比较C ++中的类类型

Question

I need to compare two classes, more exactly their types. I wrote the following code:

class Base {};
class Derived : public Base {};

class Engine
{
public:
    template <class T>
    T addComponent();
};

template <class T>
T Engine::addComponent()
{
    Base* isRight = dynamic_cast<Base*>(T);
    if (!isRight)
        throw("Error!");

    return T();
}

And then I call it

int main()
{
    Engine engine = Engine();
    Derived derived = engine.addComponent<Derived>();
}

Well, I know, dynamic_cast works only on instances of the class. I hope you know a solution.

Answer 1

I believe you're looking for std::is_base_of . And since it's a static thing, you can do this check entirely at compile time:

template <class T>
T Engine::addComponent()
{
    static_assert(std::is_base_of<Base, T>::value, "T doesn't derive from Base!");

    return T();
}