How to convert int to QString?
Solution 1
Use QString::number()
:
int i = 42;
QString s = QString::number(i);
Solution 2
And if you want to put it into string within some text context, forget about +
operator.
Simply do:
// Qt 5 + C++11
auto i = 13;
auto printable = QStringLiteral("My magic number is %1. That's all!").arg(i);
// Qt 5
int i = 13;
QString printable = QStringLiteral("My magic number is %1. That's all!").arg(i);
// Qt 4
int i = 13;
QString printable = QString::fromLatin1("My magic number is %1. That's all!").arg(i);
Solution 3
Moreover to convert whatever you want, you can use QVariant
.
For an int
to a QString
you get:
QVariant(3).toString();
A float
to a string
or a string
to a float
:
QVariant(3.2).toString();
QVariant("5.2").toFloat();
Solution 4
Yet another option is to use QTextStream and the <<
operator in much the same way as you would use cout
in C++:
QPoint point(5,1);
QString str;
QTextStream(&str) << "Mouse click: (" << point.x() << ", " << point.y() << ").";
// OUTPUT:
// Mouse click: (5, 1).
Because operator <<()
has been overloaded, you can use it for multiple types, not just int
. QString::arg()
is overloaded, for example arg(int a1, int a2)
, but there is no arg(int a1, QString a2)
, so using QTextStream()
and operator <<
is convenient when formatting longer strings with mixed types.
Caution: You might be tempted to use the sprintf()
facility to mimic C style printf()
statements, but it is recommended to use QTextStream
or arg()
because they support Unicode string
s.
Solution 5
I always use QString::setNum()
.
int i = 10;
double d = 10.75;
QString str;
str.setNum(i);
str.setNum(d);
setNum()
is overloaded in many ways. See QString
class reference.
Ahmad
Updated on October 07, 2021Comments
-
Ahmad over 2 years
Is there a
QString
function which takes an int and outputs it as aQString
? -
x29a almost 9 yearsSince you mention the
+
operator, careful around integers, since it might very well work but internally, theoperator+(const QString &s, char c)
implementation is called, and the string wont contain the integer as number but itsQChar::fromAscii(c)
equivalent -
David Sánchez over 8 yearsSince you mention the + operator, you can actually do it, but understanding whats happening: QString p = s + QString::number(1); being s a QString works perfectly. So, basically QString + QString is okay, QString + int bad.
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Eliyahu Skoczylas almost 8 yearsUnfortunately, the link to the Nokia site no longer works.
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Zeks about 7 yearsHere's the more interesting question: is there a faster way? I have encountered a problem where this version almost takes more time than the entire processing afterwards...
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Georg Fritzsche about 7 yearsThen you probably want to work on pre-allocated buffers... but this sounds like a separate question.
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mr3 almost 7 yearsCall me nuts, but I'd get more use out of the question as "How to convert a number to QString?", this as the main answer for lightweight conversions, and the other answers for special treatments.