qtqlist

Save QList<int> to QSettings


I want to save a QList<int> to my QSettings without looping through it.
I know that I could use writeArray() and a loop to save all items or to write the QList to a QByteArray and save this but then it is not human readable in my INI file..

Currently I am using the following to transform my QList<int> to QList<QVariant>:

QList<QVariant> variantList;
//Temp is the QList<int>
for (int i = 0; i < temp.size(); i++)
  variantList.append(temp.at(i));

And to save this QList<Variant> to my Settings I use the following code:

QVariant list;
list.setValue(variantList);
//saveSession is my QSettings object
saveSession.setValue("MyList", list);

The QList is correctly saved to my INI file as I can see (comma seperated list of my ints)
But the function crashes on exit.
I already tried to use a pointer to my QSettings object instead but then it crashes on deleting the pointer ..


Solution

  • QSettings::setValue() needs QVariant as a second parameter. To pass QList as QVariant, you have to declare it as a Qt meta type. Here's the code snippet that demonstrates how to register a type as meta type:

    #include <QCoreApplication>
    #include <QDebug>
    #include <QMetaType>
    #include <QSettings>
    #include <QVariant>
    
    Q_DECLARE_METATYPE(QList<int>)
    
    int main(int argc, char *argv[])
    {
        QCoreApplication a(argc, argv);
    
        qRegisterMetaTypeStreamOperators<QList<int> >("QList<int>");
    
        QList<int> myList;
        myList.append(1);
        myList.append(2);
        myList.append(3);
    
        QSettings settings("Moose Soft", "Facturo-Pro");
        settings.setValue("foo", QVariant::fromValue(myList));
        QList<int> myList2 = settings.value("foo").value<QList<int> >();
        qDebug() << myList2;
    
        return 0;
    }