Function pointer in a C++ class

Question

I’m having trouble putting a pointer to a function in a class:

int Menu::validaescolha(){
    cout << 1232;
    return 1;
}
int Menu::inicial(){
    int (Menu::*funcs)() = &Menu::validaescolha;
    funcs();
    return 0;
}

Return these errors:

1 - Error (active) E0109 expressions preceding apparent call parentheses must have function type (pointer-to-)

2 - Error C2064 the term cannot be evaluated as a function receiving 0 arguments

I have no idea what to do here...

Answer 1

Pointer to method is a technique not widely used (I think), and so few people know. I had to do some research to find out that you need to use additional parentheses when using the pointer. Note that it is necessary to have an object to call the method through the pointer.

This applies to nonstatic methods. Pointers for static methods are not special, they are declared in the same way as pointers for "common" functions (which are not members of a class).

#include <iostream>
using namespace std;

class Menu
{
   public:
      int validaEscolha();
      static int stValidaEscolha();
      int inicial();
};


int Menu::validaEscolha()
{
   cout << 1232 << endl;
   return 1;
}

int Menu::stValidaEscolha()
{
   cout << 1232 << endl;
   return 1;
}

int Menu::inicial()
{
   // ponteiro para método não estático
   int (Menu::*funcs)() = &Menu::validaEscolha;
   (this->*funcs)();

   // ponteiro para método estático
   int (*stFuncs)() = &Menu::stValidaEscolha;
   stFuncs();

   return 0;
}

int main()
{
   Menu m;
   m.inicial();
}