QFile: new file name append to tho last saved - qt

Question

I'm looking for the error I made on this code, but I can not find any solution since hours..
This function should simpli save a file to a directory:
void MyClass::saveSettingsToFile(QString file_name)
{
QString path;
path = dir.append(file_name);
QFile my_file(path);
if (!my_file.open(QFile::WriteOnly))
{
qDebug() << "Could not open file for writing";
}
QTextStream out(& my_file);
out << "some text \n"
my_file.flush();
my_file.close();
path = "";
file_name ="";
}
Where dir is a QString containing the directory, file_name is gathered from a lineEdit field.
When I first call the function with, for example file_name = "aaaa.txt", I find this aaaa.txt in the specified directory. All right.
When then I call again the function with file_name = "bbbb.txt", I find in the specified directory this file: aaaa.txtbbbb.txt, instead of I
bbbb.txt
It seems to me a very s****d error, but I cannot find what!
EDITED: there was this mistake QTextStream out(& path); instead of QTextStream out(& my_file);

Answer 1

You are modifying dir variable with QString::append. Variable dir is obviously a class member of MyClass. Try this instead:
void MyClass::saveSettingsToFile(QString file_name)
{
QString path(dir);
path.append(file_name);
QFile my_file(path);
//...
}

Answer 2

The QString::append function modify the parameter value itself as you can see in the documentation: http://doc.qt.io/qt-5/qstring.html#append
Example:
QString x = "free";
QString y = "dom";
x.append(y);
// x == "freedom"
So, what happens is that it keeps appending the content to the dir variable, not only assigning the result to path.