Swift基础学习笔记

03 April 2015

Swift基础

Swift语言相当灵活，这里做了一下总结，每个特性下面直接用代码做解释。

Variables

var languageName: String = "Swift"

let languageName: String = "Swift"  //常量，安全性和运行速度有优势，所以优先考虑。

var version = 1.0  //推导为Double类型
var version: Double = 1.0 

变量名可以使用Unicode符号，Emojo汉字都可以

String:

let someString = "String"

let components = "~/Documents/ZhaoZhe".pathComponents
// ["~", "Documents", "ZhaoZhe"]

Character:

for character in "Swift" {
	println(character)
}

Combining Strings and Characters:

let china = "a"
let video = "好开心"
let chineseVideo = china + video

Building Complex Strings:

let a = 3, b = 5
let mathResult = "\(a) 乘以 \(b) 等于 \(a * b)"
\\3 乘以 5 等于 15

String Mutability：

var a = "小明"
a += "和小红"

Array and Dictionary:

let components = "~/Documents/ZhaoZhe".pathComponents
// ["~", "Documents", "ZhaoZhe"]

var names = ["ming", "hong", "sang", "four"]

var numberOfLegs = ["ant": 6, "snake": 0, "dog": 4]

var elements = Int[]()

Modify an Array:

var shoppingList = ["松花蛋", "doujiang"]
println(shoppingList[0])
shoppingList += "new"
shoppingList += ["new2", "new3"]
shoppingList[0] = "6颗松花蛋"
shoppingList[3...5] = ["毛豆", "黄瓜"]

Modify a Dictionary:

var numberOfLegs = ["ant": 6, "snake": 0, "dog": 4]
numberOfLegs["蜘蛛"] = 273 //自动添加这条

Retrieving a Value from a Dictionary:

possibleLegCount: Int? = numberOfLegs["章鱼"] //表示可能得到一个值，也可能没有值

if possibleLegCount == nil {
	println("no data")
} else {
	let legCount = possibleLegCount! //强制解包
	println("一只章鱼\(legCount)条腿")
}

等价写法：

if possibleLegCount {
	let legCount = possibleLegCount!
	println("一只章鱼\(legCount)条腿")
}

等价写法：

if let legCount = possibleLegCount {
	println("一只章鱼\(legCount)条腿")
}

If Stagements:

if legCount == 0 {
} else if letCount == 1 {
else {
}

Switch:

switch legCount {
	case 0:
		println("000")
		break //写不写都会执行break
		
	case 1, 3, 5, 7, 9:
		println("111")
		
	case 10...100:
		println("222")
		
	default:
		println("nnn")
}

switch sender {
	case button:
		println("someone tapped button")
		
	case usernameTextField:
		println("someone tapped the text field")
		
	default:
		println("tapped something else")
}

Loops:

while !winCheck() {
	next()

}

for var i = 1; i<=10; ++i {
}

for number in 1...5 {
	//表示1~5所有值，如果是1..5就是1234，不包含5
}

var numberOfLegs = ["ant": 6, "snake": 0, "dog": 4]
for (animalName, legCount) in numberOfLegs {
	println("一只\(animalName)\(legCount)条腿")
}

Functions:

func sayHello() {
	println("Hello")
}

sayHello()

func sayHello(name: String = "路人甲") {
	println("\(name) 你好")
}
sayHello() or sayHello(name: "zhaozhe")


func buildGreeting(name: String = "lurenjia") -> String {
	return name + "Hello"
}
let greeting = buildGreeting()

//Return Multiple Values
func refreshWebPage() -> (Int, String) {
	return (200, "Success")
}
let (statusCode, message) = refreshWebPage()

等价写法：

func refreshWebPage() -> (code: Int, message: String) {
	return (200, "Success")
}
let status = refreshWebPage()
println("Received \(status.code): \(status.message)")

Tuples (元组)

//类似于没有名字的结构体
(2.79, 3.99, 4.19)
(404, "Not Found")

Closures: 闭包

let greetingPrinter = {
	println("Hello World!")
}

等价写法：

let greetingPrinter: () -> () = {
	println("Hello World!")
}

greetingPrinter()

Closure as Parameters:

func repeat(count: Int, task: () -> ()) {
	for i in 0..count {
		task()
	}
}

repeat(2, {
	println("Hello!")
})

Trailing Closures: 依附式闭包

repeat(2) {
	println("Hello!")
}

Classes:

class Vehicle {
	// properties
	// methods
	// initializers
	
	var numberOfWheels = 0 //Stored Properties
	//此处必须设置初始值，或者声明时加?
	
	//Computed Properties
	var description: String {
		get { //get属性是默认的，不写这个声明也可以
			return "\(numberOfWheels)个轮子"
		}
		set {
			//在这里可以通过newValue变量访问新值
		}
	}
}

let someVehicle = Vehicle()
someVehicle.numberOfWheels = 2
println(someVehicle.description)

	

class Bicycle: Vehicle {
	init() {
		super.init() //这个不是必要的，子类初始化与父类无关
		numberOfWheels = 2
	}
}
let myBicycle = Bicycle()

Overriding a Property:

class Car: Vehicle {
	var speed = 0.0
	init() {
		numberOfWheels = 4
	}
	override var description: String {
		return super.description + ", 每小时 \(speed) 英里"
	}
}

Property Observers: 属性观察

class ParentsCar: Car {
	override var speed: Double {
		willSet {
			//这里可以通过newValue变量访问新值
			if newValue > 65.0 {
				println("请小心")
			}
		}
		didSet {
			//在这里可以通过oldValue变量访问旧值
		}
	}
}

Methods:

class Conter {
	var count = 0
	func increment(amount: Int) {
		count += amount
	}
	func resetToCount(count: Int) {
		self.count = count
	}
}

Structures in Swift:

struct Point {
	var x, y: Double
}
struct Size {
	var width, height: Double
}
struct Rect {
	var origin: Point
	var size: Size
	
	var area: Double {
		return size.width * size.height
	}
	
	func isBiggerThanRect(other: Rect) -> Bool {
		return self.area > other.area
	}
}


var point = Point(x: 0.0, y: 0.0)
var size = Size(width: 640.0, height: 480.0)
var rect = Rect(origin: point, size: size)

Structures and Classes:

struct不可继承，class可以

struct在传输的时候是值传递，会复制整个值。class对象是引用传递，传递的是对象的引用

Constants and Variables: Reference Types

let window = Window(frame: frame)  //Window是类
window.title = "Hello!" //这么做是可以的，因为window是个引用，即时是常量的引用也可以修改对象内的值
 
window = Window(frame: frame) //这样不可以

Constants and Variables: Value Types

let point1 = Point(x: 0.0, y: 0.0)  //Point是结构体

point1.x = 5  //不可以这样做

Mutating a Structure:

struct Point {
	var x, y: Double
	
	mutating func moveToTheRightBy(dx: Double) { //mutating是在涉及到修改struct内部变量时必须的
		x += dx
	}
}

let point = Point(x: 0.0, y: 0.0)
point.moveToTheRightBy(200.0)  //错误！！！

Enumerations: 枚举

enum Day: Int {
	case Monday = 1
	case Tuesday = 2
	case Wdnesday = 3, Thursday = 4
}

等价写法：

enum Day: Int {
	case Monday = 1, Tuesday, Wednesday, Thursday
}

let day = Day.thursday	//推导为枚举Day类型
//day 是 Thursday

let dayNumber = Day.Thursday.toRow() //推导为其内部存储Int类型
//dayNumber 是 4


enum Direction {
	case North, South, East, West
}
var direction = Direction.West
direction = .East

let lable = UILable()
lable.textAlignment = .Right

Enumerations: Associated Values

enum TrainStatus {
	case OnTime, Delayed(Int)
	init() {
		self = OnTime
	}
	var description: String {
		switch self {
			case OnTime:
				return "准时到达"
			case Delayed(let minutes):
				return "延误 \(minutes) 分钟"
			default:
				return "准时到达“”
		}
	}
}

var status = .Delayed(42)
println(status.description)
//延误 42 分钟

Nested Types: 类型嵌套

class Train {
	enum Status {
		case ......
		......
	}
}

Extensions: 扩展

extension Size {
	mutating func increaseByFactor(factor: Int) {
		width *= factor
		height *= factor
	}
}

extension Int {
	func repetitions(task: () -> ()) {
		for i in 0..self {
			task()
		}
	}
}

500.repetitions({
	println("赵哲"
})

Generic: 泛型

struct Stack<T> {
	var elements = T[]()
	
	mutating func push(element: T) {
		elements.append(element)
	}
	
	mutating func pop() -> T {
		return elements.removeLast()
	}
}

var stringStack = Stack<String>()
stringStack.push("Hello")
println(stringStack.pop())

Coding 4