Pass class member function address to another member in initialization list

Question

Suppose that I have a class that accepts a function pointer in its constructor like this:

class IOControl
{
public:
    IOControl(void (*callback)(void));
};

And I have another class that I want to pass a non-static member address of it to above class constructor:

class Core
{
    public:
        Core();
    
    private:
        void some_callback();
        IOControl io;

};


Core::Core(): io(&Core::some_callback)
{

}

But I get this error:

no matching function for call to 'IOControl::IOControl(void (Core::*)())'

If I make both io and some_callback as static it would work fine but as a non-static member, I get the above error.

Also using Core::Core(): io(&(this->some_callback)) or Core::Core(): io(&some_callback) give me ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function... error.

pointers to free functions are not pointers to member functions. — 463035818_is_not_an_ai, Oct 13 '20 at 10:02
@idclev463035818 Do you mean `some_callback` is a free function? — Masoud Rahimi, Oct 13 '20 at 10:04
yes. Member function pointers are something entirely different, because they need an object to be called — 463035818_is_not_an_ai, Oct 13 '20 at 10:06
the error message already tells you, the parameter you try to pass is of type `void (Core::*)()` thats a member function pointer, but the constructor takes a `void (*)(void)` thats a pointer to free function — 463035818_is_not_an_ai, Oct 13 '20 at 10:07
@idclev463035818 So how can I define IO class to accept any member function pointer from any class? Is this possible? — Masoud Rahimi, Oct 13 '20 at 10:15
What do you want to do with pointers to methods of arbitrary type? `template IOControl(T t);` would work, but remember: You need an object to call the method. Maybe open a new question — 463035818_is_not_an_ai, Oct 13 '20 at 10:36

Pass class member function address to another member in initialization list

0 Answers0