removing whitespaces from a QRegExpValidator - qt

Question

I have a code someone wrote and there
this->llBankCode = new widgetLineEditWithLabel(tr("Bankleitzahl"), "", Qt::AlignTop, this);
QRegExpValidator *validatorBLZ = new QRegExpValidator(this);
validatorBLZ->setRegExp(QRegExp( "[0-9]*", Qt::CaseSensitive));
this->llBankCode->lineEdit->setValidator(validatorBLZ);
as it can be seen from this code, is that validatorBLZ can accept only numbers between 0 and 9. I would like to change it, that validatorBLZ would be able to get as an input whitespace as well (but not to start with a whitespace), but it wont be shown.
Example:
if i try to copy & paste a string of the format '22 34 44', the result would be an empty field. What i would like to happen is that the string '22 34 44' will be shown in the field as '223444'.
How could i do it?

Answer 1

You could try using:
QString string = "22 34 44";
string.replace(QString(" "), QString(""));
That will replace any spaces with a non-space.

Answer 2

Write your own QValidator subclass and reimplement validate and fixup. Fixup does what you ask for: changes the input in a way that makes it intermediate/acceptable.
In your case, consider the following code-snippet for fixup:
fixup (QString &input) const
{
QString fixed;
fixed.reserve(input.size());
for (int i=0; i<input.size(); ++i)
if (input.at(i).isDigit()) fixed.append(input.at(i));
input = fixed;
}
(this is not tested)
The validate function will obviously look similar, returning QValidator::Invalid when it encounters a non-digit character and returning the according position in pos.
If your BLZ is limited to Germany, you could easily add the validation feature that it only returns QValidator::Acceptable when there are eight digits, and QValidator::Intermediate else.
Anyhow, writing an own QValidator, which often is very easy and straight forward, is the best (and most future-proof) solution most of the time. RegExes are great, but C++ clearly is the more powerful language here, which in addition results in a much more readable validator ;).