Calling cdialog function from a subclassed control

I am not very pratical with classes interaction and I would like to know why if I declare a CDialog member variable into my subclassed control's class, visual studio gives weird errors like error C2065: 'IDD_MY_DIALOG' : undeclared identifier



Better explanation:

I have a mfc dialog with its nice class CMyDialog and all handlers.. OnInitDialog.. OnCancel... etc...

I have a control subclassed to something.. CStatic for example, so I have a class for this control derived from CStatic, and I'll call CMyCustomLabel

Why if I try to
#include "MyDialog.h"
into MyCustomLabel.h, visual studio starts to give me a lot of strange errors?

How do I call a function inside CMyDialog from a function inside CMyCustomLabel ??


Can't understand this problem..

First, dialog IDs (ie. 'IDD_MY_DIALOG') are typically stored in "resource.h". Make sure you include resource.h. Second, from your problem description, it would appear that you are trying to display a dialog/call a dialog function from within a static control. Is this correct? How are you planning to accomplish this? You may want to post some code that shows what you are trying to accomplish.

Here's an example of what I am trying to do:

#include "MyDialog.h" <- only including this causes me to have a LOT of weird errors
#pragma once

// CTabClass

class CTabClass : public CTabCtrl
{
DECLARE_DYNAMIC(CTabClass)

public:
CTabClass();
virtual ~CTabClass();
protected:
DECLARE_MESSAGE_MAP()
public:
afx_msg void OnTcnSelchange(NMHDR *pNMHDR, LRESULT *pResult);
CMyDialog dlg;
};


Simple including a .h file of a mfc dialog class causes a lot of errors, here's some:

1> c:\blabla..\tabclass.h(6) : see declaration of 'CTabClass'
1>c:\blabla..\tabclass.cpp(10) : error C2027: use of undefined type 'CTabClass'
1> c:\blabla..\tabclass.h(6) : see declaration of 'CTabClass'
1>c:\blabla..\tabclass.cpp(10) : error C2496: 'classCTabClass' : 'selectany' can only be applied to data items with external linkage
1>c:\blabla..\tabclass.cpp(10) : error C2027: use of undefined type 'CTabClass'
1> c:\blabla..\tabclass.h(6) : see declaration of 'CTabClass'
1>c:\blabla..\tabclass.cpp(10) : error C2027: use of undefined type 'CTabClass'
1> c:\blabla..\tabclass.h(6) : see declaration of 'CTabClass'
1>c:\blabla..\tabclass.cpp(10) : error C2027: use of undefined type 'CTabClass'
1> c:\blabla..\tabclass.h(6) : see declaration of 'CTabClass'
1>c:\blabla..\tabclass.cpp(10) : error C2027: use of undefined type 'CTabClass'
1> c:\blabla..\tabclass.h(6) : see declaration of 'CTabClass'
1>c:\blabla..\tabclass.cpp(10) : error C2270: 'GetRuntimeClass' : modifiers not allowed on nonmember functions
1>c:\blabla..\tabclass.cpp(10) : error C2027: use of undefined type 'CTabClass'
1> c:\blabla..\tabclass.h(6) : see declaration of 'CTabClass'
1>c:\blabla..\tabclass.cpp(12) : error C2027: use of undefined type 'CTabClass'
1> c:\blabla..\tabclass.h(6) : see declaration of 'CTabClass'
1>c:\blabla..\tabclass.cpp(12) : error C2059: syntax error : ')'
1>c:\blabla..\tabclass.cpp(13) : error C2143: syntax error : missing ';' before '{'
1>c:\blabla..\tabclass.cpp(13) : error C2447: '{' : missing function header (old-style formal list?)

and so on..

What's wrong?? ._.

What source file is generating the errors?

the .h file of the control subclassed from CTabCtrl
And the error of IDD_MY_DIALOG undefined (that is NOT true, if i remove that include the compiling process goes okay) from the .h file of CMyDialog

Dunno what's wrong :((

Try moving the include file inside the pragma.

No success, same errors :(

If the code is not too large, I would suggest you post the cpp and header file(s) using Code tags. More than likely, the order of includes is at fault here.

I searched a little and I found I am trying to include B.h into A.h and A.h into B.h and this is not possible, this mechanism seems to be called "Header Guard"

Using the #define symbols should solve the problem, but still can't get it working!

Someone knows more please?

Here are the two include files:

-------------------------------- TabClass.h-------------------------

#pragma once

// CTabClass

class CPropListBoxDlg; <- THIS SHOULD TELL THE COMPILER A CPROPLISTBOXDLG IS ALREADY DEFINED

class CTabClass : public CTabCtrl
{
DECLARE_DYNAMIC(CTabClass)

public:
CTabClass();
virtual ~CTabClass();
protected:
DECLARE_MESSAGE_MAP()
public:
afx_msg void OnTcnSelchange(NMHDR *pNMHDR, LRESULT *pResult);
CPropListBoxDlg m_dlg;
};
----------------------------------------------------------------------
---------------PropListBoxDlg.h ----------------------------------
#if !defined(AFX_PROPLISTBOXDLG_H__B8AE534A_3892_11D4_BC48_00105AA2186F__INCLUDED_)
#define AFX_PROPLISTBOXDLG_H__B8AE534A_3892_11D4_BC48_00105AA2186F__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

#include "afxcmn.h"
#include "tabclass.h" <- INCLUDED



/////////////////////////////////////////////////////////////////////////////
// CPropListBoxDlg dialog

class CPropListBoxDlg : public CDialog
{
// Construction
public:
CPropListBoxDlg(CWnd* pParent = NULL); // standard constructor

~CPropListBoxDlg();

// Dialog Data
//{{AFX_DATA(CPropListBoxDlg)
enum { IDD = IDD_PROPLISTBOX_DIALOG };
//}}AFX_DATA

// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CPropListBoxDlg)
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
//}}AFX_VIRTUAL
public:
CTabClass m_tabctrl; <- MEMBER
};

//{{AFX_INSERT_LOCATION}}
// Microsoft Visual C++ will insert additional declarations immediately before the previous line.



#endif // !defined(AFX_PROPLISTBOXDLG_H__B8AE534A_3892_11D4_BC48_00105AA2186F__INCLUDED_)
---------------------------------------------------------------



It is surely an header inclusion error

Additionally I neither can't find a good link to read about this "headerguard" system.. ._.

Earlier, I asked what your intentions were with this design. Now that you've posted code, I'm beginning to think your program design may be at fault. Assuming I am wrong, you will need to define 'm_dlg' (in TabClass.h) as a CDialog object pointer and cast it to 'CPropListBoxDlg' when you use it.

I still think you need to reconsider your program design and interaction first.

Definitely you are right, Mike, the design smells not good. :) Define in class a member that has inside the member of the class currently being defined... Disaster. Nevertheless,..

Code:

---

// CTabClass

class CPropListBoxDlg; <- THIS SHOULD TELL THE COMPILER A CPROPLISTBOXDLG IS ALREADY DEFINED
// :D Never it should! This just hints the compiler that the symbolic
// name is a name of class defined somewhere to let the
// compiler be aware of variable pointer size if any would have been met
// prior that class full declaration

class CTabClass : public CTabCtrl
{
DECLARE_DYNAMIC(CTabClass)

public:
CTabClass();
virtual ~CTabClass();
protected:
DECLARE_MESSAGE_MAP()
public:
afx_msg void OnTcnSelchange(NMHDR *pNMHDR, LRESULT *pResult);
CPropListBoxDlg* m_pDlg;  // that would be enough to calm your compiler down
};

---

Thanks so much to everyone, problem solved.

This inclusion system is called: "Forward Declarations" and lets two classes perform a "reciprocal inclusion"

Notice that the pointer to CPropListBoxDlg class has to be initialized into the constructor of the CTabClass class:

CTabClass::CTabClass(CPropListBoxDlg *pointer)
{
m_pDlg = pointer;
}


I'll write an article soon or later about this mechanism I just learned, because excepted for this great forums, web lacks of papers at this purpose.

Thanks again to everyone! :D

See Forward Declaration