Can Private Pure Virtual Functions be Overridden in Derived Classes?

Private Pure Virtual Functions: Purpose and Implementation

The use of private pure virtual functions, as seen in the provided code snippet, can raise questions about accessibility and reimplementation. This article aims to clarify these aspects.

Accessibility and Reimplementation of Private Pure Virtual Functions

Unlike the common misconception, private virtual functions can be overridden in derived classes. While methods in derived classes cannot directly call virtual functions from the base class, they possess the ability to provide their own implementation. This allows for a separation between the interface specification in the base class and the customizable behavior implementation in derived classes.

Overloaded Non-Virtual Functions and Private Virtual Functions

The code snippet demonstrates a common idiom: public overloaded non-virtual functions calling private non-overloaded virtual functions. This technique helps manage the C hiding rule.

Hiding Rule and the Overloaded Interface

Without private pure virtual functions, if the virtual functions in the Engine class constituted an overloaded interface, preventing the hiding of the second overload in a derived class would require an explicit "using" declaration. This can lead to issues when calling the base class function with arguments that are convertible to other overloads.

Benefits of Private Pure Virtual Functions

By making the virtual implementation private in combination with overloaded non-virtual functions, authors of derived classes can focus purely on providing the desired customization without having to worry about naming conflicts or hiding issues.

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