Object Recursion

By: B. Woolf

Summary: Handle a request over a structure by delegating it polymorphically. A request can be decomposed repeatedly into smaller parts.

Pattern: Object Recursion

Handle a request over a structure by delegating it polymorphically. A request can be decomposed repeatedly into smaller parts. An initiator makes a request of a handler. The handler does what it needs to do, then passes the request on to its successor--another handler--and returns a result based on the successor's result.

• Chain of Responsibility [Gamma+95] uses this pattern.
• In Interpreter [Gamma+95], the interpret() message traverses an abstract syntax tree using this pattern.
• Iterator [Gamma+95] on a branching structure can be implemented recursively. If the terminating points are objects, then this is Object Recursion.
• Proxy [Gamma+95] is an example of one-level-deep Object Recursion.