Does 'pushViewController' Prevent the ViewController from Calling deinit? - ios

Question

I have several view controllers (UIViewController). Each view controller has its own storyboard. And I want the app to call deinit when it transitions from one view controller to another. But it won't.
The app starts with HomeViewController. And it will transition to SelectViewController when the user taps a button (UIButton).
class HomeViewController: BasicViewController {
#IBAction func selectTapped(_ sender: UIButton) {
let storyboard = UIStoryboard(name:"Select",bundle:nil)
let controller = storyboard.instantiateViewController(withIdentifier: "SelectView") as! UINavigationController
let viewController = controller.topViewController as! SelectViewController
self.navigationController?.pushViewController(viewController, animated: true)
}
deinit {
print("HOME HAS BEEN REMOVED FROM MEMORY")
}
}
The app never calls deinit when it leaves HomeViewController. I wonder if that's because it's pushing a view controller? If I set the view controller as follows, the app will crash. What am I doing wrong? I have never done it with different storyboards. Thanks.
class HomeViewController: BasicViewController {
#IBAction func selectTapped(_ sender: UIButton) {
let storyboard = UIStoryboard(name:"Select",bundle:nil)
let viewController = storyboard.instantiateViewController(withIdentifier: "SelectView") as! SelectViewController
self.navigationController?.setViewControllers([viewController], animated: true)
}
}
UPDATE 1
I guess it's just the following.
#IBAction func selectTapped(_ sender: UIButton) {
let storyboard = UIStoryboard(name:"Select",bundle:nil)
let controller = storyboard.instantiateViewController(withIdentifier: "SelectView") as! UINavigationController
self.present(controller, animated: true, completion: nil)
}
UPDATE 2
I also clear the view controller stack when SelectViewController appears as follows.
override func viewWillAppear(_ animated:Bool) {
super.viewWillAppear(animated)
var navigationArray = self.navigationController?.viewControllers
navigationArray?.removeAll()
}

Answer 1

Actually, It is not about storyboards. As per the Apple's documentation, "deinit" method gets automatically called when an object is deallocated from memory, not when a view controller is pushed from current one.
When you push "SelectViewController" from "HomeViewController", instance of "HomeViewController" does not deallocated from memory, hence deinit method does not called.
Here is a link to Apple's Documentation for Deinitialization. Alternatively, you can use "viewDidDisappear" method of the view controller to perform an operation if it satisfies your need.

Answer 2

From your code snippet, I understand that you expect deinit is called after pushViewController. But, by calling pushViewController, your navigation controller pushes your HomeViewContoller to navigation stack, which means navigation controller holds strong reference to your HomeViewController object. So, deinit is not called. If you don't need HomeViewController, you have to manually remove it from navigation stack w/in SelectViewController.
See this how. How to remove a specific view controller from uinavigationcontroller stack?
In SelectViewController,
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let allControllers = NSMutableArray(array: navigationController!.viewControllers)
allControllers.removeObject(at: allControllers.count - 2)
self.navigationController!.setViewControllers(allControllers as [AnyObject] as! [UIViewController], animated: false)
}