Restrict Textbox Input in C++

This is a discussion on Restrict Textbox Input in C++ within the C++ Programming forums, part of the General Programming Boards category; I'm writing a simple calculation program using C++. I'd like to restrict my textboxes to only except valid hex numbers ...

  1. #1
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    Restrict Textbox Input in C++

    I'm writing a simple calculation program using C++. I'd like to restrict my textboxes to only except valid hex numbers as input. Is there an easy way to do this? I will post code if necessary but my code is all under the calculation button and I think this needs to be put behind the textbox itself. The default VS 2008 code is all I have there now.

  2. #2
    Registered User bobknows's Avatar
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    are you using char or int for the input?
    int wont accept letters

    once you are using char just use an if statement or a switch like this:
    Code:
    char hexnumber[6]
    for(int a = 0; a < 6; a++;
    {
          cin << hexnumber[a];
          switch hexnumber[a]
          {
                case '1':
                case '2':
                 ...... and do on,
                            then: 
                case 'F':
                   break;
                  default:
                cout << "that is invalid input try again";
                break;
           }
    or test the whole input after you cin it,

    i have no idea on how to do this in visual but it should be pretty easy to convert

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    Quote Originally Posted by dolfaniss View Post
    I'm writing a simple calculation program using C++. I'd like to restrict my textboxes to only except valid hex numbers as input. Is there an easy way to do this? I will post code if necessary but my code is all under the calculation button and I think this needs to be put behind the textbox itself. The default VS 2008 code is all I have there now.
    What UI library are you using? QT, WxWidgits, Win32, MFC, etc?
    bit∙hub [bit-huhb] n. A source and destination for information.

  4. #4
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    Win32 library.

  5. #5
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    I believe you can do this by catching EN_UPDATE via WM_COMMAND, then modifying the edit control's text if it contains unwanted characters.

    If this doesn't work, then I think you need to subclass the control and catch the keypress events.
    bit∙hub [bit-huhb] n. A source and destination for information.

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