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Module: ActiveModel::Dirty

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Included In:
::ActiveRecord::AttributeMethods::Dirty, ::ActiveRecord::Base, ActiveRecord::InternalMetadata, ActiveRecord::SchemaMigration
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::ActiveSupport::Concern
Instance Chain:
self, AttributeMethods
Defined in: activemodel/lib/active_model/dirty.rb

Overview

Provides a way to track changes in your object in the same way as Active Record does.

The requirements for implementing Dirty are:

  • include ActiveModel::Dirty in your object.

  • Call define_attribute_methods passing each method you want to track.

  • Call [attr_name]_will_change! before each change to the tracked attribute.

  • Call #changes_applied after the changes are persisted.

  • Call #clear_changes_information when you want to reset the changes information.

  • Call #restore_attributes when you want to restore previous data.

A minimal implementation could be:

class Person
  include ActiveModel::Dirty

  define_attribute_methods :name

  def initialize
    @name = nil
  end

  def name
    @name
  end

  def name=(val)
    name_will_change! unless val == @name
    @name = val
  end

  def save
    # do persistence work

    changes_applied
  end

  def reload!
    # get the values from the persistence layer

    clear_changes_information
  end

  def rollback!
    restore_attributes
  end
end

A newly instantiated Person object is unchanged:

person = Person.new
person.changed? # => false

Change the name:

person.name = 'Bob'
person.changed?       # => true
person.name_changed?  # => true
person.name_changed?(from: nil, to: "Bob") # => true
person.name_was       # => nil
person.name_change    # => [nil, "Bob"]
person.name = 'Bill'
person.name_change    # => [nil, "Bill"]

Save the changes:

person.save
person.changed?      # => false
person.name_changed? # => false

Reset the changes:

person.previous_changes         # => {"name" => [nil, "Bill"]}
person.name_previously_changed? # => true
person.name_previous_change     # => [nil, "Bill"]
person.reload!
person.previous_changes         # => {}

Rollback the changes:

person.name = "Uncle Bob"
person.rollback!
person.name          # => "Bill"
person.name_changed? # => false

Assigning the same value leaves the attribute unchanged:

person.name = 'Bill'
person.name_changed? # => false
person.name_change   # => nil

Which attributes have changed?

person.name = 'Bob'
person.changed # => ["name"]
person.changes # => {"name" => ["Bill", "Bob"]}

If an attribute is modified in-place then make use of [attribute_name]_will_change! to mark that the attribute is changing. Otherwise Active Model can’t track changes to in-place attributes. Note that Active Record can detect in-place modifications automatically. You do not need to call [attribute_name]_will_change! on Active Record models.

person.name_will_change!
person.name_change # => ["Bill", "Bill"]
person.name << 'y'
person.name_change # => ["Bill", "Billy"]

Constant Summary

AttributeMethods - Included

CALL_COMPILABLE_REGEXP, NAME_COMPILABLE_REGEXP

AttributeMethods - Attributes & Methods

Class Method Summary

::ActiveSupport::Concern - Extended

append_features, class_methods, included

Instance Attribute Summary

Instance Method Summary

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 in the class ActiveModel::AttributeMethods

DSL Calls

included

[ GitHub ] 


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# File 'activemodel/lib/active_model/dirty.rb', line 128

included do
  attribute_method_suffix "_changed?", "_change", "_will_change!", "_was"
  attribute_method_suffix "_previously_changed?", "_previous_change"
  attribute_method_affix prefix: "restore_", suffix: "!"
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_matchers   (rw)
  

  [ GitHub ]


  

  


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



class_attribute :attribute_method_matchers, instance_writer: false, default: [ ClassMethods::AttributeMethodMatcher.new ]


  








  

    .attribute_method_matchers?  ⇒ Boolean  (rw)
  

  [ GitHub ]


  

  


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



class_attribute :attribute_method_matchers, instance_writer: false, default: [ ClassMethods::AttributeMethodMatcher.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_matchers   (readonly)
  

  [ GitHub ]


  

  


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



class_attribute :attribute_method_matchers, instance_writer: false, default: [ ClassMethods::AttributeMethodMatcher.new ]


  








  

    #attribute_method_matchers?  ⇒ Boolean  (readonly)
  

  [ GitHub ]


  

  


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



class_attribute :attribute_method_matchers, instance_writer: false, default: [ ClassMethods::AttributeMethodMatcher.new ]


  








  

    #changed?  ⇒ Boolean  (readonly)
  



  

    

Returns true if any of the attributes have unsaved changes, false otherwise.



person.changed? # => false
person.name = 'bob'
person.changed? # => true


  





  


  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 161



def changed?
  changed_attributes.present?
end


  







Instance Method Details



  

    #changed   (readonly)
  



  

    

Returns an array with the name of the attributes with unsaved changes.



person.changed # => []
person.name = 'bob'
person.changed # => ["name"]


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 170



def changed
  changed_attributes.keys
end


  








  

    #changed_attributes  
  



  

    

Returns a hash of the attributes with unsaved changes indicating their original values like attr => original value.



person.name # => "bob"
person.name = 'robert'
person.changed_attributes # => {"name" => "bob"}


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 218



def changed_attributes
  # This should only be set by methods which will call changed_attributes
  # multiple times when it is known that the computed value cannot change.
  if defined?(@cached_changed_attributes)
    @cached_changed_attributes
  else
    attributes_changed_by_setter.reverse_merge(mutations_from_database.changed_values).freeze
  end
end


  








  

    #changes  
  



  

    

Returns a hash of changed attributes indicating their original and new values like attr => [original value, new value].



person.changes # => {}
person.name = 'bob'
person.changes # => { "name" => ["bill", "bob"] }


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 234



def changes
  cache_changed_attributes do
    ActiveSupport::HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }]
  end
end


  








  

    #changes_applied  
  



  

    

Clears dirty data and moves #changes to previously_changed and #mutations_from_database to #mutations_before_last_save respectively.


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 146



def changes_applied
  unless defined?(@attributes)
    @previously_changed = changes
  end
  @mutations_before_last_save = mutations_from_database
  @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
  forget_attribute_assignments
  @mutations_from_database = nil
end


  








  

    #clear_attribute_changes(attr_names)  
  

  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 205



def clear_attribute_changes(attr_names)
  attributes_changed_by_setter.except!(*attr_names)
  attr_names.each do |attr_name|
    clear_attribute_change(attr_name)
  end
end


  








  

    #clear_changes_information  
  



  

    

Clears all dirty data: current changes and previous changes.


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 197



def clear_changes_information
  @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
  @mutations_before_last_save = nil
  @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
  forget_attribute_assignments
  @mutations_from_database = nil
end


  








  

    #previous_changes  
  



  

    

Returns a hash of attributes that were changed before the model was saved.



person.name # => "bob"
person.name = 'robert'
person.save
person.previous_changes # => {"name" => ["bob", "robert"]}


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 246



def previous_changes
  @previously_changed ||= ActiveSupport::HashWithIndifferentAccess.new
  @previously_changed.merge(mutations_before_last_save.changes)
end


  








  

    #restore_attributes(attributes = changed)  
  



  

    

Restore all previous data of the provided attributes.


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 192



def restore_attributes(attributes = changed)
  attributes.each { |attr| restore_attribute! attr }
end