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"]
# File lib/active_model/dirty.rb, line 111 def changed changed_attributes.keys end
Returns true
if any attribute have unsaved changes,
false
otherwise.
person.changed? # => false person.name = 'bob' person.changed? # => true
# File lib/active_model/dirty.rb, line 102 def changed? changed_attributes.present? end
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"}
# File lib/active_model/dirty.rb, line 141 def changed_attributes @changed_attributes ||= {} end
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"] }
# File lib/active_model/dirty.rb, line 121 def changes ActiveSupport::HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }] end
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"]}
# File lib/active_model/dirty.rb, line 131 def previous_changes @previously_changed end
Handle *_change
for method_missing
.
# File lib/active_model/dirty.rb, line 153 def attribute_change(attr) [changed_attributes[attr], __send__(attr)] if attribute_changed?(attr) end
Handle *_changed?
for method_missing
.
# File lib/active_model/dirty.rb, line 148 def attribute_changed?(attr) changed_attributes.include?(attr) end
Handle *_was
for method_missing
.
# File lib/active_model/dirty.rb, line 158 def attribute_was(attr) attribute_changed?(attr) ? changed_attributes[attr] : __send__(attr) end
Handle *_will_change!
for method_missing
.
# File lib/active_model/dirty.rb, line 163 def attribute_will_change!(attr) return if attribute_changed?(attr) begin value = __send__(attr) value = value.duplicable? ? value.clone : value rescue TypeError, NoMethodError end changed_attributes[attr] = value end
Handle reset_*!
for method_missing
.
# File lib/active_model/dirty.rb, line 176 def reset_attribute!(attr) if attribute_changed?(attr) __send__("#{attr}=", changed_attributes[attr]) changed_attributes.delete(attr) end end