QString to char* not converting

[jacek]

I don't see why the byte array should be deleted here since it (or it's pointer) is still in scope, no?

The pointer is in scope, but the temporary QByteArray isn't. QString::toLatin1() returns a completely new QByteArray object --- not some reference to an internal buffer. On the other hand QByteArray::data() returns a pointer to internal data of that QByteArray, so if it gets destroyed, that pointer will be invalid.

The QByteArray help says, "QByteArray makes a deep copy of the const char * data, so you can modify it later without experiencing side effects", so shouldn't it be available to me to display?

It also says:

The pointer remains valid as long as the byte array isn't reallocated.

You should use QString::toLatin1() this way:

QString str( "some string" );
QByteArray ba( str.toLatin1() );
char *cstr = ba.data(); // you can use cstr as long as ba exist

QString str( "some string" );
QByteArray ba( str.toLatin1() );
char *cstr = ba.data(); // you can use cstr as long as ba exist

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but you do it like this:

char *cstr = str.toLatin1().data(); // wrong

char *cstr = str.toLatin1().data(); // wrong

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this uses a temporary QByteArray that ceases to exist immediately, so the workaround is to copy that string:

char *cstr = qstrdup( str.toLatin1().data() ); // ok, but remember to delete cstr

char *cstr = qstrdup( str.toLatin1().data() ); // ok, but remember to delete cstr

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[DPinLV]

Jacek,

That clears some things up, thanks, you've been a great help.

Derrick

[lum]

const char * data () const (obsolete)

[jacek]

const char * data () const (obsolete)

It was available in Qt3, but this thread is about Qt4.