Dictionary

• 선언

var operations: Dictionary<String, Double> = [
	"π" : Double.pi,
    "e" : M_E
]

• 호출

func performOperation(symbol: String){
	if let constant = operations[symbol]{
    	accumulator = constant
    }
}

• 약식

var pac10teamRankings = Dictionary<String, Int>()
// is
var pac10teamRankings = [String:Int]()

• 딕셔너리에서 key를 통해 value를 얻을땐 옵셔널 타입

pac10teamRankings = ["stanford":1, "Cal":10]
let ranking = pac10teamRankings["Ohio State"]// ranking의 타입은 Int? (nil)

• 열거 방법(튜플이용)

for(key, value) in pac10teamRankings {
	print("\(key) = \(value)")
}