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. -
Call
changes_applied
after the changes are persisted. -
Call
clear_changes_information
when you want to reset the changes information. -
Call
restore_attributes
when you want to restore previous data.
A minimal implementation could be:
class Person
include ActiveModel::Dirty
define_attribute_methods :name
def initialize
@name = nil
end
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: nil, to: "Bob") # => true
person.name_was # => nil
person.name_change # => [nil, "Bob"]
person.name = 'Bill'
person.name_change # => [nil, "Bill"]
Save the changes:
person.save
person.changed? # => false
person.name_changed? # => false
Reset the changes:
person.previous_changes # => {"name" => [nil, "Bill"]}
person.name_previously_changed? # => true
person.name_previously_changed?(from: nil, to: "Bill") # => true
person.name_previous_change # => [nil, "Bill"]
person.name_previously_was # => nil
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"]
- C
- P
- R
Instance Public methods
changed() Link
Returns an array with the name of the attributes with unsaved changes.
person.changed # => []
person.name = 'bob'
person.changed # => ["name"]
changed?() Link
Returns true
if any of the attributes has unsaved changes, false
otherwise.
person.changed? # => false
person.name = 'bob'
person.changed? # => true
changed_attributes() Link
Returns a hash of the attributes with unsaved changes indicating their original values like attr => original value
.
person.name # => "bob"
person.name = 'robert'
person.changed_attributes # => {"name" => "bob"}
changes() Link
Returns a hash of changed attributes indicating their original and new values like attr => [original value, new value]
.
person.changes # => {}
person.name = 'bob'
person.changes # => { "name" => ["bill", "bob"] }
changes_applied() Link
Clears dirty data and moves changes
to previous_changes
and mutations_from_database
to mutations_before_last_save
respectively.
clear_attribute_changes(attr_names) Link
clear_changes_information() Link
Clears all dirty data: current changes and previous changes.
previous_changes() Link
Returns a hash of attributes that were changed before the model was saved.
person.name # => "bob"
person.name = 'robert'
person.save
person.previous_changes # => {"name" => ["bob", "robert"]}