Using & Setting Static Function Pointers in Different Classes

Question

I have 2 classes, A and B

A has a function called foo();

B has a static function pointer designed to point towards foo, let's call it fuu.

The definition of fuu in class B looks like this

static void (A::*fuu)();

Somewhere along the runtime class A sets fuu. The code I wrote resembles this

B::fuu = &A:foo;

This properly sets the function pointer, however I am unable to use it (I am calling it in the B class)

I've tried

*fuu();

 B::fuu();

 B::*fuu();

Is there a syntax error preventing me from dereferencing?

TLDR: Trying to call a non-static function from an instance of class A, from a static function in class B

aschepler · Accepted Answer · 2016-11-15 00:25:03Z

4

You need

(a.*fuu)();

where a is an object of class A, or

(aptr->*fuu)();

where aptr is a pointer of type A*.

You can't call a non-static member function of class A without an object of class A to call it on.

answered Nov 15, 2016 at 0:25

aschepler

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2 Comments

Andros Yang Over a year ago

Is there a reason for being unable to call a non-static member function? I assumed that since the pointer pointed to the address space then I would be able to just call it after dereferencing. Also would it be possible to work around this? Perhaps passing a non-static function into a static function as a callback?

epx Over a year ago

The pointer to a non-static member function is like a pointer to a function that passes an object pointer as the first parameter (that will be accessible as 'this' within the function). To call a function pointer like this, you need to pass all parameters, including the first one - the ways shown in answer are basically syntatic sugar to fill that 1st parameter.

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