Interfaces done right

Interfaces are one of the backbones of modern, object-oriented design. You need to use instances of different classes which share similarities in a uniform way? Use interfaces. You cannot easily test a class because it depends on details of other classes? Make your class depend on interfaces instead and introduce mock objects. You have a class with a single responsibility, but a respectable amount of methods which are intended for different types of callers? Make your class implement several interfaces, and let different callers refer to the ones which suit their needs.

As you can see, interfaces used correctly are pretty powerful tools, and many programming languages such as Java and C# provide dedicated interface keywords. This is not the case for C++. This article explains how to write clean and safe interfaces for your classes.

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