Revision Notes/Design Patterns
Field Entry - Design Patterns
Chain of Responsibility
Passes a request along a chain of handlers; each handler either processes it or passes it to the next one in the chain.
Field Note - Real-world Analogy
“Customer support escalation. You call a helpline. The first agent (Level 1 support) handles simple questions. If they can't solve it, they pass you to Level 2 support. Level 2 passes to Level 3 specialist if needed. Each handler processes what it can and escalates the rest.”
Field Observations - Key Topics Covered
The problem: a request might need to go through multiple checks or steps, but you don't want the sender to know about all of them. For example, an HTTP request might need authentication, then rate limiting, then input validation, then permission checks — all before reaching the actual handler.
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