When are callback methods invoked in the view controller's lifecycle?

The view controller lifecycle callback methods (e.g., UIViewController in iOS) are called by the system at specific points in the controller's lifecycle:

• viewDidLoad — called once after the view is loaded into memory; data is usually initialized here and UI is configured.

• viewWillAppear — called before the view appears on the screen; UI can be updated or data prepared.

• viewDidAppear — called immediately after the view appears; often used to start animations or load data.

• viewWillDisappear — called before the view disappears; state can be saved or operations canceled.

• viewDidDisappear — called after the view has disappeared; resources can be released here.

These methods help manage the UI state and resources depending on the visibility of the controller.