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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
108:     def changed
109:       changed_attributes.keys
110:     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
100:     def changed?
101:       changed_attributes.any?
102:     end
changed_attributes() click to toggle source

Map of change attr => original value.

     # File lib/active_model/dirty.rb, line 130
130:     def changed_attributes
131:       @changed_attributes ||= {}
132:     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
116:     def changes
117:       HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }]
118:     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
125:     def previous_changes
126:       @previously_changed
127:     end

Private Instance Methods

attribute_change(attr) click to toggle source

Handle *_change for method_missing.

     # File lib/active_model/dirty.rb, line 142
142:       def attribute_change(attr)
143:         [changed_attributes[attr], __send__(attr)] if attribute_changed?(attr)
144:       end
attribute_changed?(attr) click to toggle source

Handle *_changed? for method_missing.

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

Handle *_was for method_missing.

     # File lib/active_model/dirty.rb, line 147
147:       def attribute_was(attr)
148:         attribute_changed?(attr) ? changed_attributes[attr] : __send__(attr)
149:       end
attribute_will_change!(attr) click to toggle source

Handle *_will_change! for method_missing.

     # File lib/active_model/dirty.rb, line 152
152:       def attribute_will_change!(attr)
153:         begin
154:           value = __send__(attr)
155:           value = value.duplicable? ? value.clone : value
156:         rescue TypeError, NoMethodError
157:         end
158: 
159:         changed_attributes[attr] = value unless changed_attributes.include?(attr)
160:       end
reset_attribute!(attr) click to toggle source

Handle reset_*! for method_missing.

     # File lib/active_model/dirty.rb, line 163
163:       def reset_attribute!(attr)
164:         __send__("#{attr}=", changed_attributes[attr]) if attribute_changed?(attr)
165:       end

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