module ActiveRecord # 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'] module Dirty DIRTY_SUFFIXES = ['_changed?', '_change', '_will_change!', '_was'] 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.superclass_delegating_accessor :partial_updates base.partial_updates = true base.send(:extend, ClassMethods) end # Do any attributes have unsaved changes? # person.changed? # => false # person.name = 'bob' # person.changed? # => true def changed? !changed_attributes.empty? end # List of attributes with unsaved changes. # person.changed # => [] # person.name = 'bob' # person.changed # => ['name'] def changed changed_attributes.keys end # Map of changed attrs => [original value, new value]. # person.changes # => {} # person.name = 'bob' # person.changes # => { 'name' => ['bill', 'bob'] } def changes changed.inject({}) { |h, attr| h[attr] = attribute_change(attr); h } end # Attempts to +save+ the record and clears changed attributes if successful. def save_with_dirty(*args) #:nodoc: if status = save_without_dirty(*args) changed_attributes.clear end status end # Attempts to save! the record and clears changed attributes if successful. def save_with_dirty!(*args) #:nodoc: status = save_without_dirty!(*args) changed_attributes.clear status end # reload the record and clears changed attributes. def reload_with_dirty(*args) #:nodoc: record = reload_without_dirty(*args) changed_attributes.clear record end private # Map of change attr => original value. def changed_attributes @changed_attributes ||= {} end # Handle *_changed? for +method_missing+. def attribute_changed?(attr) changed_attributes.include?(attr) end # Handle *_change for +method_missing+. def attribute_change(attr) [changed_attributes[attr], __send__(attr)] if attribute_changed?(attr) end # Handle *_was for +method_missing+. def attribute_was(attr) attribute_changed?(attr) ? changed_attributes[attr] : __send__(attr) end # Handle *_will_change! for +method_missing+. def attribute_will_change!(attr) changed_attributes[attr] = clone_attribute_value(:read_attribute, attr) end # Wrap write_attribute to remember original attribute value. def write_attribute_with_dirty(attr, value) attr = attr.to_s # The attribute already has an unsaved change. if changed_attributes.include?(attr) old = changed_attributes[attr] changed_attributes.delete(attr) unless field_changed?(attr, old, value) else old = clone_attribute_value(:read_attribute, attr) changed_attributes[attr] = old if field_changed?(attr, old, value) end # Carry on. write_attribute_without_dirty(attr, value) end def update_with_dirty if partial_updates? # Serialized attributes should always be written in case they've been # changed in place. update_without_dirty(changed | (attributes.keys & self.class.serialized_attributes.keys)) else update_without_dirty end end def field_changed?(attr, old, value) if column = column_for_attribute(attr) if column.number? && column.null && (old.nil? || old == 0) && value.blank? # For nullable numeric columns, NULL gets stored in database for blank (i.e. '') values. # Hence we don't record it as a change if the value changes from nil to ''. # If an old value of 0 is set to '' we want this to get changed to nil as otherwise it'll # be typecast back to 0 (''.to_i => 0) value = nil else value = column.type_cast(value) end end old != value end module ClassMethods def self.extended(base) base.metaclass.alias_method_chain(:alias_attribute, :dirty) end def alias_attribute_with_dirty(new_name, old_name) alias_attribute_without_dirty(new_name, old_name) DIRTY_SUFFIXES.each do |suffix| module_eval <<-STR, __FILE__, __LINE__+1 def #{new_name}#{suffix}; self.#{old_name}#{suffix}; end # def subject_changed?; self.title_changed?; end STR end end end end end