swift - 如何访问案例的切换结果？

Question

如何访问示例 apple swift book 代码的 switch 语句结果？

我想我可以创建只返回 case 语句值的函数，但我试图理解这段代码。

enum ServerResponse {
    case Result(String, String)
    case Error(String)
}

let success = ServerResponse.Result("6:00 am", "8:09 pm")
let failure = ServerResponse.Error("Out of cheese.")

switch success {
case let .Result(sunrise, sunset):
    let serverResponse = "Sunrise is at \(sunrise) and sunset is at \(sunset)."
case let .Error(error):
    let serverResponse = "Failure...  \(error)"
}

Answer 1

这个例子太做作了，一点用处都没有。考虑一下

enum ServerResponse {
    case Result(String, String)
    case Error(String)
}

for i in 1...100 {
    let mySuccess: ServerResponse = {
        let zeroOrOne = rand() % 2
        if zeroOrOne == 0 {
            return ServerResponse.Result("7:00 am", "8.09 pm")
        } else {
            return ServerResponse.Error("Out of cheese.")
        }
    }()

    var serverResponse: String
    switch mySuccess {
    case let .Result(sunrise, sunset):
        serverResponse = "Sunrise is at \(sunrise) and sunset as \(sunset)"
    case let .Error(error):
        serverResponse = "Failure... \(error)"
    }

    println(serverResponse)
}

要点是示例中的“成功”变量实际上应该是某个函数/子系统调用的结果赋值。为了 println() 的清晰度，我将它包裹在一个循环中