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:

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

changed() click to toggle source

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
changed?() click to toggle source

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
changed_attributes() click to toggle source

Map of change attr => original value.

# File lib/active_model/dirty.rb, line 130
def changed_attributes
  @changed_attributes ||= {}
end
changes() click to toggle source

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
previous_changes() click to toggle source

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

attribute_change(attr) click to toggle source

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
attribute_changed?(attr) click to toggle source

Handle *_changed? for method_missing.

# File lib/active_model/dirty.rb, line 137
def attribute_changed?(attr)
  changed_attributes.include?(attr)
end
attribute_was(attr) click to toggle source

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
attribute_will_change!(attr) click to toggle source

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
reset_attribute!(attr) click to toggle source

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