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Module: ActiveModel::Dirty

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Included In:
::ActiveRecord::AttributeMethods::Dirty, ::ActiveRecord::Base
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 *_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_previously_changed?(from: nil, to: "Bill") # => true
person.name_previous_change     # => [nil, "Bill"]
person.name_previously_was      # => nil
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 *_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 *_will_change! on Active Record models.

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

Methods can be invoked as name_changed? or by passing an argument to the generic method attribute_changed?("name").

Constant Summary

AttributeMethods - Included

CALL_COMPILABLE_REGEXP, FORWARD_PARAMETERS, NAME_COMPILABLE_REGEXP

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.

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 127

included do
  ##
  # :method: *_previously_changed?
  #
  # :call-seq: *_previously_changed?(**options)
  #
  # This method is generated for each attribute.
  #
  # Returns true if the attribute previously had unsaved changes.
  #
  #   person = Person.new
  #   person.name = 'Britanny'
  #   person.save
  #   person.name_previously_changed? # => true
  #   person.name_previously_changed?(from: nil, to: 'Britanny') # => true

  ##
  # :method: *_changed?
  #
  # This method is generated for each attribute.
  #
  # Returns true if the attribute has unsaved changes.
  #
  #   person = Person.new
  #   person.name = 'Andrew'
  #   person.name_changed? # => true

  ##
  # :method: *_change
  #
  # This method is generated for each attribute.
  #
  # Returns the old and the new value of the attribute.
  #
  #   person = Person.new
  #   person.name = 'Nick'
  #   person.name_change # => [nil, 'Nick']

  ##
  # :method: *_will_change!
  #
  # This method is generated for each attribute.
  #
  # If an attribute is modified in-place then make use of
  # <tt>*_will_change!</tt> 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 <tt>*_will_change!</tt> on Active Record
  # models.
  #
  #   person = Person.new('Sandy')
  #   person.name_will_change!
  #   person.name_change # => ['Sandy', 'Sandy']

  ##
  # :method: *_was
  #
  # This method is generated for each attribute.
  #
  # Returns the old value of the attribute.
  #
  #   person = Person.new(name: 'Steph')
  #   person.name = 'Stephanie'
  #   person.name_was # => 'Steph'

  ##
  # :method: *_previous_change
  #
  # This method is generated for each attribute.
  #
  # Returns the old and the new value of the attribute before the last save.
  #
  #   person = Person.new
  #   person.name = 'Emmanuel'
  #   person.save
  #   person.name_previous_change # => [nil, 'Emmanuel']

  ##
  # :method: *_previously_was
  #
  # This method is generated for each attribute.
  #
  # Returns the old value of the attribute before the last save.
  #
  #   person = Person.new
  #   person.name = 'Sage'
  #   person.save
  #   person.name_previously_was  # => nil

  ##
  # :method: restore_*!
  #
  # This method is generated for each attribute.
  #
  # Restores the attribute to the old value.
  #
  #   person = Person.new
  #   person.name = 'Amanda'
  #   person.restore_name!
  #   person.name # => nil

  ##
  # :method: clear_*_change
  #
  # This method is generated for each attribute.
  #
  # Clears all dirty data of the attribute: current changes and previous changes.
  #
  #   person = Person.new(name: 'Chris')
  #   person.name = 'Jason'
  #   person.name_change # => ['Chris', 'Jason']
  #   person.clear_name_change
  #   person.name_change # => nil

  attribute_method_suffix "_previously_changed?", "_changed?", parameters: "**options"
  attribute_method_suffix "_change", "_will_change!", "_was", parameters: false
  attribute_method_suffix "_previous_change", "_previously_was", parameters: false
  attribute_method_affix prefix: "restore_", suffix: "!", parameters: false
  attribute_method_affix prefix: "clear_", suffix: "_change", parameters: false
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 ]


  








  

    #changed?  ⇒ Boolean  (readonly)
  



  

    

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



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


  





  


  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 279



def changed?
  mutations_from_database.any_changes?
end


  







Instance Method Details



  

    #attribute_changed?(attr_name, **options)  ⇒ Boolean 
  



  

    

Dispatch target for *_changed? attribute methods.


  





  


  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 293



def attribute_changed?(attr_name, **options)
  mutations_from_database.changed?(attr_name.to_s, **options)
end


  








  

    #attribute_previously_changed?(attr_name, **options)  ⇒ Boolean 
  



  

    

Dispatch target for *_previously_changed? attribute methods.


  





  


  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 303



def attribute_previously_changed?(attr_name, **options)
  mutations_before_last_save.changed?(attr_name.to_s, **options)
end


  








  

    #attribute_previously_was(attr_name)  
  



  

    

Dispatch target for *_previously_was attribute methods.


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 308



def attribute_previously_was(attr_name)
  mutations_before_last_save.original_value(attr_name.to_s)
end


  








  

    #attribute_was(attr_name)  
  



  

    

Dispatch target for *_was attribute methods.


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 298



def attribute_was(attr_name)
  mutations_from_database.original_value(attr_name.to_s)
end


  








  

    #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 288



def changed
  mutations_from_database.changed_attribute_names
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 336



def changed_attributes
  mutations_from_database.changed_values
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 346



def changes
  mutations_from_database.changes
end


  








  

    #changes_applied  
  



  

    

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


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 265



def changes_applied
  unless defined?(@attributes)
    mutations_from_database.finalize_changes
  end
  @mutations_before_last_save = mutations_from_database
  forget_attribute_assignments
  @mutations_from_database = nil
end


  








  

    #clear_attribute_changes(attr_names)  
  

  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 324



def clear_attribute_changes(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 318



def clear_changes_information
  @mutations_before_last_save = nil
  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 356



def previous_changes
  mutations_before_last_save.changes
end


  








  

    #restore_attributes(attr_names = changed)  
  



  

    

Restore all previous data of the provided attributes.


  



  [ GitHub ]


  

  


# File 'activemodel/lib/active_model/dirty.rb', line 313



def restore_attributes(attr_names = changed)
  attr_names.each { |attr_name| restore_attribute!(attr_name) }
end