Class: ActiveRecord::Base

Inherits:
Object
  • Object
show all
Defined in:
lib/active_record/base.rb,
lib/active_record/connection_adapters/mysql_adapter.rb,
lib/active_record/connection_adapters/sqlite_adapter.rb,
lib/active_record/connection_adapters/sqlite3_adapter.rb,
lib/active_record/connection_adapters/postgresql_adapter.rb,
lib/active_record/connection_adapters/abstract/connection_specification.rb

Overview

Active Record objects don’t specify their attributes directly, but rather infer them from the table definition with which they’re linked. Adding, removing, and changing attributes and their type is done directly in the database. Any change is instantly reflected in the Active Record objects. The mapping that binds a given Active Record class to a certain database table will happen automatically in most common cases, but can be overwritten for the uncommon ones.

See the mapping rules in table_name and the full example in files/README.html for more insight.

Creation

Active Records accept constructor parameters either in a hash or as a block. The hash method is especially useful when you’re receiving the data from somewhere else, like an HTTP request. It works like this:

user = User.new(:name => "David", :occupation => "Code Artist")
user.name # => "David"

You can also use block initialization:

user = User.new do |u|
  u.name = "David"
  u.occupation = "Code Artist"
end

And of course you can just create a bare object and specify the attributes after the fact:

user = User.new
user.name = "David"
user.occupation = "Code Artist"

Conditions

Conditions can either be specified as a string, array, or hash representing the WHERE-part of an SQL statement. The array form is to be used when the condition input is tainted and requires sanitization. The string form can be used for statements that don’t involve tainted data. The hash form works much like the array form, except only equality and range is possible. Examples:

class User < ActiveRecord::Base
  def self.authenticate_unsafely(user_name, password)
    find(:first, :conditions => "user_name = '#{user_name}' AND password = '#{password}'")
  end

  def self.authenticate_safely(user_name, password)
    find(:first, :conditions => [ "user_name = ? AND password = ?", user_name, password ])
  end

  def self.authenticate_safely_simply(user_name, password)
    find(:first, :conditions => { :user_name => user_name, :password => password })
  end
end

The authenticate_unsafely method inserts the parameters directly into the query and is thus susceptible to SQL-injection attacks if the user_name and password parameters come directly from an HTTP request. The authenticate_safely and authenticate_safely_simply both will sanitize the user_name and password before inserting them in the query, which will ensure that an attacker can’t escape the query and fake the login (or worse).

When using multiple parameters in the conditions, it can easily become hard to read exactly what the fourth or fifth question mark is supposed to represent. In those cases, you can resort to named bind variables instead. That’s done by replacing the question marks with symbols and supplying a hash with values for the matching symbol keys:

Company.find(:first, :conditions => [
  "id = :id AND name = :name AND division = :division AND created_at > :accounting_date",
  { :id => 3, :name => "37signals", :division => "First", :accounting_date => '2005-01-01' }
])

Similarly, a simple hash without a statement will generate conditions based on equality with the SQL AND operator. For instance:

Student.find(:all, :conditions => { :first_name => "Harvey", :status => 1 })
Student.find(:all, :conditions => params[:student])

A range may be used in the hash to use the SQL BETWEEN operator:

Student.find(:all, :conditions => { :grade => 9..12 })

Overwriting default accessors

All column values are automatically available through basic accessors on the Active Record object, but sometimes you want to specialize this behavior. This can be done by overwriting the default accessors (using the same name as the attribute) and calling read_attribute(attr_name) and write_attribute(attr_name, value) to actually change things. Example:

class Song < ActiveRecord::Base
  # Uses an integer of seconds to hold the length of the song

  def length=(minutes)
    write_attribute(:length, minutes * 60)
  end

  def length
    read_attribute(:length) / 60
  end
end

You can alternatively use self=(value) and self instead of write_attribute(:attribute, value) and read_attribute(:attribute) as a shorter form.

Attribute query methods

In addition to the basic accessors, query methods are also automatically available on the Active Record object. Query methods allow you to test whether an attribute value is present.

For example, an Active Record User with the name attribute has a name? method that you can call to determine whether the user has a name:

user = User.new(:name => "David")
user.name? # => true

anonymous = User.new(:name => "")
anonymous.name? # => false

Accessing attributes before they have been typecasted

Sometimes you want to be able to read the raw attribute data without having the column-determined typecast run its course first. That can be done by using the <attribute>_before_type_cast accessors that all attributes have. For example, if your Account model has a balance attribute, you can call account.balance_before_type_cast or account.id_before_type_cast.

This is especially useful in validation situations where the user might supply a string for an integer field and you want to display the original string back in an error message. Accessing the attribute normally would typecast the string to 0, which isn’t what you want.

Dynamic attribute-based finders

Dynamic attribute-based finders are a cleaner way of getting (and/or creating) objects by simple queries without turning to SQL. They work by appending the name of an attribute to find_by_ or find_all_by_, so you get finders like Person.find_by_user_name, Person.find_all_by_last_name, Payment.find_by_transaction_id. So instead of writing Person.find(:first, :conditions => ["user_name = ?", user_name]), you just do Person.find_by_user_name(user_name). And instead of writing Person.find(:all, :conditions => ["last_name = ?", last_name]), you just do Person.find_all_by_last_name(last_name).

It’s also possible to use multiple attributes in the same find by separating them with “and”, so you get finders like Person.find_by_user_name_and_password or even Payment.find_by_purchaser_and_state_and_country. So instead of writing Person.find(:first, :conditions => ["user_name = ? AND password = ?", user_name, password]), you just do Person.find_by_user_name_and_password(user_name, password).

It’s even possible to use all the additional parameters to find. For example, the full interface for Payment.find_all_by_amount is actually Payment.find_all_by_amount(amount, options). And the full interface to Person.find_by_user_name is actually Person.find_by_user_name(user_name, options). So you could call Payment.find_all_by_amount(50, :order => "created_on").

The same dynamic finder style can be used to create the object if it doesn’t already exist. This dynamic finder is called with find_or_create_by_ and will return the object if it already exists and otherwise creates it, then returns it. Example:

# No 'Summer' tag exists
Tag.find_or_create_by_name("Summer") # equal to Tag.create(:name => "Summer")

# Now the 'Summer' tag does exist
Tag.find_or_create_by_name("Summer") # equal to Tag.find_by_name("Summer")

Use the find_or_initialize_by_ finder if you want to return a new record without saving it first. Example:

# No 'Winter' tag exists
winter = Tag.find_or_initialize_by_name("Winter")
winter.new_record? # true

To find by a subset of the attributes to be used for instantiating a new object, pass a hash instead of a list of parameters. For example:

Tag.find_or_create_by_name(:name => "rails", :creator => current_user)

That will either find an existing tag named “rails”, or create a new one while setting the user that created it.

Saving arrays, hashes, and other non-mappable objects in text columns

Active Record can serialize any object in text columns using YAML. To do so, you must specify this with a call to the class method serialize. This makes it possible to store arrays, hashes, and other non-mappable objects without doing any additional work. Example:

class User < ActiveRecord::Base
  serialize :preferences
end

user = User.create(:preferences => { "background" => "black", "display" => large })
User.find(user.id).preferences # => { "background" => "black", "display" => large }

You can also specify a class option as the second parameter that’ll raise an exception if a serialized object is retrieved as a descendent of a class not in the hierarchy. Example:

class User < ActiveRecord::Base
  serialize :preferences, Hash
end

user = User.create(:preferences => %w( one two three ))
User.find(user.id).preferences    # raises SerializationTypeMismatch

Single table inheritance

Active Record allows inheritance by storing the name of the class in a column that by default is named “type” (can be changed by overwriting Base.inheritance_column). This means that an inheritance looking like this:

class Company < ActiveRecord::Base; end
class Firm < Company; end
class Client < Company; end
class PriorityClient < Client; end

When you do Firm.create(:name => “37signals”), this record will be saved in the companies table with type = “Firm”. You can then fetch this row again using Company.find(:first, “name = ‘37signals’”) and it will return a Firm object.

If you don’t have a type column defined in your table, single-table inheritance won’t be triggered. In that case, it’ll work just like normal subclasses with no special magic for differentiating between them or reloading the right type with find.

Note, all the attributes for all the cases are kept in the same table. Read more: www.martinfowler.com/eaaCatalog/singleTableInheritance.html

Connection to multiple databases in different models

Connections are usually created through ActiveRecord::Base.establish_connection and retrieved by ActiveRecord::Base.connection. All classes inheriting from ActiveRecord::Base will use this connection. But you can also set a class-specific connection. For example, if Course is an ActiveRecord::Base, but resides in a different database, you can just say Course.establish_connection and Course *and all its subclasses* will use this connection instead.

This feature is implemented by keeping a connection pool in ActiveRecord::Base that is a Hash indexed by the class. If a connection is requested, the retrieve_connection method will go up the class-hierarchy until a connection is found in the connection pool.

Exceptions

  • ActiveRecordError – generic error class and superclass of all other errors raised by Active Record

  • AdapterNotSpecified – the configuration hash used in establish_connection didn’t include an :adapter key.

  • AdapterNotFound – the :adapter key used in establish_connection specified a non-existent adapter (or a bad spelling of an existing one).

  • AssociationTypeMismatch – the object assigned to the association wasn’t of the type specified in the association definition.

  • SerializationTypeMismatch – the serialized object wasn’t of the class specified as the second parameter.

  • ConnectionNotEstablished – no connection has been established. Use establish_connection before querying.

  • RecordNotFound – no record responded to the find* method. Either the row with the given ID doesn’t exist or the row didn’t meet the additional restrictions.

  • StatementInvalid – the database server rejected the SQL statement. The precise error is added in the message. Either the record with the given ID doesn’t exist or the record didn’t meet the additional restrictions.

  • MultiparameterAssignmentErrors – collection of errors that occurred during a mass assignment using the attributes= method. The errors property of this exception contains an array of AttributeAssignmentError objects that should be inspected to determine which attributes triggered the errors.

  • AttributeAssignmentError – an error occurred while doing a mass assignment through the attributes= method. You can inspect the attribute property of the exception object to determine which attribute triggered the error.

Note: The attributes listed are class-level attributes (accessible from both the class and instance level). So it’s possible to assign a logger to the class through Base.logger= which will then be used by all instances in the current object space.

Defined Under Namespace

Classes: ConnectionSpecification

Constant Summary collapse

@@subclasses = 
{}
@@configurations = 
{}
@@primary_key_prefix_type = 
nil
@@table_name_prefix = 
""
@@table_name_suffix = 
""
@@pluralize_table_names = 
true
@@colorize_logging = 
true
@@default_timezone = 
:local
@@allow_concurrency = 
false
@@schema_format = 
:ruby
@@verification_timeout = 
0
@@defined_connections =

The class -> [adapter_method, config] map

{}
@@active_connections =

The class -> thread id -> adapter cache. (class -> adapter if not allow_concurrency)

{}

Class Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(attributes = nil) ⇒ Base

New objects can be instantiated as either empty (pass no construction parameter) or pre-set with attributes but not yet saved (pass a hash with key names matching the associated table column names). In both instances, valid attribute keys are determined by the column names of the associated table – hence you can’t have attributes that aren’t part of the table columns.



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# File 'lib/active_record/base.rb', line 1848

def initialize(attributes = nil)
  @attributes = attributes_from_column_definition
  @attributes_cache = {}
  @new_record = true
  ensure_proper_type
  self.attributes = attributes unless attributes.nil?
  self.class.send(:scope, :create).each { |att,value| self.send("#{att}=", value) } if self.class.send(:scoped?, :create)
  result = yield self if block_given?
  callback(:after_initialize) if respond_to_without_attributes?(:after_initialize)
  result
end

Class Attribute Details

.abstract_class ⇒ Object

Set this to true if this is an abstract class (see #abstract_class?).



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# File 'lib/active_record/base.rb', line 1143

def abstract_class
  @abstract_class
end

Class Method Details

.===(object) ⇒ Object

Overwrite the default class equality method to provide support for association proxies.



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# File 'lib/active_record/base.rb', line 1131

def ===(object)
  object.is_a?(self)
end

.abstract_class? ⇒ Boolean

Returns whether this class is a base AR class. If A is a base class and B descends from A, then B.base_class will return B.

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 1147

def abstract_class?
  abstract_class == true
end

.accessible_attributes ⇒ Object

Returns an array of all the attributes that have been made accessible to mass-assignment.



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# File 'lib/active_record/base.rb', line 785

def accessible_attributes # :nodoc:
  read_inheritable_attribute("attr_accessible")
end

.active_connection_name ⇒ Object

:nodoc:



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 54

def active_connection_name #:nodoc:
  @active_connection_name ||=
     if active_connections[name] || @@defined_connections[name]
       name
     elsif self == ActiveRecord::Base
       nil
     else
       superclass.active_connection_name
     end
end

.allow_concurrency=(threaded) ⇒ Object

set concurrency support flag (not thread safe, like most of the methods in this file)



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 41

def allow_concurrency=(threaded) #:nodoc:
  logger.debug "allow_concurrency=#{threaded}" if logger
  return if @@allow_concurrency == threaded
  clear_all_cached_connections!
  @@allow_concurrency = threaded
  method_prefix = threaded ? "thread_safe" : "single_threaded"
  sing = (class << self; self; end)
  [:active_connections, :scoped_methods].each do |method|
    sing.send(:alias_method, method, "#{method_prefix}_#{method}")
  end
  log_connections if logger
end

.attr_accessible(*attributes) ⇒ Object

Similar to the attr_protected macro, this protects attributes of your model from mass-assignment, such as new(attributes) and attributes=(attributes) however, it does it in the opposite way. This locks all attributes and only allows access to the attributes specified. Assignment to attributes not in this list will be ignored and need to be set using the direct writer methods instead. This is meant to protect sensitive attributes from being overwritten by URL/form hackers. If you’d rather start from an all-open default and restrict attributes as needed, have a look at attr_protected.

Options

*attributes A comma separated list of symbols that represent columns not to be protected

Examples

class Customer < ActiveRecord::Base
  attr_accessible :name, :nickname
end

customer = Customer.new(:name => "David", :nickname => "Dave", :credit_rating => "Excellent")
customer.credit_rating # => nil
customer.attributes = { :name => "Jolly fellow", :credit_rating => "Superb" }
customer.credit_rating # => nil

customer.credit_rating = "Average"
customer.credit_rating # => "Average"



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# File 'lib/active_record/base.rb', line 780

def attr_accessible(*attributes)
  write_inheritable_attribute("attr_accessible", Set.new(attributes.map(&:to_s)) + (accessible_attributes || []))
end

.attr_protected(*attributes) ⇒ Object

Attributes named in this macro are protected from mass-assignment, such as new(attributes) and attributes=(attributes). Their assignment will simply be ignored. Instead, you can use the direct writer methods to do assignment. This is meant to protect sensitive attributes from being overwritten by URL/form hackers. Example:

class Customer < ActiveRecord::Base
  attr_protected :credit_rating
end

customer = Customer.new("name" => David, "credit_rating" => "Excellent")
customer.credit_rating # => nil
customer.attributes = { "description" => "Jolly fellow", "credit_rating" => "Superb" }
customer.credit_rating # => nil

customer.credit_rating = "Average"
customer.credit_rating # => "Average"

To start from an all-closed default and enable attributes as needed, have a look at attr_accessible.



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# File 'lib/active_record/base.rb', line 746

def attr_protected(*attributes)
  write_inheritable_attribute("attr_protected", Set.new(attributes.map(&:to_s)) + (protected_attributes || []))
end

.attr_readonly(*attributes) ⇒ Object

Attributes listed as readonly can be set for a new record, but will be ignored in database updates afterwards.



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# File 'lib/active_record/base.rb', line 790

def attr_readonly(*attributes)
  write_inheritable_attribute("attr_readonly", Set.new(attributes.map(&:to_s)) + (readonly_attributes || []))
end

.base_class ⇒ Object

Returns the base AR subclass that this class descends from. If A extends AR::Base, A.base_class will return A. If B descends from A through some arbitrarily deep hierarchy, B.base_class will return A.



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# File 'lib/active_record/base.rb', line 1138

def base_class
  class_of_active_record_descendant(self)
end

.benchmark(title, log_level = Logger::DEBUG, use_silence = true) ⇒ Object

Log and benchmark multiple statements in a single block. Example:

Project.benchmark("Creating project") do
  project = Project.create("name" => "stuff")
  project.create_manager("name" => "David")
  project.milestones << Milestone.find(:all)
end

The benchmark is only recorded if the current level of the logger matches the log_level, which makes it easy to include benchmarking statements in production software that will remain inexpensive because the benchmark will only be conducted if the log level is low enough.

The logging of the multiple statements is turned off unless use_silence is set to false.



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# File 'lib/active_record/base.rb', line 1111

def benchmark(title, log_level = Logger::DEBUG, use_silence = true)
  if logger && logger.level == log_level
    result = nil
    seconds = Benchmark.realtime { result = use_silence ? silence { yield } : yield }
    logger.add(log_level, "#{title} (#{'%.5f' % seconds})")
    result
  else
    yield
  end
end

.class_name(table_name = table_name) ⇒ Object

Turns the table_name back into a class name following the reverse rules of table_name.



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# File 'lib/active_record/base.rb', line 981

def class_name(table_name = table_name) # :nodoc:
  # remove any prefix and/or suffix from the table name
  class_name = table_name[table_name_prefix.length..-(table_name_suffix.length + 1)].camelize
  class_name = class_name.singularize if pluralize_table_names
  class_name
end

.clear_active_connection_name ⇒ Object

:nodoc:



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 65

def clear_active_connection_name #:nodoc:
  @active_connection_name = nil
  subclasses.each { |klass| klass.clear_active_connection_name }
end

.clear_active_connections! ⇒ Object

Clears the cache which maps classes to connections.



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 84

def clear_active_connections!
  clear_cache!(@@active_connections) do |name, conn|
    conn.disconnect!
  end
end

.clear_reloadable_connections! ⇒ Object

Clears the cache which maps classes



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 91

def clear_reloadable_connections!
  if @@allow_concurrency
    # With concurrent connections @@active_connections is
    # a hash keyed by thread id.
    @@active_connections.each do |thread_id, conns|
      conns.each do |name, conn|
        if conn.requires_reloading?
          conn.disconnect!
          @@active_connections[thread_id].delete(name)
        end
      end
    end
  else
    @@active_connections.each do |name, conn|
      if conn.requires_reloading?
        conn.disconnect!
        @@active_connections.delete(name)
      end
    end
  end
end

.column_methods_hash ⇒ Object

Returns a hash of all the methods added to query each of the columns in the table with the name of the method as the key and true as the value. This makes it possible to do O(1) lookups in respond_to? to check if a given method for attribute is available.



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# File 'lib/active_record/base.rb', line 1032

def column_methods_hash #:nodoc:
  @dynamic_methods_hash ||= column_names.inject(Hash.new(false)) do |methods, attr|
    attr_name = attr.to_s
    methods[attr.to_sym]       = attr_name
    methods["#{attr}=".to_sym] = attr_name
    methods["#{attr}?".to_sym] = attr_name
    methods["#{attr}_before_type_cast".to_sym] = attr_name
    methods
  end
end

.column_names ⇒ Object

Returns an array of column names as strings.



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# File 'lib/active_record/base.rb', line 1019

def column_names
  @column_names ||= columns.map { |column| column.name }
end

.columns ⇒ Object

Returns an array of column objects for the table associated with this class.



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# File 'lib/active_record/base.rb', line 1005

def columns
  unless @columns
    @columns = connection.columns(table_name, "#{name} Columns")
    @columns.each {|column| column.primary = column.name == primary_key}
  end
  @columns
end

.columns_hash ⇒ Object

Returns a hash of column objects for the table associated with this class.



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# File 'lib/active_record/base.rb', line 1014

def columns_hash
  @columns_hash ||= columns.inject({}) { |hash, column| hash[column.name] = column; hash }
end

.connected? ⇒ Boolean

Returns true if a connection that’s accessible to this class has already been opened.

Returns:

  • (Boolean) 


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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 268

def self.connected?
  active_connections[active_connection_name] ? true : false
end

.connection ⇒ Object

Returns the connection currently associated with the class. This can also be used to “borrow” the connection to do database work unrelated to any of the specific Active Records.



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 73

def connection
  if @active_connection_name && (conn = active_connections[@active_connection_name])
    conn
  else
    # retrieve_connection sets the cache key.
    conn = retrieve_connection
    active_connections[@active_connection_name] = conn
  end
end

.connection=(spec) ⇒ Object

Set the connection for the class.



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 286

def self.connection=(spec) #:nodoc:
  if spec.kind_of?(ActiveRecord::ConnectionAdapters::AbstractAdapter)
    active_connections[name] = spec
  elsif spec.kind_of?(ConnectionSpecification)
    config = spec.config.reverse_merge(:allow_concurrency => @@allow_concurrency)
    self.connection = self.send(spec.adapter_method, config)
  elsif spec.nil?
    raise ConnectionNotEstablished
  else
    establish_connection spec
  end
end

.content_columns ⇒ Object

Returns an array of column objects where the primary id, all columns ending in “_id” or “_count”, and columns used for single table inheritance have been removed.



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# File 'lib/active_record/base.rb', line 1025

def content_columns
  @content_columns ||= columns.reject { |c| c.primary || c.name =~ /(_id|_count)$/ || c.name == inheritance_column }
end

.count_by_sql(sql) ⇒ Object

Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part. The use of this method should be restricted to complicated SQL queries that can’t be executed using the ActiveRecord::Calculations class methods. Look into those before using this.

Options

sql: An SQL statement which should return a count query from the database, see the example below

Examples

Product.count_by_sql "SELECT COUNT(*) FROM sales s, customers c WHERE s.customer_id = c.id"



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# File 'lib/active_record/base.rb', line 656

def count_by_sql(sql)
  sql = sanitize_conditions(sql)
  connection.select_value(sql, "#{name} Count").to_i
end

.create(attributes = nil) ⇒ Object

Creates an object (or multiple objects) and saves it to the database, if validations pass.

The resulting object is returned whether the object was saved successfully to the database or not.

The attributes parameter can be either be a Hash or an Array of Hashes. These Hashes describe the attributes on the objects that are to be created.

Examples

# Create a single new object
User.create(:first_name => 'Jamie')
# Create an Array of new objects
User.create([{:first_name => 'Jamie'}, {:first_name => 'Jeremy'}])



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# File 'lib/active_record/base.rb', line 517

def create(attributes = nil)
  if attributes.is_a?(Array)
    attributes.collect { |attr| create(attr) }
  else
    object = new(attributes)
    object.save
    object
  end
end

.decrement_counter(counter_name, id) ⇒ Object

Decrement a number field by one, usually representing a count.

This works the same as increment_counter but reduces the column value by 1 instead of increasing it.

Options

counter_name The name of the field that should be decremented id The id of the object that should be decremented

Examples

# Decrement the post_count column for the record with an id of 5
DiscussionBoard.decrement_counter(:post_count, 5)



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# File 'lib/active_record/base.rb', line 724

def decrement_counter(counter_name, id)
  update_counters(id, counter_name => -1)
end

.delete(id) ⇒ Object

Delete an object (or multiple objects) where the id given matches the primary_key. A SQL DELETE command is executed on the database which means that no callbacks are fired off running this. This is an efficient method of deleting records that don’t need cleaning up after or other actions to be taken.

Objects are not instantiated with this method.

Options

id Can be either an Integer or an Array of Integers

Examples

# Delete a single object
Todo.delete(1)

# Delete multiple objects
todos = [1,2,3]
Todo.delete(todos)



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# File 'lib/active_record/base.rb', line 572

def delete(id)
  delete_all([ "#{connection.quote_column_name(primary_key)} IN (?)", id ])
end

.delete_all(conditions = nil) ⇒ Object

Deletes all the records that match the conditions without instantiating the objects first (and hence not calling the destroy method). Example:

Post.delete_all "person_id = 5 AND (category = 'Something' OR category = 'Else')"



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# File 'lib/active_record/base.rb', line 639

def delete_all(conditions = nil)
  sql = "DELETE FROM #{quoted_table_name} "
  add_conditions!(sql, conditions, scope(:find))
  connection.delete(sql, "#{name} Delete all")
end

.descends_from_active_record? ⇒ Boolean

True if this isn’t a concrete subclass needing a STI type condition.

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 1061

def descends_from_active_record?
  if superclass.abstract_class?
    superclass.descends_from_active_record?
  else
    superclass == Base || !columns_hash.include?(inheritance_column)
  end
end

.destroy(id) ⇒ Object

Destroy an object (or multiple objects) that has the given id, the object is instantiated first, therefore all callbacks and filters are fired off before the object is deleted. This method is less efficient than ActiveRecord#delete but allows cleanup methods and other actions to be run.

This essentially finds the object (or multiple objects) with the given id, creates a new object from the attributes, and then calls destroy on it.

Options

id Can be either an Integer or an Array of Integers

Examples

# Destroy a single object
Todo.destroy(1)

# Destroy multiple objects
todos = [1,2,3]
Todo.destroy(todos)



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# File 'lib/active_record/base.rb', line 595

def destroy(id)
  id.is_a?(Array) ? id.each { |id| destroy(id) } : find(id).destroy
end

.destroy_all(conditions = nil) ⇒ Object

Destroys the objects for all the records that match the conditions by instantiating each object and calling the destroy method. Example:

Person.destroy_all "last_login < '2004-04-04'"



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# File 'lib/active_record/base.rb', line 632

def destroy_all(conditions = nil)
  find(:all, :conditions => conditions).each { |object| object.destroy }
end

.establish_connection(spec = nil) ⇒ Object

Establishes the connection to the database. Accepts a hash as input where the :adapter key must be specified with the name of a database adapter (in lower-case) example for regular databases (MySQL, Postgresql, etc):

ActiveRecord::Base.establish_connection(
  :adapter  => "mysql",
  :host     => "localhost",
  :username => "myuser",
  :password => "mypass",
  :database => "somedatabase"
)

Example for SQLite database:

ActiveRecord::Base.establish_connection(
  :adapter => "sqlite",
  :database  => "path/to/dbfile"
)

Also accepts keys as strings (for parsing from yaml for example):

ActiveRecord::Base.establish_connection(
  "adapter" => "sqlite",
  "database"  => "path/to/dbfile"
)

The exceptions AdapterNotSpecified, AdapterNotFound and ArgumentError may be returned on an error.



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 204

def self.establish_connection(spec = nil)
  case spec
    when nil
      raise AdapterNotSpecified unless defined? RAILS_ENV
      establish_connection(RAILS_ENV)
    when ConnectionSpecification
      clear_active_connection_name
      @active_connection_name = name
      @@defined_connections[name] = spec
    when Symbol, String
      if configuration = configurations[spec.to_s]
        establish_connection(configuration)
      else
        raise AdapterNotSpecified, "#{spec} database is not configured"
      end
    else
      spec = spec.symbolize_keys
      unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end

      begin
        require 'rubygems'
        gem "activerecord-#{spec[:adapter]}-adapter"
        require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
      rescue LoadError
        begin
          require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
        rescue LoadError
          raise "Please install the #{spec[:adapter]} adapter: `gem install activerecord-#{spec[:adapter]}-adapter` (#{$!})"
        end
      end

      adapter_method = "#{spec[:adapter]}_connection"
      if !respond_to?(adapter_method)
        raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter"
      end

      remove_connection
      establish_connection(ConnectionSpecification.new(spec, adapter_method))
  end
end

.exists?(id_or_conditions) ⇒ Boolean

Checks whether a record exists in the database that matches conditions given. These conditions can either be a single integer representing a primary key id to be found, or a condition to be matched like using ActiveRecord#find.

The id_or_conditions parameter can be an Integer or a String if you want to search the primary key column of the table for a matching id, or if you’re looking to match against a condition you can use an Array or a Hash.

Possible gotcha: You can’t pass in a condition as a string e.g. “name = ‘Jamie’”, this would be sanitized and then queried against the primary key column as “id = ‘name = 'Jamie”

Examples

Person.exists?(5)
Person.exists?('5')
Person.exists?(:name => "David")
Person.exists?(['name LIKE ?', "%#{query}%"])

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 500

def exists?(id_or_conditions)
  !find(:first, :select => "#{table_name}.#{primary_key}", :conditions => expand_id_conditions(id_or_conditions)).nil?
rescue ActiveRecord::ActiveRecordError
  false
end

.find(*args) ⇒ Object

Find operates with three different retrieval approaches:

  • Find by id: This can either be a specific id (1), a list of ids (1, 5, 6), or an array of ids ([5, 6, 10]). If no record can be found for all of the listed ids, then RecordNotFound will be raised.

  • Find first: This will return the first record matched by the options used. These options can either be specific conditions or merely an order. If no record can be matched, nil is returned.

  • Find all: This will return all the records matched by the options used. If no records are found, an empty array is returned.

All approaches accept an options hash as their last parameter. The options are:

  • :conditions: An SQL fragment like “administrator = 1” or [ “user_name = ?”, username ]. See conditions in the intro.

  • :order: An SQL fragment like “created_at DESC, name”.

  • :group: An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.

  • :limit: An integer determining the limit on the number of rows that should be returned.

  • :offset: An integer determining the offset from where the rows should be fetched. So at 5, it would skip rows 0 through 4.

  • :joins: An SQL fragment for additional joins like “LEFT JOIN comments ON comments.post_id = id” (Rarely needed). Accepts named associations in the form of :include, which will perform an INNER JOIN on the associated table(s). The records will be returned read-only since they will have attributes that do not correspond to the table’s columns. Pass :readonly => false to override. See adding joins for associations under Associations.

  • :include: Names associations that should be loaded alongside using LEFT OUTER JOINs. The symbols named refer to already defined associations. See eager loading under Associations.

  • :select: By default, this is * as in SELECT * FROM, but can be changed if you, for example, want to do a join but not include the joined columns.

  • :from: By default, this is the table name of the class, but can be changed to an alternate table name (or even the name of a database view).

  • :readonly: Mark the returned records read-only so they cannot be saved or updated.

  • :lock: An SQL fragment like “FOR UPDATE” or “LOCK IN SHARE MODE”. :lock => true gives connection’s default exclusive lock, usually “FOR UPDATE”.

Examples for find by id:

Person.find(1)       # returns the object for ID = 1
Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6)
Person.find([7, 17]) # returns an array for objects with IDs in (7, 17)
Person.find([1])     # returns an array for the object with ID = 1
Person.find(1, :conditions => "administrator = 1", :order => "created_on DESC")

Note that returned records may not be in the same order as the ids you provide since database rows are unordered. Give an explicit :order to ensure the results are sorted.

Examples for find first:

Person.find(:first) # returns the first object fetched by SELECT * FROM people
Person.find(:first, :conditions => [ "user_name = ?", user_name])
Person.find(:first, :order => "created_on DESC", :offset => 5)

Examples for find all:

Person.find(:all) # returns an array of objects for all the rows fetched by SELECT * FROM people
Person.find(:all, :conditions => [ "category IN (?)", categories], :limit => 50)
Person.find(:all, :offset => 10, :limit => 10)
Person.find(:all, :include => [ :account, :friends ])
Person.find(:all, :group => "category")

Example for find with a lock. Imagine two concurrent transactions: each will read person.visits == 2, add 1 to it, and save, resulting in two saves of person.visits = 3. By locking the row, the second transaction has to wait until the first is finished; we get the expected person.visits == 4.

Person.transaction do
  person = Person.find(1, :lock => true)
  person.visits += 1
  person.save!
end



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# File 'lib/active_record/base.rb', line 438

def find(*args)
  options = args.extract_options!
  # Note:  we extract any :joins option with a non-string value from the options, and turn it into
  #  an internal option :ar_joins.  This allows code called from here to find the ar_joins, and
  #  it bypasses marking the result as read_only.
  #  A normal string join marks the result as read-only because it contains attributes from joined tables
  #  which are not in the base table and therefore prevent the result from being saved.
  #  In the case of an ar_join, the JoinDependency created to instantiate the results eliminates these
  #  bogus attributes.  See JoinDependency#instantiate, and JoinBase#instantiate in associations.rb.
  validate_find_options(options)
  set_readonly_option!(options)

  case args.first
    when :first then find_initial(options)
    when :all   then find_every(options)
    else             find_from_ids(args, options)
  end
end

.find_by_sql(sql) ⇒ Object

Executes a custom sql query against your database and returns all the results. The results will be returned as an array with columns requested encapsulated as attributes of the model you call this method from. If you call Product.find_by_sql then the results will be returned in a Product object with the attributes you specified in the SQL query.

If you call a complicated SQL query which spans multiple tables the columns specified by the SELECT will be attributes of the model, whether or not they are columns of the corresponding table.

The sql parameter is a full sql query as a string. It will be called as is, there will be no database agnostic conversions performed. This should be a last resort because using, for example,

MySQL specific terms will lock you to using that particular database engine or require you to change your call if you switch engines

Examples

# A simple sql query spanning multiple tables
Post.find_by_sql "SELECT p.title, c.author FROM posts p, comments c WHERE p.id = c.post_id"
> [#<Post:0x36bff9c @attributes={"title"=>"Ruby Meetup", "first_name"=>"Quentin"}>, ...]

# You can use the same string replacement techniques as you can with ActiveRecord#find
Post.find_by_sql ["SELECT title FROM posts WHERE author = ? AND created > ?", author_id, start_date]
> [#<Post:0x36bff9c @attributes={"first_name"=>"The Cheap Man Buys Twice"}>, ...]



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# File 'lib/active_record/base.rb', line 480

def find_by_sql(sql)
  connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
end

.finder_needs_type_condition? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 1069

def finder_needs_type_condition? #:nodoc:
  # This is like this because benchmarking justifies the strange :false stuff
  :true == (@finder_needs_type_condition ||= descends_from_active_record? ? :false : :true)
end

.human_attribute_name(attribute_key_name) ⇒ Object

Transforms attribute key names into a more humane format, such as “First name” instead of “first_name”. Example:

Person.human_attribute_name("first_name") # => "First name"

Deprecated in favor of just calling “first_name”.humanize



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# File 'lib/active_record/base.rb', line 1056

def human_attribute_name(attribute_key_name) #:nodoc:
  attribute_key_name.humanize
end

.increment_counter(counter_name, id) ⇒ Object

Increment a number field by one, usually representing a count.

This is used for caching aggregate values, so that they don’t need to be computed every time. For example, a DiscussionBoard may cache post_count and comment_count otherwise every time the board is shown it would have to run an SQL query to find how many posts and comments there are.

Options

counter_name The name of the field that should be incremented id The id of the object that should be incremented

Examples

# Increment the post_count column for the record with an id of 5
DiscussionBoard.increment_counter(:post_count, 5)



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# File 'lib/active_record/base.rb', line 707

def increment_counter(counter_name, id)
  update_counters(id, counter_name => 1)
end

.inheritance_column ⇒ Object

Defines the column name for use with single table inheritance – can be set in subclasses like so: self.inheritance_column = “type_id”



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# File 'lib/active_record/base.rb', line 900

def inheritance_column
  @inheritance_column ||= "type".freeze
end

.inherited(child) ⇒ Object

:nodoc:



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# File 'lib/active_record/base.rb', line 300

def self.inherited(child) #:nodoc:
  @@subclasses[self] ||= []
  @@subclasses[self] << child
  super
end

.inspect ⇒ Object

Returns a string like ‘Post id:integer, title:string, body:text’



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# File 'lib/active_record/base.rb', line 1075

def inspect
  if self == Base
    super
  elsif abstract_class?
    "#{super}(abstract)"
  elsif table_exists?
    attr_list = columns.map { |c| "#{c.name}: #{c.type}" } * ', '
    "#{super}(#{attr_list})"
  else
    "#{super}(Table doesn't exist)"
  end
end

.log_connections ⇒ Object

connection state logging



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 300

def self.log_connections #:nodoc:
  if logger
    logger.info "Defined connections: #{@@defined_connections.inspect}"
    logger.info "Active connections: #{active_connections.inspect}"
    logger.info "Active connection name: #{@active_connection_name}"
  end
end

.mysql_connection(config) ⇒ Object

Establishes a connection to the database that’s used by all Active Record objects.



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# File 'lib/active_record/connection_adapters/mysql_adapter.rb', line 70

def self.mysql_connection(config) # :nodoc:
  config = config.symbolize_keys
  host     = config[:host]
  port     = config[:port]
  socket   = config[:socket]
  username = config[:username] ? config[:username].to_s : 'root'
  password = config[:password].to_s

  if config.has_key?(:database)
    database = config[:database]
  else
    raise ArgumentError, "No database specified. Missing argument: database."
  end

  require_mysql
  mysql = Mysql.init
  mysql.ssl_set(config[:sslkey], config[:sslcert], config[:sslca], config[:sslcapath], config[:sslcipher]) if config[:sslkey]

  ConnectionAdapters::MysqlAdapter.new(mysql, logger, [host, username, password, database, port, socket], config)
end

.postgresql_connection(config) ⇒ Object

Establishes a connection to the database that’s used by all Active Record objects



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# File 'lib/active_record/connection_adapters/postgresql_adapter.rb', line 6

def self.postgresql_connection(config) # :nodoc:
  require_library_or_gem 'postgres' unless self.class.const_defined?(:PGconn)

  config = config.symbolize_keys
  host     = config[:host]
  port     = config[:port] || 5432
  username = config[:username].to_s
  password = config[:password].to_s

  if config.has_key?(:database)
    database = config[:database]
  else
    raise ArgumentError, "No database specified. Missing argument: database."
  end

  # The postgres drivers don't allow the creation of an unconnected PGconn object,
  # so just pass a nil connection object for the time being.
  ConnectionAdapters::PostgreSQLAdapter.new(nil, logger, [host, port, nil, nil, database, username, password], config)
end

.primary_key ⇒ Object

Defines the primary key field – can be overridden in subclasses. Overwriting will negate any effect of the primary_key_prefix_type setting, though.



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# File 'lib/active_record/base.rb', line 882

def primary_key
  reset_primary_key
end

.protected_attributes ⇒ Object

Returns an array of all the attributes that have been protected from mass-assignment.



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# File 'lib/active_record/base.rb', line 751

def protected_attributes # :nodoc:
  read_inheritable_attribute("attr_protected")
end

.quote_value(value, column = nil) ⇒ Object

:nodoc:



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# File 'lib/active_record/base.rb', line 1089

def quote_value(value, column = nil) #:nodoc:
  connection.quote(value,column)
end

.readonly_attributes ⇒ Object

Returns an array of all the attributes that have been specified as readonly.



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# File 'lib/active_record/base.rb', line 795

def readonly_attributes
  read_inheritable_attribute("attr_readonly")
end

.remove_connection(klass = self) ⇒ Object

Remove the connection for this class. This will close the active connection and the defined connection (if they exist). The result can be used as an argument for establish_connection, for easily re-establishing the connection.



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 276

def self.remove_connection(klass=self)
  spec = @@defined_connections[klass.name]
  konn = active_connections[klass.name]
  @@defined_connections.delete_if { |key, value| value == spec }
  active_connections.delete_if { |key, value| value == konn }
  konn.disconnect! if konn
  spec.config if spec
end

.require_mysql ⇒ Object 



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# File 'lib/active_record/connection_adapters/mysql_adapter.rb', line 45

def self.require_mysql
  # Include the MySQL driver if one hasn't already been loaded
  unless defined? Mysql
    begin
      require_library_or_gem 'mysql'
    rescue LoadError => cannot_require_mysql
      # Use the bundled Ruby/MySQL driver if no driver is already in place
      begin
        ActiveRecord::Base.logger.info(
          "WARNING: You're using the Ruby-based MySQL library that ships with Rails. This library is not suited for production. " +
          "Please install the C-based MySQL library instead (gem install mysql)."
        ) if ActiveRecord::Base.logger

        require 'active_record/vendor/mysql'
      rescue LoadError
        raise cannot_require_mysql
      end
    end
  end

  # Define Mysql::Result.all_hashes
  MysqlCompat.define_all_hashes_method!
end

.reset_column_information ⇒ Object

Resets all the cached information about columns, which will cause them to be reloaded on the next request.



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# File 'lib/active_record/base.rb', line 1044

def reset_column_information
  generated_methods.each { |name| undef_method(name) }
  @column_names = @columns = @columns_hash = @content_columns = @dynamic_methods_hash = @generated_methods = @inheritance_column = nil
end

.reset_column_information_and_inheritable_attributes_for_all_subclasses ⇒ Object

:nodoc:



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# File 'lib/active_record/base.rb', line 1049

def reset_column_information_and_inheritable_attributes_for_all_subclasses#:nodoc:
  subclasses.each { |klass| klass.reset_inheritable_attributes; klass.reset_column_information }
end

.reset_primary_key ⇒ Object

:nodoc:



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# File 'lib/active_record/base.rb', line 886

def reset_primary_key #:nodoc:
  key = 'id'
  case primary_key_prefix_type
    when :table_name
      key = Inflector.foreign_key(base_class.name, false)
    when :table_name_with_underscore
      key = Inflector.foreign_key(base_class.name)
  end
  set_primary_key(key)
  key
end

.reset_sequence_name ⇒ Object

:nodoc:



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# File 'lib/active_record/base.rb', line 910

def reset_sequence_name #:nodoc:
  default = connection.default_sequence_name(table_name, primary_key)
  set_sequence_name(default)
  default
end

.reset_subclasses ⇒ Object

:nodoc:



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# File 'lib/active_record/base.rb', line 306

def self.reset_subclasses #:nodoc:
  nonreloadables = []
  subclasses.each do |klass|
    unless Dependencies.autoloaded? klass
      nonreloadables << klass
      next
    end
    klass.instance_variables.each { |var| klass.send(:remove_instance_variable, var) }
    klass.instance_methods(false).each { |m| klass.send :undef_method, m }
  end
  @@subclasses = {}
  nonreloadables.each { |klass| (@@subclasses[klass.superclass] ||= []) << klass }
end

.reset_table_name ⇒ Object

:nodoc:



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# File 'lib/active_record/base.rb', line 859

def reset_table_name #:nodoc:
  base = base_class

  name =
    # STI subclasses always use their superclass' table.
    unless self == base
      base.table_name
    else
      # Nested classes are prefixed with singular parent table name.
      if parent < ActiveRecord::Base && !parent.abstract_class?
        contained = parent.table_name
        contained = contained.singularize if parent.pluralize_table_names
        contained << '_'
      end
      name = "#{table_name_prefix}#{contained}#{undecorated_table_name(base.name)}#{table_name_suffix}"
    end

  set_table_name(name)
  name
end

.retrieve_connection ⇒ Object

Locate the connection of the nearest super class. This can be an active or defined connection: if it is the latter, it will be opened and set as the active connection for the class it was defined for (not necessarily the current class).



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 249

def self.retrieve_connection #:nodoc:
  # Name is nil if establish_connection hasn't been called for
  # some class along the inheritance chain up to AR::Base yet.
  if name = active_connection_name
    if conn = active_connections[name]
      # Verify the connection.
      conn.verify!(@@verification_timeout)
    elsif spec = @@defined_connections[name]
      # Activate this connection specification.
      klass = name.constantize
      klass.connection = spec
      conn = active_connections[name]
    end
  end

  conn or raise ConnectionNotEstablished
end

.sanitize(object) ⇒ Object

Used to sanitize objects before they’re used in an SQL SELECT statement. Delegates to connection.quote.



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# File 'lib/active_record/base.rb', line 1094

def sanitize(object) #:nodoc:
  connection.quote(object)
end

.sequence_name ⇒ Object

Lazy-set the sequence name to the connection’s default. This method is only ever called once since set_sequence_name overrides it.



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# File 'lib/active_record/base.rb', line 906

def sequence_name #:nodoc:
  reset_sequence_name
end

.serialize(attr_name, class_name = Object) ⇒ Object

If you have an attribute that needs to be saved to the database as an object, and retrieved as the same object, then specify the name of that attribute using this method and it will be handled automatically.

The serialization is done through YAML. If class_name is specified, the serialized object must be of that class on retrieval or SerializationTypeMismatch will be raised.

Options

attr_name The field name that should be serialized class_name Optional, class name that the object type should be equal to

Example

# Serialize a preferences attribute
class User
  serialize :preferences
end



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# File 'lib/active_record/base.rb', line 814

def serialize(attr_name, class_name = Object)
  serialized_attributes[attr_name.to_s] = class_name
end

.serialized_attributes ⇒ Object

Returns a hash of all the attributes that have been specified for serialization as keys and their class restriction as values.



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# File 'lib/active_record/base.rb', line 819

def serialized_attributes
  read_inheritable_attribute("attr_serialized") or write_inheritable_attribute("attr_serialized", {})
end

.set_inheritance_column(value = nil, &block) ⇒ Object Also known as: inheritance_column=

Sets the name of the inheritance column to use to the given value, or (if the value # is nil or false) to the value returned by the given block.

Example:

class Project < ActiveRecord::Base
  set_inheritance_column do
    original_inheritance_column + "_id"
  end
end



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# File 'lib/active_record/base.rb', line 954

def set_inheritance_column(value = nil, &block)
  define_attr_method :inheritance_column, value, &block
end

.set_primary_key(value = nil, &block) ⇒ Object Also known as: primary_key=

Sets the name of the primary key column to use to the given value, or (if the value is nil or false) to the value returned by the given block.

Example:

class Project < ActiveRecord::Base
  set_primary_key "sysid"
end



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# File 'lib/active_record/base.rb', line 938

def set_primary_key(value = nil, &block)
  define_attr_method :primary_key, value, &block
end

.set_sequence_name(value = nil, &block) ⇒ Object Also known as: sequence_name=

Sets the name of the sequence to use when generating ids to the given value, or (if the value is nil or false) to the value returned by the given block. This is required for Oracle and is useful for any database which relies on sequences for primary key generation.

If a sequence name is not explicitly set when using Oracle or Firebird, it will default to the commonly used pattern of: #table_name_seq

If a sequence name is not explicitly set when using PostgreSQL, it will discover the sequence corresponding to your primary key for you.

Example:

class Project < ActiveRecord::Base
  set_sequence_name "projectseq"   # default would have been "project_seq"
end



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# File 'lib/active_record/base.rb', line 975

def set_sequence_name(value = nil, &block)
  define_attr_method :sequence_name, value, &block
end

.set_table_name(value = nil, &block) ⇒ Object Also known as: table_name=

Sets the table name to use to the given value, or (if the value is nil or false) to the value returned by the given block.

Example:

class Project < ActiveRecord::Base
  set_table_name "project"
end



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# File 'lib/active_record/base.rb', line 924

def set_table_name(value = nil, &block)
  define_attr_method :table_name, value, &block
end

.silence ⇒ Object

Silences the logger for the duration of the block.



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# File 'lib/active_record/base.rb', line 1123

def silence
  old_logger_level, logger.level = logger.level, Logger::ERROR if logger
  yield
ensure
  logger.level = old_logger_level if logger
end

.single_threaded_active_connections ⇒ Object

:nodoc:



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 29

def single_threaded_active_connections #:nodoc:
  @@active_connections
end

.sqlite3_connection(config) ⇒ Object

sqlite3 adapter reuses sqlite_connection.



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# File 'lib/active_record/connection_adapters/sqlite3_adapter.rb', line 6

def self.sqlite3_connection(config) # :nodoc:
  parse_sqlite_config!(config)

  unless self.class.const_defined?(:SQLite3)
    require_library_or_gem(config[:adapter])
  end

  db = SQLite3::Database.new(
    config[:database],
    :results_as_hash => true,
    :type_translation => false
  )

  db.busy_timeout(config[:timeout]) unless config[:timeout].nil?

  ConnectionAdapters::SQLite3Adapter.new(db, logger)
end

.sqlite_connection(config) ⇒ Object

Establishes a connection to the database that’s used by all Active Record objects



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# File 'lib/active_record/connection_adapters/sqlite_adapter.rb', line 7

def sqlite_connection(config) # :nodoc:
  parse_sqlite_config!(config)

  unless self.class.const_defined?(:SQLite)
    require_library_or_gem(config[:adapter])

    db = SQLite::Database.new(config[:database], 0)
    db.show_datatypes   = "ON" if !defined? SQLite::Version
    db.results_as_hash  = true if defined? SQLite::Version
    db.type_translation = false

    # "Downgrade" deprecated sqlite API
    if SQLite.const_defined?(:Version)
      ConnectionAdapters::SQLite2Adapter.new(db, logger)
    else
      ConnectionAdapters::DeprecatedSQLiteAdapter.new(db, logger)
    end
  end
end

.table_exists? ⇒ Boolean

Indicates whether the table associated with this class exists

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 989

def table_exists?
  if connection.respond_to?(:tables)
    connection.tables.include? table_name
  else
    # if the connection adapter hasn't implemented tables, there are two crude tests that can be
    # used - see if getting column info raises an error, or if the number of columns returned is zero
    begin
      reset_column_information
      columns.size > 0
    rescue ActiveRecord::StatementInvalid
      false
    end          
  end
end

.table_name ⇒ Object

Guesses the table name (in forced lower-case) based on the name of the class in the inheritance hierarchy descending directly from ActiveRecord. So if the hierarchy looks like: Reply < Message < ActiveRecord, then Message is used to guess the table name even when called on Reply. The rules used to do the guess are handled by the Inflector class in Active Support, which knows almost all common English inflections. You can add new inflections in config/initializers/inflections.rb.

Nested classes are given table names prefixed by the singular form of the parent’s table name. Enclosing modules are not considered. Examples:

class Invoice < ActiveRecord::Base; end;
file                  class               table_name
invoice.rb            Invoice             invoices

class Invoice < ActiveRecord::Base; class Lineitem < ActiveRecord::Base; end; end;
file                  class               table_name
invoice.rb            Invoice::Lineitem   invoice_lineitems

module Invoice; class Lineitem < ActiveRecord::Base; end; end;
file                  class               table_name
invoice/lineitem.rb   Invoice::Lineitem   lineitems

Additionally, the class-level table_name_prefix is prepended and the table_name_suffix is appended. So if you have “myapp_” as a prefix, the table name guess for an Invoice class becomes “myapp_invoices”. Invoice::Lineitem becomes “myapp_invoice_lineitems”.

You can also overwrite this class method to allow for unguessable links, such as a Mouse class with a link to a “mice” table. Example:

class Mouse < ActiveRecord::Base
  set_table_name "mice"
end



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# File 'lib/active_record/base.rb', line 855

def table_name
  reset_table_name
end

.thread_safe_active_connections ⇒ Object

Retrieve the connection cache.



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 25

def thread_safe_active_connections #:nodoc:
  @@active_connections[Thread.current.object_id] ||= {}
end

.update(id, attributes) ⇒ Object

Updates an object (or multiple objects) and saves it to the database, if validations pass. The resulting object is returned whether the object was saved successfully to the database or not.

Options

id This should be the id or an array of ids to be updated attributes This should be a Hash of attributes to be set on the object, or an array of Hashes.

Examples

# Updating one record:
Person.update(15, {:user_name => 'Samuel', :group => 'expert'})

# Updating multiple records:
people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy"} } 	
Person.update(people.keys, people.values)



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# File 'lib/active_record/base.rb', line 543

def update(id, attributes)
  if id.is_a?(Array)
    idx = -1
    id.collect { |id| idx += 1; update(id, attributes[idx]) }
  else
    object = find(id)
    object.update_attributes(attributes)
    object
  end
end

.update_all(updates, conditions = nil, options = {}) ⇒ Object

Updates all records with details given if they match a set of conditions supplied, limits and order can also be supplied.

Options

updates A String of column and value pairs that will be set on any records that match conditions conditions An SQL fragment like “administrator = 1” or [ “user_name = ?”, username ]. 

See conditions in the intro for more info.

options Additional options are :limit and/or :order, see the examples for usage.

Examples

# Update all billing objects with the 3 different attributes given
Billing.update_all( "category = 'authorized', approved = 1, author = 'David'" )

# Update records that match our conditions
Billing.update_all( "author = 'David'", "title LIKE '%Rails%'" )

# Update records that match our conditions but limit it to 5 ordered by date
Billing.update_all( "author = 'David'", "title LIKE '%Rails%'", 
                      :order => 'created_at', :limit => 5 )



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# File 'lib/active_record/base.rb', line 620

def update_all(updates, conditions = nil, options = {})
  sql  = "UPDATE #{table_name} SET #{sanitize_sql_for_assignment(updates)} "
  scope = scope(:find)
  add_conditions!(sql, conditions, scope)
  add_order!(sql, options[:order], scope)
  add_limit!(sql, options, scope)
  connection.update(sql, "#{name} Update")
end

.update_counters(id, counters) ⇒ Object

A generic “counter updater” implementation, intended primarily to be used by increment_counter and decrement_counter, but which may also be useful on its own. It simply does a direct SQL update for the record with the given ID, altering the given hash of counters by the amount given by the corresponding value:

Options

id The id of the object you wish to update a counter on counters An Array of Hashes containing the names of the fields 

to update as keys and the amount to update the field by as
values

Examples

# For the Post with id of 5, decrement the comment_count by 1, and 
# increment the action_count by 1
Post.update_counters 5, :comment_count => -1, :action_count => 1
# Executes the following SQL:
# UPDATE posts
#    SET comment_count = comment_count - 1,
#        action_count = action_count + 1
#  WHERE id = 5



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# File 'lib/active_record/base.rb', line 684

def update_counters(id, counters)
  updates = counters.inject([]) { |list, (counter_name, increment)|
    sign = increment < 0 ? "-" : "+"
    list << "#{connection.quote_column_name(counter_name)} = #{connection.quote_column_name(counter_name)} #{sign} #{increment.abs}"
  }.join(", ")
  update_all(updates, "#{connection.quote_column_name(primary_key)} = #{quote_value(id)}")
end

.verify_active_connections! ⇒ Object

Verify active connections.



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 114

def verify_active_connections! #:nodoc:
  if @@allow_concurrency
    remove_stale_cached_threads!(@@active_connections) do |name, conn|
      conn.disconnect!
    end
  end
  
  active_connections.each_value do |connection|
    connection.verify!(@@verification_timeout)
  end
end

Instance Method Details

#==(comparison_object) ⇒ Object

Returns true if the comparison_object is the same object, or is of the same type and has the same id.



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# File 'lib/active_record/base.rb', line 2113

def ==(comparison_object)
  comparison_object.equal?(self) ||
    (comparison_object.instance_of?(self.class) && 
      comparison_object.id == id && 
      !comparison_object.new_record?)
end

#[](attr_name) ⇒ Object

Returns the value of the attribute identified by attr_name after it has been typecast (for example, “2004-12-12” in a data column is cast to a date object, like Date.new(2004, 12, 12)). (Alias for the protected read_attribute method).



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# File 'lib/active_record/base.rb', line 2020

def [](attr_name)
  read_attribute(attr_name)
end

#[]=(attr_name, value) ⇒ Object

Updates the attribute identified by attr_name with the specified value. (Alias for the protected write_attribute method).



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# File 'lib/active_record/base.rb', line 2026

def []=(attr_name, value)
  write_attribute(attr_name, value)
end

#attribute_for_inspect(attr_name) ⇒ Object

Format attributes nicely for inspect.



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# File 'lib/active_record/base.rb', line 2078

def attribute_for_inspect(attr_name)
  value = read_attribute(attr_name)

  if value.is_a?(String) && value.length > 50
    "#{value[0..50]}...".inspect
  elsif value.is_a?(Date) || value.is_a?(Time)
    %("#{value.to_s(:db)}")
  else
    value.inspect
  end
end

#attribute_names ⇒ Object

Returns an array of names for the attributes available on this object sorted alphabetically.



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# File 'lib/active_record/base.rb', line 2103

def attribute_names
  @attributes.keys.sort
end

#attribute_present?(attribute) ⇒ Boolean

Returns true if the specified attribute has been set by the user or by a database load and is neither nil nor empty? (the latter only applies to objects that respond to empty?, most notably Strings).

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 2092

def attribute_present?(attribute)
  value = read_attribute(attribute)
  !value.blank?
end

#attributes(options = nil) ⇒ Object

Returns a hash of all the attributes with their names as keys and clones of their objects as values.



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# File 'lib/active_record/base.rb', line 2052

def attributes(options = nil)
  attributes = clone_attributes :read_attribute
  
  if options.nil?
    attributes
  else
    if except = options[:except]
      except = Array(except).collect { |attribute| attribute.to_s }
      except.each { |attribute_name| attributes.delete(attribute_name) }
      attributes
    elsif only = options[:only]
      only = Array(only).collect { |attribute| attribute.to_s }
      attributes.delete_if { |key, value| !only.include?(key) }
      attributes
    else
      raise ArgumentError, "Options does not specify :except or :only (#{options.keys.inspect})"
    end
  end
end

#attributes=(new_attributes, guard_protected_attributes = true) ⇒ Object

Allows you to set all the attributes at once by passing in a hash with keys matching the attribute names (which again matches the column names). Sensitive attributes can be protected from this form of mass-assignment by using the attr_protected macro. Or you can alternatively specify which attributes can be accessed with the attr_accessible macro. Then all the attributes not included in that won’t be allowed to be mass-assigned.



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# File 'lib/active_record/base.rb', line 2035

def attributes=(new_attributes, guard_protected_attributes = true)
  return if new_attributes.nil?
  attributes = new_attributes.dup
  attributes.stringify_keys!

  multi_parameter_attributes = []
  attributes = remove_attributes_protected_from_mass_assignment(attributes) if guard_protected_attributes
  
  attributes.each do |k, v|
    k.include?("(") ? multi_parameter_attributes << [ k, v ] : send(k + "=", v)
  end

  assign_multiparameter_attributes(multi_parameter_attributes)
end

#attributes_before_type_cast ⇒ Object

Returns a hash of cloned attributes before typecasting and deserialization.



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# File 'lib/active_record/base.rb', line 2073

def attributes_before_type_cast
  clone_attributes :read_attribute_before_type_cast
end

#becomes(klass) ⇒ Object

Returns an instance of the specified klass with the attributes of the current record. This is mostly useful in relation to single-table inheritance structures where you want a subclass to appear as the superclass. This can be used along with record identification in Action Pack to allow, say, Client < Company to do something like render :partial => @client.becomes(Company) to render that instance using the companies/company partial instead of clients/client.

Note: The new instance will share a link to the same attributes as the original class. So any change to the attributes in either instance will affect the other.



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# File 'lib/active_record/base.rb', line 1941

def becomes(klass)
  returning klass.new do |became|
    became.instance_variable_set("@attributes", @attributes)
    became.instance_variable_set("@attributes_cache", @attributes_cache)
    became.instance_variable_set("@new_record", new_record?)
  end
end

#clone ⇒ Object

Returns a clone of the record that hasn’t been assigned an id yet and is treated as a new record. Note that this is a “shallow” clone: it copies the object’s attributes only, not its associations. The extent of a “deep” clone is application-specific and is therefore left to the application to implement according to its need.



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# File 'lib/active_record/base.rb', line 1926

def clone
  attrs = self.attributes_before_type_cast
  attrs.delete(self.class.primary_key)
  record = self.class.new
  record.send :instance_variable_set, '@attributes', attrs
  record
end

#column_for_attribute(name) ⇒ Object

Returns the column object for the named attribute.



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# File 'lib/active_record/base.rb', line 2108

def column_for_attribute(name)
  self.class.columns_hash[name.to_s]
end

#connection ⇒ Object

Returns the connection currently associated with the class. This can also be used to “borrow” the connection to do database work that isn’t easily done without going straight to SQL.



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# File 'lib/active_record/connection_adapters/abstract/connection_specification.rb', line 173

def connection
  self.class.connection
end

#decrement(attribute) ⇒ Object

Initializes the attribute to zero if nil and subtracts one. Only makes sense for number-based attributes. Returns self.



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# File 'lib/active_record/base.rb', line 1983

def decrement(attribute)
  self[attribute] ||= 0
  self[attribute] -= 1
  self
end

#decrement!(attribute) ⇒ Object

Decrements the attribute and saves the record.



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# File 'lib/active_record/base.rb', line 1990

def decrement!(attribute)
  decrement(attribute).update_attribute(attribute, self[attribute])
end

#destroy ⇒ Object

Deletes the record in the database and freezes this instance to reflect that no changes should be made (since they can’t be persisted).



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# File 'lib/active_record/base.rb', line 1910

def destroy
  unless new_record?
    connection.delete <<-end_sql, "#{self.class.name} Destroy"
      DELETE FROM #{self.class.quoted_table_name}
      WHERE #{connection.quote_column_name(self.class.primary_key)} = #{quoted_id}
    end_sql
  end

  freeze
end

#eql?(comparison_object) ⇒ Boolean

Delegates to ==

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 2121

def eql?(comparison_object)
  self == (comparison_object)
end

#freeze ⇒ Object

Freeze the attributes hash such that associations are still accessible, even on destroyed records.



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# File 'lib/active_record/base.rb', line 2132

def freeze
  @attributes.freeze; self
end

#frozen? ⇒ Boolean

Returns true if the attributes hash has been frozen.

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 2137

def frozen?
  @attributes.frozen?
end

#has_attribute?(attr_name) ⇒ Boolean

Returns true if the given attribute is in the attributes hash

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 2098

def has_attribute?(attr_name)
  @attributes.has_key?(attr_name.to_s)
end

#hash ⇒ Object

Delegates to id in order to allow two records of the same type and id to work with something like:

[ Person.find(1), Person.find(2), Person.find(3) ] & [ Person.find(1), Person.find(4) ] # => [ Person.find(1) ]



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# File 'lib/active_record/base.rb', line 2127

def hash
  id.hash
end

#id ⇒ Object

A model instance’s primary key is always available as model.id whether you name it the default ‘id’ or set it to something else.



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# File 'lib/active_record/base.rb', line 1862

def id
  attr_name = self.class.primary_key
  column = column_for_attribute(attr_name)
  
  self.class.send(:define_read_method, :id, attr_name, column)
  # now that the method exists, call it
  self.send attr_name.to_sym

end

#id=(value) ⇒ Object

Sets the primary ID.



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# File 'lib/active_record/base.rb', line 1887

def id=(value)
  write_attribute(self.class.primary_key, value)
end

#id_before_type_cast ⇒ Object

:nodoc:



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# File 'lib/active_record/base.rb', line 1878

def id_before_type_cast #:nodoc:
  read_attribute_before_type_cast(self.class.primary_key)
end

#increment(attribute) ⇒ Object

Initializes the attribute to zero if nil and adds one. Only makes sense for number-based attributes. Returns self.



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# File 'lib/active_record/base.rb', line 1971

def increment(attribute)
  self[attribute] ||= 0
  self[attribute] += 1
  self
end

#increment!(attribute) ⇒ Object

Increments the attribute and saves the record.



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# File 'lib/active_record/base.rb', line 1978

def increment!(attribute)
  increment(attribute).update_attribute(attribute, self[attribute])
end

#inspect ⇒ Object

Returns the contents of the record as a nicely formatted string.



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# File 'lib/active_record/base.rb', line 2153

def inspect
  attributes_as_nice_string = self.class.column_names.collect { |name|
    if has_attribute?(name) || new_record?
      "#{name}: #{attribute_for_inspect(name)}"
    end
  }.compact.join(", ")
  "#<#{self.class} #{attributes_as_nice_string}>"
end

#new_record? ⇒ Boolean

Returns true if this object hasn’t been saved yet – that is, a record for the object doesn’t exist yet.

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 1892

def new_record?
  @new_record
end

#quoted_id ⇒ Object

:nodoc:



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# File 'lib/active_record/base.rb', line 1882

def quoted_id #:nodoc:
  quote_value(id, column_for_attribute(self.class.primary_key))
end

#readonly! ⇒ Object

Marks this record as read only.



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# File 'lib/active_record/base.rb', line 2148

def readonly!
  @readonly = true
end

#readonly? ⇒ Boolean

Returns true if the record is read only. Records loaded through joins with piggy-back attributes will be marked as read only since they cannot be saved.

Returns:

  • (Boolean) 


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# File 'lib/active_record/base.rb', line 2143

def readonly?
  @readonly == true
end

#reload(options = nil) ⇒ Object

Reloads the attributes of this object from the database. The optional options argument is passed to find when reloading so you may do e.g. record.reload(:lock => true) to reload the same record with an exclusive row lock.



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# File 'lib/active_record/base.rb', line 2009

def reload(options = nil)
  clear_aggregation_cache
  clear_association_cache
  @attributes.update(self.class.find(self.id, options).instance_variable_get('@attributes'))
  @attributes_cache = {}
  self
end

#save ⇒ Object

  • No record exists: Creates a new record with values matching those of the object attributes.

  • A record does exist: Updates the record with values matching those of the object attributes.



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# File 'lib/active_record/base.rb', line 1898

def save
  create_or_update
end

#save! ⇒ Object

Attempts to save the record, but instead of just returning false if it couldn’t happen, it raises a RecordNotSaved exception



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# File 'lib/active_record/base.rb', line 1904

def save!
  create_or_update || raise(RecordNotSaved)
end

#to_param ⇒ Object

Enables Active Record objects to be used as URL parameters in Action Pack automatically.



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# File 'lib/active_record/base.rb', line 1873

def to_param
  # We can't use alias_method here, because method 'id' optimizes itself on the fly.
  (id = self.id) ? id.to_s : nil # Be sure to stringify the id for routes
end

#toggle(attribute) ⇒ Object

Turns an attribute that’s currently true into false and vice versa. Returns self.



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# File 'lib/active_record/base.rb', line 1995

def toggle(attribute)
  self[attribute] = !send("#{attribute}?")
  self
end

#toggle!(attribute) ⇒ Object

Toggles the attribute and saves the record.



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# File 'lib/active_record/base.rb', line 2001

def toggle!(attribute)
  toggle(attribute).update_attribute(attribute, self[attribute])
end

#update_attribute(name, value) ⇒ Object

Updates a single attribute and saves the record. This is especially useful for boolean flags on existing records. Note: This method is overwritten by the Validation module that’ll make sure that updates made with this method aren’t subjected to validation checks. Hence, attributes can be updated even if the full object isn’t valid.



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# File 'lib/active_record/base.rb', line 1952

def update_attribute(name, value)
  send(name.to_s + '=', value)
  save
end

#update_attributes(attributes) ⇒ Object

Updates all the attributes from the passed-in Hash and saves the record. If the object is invalid, the saving will fail and false will be returned.



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# File 'lib/active_record/base.rb', line 1959

def update_attributes(attributes)
  self.attributes = attributes
  save
end

#update_attributes!(attributes) ⇒ Object

Updates an object just like Base.update_attributes but calls save! instead of save so an exception is raised if the record is invalid.



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# File 'lib/active_record/base.rb', line 1965

def update_attributes!(attributes)
  self.attributes = attributes
  save!
end