Check that the app runs for the first time - c++

Question

I'm new to qt mobile development and I have a rather dumb question.
How would I check whether a user runs the app for the first time (both Android and iOS)?
EDIT:
The reason I need this check is that I have an intro SwipeView for the first-timers and after it's read once it should always open the main app screen.
I've tried the way #TrebledJ suggested and it seems to work alright, Or is this stupid to do that in main.cpp?
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QSettings>
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
QSettings settings;
QVariant firstRun = settings.value("first-run");
QQmlApplicationEngine engine;
QUrl startingScreen(QStringLiteral("qrc:/main.qml"));
if(!firstRun.isValid())
settings.setValue("first-run", true);
else
startingScreen.setUrl(QStringLiteral("qrc:/start.qml"));
engine.load(startingScreen);
if (engine.rootObjects().isEmpty())
return -1;
return app.exec();
}

Answer 1

Use QSettings to check for a set value.
QSettings settings;
QVariant val = settings.value("first-time");
if (!val.isValid()) {
// ... first run
settings.setValue("first-time", false); // set a value so that the value is valid on the next run
} else {
// ... not first run
}
In QML, there is the Settings QML Type.
import Qt.labs.settings 1.0
Settings {
id: settings
property bool isFirstTime: true
}
Component.onCompleted: {
if (settings.isFirstTime) {
// ... first run
settings.isFirstTime = false;
} else {
// ... not first run
}
}
However, according to documentation:
Note: This type is made available by importing the Qt.labs.settings module. Types in the Qt.labs module are not guaranteed to remain compatible in future versions.
In consideration of the non-guarantee, Felgo/V-Play's API has a Storage QML Type which can also perform the check in QML. (The first example in their documentation implements this.)