Function overriding is redefinition of base class function in its derived class with same signature i.e return type and parameters.
But there may be situations when a programmer makes a mistake while overriding that function. So, to keep track of such an error, C++11 has come up with the keyword override. It will make the compiler to check the base class to see if there is a virtual function with this exact signature. And if there is not, the compiler will show an error.
This will be more clear from the following example:
Explanation: Here the user intended to override the function func() in the derived class but did a silly mistake and redefined the function with different signature. Which was not detected by the compiler. However, the program is not actually what the user wanted. So, to get rid of such silly mistake to be in safe side, override keyword can be used.
Below is a C++ example to show the use of override keyword in C++.
prog.cpp:17:7: error: 'void derived::func(int)' marked 'override', but does not override void func(int a) override ^
In short, it serves the following functions. It helps to check if :
- There is a method with the same name in the parent class.
- The method in the parent class is declared as “virtual” which means it was intended to be rewritten.
- The method in the parent class has the same signature as the method in the subclass.
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