Mastering Python Design Patterns - Second Edition

Summary

In this chapter, we covered the Chain of Responsibility design pattern. This pattern is useful to model requests and/or handle events when the number and type of handlers aren't known in advance. Examples of systems that fit well with Chain of Responsibility are event-based systems, purchase systems, and shipping systems.

In the Chain of Responsibility pattern, the sender has direct access to the first node of a chain. If the request cannot be satisfied by the first node, it forwards it to the next node. This continues until either the request is satisfied by a node or the whole chain is traversed. This design is used to achieve loose coupling between the sender and the receiver(s).

ATMs are an example of Chain of Responsibility. ...