Calling cdialog function from a subclassed control

[NasterMain]

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..

[Mike Harnad]

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.

[NasterMain]

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?? ._.

[Mike Harnad]

What source file is generating the errors?

[NasterMain]

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 (

[Mike Harnad]

Try moving the include file inside the pragma.

[NasterMain]

No success, same errors

[Mike Harnad]

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.

[NasterMain]

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?

[NasterMain]

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.. ._.

[Mike Harnad]

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.

[Igor Vartanov]

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,..

// 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
};

[NasterMain]

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!

[Arjay]

See Forward Declaration