Adapter (aka Wrapper)

Intent

• Convert the interface of a class into another interface clients expect.

• Adapter lets classes work together that couldn't otherwise because of incompatible interfaces.

Problem

• How can a class be reused that does not have the interface clients require?

• How can classes that have incompatible interfaces work together?

Solution

• Define a separate adapter class that converts the incompatible interface of a class adaptee into another interface target clients require.

• Work through an adapter to work with (reuse) classes that do not have the required interface.

Advantages

✅ Supports reusability.

Note

• There are two ways of implementing the adapter pattern

  1. Object Adapter

     • In this adapter pattern, the adapter contains an instance of the class it wraps. In this situation, the adapter makes calls to the instance of the wrapped object.

     • Uses object composition to implement a Target interface in terms of (by delegating to) an Adaptee object.

  2. Class Adapter

     • This adapter pattern uses multiple polymorphic interfaces implementing or inheriting both the interface that is expected and the interface that is pre-existing.

     • Uses inheritance to implement a Target interface in terms of (by inheriting from) an Adaptee class.