The Complete Guide to Swift

// This is how you define an enum
enum CardShape: Int
{
   // We defined the raw value for the enum as Int, so specifying the first is enough
   case Hearts = 1
   case Clubs, Spades, Diamonds 

   // Enums can have methods associated with them
   func description() -> String
   {
      switch self
      {
         case .Hearts:
            return "Hearts"

         case .Clubs:
            return "Clubs"

         case .Spades:
            return "Spades"

         case .Diamonds:
            return "Diamonds"

         default:
            return "Undefined"
      }
   } 

   func isRed() -> Bool
   {
      case .Hearts, .Diamonds:
         return true

      default:
         return false
   }
}

// Getting the raw value for an enum value (in this case, 3)
// Raw value types can also be strings or floating point values
var heartShapeRawValue = CardShape.Spades.toRaw()

var heartShape = CardShape.fromRaw(heartShapeRawValue)
println("One of the card shapes is \(heartShape.description())")

One more important thing you should know about Enumerations in Swift:

• If there isn't a meaningful raw value for the enum you're creating, you don't have to specify one. Example: Just use enum CardShape {...} instead of enum CardShape: Int {...}.

The basic app structure in Swift is very similar to the one you may know from Objective-C. When you create a new project using the "Single View Application" template we mentioned earlier, you'll see two main files:

• AppDelegate.swift
• ViewController.swift

Those of you who are familiar with iOS development, can see the resemblance to the equivalent files on Objective-C projects. Let's quickly go over the important methods in these files:

In AppDelegate.swift, you can find:

func application(application: UIApplication, 
		    didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool

Which is the first point of customisation after the application is launched.

You can also find the methods that are called when the app is sent to/from the background, resigns/becomes active (when a phone call is received, for example) and when the application is eventually terminated (removed from the background by the user or by the operating system. This is what these methods look like in Swift:

func applicationWillResignActive(application: UIApplication)

func applicationDidEnterBackground(application: UIApplication)

func applicationWillEnterForeground(application: UIApplication)

func applicationDidBecomeActive(application: UIApplication)

func applicationWillTerminate(application: UIApplication)

In ViewController.swift, you can find:

override func viewDidLoad()

override func didReceiveMemoryWarning()

The viewDidLoad method is called (as its name suggests) when the view finishes loading. This is where you'll put necessary logic for the view's proper display.

The didReceiveMemoryWarning method is a chance for you as the developer to clean things up if the operating system decides to warn you that your app is taking up too much space and may be terminated soon unless you take some action.

If you have an existing Objective-C iOS project and don't want to completely migrate it to Swift, but still want to use some of Swift's advantages (and learn to master the language as you code), you can mix and match. You can have both Swift and Objective-C files coexist in the same project, no matter what was the project's original language. All you need to do is create a new .swift file and add it to your existing Objective-C project.