ViewDidLoad() not triggering background refresh

Question

So The community has been a great helping me along with a school project. However I've hit a snag. I'm building a simple Kitchen timer app thats a SVC with a tab view. The first page allows the user to set the timer, then the second is a basic settings page that allows the user to trigger a random background color I made to fulfill the requirements of the assignment. Everything is working great say for one part. Once the user triggers a random color to be used as a background, I wanted that background color to also be applied to the other views. I went with the advice I sought out here: Change viewController BG color based off another view controller and used singleton. However when I navigate from the settings view, to the timer view nothing happens. Now I added self.view.backgroundColor = Settings.sharedInstance.backgroundColor to my viewDidLoad() like so:

`override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    self.view.backgroundColor = Settings.sharedInstance.backgroundColor
    print(Settings.sharedInstance.backgroundColor)
}

` Nothing seems to happen. However! as a test, I added the same block to :

@IBAction func pickerStartButtonChnage(_ sender: UIButton) {

    self.view.backgroundColor = Settings.sharedInstance.backgroundColor
    print(Settings.sharedInstance.backgroundColor)

    if !cron.isValid{ // prevent more than one time on the thread
        nameIt.text = cronStr(cronCount)
        cron = Timer.scheduledTimer(timeInterval: timeInterval,
                               target: self,
                               selector: #selector(TimerViewController.timerDidEnd(_:)),
                               userInfo: "is done!",
                               repeats: true) //repeating timer in the second iteration
    }
}

It works! My question is why is the background not being triggered in the viewDidLoad(), when it works fine when the button is triggered? I appreciate any advice in advance, thank you.

Answer 1

Change the color in viewWillAppear() instead. viewDidLoad() happens when the view is first loaded into memory, but viewWillAppear() gets called every time it will appear.

override func viewWillAppear() {
    super.viewWillAppear()
    self.view.backgroundColor = Settings.sharedInstance.backgroundColor
}