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is_final template in C++
In this article we will be discussing the working, syntax and examples of std::is_final template in C++ STL.
is_final is a template which comes under the <type_traits> header file. This template is used to check whether the given type T is a final class or not.
What is a final class in C++?
When we declare a class with the final specifier then it is called as Final Class. Final class is a special kind of class which can’t be extended to create another class. In C++ to make a class as a final we make a class as a friend and then virtually inherit that class, to make that class nonextendable.
Example of a final class
class final_abc; //Class which is to be made final
class abc {
private:
abc(){cout<<"abc constructor";}
friend class final_abc;
};
class final_abc : virtual abc //made it final class. {
public:
final_abc(){cout<<"Final class constructor";}
};
class derive : public final_abc; //Error can't be extendedSyntax
template <class T> is_final;
Parameters
The template can have only parameter of type T, and check whether the given type is a final class type or not.
Return value
It returns a Boolean value, true if the given type is a final class, and false if the given type is not a final class.
Example
Input: class final_abc;
class abc { friend class final_abc; };
class final_abc : virtual abc{ };
is_final<abc>::value;
Output: False
Input: class final_abc;
class abc
{ friend class final_abc; };
class final_abc : virtual abc{ };
is_final<final_abc>::value;
Output: TrueExample
#include <iostream>
#include <type_traits>
using namespace std;
class TP {
//Same if it will be a structure instead of a class
};
class T_P final {
//Same if it will be a structure instead of a class
};
int main() {
cout << boolalpha;
cout << "Using is_final";
cout << "\nTutorials Point: "<<is_final<TP>::value;
cout << "\nT_P Final: "<<is_final<T_P>::value;
cout << "\ncheck for char: "<<is_final<int>::value;
return 0;
}Output
If we run the above code it will generate the following output −
Using is_final Tutorials Point: false T_P Final: true check for char: false
Example
#include <iostream>
#include <type_traits>
using namespace std;
union TP {
//Union
};
union T_P final {
//Union
};
int main() {
cout << boolalpha;
cout << "Using is_final";
cout << "\nTutorials Point: "<<is_final<TP>::value;
cout << "\nT_P Final: "<<is_final<T_P>::value;
cout << "\ncheck for char: "<<is_final<int>::value;
return 0;
}Output
If we run the above code it will generate the following output −
Using is_final Tutorials Point: false T_P Final: true check for char: false
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