override

Keyword: override

The override keyword in C++ is used in object-oriented programming to indicate that a member function in a derived class is intended to override a virtual function in a base class. This keyword is part of modern C++ (introduced in C++11) and serves as a way to improve code clarity, maintainability, and safety.

What Does override Do?

When you use the override keyword, the compiler checks that the function is indeed overriding a virtual function from the base class. If it is not, the compiler will generate an error. This helps prevent subtle bugs that can occur if you accidentally misspell a function name or mismatch the function signature.

Example without override

In this case, Display() in the Derived class is not overriding display() in the Base class due to the case difference in the function name. However, this will not produce any compiler errors, and the Base::display() function will be called instead of the intended Derived::Display(), leading to unexpected behavior.

Example With override (Safety Check)

In this example, if there were a mistake such as a misspelled function name or an incorrect signature, the compiler would catch the error because of the override keyword.

Benefits of Using override:

• Error Prevention: Helps prevent bugs by ensuring that the derived class function is indeed overriding a base class function.
• Code Clarity: Clearly indicates to anyone reading the code that a function is intended to override a base class function.
• Maintainability: Makes the code easier to maintain by reducing the risk of unintended behavior due to mismatches in function signatures.

Common Usage Scenarios:

• Polymorphism: When working with polymorphism, using override ensures that the correct function is called for derived objects.
• Refactoring: If you refactor base class functions, override helps ensure that you update all derived classes accordingly.
• Inheritance Chains: In complex inheritance chains, override can help track which functions are meant to be overridden at each level.

Summary

• Using the override keyword is a best practice in modern C++ programming. It enhances the safety and readability of your code, especially when dealing with inheritance and polymorphism. It should be used whenever you intend for a function in a derived class to override a virtual function in a base class.