Re: problem with header files

From:

David Wilkinson <no-reply@effisols.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 26 May 2006 14:40:20 -0400

Message-ID:

<#eNrPPPgGHA.4776@TK2MSFTNGP05.phx.gbl>

Bhargs wrote:

Pls observe the comments and this works even though I do not forward
declare it.
CUserDlg is a class derived from Dialog .
This works even though you do not forward declare it.

#include "MyListSeriesResltsCtrl.h"
#include "IconsListCtrl.h"
#include "UserDataDlg.h"

//class CUserDlg;

class CMyListSeriesCtrl : public CListCtrl
{
    DECLARE_DYNAMIC(CMyListSeriesCtrl)
private:
    BOOL m_bIsRowSelected;
    int nSortedCol;
    BOOL bSortAscending;

public:
    CMyListSeriesCtrl();
    virtual ~CMyListSeriesCtrl();
    CMyListSeriesResltsCtrl *m_pmyListSeriesCtrl;
    CIconsListCtrl *m_IconListCtrl;
    CUserDataDlg *userDlg;

    void SetListToFill(CMyListSeriesResltsCtrl *pListCtrl ){
        m_pmyListSeriesCtrl = pListCtrl;

    }
    void SetTabToFill(CUserDataDlg *pCtrl ){
        userDlg= pCtrl;
    }

    BOOL SortTextItems( int nCol, BOOL bAscending,
                    int low ,int high );
    void SetApply();

protected:
    DECLARE_MESSAGE_MAP()
public:
    afx_msg void OnLvnKeydownListResults2(NMHDR *pNMHDR, LRESULT
*pResult);
public:
    afx_msg void OnNMRclick(NMHDR *pNMHDR, LRESULT *pResult);
public:
    afx_msg void OnNMClick(NMHDR *pNMHDR, LRESULT *pResult);
public:
    afx_msg void OnLvnColumnclick(NMHDR *pNMHDR, LRESULT *pResult);
    afx_msg void OnHeaderClicked(NMHDR* pNMHDR, LRESULT* pResult);
};

Bhargs:

I think your commented line should be

//class CUserDataDlg;

yes? But anyway, you have already included "UserDataDlg.h", so you do
not need to forward declare also.

BUT, it is not just a matter of making the code work. As a matter of
style, headers should not include other headers unless it is necessary.
Two reasons:

1. Sometimes you have to use forward declaration to avoid circular
references.

2. Including unnecessary headers can increase your compile times.

If the definition of class A only uses pointers or references to class
B, then B can be forward declared in A.h. Only base classes and
non-pointer members require that the other header be included.

In your example, all of CMyListSeriesResltsCtrl, CIconsListCtrl and
CUserDataDlg can be forward declared in the header file (they must of
course be included in the implementation file).

David Wilkinson