![]() Code you need to execute only once should go into an initializer or viewDidLoad().You can also prepare the interface for animations you want to trigger when the view controller appears.Usually you use this method to update the user interface with data that might have changed while the view controller was not on the screen.Notifies the view controller that its view is about to be added to a view hierarchy.This method can be called multiple times for the same instance of a view controller. You override this method for tasks that you need to repeat every time a view controller comes on screen.Keep in mind that in this lifecycle step the view bounds are not final.If you need to perform some task every time a view controller comes on screen, then you need the following methods. This method is called only once in the lifetime of a view controller, so you use it for things that need to happen only once.If you need to repeat them (background activity/ UI changes/ make network calls ) to update the data in the view controller ,viewDidAppear(_:) is more appropriate to do so.Good place to init and setup objects used in the viewController.A common case are network calls that you need to do only once when the screen is loaded.It is also a good place where to start some background activity where you need to have the user interface in place at the end.It is common to use this method to populate the user interface of the view controller with data before the user sees it.When this method gets called, the view of the view controller has been created and you are sure that all the outlets are in place.Its implementation in UIVIewController loads the interface from the interface file and connects all the outlets and actions for you. If you are working with storyboards or nib files you do not have to do anything with this method and you can ignore it.Don’t use this unless there is a valid reason. You override this method only in case you want to build the whole interface for the view controller from code. This is the method that creates the view for the view controller.If you create a view controller from a nib file, this initializer is called instead of init(coder:).You do not need to move every view controller in a separate nib file. You also might have a project that was created when storyboards did not exist yet, so every view controller had its own nib file.Keep in mind that if your main storyboard starts getting too big, you can split it into more storyboards. This might happen, for example, to work in a larger team where different members need to be change view controller interfaces without affecting the work of others. ![]() Sometimes you might decide to put your view controller’s interface in a separate nib file instead of a storyboard.This might create unexpected behavior and bugs, so it’s safer not to access the view until later in the lifecycle. If you try to access it through the view property of UIViewController, the loadView() method will be called. Beware that the view of the view controller has still not been instantiated at this point.Previous view controllers might also pass these objects to the current one, so you do not always need to instantiate them in every view controller.These include model objects or other auxiliary controllers, like network controllers. During the initalization phase of a view controller, you usually allocate the resources that the view controller will need during its lifetime.If you are curious, serialization transforms an object in a byte stream that you can save on disk or send over the network. This is not used often, so you can ignore the parameter. It provides an NSCoder instance as a parameter, which you need only if you are using iOS serialization APIs.View controller are usually created from storyboards.When this is the case,init(coder:) is the initializer that gets called and you have to override.
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