asked on

Data Exchange

info:
The MFC application I am writing has Database DAO file support.

Its called TheoFrontEnd

I have an edit box on my main form that is displaying the wrong value.

The control is:
IDC_EDIT_RecordCNT

Its member varible is:
long m_RecordCNT;

The applications CTheoFrontEndView::OnInitialUpdate()function looks like this:
void CTheoFrontEndView::OnInitialUpdate()
{
//start code generated by MFC
m_pSet = &GetDocument()->m_theoFrontEndSet;
CDaoRecordView::OnInitialUpdate();
GetParentFrame()->RecalcLayout();
ResizeParentToFit();
//end code generated by MFC

//start of my code
m_pSet->MoveLast();
m_RecordCNT=m_pSet->GetRecordCount(); //counts the number of records in the table I have linked to
//end of my code
}

When I debug the app. the member variable m_RecordCNT DOES get the correct value! However, that values does not show up in the edit box that the member variable is attached to.

From what I can tell the
void CTheoFrontEndView::DoDataExchange(CDataExchange* pDX)
function is never getting called. (maybe)

Or

Maybe I need to invalidate the rectangle that the edit box occupies. I don't know.

What do you think?

Thanx
Ace

Smave

ASKER

OK. After little more investigation the
void CTheoFrontEndView::DoDataExchange(CDataExchange* pDX)
is getting called.

But somehow the member variable
long m_RecordCNT;
is getting reset to 0 after the
void CTheoFrontEndView::OnInitialUpdate()
is executed.

I moved the statement
m_RecordCNT=m_pSet->GetRecordCount(); //counts the number of records in the table I have linked to
from the
void CTheoFrontEndView::OnInitialUpdate()
function to the
void CTheoFrontEndView::DoDataExchange(CDataExchange* pDX)
function.
Now the correct value does display in the edit box.

This fix works, but it is unacceptable. I only need to count the records once, not every time the view is changed.

Why is the member variable loosing its value?

Thanx
Dave

DanRollins

To transfer the data from a variable to a screen element, use
UpdateData( FALSE );

This assumes that you have used ClassWizard to associate a m_RecordCNT with the edit control. If so, there will be something like this in your DoDataExchange fn:

DDX_Text(pDX, IDC_EDIT1, m_sEdit1);

-- Dan

Smave

ASKER

Yes the class wizard did add:
DDX_Text(pDX, IDC_EDIT_RecordCNT, m_RecordCNT);
to the
void CTheoFrontEndView::DoDataExchange(CDataExchange* pDX)
function.

Somehow the
m_RecordCNT
member variable is loosing it values after the
void CTheoFrontEndView::OnInitialUpdate()
function is run.

I thought the member variable is global within the CTheoFrontEndView scope.

Ace

Smave

ASKER

Maybe this deserves 100 points.

ASKER CERTIFIED SOLUTION

DanRollins

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peterdownes

Hi S,

As Dan has said, call UpdateData(FALSE);

The problem with your code is that CDaoRecordView::OnInitialUpdate() calls UpdateData(FALSE) before you set the value of m_RecordCNT

void CTheoFrontEndView::OnInitialUpdate()
{
//start code generated by MFC
m_pSet = &GetDocument()->m_theoFrontEndSet;
CDaoRecordView::OnInitialUpdate();
GetParentFrame()->RecalcLayout();
ResizeParentToFit();
//end code generated by MFC

//start of my code
m_pSet->MoveLast();
m_RecordCNT=m_pSet->GetRecordCount(); //counts the number of records in the table I have linked
to
UpdateData(FALSE);
//end of my code
}

So the way to fix the problem is to add UpdateData as above.

Regards.