How do I remove trailing whitespace from a QString?
Solution 1
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 "";
}
Solution 2
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"
Solution 3
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.
Solution 4
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.
Solution 5
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;
}
Di Zou
Updated on April 22, 2021Comments
-
Di Zou about 3 years
I want to remove all the trailing whitespace characters in a
QString
. I am looking to do what the Python functionstr.rstrip()
with aQString
.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.