Path is wrong, what to do? - c++

Question

I'd like to write something to my path.
My code is following
QString Log::logPacketsPath = QDir::currentPath() + "/logs/Packets/";
int userID = 1;
QString text = "test 1 2 3";
QFile logPacketFile(logPacketsPath + "UserID: " + userID + " - " + QDateTime::currentDateTime().toString("dd.MM.yy") + ".log");
if (logPacketFile.open(QFile::WriteOnly | QFile::Text | QFile::Append))
{
QTextStream out(&logPacketFile);
out << "[" << QDateTime::currentDateTime().toString("dd.MM.yy, hh:mm:ss") << "]: " << text << "\n";
logPacketFile.close();
}
But it only creates the file named "UserID" with nothing in it.
Do you know where the mistake is?

Answer 1

I'm not sure which OS you're using, but ':' is invalid in a Windows filename.
Next, you should flush the QTextStream before closing the file:
out.flush();
logPacketFile.close();
or create additional scope:
{
QTextStream out(&logPacketFile);
out << "[" << QDateTime::currentDateTime().toString("dd.MM.yy, hh:mm:ss") << "]: " << text << "\n";
}
logPacketFile.close();
Also, as Chemobyl has pointed out, you can get into trouble by concatinating the int userID to your filepath. I'd suggest using string formatting to create the filename:
QString logPacketFile("%1UserID%2 - %3.log")
.arg(logPacketsPath)
.arg(userID)
.arg(QDateTime::currentDateTime().toString("dd.MM.yy"));

Answer 2

Convert int to QString:
Use QString::number().
Output with your current code:
"C:/.../logs/Packets/UserID [bad symbols here] - 17.11.14.log"
Output with
QFile logPacketFile(logPacketsPath + "UserID " + QString::number(userID) + " - " + QDateTime::currentDateTime().toString("dd.MM.yy") + ".log");//removed colon
is:
"C:/.../logs/Packets/UserID 1 - 17.11.14.log"
It is source of big troubles. See next:
int userID = 70;
QString text = "test 1 2 3";
QFile logPacketFile(logPacketsPath + "UserID " + userID + " - " + QDateTime::currentDateTime().toString("dd.MM.yy") + ".log");
Output:
.../UserID F - 17.11.14.log"
Note F, not a 70 because operator+ thought that you use simple char and 70 in char is F:
http://www.asciitable.com/
So I strongly suggest you to use QString::number to prevent errors.