[SOLVED] Convert Qstring to char* and back

saeedhardan

why is it so hard to do so ?
!http://i57.tinypic.com/2yynk9i.png(example)!

i tried also :
1 - str.toStdString().c_str(); but returns const char .
2 - str.toLocal8Bit().data(); (same trash as utf8 see below )

in the image you see ip which qstring (1.1.1.1), in function ipValid() i convert it to char* str .
you can see in the value of str to the right of the image (debugging mode) ,which is trash .

dheerendra

Not sure what sure what you are trying to achieve. Here is simple one based on your question.

QString data("1.1.1.1");
qDebug() << data;
char *datachar = data.toLocal8Bit().data();
qDebug() << datachar;

qDebug() << QString(datachar);

If you want break the string based on "." you can use QString.split as well.

SGaist

Hi,

To add to Dheerendra, if you really want to validate an IP address, you should rather use a regular expression.

If it comes from a user through a QLineEdit, you can also use a validator to ensure the user is only entering correct data.

saeedhardan

thanks for tips on validating ip , but this isn't the only place i need to convert qstring to char* .

[quote author="Dheerendra" date="1408982078"]Not sure what sure what you are trying to achieve. Here is simple one based on your question.

char *datachar = data.toLocal8Bit().data();

[/quote]

i tried this method , but it doen't convert right , when i do :
char* str = ip.toLocal8Bit().data(); (ip=1.1.1.1)
str isn't 1.1.1.1 , see picture value of str .

dheerendra

Are you taking about Quotes ? which are sorounding the string ? These quotes are not part of string.

Here is the output of my program.

"1.1.1.1"
1.1.1.1
"1.1.1.1"

saeedhardan

this is the output on my machine :
!http://i58.tinypic.com/j7f7d3.png(output)!

is there something wrong with my qt ? i dont understand im new to qt so sorry if its a silly mistake

dheerendra

which platform ?

saeedhardan

windows 8.1 32bit

Qt Creator 3.1.2 Based on Qt 5.3.1 (MSVC 2010, 32 bit)

cincirin

QString::toLocal8Bit::data construct a temporary QByteArray object which will be destroyed and hence you got "bullshit" datachar contents.
QByteArray ba = data.toLocal8Bit();
char* datachar = ba.data();
In this way ba object will be destroyed on function exit

andreyc

I think qDebug() tries to be smart.
Try to use std::cout instead.

saeedhardan

[quote author="cincirin" date="1408986595"]QString::toLocal8Bit::data construct a temporary QByteArray object which will be destroyed and hence you got "bullshit" datachar contents.
QByteArray ba = data.toLocal8Bit();
char* datachar = ba.data();
In this way ba object will be destroyed on function exit[/quote]

thank you very much sir , you r right

andreyc

@
void barStd()
{
QString ip = "1.1.1.1";
qDebug() << "ip =" << ip;
char* localdata = ip.toLocal8Bit().data();
std::cout << "std::cout char* localdata = " << localdata << std::endl;
}

void barqDebug()
{
QString ip = "1.1.1.1";
qDebug() << "ip =" << ip;
char* localdata = ip.toLocal8Bit().data();
qDebug() << "qDebug() char* localdata = " << localdata;
}
@

and output
@
ip = "1.1.1.1"
qDebug() char* localdata =
ip = "1.1.1.1"
std::cout char* localdata = 1.1.1.1
@