Forward declaration problem

[linq936@hotmail.com]

Hi,
I have 2 classes, h1 and h2, declared in 2 seperated header files h1.h
and h2.h and implementated in 2 seperated source files h1.c and h2.c.

The h1.h looks like this,

#ifndef H1_H
#define H1_H

#ifndef H2_H
#include "h2.h"
#endif

namespace ns {
class h1 {
<some stuff>
}
}
#endif


The h2.h looks like this,

#ifndef H2_H
#define H2_H

#include "h1.h"
// NOTICE that I include the header without condition

namespace ns {
class h2 {
h1 h1_obj;

<some stuff>
}
}
#endif

the h1.c looks like this,
#ifndef H1_H
#include "h1.h"
#endif

<some code>

when I compile h1.c using Visual C++ compiler I get an error, error
C2079: 'h1_obj' uses undefined class 'ns::h1'.

Then I updated h2.h by adding a forward declaration of class h1 like
this,
#ifndef H2_H
#define H2_H

#include "h1.h"

namespace ns {
class h1;

class h2 {
h1 h1_obj;

<some stuff>
}
}
#endif

But I get the same error.

Any idea?

[linq936@hotmail.com]

Re: Forward declaration problem


linq936@hotmail .com wrote:[color=blue]
> Hi,
> I have 2 classes, h1 and h2, declared in 2 seperated header files h1.h
> and h2.h and implementated in 2 seperated source files h1.c and h2.c.
>
> The h1.h looks like this,
>
> #ifndef H1_H
> #define H1_H
>
> #ifndef H2_H
> #include "h2.h"
> #endif
>
> namespace ns {
> class h1 {
> <some stuff>
> }
> }
> #endif
>
>
> The h2.h looks like this,
>
> #ifndef H2_H
> #define H2_H
>
> #include "h1.h"
> // NOTICE that I include the header without condition
>
> namespace ns {
> class h2 {
> h1 h1_obj;
>
> <some stuff>
> }
> }
> #endif
>
> the h1.c looks like this,
> #ifndef H1_H
> #include "h1.h"
> #endif
>
> <some code>
>
> when I compile h1.c using Visual C++ compiler I get an error, error
> C2079: 'h1_obj' uses undefined class 'ns::h1'.
>
> Then I updated h2.h by adding a forward declaration of class h1 like
> this,
> #ifndef H2_H
> #define H2_H
>
> #include "h1.h"
>
> namespace ns {
> class h1;
>
> class h2 {
> h1 h1_obj;
>
> <some stuff>
> }
> }
> #endif
>
> But I get the same error.
>
> Any idea?[/color]

OK, solve the problem, I changed h1.h like this,

#ifndef H1_H
#define H1_H

namespace ns {
class h1 {
<some stuff>
}
}

#ifndef H2_H
#include "h2.h"
#endif

#endif

Now it is ok.