异端，异端啊，我感觉这是map吧？
enum ATMStatus {
case Success(Int)
case Error(String)
}
func withdraw(amount: Int) -> ATMStatus {
if balance >= amount {
balance -= amount
return .Success(balance)
} else {
return .Error("QiongB")
}
}
let result = withdraw()
switch result {
case .Success:
//print(money)
print("I am here")
break
case let .Error(msg):
print(msg)
break
}
还可以递归包含，但是声明的enum前面要加indirect
indirect enum Expression {
case Number(Int)
case Addition(Expression, Expression)
case Multiply(Expression, Expression)
}
//(5 + 4) * 2
let five = Expression.Number()
let four = Expression.Number()
let sum = Expression.Addition(five, four)
let multi = Expression.Multiply(sum, four)
func compute(expression: Expression) -> Int {
switch expression {
case let .Number(value):
return value
case let .Addition(left, right):
return compute(left) + compute(right)
case let .Multiply(left, right):
return compute(left) * compute(right)
}
}
compute(multi)
学习进度缓慢，咸鱼