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"]}