Question

I have to declare Iter as typename but no typedef.
Then, I cannot use Iter in my template class declaration => frustrating 🙁
Please teach me how to use Iter, or else explain me why C++ is so nasty…

template <typename T>
struct MyContainer
{
  typedef  std::vector<T>  Vec;
  typename Vec::iterator   Iter;

  void Fo (typename std::vector<T>::iterator);  //ok
  typename std::vector<T>::iterator Ba();       //ok

  void Foo (Iter);   //error: 'Iter' is not a type
  Iter Bar ();       //error: 'Iter' does not name a type
};                   //(gcc 4.1.2)

1. Why typedef cannot be used to declare Iter? Why not?
2. How to use Iter within the template class? (e.g. as function parameter type)

EDIT
In the instruction typename Vec::iterator Iter; the keyword typename says Vec::iterator is a type (i.e. not a static member function/attribute). Therefore, Iter is not declared as a type, but as a variable using the type Vec::iterator.

Answer 1

1. typedef can be used alongside typename. So it becomes:

   typedef typename vec::iterator Iter;
   

2. Just use Iter now.

   template <typename T>
   struct MyContainer
   {
     typedef  std::vector<T>         Vec;
     typedef typename Vec::iterator  Iter;
   
     void Foo (Iter);   //ok
     Iter Bar ();       //ok
   };