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Module: ActiveRecord::AttributeMethods

Constant Summary

::ActiveModel::AttributeMethods - Included

CALL_COMPILABLE_REGEXP, FORWARD_PARAMETERS, NAME_COMPILABLE_REGEXP

::ActiveModel::AttributeMethods - Attributes & Methods

Class Method Summary

::ActiveSupport::Concern - Extended

class_methods

Define class methods from given block.

included

Evaluate given block in context of base class, so that you can write class macros here.

prepended

Evaluate given block in context of base class, so that you can write class macros here.

::ActiveSupport::Autoload - Extended

Instance Method Summary

::ActiveModel::AttributeMethods - Included

#attribute_missing

attribute_missing is like #method_missing, but for attributes.

#method_missing

Allows access to the object attributes, which are held in the hash returned by #attributes, as though they were first-class methods.

#respond_to?,
#respond_to_without_attributes?

A Person instance with a name attribute can ask person.respond_to?(:name), person.respond_to?(:name=), and person.respond_to?(:name?) which will all return true.

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(name) (private)

[ GitHub ]

  
# File 'activerecord/lib/active_record/attribute_methods.rb', line 482

def method_missing(name, ...)
  unless self.class.attribute_methods_generated?
    if self.class.method_defined?(name)
      # The method is explicitly defined in the model, but calls a generated
      # method with super. So we must resume the call chain at the right setp.
      last_method = method(name)
      last_method = last_method.super_method while last_method.super_method
      self.class.define_attribute_methods
      if last_method.super_method
        return last_method.super_method.call(...)
      end
    elsif self.class.define_attribute_methods | self.class.generate_alias_attributes
      # Some attribute methods weren't generated yet, we retry the call
      return public_send(name, ...)
    end
  end

  super
end

DSL Calls

included

[ GitHub ]


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 12

included do
  initialize_generated_modules
  include Read
  include Write
  include BeforeTypeCast
  include Query
  include PrimaryKey
  include TimeZoneConversion
  include Dirty
  include Serialization
end

Class Attribute Details

.attribute_aliases (rw)

[ GitHub ]

  
# File 'activemodel/lib/active_model/attribute_methods.rb', line 72

class_attribute :attribute_aliases, instance_writer: false, default: {}

.attribute_aliases?Boolean (rw)

[ GitHub ]

  
# File 'activemodel/lib/active_model/attribute_methods.rb', line 72

class_attribute :attribute_aliases, instance_writer: false, default: {}

.attribute_method_patterns (rw)

[ GitHub ]

  
# File 'activemodel/lib/active_model/attribute_methods.rb', line 73

class_attribute :attribute_method_patterns, instance_writer: false, default: [ ClassMethods::AttributeMethodPattern.new ]

.attribute_method_patterns?Boolean (rw)

[ GitHub ]

  
# File 'activemodel/lib/active_model/attribute_methods.rb', line 73

class_attribute :attribute_method_patterns, instance_writer: false, default: [ ClassMethods::AttributeMethodPattern.new ]

Instance Attribute Details

#attribute_aliases (readonly)

[ GitHub ]

  
# File 'activemodel/lib/active_model/attribute_methods.rb', line 72

class_attribute :attribute_aliases, instance_writer: false, default: {}

#attribute_aliases?Boolean (readonly)

[ GitHub ]

  
# File 'activemodel/lib/active_model/attribute_methods.rb', line 72

class_attribute :attribute_aliases, instance_writer: false, default: {}

#attribute_method_patterns (readonly)

[ GitHub ]

  
# File 'activemodel/lib/active_model/attribute_methods.rb', line 73

class_attribute :attribute_method_patterns, instance_writer: false, default: [ ClassMethods::AttributeMethodPattern.new ]

#attribute_method_patterns?Boolean (readonly)

[ GitHub ]

  
# File 'activemodel/lib/active_model/attribute_methods.rb', line 73

class_attribute :attribute_method_patterns, instance_writer: false, default: [ ClassMethods::AttributeMethodPattern.new ]

Instance Method Details

#[](attr_name)

Returns the value of the attribute identified by attr_name after it has been type cast. (For information about specific type casting behavior, see the types under ::ActiveModel::Type.)

class Person < ActiveRecord::Base
  belongs_to :organization
end

person = Person.new(name: "Francesco", date_of_birth: "2004-12-12")
person[:name]            # => "Francesco"
person[:date_of_birth]   # => Date.new(2004, 12, 12)
person[:organization_id] # => nil

Raises ::ActiveModel::MissingAttributeError if the attribute is missing. Note, however, that the id attribute will never be considered missing.

person = Person.select(:name).first
person[:name]            # => "Francesco"
person[:date_of_birth]   # => ActiveModel::MissingAttributeError: missing attribute 'date_of_birth' for Person
person[:organization_id] # => ActiveModel::MissingAttributeError: missing attribute 'organization_id' for Person
person[:id]              # => nil
[ GitHub ]

  
# File 'activerecord/lib/active_record/attribute_methods.rb', line 422

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

#[]=(attr_name, value)

Updates the attribute identified by attr_name using the specified value. The attribute value will be type cast upon being read.

class Person < ActiveRecord::Base
end

person = Person.new
person[:date_of_birth] = "2004-12-12"
person[:date_of_birth] # => Date.new(2004, 12, 12)
[ GitHub ]

  
# File 'activerecord/lib/active_record/attribute_methods.rb', line 435

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

#accessed_fields

Returns the name of all database fields which have been read from this model. This can be useful in development mode to determine which fields need to be selected. For performance critical pages, selecting only the required fields can be an easy performance win (assuming you aren’t using all of the fields on the model).

For example:

class PostsController < ActionController::Base
  after_action :print_accessed_fields, only: :index

  def index
    @posts = Post.all
  end

  private
    def print_accessed_fields
      p @posts.first.accessed_fields
    end
end

Which allows you to quickly change your code to:

class PostsController < ActionController::Base
  def index
    @posts = Post.select(:id, :title, :author_id, :updated_at)
  end
end
[ GitHub ]

  
# File 'activerecord/lib/active_record/attribute_methods.rb', line 467

def accessed_fields
  @attributes.accessed
end

#attribute_for_inspect(attr_name)

Returns an #inspect-like string for the value of the attribute attr_name. ::String attributes are truncated up to 50 characters. 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 00:15:07.000000000 +0000\""

person.attribute_for_inspect(:tag_ids)
# => "[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]"
[ GitHub ]

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

def attribute_for_inspect(attr_name)
  attr_name = attr_name.to_s
  attr_name = self.class.attribute_aliases[attr_name] || attr_name
  value = _read_attribute(attr_name)
  format_for_inspect(attr_name, value)
end

#attribute_names

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"]
[ GitHub ]

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

def attribute_names
  @attributes.keys
end

#attribute_present?(attr_name) ⇒ 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
[ GitHub ]

  
# File 'activerecord/lib/active_record/attribute_methods.rb', line 394

def attribute_present?(attr_name)
  attr_name = attr_name.to_s
  attr_name = self.class.attribute_aliases[attr_name] || attr_name
  value = _read_attribute(attr_name)
  !value.nil? && !(value.respond_to?(:empty?) && value.empty?)
end

#attributes

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}
[ GitHub ]

  
# File 'activerecord/lib/active_record/attribute_methods.rb', line 353

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
  alias_attribute :new_name, :name
end

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

  
# File 'activerecord/lib/active_record/attribute_methods.rb', line 323

def has_attribute?(attr_name)
  attr_name = attr_name.to_s
  attr_name = self.class.attribute_aliases[attr_name] || attr_name
  @attributes.key?(attr_name)
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 defines 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
[ GitHub ]

  
# File 'activerecord/lib/active_record/attribute_methods.rb', line 296

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

  # 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)
    if name = self.class.symbol_column_to_string(name.to_sym)
      return _has_attribute?(name)
    end
  end

  true
end