QT Creator Error (no match for operator =)

Question

I'm receiving this error everytime I build my code. I'm using QT Creator 3.1, (5.2.1 build)

error: no match for 'operator+' (operand types are 'QStringList' and 'const char [2]')

Here is a snippet of code, hope it can help (the asterix line is where the error is highlighted)

int main(int argc, char *argv[])
{
Shutdown = false;

QApplication a(argc, argv);
a.setApplicationName("aQtLow");

//Create default data paths if they don't exist
QDir Path;
**MainPath = QStandardPaths::standardLocations(QStandardPaths::HomeLocation) + "/" + a.applicationName() + "Data";**
Path.setPath(MainPath);

Answer 1

The problem is that you are trying to concatenate a QStringList with QStrings since

QStandardPaths::standardLocations(QStandardPaths::HomeLocation)

returns a QStringList.

You would need to gt the element you wish to reuse, e.g. using the .first() method. You could write this:

MainPath = QStandardPaths::standardLocations(QStandardPaths::HomeLocation).first() + "/" + a.applicationName() + "/Data";

Note that I just added a missing "/" between the application name and the "Data" because I think that would be more logical to use, but feel free to reject that edit if you wish.

But since you seem to be interested in the data directory location, I would suggest to use the dedicated enum from QStandardPaths:

or it would be even better to just use:

QStandardPaths::DataLocation 9 Returns a directory location where persistent application data can be stored. QCoreApplication::organizationName and QCoreApplication::applicationName are appended to the directory location returned for GenericDataLocation.

You could write this then:

QDir Path(QStandardPaths::standardLocations(QStandardPaths::DataLocation).first());

In fact, if you wish to avoid the .first() call, you could probably use the writableLocation() method as follows:

QDir Path(QStandardPaths::writableLocation(QStandardPaths::DataLocation));

=====================================================

Out of curiosity, this could also be an alternative:

QString QDir::homePath () [static]

or

QDir QDir::home () [static]

as follows:

QDir Path = QDir::home();
Path.cd(a.applicationName() + "Data");

or

QDir Path(QDir::homePath() + "/" + a.applicationName() + "/Data");

If that is not enough, there is even one more alternative:

QDir Path(QCoreApplication::applicationDirPath + "/Data");

Answer 2

QStandardPaths::standardLocations return QStringList. You should use QStringList::join or QStringList::at or use foreach. Mb you want to do something else but I don`t know what because variable MainPath so mysterious =)