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Data Structures & Methods

Data Structures

class, enum and struct are the basic building blocks of swift they have:

  • Similar Syntax
  • Can have Properties (var, let), Methods (func)
  • Can have initializer
  • Only class has inheritance
  • Only class has introspection and casting
  • class = Reference type, enum and struct = Value type

enums

enum enumTypeVar : Int { // explicitly all Int's
    case firstProperty   = 1
    case secondProperty  = 2
}
vat type = enumTypeVar.firstProperty

enum Barcode {
    case UPCA(Int, Int, Int, Int)
    case QRCode(String)
}

struct

struct Resolution {
    var width = 0
    var height = 0
}

class

Creation

class MyClass : OptionalSuperClass, OptionalProtocol1, OptionalProtocol2 {
  var myProperty : String var myOptionalProperty : String?
  // More Properties  ::
  // Only need override dif subclassing
  override init() {
    myProperty = "initValue"
  }
  // More methods
  }

Usage

var myClassObject = MyClass()
  println("(myClassObject.myProperty)") // "initValue"
  println("(myClassObject.myOptionalProperty!)") // nil

Final

With Final a funcor class can't be override. It will be the end of the line.

Methods func

func doIt() -> Int {
    return 0
}

Internal & External Names

Methods in swift can have internal and external names. The first parameter is a littel different, it should be consistent with the method name.

  • First parameter has no external name but can be forced with #.
  • All other parameters need to have an external name
  • _ == "I don't care". An name can be eliminated
func doIt(a:Int) -> Int {
    return a
}
doIt(0)         // return 0

func doIt(a:Int, b:Int) -> (a:Int, b:Int){
    return (a, b)
}
doIt(0, b:1)   // returns a tuple (a,b) == (0,1)
doIt(a:0, b:1) // error first param has no external name

func doIt(externalName InternalName:Int) -> Int {
    return internalName
}
doIt(externalName:0)
doIt(0)              // Error no external name given

func doIt(#InternalandImplicitExternalName:Int) -> Int {
    return InternalandImplicitExternalName
}
doIt(InternalandImplicitExternalName:0)

override

A Method from a superclass can be override wiwth the keyword override

class Classname : SuperClassName {
    override doIt()
}

final()

With Final a funcor class can't be override. It will be the end of the line.

init() Method

Two types of init

  • designated init()
  • convenience init()

Free Inits

  • If all Properties are initialized
  • structwith no initializers will get a default init

What can be done in an init:

  • Set or Reset properties values var and even let
  • Call other init methods self.init()
  • Call super classes init methods super.init()

What have to be done in an init:

  • After init() all properties need to have an value (or nil)
  • Designated init can only call designated init of its immediate superclass
  • All own properties need to be initialized before using superclass init
  • The superclass init nedd to be called before inherited properties can ba assigned
  • convenience init can only call designated init in it's own class
  • convenience init can call other convenience init but in the end a designated init must be called
  • convenience init first call designated init before set any property value

Inherited init

  • If no init is implemented all superclass init are inherited
  • If you override all superclass init, you'll inherit all its convenience init
  • If you implement no init, you'll inherit all superclass init

Required init

  • A class can mark one or more init as required

Failable init

Rare, it is a init which can return nil

init?(){
    // might return nil
}

## UIImage example
let image = UIImage(named: "nonExistingName") // image is an Optional UIImage?
// solution
if let image= UIImage(named: "nonExistingName"){
    // image was successfully created
} else {
    // couldn't create the image
}

Objects

Creating Objects

Calling init via the type name

let x = ClassName()
let y = [String]()

Calling type methods (rare)

let button = UIButton.buttonWithType(UIButtonType.System)

AnyObject

  • sSpecial Type (it is a Protocol) used to compatibility with Objective-C-based API
// As Properties
var destinationViewController : AnyObject
var toolbarItems: [AnyObject]

// As Arguments to functions
func appendDigit(sender: AnyObject)
func addConstraints(constraints: [AnyObject])

// Return type of functions
class func buttonWithType(buttonType: UIButtonType) -> AnyObject

Convert AnyObject

Casting as or as?

var destinationViewController: AnyObject
let calcVC = destinationViewController as CalculatorViewVController  // could crash if not correct

if let calcVC = destinationViewController as? CalculatorViewController { ... }

Cast on the fly

let button: AnyObject = UIButton.buttonWithTyoe(UIButtonType.System)
let title = (button as UIButton).currentTitle