forward declaration of using in c++11

Question

I'm trying to use a type alias of an object in another header without including header file .

My simplified version of code is :

// A.h
    #include <vector>
    using Vector=std::vector<int>;

====================================================

//B.h
using Vector;//forward declaration but not working !(Vector has not beed declared)
int foo(Vector*);

====================================================
//B.cpp
#include "A.h"
void foo(Vector*){}

I don't want to write using Vector=std::vector<int>; again in B.h because It's definition must be same as definition of Vector in A.h and It may change in future and I can't include it because my code have circular dependency.

Is forward declaration of using possible in c++11 ?

Answer 1

It is not possible, however the following could be a workaround.

// Common.h
...
#include <vector>
using Vector=std::vector<int>;
...

Afterwards you include Common.h in both, A.h and B.h.