How to extern Class objects C++ MFC

Question

I am working on MFC SDI application, in which I include one C++ generic class, but I have a problem and am stuck on it.

I have a generic C++ class in Tree.h and its implementation Tree.cpp , as well as two more classes, say a_Class.h and b_Class.h .

The problem is:

I am making an instance of Tree.h in a_Class.cpp like this:

Tree *obj = new Tree()

I declared it it globally. Now, I want to use this very same object in b_Class .

For this I use the extern keywork, in b_Class.cpp as follows:

extern Tree *obj;

This run fine, but it doesn't use the same object. In the background, it declares separate objects.

How can I fix this?

Answer 1

From your description it sounds like it should work. You might rewrite it differently, in a_Class.cpp add global function:

static Tree* obj = new Tree();
Tree* GetTreeObj() {
   return obj;
}

in b_Class.h add:

extern Tree* GetTreeObj();

then use GetTreeObj() to retrieve Tree pointer