Question

Let’s say I have a class like this:

class LinkedList
{
    struct Node
    {
        int StoredValue;
        // ...
    };

    Node& GetNodeReference(std::size_t Index)
    {
        // ...

        return NodeReference;
    }

    public:

    int Get(std::size_t Index) const
    {
        return GetNodeReference(Index).StoredValue;
    }
};

This won’t compile because the const method Get uses GetNodeReference, which cannot be const because it returns a reference.

How can I work around this?

Answer 1

I’m not sure what you’re trying to achieve, but you could provide two overloads of GetNodeReference:

Node& GetNodeReference(std::size_t Index)
{
    // ...

    return NodeReference;
}

const Node& GetNodeReference(std::size_t Index) const
{
    // ...

    return NodeReference;
}

Note that the second overload has two const modifers, one at the beginning of the line for the return type and one at the end of the line for the implicitly passed *this object.

To avoid code repetition, you can implement the non-const overload based on the const overload:

const Node& GetNodeReference(std::size_t Index) const
{
    // ...

    return NodeReference;
}

Node& GetNodeReference(std::size_t Index)
{
    return const_cast<Node&>(static_cast<const LinkedList&>(*this).getNodeReference(Index));
}

This technique is discussed in Item 3 of Effective C++ by Scott Meyers.