Chapter 15. Catalog


“Who's in charge here?”

This is a moderate-size example involving both refactoring and development. The goal is to demonstrate how we can use refactoring to explore design decisions and their consequences.


Imagine a store selling a variety of items. During a brief design session, we decide there are several classes of interest: Item (something for sale), Catalog (the set of all items), and Query (to find a specific set of items).

Catalog and Query must collaborate to search, but how that collaboration will occur needs to be decided. Imagine a fourth class, Interrogator. It has a method evaluate(catalog, query) that returns a list of items. This method encapsulates the decision about how to handle things.

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