Methods

Methods

Structures and enumerations are value types. By default, the properties of a value type cannot be modified from within its instance methods.

struct Point {
    var x = 0.0, y = 0.0
    mutating func moveByX(deltaX: Double, y deltaY: Double) {
        x += deltaX
        y += deltaY
    }
}
var somePoint = Point(x: 1.0, y: 1.0)
somePoint.moveByX(2.0, y: 3.0)
println("The point is now at ((somePoint.x), (somePoint.y))")
// prints "The point is now at (3.0, 4.0)" 

let fixedPoint = Point(x: 3.0, y: 3.0)
fixedPoint.moveByX(2.0, y: 3.0)
// this will report an error 

enum TriStateSwitch {
    case Off, Low, High
    mutating func next() {
        switch self {
        case Off:
            self = Low
        case Low:
            self = High
        case High:
            self = Off
        }
    }
}
var ovenLight = TriStateSwitch.Low
ovenLight.next()
// ovenLight is now equal to .High
ovenLight.next()
// ovenLight is now equal to .Off 

struct LevelTracker {
    static var highestUnlockedLevel = 1
    static func unlockLevel(level: Int) {
        if level > highestUnlockedLevel { highestUnlockedLevel = level }
    }
    static func levelIsUnlocked(level: Int) -> Bool {
        return level <= highestUnlockedLevel
    }
    var currentLevel = 1
    mutating func advanceToLevel(level: Int) -> Bool {
        if LevelTracker.levelIsUnlocked(level) {
            currentLevel = level
            return true
        } else {
            return false
        }
    }
}

class Player {
    var tracker = LevelTracker()
    let playerName: String
    func completedLevel(level: Int) {
        LevelTracker.unlockLevel(level + 1)
        tracker.advanceToLevel(level + 1)
    }
    init(name: String) {
        playerName = name
    }
}

var player = Player(name: "Argyrios")
player.completedLevel(1)
println("highest unlocked level is now (LevelTracker.highestUnlockedLevel)")
// prints "highest unlocked level is now 2”

player = Player(name: "Beto")
if player.tracker.advanceToLevel(6) {
    println("player is now on level 6")
} else {
    println("level 6 has not yet been unlocked")
}
// prints "level 6 has not yet been unlocked"