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Design pattern: Chain of Responsibility

Description: "Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it."

This pattern can be used with both classes and prototypes.

In this sample implementation, we use prototypes and fixed successors in the chain of responsibility. But the successors could also easily be defined dynamically.

Print Logtalk, Prolog backend, and kernel versions (if running as a notebook):

%versions

Start by loading the design pattern sample implementation:

logtalk_load(design_patterns('behavioral/chain_of_responsibility/loader')).

Try some purchasing requests of varying amount:

manager::process_request(3500).

<!-- Manager will approve 3500 true. -->

manager::process_request(6500).

<!-- Director will approve 6500 true. -->

manager::process_request(11500).

<!-- Vice President will approve 11500 true. -->

manager::process_request(27000).

<!-- President will approve 27000 true. -->

manager::process_request(32000).

<!-- Request denied for 32000 false. -->