重载强制转换运算符时的C ++模糊性

Question

Found:
Ambiguity while overloading the cast operator

and

C++ Operator Ambiguity

not helpful

Situation:

Inside the container class's body I have:

operator T& () const {
    return *data;
}

operator const T& () const {
    return *data;
}

The intent being that:

container<object> test = new object;
object& whatever = test; //<--uses (T&) cast
const object& other = test; //<--uses (const T&) cast

However the second one causes an error because it is ambiguous.

I completely see why the compiler is complaining, it is okay to assign a object& and a const object& to a const object& however I'd like it to not complain and choose the second (return const object& )

Oh wait, just got my answer.

Answer 1

Even though they're different conversion operators (not just overloads of one), the ambiguity is resolved by removing the const you have on the first one.

Thus:

operator T& () {
    return *data;
}

operator const T& () const {
    return *data;
}

Alternatively, if it really makes sense to provide non- const access to the pointed to data via a const object, then just do

operator T& () const {
    return *data;
}

Answer 2

Stop being silly. As I said you may assign a object& or a const object& to a const object& so the first cast operator is sufficient for the job in either case.

Silly me. Hope this helps someone in the future!