Swift 学习笔记 enum 枚举类型

异端，异端啊，我感觉这是map吧？

 1 enum ATMStatus {
 2     case Success(Int)
 3     case Error(String)
 4 }
 5
 6 var balance = 200
 7
 8 func withdraw(amount: Int) -> ATMStatus {
 9     if balance >= amount {
10         balance -= amount
11         return .Success(balance)
12     } else {
13         return .Error("QiongB")
14     }
15 }
16
17 let result = withdraw(30)
18
19 switch result {
20 case .Success:
21     //print(money)
22     print("I am here")
23     break
24 case let .Error(msg):
25     print(msg)
26     break
27 }

还可以递归包含，但是声明的enum前面要加indirect

 1 indirect enum Expression {
 2     case Number(Int)
 3     case Addition(Expression, Expression)
 4     case Multiply(Expression, Expression)
 5 }
 6
 7 //(5 + 4) * 2
 8 let five = Expression.Number(5)
 9 let four = Expression.Number(4)
10 let sum = Expression.Addition(five, four)
11 let multi = Expression.Multiply(sum, four)
12
13 func compute(expression: Expression) -> Int {
14     switch expression {
15     case let .Number(value):
16         return value
17     case let .Addition(left, right):
18         return compute(left) + compute(right)
19     case let .Multiply(left, right):
20         return compute(left) * compute(right)
21     }
22 }
23
24 compute(multi)

学习进度缓慢，咸鱼