Question

If I have a pointer to an object that has an overloaded subscript operator ([]) why can’t I do this:

 MyClass *a = new MyClass();
 a[1];

but have to do this instead:

 MyClass *a = new MyClass();
 (*a)[1];

Answer 1

It’s because you can’t overload operators for a pointer type; you can only overload an operator where at least one of the parameters (operands) is of class type or enumeration type.

Thus, if you have a pointer to an object of some class type that overloads the subscript operator, you have to dereference that pointer in order to call its overloaded subscript operator.

In your example, a has type MyClass*; this is a pointer type, so the built-in operator[] for pointers is used. When you dereference the pointer and obtain a MyClass, you have a class-type object, so the overloaded operator[] is used.