swift学习-元组

元组

元组(tuples)把多个值组合成一个复合值。元组内的值可以使任意类型,并不要求是相同类型。

let http404Error = (404, "Not Found")
// http404Error 的类型是 (Int, String),值是 (404, "Not Found")

你可以将一个元组的内容分解(decompose)成单独的常量和变量,然后你就可以正常使
用它们了:

let (statusCode, statusMessage) =  (404, "Not Found")
 println("The status code is \(statusCode)")
// 输出 "The status code is 404"
 println("The status message is \(statusMessage)")5.
 // 输出 "The status message is Not Found"

如果你只需要一部分元组值,分解的时候可以把要忽略的部分用下划线(_)标记:

 let (justTheStatusCode, _) = (404, "Not Found")
 println("The status code is \(justTheStatusCode)")
3. // 输出 "The status code is 404"

此外,你还可以通过下标来访问元组中的单个元素,下标从零开始:

let http404Error = (404, "Not Found")

 println("The status code is \(http404Error.0)")
 // 输出 "The status code is 404"
 println("The status message is \(http404Error.1)")
 // 输出 "The status message is Not Found"

你可以在定义元组的时候给单个元素命名:

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

给元组中的元素命名后,你可以通过名字来获取这些元素的值:

 println("The status code is \(http200Status.statusCode)")
 // 输出 "The status code is 200"
 println("The status message is \(http200Status.description)")
 // 输出 "The status message is OK"