Design Patterns
Chain of Responsibility
In the worst case, a request travels through all n handlers. So handling one request takes O(n) time — the time can grow with the number of handlers.
The idea, in plain English
Chain of responsibility passes a request down a line of people until someone can handle it. Think of an expense request going to your manager first. If it's too big, it moves up to the director, then the VP. Each person either deals with it or bumps it up the chain.
How it works
- 1You line up a series of handler objects. Each one knows which handler comes next.
- 2You hand the request to the first handler in line.
- 3Each handler asks 'can I handle this?' If yes, it deals with it. If no, it passes the request to the next handler in line.
When you'd use it
Use this when several objects might handle a request, but you don't know which one in advance. Examples: approval chains, event handling, or support-ticket escalation.
Common beginner mistakes
- Always set the 'next' handler, or a request can silently get dropped instead of passing along.
- Don't build a chain so long that requests take forever to reach the handler that can actually deal with them.
Try it — edit and run
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Manager approved $50
Director approved $500
VP approved $5000Not sure this is the right topic? See the learning paths → or where this leads →