Wrapping an object and pretend it's an int

Question

I have a class Object that I'd like to use as if it were an int . In other words I want to pass this object to functions that accepts int , int* or int& so that the functions "see" actually ony the wrapped int value.

The code below illustrates what I want to do. I was able to write the code for int and int* but I'm not able to write the code for int& .

#include <cassert>   

class Object
{
public:
  int bla = 0;
  int val = 0;   // the int being wrapped

  Object(int v) : val(v) {};
  operator int() const { return val; };
  int *operator &() { return &val; };

#if 1
  int & operator() { return val; };   // << does not compile
#endif
};

int func(int val) {
  return val * 2;
}

void Bar(int* pval, int val) {
  *pval = val;
}

void Foo(int & pval, int val) {
  pval = val;
}

int main() {
  int val;
  Bar(&val, 123);
  assert(val == 123);
  Foo(val, 789);
  assert(val == 789);    

  Object o(8);
  assert(func(o) == 2 * 8);   // operator int()
  Bar(&o, 1234);              // int *operator &()
  assert(o.val == 1234);

#if 1
  Foo(o, 456);                // << does not compile
  assert(o.val == 456);
#endif
}

If #if 1 is replaced with #if 0 , the code works as expected.

Could anybody point me into the right direction so Foo(o, 456); compiles?

Answer 1

The problem is the conversion operator, which you have the wrong syntax for.

It should be

operator int&() { return val; }