Structures and Classes

Definition Syntax

                  struct SomeStructure {

    // structure definition goes here

}

class SomeClass {

    // class definition goes here

}
                

                  struct Resolution {

    var width = 0

    var height = 0

}

class VideoMode {

    var resolution = Resolution()

    var interlaced = false

    var frameRate = 0.0

    var name: String?

}
                

Structure and Class Instances

                  let someResolution = Resolution()

let someVideoMode = VideoMode()
                

Accessing Properties

                  print("The width of someResolution is \(someResolution.width)")

// Prints "The width of someResolution is 0"
                

                  print("The width of someVideoMode is \(someVideoMode.resolution.width)")

// Prints "The width of someVideoMode is 0"
                

                  someVideoMode.resolution.width = 1280

print("The width of someVideoMode is now \(someVideoMode.resolution.width)")

// Prints "The width of someVideoMode is now 1280"
                

Memberwise Initializers for Structure Types

                  let vga = Resolution(width: 640, height: 480)
                

Structures and Enumerations Are Value Types

                  let hd = Resolution(width: 1920, height: 1080)

var cinema = hd
                

                  cinema.width = 2048
                

                  print("cinema is now \(cinema.width) pixels wide")

// Prints "cinema is now 2048 pixels wide"
                

                  print("hd is still \(hd.width) pixels wide")

// Prints "hd is still 1920 pixels wide"
                

                  enum CompassPoint {

    case north, south, east, west

    mutating func turnNorth() {

        self = .north

    }

}

var currentDirection = CompassPoint.west

let rememberedDirection = currentDirection

currentDirection.turnNorth()



print("The current direction is \(currentDirection)")

print("The remembered direction is \(rememberedDirection)")

// Prints "The current direction is north"

// Prints "The remembered direction is west"
                

Classes Are Reference Types

                  let tenEighty = VideoMode()

tenEighty.resolution = hd

tenEighty.interlaced = true

tenEighty.name = "1080i"

tenEighty.frameRate = 25.0
                

                  let alsoTenEighty = tenEighty

alsoTenEighty.frameRate = 30.0
                

                  print("The frameRate property of tenEighty is now \(tenEighty.frameRate)")

// Prints "The frameRate property of tenEighty is now 30.0"
                

Identity Operators

                  if tenEighty === alsoTenEighty {

    print("tenEighty and alsoTenEighty refer to the same VideoMode instance.")

}

// Prints "tenEighty and alsoTenEighty refer to the same VideoMode instance."