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,
lib/active_record/attribute_methods/composite_primary_key.rb

Overview

Active Record Attribute Methods

Defined Under Namespace

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

Constant Summary collapse

RESTRICTED_CLASS_METHODS = 
%w(private public protected allocate new name superclass)

Class Method Summary collapse

Instance Method Summary collapse

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(name) ⇒ Object (private) 



475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
 
# File 'lib/active_record/attribute_methods.rb', line 475

def method_missing(name, ...)
  # We can't know whether some method was defined or not because
  # multiple thread might be concurrently be in this code path.
  # So the first one would define the methods and the others would
  # appear to already have them.
  self.class.define_attribute_methods

  # So in all cases we must behave as if the method was just defined.
  method = begin
    self.class.public_instance_method(name)
  rescue NameError
    nil
  end

  # The method might be explicitly defined in the model, but call a generated
  # method with super. So we must resume the call chain at the right step.
  method = method.super_method while method && !method.owner.is_a?(GeneratedAttributeMethods)
  if method
    method.bind_call(self, ...)
  else
    super
  end
end

Class Method Details

.dangerous_attribute_methods ⇒ Object

:nodoc:



30
31
32
33
34
35
36
37
38
 
# File 'lib/active_record/attribute_methods.rb', line 30

def dangerous_attribute_methods # :nodoc:
  @dangerous_attribute_methods ||= (
    Base.instance_methods +
    Base.private_instance_methods -
    Base.superclass.instance_methods -
    Base.superclass.private_instance_methods +
    %i[__id__ dup freeze frozen? hash class clone]
  ).map { |m| -m.to_s }.to_set.freeze
end

Instance Method Details

#[](attr_name) ⇒ Object

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



415
416
417
 
# File 'lib/active_record/attribute_methods.rb', line 415

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

#[]=(attr_name, value) ⇒ Object

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)



428
429
430
 
# File 'lib/active_record/attribute_methods.rb', line 428

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

#_has_attribute?(attr_name) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


322
323
324
 
# File 'lib/active_record/attribute_methods.rb', line 322

def _has_attribute?(attr_name) # :nodoc:
  @attributes.key?(attr_name)
end

#accessed_fields ⇒ Object

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



460
461
462
 
# File 'lib/active_record/attribute_methods.rb', line 460

def accessed_fields
  @attributes.accessed
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. 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]"



365
366
367
368
369
370
 
# File 'lib/active_record/attribute_methods.rb', line 365

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 ⇒ 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"]



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

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

Returns:

  • (Boolean) 


387
388
389
390
391
392
 
# File 'lib/active_record/attribute_methods.rb', line 387

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 ⇒ 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}



346
347
348
 
# File 'lib/active_record/attribute_methods.rb', line 346

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

Returns:

  • (Boolean) 


316
317
318
319
320
 
# File 'lib/active_record/attribute_methods.rb', line 316

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

Returns:

  • (Boolean) 


291
292
293
294
295
296
297
298
299
300
301
302
303
 
# File 'lib/active_record/attribute_methods.rb', line 291

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

  true
end