Flyweight

Origin:

GoF 95

Reason:

Many instances of a class contain unnecessarily duplicated information.

Synopsis:

Define a single object, the Flyweight, for all the duplicated copies. This instance is shared by the Client.

Example:

A wordprocessor represents glyphs by character code, font, size, color, etc. A paragraph should share equal gliphs, not duplicate them.

Solution:

AbstractFlyweight	Superclass or interface of all Flyweight objects.	glyph
SharedConcreteFlyweight	Class of sharable flyweight objects. Stores intrinsic state.	context independent characters
UnsharedConcreteFlyweight	Class of unsharable flyweight objects. Stores extrinsic state.	context dependent characters
FlyweightFactory	Manager of the flyweight objects.
Client	References a flyweight objects. Computes or stores extrinsic state.	paragraph or document