Error returning std :: set <T> :: iterator in the template

Question

I am wrapping a template around std :: set. Why am I getting an error to declare a Begin () function?

template <class T>
class CSafeSet
{
    public:
        CSafeSet();
        ~CSafeSet();

        std::set<T>::iterator Begin();

    private:
        std::set<T> _Set;
};

error: type 'std :: set, std :: allocator <_CharT → is not inferred from the type' CSafeSet

Answer 1

Try typename :

template <class T>
class CSafeSet
{
    public:
        CSafeSet();
        ~CSafeSet();

        typename std::set<T>::iterator Begin();

    private:
        std::set<T> _Set;
};

You need a type name there, because it depends on the T template. For more information, see the link above the code. Many of these things are simplified if you use typedef:

template <class T>
class CSafeSet
{
    public:
        typedef T value_type;
        typedef std::set<value_type> container_type;
        typedef typename container_type::iterator iterator_type;
        typedef typename container_type::const_iterator const_iterator_type;

        CSafeSet();
        ~CSafeSet();

        iterator_type Begin();

    private:
        container_type _Set;
};

, , CSafeSet , set, :

template <class T, class Compare = std::less<T>, class Allocator = std::allocator<T> >
class CSafeSet
{
    public:
        typedef T value_type;
        typedef Compare compare_type;
        typedef Allocator allocator_type;

        typedef std::set<value_type, compare_type, allocator_type> container_type;
        typedef typename container_type::iterator iterator_type;
        typedef typename container_type::const_iterator const_iterator_type;

        // ...
}

, , , , . , Begin() , , Begin() ( , C , , :])