How to set Input Mask and QValidator to a QLineEdit at a time in Qt?

Question

I want a line edit which accepts an ip address. If I give input mask as:

ui->lineEdit->setInputMask("000.000.000.000");

It is accepting values greater than 255. If I give a validator then we have to give a dot(.) after every three digits. What would the best way to handle it?

Answer 1

It is accepting value greater than 255.

Absolutely, because '0' means this:

ASCII digit permitted but not required.

As you can see, this is not your cup of tea. There are at least the following ways to circumvent it:

• Write a custom validator

• Use regex

• Split the input into four entries and validate each entry on its own while still having visual delimiters between the entries.

The regex solution would be probably the quick, but also ugliest IMHO:

QString ipRange = "(?:[0-1]?[0-9]?[0-9]|2[0-4][0-9]|25[0-5])";
// You may want to use QRegularExpression for new code with Qt 5 (not mandatory).
QRegExp ipRegex ("^" + ipRange
                 + "\\." + ipRange
                 + "\\." + ipRange
                 + "\\." + ipRange + "$");
QRegExpValidator *ipValidator = new QRegExpValidator(ipRegex, this);
lineEdit->setValidator(ipValidator);

Disclaimer: this will only validate IP4 addresses properly, so it will not work for IP6 should you need that in the future.