Why are there double quotes when we print using QString? - qt

Question

I am using Qt framework in Linux and a complete beginner.
When I print a simple message like:
qDebug() << "Hello World";
In the Console the output is Hello World.
But if I print the same message like:
QString str = "Hello World";
qDebug() << str;
In the Console the output is "Hello World",(Notice the quotes), How to get the same output using QString?

Answer 1

See QDebug::noquote
Disables automatic insertion of quotation characters around QChar, QString and QByteArray contents and returns a reference to the stream.
When quoting is disabled, these types are printed without quotation characters and without escaping of non-printable characters.
This function was introduced in Qt 5.4.
Usage:
QString str = "Hello World";
qDebug().noquote() << str;
http://doc.qt.io/qt-5/qdebug.html#noquote

Answer 2

you can find the answer in the Qt source code(detail of implementation in the link below) :
https://code.woboq.org/qt5/qtbase/src/corelib/io/qdebug.h.html
you have several definitions of the << operator
from Qt source code :
/*! \fn QDebug &QDebug::operator<<(const char *s)
Writes the
'\0'-terminated string s, to the stream and returns a reference
to the stream. The string is never quoted nor transformed to the
output, but note that some QDebug backends might not be 8-bit clean.
/ /! \fn QDebug &QDebug::operator<<(const QString &s)
Writes the string, \a s, to the stream and returns a reference to the stream.
Normally, QDebug prints the string inside quotes and transforms
non-printable characters to their Unicode values (\u1234). To print
non-printable characters without transformation, enable the noquote()
functionality. Note that some QDebug backends might not be 8-bit
clean. Output examples: \code QString s; s = "a"; qDebug().noquote()
<< s; // prints: a qDebug() << s; // prints: "a" s = "\"a\r\n\"";
qDebug() << s; // prints: "\"a\r\n\"" s = "\033"; // escape character
qDebug() << s; // prints: "\u001B" s = "\u00AD"; // SOFT HYPHEN
qDebug() << s; // prints: "\u00AD" s = "\u00E1"; // LATIN SMALL LETTER
A WITH ACUTE qDebug() << s; // prints: "á" s = "a\u0301"; // "a"
followed by COMBINING ACUTE ACCENT qDebug() << s; // prints: "aÌ"; s =
"\u0430\u0301"; // CYRILLIC SMALL LETTER A followed by COMBINING ACUTE
ACCENT qDebug() << s; // prints: "аÌ" \endcode
*/
qDebug()<< "hello world" uses QDebug &QDebug::operator<<(const char *s) and not QDebug &QDebug::operator<<(const QString &s) that's why you get the quotes in one version and not the other.
you can get the same result by using :
qDebug().noquote() << s;
on the QString version