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module ActiveModel
# <tt>ActiveModel::Dirty</tt> provides a way to track changes in your
# object in the same way as ActiveRecord does.
#
# The requirements to implement 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
#
# If you wish to also track previous changes on save or update, you need to add
#
# @previously_changed = changes
#
# inside of your save or update method.
#
# A minimal implementation could be:
#
# class Person
#
# include ActiveModel::Dirty
#
# define_attribute_methods [:name]
#
# def name
# @name
# end
#
# def name=(val)
# name_will_change!
# @name = val
# end
#
# def save
# @previously_changed = changes
# end
#
# end
#
# == Examples:
#
# 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_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
#
# 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'] }
#
# Resetting an attribute returns it to its original state:
# person.reset_name! # => 'Bill'
# person.changed? # => false
# person.name_changed? # => false
# person.name # => 'Bill'
#
# Before modifying an attribute in-place:
# person.name_will_change!
# 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 => 'reset_', :suffix => '!'
end
# Do any attributes have unsaved changes?
# person.changed? # => false
# person.name = 'bob'
# person.changed? # => true
def changed?
!changed_attributes.empty?
end
# List of attributes with unsaved changes.
# person.changed # => []
# person.name = 'bob'
# person.changed # => ['name']
def changed
changed_attributes.keys
end
# Map of changed attrs => [original value, new value].
# person.changes # => {}
# person.name = 'bob'
# person.changes # => { 'name' => ['bill', 'bob'] }
def changes
changed.inject({}) { |h, attr| h[attr] = attribute_change(attr); h }
end
# Map of attributes that were changed when the model was saved.
# person.name # => 'bob'
# person.name = 'robert'
# person.save
# person.previous_changes # => {'name' => ['bob, 'robert']}
def previous_changes
previously_changed_attributes
end
private
# Map of change <tt>attr => original value</tt>.
def changed_attributes
@changed_attributes ||= {}
end
# Map of fields that were changed when the model was saved
def previously_changed_attributes
@previously_changed || {}
end
# Handle <tt>*_changed?</tt> for +method_missing+.
def attribute_changed?(attr)
changed_attributes.include?(attr)
end
# Handle <tt>*_change</tt> for +method_missing+.
def attribute_change(attr)
[changed_attributes[attr], __send__(attr)] if attribute_changed?(attr)
end
# Handle <tt>*_was</tt> for +method_missing+.
def attribute_was(attr)
attribute_changed?(attr) ? changed_attributes[attr] : __send__(attr)
end
# Handle <tt>*_will_change!</tt> for +method_missing+.
def attribute_will_change!(attr)
begin
value = __send__(attr)
value = value.duplicable? ? value.clone : value
rescue TypeError, NoMethodError
end
changed_attributes[attr] = value
end
# Handle <tt>reset_*!</tt> for +method_missing+.
def reset_attribute!(attr)
__send__("#{attr}=", changed_attributes[attr]) if attribute_changed?(attr)
end
end
end
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