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']
# File 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
List of attributes with unsaved changes.
person.changed # => [] person.name = 'bob' person.changed # => ['name']
# File lib/active_record/dirty.rb, line 65 def changed changed_attributes.keys end
Do any attributes have unsaved changes?
person.changed? # => false person.name = 'bob' person.changed? # => true
# File lib/active_record/dirty.rb, line 57 def changed? !changed_attributes.empty? end
Map of changed attrs => [original value, new value].
person.changes # => {} person.name = 'bob' person.changes # => { 'name' => ['bill', 'bob'] }
# File lib/active_record/dirty.rb, line 73 def changes changed.inject({}) { |h, attr| h[attr] = attribute_change(attr); h } end
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