QIntValidators dont work for me

nullbuil7

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

JonB

@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?

nullbuil7

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

SGaist

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 ?

JonB

@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.

nullbuil7

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

Xiao Yang

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

VRonin

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();
}

Christian Ehrlicher

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

DrewB

To limit 0 to 255 you can use QRegularExpressionValidator instead of QIntValidator

QRegularExpressionValidator* decValidator = new QRegularExpressionValidator(QRegularExpression("([01][0-9][0-9]|2[0-4][0-9]|25[0-5])"), decEdit);
decEdit->setValidator(decValidator);

JonB

@DrewB Does this behave any differently from the clearer QIntValidator?