Active Model Dirty
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.
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! unless val == @name @name = val end def save @previously_changed = changes @changed_attributes.clear end end
A newly instantiated object is unchanged:
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_will_change! person.name_change # => ["Bill", "Bill"] person.name << 'y' person.name_change # => ["Bill", "Billy"]