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 Classes: AttributeMethodCache, GeneratedAttributeMethods

Constant Summary collapse

AttrNames = 
Module.new {
  def self.set_name_cache(name, value)
    const_name = "ATTR_#{name}"
    unless const_defined? const_name
      const_set const_name, value.dup.freeze
    end
  end
}
BLACKLISTED_CLASS_METHODS = 
%w(private public protected allocate new name parent superclass)

Instance Method Summary collapse

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 date column is cast to a date object, like Date.new(2004, 12, 12)). It raises ActiveModel::MissingAttributeError if the identified attribute is missing.

Note: :id is always present.

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



358
359
360
 
# File 'lib/active_record/attribute_methods.rb', line 358

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



372
373
374
 
# File 'lib/active_record/attribute_methods.rb', line 372

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 up to 50 characters, Date and Time attributes are returned in the :db format, Array attributes are truncated up to 10 values. 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 ...\""

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

person.attribute_for_inspect(:tag_ids)
# => "[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ...]"



304
305
306
307
308
309
310
311
312
313
314
315
316
317
 
# File 'lib/active_record/attribute_methods.rb', line 304

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)}")
  elsif value.is_a?(Array) && value.size > 10
    inspected = value.first(10).inspect
    %(#{inspected[0...-1]}, ...])
  else
    value.inspect
  end
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"]



271
272
273
 
# File 'lib/active_record/attribute_methods.rb', line 271

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

task = Task.new(title: '', is_done: false)
task.attribute_present?(:title)   # => false
task.attribute_present?(:is_done) # => true
task.title = 'Buy milk'
task.is_done = true
task.attribute_present?(:title)   # => true
task.attribute_present?(:is_done) # => true

Returns:

  • (Boolean) 


334
335
336
337
 
# File 'lib/active_record/attribute_methods.rb', line 334

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}



283
284
285
 
# File 'lib/active_record/attribute_methods.rb', line 283

def attributes
  @attributes.to_hash
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) 


259
260
261
 
# File 'lib/active_record/attribute_methods.rb', line 259

def has_attribute?(attr_name)
  @attributes.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) 


235
236
237
238
239
240
241
242
243
244
245
246
247
248
 
# File 'lib/active_record/attribute_methods.rb', line 235

def respond_to?(name, include_private = false)
  return false unless super
  name = name.to_s

  # 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) && self.class.column_names.include?(name)
    return has_attribute?(name)
  end

  return true
end