How to detect a first app launching and display an instruction screen? - swift

Question

I am developing a walkthrough screen which should appear only the first time when the user opens the app. So far I created the walkthrough page and PageViewController.
See the picture:
I read lots of similar questions here and I understood that I have to use
UserDefaults()
inside the AppDelegate, but I didn't understand how to use the class and storyboard names inside the code.
Basically, when the app is opened for the first time, the PageViewController should appear on the screen and when the user clicks on the start button, which is on the WalkThroughScreen it will dismiss the tutorial page and the app will start.
I have tried this code:
if let isFirstStart = UserDefaults.standard.value(forKey: "isFirstLaunch") as? Bool {
if defaults.bool(forKey: "isFirstLaunch") {
defaults.set(false, forKey: "isFirstLaunch")
let mainStoryboard = UIStoryboard(name: "WalkThroughScreen", bundle: Bundle.main)
let vc : WalkThroughScreen = mainStoryboard.instantiateViewController(withIdentifier: "PageViewController") as! WalkThroughScreen
self.present(vc, animated: true, completion: nil)
}
I am pretty sure that it is a complete mess, because I didn't understand it very good and I haven't used the TutorialPage, so I will be very thankful if someone leave me hints or example how to do it correctly

Answer 1

Yes you are right, you have to use userDefaults to achieve this. And you have to do it inside appDelegate()
Roel Koops answer should do it but you can try it like this also:
let launchedBefore = UserDefaults.standard.bool(forKey: "launchedBefore")
if launchedBefore {
print("This is not first launch.")
} else {
print("This is first launch.")
UserDefaults.standard.set(true, forKey: "launchedBefore")
UserDefaults.standard.synchronize()
let mainStoryboard = UIStoryboard(name: "Main", bundle: Bundle.main)
let vc : WalkThroughScreen = mainStoryboard.instantiateViewController(withIdentifier: "WalkThroughScreen") as! WalkThroughScreen
self.present(vc, animated: true, completion: nil)
}
And make sure to declare: let userDefaults = UserDefaults.standard and use it inside didFinishLaunchingWithOptions.
There are even more solutions so I give you one more:
let userDefaults = UserDefaults.standard
if !userDefaults.bool(forKey: "launchedBefore") {
let mainStoryboard = UIStoryboard(name: "Main", bundle: Bundle.main)
let vc : WelcomeViewController = mainStoryboard.instantiateViewController(withIdentifier: "WalkThroughScreen") as! WelcomeViewController
self.window?.makeKeyAndVisible()
self.window?.rootViewController?.present(vc, animated: false, completion: nil)
userDefaults.set(true, forKey: "launchedBefore")
userDefaults.synchronize()
}
You can even declare all the storyboard thing in one line:
self.window?.rootViewController = self.storyboard?.instantiateViewController(withIdentifier: "WalkThroughScreen")
But this assumes that you declare 2 variables:
var window: UIWindow?
var storyboard: UIStoryboard?
If it didn't work just tell me, I am gonna try to help.

Answer 2

The code in your if-block is never executed if the key "isFirstLaunch" doesn't exist.
Try this:
if let isFirstStart = UserDefaults.standard.value(forKey: "isFirstLaunch") as? Bool {
print("this is not the first launch")
} else {
print("this is the first launch")
UserDefaults.standard.set(false, forKey: "isFirstLaunch")
UserDefaults.standard.synchronize()
let mainStoryboard = UIStoryboard(name: "Main", bundle: Bundle.main)
let vc : WalkThroughScreen = mainStoryboard.instantiateViewController(withIdentifier: "WalkThroughScreen") as! WalkThroughScreen
self.present(vc, animated: true, completion: nil)
}