What is the difference between viewDidLoad and viewWillAppear?

viewDidLoad and viewWillAppear are both methods provided by UIViewController in iOS that are called during the lifecycle of a view controller. While they may seem similar, there are key differences in when they are called and what actions they are typically used for:

• viewDidLoad:

• • • viewDidLoad is called when the view controller’s view hierarchy is loaded into memory, typically after the view controller is instantiated from a storyboard or created programmatically.
    • This method is called once during the view controller’s lifecycle, usually before the view is displayed on the screen.
    • viewDidLoad is commonly used for one-time setup tasks, such as initializing properties, setting up UI elements, or loading data that is not dependent on the view’s appearance or layout.
    • It is important to note that viewDidLoad may be called before the view frame is finalized or before Auto Layout constraints are applied, so operations involving view geometry or layout may not yield accurate results.

• viewWillAppear:

• • viewWillAppear is called just before the view controller’s view is added to the view hierarchy and becomes visible on the screen.
  • This method is called every time the view controller’s view is about to be displayed, regardless of whether the view is being presented for the first time or being shown again after being hidden.
  • viewWillAppear is commonly used for tasks that need to be performed every time the view is shown or updated, such as refreshing data, updating UI elements, or responding to changes in the view controller’s state.
  • Since viewWillAppear is called just before the view appears on the screen, it is an appropriate place to perform operations related to the view’s appearance, layout, or interaction with the user.

The main differences between viewDidLoad and viewWillAppear are:

• viewDidLoad is called once after the view controller’s view is loaded into memory, whereas viewWillAppear is called every time the view is about to be displayed.
• viewDidLoad is typically used for one-time setup tasks, while viewWillAppear is used for tasks that need to be performed before the view appears on the screen.