module ActiveRecord class Attribute # :nodoc: class << self def from_database(name, value, type) FromDatabase.new(name, value, type) end def from_user(name, value, type, original_attribute = nil) FromUser.new(name, value, type, original_attribute) end def with_cast_value(name, value, type) WithCastValue.new(name, value, type) end def null(name) Null.new(name) end def uninitialized(name, type) Uninitialized.new(name, type) end end attr_reader :name, :value_before_type_cast, :type # This method should not be called directly. # Use #from_database or #from_user def initialize(name, value_before_type_cast, type, original_attribute = nil) @name = name @value_before_type_cast = value_before_type_cast @type = type @original_attribute = original_attribute 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 original_value if assigned? original_attribute.original_value else type_cast(value_before_type_cast) end end def value_for_database type.serialize(value) end def changed? changed_from_assignment? || changed_in_place? end def changed_in_place? has_been_read? && type.changed_in_place?(original_value_for_database, value) end def forgetting_assignment with_value_from_database(value_for_database) end def with_value_from_user(value) type.assert_valid_value(value) self.class.from_user(name, value, type, self) end def with_value_from_database(value) self.class.from_database(name, value, type) end def with_cast_value(value) self.class.with_cast_value(name, value, type) end def with_type(type) self.class.new(name, value_before_type_cast, type, original_attribute) end def type_cast(*) raise NotImplementedError end def initialized? true end def came_from_user? false end def has_been_read? defined?(@value) end def ==(other) self.class == other.class && name == other.name && value_before_type_cast == other.value_before_type_cast && type == other.type end alias eql? == def hash [self.class, name, value_before_type_cast, type].hash end protected attr_reader :original_attribute alias_method :assigned?, :original_attribute def initialize_dup(other) if defined?(@value) && @value.duplicable? @value = @value.dup end end def changed_from_assignment? assigned? && type.changed?(original_value, value, value_before_type_cast) end def original_value_for_database if assigned? original_attribute.original_value_for_database else _original_value_for_database end end def _original_value_for_database value_for_database end class FromDatabase < Attribute # :nodoc: def type_cast(value) type.deserialize(value) end def _original_value_for_database value_before_type_cast end end class FromUser < Attribute # :nodoc: def type_cast(value) type.cast(value) end def came_from_user? true end end class WithCastValue < Attribute # :nodoc: def type_cast(value) value end def changed_in_place_from?(old_value) false end end class Null < Attribute # :nodoc: def initialize(name) super(name, nil, Type::Value.new) end def type_cast(*) nil end def with_type(type) self.class.with_cast_value(name, nil, type) end def with_value_from_database(value) raise ActiveModel::MissingAttributeError, "can't write unknown attribute `#{name}`" end alias_method :with_value_from_user, :with_value_from_database end class Uninitialized < Attribute # :nodoc: def initialize(name, type) super(name, nil, type) end def value if block_given? yield name end end def value_for_database end def initialized? false end end private_constant :FromDatabase, :FromUser, :Null, :Uninitialized, :WithCastValue end end