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.
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:
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"]}
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"]
Returns an array with the name of the attributes with unsaved changes.
person.changed # => [] person.name = 'bob' person.changed # => ["name"]
Returns true
if any attribute have unsaved changes,
false
otherwise.
person.changed? # => false person.name = 'bob' person.changed? # => true
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"}
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"] }
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"]}