Adapter

The Adapter pattern is a structural design pattern that allows objects with incompatible interfaces to work together. It acts as a bridge between two incompatible interfaces by converting the interface of a class into another interface that a client expects.

In layman’s terms, imagine you have a plug that doesn’t fit into a socket. An adapter is like a device that you can plug into the socket, and then you can plug your plug into the adapter. This way, the plug and socket can work together even though they were not designed to be compatible.

UML Diagram

+-----------------+      +------------------+
|    Client       |      |  Target          |
|-----------------|      |------------------|
| request()       |      | request()        |
+-----------------+      +------------------+
          |                      ^
          |                      |
          v                      |
+-----------------+      +------------------+
|    Adapter      |      |  Adaptee         |
|-----------------|      |------------------|
| request()       |----->| specificRequest()|
+-----------------+      +------------------+

--- Java Example ---

// Target interface
public interface Target {
    void request();
}

// Adaptee class
public class Adaptee {
    public void specificRequest() {
        System.out.println("Called specificRequest()");
    }
}

// Adapter class
public class Adapter implements Target {
    private Adaptee adaptee;

    public Adapter(Adaptee adaptee) {
        this.adaptee = adaptee;
    }

    @Override
    public void request() {
        adaptee.specificRequest();
    }
}

// Client code
public class Client {
    public static void main(String[] args) {
        Adaptee adaptee = new Adaptee();
        Target target = new Adapter(adaptee);
        target.request();
    }
}

--- Python Example ---

 from typing import Protocol

 # Target interface
 class Target(Protocol):
     def request(self) -> None:
         pass

 # Adaptee class
 class Adaptee:
     def specific_request(self) -> None:
         print("Called specific_request()")

 # Adapter class
 class Adapter(Target):
     def __init__(self, adaptee: Adaptee) -> None:
         self.adaptee: Adaptee = adaptee

     def request(self) -> None:
         self.adaptee.specific_request()

 # Client code
 if __name__ == "__main__":
     adaptee = Adaptee()
     target: Target = Adapter(adaptee)
     target.request()