Swift中的Tuple类型

Swift中的Tuple类型可以包含任何值，并且这些值的类型可以互相不一样。Tuple本身比较简单，需要记得也就是访问Tuple的方式。

使用变量名访问

    let http404Error = (404, "Not Found")
    // http404Error is of type (Int, String), and equals (404, "Not Found")

    let (statusCode, statusMessage) = http404Error //注意这里
    print("The status code is (statusCode)")
    // Prints "The status code is 404"
    print("The status message is (statusMessage)")
    // Prints "The status message is Not Found"

使用这种方式，还可以使用_忽略后面的Tuple值：

    let (justTheStatusCode, _) = http404Error
    print("The status code is (justTheStatusCode)")
    // Prints "The status code is 404"

使用序号访问

    print("The status code is (http404Error.0)")
    // Prints "The status code is 404"
    print("The status message is (http404Error.1)")
    // Prints "The status message is Not Found"

使用key访问

Tuple定义的时候，可以给每个value前添加一个key，访问的时候可以使用这个key访问：

    let http200Status = (statusCode: 200, description: "OK")

    print("The status code is (http200Status.statusCode)")
    // Prints "The status code is 200"
    print("The status message is (http200Status.description)")
    // Prints "The status message is OK"