Flyweight(Chapter 21 of Pro Objective-C Design Patterns for iOS)

You’d naturally think about using it when all of the following are true:

􀀁 Your app uses a lot of objects.

􀀁 Keeping objects in memory can affect memory performance.

􀀁 Most of the object’s unique state (extrinsic state) can be externalized and lightweight.

􀀁 Relatively few shared objects can replace the original bunch of objects after the objects’ extrinsic state is removed.

􀀁 Your app doesn’t depend on object identity since shared objects cannot have unique identities.