How to obtain const char * from QString

Question

I have read a string in from an XML file with UTF8 encoding. I store this value in a QString object and concatenate it with some other information. I can see in the QtCreator debugger that the QString holds the desired value.

I need to pass this string to another library that takes a const char * argument. How do I obtain the const char * please? I've tried toLocal8bit(), toLatin1(), toUtf8() all with no luck. Seems like I am missing something...

http://stackoverflow.com/questions/4214369/how-to-convert-qstring-to-stdstring — Min Lin, Sep 25 '13 at 04:06
@MinLin: that thread is about std string, *not* const char*. — László Papp, Sep 25 '13 at 06:41
@LaszloPapp Well, in the answer the rvalue is const char*, just implicitly converted to the lvalue which is a std string — Min Lin, Sep 25 '13 at 06:45
@MinLin: std::string and QString should not be mixed IMO as it is not necessary. Hence, that is a different use case, so a different question. It is better to go through qt types without mixing std in. See my answer below. — László Papp, Sep 25 '13 at 06:47
@LaszloPapp Well, your answer is correct. What I mean is that in that post though it wants a std string, the right hand side is a const char*, and I think readers of that post should be able to figure out. — Min Lin, Sep 25 '13 at 10:21
Possible duplicate of [QString to char\* conversion](https://stackoverflow.com/questions/2523765/qstring-to-char-conversion) — Ben Jones, Jul 27 '18 at 20:46

score 10 · Accepted Answer · edited Jul 27 '18 at 20:04

I need to pass this string to another library that takes a const char * argument. How do I obtain the const char * please? I've tried toLocal8bit(), toLatin1(), toUtf8() all with no luck. Seems like I am missing something...

Because if you try those, you only get a QByteArray back as opposed to a const char*. You could use the constData() method on the QByteArray you got that way, and then you will have the desired result.

Mixing std::string and QString is not necessary, hence it is better to go through the qt types (QString -> QByteArray -> const char*) without introducing std::string in here.

Where you use toLocal8bit(), toLatin1() or toUtf8() depends on your encoding, so that is a different question to the main one in here. They will all return a QByteArray to you.

Note: you should avoid using toAscii() though as that is deprecated in Qt 5 for good.

How to obtain const char * from QString

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