module ActiveRecord class Attribute # :nodoc: class << self def from_database(value, type) FromDatabase.new(value, type) end def from_user(value, type) FromUser.new(value, type) end end attr_reader :value_before_type_cast, :type # This method should not be called directly. # Use #from_database or #from_user def initialize(value_before_type_cast, type) @value_before_type_cast = value_before_type_cast @type = type end def value # `defined?` is cheaper than `||=` when we get back falsy values @value = type_cast(value_before_type_cast) unless defined?(@value) @value end def value_for_database type.type_cast_for_database(value) end def changed_from?(old_value) type.changed?(old_value, value, value_before_type_cast) end def changed_in_place_from?(old_value) type.changed_in_place?(old_value, value) end def type_cast raise NotImplementedError end protected def initialize_dup(other) if defined?(@value) && @value.duplicable? @value = @value.dup end end class FromDatabase < Attribute def type_cast(value) type.type_cast_from_database(value) end end class FromUser < Attribute def type_cast(value) type.type_cast_from_user(value) end end class Null class << self attr_reader :value, :value_before_type_cast, :value_for_database def changed_from?(*) false end alias changed_in_place_from? changed_from? end end end end