Swift 语言基础（一）

1.变量申明

var greeting:String = "Hello"

如果编译能够推断出变量的类型也可以去掉类型标注

var greeting = "Hello"

很明显”Hello”是一个String类型

Swift会在编译时检查类型是否匹配

2.字符连接

var greeting = "Hello"greeting = greeting +" World!"

Swift 的String类型是可变的

3.如果你想声明一个不可变的值

let greeting = "Hello!"

不可以对常量进行重新赋值

4.语句的结尾不需要分号
除非一行中多个语句

5.所有的数字类型转换必须显示的标明

var radius = 4var pi = 3.14159var area = Double(radius) * Double(radius) *pi

6.编译时检测是否越界

var overflow = Int.max + 1

编译会显示越界
7.Booleans
Boolean 值只能使用Bool 类型。

8.Tuples

var  address:(Int,String) = (51800,"ShenZhen")address.0 //访问邮编address.1 //访问城市

解构Tuple

var address = (51800,"ShenZhen")let (post,city) = addressprintln(post)println(city)

同时也可以通过key来解构Tuple

var address = (post:51800,city:"ShenZhen")println(address.post)println(address.city)

9.字符串插值 (String Interpolation)

var address = (post:51800,city:"ShenZhen")let (post,city) = addressprintln("post:" + String(post) + " city:" + city)println("post: \(post+10),city:\(city)")

10.for循环

let greeting = "I love Swift"for i in 1...5{    println("\(i) ---- \(greeting)")}

11.if语句
条件的结果必须是Bool

if语句必须要放在{}里面

12.Switch语句

var direction = "up"switch direction {    case "down":        println("Going Down!")    case "up":        println("Going up!")    default:        println("Going Nowhere!")}

switch 里面的case必要能够完全匹配可能的值，否则必须加上default.

也可以使用一个范围的值进行匹配

var score = 570switch score{case 1..<10:    println("novice")case 10..<100:    println("proficient")case 100..<1000:    println("rock-star")default:    println("awesome")}