What is wrong in the following code:
Point2D.h
template <class T>
class Point2D
{
private:
T x;
T y;
...
};
PointsList.h
template <class T>
class Point2D;
template <class T>
struct TPointsList
{
typedef std::vector <Point2D <T> > Type;
};
template <class T>
class PointsList
{
private:
TPointsList <T>::Type points; //Compiler error
...
};
I would like to create new user type TPointsList without direct type specification...
have you tried using the typename keyword?
template <class T>
class Points2DList
{
private:
typename TPoints2DList <T>::Type points; //using the typename keyword
...
};
Others have already answered your question, but I think, if you want to know why typename is required there, then you may see this topic:
The question is a bit unclear, but it appears that you are trying to instantiate a vector of Point2D without having the definition of the Point2D template available. Try adding #include "Point2D.h" to the top of PointsList.h. As other answerers have mentioned, you are also attempting to use a qualified dependant type without a typename, so you should also add change the line
TPointsList <T>::Type points; //Compiler error
to:
typename TPointsList <T>::Type points;
What is TPoints2DList? It's not declared anywhere.
Now that TPoints2DList is declared as a struct, it has be referenced as such:
private:
struct TPointsList <T>::Type points; //should compile now
#include <vector> is added.