Static Class Structure

• Client
  • Refers to the Flyweight interface.
  • Maintains a reference (flyweight) to a Flyweight object.
  • Passes in extrinsic state when invoking a Flyweight operation (operation(extrinsicState)).
  • Requests a Flyweight object from the FlyweightFactory (by invoking getFlyweight(key)).
• Flyweight
  • Defines an interface (operation(extrinsicState)) through which extrinsic (variant) state can be passed in.
• Flyweight1,…
  • Implement the Flyweight interface.
  • Store intrinsic (invariant) state that can be shared.
• UnsharedFlyweight1,…
  • Implement the Flyweight interface but are not shared.
• FlyweightFactory
  • Maintains a container of shared Flyweight objects (flyweight pool).
  • Creates a Flyweight object if it doesn't exist and shares (reuses) an existing one.

Dynamic Object Collaboration

• In this sample scenario, a Client object shares a Flyweight1 object by requesting it from a FlyweightFactory object.
• The interaction starts with the Client that calls getFlyweight(key) on the FlyweightFactory.
• Because the flyweight does not already exist, the FlyweightFactory creates a Flyweight1 object and returns it to the Client.
• The Client calls operation(extrinsicState) on the returned Flyweight1 object by passing in the extrinsic state.
• Thereafter, the Client again calls getFlyweight(key) on the FlyweightFactory.
• Because the flyweight already exists, the FlyweightFactory shares (reuses) the Flyweight1 object.
• The Client calls operation(extrinsicState) on the returned Flyweight1 object.
• See also Sample Code / Example 1.