Function pointer to template class member function

问题:

I have a templated class defined (in part) as

template <class T> MyClass
{
public:
   void DoSomething(){}
};

If I want to call DoSomething from another class, but be able to do this for multiple 'T' types in the same place, I am stuck for an idea as method functions pointers are uniquely constrained to the class type. Of course, each MyClass is a different type, so I can not store function pointers to MyClassDoSomething() in a 'polymorphic' way.

My use-case is I want to store, in a holding class, a vector of function pointers to 'DoSomething' such that I can issue a call to all stored classes from one place.

Has anyone any suggestions?

回答1:

Ok, so the functor solution doesn't work as you need. Perhaps you should have your template class inherit from a common base "Interface" class. And then you use a vector of those.

Something like this:

class Base { 
public:
  virtual ~Base(){}
  virtual void DoSomething() = 0;
}

template <class T> class MyClass : public Base {
public:
    void DoSomething(){}
};

std::vector<Base *> objects;
objects.push_back(new MyClass<int>);
objects.push_back(new MyClass<char>);

回答2:

You know, that is just what I needed to do. Bizzarly I had discounted it as a solution valid for my usecase early on, for reasons that now escape me. I think I was blinded by some metaprogramming stuff I'm doing in the same place for compile-time dispatch (i.e. confusing compile time and runtime in my addled brain).

Thanks for the jolts!