Use multiple inheritance to represent multiple distinct interfaces

Reason

Not all classes will necessarily support all interfaces, and not all callers will necessarily want to deal with all operations. Especially to break apart monolithic interfaces into "aspects" of behavior supported by a given derived class.

Example

class iostream : public istream, public ostream {   // very simplified
    // ...
};

istream provides the interface to input operations; ostream provides the interface to output operations. iostream provides the union of the istream and ostream interfaces and the synchronization needed to allow both on a single stream.

Note

This is a very common use of inheritance because the need for multiple different interfaces to an implementation is common and such interfaces are often not easily or naturally organized into a single-rooted hierarchy.

Note

Such interfaces are typically abstract classes.

Enforcement

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