Mastering Python Design Patterns

Use cases

By using the Chain of Responsibility pattern, we give a chance to a number of different objects to satisfy a specific request. This is useful when we don't know which object should satisfy a request in advance. An example is a purchase system. In purchase systems, there are many approval authorities. One approval authority might be able to approve orders up to a certain value, let's say $100. If the order is more than $100, the order is sent to the next approval authority in the chain that can approve orders up to $200, and so forth.

Another case where Chain of Responsibility is useful is when we know that more than one object might need to process a single request. This is what happens in an event-based programming. A single event such ...