Using UserDefaults in viewWillAppear - swift

Question

I'm setting up the Settings page (in SettingsView class) where users can set «On» / «Off» for the background parallax effect. The selection is saved in UserDefaults().string(forKey: "parallaxStatus"). In the viewWillAppear of ViewController class, I checked the parallaxStatus. If the status of the parallax effect is «On», then this effect is displayed. If the status is «Off», then nothing should happen.
The problem appeared when parallaxStatus changed from «On» to «Off» In this case, the parallax effect still displayed before I reload the View. But if parallaxStatus changed from «Off» to «On», the function works well without reloading the View.
Bellow is the code of viewWillAppear function. Thanks for any help or hint.
override func viewWillAppear(_ animated: Bool) {
let parallaxStatus = UserDefaults().string(forKey: "parallaxStatus")
if parallaxStatus == "On" {
let min = CGFloat(-40)
let max = CGFloat(40)
let xMotion = UIInterpolatingMotionEffect(keyPath: "layer.transform.translation.x", type: .tiltAlongHorizontalAxis)
xMotion.minimumRelativeValue = min
xMotion.maximumRelativeValue = max
let yMotion = UIInterpolatingMotionEffect(keyPath: "layer.transform.translation.y", type: .tiltAlongVerticalAxis)
yMotion.minimumRelativeValue = min
yMotion.maximumRelativeValue = max
let motionEffectGroup = UIMotionEffectGroup()
motionEffectGroup.motionEffects = [xMotion,yMotion]
bgImage.addMotionEffect(motionEffectGroup) } else { }
}

Answer 1

1- You should use a bool value in userDefaults
UserDefaults.standard.bool(forKey: "parallaxStatusOn") // default is false
2- viewWillAppear is called when you dimiss a presented / poped vc so in your case , you use a settingsView not vc verify it's being called by other KVO or any event driven notifier
3- if the state is on and changed to off , verify you remove the motion effects with if the vc is still appeared ( not deallocated btw do it in else of check )
bgImage.motionEffects.forEach { bgImage.removeMotionEffect($0) }