Swift Tour漫笔总结(2)

Type Aliases

typealias AudioSample = UInt16

Booleans

非boolean值不会被替代为bool，例如：

let i = 1
if i {
　　// this example will not compile, and will report an error
}

Tuples

例如：HTTPStatus Code ("404", "Not Found")

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

Access Tuple:

let (statusCode, statusMessage) = heep404Error
println("This status code is \(statusCode)")
// prints "The status code is 404"
println("The statuis message is \(statusMessage)")
// prints "The status message is Not Found"

简写，使用 _ 代替不需要的变量，例如：

let (justTheStatusCode, _) = http404Error
println("The status code is \(justTheStatusCode)")
// prints "The status code is 404"

另一种access tuple的方法：

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

Tuple的完整define

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

对应的access

println("The status code is \(http200status.statusCode)")
println("The status code message is \(http200status.description)")