Is it possible to clone a polymorphic object without manually adding overridden clone method into each derived class in C++?

Question

The typical pattern when you want to copy a polymorphic class is adding a virtual clone method and implement it in each derived class like this:

Base* Derive         


        

Answer 1

You could use CRTP to add an additional layer between your derived class and base that implements your cloning method.

struct Base {
    virtual ~Base() = default;
    virtual Base* clone() = 0;
};

template 
struct Base_with_clone : Base {
    Base* clone() {
        return new T(*this);
    }
};

struct Derived : Base_with_clone {};