Formatting an Edit Box Using strstream

Formatting an Edit Box Using strstream

Objective: you have a floating point variable, and you want to apply iostream-type formatting to it so that it looks good in an Edit box. So instead of using iostream objects (like cout), we'll use strstream (string stream) objects that use a regular character array to hold the formatted character that ultimately need to be displayed.

Key concepts -

You need to include

strstrea.h (yes, there is no m at the end)
iomanip.h

You need to define a character array that will hold the 'output' string.

static char chararray[10];

// static so it hangs around from call to call

// 10 is an arbitrary length that I picked out of thin air

You need to define the string stream object, and initialize it so that it is associated with the character array --

static strstream stringstream(chararray, 10);

My sample uses UpdateData to get a floating point number from the GUI, then applies ordinary iostream-type filters to convert the number so that it has 2 digits of accuracy.

Assuming x has the floating point number to be formatted --

stringStream << setiosflags(ios::fixed) << setprecision(2) << setiosflags(ios::showpoint) << x << ends;

You then have to convert the character array to floating point, assuming that the member variable (m-textbox) associated with the Edit box was a floating point variable.

m_textbox = atof(chararray);

Finally, we use UpdateData to refresh the Edit box.

Click HERE to download a zip containing all the files in the project

Filenames used in the project --

format.aps format.clw format.cpp format.dsp format.dsw format.h
format.ncb format.opt format.plg format.rc FormatDlg.cpp FormatDlg.h readme.txt

res directory --

resource.h stdafx.cpp stdafx.h

Code needed at the top of the Dialog --

#include <strstrea.h>
#include <iomanip.h>

Code needed to go with the 'Format' button --

void CFormatDlg::OnOK()
{
float x;
static char chararray[10];
static ostrstream stringStream(chararray, 10);
UpdateData(TRUE);
x = m_textbox;
stringStream << setiosflags(ios::fixed) << setprecision(2) <<setiosflags(ios::showpoint) << x << ends;
m_textbox = atof(chararray);
UpdateData(FALSE);
stringStream.seekp(0); //resets the stream for susequent uses
//MessageBox(chararray);
//uncomment this, and then input 1.9978 and see what happens
}

No, you can't redo lab 3 !!
Created & Maintained by DrB on Mon, Oct 23, 2000