C++ Function Callback using class member and run it in main

Question

I know, many post asking about this, been reading about 10 post with long answers but, every post seems different case and needs different implementation.

so, what did i do wrong here?

#include <iostream>
using namespace std;
class Foo {
   public:
    void callbackFunc(void (*funcParam1)());
    void funcA();

};
void Foo::callbackFunc(void (*funcParam1)()) {
    funcParam1();
}
void Foo::funcA() { cout << "func A OK.." << endl; }
void aa(){
    int x =0;
}
Foo bar;
int main() { bar.callbackFunc(bar.funcA); }

this example throws error: invalid use of non-static member function ‘void Foo::funcA()’ in the main() especially in the callbackFuncparameter.

i want to use it in arduino later.

Member function pointers are different from regular function pointers (https://stackoverflow.com/questions/2402579/function-pointer-to-member-function) — SuperStormer, Mar 29 '20 at 21:41
it is not completely clear what you want to achieve with that design, as `callbackFunc` immediately calls the function. Do you acutally want to store the callback to call it later? Is the signature always `void(*)()`? — 463035818_is_not_an_ai, Mar 29 '20 at 21:42
@idclev463035818 `&Foo::funcA` is the correct syntax to refer to a non-static member function. — David G, Mar 29 '20 at 21:55
@idclev463035818 so, it'll be `bar.callbackFunc(&Foo::funcA);` ? — Jastria Rahmat, Mar 31 '20 at 08:37

score 2 · Answer 1 · answered Mar 29 '20 at 21:47

2

You may get away with the error with static funcA:

static void funcA();

Looks like the problem is that your callbackFunc expects a function pointer, but member function funcA is not a normal function and expects an object to begin with. Making it static would get away of the issue.

answered Mar 29 '20 at 21:47

artm

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hi, this partially correct. but, later on, each instance will utilize variables from each class. So, making it static won't solve the problem. But, thank you for the answer. – Jastria Rahmat Mar 31 '20 at 08:36

C++ Function Callback using class member and run it in main

1 Answers1