How to create and use a class_b, inside a class_a

[tonnot]

I have a class_a and class_b classes (with their .h and .c files)
I create an instance of class_a into my main,cpp.
After I use it in other cpp files using 'extern' .
Ok, how I can to create an instance of class_b inside class_a to use it in this way :

class_a.class_b.mymethod

Now I have a unreferenced error.
A piece of code will be appreciated.
Thanks

[hamsterman]

//A.h
//header guard

struct A{
   int i;
   ...
};

//A.cpp
#include "A.h"
...

//B.h
//header guard
#include "A.h"

struct B{
   A a;
   ...
};

//B.cpp
#include "B.h"
...

//main.cpp
#include "B.h"

int main(){
   B b;
   return b.a.i;
}

?

[tonnot]

I have the same, except than I create the B b in main.cpp, later I use it using 'extern B b'.
Another more thing is that all is encapsulated into a QT DLL....
I'm going to think something more....


Thanks any way

[hamsterman]

you mean

//B.h
//header guard

struct B{
   int i;
   ...
};

//B.cpp
#include "B.h"
...

//A.h
//header guard
#include "B.h"

struct A{
   B b;
   ...
};

//A.cpp
#include "A.h"

extern A a;

void function(){
   a.b.i = 5;
}
...

//main.cpp
#include "A.h"

A a;

int main(){
   return 0;
}

?