CODEWITHSUNDEEP
qtseed
YeP
YeP

Reputation: 211

how to reseed qrand() in Qt?

I use this the generate random string in Qt:

GenerateRandomString()
{
const QString possibleCharacters("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789");
const int randomStringLength = 5; // assuming you want random strings of 5 characters

QString randomString;
for(int i=0; i<randomStringLength; ++i)
{
   int index = qrand() % possibleCharacters.length();
   QChar nextChar = possibleCharacters.at(index);
   randomString.append(nextChar);
}
return randomString;
}

however the strings it generates repeat every time I start the debug (or run the program). It seems like qrand() is seeded the same every time. How can I properly reseed qrand() so that it is more random? Thank you.

Upvotes: 0

Views: 2245

Answers (2)

Mr. Developerdude
Mr. Developerdude

Reputation: 9668

As an alternative to @Yep's answer, since QDateTime::toTime_t() is deprecated since Qt5.8, the following will work just as well:

qsrand(QDateTime::currentMSecsSinceEpoch()%UINT_MAX);

Upvotes: 1

YeP
YeP

Reputation: 211

I found a solution... I add this to the constructor so the program is seeded differently every time. It works for my purpose.

QDateTime cd = QDateTime::currentDateTime();
qsrand(cd.toTime_t());

Upvotes: 3

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