Dynamic polymorphism is a powerful concept in object-oriented programming that allows objects of different concrete classes to be treated as objects of a common base class. In C++, dynamic polymorphism is achieved using virtual functions and inheritance. However, the static nature of inheritance poses limitations to dynamically adding new subclasses at runtime.

Fortunately, C++ provides a feature called variadic templates, which can be leveraged to achieve dynamic polymorphism without the need for predefined subclasses. Variadic templates allow for the creation of generic functions and classes that can accept a variable number of arguments of different types.

Let’s explore a simple example to understand how to use variadic templates for dynamic polymorphism in C++.

#include <iostream>

class Base {
public:
    virtual void print() const = 0;
};

template<typename... Types>
class Printer : public Base {
public:
    Printer(Types... args) : arguments(std::forward<Types>(args)...) {}

    void print() const override {
        printImpl(arguments);
    }

private:
    template<typename T>
    void printImpl(T arg) const {
        std::cout << arg << std::endl;
    }

    template<typename T, typename... Rest>
    void printImpl(T arg, Rest... rest) const {
        std::cout << arg << ", ";
        printImpl(rest...);
    }

    std::tuple<Types...> arguments;
};

int main() {
    Printer<int, float, std::string> printer(42, 3.14f, "Hello, World!");
    printer.print();
    return 0;
}

In the above code, we define a base class Base with a pure virtual function print(). We then define a class template Printer that derives from Base and takes a variadic template parameter Types. The constructor of the Printer class takes a variable number of arguments of different types.

The Printer class implements the print() function by using a set of recursive helper functions printImpl(). The first printImpl() overload handles the case when there is only one argument, while the second overload handles the case when there are multiple arguments. Each overload prints the argument and recursively calls itself with the remaining arguments.

In the main() function, we create an instance of the Printer class with int, float, and std::string as the template arguments. We then call the print() function, which prints all the arguments sequentially.

By using variadic templates, we achieve dynamic polymorphism in C++ as the Printer class can accept any number of arguments of different types at runtime. This approach provides flexibility and eliminates the need for predefined subclasses.

#C++ #VariadicTemplates