Accepting only a to z and a to Z (only alpabatic characters)

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How to implements to access only alphabetic characters in vc++ mfc

What I have tried:

BOOL CFilterGroup::PreTranslateMessage(MSG* pMsg)
{
if (pMsg->message == WM_CHAR)
{
if ((pMsg->wParam >= '\x41' && pMsg->wParam <= '\x5A'))
{

return FALSE;
}
}
return CDialogEx::PreTranslateMessage(pMsg);
}

but its not ignoring and its taking all characters

Posted 23-Apr-17 21:43pm

Member 13089825

Updated 23-Apr-17 22:24pm

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Jochen Arndt · Accepted Answer · 2017-04-23T22:23:00

You have to reverse the check and the return value.

See CWnd::PreTranslateMessage[^]:

Quote:
Nonzero if the message was translated and should not be dispatched; 0 if the message was not translated and should be dispatched.

You have to return TRUE if a message should be filtered out.

To check for lower and upper case ASCII letters (a-z, A-Z), you can use isalpha[^]

#include <ctype.h>

BOOL CFilterGroup::PreTranslateMessage(MSG* pMsg)
{
    if (pMsg->message == WM_CHAR)
    {
        if (!isalpha(pMsg->wParam))
        {
            /* Return TRUE to indicate that message should not be dispatched. */
            return TRUE;
        }
    }
    return CDialogEx::PreTranslateMessage(pMsg);
}

Richard MacCutchan · Accepted Answer · 2017-04-23T22:24:00

Your test looks wrong; surely it should return TRUE to indicate an alphabetic character. Also, why use hex rather than actual characters? So ...

C++

if ((pMsg->wParam >= 'A' && pMsg->wParam <= 'Z') ||
    (pMsg->wParam >= 'a' && pMsg->wParam <= 'z'))
{
    return TRUE;
}

You can see what actual value is in wParam by using your debugger.

Accepting only a to z and a to Z (only alpabatic characters)

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