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::Dirtyin your object. -
Call
define_attribute_methodspassing each method you want to track. -
Call
attr_name_will_change!before each change to the tracked attribute. -
Call
changes_appliedafter the changes are persisted. -
Call
reset_changeswhen you want to reset the changes information.
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!
reset_changes
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 # => {}
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 ActiveModel can't
track changes to in-place attributes.
person.name_will_change! person.name_change # => ["Bill", "Bill"] person.name << 'y' person.name_change # => ["Bill", "Billy"]