Flowdock
module
Importance_3
Ruby on Rails latest stable (v4.2.1) - 0 notes

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:

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!
    # get the values from the persistence layer

    clear_changes_information
  end

  def rollback!
    restore_attributes
  end
end

A newly instantiated Person object is unchanged:

person = Person.new
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 # => {}

Rollback the changes:

person.name = "Uncle Bob"
person.rollback!
person.name          # => "Bill"
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 Active Model can’t track changes to in-place attributes. Note that Active Record can detect in-place modifications automatically. You do not need to call +[attribute_name]_will_change!+ on Active Record models.

person.name_will_change!
person.name_change # => ["Bill", "Bill"]
person.name << 'y'
person.name_change # => ["Bill", "Billy"]
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