What is the purpose of the Chain of Responsibility design pattern and how is it implemented?

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What is the purpose of the Chain of Responsibility design pattern and how is it implemented?

The purpose of the Chain of Responsibility design pattern is to decouple the sender of a request from its receiver by allowing multiple objects to handle the request. This pattern promotes loose coupling and flexibility in the system, as it allows different objects to handle the request dynamically without the sender needing to know the exact receiver.

The implementation of the Chain of Responsibility pattern involves creating a chain of objects, where each object in the chain has a reference to the next object in the chain. When a request is made, it is passed through the chain until an object is found that can handle the request. Each object in the chain has the option to handle the request or pass it to the next object in the chain.

To implement the Chain of Responsibility pattern, the following components are typically involved:

1. Handler Interface/Abstract Class: This defines the common interface or abstract class that all handlers in the chain must implement. It usually includes a method to handle the request and a reference to the next handler in the chain.

2. Concrete Handlers: These are the actual objects that make up the chain. Each concrete handler implements the handler interface/abstract class and provides its own implementation of the handle request method. It also has a reference to the next handler in the chain.

3. Client: The client is responsible for creating the chain of handlers and initiating the request. It sends the request to the first handler in the chain, and the request is then passed through the chain until it is handled or reaches the end of the chain.

The implementation of the Chain of Responsibility pattern allows for dynamic and flexible handling of requests. It enables the addition or removal of handlers from the chain without affecting the client's code. Additionally, it promotes the principle of single responsibility, as each handler in the chain is responsible for handling a specific type of request.