Convert std::string to QString

Question

I've got an std::string content that I know contains UTF-8 data. I want to convert it to a QString. How do I do that, avoiding the from-ASCII conversion in Qt?

score 131 · Answer 1 · edited Apr 13 '18 at 09:33

131

QString::fromStdString(content) is better since it is more robust. Also note, that if std::string is encoded in UTF-8, then it should give exactly the same result as QString::fromUtf8(content.data(), int(content.size())).

edited Apr 13 '18 at 09:33

plasmacel

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answered Sep 01 '13 at 11:32

Jackpap

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Only in Qt5. In Qt4 it uses QString::fromAscii. – Rémi Benoit Mar 17 '16 at 09:12
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This should be the accepted answer. However your last statement is not necessarily true. In the C++ standard there is no guarantee, that `std::string` is encoded in UTF8 (actually the encoding is unspecified), so `QString::fromUtf8(content.data(), int(content.size()))` may give different (and also incorrect) results than `QString::fromStdString(content)`. – plasmacel Apr 13 '18 at 09:27

score 106 · Accepted Answer · edited May 02 '16 at 08:35

106

There's a QString function called fromUtf8 that takes a const char*:

QString str = QString::fromUtf8(content.c_str());

edited May 02 '16 at 08:35

leyyin

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answered Dec 02 '10 at 17:51

Michael Mrozek

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More efficient: `QString::fromUtf8( content.data(), content.size() )` – Marc Mutz - mmutz Apr 29 '11 at 21:22
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In the C++ standard there is no guarantee, that `std::string` is encoded in UTF8 (actually the encoding is unspecified), so this answer is not entirely correct. At least you should check the encoding by an assertion. – plasmacel Apr 13 '18 at 09:26

score 13 · Answer 3 · answered Jan 15 '19 at 09:42

13

Since Qt5 fromStdString internally uses fromUtf8, so you can use both:

inline QString QString::fromStdString(const std::string& s) 
{
return fromUtf8(s.data(), int(s.size()));
}

answered Jan 15 '19 at 09:42

maxa

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score 9 · Answer 4 · answered Sep 02 '15 at 12:34

Usually, the best way of doing the conversion is using the method fromUtf8, but the problem is when you have strings locale-dependent.

In these cases, it's preferable to use fromLocal8Bit. Example:

std::string str = "ëxample";
QString qs = QString::fromLocal8Bit(str.c_str());

Convert std::string to QString

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