Why are Private Pure Virtual Functions Used in C ?

Private Pure Virtual Functions: Purpose and Implementation

When encountering private pure virtual functions, it's common to wonder how derived classes can access and reimplement them.

Virtual Accessibility and Reimplementation

Contrary to what you might assume, private virtual functions are accessible to derived classes. Methods of derived classes cannot call virtual functions from the base class, but they can override and provide their own implementations.

Reasons for Using Private Pure Virtual Functions

This idiom separates the specification of the interface from the specification of the customizable implementation behavior. It allows for a clear and flexible interface that can be extended by derived classes.

The "PONV POV" Idiom

The code snippet you provided adheres to the "Public Overloaded Non-Virtuals Call Protected Non-Overloaded Virtuals" (PONV POV) idiom. Here, public overloaded non-virtual functions call non-public, non-overloaded virtual functions.

Hiding Rule Management

This idiom helps manage the hiding rule in C . If the virtual functions were overloaded and public, an issue could arise when trying to override specific implementations in derived classes. The using declaration would be necessary to prevent the hiding of base class members.

By using the PONV POV idiom with private virtual functions, derived classes can simply override the desired implementations without worrying about hiding issues.

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