如何在首次启动时仅显示一次UIPageViewController

Question

I want to show a tutorial that is a UIPageView only once at the beginning of the first launch.

I am attempting this using this code

let launchedBefore = UserDefaults.standard.bool(forKey: "launchedBefore")
    if launchedBefore  {
        performSegue(withIdentifier: "tutorialtohome1", sender: nil)
    }
    else {
        UserDefaults.standard.set(true, forKey: "launchedBefore")
    }

For some reason it's not working with the UIPageController, it works fine with other views.

Just to make clear, I only want this view to appear once, then never again, as it acts as a tutorial.

Any suggestions?

Thanks

Answer 1

You need to check the OBJECT. Not the bool. This is better way to do it. On first run, there are no such key "lauchedBefore". You cannot check boolean value of what's not there.

let launchedBefore = UserDefaults.standard.object(forKey: "launchedBefore")

    if (launchedBefore==nil)  {
        performSegue(withIdentifier: "tutorialtohome1", sender: nil)
        UserDefaults.standard.set(true, forKey: "launchedBefore")
    }
    else {
        // already launched, so do nothing.
    }