Swift

swift和oc不一样的地方

//类 属性 对象 Foundation (NSArray NSDictionary NSString)

//if bool enum switch for

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 1.如何定义变量和常量

let age = 20

var num = 24

swift中变量有自动类型推断

num = 30是对的

num = 1.5是错误的  由于上面num=24系统已经默认num是整型了

能够在声明的时候肯定变量的类型

var count:Int = 23

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2.字符串 String

定义字符串

let name:String = "wangkaiyu"

var address:String = String()

打印字符串

print(name)

print("My name is \(name)")

截取某段字符串或者获取字符串的唱的

(name as NSString).substringToIndex(4)

(name as NSString).substringWithRange(NSMakeRange(4, 5))

(name as NSString).length

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3.数组Array

//OC数组里面只能存放对象 swift里面能够存听任意类型

//可是一次只能存放同一种类型  定义成什么类型就存放什么类型

var heightArray:Array<Int> = Array()

heightArray.append(3)

heightArray .insert(4, atIndex: 1)添加元素

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 4.if语句

for index in 1...5{

    print(index)

}

 

//用于快速枚举

namesArray.appendContentsOf(["Ellis", "Alisa"])

for name in namesArray{

    print(name)

}

 

//用于字典的遍历

let numberOfLegs:[String:Int] = ["cat":4, "duck":2]

for (name, legs) in numberOfLegs{

    print("name:\(name) leg:\(legs)")

}

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 5.swift支持多种命名格式

let 个人名字:String = "wky"

print(个人名字)

 

let 学生的身高:Array<Int> = [10,20,30]

print(学生的身高[0])

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 6.元祖

let someCharacter: Character = "e"

switch someCharacter {

case "a", "e", "i", "o", "u":

    print("\(someCharacter) is a vowel")

case "b", "c", "d", "f", "g", "h", "j", "k", "l", "m",

     "n", "p", "q", "r", "s", "t", "v", "w", "x", "y", "z":

    print("\(someCharacter) is a consonant")

default:

    print("\(someCharacter) is not a vowel or a consonant")

}

 

 

let somePoint = (1, 1)

switch somePoint {

case (0, 0):

    print("(0, 0) is at the origin")

case (_, 0):

    print("(\(somePoint.0), 0) is on the x-axis")

case (0, _):

    print("(0, \(somePoint.1)) is on the y-axis")

case (-2...2, -2...2):

    print("(\(somePoint.0), \(somePoint.1)) is inside the box")

default:

    print("(\(somePoint.0), \(somePoint.1)) is outside of the box")

}

 

 

let studentInfo = (pName:"wky", pAge:23, pHeight:170)

studentInfo.pName

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7.枚举 

enum CompassPoint {

    case North

    case South

    case West

    case East

}

 

let direction:CompassPoint = .North

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 8.结构体(值传递  会自动添加对应的init方法)

struct MusicModel {

    var name:String?

    var url:String?

    var singer:String?

}

 

let model:MusicModel = MusicModel(name: "哈哈哈", url: "http://www.baidu.com", singer: "哈哈哈")

 

var model2 = model;

model2.name = "呵呵呵"

model.name

结果仍是model的哈哈哈  并无变成呵呵呵

因此使用结构体时  把一个变量赋给另外一个变量  改变另外一个变量的值  原来的变量的值是不会发生改变的

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9.类

类里面声明变量必定要给初值（若是没有初值  就在变量后面加上？表示可选值）

init方法必须本身实现

class Student: NSObject {

    var name:String?

    var _url:String?

    var url:String{

        set{

            self._url = newValue

        }

        get{

            return self._url!

        }

    }

    init(name:String, url:String) {

        super.init()

        self.name = name

        self.url = url

    }

    

    //没有返回值 -> Void省略

    func test(a:Int, b:String){

    }

    

    func test2(a:Int, b:String) -> String{

        return ""

    }

}

 

let xw = Student(name: "快乐崇拜", url: "http://www.baidu.com")

var zs = xw;

zs.name = "七里香"

xw.name

结果就变成七里香了

因此类 和 结构体不一样的就是把一个变量赋值给另外一个变量  当另外一个变量当中的值改变的时候原来的变量里面的值也会随之改变

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10.extension  能够用来添加新的方法 

extension Student{

    func test3(){

        

    }

}

这就给上面的Student类别添加了第三个方法

extension MusicModel{

    

}