UpdateData(TRUE)/(FALSE) and DoModal - internal steps

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Hi ,

In Dialog Base Application, if i call DoModal and UpdateData(TRUE) or (FALSE),what are the functions are getting called internally?.

for example:

CEdit m_strString;

In OnInitDialog, if i call UpdateData(FALSE) and what ever the data is initializing into m_strString that value is updated into edit control. If i won't use UpdateData(FALSE) means, the value is not updating.here what is happening?

void classname::OnInitDialog()
{

m_strString = "test_value";
UpdateData(FALSE);

return TRUE;
}

by default return type is TRUE in OnInitDialog, if i changed to FALSE, then what happen?.

what are all the functions are getting called?.

regards,
ranjith

Posted 27-Feb-14 18:45pm

ranjithkumar81

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Jochen Arndt · Answer 1 · 2014-02-27T20:58:00

Your example is wrong: Your m_strString variable is of type CEdit but it is used as CString.

You should read about Dialog Data Exchange[^] (DDX).

If you don't want to use DDX, add member variables of your control types and call the appropiate functions to set and get the values from within OnInitDialog (SetWindowText for CEdit) and OnOK (GetWindowText for CEdit).

See the MSDN for OnInitDialog[^] about the return value:

Quote:
Specifies whether the application has set the input focus to one of the controls in the dialog box. If OnInitDialog returns nonzero, Windows sets the input focus to the default location, the first control in the dialog box. The application can return 0 only if it has explicitly set the input focus to one of the controls in the dialog box.

[UPDATE]
The default implementation of OnInitDialog will call UpdateData(FALSE). So you don't have to call it yourself when initializing your control member variables before calling the base class function CDialog::OnInitDialog (which is missing in your example).