The chain of responsibility design pattern

The chain of responsibility is a design pattern where the sender of a request is decoupled from its receiver. This way, it makes it possible for multiple objects to handle the request and to keep logic nicely separated. The receivers form a chain where they pass the request and, if possible, they process it, and if not, they pass it to the next receiver. There are variations where a handler might dispatch the request to multiple other handlers at the same time. This somehow reminds us of function composition, which in Scala can be achieved using the stackable traits design pattern.