Swift培训

　　本篇是Swift内部培训整理的PPT材料，主要内容来源于苹果Swift编程语言官方教程，参考了网上的一些视频课程内容。在教程介绍完之后，本人附带实现了一个项目开发中的常用场景的Demo：基于导航栏和Tab栏的应用。

1.Swift概述

　　我们先来看一篇文章：《苹果新贵 Swift之前世今生》

　　Swift是用于设计iOS及Mac OS X应用的一门新语言。

1.1.Swift特点

1. Swift保留了C与Objective-C的优点，并摒弃其为了兼容C语言所受的限制；
2. Swift吸纳了安全编程模式，并新增了一些现代化功能，使其更易使用、更为灵活、更具乐趣。
3. Swift的简洁风格与广受欢迎的成熟框架Cocoa/Cocoa Touch相结合，将为重新构思软件的开发过程带来新机遇；
4. Swift内存管理采用ARC风格。

1.2.Swift代码的文件扩展名

　　*.swift

2.第一个Swift程序

2.1.使用Xcode Project编写

2.2.使用Playground编写

　　我们可以基于 Playground 做这些事情：

1. 学习：通过 Playground 学习 Swift，制作 Swift 教程实现交互式学习，同时还可以培训其他初学者。
2. 代码开发：执行算法程序，迅速看到算法结果，跟踪变量；执行绘图程序，即时看到图像结果，及时调整。执行通用代码，查看变量的改变情况。
3. 实验性代码：无需创建项目，直接打开一个独立的Playground文件即可编写代码，尝试调用新的 API。

3.常量与变量

　　let关键词声明常量，var关键词声明变量。

let maximumNumberOfLoginAttempts =   // 常量只有在初始化的时候可以赋值

var currentLoginAttempt = 

4.运算符和表达式

4.1.运算符

1. 算术运算符：*、/、+、—、%、++、——
2. 关系运算符：>、<、>=、<=、==、!=
3. 布尔逻辑运算符：！、&&、||
4. 三元运算符：？：

4.2.表达式

　　1.不指定数据类型

var a1 = 

var a2 = 

var a = a1 > a2 ? "a1":"a2"

　　2.指定数据类型

var a1:Int = 

var a2:Int = 

var a = a1 > a2 ? "a1":"a2"

　　3.可以有分号结尾

var a1:Int = ; var a2:Int = 

var a = a1 > a2 ? "a1":"a2"

4.3.注释

//

/*    */

5.数据类型

5.1.整型

　　Swift提供8、16、32、64位形式的有符号及无符号整数，这些整数类型遵循C语言的命名规约。与Swift中的所有类型一样，这些整数类型的名称以大写字母开头。

　　Swift还提供了一个整数类型Int；

1. 在32位平台，Int与Int32宽度一致；
2. 在64位平台，Int与Int64宽度一致；

　　Swift还提供了无符号整数类型UInt。

5.2.浮点型

1. 单精度浮点(32位) Float
2. 双精度浮点(64位) Double

5.3.数字型

　　表示数字如下：

let decimalInteger =   // 表示是10进制

let binaryInteger = 0b10001  // 二进制17

let octalInteger = 0o21  // 8进制17

let hexadecimalInteger = 0x11  // 16进制17

5.4.布尔类型

　　true和false

let orangesAreOrange = true

let turnipsAreDelicious = false

6.数据类型转换

6.1.整型转换

　　不同类型的整数常量或变量所能存储的值域不同，需要显示地转换

let twoThousand:UInt16 = 

let one:UInt8 = 

//let twoThousandAndOne = twoThousand + one  // 错误

let twoThousandAndOne = twoThousand + UInt16(one)  // 正确

6.2.整型与浮点数转换

　　整数与浮点数类型之间的转换，需要显示地转换：

let three = 

let pointOneFourOneFiveNine = 0.14159

let pi = Double(three) + pointOneFourOneFiveNine

7.字符串类型

7.1.字符串初始化

　　1.初始化

let someString = "Some string literal value"

let wiseWords = "\"Imagination is more important than knowledge\" - Einstein"

let dollarSign = "\x24"  // $,Unicode scalar U+0024

　　2.空值

var emptyString = ""  // 空串初始化

var anotherEmptyString = String()  // 通过初始化函数初始化

　　3.空值判断

if emptyString.isEmpty{

    println("Nothing to see here")

}

if emptyString == ""{

    println("Nothing to see here")

}

7.2.字符串修改

　　var 声明的可以修改，let不能修改。

var variableString = "Horse"

variableString += " and carriage"

7.3.字符串插入

　　斜杠+括号+变量

let multiplier = 

let message = "\(multiplier) times 2.5 is \(Double(multiplier) * 2.5)"

7.4.字符串长度

　　使用countElements函数。OC中使用length属性。

let unusualMenagerie = "Koala , Snail, Penguin"

println("unusualMenagerie has \(countElements(unusualMenagerie)) characters")

7.5.比较字符串相等

let quotation = "We're a lot alike,you and I."

let sameQuotation = "We're a lot alike,you and I."

if quotation == sameQuotation{

    println("These two strings are considered equal")

}

8.元组(tuple)类型

　　元组将多个值组合为单个值。元组内的值可以是任意类型，各元素不必是相同的类型，元组在作为函数返回值时尤其有用。

　　1.定义方法1

let http404Error = (,"Not Found")

println("The status code is \(http404Error.0)");

println("The status message is \(http404Error.1)");

　　2.定义方法2

let http200Error = (statusCode:,discription:"Not Found")

println("The status code is \(http200Error.statusCode)");

println("The status message is \(http200Error.discription)");

9.可选(Optional)类型

9.1.使用可选类型

　　我们在如下情况下使用可选类型：

1. 它有值但不确定；
2. 没有任何值。

let possibleNumber = ""

let convertedNumber:Int?=possibleNumber.toInt()

　　“Int?”是可选类型

if convertedNumber{

    println("\(possibleNumber) has an Integer value of \(convertedNumber!)")

}
else{

    println("\(possibleNumber) could not be convented to an integer")

}

　　convertedNumber是从可选类型中取值

9.2.使用nil

　　我们可以为可选类型的变量设置nil值，表示没有任何值。

var serverResponseCode:Int?=

serverResponseCode = nil

　　如果不是可选类型，那么是不能设置为nil的

10.数组

10.1.数组初始化

　　基本语法：

[value1,value2,value3]

var shoppingList:String[] = [“Eggs","Milk"]

　　对比一下OC中的方式：

NSArray *array = @[@"aa",@"bb"];

10.2.数组追加元素

　　使用append函数追加或通过+操作符：

var shoppingList:String[] = ["Eggs","Milk"]

shoppingList.append("Flour")

shoppingList += ["Cheese","Butter"]

10.3.数组插入元素

　　使用insert方法：

var shoppingList:String[] = ["Eggs","Milk"]

shoppingList.insert("Butter", atIndex: )

shoppingList += ["Cheese","Chocolate Spread"]

　　比较一下OC中：

[array insertObject:@"dd" atIndex:];

10.4.数组删除元素

　　使用removeAtIndex方法

var shoppingList:String[] = ["Eggs","Milk","Butter"]

let deleteItem = shoppingList.removeAtIndex()

println(deleteItem)

println(shoppingList)

10.5.数组长度

　　使用count属性(和OC中一样)：

var shoppingList:String[] = ["Eggs","Milk","Butter"]

println("The shopping list contains \(shoppingList.count) items.")

10.6.数组遍历

　　1.遍历方法1

var shoppingList:String[] = ["Eggs","Milk","Butter"]

for item in shoppingList{

    println(item)

}

　　2.遍历方法2

　　有循环变量：

for(index,value) in enumerate(shoppingList){

    println("Item \(index + 1):\(value)")

}

11.字典

11.1.字典初始化

　　基本语法：

[key1:value1,key2:value2,key3:value3]

var airports:Dictionary<String,String> = ["TYO":"Tokyo","DUB":"Dublin"]

11.2.字典追加元素

var airports:Dictionary<String,String> = ["TYO":"Tokyo","DUB":"Dublin"]

airports["LHR"] = "Lonton"

println("The dictionary of airports contains \(airports.count)")

11.3.字典删除元素

　　通过removeValueForKey(key)方法删除

var airports:Dictionary<String,String> = ["TYO":"Tokyo","DUB":"Dublin"]

if let removedValue = airports.removeValueForKey("DUB"){

    println("The removed airport's name is \(removedValue)")

}
else{

    println("The airports dictionary does not contains a value for DUB")

}

11.4.字典长度

　　使用count属性

println("The count of airport's is \(airports.count)")

11.5.字典遍历

　　1.遍历字典

var airports:Dictionary<String,String> = ["TYO":"Tokyo","DUB":"Dublin"]

for (airportCode,airportName) in airports{

    println("\(airportCode):\(airportName)")

}

　　2.遍历键和值

for airportCode in airports.keys{

    println("Airport code:\(airportCode)")

}

for airportName in airports.values{

    println("Airport name\(airportName)")

}

　　3.获得键和值的数组

let airportCodes = Array(airports.keys)

let airportNames = Array(airports.values)

12.控制语句

12.1.分支语句

　　1.条件语句if-else

if boolean-expression{

statement1;

}[else if boolean-expression{

statement2;

}]
[else{

statement3;

}]

　　2.多分支语句switch

switch some value to consider{

case value1,value2,value3:

respond to value1

default:

otherwise

}

　　每个case不需要显示地添加break,每个case至少有一条语句。可以比较任何类型。

12.2.循环语句

　　1.while语句

while condition{

statements

}

　　示例：

var i = 

var r = 

var s = 

var t = 

while i <  {

    r = i /  ;

    s = (i - r * ) / ;

    t = i - r *  - s * ;

    if(i == r * r * r + s * s * s + t * t * t){

        println("i=\(i)");

    }

    i++

}

　　2.do-while语句

do{

statements

}while condition

　　示例：

var i = 

var r = 

var s = 

var t = 

do{

    r = i /  ;

    s = (i - r * ) / ;

    t = i - r *  - s * ;

    if(i == r * r * r + s * s * s + t * t * t){

        println("i=\(i)");

    }

    i++

}while i < 

　　3.for语句

for initialization;condition;increment{

statements

}

　　示例：

var i = 

var r = 

var s = 

for var j = ;j <= i;j++ {

    r = j * j;

    s = j * j * j;

    println("\(j)的平方：\(r) \(j)的立方：\(s)");

}

　　4.for in语句

　　一般用于遍历集合

　　1.遍历范围

for index in ...{

    println("\(index) times 5 is \(index * 5)");

}

　　2.忽略循环变量

let base = 

let power = 

var answer = 

for _ in ...power{

    answer *= base;

}

println("\(base) to the power of \(power) is \(answer)")

　　3.遍历数组

let names = ["Anna","Alex","Jack"]

for name in names{

    println("Hello,\(name)")

}

　　4.遍历字典

let numberofLegs = ["spider":,"ant":,"car":];

for(animalName,legCount) in numberofLegs{

    println("\(animalName) have \(legCount) legs")

}

　　5.遍历字符串

for character in "Hello"{

    println(character)

}

12.3.跳转语句

1. continue：终止当次循环，接着进入下一次循环
2. break：终止循环；
3. fallthrough：其他语言没有的，贯穿的意思，常用于switch语句中，示例如下：

let integerDescribe = 

var description = "The number \(integerDescribe) is"

switch integerDescribe{

case ,,:

    description += " a prise number,and also"

    fallthrough

default:

    description += " an integer.";

}

4.return

13.函数

13.1.函数定义

　　使用func定义一个函数。调用函数使用它的名字加上小括号中的参数列表。使用->分隔参数的名字和返回值类型。

　　函数声明：

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

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

}

　　函数调用：

greet("Bob", "Tuesday")

13.2.无返回值函数

func sayGoodBye(personName:String){

    println("Goodbye,\(personName)");

}

sayGoodBye("Tony");

13.3.多返回值函数

　　使用元组类型返回多个值

func count(string:String) -> (vowels:Int,consonants:Int,others:Int){

    var vowel = ,consonant = ,other = ;

    for character in string{

        switch String(character).lowercaseString{

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

            ++vowel;

        case "b","c","d","f","g","h","j","k","l","m","n","p","q","r","s","t","v","w","x","y","z":

            ++consonant;

        default:

            ++other;

        }

    }

    return (vowel,consonant,other);

}

let total = count("Some thing is change!");

println("\(total.vowels)元音,\(total.consonants)辅音")

13.4.嵌入函数

func chooseStepFunction(backwards:Bool) -> (Int) -> Int{

    func stepForward(input:Int) -> Int{
        return input +
    }

    func stepBackward(input:Int) -> Int{
        return input -
    }

    return backwards ? stepBackward : stepForward
}

var currentValue = -

// moveNearerToZero是一个函数指针
let moveNearerToZero = chooseStepFunction(currentValue > )

while currentValue != {

    println("\(currentValue)......")

    currentValue = moveNearerToZero(currentValue)

}

14.闭包(Closure)

　　语法：

{(parameters) -> return type in

statements

}

　　示例：数组排序

　　采用函数实现：

let names = ["Chris","Alex","Ewa","Barry","Daniella"]

func backwards(s1:String,s2:String) -> Bool{

    return s1 > s2

}

// sort排序函数，backwards通过排序规则的函数
var reversed = sort(names,backwards)

println(reversed)

　　采用闭包实现：

var reversed = sort(names,{(s1:String,s2:String) -> Bool in 

return s1 > s2

})

println(reversed)

15.类与结构体

　　类和结构体有很多共性：

1. 定义属性存储数据；
2. 定义方法执行功能处理；
3. 定义下标，通过下标访问它们的值；
4. 初始化它们的状态；
5. 通过扩展（Extension）扩展其功能；
6. 遵守协议(Protocol)，协议提供一种特定的标准功能。

　　类比结构体多出的功能：

1. 能够继承另外一个类；
2. 能够核对运行期对象的类型；
3. 析构对象释放资源；
4. 引用计数允许一个类实例有多个引用。

15.1.类和结构体的定义

　　定义类和结构体：

class SomeClass{

// class definition goes here

}

struct SomeStructure{

// structure definition goes here

}

　　示例：

struct Resolution{

var width = 

var height = 

}

class VideoMode{

var resolution = Resolution()

var interfaced = false

var frameRate = 0.0

var name:String?

}

15.2.类和结构体的实例化

struct Resolution{

var width = 

var height = 

}

class VideoMode{

var resolution = Resolution()

var interfaced = false

var frameRate = 0.0

var name:String?

}

let someResolution = Resolution()

// let someResolution = Resolution(width:10,height:20)

let someVideoMode = VideoMode()

16.属性

16.1.属性的存储

　　属性的主要作用是存储数据，可以分为常量属性和变量属性；

struct FixedLengthRange{

    var firstValue:Int

    let length:Int

}

var rangeOfThreeItems = FixedLengthRange(firstValue:,length:)

rangeOfThreeItems.firstValue =
// 注意：length是常量属性，值是不可以修改的

16.2.延时存储属性

　　延时存储属性是初始化时候不分配值，直到第一次使用它。属性@lazy声明。

　　为什么要用延时存储属性？当一个属性是一个庞大类时，并且这个属性很少用到，那么就可以考虑使用延时存储属性，这样可以避免大量数据加载到内存中。

class DataImporter{

    var fileName = "data.txt"

}

class DataManager{

    @lazy var importer = DataImporter()

    var data = ""

} 

let manager = DataManager();

manager.data += "Some Data"

manager.data += "Some more data"

println(manager.importer.fileName)

　　去掉@lazy关键字在playground里面试试，看看有什么不一样？

16.3.计算属性

　　有的时候一些属性是通过其他的属性计算得出的，通过get和set访问器对其访问。

// 定义Point
struct Point{

    var x = 0.0,y = 0.0

}

// 定义Size
struct Size{

    var width = 0.0,height = 0.0

}

// 定义Rect
struct Rect{

    var origin = Point()

    var size = Size()

    var center:Point{

    get{

        let centerX = origin.x + (size.width / )

        let centerY = origin.y + (size.height / )

        return Point(x:centerX,y:centerY)

    }

    set(newCenter){

        origin.x = newCenter.x - (size.width / )

        origin.y = newCenter.y - (size.height / )

    }

    }

}

var square = Rect(origin:Point(x:0.0,y:0.0),size:Size(width:10.0,height:20.0))

let initialSquareCenter = square.center

square.center = Point(x:15.0,y:15.0)

println("square origin is now at (\(square.origin.x),\(square.origin.y))")

16.4.属性观察者

　　为了监听属性的变化，swift通过了属性观察者。

1. willset观察者是在存储之前调用；
2. didSet新值存储后调用。

class StepCounter{

    var totalSteps:Int = {

    willSet(newTotalSteps){

        println("About to set totalSteps to \(newTotalSteps)")

    }
    didSet{

        if totalSteps >= oldValue{

            println("Added \(totalSteps - oldValue) steps")

        }

    }

    }

}

let stepCounter = StepCounter()

stepCounter.totalSteps = 

stepCounter.totalSteps = 

16.5.静态属性

　　静态属性在结构体中使用static定义，类中使用class定义。

struct SomeStructure{

    static var storedTypeProperty = "Some Value"

}

class SomeClass{

    class var computedTypeProperty:Int{

        return 

    }

}

17.方法

　　Swift中的方法是与特定类型(类和结构体)相关的函数

17.1.方法

class Counter{

    var count = 

    func increment(){

        count++

    }

    func incremmentBy(amount:Int){

        count += amount

    }

    func reset(){

        count = 

    }

}

let counter = Counter()

counter.increment()

counter.incremmentBy()

counter.reset()

17.2.使用self

　　self代表当前对象。

struct Point{

    var x = 0.0,y = 0.0

    func isToTheRightOfX(x:Double) -> Bool{

        return self.x > x

    }

}

let somePoint = Point(x:4.0,y:5.0)

if somePoint.isToTheRightOfX(1.0){

    println("This point is to the right of the line where x == 1.0")

}

18.下标

18.1.定义下标

　　还记得字典吗？

var numberOfLegs = ["bird":,"cat":,"ant":]

let birdLeg = numberOfLegs["bird"]

　　["bird"]就是下标

　　下标可以在类和结构体中定义

18.2.只读下标

struct TimesTable{

    let multiplier:Int

    subscript(index:Int) -> Int{

        return multiplier * index

    }

}

let threeTimesTable = TimesTable(multiplier:)

println("six times three is \(threeTimesTable[6])")

19.继承

　　Swift中的类能够继承其他类的属性、方法等。

19.1.定义基类

class Vehicle{

    var numberOfWheels:Int

    var maxPassengers:Int

    func description() -> String{

        return "\(numberOfWheels) wheels;up to \(maxPassengers)"

    }

    init(){

        numberOfWheels = 

        maxPassengers = 

    }

}

let someVehicle = Vehicle()

19.2.定义子类

class Bicycle:Vehicle{

    init() {

        super.init()

        numberOfWheels = 

    }

}

let bicycle = Bicycle()

println("Bicycle:\(bicycle.description())")

19.3.重写(Overriding)

　　子类能够重写父类的方法、属性、下标。

19.3.1方法重写

class Vehicle{

    var numberOfWheels:Int

    var maxPassengers:Int

    func description() -> String{

        return "\(numberOfWheels) wheels;up to \(maxPassengers)"

    }

    init(){

        numberOfWheels = 

        maxPassengers = 

    }

}

class Car:Vehicle{

    var speed:Double = 0.0

    init() {

        super.init()

        numberOfWheels = 

        maxPassengers = 

    }

    override func description() -> String{

        return super.description() + ";" + "traveling at \(speed)"

    }

}

let car = Car()

println("Car:\(car.description())")

19.3.2属性重写

class Vehicle{

    var numberOfWheels:Int

    var maxPassengers:Int

    func description() -> String{

        return "\(numberOfWheels) wheels;up to \(maxPassengers)"

    }

    init(){

        numberOfWheels = 

        maxPassengers = 

    }

}

class Car:Vehicle{

    var speed:Double = 0.0

    init() {

        super.init()

        numberOfWheels = 

        maxPassengers = 

    }

    override func description() -> String{

        return super.description() + ";" + "traveling at \(speed)"

    }

}

class SpeedLimitedCar:Car{

    override var speed:Double{

    get{

        return super.speed

    }
    set{

        super.speed = min(newValue,40.0)

    }

    }

}

let limitedCar = SpeedLimitedCar()

limitedCar.speed = 60.0

println("SpeedLimitedCar:\(limitedCar.description())")

20.构造器(Initializer)

　　为了初始化结构体和类等类型的实例属性。

20.1.默认构造器

struct Fahrenheit{

    var temperature:Double

    init(){

        temperature = 32.0

    }

}

var f = Fahrenheit()  // 调用默认构造器init()，没有参数和返回值

println("The default temperature is \(f.temperature)")

20.2.自定义构造器

　　定义类两个构造器：init(fromFahrenheit:) 和 init(fromKelvin:)

struct Celsius{

    var temperatureInCelsius:Double

    init(fromFahrenheit fahrenheit:Double){

        temperatureInCelsius = (fahrenheit - 32.0) / 1.8

    }

    init(fromKelvin kelvin:Double){

        temperatureInCelsius = kelvin - 273.15

    }

//    init(fahrenheit:Double){

//        temperatureInCelsius = (fahrenheit - 32.0) / 1.8

//    }

//    

//    init(kelvin:Double){

//        temperatureInCelsius = kelvin - 273.15

//    }

}

let boilingPointOfWater = Celsius(fromFahrenheit:212.0)

let freezingPointOfWater = Celsius(fromKelvin:273.15)

//let boilingPointOfWater = Celsius(fahrenheit:212.0)

//let freezingPointOfWater = Celsius(kelvin:273.15)

21.析构器(Deinitializer)

　　析构器与构造器相反，在对象释放时候调用。

　　使用关键字deinit，语法如下：

deinit{

}

　　实例：

class Player{

    var coinsInPurse:Int

    init(coins:Int){

        println("call init")

        coinsInPurse = coins

    }

    func winCoins(coins:Int){

        coinsInPurse += 

    }

    deinit{

        coinsInPurse = 

    }

}

var playerOne:Player? = Player(coins:)

println("PlayerOne has coins \(playerOne!.coinsInPurse)")

playerOne = nil;

22.扩展(Extension)

　　在现有类和结构体的基础上，扩展新的功能。

　　语法：

extension SomeType{

}

extension SomeType:SomeProtocol,AnotherProtocol{

}

　　OC中的扩展：

@interface UIImage (UIImageScale)

22.1.计算属性

extension Double{

    var km:Double{return self * 1000.0}

    var m:Double{return self}

    var cm:Double{return self / 100.0}

    var mm:Double{return self / 1000.0}

}

let oneInch = 25.4.mm

println("OneInch is \(oneInch) meters")

22.2.使用构造器

struct Size{

    var width = 0.0,height = 0.0

}

struct Point{

    var x = 0.0,y = 0.0

}

struct Rect{

    var origin = Point()

    var size = Size()

}

extension Rect{

    init(center:Point,size:Size){

        let originX = center.x - (size.width / )

        let originY = center.y - (size.height / )

        self.init(origin:Point(x:originX,y:originY),size:size)
    }
}

let centerRect = Rect(center:Point(x:4.0,y:4.0),size:Size(width:3.0,height:3.0))

22.3.方法扩展

extension Int{

    func message() -> String{

        var message = "";

        switch self{

        case :

            message = "成功"

        case -:

            message = "用户登录失败"

        default:

            message = "未知错误"

        }

        return message;

    }

}

.message();

.message();

(-).message();

23.协议(Protocol)

　　协议是为方法、属性等定义一套规范，没有具体的实现。协议能够被类、结构体等具体实现。

protocol SomeProtocol{

}

struct SomeStructure:SomeProtocol{

}

class SomeClass:SomeProtocol{

}

23.1.属性

// 1.set和get访问器
protocol SomeProtocol{

    var mustBeSettable:Int{get set}

    var doesNotNeedToBeSettable:Int{get}

}

// 2.静态属性
protocol AnotherProtocol{

    class var someTypeProperty:Int{get set}

}

// 3.只读
protocol FullyNamed{

    var fullName:String{get}

}

　　示例：

protocol FullyNamed{

    var fullName:String{get}

}

struct Person : FullyNamed{

    var fullName:String

}

let john = Person(fullName:"John Appleseed")

class Starship : FullyNamed{

    var prefix:String?

    var name:String

    init(name:String,prefix:String? = nil){

        self.name = name

        self.prefix = prefix

    }

    var fullName:String{

    return (prefix ? prefix! + " " : "") + name

    }

}

var ncc1701 = Starship(name:"Enterprise",prefix:"USS")

println("\(ncc1701.fullName)")

23.2.方法

// 1.定义方法
protocol RandomNumberGenerator{

    func random() -> Double

}

// 2.定义静态方法
protocol SomeProtocol{

    class func someTypeMethod()

}

　　示例：

class LinearCongruentialGenerator:RandomNumberGenerator{

    var lastRandom = 42.0
    let m = 139968.0
    let a = 3877.0
    let c = 29573.0

    func random() -> Double{

        lastRandom = ((lastRandom * a + c) % m)

        return lastRandom / m

    }

}

let generator = LinearCongruentialGenerator()

println("Here's a random number:\(generator.random())")

23.3.把协议作为类型使用

protocol RandomNumberGenerator{

    func random() -> Double

}

class LinearCongruentialGenerator:RandomNumberGenerator{

    var lastRandom = 42.0

    let m = 139968.0

    let a = 3877.0

    let c = 29573.0

    func random() -> Double{

        lastRandom = ((lastRandom * a + c) % m)

        return lastRandom / m

    }

}

class Dice{

    let sides:Int

    let generator:RandomNumberGenerator

    init(sides:Int,generator:RandomNumberGenerator){

        self.sides = sides

        self.generator = generator

    }

    func roll() -> Int{

        return Int(generator.random() * Double(sides)) + 

    }

}

var d6 = Dice(sides:,generator:LinearCongruentialGenerator())

for _ in ...{

    println("Random dice roll is \(d6.roll())")

}

24.Swift的应用

　　在这一部分，我实现了一个小Demo：导航栏和Tab栏结合使用。具体代码说明如下：

24.1.项目结构说明

　　主要文件说明：

1. AppDelegate：系统委托类；
2. TabBarViewController：Tab栏管理类；
3. CustomNavigationController：自定义的导航栏类，在这个类里面，做了4英寸屏和3.5英寸屏的处理；
4. ViewController文件夹：具体的页面控制器；
5. NSStringExt：对String类型的扩展，主要是IOS7的判断、根据字符串长度返回在控件中显示的高度(常用于UITableViewCell中自适应调整Cell的高度使用)；
6. .......

 24.2.运行效果截图

　　iPhone 5S截图：

　　iPhone 4S截图：

 24.3.主要代码

　　AppDelegate里面：

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool
    {
        self.window = UIWindow(frame: UIScreen.mainScreen().bounds)

        var tabbarViewCtrl = TabBarViewController(nibName:nil,bundle:nil);
//        var navigationViewController = UINavigationController(rootViewController:tabbarViewCtrl);

        var navigationViewController = CustomNavigationController(rootViewController: tabbarViewCtrl);
        self.window!.rootViewController = navigationViewController;

        self.window!.makeKeyAndVisible()
        return true
    }

　　TabBarViewController：

    init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?)
    {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)

        self.title = "任务";
    }

    override func viewDidLoad()
    {
        super.viewDidLoad()

        configureTabBar();
    }

    override func didReceiveMemoryWarning()
    {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    /*******************************************************************************
    * 方法名称：configureTabBar
    * 功能描述：配置TabBar控件
    * 输入参数：
    * 输出参数：
    ******************************************************************************/
    func configureTabBar()
    {
        self.view.backgroundColor = UIColor.whiteColor();
        self.tabBar.hidden = true;  // 隐藏自带的Tab
        var width = self.view.frame.size.width;
        var height = self.view.frame.size.height;

        self.myTabbar = UIView(frame:CGRectMake(, height -  - , width, ));
        let currentVersion = UIDevice.currentDevice().systemVersion;

        if (currentVersion.isIos7())
        {
            self.myTabbar!.frame = CGRectMake(, height - , width, );
        }
        self.myTabbar!.backgroundColor = UIColor(patternImage:UIImage(named:"tab_bg_ico.png"));
        self.view.addSubview(self.myTabbar);
        self.view.bringSubviewToFront(self.myTabbar);

        // 任务
        var btnTask = UIButton.buttonWithType(UIButtonType.Custom) as UIButton;  // 后面必须要加上as UIButton
        btnTask.frame = CGRectMake(, , , );
        btnTask.tag = ;
        btnTask.selected = true;
        btnTask.setImage(UIImage(named:"tabtask_sel_ico.png"),forState:UIControlState.Normal);
        btnTask.addTarget(self,action: "tabBarButtonClicked:",forControlEvents:UIControlEvents.TouchUpInside);
        self.myTabbar!.addSubview(btnTask);

        // 单据
        var btnBill = UIButton.buttonWithType(UIButtonType.Custom) as UIButton;
        btnBill.frame = CGRectMake(, , , );
        btnBill.tag = ;
        btnBill.setImage(UIImage(named:"tabbill_nor_ico.png"),forState:UIControlState.Normal);
        btnBill.addTarget(self,action: "tabBarButtonClicked:",forControlEvents:UIControlEvents.TouchUpInside);
        self.myTabbar!.addSubview(btnBill);

        // 查询
        var btnQuery = UIButton.buttonWithType(UIButtonType.Custom) as UIButton;
        btnQuery.frame = CGRectMake(, , , );
        btnQuery.tag = ;
        btnQuery.setImage(UIImage(named:"tabquery_nor_ico.png"),forState:UIControlState.Normal);
        btnQuery.addTarget(self,action: "tabBarButtonClicked:",forControlEvents:UIControlEvents.TouchUpInside);
        self.myTabbar!.addSubview(btnQuery);

        // 设置
        var btnSetting = UIButton.buttonWithType(UIButtonType.Custom) as UIButton;
        btnSetting.frame = CGRectMake(, , , );
        btnSetting.tag = ;
        btnSetting.setImage(UIImage(named:"tabset_nor_ico.png"),forState:UIControlState.Normal);
        btnSetting.addTarget(self,action:"tabBarButtonClicked:",forControlEvents:UIControlEvents.TouchUpInside);
        self.myTabbar!.addSubview(btnSetting);

        var taskViewCtrl = MyTaskViewController(nibName:"MyTaskViewController",bundle:nil);
        var billViewCtrl = MyBillViewController();
        var queryViewCtrl = QueryViewController(nibName:"QueryViewController",bundle:nil);
        var settingViewCtrl = SettingViewController(nibName:"SettingViewController",bundle:nil);

        self.viewControllers = [taskViewCtrl,billViewCtrl,queryViewCtrl,settingViewCtrl];
    }

    /*******************************************************************************
    * 方法名称：configureTabBar
    * 功能描述：配置TabBar控件
    * 输入参数：
        sender:事件源
    * 输出参数：
    ******************************************************************************/
    func tabBarButtonClicked(sender:UIButton)
    {
        var index       = sender.tag;
        var btnTask     = self.view.viewWithTag() as UIButton
        var btnBill     = self.view.viewWithTag() as UIButton
        var btnQuery    = self.view.viewWithTag() as UIButton
        var btnSetting  = self.view.viewWithTag() as UIButton

        switch index{
            case :  // 任务
                self.title = "任务";
                btnTask.selected    = true;
                btnBill.selected    = false;
                btnQuery.selected   = false;
                btnSetting.selected = false;
                btnTask.setImage(UIImage(named:"tabtask_sel_ico.png"),forState:UIControlState.Normal);
                btnBill.setImage(UIImage(named:"tabbill_nor_ico.png"),forState:UIControlState.Normal);
                btnQuery.setImage(UIImage(named:"tabquery_nor_ico.png"),forState:UIControlState.Normal);
                btnSetting.setImage(UIImage(named:"tabset_nor_ico.png"),forState:UIControlState.Normal);
            case :  // 单据
                self.title = "单据";
                btnTask.selected    = false;
                btnBill.selected    = true;
                btnQuery.selected   = false;
                btnSetting.selected = false;
                btnTask.setImage(UIImage(named:"tabtask_nor_ico.png"),forState:UIControlState.Normal);
                btnBill.setImage(UIImage(named:"tabbill_sel_ico.png"),forState:UIControlState.Normal);
                btnQuery.setImage(UIImage(named:"tabquery_nor_ico.png"),forState:UIControlState.Normal);
                btnSetting.setImage(UIImage(named:"tabset_nor_ico.png"),forState:UIControlState.Normal);
            case :  // 查询
                self.title = "查询";
                btnTask.selected    = false;
                btnBill.selected    = false;
                btnQuery.selected   = true;
                btnSetting.selected = false;
                btnTask.setImage(UIImage(named:"tabtask_nor_ico.png"),forState:UIControlState.Normal);
                btnBill.setImage(UIImage(named:"tabbill_nor_ico.png"),forState:UIControlState.Normal);
                btnQuery.setImage(UIImage(named:"tabquery_sel_ico.png"),forState:UIControlState.Normal);
                btnSetting.setImage(UIImage(named:"tabset_nor_ico.png"),forState:UIControlState.Normal);
            case :  // 设置
                self.title = "设置";
                btnTask.selected    = false;
                btnBill.selected    = false;
                btnQuery.selected   = false;
                btnSetting.selected = true;
                btnTask.setImage(UIImage(named:"tabtask_nor_ico.png"),forState:UIControlState.Normal);
                btnBill.setImage(UIImage(named:"tabbill_nor_ico.png"),forState:UIControlState.Normal);
                btnQuery.setImage(UIImage(named:"tabquery_nor_ico.png"),forState:UIControlState.Normal);
                btnSetting.setImage(UIImage(named:"tabset_sel_ico.png"),forState:UIControlState.Normal);
            default:
                println("No Selected Items");
        }

        self.selectedIndex = index - ;
    }

　　CustomNavigationController：

class CustomNavigationController: UINavigationController
{
    init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?)
    {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
        // Custom initialization
    }

    init(rootViewController: UIViewController!)
    {
        return super.init(rootViewController: rootViewController);
    }

    override func viewDidLoad()
    {
        super.viewDidLoad()

        let currentVersion = UIDevice.currentDevice().systemVersion;

        if (currentVersion.isIos7())
        {
            self.navigationBar.setBackgroundImage(UIImage(named:"navbg_ico.png").stretchableImageWithLeftCapWidth(,topCapHeight: ),forBarMetrics:UIBarMetrics.Default);
        }
        else
        {
            self.navigationBar.setBackgroundImage(UIImage(named:"navbg_ico.png"),forBarMetrics:UIBarMetrics.DefaultPrompt);
        }
    }

    override func didReceiveMemoryWarning()
    {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    override func pushViewController(viewController: UIViewController!, animated: Bool)
    {
        super.pushViewController(viewController,animated:animated);
    }

    override func popViewControllerAnimated(animated: Bool) -> UIViewController!
    {
        return super.popViewControllerAnimated(animated);
    }
}

　　MyTaskViewController

    override func viewDidLoad()
    {
        super.viewDidLoad()

        self.tableView.registerClass(UITableViewCell.self,forCellReuseIdentifier: "Cell");
    }

    override func viewWillAppear(animated: Bool)
    {
        var width = self.view.frame.size.width
        var height = self.view.frame.size.height

        self.tableView.frame = CGRectMake(, , width, height - );
    }

    override func didReceiveMemoryWarning()
    {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    // =========================================================================
    // Table view data source

    func numberOfSectionsInTableView(tableView: UITableView!) -> Int
    {
        return ;
    }

    func tableView(tableView: UITableView!, numberOfRowsInSection section: Int) -> Int
    {
        return ;
    }

    func tableView(tableView: UITableView!, heightForRowAtIndexPath indexPath: NSIndexPath!) -> CGFloat
    {
        return ;
    }

    func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCell!
    {
        let cell = tableView .dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell;
        var lblBillCode = UILabel(frame:CGRectMake(,,,));
        lblBillCode.text = "JTBX1404020601";
        lblBillCode.font = UIFont(name: "Arial",size: );

        cell.addSubview(lblBillCode);
        var lblContent = UILabel(frame:CGRectMake(,,,));
        lblContent.text = "市内交通费用报销单";
        lblContent.textAlignment = NSTextAlignment.Right;
        lblContent.font = UIFont(name: "Arial",size: );
        cell.addSubview(lblContent);

        var lblTime = UILabel(frame:CGRectMake(,,,));
        lblTime.text = "2014-05-23 22:10:10";
        lblTime.font = UIFont(name: "Arial",size: );
        lblTime.textColor = UIColor.grayColor();
        lblTime.textAlignment = NSTextAlignment.Right;
        cell.addSubview(lblTime);
        return cell;
    }

    // =========================================================================
    // Table view data delegate

    func tableView(tableView: UITableView!, didSelectRowAtIndexPath indexPath: NSIndexPath!){
        println("row = %d",indexPath.row)
    }

　　NSStringExt：

extension String {

    /*******************************************************************************
    * 方法名称：isIos7
    * 功能描述：配置TabBar控件
    * 输入参数：
    * 输出参数：true:IOS7及以上系统;false:IOS7以下系统。
    ******************************************************************************/
    func isIos7() -> Bool?
    {
        return self >= "7.0"
    }

    func stringHeightWith(fontSize:CGFloat,width:CGFloat)->CGFloat
    {
        var font = UIFont.systemFontOfSize(fontSize)
        var size = CGSizeMake(width,CGFLOAT_MAX)
        var paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.lineBreakMode = .ByWordWrapping;
        var  attributes = [NSFontAttributeName:font,
            NSParagraphStyleAttributeName:paragraphStyle.copy()]

        var text = self as NSString
        var rect = text.boundingRectWithSize(size, options:.UsesLineFragmentOrigin, attributes: attributes, context:nil)
        return rect.size.height
    }
} 

　　源码下载