C++ passing method pointer as template argument

Question

I have a caller function like this:

template
void CallMethod(T *object){
    (object->*method)(args);
}
         


        

Answer 1

It looks like you're trying to implement an interface via templates. It might be possible, but wouldn't it be nicer to have a base class with a virtual function, and use a base class pointer to access the virtual function via a simple function call?

Header:

class AbstractBase
{
public:
    virtual void func() = 0;
}
class SubClass : public AbstractBase
{
public:
    void func();
}

Source file:

void SubClass::func()
{
    std::cout << "Virtual function called.\n";
}

Example usage:

int main()
{
    AbstractBase* base;
    base = new SubClass();
    base->func(); // virtual function call through base pointer will use SubClass's implementation
    return 0;
}

You can store a vector of pointers (or smart pointers if you use boost or C++0x) which you can loop through and use this to do all kinds of SubClass dependent stuff.

Alternatively, use boost::function or std::function (C++0x) which is an object containing the member function in question and pass that as a template parameter, using the object instance as a first argument. Which comes down to a workaround of the above.

UPDATE: Seeing that you need a plain C function pointer, there are some tricks that might imapct runtime performance in c++0x or boost: bind, function::target and so forth...

You will need this to get a function pointer out of a std/boost::function, and this to bind the first argument to an object. bind acts at runtime, so maybe a template would be better in this case...