output QString

Weichao Wang

Dear all,
For QString str,
cout << str;
produces error while compiling, and one must use str.toStdString(), but
QTextStream << str.toStdString();
produces error, and one must use str (without .toStdString()). What's the reason that Qt is designed this way? Is it not possible to design QString this way so that cout and QTextStream would have the same syntax?
Weichao

aha_1980

@Weichao-Wang

Try this:

QTextStream output(stdout);
QString str = "Hello World";

output << str;

Weichao Wang

@aha_1980
You mean that this way we can avoid using cout so that file and console output would behave the same way?
Weichao

jsulm

@Weichao-Wang said in output QString:

Is it not possible to design QString this way so that cout and QTextStream would have the same syntax?

You can implement this:

std::ostream&  operator <<(std::ostream &stream,const QString &str)
{
   stream << str.toAscii().constData(); //or: stream << str.toStdString(); //??
   return stream;
}

See https://stackoverflow.com/questions/16281014/operator-for-qstring

Weichao Wang

Thank you all!
Weichao

aha_1980

@jsulm said in output QString:

stream << str.toAscii().constData();

toAscii() is deprecated, use toLatin1() instead.

@Weichao-Wang

However, note that QString is an Unicode string, using toLatin1() will only work for letters in the Latin-1 encoding range. Most likely toUtf8() or toLocal8Bit() will be the better solution.

jsulm

@aha_1980 I just copy pasted the code from the link above :-) I did this just to show the direction. But yes, because people often just copy paste code from forum it is good you corrected the issues in the code!

JKSH

@Weichao-Wang said in output QString:

What's the reason that Qt is designed this way?

std::string has a terrible design. I am glad that QString is designed differently, because QString is much more powerful and easy to use.