CODEWITHSUNDEEP
c++qstring
SPlatten
SPlatten

Reputation: 5758

Qt QString toInt() fails

I have a 'QString' containing "-3.5", however if I try to convert this to an integer using the 'toInt' method it returns 0. Why?

    QString strTest = "-3.5";
    int intTest = strTest.toInt();

    qDebug() << intTest;

intTest will be 0 ?

Upvotes: 3

Views: 8363

Answers (2)

krzaq
krzaq

Reputation: 16421

As opposed to std::stoi and streams from the standard library, Qt strings require the whole string to be a valid integer to perform the conversion. You could use toDouble instead as a workaround.

You should also use the optional ok parameter to check for errors:

QString strTest = "-3.5";
book ok;
int intTest = strTest.toInt(&ok);
if(ok) {
    qDebug() << intTest;
} else {
    qDebug() << "failed to read the string";
}

Upvotes: 6

Ami Tavory
Ami Tavory

Reputation: 76297

If you look at the documentation, it says

Returns 0 if the conversion fails.

You should use

bool ok;
strTest.toInt(&ok);

and then check the value of ok - otherwise, you won't be sure if the 0 is the actual value, or an indication of failure.

In this case it's failing because it is not actually an integer (it has a decimal point). Note that you can use toDouble (and check ok there too!), and then cast the result as you see fit.

QString strTest = "-3.5";

bool ok;
double t = strTest.toDouble(&ok);

if(ok)
    qDebug() << static_cast<int>(t);

Upvotes: 5

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