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require 'active_support/hash_with_indifferent_access'
require 'active_support/core_ext/object/duplicable'
module ActiveModel
# == 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:
#
# * <tt>include ActiveModel::Dirty</tt> in your object.
# * Call <tt>define_attribute_methods</tt> passing each method you want to
# track.
# * Call <tt>[attr_name]_will_change!</tt> before each change to the tracked
# attribute.
# * Call <tt>changes_applied</tt> after the changes are persisted.
# * Call <tt>clear_changes_information</tt> when you want to reset the changes
# information.
# * Call <tt>restore_attributes</tt> when you want to restore previous data.
#
# A minimal implementation could be:
#
# class Person
# include ActiveModel::Dirty
#
# define_attribute_methods :name
#
# 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 object is unchanged:
#
# person = Person.find_by(name: 'Uncle Bob')
# person.changed? # => false
#
# Change the name:
#
# person.name = 'Bob'
# person.changed? # => true
# person.name_changed? # => true
# person.name_changed?(from: "Uncle Bob", to: "Bob") # => true
# person.name_was # => "Uncle Bob"
# person.name_change # => ["Uncle Bob", "Bob"]
# person.name = 'Bill'
# person.name_change # => ["Uncle Bob", "Bill"]
#
# Save the changes:
#
# person.save
# person.changed? # => false
# person.name_changed? # => false
#
# Reset the changes:
#
# person.previous_changes # => {"name" => ["Uncle Bob", "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"]
module Dirty
extend ActiveSupport::Concern
include ActiveModel::AttributeMethods
included do
attribute_method_suffix '_changed?', '_change', '_will_change!', '_was'
attribute_method_affix prefix: 'restore_', suffix: '!'
end
# Returns +true+ if any attribute have unsaved changes, +false+ otherwise.
#
# person.changed? # => false
# person.name = 'bob'
# person.changed? # => true
def changed?
changed_attributes.present?
end
# Returns an array with the name of the attributes with unsaved changes.
#
# person.changed # => []
# person.name = 'bob'
# person.changed # => ["name"]
def changed
changed_attributes.keys
end
# Returns a hash of changed attributes indicating their original
# and new values like <tt>attr => [original value, new value]</tt>.
#
# person.changes # => {}
# person.name = 'bob'
# person.changes # => { "name" => ["bill", "bob"] }
def changes
ActiveSupport::HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }]
end
# 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"]}
def previous_changes
@previously_changed ||= ActiveSupport::HashWithIndifferentAccess.new
end
# Returns a hash of the attributes with unsaved changes indicating their original
# values like <tt>attr => original value</tt>.
#
# person.name # => "bob"
# person.name = 'robert'
# person.changed_attributes # => {"name" => "bob"}
def changed_attributes
@changed_attributes ||= ActiveSupport::HashWithIndifferentAccess.new
end
# Handle <tt>*_changed?</tt> for +method_missing+.
def attribute_changed?(attr, options = {}) #:nodoc:
result = changes_include?(attr)
result &&= options[:to] == __send__(attr) if options.key?(:to)
result &&= options[:from] == changed_attributes[attr] if options.key?(:from)
result
end
# Handle <tt>*_was</tt> for +method_missing+.
def attribute_was(attr) # :nodoc:
attribute_changed?(attr) ? changed_attributes[attr] : __send__(attr)
end
# Restore all previous data of the provided attributes.
def restore_attributes(attributes = changed)
attributes.each { |attr| restore_attribute! attr }
end
private
def changes_include?(attr_name)
attributes_changed_by_setter.include?(attr_name)
end
# Removes current changes and makes them accessible through +previous_changes+.
def changes_applied # :doc:
@previously_changed = changes
@changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
end
# Clear all dirty data: current changes and previous changes.
def clear_changes_information # :doc:
@previously_changed = ActiveSupport::HashWithIndifferentAccess.new
@changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
end
# Handle <tt>*_change</tt> for +method_missing+.
def attribute_change(attr)
[changed_attributes[attr], __send__(attr)] if attribute_changed?(attr)
end
# Handle <tt>*_will_change!</tt> for +method_missing+.
def attribute_will_change!(attr)
return if attribute_changed?(attr)
begin
value = __send__(attr)
value = value.duplicable? ? value.clone : value
rescue TypeError, NoMethodError
end
set_attribute_was(attr, value)
end
# Handle <tt>restore_*!</tt> for +method_missing+.
def restore_attribute!(attr)
if attribute_changed?(attr)
__send__("#{attr}=", changed_attributes[attr])
clear_attribute_changes([attr])
end
end
# This is necessary because `changed_attributes` might be overridden in
# other implemntations (e.g. in `ActiveRecord`)
alias_method :attributes_changed_by_setter, :changed_attributes # :nodoc:
# Force an attribute to have a particular "before" value
def set_attribute_was(attr, old_value)
attributes_changed_by_setter[attr] = old_value
end
# Remove changes information for the provided attributes.
def clear_attribute_changes(attributes) # :doc:
attributes_changed_by_setter.except!(*attributes)
end
end
end
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