Tell me about the lifecycle of UIViewController.

UIViewController goes through the following main stages:

1. Initialization: Creating an instance of the controller.
2. Loading View: Loading or creating the view associated with the controller (UIView).
3. View Appearing: Preparing and displaying the view on the screen.
4. View Displayed: The view is fully visible and interacts with the user.
5. View Disappearing: The view starts to hide or is removed from the screen.
6. View Unloading: The view is removed from memory.

Main lifecycle methods:

• init(nibName:bundle:) / required init?(coder:): Initialization of the controller.
• viewDidLoad(): Called once after the view is loaded into memory.
• viewWillAppear(_:): Called just before the view appears on the screen.
• viewDidAppear(_:): Called after the view has fully appeared on the screen.
• viewWillDisappear(_:): Called just before the view is hidden or removed.
• viewDidDisappear(_:): Called after the view has been fully hidden or removed.
• viewWillLayoutSubviews(): Called before the view controller's subviews start to change their size and position.
• viewDidLayoutSubviews(): Called after the subviews have finished changing their size and position.
• didReceiveMemoryWarning(): Called when a low memory warning is received.
• deinit: Called before the memory occupied by the controller instance is released.

Usage example:

class MyViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Perform one-time view setup here
        print("viewDidLoad")
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        // Update UI before the view appears
        print("viewWillAppear")
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        // Start animations or other tasks after the view appears
        print("viewDidAppear")
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        // Save UI state before the view disappears
        print("viewWillDisappear")
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        // Stop tasks that are not needed when the view is not visible
        print("viewDidDisappear")
    }

    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        // Configure frames of elements before they are redrawn
        print("viewWillLayoutSubviews")
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        // Configure after elements are redrawn
        print("viewDidLayoutSubviews")
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Release resources in low memory situations
        print("didReceiveMemoryWarning")
    }

    deinit {
        // Cleanup subscriptions and other resources
        print("deinit")
    }
}