Convert any QVariant to QString

Question

I am aware of how to convert a QVariant containing a QString to a QString: How can I convert QVariant to QString and vice versa in Qt?

What I want to ask is how do I convert ANY QVariant into a QString? i.e. even if my QVariant object has an int, is there an easy way to convert it to QString?

You can use the toString() method as long as it is one of those types: http://doc.qt.io/qt-5/qvariant.html#toString otherwise, you can deduce if the type can be printed via http://doc.qt.io/qt-5/qvariant.html#canConvert-1 — DuKes0mE, Dec 15 '16 at 11:02
What will you use that string for? does it have to be human-readable? if so, what if the `QVariant` contains say a `QPixmap`/`QImage`? How would you make a `QString` out of that? — Mike, Dec 15 '16 at 11:44
Possible duplicate of [How can I convert QVariant to QString and vice versa in Qt?](http://stackoverflow.com/questions/7228826/how-can-i-convert-qvariant-to-qstring-and-vice-versa-in-qt) — Elcan, Dec 15 '16 at 12:59
@manatttta I did, but what you ask is exactly the same. Even if your QVariant is an int, it'll be output as a String. Only if you use custom classes it won't work. — Elcan, Dec 15 '16 at 14:27

score 16 · Answer 1 · answered Dec 15 '16 at 12:00

16

You can use QVariant::toString for types listed in the method documentation.

int value = 1;
QString s = QVariant(value).toString();

answered Dec 15 '16 at 12:00

talamaki

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e.jahandar · Answer 2 · 2016-12-15T12:19:42.960

2

You can use Qstring formating

QVariant qv(1);
QString str = QString ("%1").arg(qv.toInt());

also you it could be more generic like this

if(qv.typeName() == QString("QString"))
   str = QString("%1").arg(qv.toString());
else if(qv.typeName() == QString("int"));
   str = QString ("%1").arg(qv.toInt());
...

or by using qv.type()

if(qv.type() == QVariant::String)
    str = QString("%1").arg(qv.toString());
...

edited Dec 15 '16 at 12:19

answered Dec 15 '16 at 10:59

e.jahandar

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Thanks for the reply. However that is specific for `int` types. I meant all types! – manatttta Dec 15 '16 at 11:01
@manatttta i think you could write a function and iterate for all types, added an example. – e.jahandar Dec 15 '16 at 11:04
@Falcon I would rather use type() than typeName(), like "if(qv.type() == QVariant::String) etc. – talamaki Dec 15 '16 at 11:39
1

@e.jahandar , Never compare c strings using `==` use `strcmp` if you want to, see [this question](http://stackoverflow.com/q/4843640/2666212). In this case you can use `qv.type()` instead as suggested by @talamaki, this would be faster and more to the point. Please edit your answer – Mike Dec 15 '16 at 12:06
@Mike , its not c string, its Qstring with const char * , lookat documentation, http://doc.qt.io/qt-5/qstring.html the QString class has overloaded == operator – e.jahandar Dec 15 '16 at 12:09
1

@e.jahandar , [`QVariant::typeName()`](https://doc.qt.io/qt-5/qvariant.html#typeName) returns a `const char*` and you are comparing that with your string literal `"QString"` or `"int"`. Neither the LHS nor the RHS of the `operator==` is a `QString`. – Mike Dec 15 '16 at 12:13
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It'd be less overhead to use `QString::number(foo)` instead of `QString("%1").arg(foo)`. And simply do `str = qv.toString()`. Finally, instead of `QString("xyz")` prefer `QStringLiteral("xyz")` - it saves on runtime conversions from C string to QString. – Kuba hasn't forgotten Monica Dec 16 '16 at 00:06

Convert any QVariant to QString

2 Answers2