module ActiveModel::Dirty
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. -
Call
changes_applied
after the changes are persisted. -
Call
reset_changes
when 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"]
Public Instance Methods
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 118 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 109 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 148 def changed_attributes @changed_attributes ||= ActiveSupport::HashWithIndifferentAccess.new 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 128 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 138 def previous_changes @previously_changed ||= ActiveSupport::HashWithIndifferentAccess.new end
Private Instance Methods
Handle *_change
for method_missing
.
# File lib/active_model/dirty.rb, line 180 def attribute_change(attr) [changed_attributes[attr], __send__(attr)] if attribute_changed?(attr) end
Handle *_will_change!
for method_missing
.
# File lib/active_model/dirty.rb, line 185 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
Removes current changes and makes them accessible through
previous_changes
.
# File lib/active_model/dirty.rb, line 168 def changes_applied @previously_changed = changes @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new end
Handle reset_*!
for method_missing
.
# File lib/active_model/dirty.rb, line 198 def reset_attribute!(attr) if attribute_changed?(attr) __send__("#{attr}=", changed_attributes[attr]) changed_attributes.delete(attr) end end
Removes all dirty data: current changes and previous changes
# File lib/active_model/dirty.rb, line 174 def reset_changes @previously_changed = ActiveSupport::HashWithIndifferentAccess.new @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new end