[SOLVED] QString to const char *

[great88]

my code is like this :

@
QLineEdit textbox;
textBox.setText("QWERTY");
const char * mytext= textBox.text().toUtf8().constData();

QString mystring = QString::fromUtf8(mytext);
@

now mystring just equals "Q" .

Should it not be "QWERTY" ?

What am I doing wrong ?

[great88]

More to the point , I am using a 3rd party function that takes const char * as argument .

I only have the function interface not the implementation .

When I try to get a QString from the QLineEdit and convert it to const char * and feed it to the 3rd party function , the function fails to give proper output .
When I just feed the equivalent string literal to the function , the function gives correct output .

So something is wrong with the .toUtf8().constData() conversion from QString to const char * .
I think .

[MuldeR]

I think this code of your's is flawed:
@const char * mytext = textBox.text().toUtf8().constData();@

The toUtf8() function returns a QByteArray object containing the UTF8-converted string. And constData() returns a pointer to that QByteArray's internal buffer. But you don't keep the QByteArray object anywhere! So the temporary QByteArray is destroyed instantly - thus your pointer is dangling!

Try instead one of those:
@// --- Method #1 ---
const QByteArray byteArray = mytext = textBox.text().toUtf8();
const char *mytext = byteArray.constData();

// --- Method #2 ---
const char *mytext = strdup(textBox.text().toUtf8().constData());@

Don't forget free(mytest), if you use method #2 ;-)

--

From the docs:
[quote]const char * QByteArray::constData () const
Returns a pointer to the data stored in the byte array. The pointer can be used to access the bytes that compose the array. The data is '\0'-terminated unless the QByteArray object was created from raw data. The pointer remains valid as long as the byte array isn't reallocated or destroyed.[/quote]

[great88]

Thank you for explaining that . I tried your method 1 and it works .