Track unsaved attribute changes.

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'] }

Before modifying an attribute in-place:

person.name_will_change!
person.name << 'by'
person.name_change    # => ['uncle bob', 'uncle bobby']
Namespace
Methods
C
I
Constants
DIRTY_SUFFIXES = ['_changed?', '_change', '_will_change!', '_was']
 
Class Public methods
included(base)
# File activerecord/lib/active_record/dirty.rb, line 39
def self.included(base)
  base.attribute_method_suffix *DIRTY_SUFFIXES
  base.alias_method_chain :write_attribute, :dirty
  base.alias_method_chain :save,            :dirty
  base.alias_method_chain :save!,           :dirty
  base.alias_method_chain :update,          :dirty
  base.alias_method_chain :reload,          :dirty
  base.class_attribute :partial_updates
  base.partial_updates = true
  base.send(:extend, ClassMethods)
end
Instance Public methods
changed()

List of attributes with unsaved changes.

person.changed # => []
person.name = 'bob'
person.changed # => ['name']
# File activerecord/lib/active_record/dirty.rb, line 65
def changed
  changed_attributes.keys
end
changed?()

Do any attributes have unsaved changes?

person.changed? # => false
person.name = 'bob'
person.changed? # => true
# File activerecord/lib/active_record/dirty.rb, line 57
def changed?
  !changed_attributes.empty?
end
changes()

Map of changed attrs => [original value, new value].

person.changes # => {}
person.name = 'bob'
person.changes # => { 'name' => ['bill', 'bob'] }
# File activerecord/lib/active_record/dirty.rb, line 73
def changes
  changed.inject({}) { |h, attr| h[attr] = attribute_change(attr); h }
end