Structural Design Pattern: Flyweight Design pattern

Define Flyweight Design Pattern

The flyweight pattern is used when there is a need to construct a huge number of objects with essentially identical properties and some common data. A few shared objects can replace many non-shared ones.

Concepts of Flyweight Design Pattern

The flyweight pattern makes use of both intrinsic and extrinsic data.

• Intrinsic Data: The shared flyweight objects' characteristics store intrinsic data. This information is stateless and normally unchanging; if something changes, it will be reflected in all objects that reference the flyweight.
• Extrinsic Data: Extrinsic data is computed during runtime and stored outside of a flyweight object. As a result, it has the potential to be meaningful.

Examples of Flyweight Design Patterns

Examples of flyweight patterns are:

• Game Objects
• Social Media Posts
• List of Users

Flyweight Design Pattern with UML diagram

The classes, interfaces, and objects in the above UML class diagram are listed below:

• Flyweight: This interface defines the properties of flyweight objects.
• ConcreteFlyweight: This class inherits from the Flyweight class.
• UnsharedFlyweight: This class inherits from the Flyweight class and allows for information sharing; instances of concrete flyweight classes can be created that are not shared.
• FlyweightFactory: This class manages a set of pre-built flyweight objects. When the client invokes the GetFlyweight method, it determines whether the requested flyweight object exists in the collection. If it's found, it's returned; otherwise, a new object is generated, added to the collection, and returned.

When to use a Flyweight Design Pattern?

• The flyweight design pattern is excellent for creating a huge number of similar products with high storage costs.
• A few shared objects can replace many non-shared ones.
• The majority of the state can be stored on disc or calculated during runtime.