Xcode Swift 3: Timer and Segue View Controller Error

Xcode Swift 3: Timer and Segue View Controller Error

Try this code:

Note: Code tested in Swift 3.

Step 1: First set storyboard Segue Identifier

Step 2:

   let emptyString = String() // Do nothing 

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

    Timer.scheduledTimer(timeInterval: 8.0, target: self, selector: #selector(timeToMoveOn), userInfo: nil, repeats: false)

    }

    func timeToMoveOn() {
    self.performSegue(withIdentifier: "goToMainUI", sender: self)
   }

   override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

    if (segue.identifier == "goToMainUI") {

    let dest = segue.destination as! viewTwo // viewTwo is your destination ViewController
    dest.emptyString = emptyString

        print("Segue Performed")

    }

}

In your ViewTwo add this above viewDidLoad method.

  var emptyString = String()

Xcode doesn't Recognise Timer()- Swift 3

Timer is a Swift 3 type, but judging from the rest of your method signatures, you appear to be using Swift 2. Use NSTimer in Swift 2.

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Also, for future reference, in addition to the timeInterval typo (which you've now fixed), the third parameter is selector, not selecter.

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So, in Swift 2:

NSTimer.scheduledTimerWithTimeInterval(8.0, target: self, selector: #selector(changeview), userInfo: nil, repeats: false)

Or in Swift 3:

Timer.scheduledTimer(timeInterval: 8.0, target: self, selector: #selector(changeview), userInfo: nil, repeats: false)

iOS Looking to delay segue between view controllers when button is pressed

Whenever you user performSegue method then you need to use like that

In the example with a 10 second delay

DispatchQueue.main.asyncAfter(deadline: .now() + 10.0, execute: {
   self.performSegue(withIdentifier: "segue", sender: self )
})

Updated

In this example with 5 second delay

DispatchQueue.main.asyncAfter(deadline:.now() + 5.0, execute: {
   self.performSegue(withIdentifier:"segue",sender: self)
})

Swift Timer.scheduledTimer() doesn't work

Timers don't work on background queues (without some sleight of hand involving creating run loops or manually scheduling it on an existing run loop). But you should never initiate any UI update from anything other than the main queue, anyway.

So, since you're calling performSegue from a URLSession completion closure (which runs on a background queue), it's actually running viewDidLoad from the background queue, too. Thus the attempt to schedule the timer is failing. To get around this, you have to manually dispatch the performSegue code to the main queue:

let task = URLSession.shared.dataTask(with: url!) { data, response, error in
    ...

    if isPassed != "null" {
        DispatchQueue.main.async {
            self.performSegue(withIdentifier: "gotoGame", sender: ...)
        }
    }
}

If you're ever unsure whether some code is running on the main queue or not, refer to the documentation. Or you can use a dispatch precondition:

dispatchPrecondition(condition: .onQueue(.main))

That way it will (in debug builds) stop the app if you've accidentally invoked the code from a background queue.

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Unrelated to your current problem, but as an aside, to avoid a strong reference cycle between the timer and the view controller, you generally want to keep a reference to the timer so that you can invalidate it when the view disappears (e.g. create timer in viewDidAppear and remove it in viewDidDisappear). Otherwise you can end up retaining the GameViewController after it was dismissed, e.g.:

class GameViewController: UIViewController {

    weak var timer: Timer?

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        timer = Timer.scheduledTimer(timeInterval: 1.0, target:self, selector: #selector(setCalculationLs(_:)), userInfo: nil, repeats: true)
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)

        timer?.invalidate()
    }

    @objc func setCalculationLs(_ timer: Timer) {
        print("Tick")
    }
}

Or in iOS 10 or later, you can use the block-based variant with weak reference to self, and invalidate in deinit:

class GameViewController: UIViewController {

    weak var timer: Timer?

    override func viewDidLoad() {
        super.viewDidLoad()

        timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { [weak self] timer in
            self?.setCalculationLs()
        }
    }

    deinit {
        timer?.invalidate()
    }

    func setCalculationLs() {
        print("Tick")
    }

}

Getting : Attempt to dismiss from view controller while a presentation or dismiss is in progress

simply use:-- dismiss(animated: true, completion: nil) and omit self

different viewcontroller segue

When you say B_Controller().goToC() you are creating a new instance of B_Controller, you aren't referring to the existing instance that was created by the goToB segue. Further, since your new instance of B_Controller isn't being created from the storyboard, it doesn't know anything about segues.

You need to store a reference to the instance of B_Controller that you are presenting in a property. Then you can use that property to invoke the goToC function.

class A_ViewController:  ViewController {

    var bController: B_Controller?

    ...//in Timer
       //first 1 minute
       performSegueWithIdentifier("goToB", sender: self)
       //second minute
       self.bController?.goToC()
    ...

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "goToB" {
            self.bController = segue.destination as! B_ViewController
            self.bController.msg = "From AtoB"
        }
        if segue.identifier == "goToSearchLocation" {
            let C_ViewController = segue.destination as! C_ViewController
            C_ViewController.msg = searchWord
            }
    }

class B_Controller:  ViewController {
    ...
    func goToC() {
       performSegueWithIdentifier("goToC", sender: self)
    }
}

You might want to re-design your code though; It would probably be cleaner to have a new timer in B that presents C rather than trying to use a single timer in A.

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