Module: ActiveRecord::AttributeMethods

Extended by:
ActiveSupport::Autoload, ActiveSupport::Concern
Includes:
ActiveModel::AttributeMethods
Included in:
Base
Defined in:
lib/active_record/attribute_methods.rb,
lib/active_record.rb,
lib/active_record/attribute_methods/read.rb,
lib/active_record/attribute_methods/dirty.rb,
lib/active_record/attribute_methods/query.rb,
lib/active_record/attribute_methods/write.rb,
lib/active_record/attribute_methods/primary_key.rb,
lib/active_record/attribute_methods/serialization.rb,
lib/active_record/attribute_methods/before_type_cast.rb,
lib/active_record/attribute_methods/time_zone_conversion.rb

Overview

Active Record Attribute Methods

Defined Under Namespace

Modules: BeforeTypeCast, ClassMethods, Dirty, PrimaryKey, Query, Read, Serialization, TimeZoneConversion, Write

Instance Method Summary collapse

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method, *args, &block) ⇒ Object

If we haven’t generated any methods yet, generate them, then see if we’ve created the method we’re looking for.



145
146
147
148
149
150
151
152
153
154
155
156
157
 
# File 'lib/active_record/attribute_methods.rb', line 145

def method_missing(method, *args, &block) # :nodoc:
  unless self.class.attribute_methods_generated?
    self.class.define_attribute_methods

    if respond_to_without_attributes?(method)
      send(method, *args, &block)
    else
      super
    end
  else
    super
  end
end

Instance Method Details

#[](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)). It raises ActiveModel::MissingAttributeError if the identified attribute is missing.

Alias for the read_attribute method.

class Person < ActiveRecord::Base
  belongs_to :organization
end

person = Person.new(name: 'Francesco', age: '22')
person[:name] # => "Francesco"
person[:age]  # => 22

person = Person.select('id').first
person[:name]            # => ActiveModel::MissingAttributeError: missing attribute: name
person[:organization_id] # => ActiveModel::MissingAttributeError: missing attribute: organization_id



326
327
328
 
# File 'lib/active_record/attribute_methods.rb', line 326

def [](attr_name)
  read_attribute(attr_name) { |n| missing_attribute(n, caller) }
end

#[]=(attr_name, value) ⇒ Object

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

class Person < ActiveRecord::Base
end

person = Person.new
person[:age] = '22'
person[:age] # => 22
person[:age] # => Fixnum



340
341
342
 
# File 'lib/active_record/attribute_methods.rb', line 340

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

#attribute_for_inspect(attr_name) ⇒ Object

Returns an #inspect-like string for the value of the attribute attr_name. String attributes are truncated upto 50 characters, and Date and Time attributes are returned in the :db format. Other attributes return the value of #inspect without modification.

person = Person.create!(name: 'David Heinemeier Hansson ' * 3)

person.attribute_for_inspect(:name)
# => "\"David Heinemeier Hansson David Heinemeier Hansson D...\""

person.attribute_for_inspect(:created_at)
# => "\"2012-10-22 00:15:07\""



260
261
262
263
264
265
266
267
268
269
270
 
# File 'lib/active_record/attribute_methods.rb', line 260

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_missing(match, *args, &block) ⇒ Object

:nodoc:



159
160
161
162
163
164
165
166
167
168
169
170
171
 
# File 'lib/active_record/attribute_methods.rb', line 159

def attribute_missing(match, *args, &block) # :nodoc:
  if self.class.columns_hash[match.attr_name]
    ActiveSupport::Deprecation.warn(
      "The method `#{match.method_name}', matching the attribute `#{match.attr_name}' has " \
      "dispatched through method_missing. This shouldn't happen, because `#{match.attr_name}' " \
      "is a column of the table. If this error has happened through normal usage of Active " \
      "Record (rather than through your own code or external libraries), please report it as " \
      "a bug."
    )
  end

  super
end

#attribute_names ⇒ Object

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

class Person < ActiveRecord::Base
end

person = Person.new
person.attribute_names
# => ["id", "created_at", "updated_at", "name", "age"]



229
230
231
 
# File 'lib/active_record/attribute_methods.rb', line 229

def attribute_names
  @attributes.keys
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). Otherwise, false. Note that it always returns true with boolean attributes.

class Task < ActiveRecord::Base
end

person = Task.new(title: '', is_done: false)
person.attribute_present?(:title)   # => false
person.attribute_present?(:is_done) # => true
person.name = 'Francesco'
person.is_done = true
person.attribute_present?(:title)   # => true
person.attribute_present?(:is_done) # => true

Returns:

  • (Boolean) 


287
288
289
290
 
# File 'lib/active_record/attribute_methods.rb', line 287

def attribute_present?(attribute)
  value = read_attribute(attribute)
  !value.nil? && !(value.respond_to?(:empty?) && value.empty?)
end

#attributes ⇒ Object

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

class Person < ActiveRecord::Base
end

person = Person.create(name: 'Francesco', age: 22)
person.attributes
# => {"id"=>3, "created_at"=>Sun, 21 Oct 2012 04:53:04, "updated_at"=>Sun, 21 Oct 2012 04:53:04, "name"=>"Francesco", "age"=>22}



241
242
243
244
245
 
# File 'lib/active_record/attribute_methods.rb', line 241

def attributes
  attribute_names.each_with_object({}) { |name, attrs|
    attrs[name] = read_attribute(name)
  }
end

#column_for_attribute(name) ⇒ Object

Returns the column object for the named attribute. Returns nil if the named attribute not exists.

class Person < ActiveRecord::Base
end

person = Person.new
person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
# => #<ActiveRecord::ConnectionAdapters::SQLite3Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>

person.column_for_attribute(:nothing)
# => nil



304
305
306
307
 
# File 'lib/active_record/attribute_methods.rb', line 304

def column_for_attribute(name)
  # FIXME: should this return a null object for columns that don't exist?
  self.class.columns_hash[name.to_s]
end

#has_attribute?(attr_name) ⇒ Boolean

Returns true if the given attribute is in the attributes hash, otherwise false.

class Person < ActiveRecord::Base
end

person = Person.new
person.has_attribute?(:name)    # => true
person.has_attribute?('age')    # => true
person.has_attribute?(:nothing) # => false

Returns:

  • (Boolean) 


217
218
219
 
# File 'lib/active_record/attribute_methods.rb', line 217

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

#respond_to?(name, include_private = false) ⇒ Boolean

A Person object with a name attribute can ask person.respond_to?(:name), person.respond_to?(:name=), and person.respond_to?(:name?) which will all return true. It also define the attribute methods if they have not been generated.

class Person < ActiveRecord::Base
end

person = Person.new
person.respond_to(:name)    # => true
person.respond_to(:name=)   # => true
person.respond_to(:name?)   # => true
person.respond_to('age')    # => true
person.respond_to('age=')   # => true
person.respond_to('age?')   # => true
person.respond_to(:nothing) # => false

Returns:

  • (Boolean) 


189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
 
# File 'lib/active_record/attribute_methods.rb', line 189

def respond_to?(name, include_private = false)
  name = name.to_s
  self.class.define_attribute_methods unless self.class.attribute_methods_generated?
  result = super

  # If the result is false the answer is false.
  return false unless result

  # If the result is true then check for the select case.
  # For queries selecting a subset of columns, return false for unselected columns.
  # We check defined?(@attributes) not to issue warnings if called on objects that
  # have been allocated but not yet initialized.
  if defined?(@attributes) && @attributes.present? && self.class.column_names.include?(name)
    return has_attribute?(name)
  end

  return true
end