Module: ActiveModel::Dirty

Extended by:
ActiveSupport::Concern
Includes:
AttributeMethods
Included in:
ActiveRecord::AttributeMethods::Dirty
Defined in:
activemodel/lib/active_model/dirty.rb

Overview

Active Model Dirty

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

The requirements for implementing ActiveModel::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_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 [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

Constants included from AttributeMethods

AttributeMethods::CALL_COMPILABLE_REGEXP, AttributeMethods::NAME_COMPILABLE_REGEXP

Instance Method Summary collapse

Methods included from ActiveSupport::Concern

append_features, class_methods, extended, included, prepend_features, prepended

Methods included from AttributeMethods

#attribute_missing, #method_missing, #respond_to?, #respond_to_without_attributes?

Dynamic Method Handling

This class handles dynamic methods through the method_missing method in the class ActiveModel::AttributeMethods

Instance Method Details

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

Dispatch target for *_changed? attribute methods.

Returns:

  • (Boolean)

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# File 'activemodel/lib/active_model/dirty.rb', line 171

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

#attribute_changed_in_place?(attr_name) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean)

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# File 'activemodel/lib/active_model/dirty.rb', line 238

def attribute_changed_in_place?(attr_name) # :nodoc:
  mutations_from_database.changed_in_place?(attr_name.to_s)
end

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

Dispatch target for *_previously_changed? attribute methods.

Returns:

  • (Boolean)

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# File 'activemodel/lib/active_model/dirty.rb', line 181

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

#attribute_previously_was(attr_name) ⇒ Object

Dispatch target for *_previously_was attribute methods.


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# File 'activemodel/lib/active_model/dirty.rb', line 186

def attribute_previously_was(attr_name) # :nodoc:
  mutations_before_last_save.original_value(attr_name.to_s)
end

#attribute_was(attr_name) ⇒ Object

Dispatch target for *_was attribute methods.


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# File 'activemodel/lib/active_model/dirty.rb', line 176

def attribute_was(attr_name) # :nodoc:
  mutations_from_database.original_value(attr_name.to_s)
end

#changedObject

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

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

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# File 'activemodel/lib/active_model/dirty.rb', line 166

def changed
  mutations_from_database.changed_attribute_names
end

#changed?Boolean

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

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

Returns:

  • (Boolean)

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# File 'activemodel/lib/active_model/dirty.rb', line 157

def changed?
  mutations_from_database.any_changes?
end

#changed_attributesObject

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"}

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# File 'activemodel/lib/active_model/dirty.rb', line 214

def changed_attributes
  mutations_from_database.changed_values
end

#changesObject

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"] }

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# File 'activemodel/lib/active_model/dirty.rb', line 224

def changes
  mutations_from_database.changes
end

#changes_appliedObject

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


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# File 'activemodel/lib/active_model/dirty.rb', line 143

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) ⇒ Object


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# File 'activemodel/lib/active_model/dirty.rb', line 202

def clear_attribute_changes(attr_names)
  attr_names.each do |attr_name|
    clear_attribute_change(attr_name)
  end
end

#clear_changes_informationObject

Clears all dirty data: current changes and previous changes.


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# File 'activemodel/lib/active_model/dirty.rb', line 196

def clear_changes_information
  @mutations_before_last_save = nil
  forget_attribute_assignments
  @mutations_from_database = nil
end

#initialize_dup(other) ⇒ Object

:nodoc:


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# File 'activemodel/lib/active_model/dirty.rb', line 131

def initialize_dup(other) # :nodoc:
  super
  if self.class.respond_to?(:_default_attributes)
    @attributes = self.class._default_attributes.map do |attr|
      attr.with_value_from_user(@attributes.fetch_value(attr.name))
    end
  end
  @mutations_from_database = nil
end

#previous_changesObject

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"]}

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

def previous_changes
  mutations_before_last_save.changes
end

#restore_attributes(attr_names = changed) ⇒ Object

Restore all previous data of the provided attributes.


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# File 'activemodel/lib/active_model/dirty.rb', line 191

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