The Inverse Extension Design Pattern

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In object-oriented programming, it is common for a child class’s method to extend the parent class’s method. However, inverting this pattern is useful as well. Although most object-oriented programming languages support the former, I have never encountered one that supported the latter. Nonetheless, it is possible to implement this pattern without explicit support from the programming language, just as it was possible to implement inheritance in C before C++ was created.

Link: Linux Journal