Finding the Public Interface

Finding and defining public interfaces is an art. It presents a design challenge because there are no cut-and-dried rules. There are many ways to create “good enough” interfaces and the costs of a “not good enough” interface may not be obvious for a while, making it difficult to learn from mistakes.

The design goal, as always, is to retain maximum future flexibility while writing only enough code to meet today’s requirements. Good public interfaces reduce the cost of unanticipated change; bad public interfaces raise it.