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.

I did some Googling, and found this: http://www.qtforum.org/article/20798/how-to-strip-trailing-whitespace-from-qstring.html

So what I have right now is something like this:

while(str.endsWith( ' ' )) str.chop(1);
while(str.endsWith( '\n' )) str.chop(1);

Is there a simpler way to do this? I want to keep all the whitespace at the beginning.

Answer 1

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 2

QString has two methods related to trimming whitespace:

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

If you want to remove only trailing whitespace, you need to implement that yourself. Here is such an implementation which mimics the implementation of trimmed:

QString rstrip(const QString& str) {
  int n = str.size() - 1;
  for (; n >= 0; --n) {
    if (!str.at(n).isSpace()) {
      return str.left(n + 1);
    }
  }
  return "";
}

Answer 3

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 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

No deep copy and no repeated calls to size/chop:

QString & rtrimInPlace (QString &str) {
    for (int n = str.size() - 1; n >= 0; -- n)
        if (!str.at(n).isSpace()) {
            str.truncate(n + 1);
            break;
        }
    return str;
}