different viewcontroller segue

Question

I want to my app can "auto" segue from ViewControll A to b, and b to c,(a,b,c is independent viewcontroller), so I did :

1. defined a timer at A_ViewController, can segue from A to B to C each one minute.

2. set segue at on storyBoard for ViewController A and B:

   A_ViewController : 'goToB' and 'goToC'

   B_ViewController : 'goToC'

3. and overwrite "overwrite func prepare(for segue:....." in A_ViewController.

Code:

class A_ViewController:  ViewController {

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

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "goToB" {
            let B_Controller = segue.destination as! B_ViewController
            B_ViewController.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)
    }
}

After run APP, first segue can done(Show ViewController B successfully), but after that, it always shows the error message as below :

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Receiver () has no segue with identifier 'goToC''

But I really set a segue 'goToC' on storyBoard. I do not know how to fix it. The code is already I modified from google search.

Answer 1

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.