Swift学习-概述

失去的东西，

也许从未真正拥有过，

所以不必惋惜。

开始学习Swift，Swift一年内必将取代Objective-C。

不忘初心，方得始终。

没时间只是借口。

首先第一句代码：hello world

println("Hello,world!")

关键字：let    表示常量

let constant = 42

ps：swift是先将程序转化为Objective-C，再将Objective-C转化为C语言。

Swift格式要求貌似非常高，一个空格都是错误。

=两边都要有空格。

关键字：var   表示变量

var variable = 1

variable = 2

设置数据类型：

let integerNum = 1

let doubleNumA = 1.1

let doubleNum​B: ​Double​ = ​1.2

强制转换：

let label = "hello, number is"

let num = 43

let newLabel = label + String(num)

在字符串中包含参数： \()

let apple = 3

let appleNum = " I have \(apple) apples. "

数组：[ ]

var balls = ["football" , "basketball" , "volleyball"]

空数组：let emptyArray = [String]()

balls = [ ]

字典：[:]

var people = ["Tony":"football" ,"Jesse":"basketball" , "Any":"volleyball"]

空字典：let emptyDic = [String:String]()

balls = [:]

for-in:

var nums = [3 , 2 , 5 , 4]

var sum = 0

for num in nums{

    sum += num

}

sum

关键字：if

var optionalName:String? = "Jesse"  //初始化，当optionalName缺省就为“Jesse”

if let name = optionalName{

      //if中只能是bool型，当optionalName为空为false，否则为true

}

关键字:switch

ps:没有break,默认自带break

     必须带default

let ball = "volleyball"

switch ball{

case "basketball":

      let ballComment = "basketball"     //break;

case "football":

     let ballComment = "football"

case "volleyball":

     let ballComment = "volleyball"

default:

    let ballComment = "ok"

}

关键字:for-in

let numbers = [1,2, 3, 4, 5, 6,7]

for  a in numbers {

}

var sum0 = 0

for i in 0..<4{

    sum0 += i

}

关键字:while

var n = 0

var sum = 0

while n < 10 {

     sum += n++

}

var m = 0

var sum2 = 0

do {

 sum2 += m++

}while m <10

关键字:  ..<

0..<4 == 0 ,1, 2, 3

关键字：func   函数

func function(name: String, age: Int) -> String{

  return"name is \(name),age is \(age)"

}

返回多参数

func calculate(scores:[Int]) -> (max :Int, min:Int){

   var max = scores[0]

   var min = scores[0]

    for score in scores{

        if score > max{

              max = score

        }else if score < min{

              min = score

        }

    }

    return (max, min)

}

输入不定参数

func sumOf(numbers: Int...) -> Int{

 var sum = 0

    for number in numbers{

       sum += number

    }

 return sum

}

函数里面包含函数

func functinInFunction(input: Int) -> Int{

     var y = input

    func add(){

      y += 5

    }

    add()

    return y

}

返回函数

func returnFunction() -> (Int -> Int){

    func add(input: Int) -> Int{

         return input + 1

    }

    return add

}

var lalala = returnFunction()

lalala(5)

函数作为参数

func hasAnyMatch(numbers: [Int], condition: Int -> Bool) -> Bool{

    for number in numbers{

        if condition(number){

            return true

        }

    }

    return false

}

func lessThanTen(input: Int) -> Bool{

    return input < 10

}