Swift语言简述

从6月3号凌晨发布会结束，网上很多翻译自苹果iBook的swift指南就出现在网上了，学到不少，不过实践出真知，除了基本的语法之外，下载了最新版的xcode6Beta，用来测试。以下是学习笔记：

    Swift语法

println("Hello, world”)

变量

var myVariable = 42

myVariable = 50

let myConstant = 42”

let implicitInteger = 70

let implicitDouble = 70.0

let explicitDouble: Double = 70

let label = "The width is "

let width = 94

let widthLabel = label + String(width)

\() 可以理解为%@:

let apples = 3

let oranges = 5

let appleSummary = "I have \(apples) apples."

let fruitSummary = "I have \(apples + oranges) pieces of fruit.

创建数组和字典使用方括号（[]），并通过在括号内写索引或键访问自己的元素:

数组的赋值：

var shoppingList = ["catfish", "water", "tulips", "blue paint"]

shoppingList[1] = "bottle of water"

 

字典的赋值：(key:value结构)

var occupations = [

    "Malcolm": "Captain",

    "Kaylee": "Mechanic",

]

字典中某个键的赋值:

occupations["Jayne"] = "Public Relations”

创建一个空的数组：

let emptyArray = String[]()

创建空字典：

let emptyDictionary = Dictionary<String, Float>()

如果类型信息可推断，则可以设置空的数组：shoppingList = []

空字典： shoppingDic=[:]

使用if、switch作为条件判断，使用for-in、for、while、do-while构造循环。

let individualScores = [75, 43, 103, 87, 12]

var teamScore = 0

for score in individualScores {

    if score > 50 {

        teamScore += 3

    } else {

        teamScore += 1

    }

}

let vegetable = "red pepper"

switch vegetable {

case "celery":

    let vegetableComment = "Add some raisins and make ants on a log."

case "cucumber", "watercress":

    let vegetableComment = "That would make a good tea sandwich."

case let x where x.hasSuffix("pepper"):

    let vegetableComment = "Is it a spicy \(x)?"

default:

    let vegetableComment = "Everything tastes good in soup."

}

switch语句支持多种数据和多种比较，若匹配则立即跳出，所以不需要break。

var n = 2

while n < 100 {

    n = n * 2

    println(n)

}

var m = 2

do {

    m = m * 2

    println(m)

} while m < 100

这两个程序是等价的，结果都是

4  8  16  32  64  128

其中第一个是swift式的。

var firstForLoop = 0

for i in 0..3 {

    firstForLoop += 1

    println("第一组+\(firstForLoop)")

}

var secondForLoop = 0

for var i = 0; i < 3; ++i {

    secondForLoop += 1

    println(secondForLoop)

}

两组程序是等价的，结果：

第一组+1

第一组+2

第一组+3

1

2

3

用..方式设置初始值和最终值。

函数

func greet(name: String, day: String) -> String {

    return "Hello \(name), today is \(day)."

}

greet("Bob", "Tuesday")

println(greet("Bob", “Tuesday"))

执行结果：Hello Bob, today is Tuesday.

name: String 形式定义变量及类型  （）内用逗号分隔参数，->后跟函数返回类型

学习的资源来自：http://gashero.iteye.com/blog/2075324 以及苹果iBooks。