Which is best? (by Optimization & Speed)

[DjChris14]

Im experimenting something in my codes in MFC...
i use GetDlgItem function rather than creating a variable for a specific control (to avoid using UpdateData function).

Which is better among them? GetDlgItem or Creating Control Variable?

Thanks....

[gstercken]

Which is better among them? GetDlgItem or Creating Control Variable?

It's a tradeoff - using DDX variables is the better design, leads to less code, and it is safer, since you don't have to test whether the control exists and if it is of the right type. OTOH, calling UpdateData is generally slower, since it transfers data for all the controls in the dialog. Besides that, there are situations where you can't use UpdateData() since you don't want to update other controls, so you can't use UpdateData.
What I don't understand in your question: You are talking about control variables (like CEdit, CListCtrl), not DDX data members (like CString, int) - note that for DDX control members, UpdateData() does nothing, DDX just creates and attaches the control at the beginning. In that case, I don't see any advantage in using GetDlgItem ().

[DjChris14]

i see.. i always find some of the codes from former officemates and sample codes in the net that uses the UpdateData function just to reflect/retrieve the values to the control and vice versa. im pertaining to the DDX variables.. when i try to use the GetDlgItem function in passing or retrieving of values, i just found out that i dont have to use UpdateData function....

sample :
void CCompute::Calculate()
{
float fResult = 0;
UpdateData(1); // to get value
fResult = m_vdPenaltyRate * float(m_viDays); // m_vdPenaltyRate and m_viDays are DDX variables
m_vsPenalty.Format("%f",fResult); // m_vsPenalty is a DDX variable also
UpdateData(0); // to Show the result
}

[gstercken]

im pertaining to the DDX variables.. when i try to use the GetDlgItem function in passing or retrieving of values, i just found out that i dont have to use UpdateData function....

OK, so (according to the code you posted) you are not referring to control variables, but DDX value members. Then note that for the example you posted, DDX does a lot more. To do the same as your code without UpdateData, you would have to:

• Call GetDlgItem() to get the control as a CWnd*
• Check whether the control exists and if it is of the correct type
• Cast it to the correct type (e.g. CEdit)
• Create a CString variable and call GetWindowText() to retrieve the text (OK, these steps can be simplified if you calleed GetDlgItemText() directly)
• Check whether the string is a valid numerical string, and display an error message if not
• Convert the string to a float
• Optionally, check the range, and display an error message if out of range
• After the calculation is done, format the result as a string
• Call GetDlgItem again for the other control
• Do the checking etc. as described above
• Set the control's text via SetWindowText.

The DDX mechanism does all that for you.

[DjChris14]

thanks mr.gstercken...

i just looking about this area due to optimization of codes regards of usage and implimentation in a system.... some of my officemates always use the UpdateData function even thought only one control (DDX variable) was modified... which i found out that it makes the process slower...

[GCDEF]

thanks mr.gstercken...

i just looking about this area due to optimization of codes regards of usage and implimentation in a system.... some of my officemates always use the UpdateData function even thought only one control (DDX variable) was modified... which i found out that it makes the process slower...

Some optimizations aren't worth worrying about. In this case, unless you have hundreds of controls and you're calling UpdateData thousands of times, it isn't worth your time to try to optimize a function that doesn't impede the user or slow execution down noticably anyway.

[TheCPUWizard]

...which i found out that it makes the process slower...

I would be very interesting in seeing a timing study to back this claim up!

[PadexArt]

I don't know if the speed is so important. Wha I find really annoying when using member variables like that is that all of them get updated. There is no easy way ( if any) to update only 1 member variable.