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QIntValidators dont work for me



  • for example a part of my program code is:

        // decEdit is QLineEdit
        QIntValidator* decValidator =
                new QIntValidator(0, 255, decEdit);
        decEdit->setValidator(decValidator);
    

    this does not set any restrictions other than it should be three numbers



  • @nullbuil7
    Here is the example from the docs:

    QValidator *validator = new QIntValidator(100, 999, this);
    QLineEdit *edit = new QLineEdit(this);
    
    // the edit lineedit will only accept integers between 100 and 999
    edit->setValidator(validator);
    

    Are you saying this does not work as documented?



  • yes it doesn't work. if you say i want top to be 4000 it can go up to 9999. i don't know why


  • Lifetime Qt Champion

    Hi,

    The fact that you can enter higher value does not make sais value valid.

    By the way, which version of Qt are you using ?



  • @nullbuil7
    In the case of the docs example or your own code, what does edit->validate() return? Intermediate? Are you in the situation described in another example for QIntValidator v(100, 900, this); where it says:

    Notice that the value 999 returns Intermediate. Values consisting of a number of digits equal to or less than the max value are considered intermediate. This is intended because the digit that prevents a number from being in range is not necessarily the last digit typed.

    because this ties with your maximum of 255 and your "other than it should be three numbers [digits]"? When you know the user has finished typing you need the validator to return Acceptable, not Intermediate (or Invalid), for the input to be valid. A validator is not just about preventing the user from typing characters, it's also about checking the validity of the characters it has allowed the user to type, so two aspects.



  • i searched the web and made my own validator but i don't know how to use it. what should i do?

    #ifndef VALIDATOR_H
    #define VALIDATOR_H
    #include <QObject>
    #include <QValidator>
    
    class binValidator : public QValidator
    {
        Q_OBJECT
    public:
        explicit binValidator(QObject *parent = nullptr);
        virtual State validate(QString & input, int & pos) const override
        {
            if (input.isEmpty())
                return Acceptable;
    
            bool b;
            int val = input.toInt(&b);
    
            if ((b == true) && (val >= 0) && (val <= 255))
            {
                return Acceptable;
            }
            return Invalid;
        }
    };
    
    #endif
    


  • @nullbuil7 yes, i found it(QIntValidator, QDoubleValidtor) doesn't work too. my QLineEdit top can be input "999" when i set QIntValidator(0, 500)



  • Indeed it has been explicitly coded to return intermidiate in that case.

    You can use this:

    class HarshIntValidator : public QIntValidator{
        Q_OBJECT
        Q_DISABLE_COPY(HarshIntValidator)
    public:
        using QIntValidator::QIntValidator;
        State validate(QString & input, int & pos) const override{
            const State originalRes = QIntValidator::validate(input,pos);
            if(originalRes==Intermediate){
                const auto extracted = locale().toLongLong(input);
                if(extracted>0){
                    if(extracted>top() && -extracted<bottom())
                        return Invalid;
                }
                else if(extracted<bottom())
                    return Invalid;
            }
            return  originalRes;
        }
    };
    

    you can use it exactly as you use QIntValidator:

    int main(int argc, char *argv[])
    {
        QApplication a(argc, argv);
        QLineEdit w;
        HarshIntValidator valid(0,255);
        w.setValidator(&valid);
        w.show();
        return a.exec();
    }
    

  • Lifetime Qt Champion

    See also https://bugreports.qt.io/browse/QTBUG-76649 and other related bug reports why it's the way it is.


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