C ++：重载“对象指针” *运算符

Question

I was some misunderstanding about default operator definition(by compiler).

I have small class:

class Q
{
public:
    Q() {};
    Q(int i) { x = i; };
    ~Q() {};
    void print() { cout << x << endl; };
    Q& operator * ()
    {
        cout << "operator *\n";
        return *this;
    };
    const Q& operator * () const
    {
        cout << "operator *\n";
        return *this;
    };
private:
    int x;
};

And i'm doing this whit it:

int main()
{
    Q* obj_p = new Q(1);
    Q obj = *obj_p;
    obj.print();
    return 0;
}

I expected to see operator * , before 1 . But I saw only print() method result.

What does it mean? That I don't need to overload operator * - it's compiler work or that I do overloading somehow wrong?

Thanks.

Answer 1

obj_p is a pointer. You have not overloaded (and cannot do it anyway) the de-reference operator for a pointer. To invoke your overload, you need to act on an instance:

Q obj;
*obj;

Answer 2

There's no user-defined operator called - obj_p is a pointer, not an object, so the built-in dereference operator is called.

To complete juanchopanza's answer, you can call your operator on a pointer like so:

Q* obj_p = new Q(1);
Q obj = obj_p->operator*();

Answer 3

You use your '*' operator on Q pointer but you should use on Q objects. if you try *(*obj_p) you will see.