How do I remove trailing whitespace from a QString?

Question

I want to remove all the trailing whitespace characters in a QString. I am looking to do what the Python function str.rstrip() with a QString

Answer 1

You can do it with a regexp:

#include <QtCore>

int main(int argc, char** argv)
{
    QCoreApplication app(argc, argv);

    QString str("Hello world    ");

    qDebug() << str;

    str.remove(QRegExp("\\s+$"));

    qDebug() << str;

    return 0;
}

Whether this would be faster, I'm not sure.

Answer 2

This is a variation of the answer posted by Frank S. Thomas:

QString rstrip(const QString& str, const char *skip = " \r\n\t") {
  int n = str.size() - 1;
  for (; n >= 0; --n) {
    if (0 == strchr(skip, str.at(n).toAscii()))
      return str.left(n + 1);
  }
  return "";
}

Answer 3

As far as I know, the only built-in-functions are trimmed() and simplified(). So you will need to trim manually. In that case you should use the QChar function isSpace() to check if a character is a space character.

Answer 4

QString provides only two trimming-related functions. In case if they don't suit your needs, I'm afraid you need to implement your own custom trimming function.

QString QString::simplified () const
Returns a string that has whitespace removed from the start and the end, and that has each sequence of internal whitespace replaced with a single space.

QString str = "  lots\t of\nwhitespace\r\n ";
str = str.simplified();
// str == "lots of whitespace";

QString QString::trimmed () const
Returns a string that has whitespace removed from the start and the end.

QString str = "  lots\t of\nwhitespace\r\n ";
str = str.trimmed();
// str == "lots\t of\nwhitespace"

Answer 5

If you don't have or don't need any whitespace at the beginning either, you could use QString QString::trimmed () const.

This ignores any internal whitespace, which is corrected by the alternative solution provided by Andrejs Cainikovs.

Answer 6

If you don't want to make a deep copy of the string:

QString & rtrim( QString & str ) {
  while( str.size() > 0 && str.at( str.size() - 1 ).isSpace() )
    str.chop( 1 );
  return str;
}