How to manage instantiated viewControllers

Question

To summarise, how best is it to manage VC's?

In my case, I have 3 VC's in my game. To switch between them a button in the present VC activates the following code:

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let viewController = storyboard.instantiateViewController(withIdentifier:"firstLevel")
self.present(viewController, animated: false, completion: nil)

This code works, but each time it instantiates a new VC which causes issues in my game for global variables such as "Score" when there are two copies of the same VC and Im assuming this is really bad for memory also.

What is the best solution to this problem?

Should I dismiss the present viewController by placing the following line of code after I have instantiated the next VC?:

self.dismissViewControllerAnimated(false, completion: nil)

Quick question: what does your navigation look like? Is it like a next / previous scheme, or tabs at the bottom etc.? — m_katsifarakis, Dec 28 '18 at 16:19
The first VC is a homescreen - so it has buttons such as continue game, new game etc, the second VC is level 1 and you return to the first VC by swiping upwards. I noticed an issue when I would press continue to return to the second VC and timer started counting down twice as fast (the timer value is a global function so I am assuming two instances of the second VC are causing this) — GarrisRyder, Dec 28 '18 at 16:25

Shehata Gamal · Accepted Answer · 2018-12-28T16:17:56.260

1

You need to have only 1 vc by replacing rootViewController

 let viewController = storyboard!.instantiateViewController(withIdentifier:"firstLevel")
(UIApplication.shared.delegate as! AppDelegate).window!.rootViewController = viewController

As your current code leaves old vcs in the stack which for sure will cause memory issues

edited Dec 28 '18 at 16:17

answered Dec 28 '18 at 16:13

Shehata Gamal

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Thanks for the respone! So what does this rootViewController do? – GarrisRyder Dec 28 '18 at 16:17
it makes 1 vc presented at any time – Shehata Gamal Dec 28 '18 at 16:18
does it remove repeated instances of the same VC class? Ive replaced the code and Im getting the same issue. – GarrisRyder Dec 28 '18 at 16:27
when you return to the home vc it will be only the presented 1 – Shehata Gamal Dec 28 '18 at 16:28
Add a print message inside `deinit` vc method to verify it's deallocation after you run the above code – Shehata Gamal Dec 28 '18 at 16:29
Oh okay, but when I go from the home VC back to the first level VC, how do I avoid creating another instance of the first level VC? – GarrisRyder Dec 28 '18 at 16:30
you'll have to create another instance , as when you go back to home from level 1 vc is deallocated – Shehata Gamal Dec 28 '18 at 16:33
home vc deinit runs but first level vc deinit does not – GarrisRyder Dec 28 '18 at 16:50
that means you have a strong reference inside the level vc may be timers or any strong self link – Shehata Gamal Dec 28 '18 at 16:55
As you said, deactivating the timer in viewDidDisappear solved the countdown issue, thanks! but despite this deinit isnt being called so it must be a strong self link – GarrisRyder Dec 28 '18 at 17:00
could this issue be due to using global variables defined in a .swift file inside my class? – GarrisRyder Dec 28 '18 at 17:13

How to manage instantiated viewControllers

1 Answers1