Question

template <class T>
class List
{
    public:

        List();
        ~List();

        ...

    protected:

        template <class T> struct Item
        {
            struct Item* next;
            T data;
        };

        ...

        struct Item<T>* allocate();
};

template <class T>
struct Item<T>* List<T>::allocate() // error here
{
    ...
    return object; // struct Item<T>*
}

how can i do that?

Answer 1

The problem is deeper in fact:

You don’t have to declare Item as being template, because it’s a nested class within a template class it has access to T.

template <class T>
class List
{
public:

private:
  struct Item { ... };
};

And then you would define access like so:

template <class T>
typename List<T>::Item List<T>::access(...) {}

The point here is that List is a template class, so its parameters must be specified, while once T is specified for List it’s not necessary to precise it once again.

Note typename 😉