Associated dialog controls with a structure member variables

Question

I have this struct definition:

typedef struct tagPublicTalkInfo
{
    CString     strAwayCong1;
    CString     strAwayCong2;
    CString     strAwayBrother1;
    CString     strAwayBrother2;
    CString     strChairman;
    CString     strCong;
    CString     strHosp;
    CString     strReader;
    CString     strBrother;
    CString     strTheme;
    CString     strWTConductor;          
    CString     strInterpreter;          
    CString     strMisc;                 
    CString     strWatchtowerStudyTheme; 
    CString     strServiceTalkTheme;     
    CString     strBibleVersesReader;    
    CString     strVideoHost;            
    CString     strVideoCohost;          
    CString     strOpeningPrayer;        
    CString     strClosingPrayer;        
    int         iSongStart;              
    int         iSongMiddle;             
    int         iSongEnd;                
    int         iThemeNumber;            

} S_TALK_INFO;

This structure is passed into a dialog and retrieved like this:

void CWeekendMeetingDlg::SetWeekendMeetingInfo(S_TALK_INFO &rsTalkInfo)
{
    m_sWeekendMeetingInfo = rsTalkInfo;
}

S_TALK_INFO CWeekendMeetingDlg::GetWeekendMeetingInfo()
{
    return m_sWeekendMeetingInfo;
}

At the moment I am mapping the dialog controls to distinct variables and transfer to / from my structure. For example:

m_strChairman = m_sWeekendMeetingInfo.strChairman;
m_sWeekendMeetingInfo.strChairman = m_strChairman;

Is possible to map my controls directly to the structure member CString variables or would that be considered bad practice?

Not sure if you're familiar with the system, but the [Dialog Data Exchange](https://www.codeproject.com/Articles/14510/Dialog-Data-Exchange-in-MFC) mechanism provided by MFC's `CDataExchange` class does what I think you're asking about. — Adrian Mole, Jun 06 '20 at 18:56
@AdrianMole Usually I just add a variable to the control via the GUI and take it from there. Do the contents of the DDE is all done for me. I have never done my own thing. — Andrew Truckle, Jun 06 '20 at 19:03
I have never made any really extensive use of the DDX stuff, either. But that linked blog looks quite thorough. (There are also numerous users here on Stack Overflow with the same username as the blogger, but I wouldn't like to guess which, if any, *is* the blogger.) — Adrian Mole, Jun 06 '20 at 19:06

score 2 · Accepted Answer · answered Jun 07 '20 at 23:59

Yes, as Adrian says, you don't have to confine yourself to using the variables that the wizard would hand you. I used my test project to do this with the about dialog.

struct data_type {
    CString a_data;
    CString b_data;
};

class CAboutDlg : public CDialogEx
{
    data_type& dlg_data;
public:
    CAboutDlg(data_type&);
    //CString dummy;
    enum { IDD = IDD_ABOUTBOX };
protected:
    virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support
protected:
    DECLARE_MESSAGE_MAP()
public:
};

CAboutDlg::CAboutDlg(data_type& data) : CDialogEx(IDD_ABOUTBOX), dlg_data(data)
{
}

void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
    CDialogEx::DoDataExchange(pDX);
    DDX_Text(pDX, IDC_EDIT1_ABOUT, dlg_data.a_data);
    DDX_Text(pDX, IDC_EDIT2_ABOUT, dlg_data.b_data);
}

// App command to run the dialog
void CMFCApplicationApp::OnAppAbout()
{
    data_type data{ L"this", L"that" };
    CAboutDlg aboutDlg(data);
    aboutDlg.DoModal();
    assert(false);
}

Here I passed a reference to the external data to work on it directly. Because of the DoDataExchange mechanism, The data will only be modified if the user pushes OK. I added the first DDX_Text handler with the wizard, hence the commented value dummy. I just copied and pasted that handler to add the second.

I put the assert in the app command so the program would break there and could examine the data.

Associated dialog controls with a structure member variables

1 Answers1