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
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
Examples:¶ ↑
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 << 'y' person.name_change # => ['Bill', 'Billy']
Public Instance Methods
List of attributes with unsaved changes.
person.changed # => [] person.name = 'bob' person.changed # => ['name']
# File lib/active_model/dirty.rb, line 108 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 100 def changed? changed_attributes.any? end
Map of change attr => original value
.
# File lib/active_model/dirty.rb, line 130 def changed_attributes @changed_attributes ||= {} end
Map of changed attrs => [original value, new value].
person.changes # => {} person.name = 'bob' person.changes # => { 'name' => ['bill', 'bob'] }
# File lib/active_model/dirty.rb, line 116 def changes HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }] end
Map of attributes that were changed when 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 125 def previous_changes @previously_changed end
Private Instance Methods
Handle *_change
for method_missing
.
# File lib/active_model/dirty.rb, line 142 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 137 def attribute_changed?(attr) changed_attributes.include?(attr) end
Handle *_was
for method_missing
.
# File lib/active_model/dirty.rb, line 147 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 152 def attribute_will_change!(attr) begin value = __send__(attr) value = value.duplicable? ? value.clone : value rescue TypeError, NoMethodError end changed_attributes[attr] = value unless changed_attributes.include?(attr) end
Handle reset_*!
for method_missing
.
# File lib/active_model/dirty.rb, line 163 def reset_attribute!(attr) __send__("#{attr}=", changed_attributes[attr]) if attribute_changed?(attr) end