如何在 c++ 中超载 class 访问器

Question

I have a class that just has one single int value, and 2 more classes that extend this class. I want to be able to access this int value by just calling an instance of the class, rather than instance.val, for simplicity.

class thing {
  public:
    int val;
    thing(int a) : val(a) {}
};

class proc: public thing {
  public:
    proc (int a) : thing(a){}
};

class res : public thing {
  public:
    res(int a) : thing(a){}
};

int main(){
  proc x (3);
  res y (5);
  int* array = new int[10];

  //I want to be able to do this:
  cout << x << " " << y << endl;
  array[x]; array[y];

  //rather than this:
  cout << x.val << " " << y.val << endl;
  array[x.val]; array[y.val];
}

Basically, i want to use my created classes as ints, since all i need to store is the int value, but i need 2 different types of ints, as they will represent 2 slightly different, but almost the same things.

Answer 1

Add a conversion operator to your class:

class thing {
    public:
        int val;
        thing(int a) : val(a) {}

        operator int() const { return val; }
};

Now, you can pass an instance of your class anywhere an int is accepted.