Question

I’m implementing a class Aviary, which can store pointers to Bird-objects. Now, I have the following:

class Aviary {

public:
    const Bird &operator[](const size_t index) const {
    return birds[index];
    }

    Bird &operator[](const size_t index) {
    return birds[index];
    }

private:
    std::vector<Bird*> birds;

The Bird-objects are stored as pointers in order to avoid object-slicing. However, there is a problem with the operator[]-implementation (Reference to type ‘const Bird’ could not bind to an lvalue of ‘const value_type’ (aka ‘Bird *const’)).

How do I implement the operator[] properly?

Answer 1

You need to dereference:

return *(birds[index]);

birds[index] is a Bird*, so you can’t directly return it as a Bird&.