So you are in Atlanta on Tuesday, open up your application to look for an ATM, then check your balance. In fact, this situation, to me, is the biggest fallacy in writing code: the easiest way is the easiest way. Applications will change. User interfaces will change. Taking the easy way out initially leads to all kinds of subtle bugs and hardships in the future. Today, the best-selling product in history turns 10 years old. On June 29, , the original iPhone went on sale….
Scroll views are a great way to get more content on a screen than can actually fit, especially for smaller devices. Let's talk about how to keep a clean style code in Swift. You override this method only in case you want to build the whole interface for the view controller from code.
If you are working with storyboards or nib files you do not have to do anything with this method and you can ignore it. Its implementation in UIVIewController loads the interface from the interface file and connects all the outlets and actions for you. Application : It is common to use this method to populate the user interface of the view controller with data before the user sees it.
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. A common case are network calls that you need to do only once when the screen is loaded. Good place to init and setup objects used in the viewController. Important thing to remember : 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 perform some task every time a view controller comes on screen, then you need the following methods. Keep in mind that in this lifecycle step the view bounds are not final. This method can be called multiple times for the same instance of a view controller. Notifies the view controller that its view is about to be added to a view hierarchy Application : 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.
If you need a method thats called every time the view appears on screen, you should use viewWillAppear. While viewDidLoad is only called once, viewWillAppear is called every time the view will appear on the screen.
For example, the Now Playing section in a music app or any view that is updated when it is scrolled to. You could also use this to update the status bar when a certain view is appearing or navigated back to. It happens before any animations are started. Go ahead and try it! Try it out. You won't see the random color "pop" in anymore. Mission accomplished, right? In this simple app, that only occurs once, but in a more complicated app with multiple screens, it would mean the user would see a new color every time they navigated back to this screen.
That may be what you want, but you can also consider putting the code that sets the background color in viewDidLoad. This will change the background color once, when the view is loaded. Try putting the code there. Your complete implementation of ViewController will look like this:. One thing to note before ending the lesson: The line of code that changed the background color referenced a variable called view.
You'll learn more about this in later lessons, but it's important to note that the variable view is not random or magical; it's just an instance variable. View View LifeCycle on Learn. Swift Viewlifecycle Readme Keep away from people who try to belittle your ambitions. Learning Objectives Connect the View Controller to a. But before we get started writing code, let's talk about how your application creates views.
That was a lot to digest at once, so let's take it piece by piece. How does that view get associated with a view controller?
Bring up the view controller's Identity Inspector. Right now, ViewController. You should see output like this: Putting It Together Now that you have an understanding of the view life cycle, let's demonstrate it in a more practical manner: By changing the color of the view's background color. You can change the background color to a random color with a simple line of code: view.
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