René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"swift基础.md","articleBody":"## 检查类型\n\n用类型检查操作符(is)来检查一个实例是否属于特定子类型，返回 true 或 false 。\n## 申明变量\n\n``` swift\nvar aaa = 1 //很长的数值可以用 _ 来分隔，如 111_222.1 = 111222.1\n```\n\n根据值判断变量类型\n## 字符输出\n\n``` swift\nprintln( \"hello \\(aaa) !\" );\n```\n\n`aaa` 将被值替换.\n## 字符串合并\n\n``` swift\nvar b = \"aaa:\" + String(a)\n```\n## 数组\n\n``` swift\nvar shoppingList = [\"catfish\", \"water\", \"tulips\", \"blue paint\"]\n\n\n//key/value 形式\n\nvar occupations = [\n    \"Malcolm\": \"Captain\",\n    \"Kaylee\": \"Mechanic\",\n]\n\noccupations[\"Jayne\"] = \"Public Relations\"\n```\n### 申明空数组\n\n``` swift\nlet emptyArray = [String]() //赋值 emptyArray.append(\"1\")\nlet anyArray = [Any]() //表示任意数据类型的数组\nlet emptyDictionary = [String: Float]()  //赋值 emptyDictionary[\"a\"] = 1.0\n```\n\n用switch来判断读取anyArray数据\n\n``` swift\nfor thing in things {\n    switch thing {\n    case 0 as Int:\n        println(\"zero as an Int\")\n    case 0 as Double:\n        println(\"zero as a Double\")\n    case let someInt as Int:\n        println(\"an integer value of \\(someInt)\")\n    case let someDouble as Double where someDouble \u003e 0:\n        println(\"a positive double value of \\(someDouble)\")\n    case is Double:\n        println(\"some other double value that I don't want to print\")\n    case let someString as String:\n        println(\"a string value of \\\"\\(someString)\\\"\")\n    case let (x, y) as (Double, Double):\n        println(\"an (x, y) point at \\(x), \\(y)\")\n    case let movie as Movie:\n        println(\"a movie called '\\(movie.name)', dir. \\(movie.director)\")\n    default:\n        println(\"something else\")\n    }\n}\n```\n## for-in使用\n\n``` swift\nlet individualScores = [75, 43, 103, 87, 12]\nvar teamScore = 0\nfor score in individualScores {\n    if score \u003e 50 {\n        teamScore += 3\n    } else {\n        teamScore += 1\n    }\n}\n```\n### key/value形式遍历\n\n``` swift\nlet interestingNumbers = [\n    \"Prime\": [2, 3, 5, 7, 11, 13],\n    \"Fibonacci\": [1, 1, 2, 3, 5, 8],\n    \"Square\": [1, 4, 9, 16, 25],\n]\nvar largest = 0\nfor (kind, numbers) in interestingNumbers {\n    for number in numbers {\n        if number \u003e largest {\n            largest = number\n        }\n    }\n}\n```\n## if-else使用\n\n``` swift\nvar optionalString = \"World\" \n\nvar optionalName: String? = \"John Appleseed\"  //申明变量为的值为可选的，不然 optionalName = nil 会报错\noptionalName = nil\n\nvar greeting = \"Hello!\"\n\nif let name = optionalName {  //如果 optionalName 不为 nil 则name将被赋值，不然跳过下面的代码块到else代码块。\n    greeting = \"Hello, \\(name)\"\n}else\n{\n    greeting = \"Hello, \\(optionalString)\"\n}\n\n```\n## switch使用\n\n``` swift\nvar vegetableComment=\"\"\n\nlet vegetable = \"red pepper\"\nswitch vegetable {\ncase \"celery\":\n     vegetableComment = \"Add some raisins and make ants on a log.\"\ncase \"cucumber\", \"watercress\":\n     vegetableComment = \"That would make a good tea sandwich.\"\ncase let x where x.hasSuffix(\"pepper\"): \n     vegetableComment = \"Is it a spicy \\(x)?\"\ndefault:\n     vegetableComment = \"Everything tastes good in soup.\"\n}\n\nprintln(vegetableComment)\n```\n## do,while使用\n\n``` swift\nvar n = 2\n\n//条件在开始\nwhile n \u003c 100 { \n    n = n * 2\n}\n\n//条件在结尾\ndo {\n    m = m * 2\n} while m \u003c 100\n\n\n\n//范围\nvar firstForLoop = 0\nfor i in 0..\u003c4 { //等同于：for var i = 0; i \u003c 4; ++i \n    firstForLoop += i\n}\n\n```\n#0..\u003c4 不包括4，如果要包括4，使用 0...4\n## 函数和闭包\n\n``` swift\n\n//函数申明\n\nfunc greet函数名(name: String, day: String)函数参数 -\u003e返回值 String {\n    return \"Hello \\(name), today is \\(day).\"\n}\ngreet(\"Bob\", \"Tuesday\")\n\nfunc sumOf(numbers: Int...)参数个数不固定 -\u003e Int {\n    var sum = 0\n    for number in numbers {\n        sum += number\n    }\n    return sum\n}\nsumOf()\nsumOf(42, 597, 12)\n\n\n//返回一个元组\nfunc calculateStatistics(scores: [Int]) -\u003e (min2: Int, max2: Int, sum2: Int) {\n    var min = scores[0]\n    var max = scores[0]\n    var sum = 0\n\n    for score in scores {\n        if score \u003e max {\n            max = score\n        } else if score \u003c min {\n            min = score\n        }\n        sum += score\n    }\n\n    return (min, max, sum)\n}\nlet statistics = calculateStatistics([5, 3, 100, 3, 9])\n\nprintln(statistics)\nprintln(statistics.sum2) //使用返回元组的名称来取值\nprintln(statistics.1) //索引来取值\n\n//输出结果：\n//(3, 100, 120)\n//120\n//100\n\n\n\n//函数做为返回值，以及函数嵌套\nfunc makeIncrementer() -\u003e (String -\u003e Int) {   //(String -\u003e Int) 与返回函数的参数数据类型和返回值相同\n    func addOne(number: String) -\u003e Int {\n         var a:Int? = number.toInt()\n         if let b = a\n         {\n            return 1+b\n         }\n         else {return 1}\n    }\n    return addOne\n}\nvar increment = makeIncrementer() //调用了makeIncrementer函数，返回addOne函数\nprintln(increment(\"7\"))  //return 8\n\n\n//函数当做参数传入另一个函数\nfunc hasAnyMatches(list: [Int], condition: Int -\u003e Bool) -\u003e Bool { //condition: Int -\u003e Bool 参数函数的值和返回值定义\n    for item in list {\n        if condition(item) {\n            return true\n        }\n    }\n    return false\n}\nfunc lessThanTen(number: Int) -\u003e Bool {\n    return number \u003c 10\n}\nvar numbers = [20, 19, 7, 12]\nhasAnyMatches(numbers, lessThanTen)\n\n//使用尾随闭包\n\nhasAnyMatches(numbers){number -\u003e Bool  in \n   return number \u003c 10\n}\n\n//或者\n\nhasAnyMatches(numbers){\n   number \u003c 10\n}\n```\n### 闭包\n\n``` swift\nlet closure1  = {\n    (number: Int) -\u003e Int in  //用in将参数和返回值类型声明与闭包函数体进行分离\n    let result = 3 * number\n    return result\n}\n//等同于：\nlet closure1  = {number in 3 * number} //参数类型默认为Int型，通过 3* 来自动识别，返回计算结果\n//等同于：\nlet closure1  = {3 * $0} //一切都是默认的，使用参数位置来访问参数\n\nprintln(closure1(1))\n```\n## 对象和类\n\n``` swift\nclass NamedShape {\n    var numberOfSides: Int = 0\n    var name: String  //必须被初始化，或者定义为：var name: String?\n\n    init(name: String) {  //构造方法\n        self.name = name //初始化 name\n    }\n    deinit {\n        println(\"deinitialized\")\n    }\n    func simpleDescription() -\u003e String {\n        return \"A shape with \\(numberOfSides) sides.\"\n    }\n}\n\n//继承\nclass EquilateralTriangle: NamedShape {\n    var sideLength: Double = 0.0\n\n    init(sideLength: Double, name: String) {\n        self.sideLength = sideLength\n        super.init(name: name) //父方法\n        numberOfSides = 3 //父变量\n    }\n\n    var perimeter: Double {  //geter 和 seter 方法，不能和 willSet（set前） 和 didSet（set后） 共存\n        set {\n            sideLength = newValue / 3.0\n        }\n        get {\n            return 3.0 * sideLength\n        }\n    }\n\n    override func simpleDescription() -\u003e String {  //覆盖父方法\n        return \"An equilateral triagle with sides of length \\(sideLength).\"\n    }\n}\n\nclass Triangle {\n    var triangle: EquilateralTriangle { //申明 类 类型的变量\n        willSet {\n            println(newValue)\n        }\n    }\n    var square:Double = 1{  //同时初始化\n        willSet {\n            triangle.sideLength = newValue\n            println(\"willSet \\(newValue)\")\n        }\n        didSet(oldValue2) {\n            println(\"didSet \\(oldValue2)\")\n        }\n    }\n    init(size: Double, name: String) {\n        println(\"init\")\n        triangle = EquilateralTriangle(sideLength: size, name: name)  //初始化变量\n    }\n}\n\nvar t = Triangle(size: 12, name: \"assd\")\nt.square=21\n\n```\n### didSet 实例\n\n``` swift\nclass Foo\n{\n    var propertyChangedListener : (Int, Int) -\u003e Void = {  //一个返回为空，有两个参数的类方法\n        println(\"The value of myProperty has changed from \\($0) to \\($1)\")\n    }\n\n    var myProperty : Int = 0 {\n        didSet { propertyChangedListener(oldValue, self.myProperty) }\n    }\n}\nvar f = Foo()\nf.myProperty = 1\n```\n## 枚举\n\n``` swift\nenum CompassPoint:Int {\n  case North=1  //case 可以是一行或多行。给枚举项添加一个原始值如1，则其它的会自动叠加，如South值为2\n  case South,East\n  case West\n\n  func simpleDescription() -\u003e String { //扩展一个方法\n        switch self {\n        case .North:\n            return \"北\"\n        case .South:\n            return \"南\"\n        case .East:\n            return \"东\"\n        case .West:\n            return \"西\"\n        default:\n            return String(self.rawValue)\n        }\n    }\n}\n\nvar c = CompassPoint.North.rawValue //读取原始值\nvar c2 = CompassPoint.North //CompassPoint.init(rawValue:2) 通过原始值来取值\n\nprintln(c)\n\nc2 = .East //已知为CompassPoint类型，可以直接.East\n\nswitch c2 {\n    case .East :\n        println(c2.simpleDescription())\n    case .North :\n        println(\"c2\")\n    default:\n        println(\"aa\")\n}\n\n//相关值\n//原始值是预先设置好的，可以通过rawValue读取。而相关值是可以在具体使用过程中指定。\nenum Barcode {\n  case UPCA(Int, Int, Int) \n  case QRCode(String)\n}\n\nvar productBarcode = Barcode.UPCA(8, 85_909_51226, 3)\nproductBarcode = .QRCode(\"ABCDEFGHIJKLMNOP\")\n\n//读取相关值，注意let的用法。\nswitch productBarcode {\n    case .UPCA(let numberSystem, let identifier, let check):\n        println(\"UPC-A with value of \\(numberSystem), \\(identifier), \\(check).\")\n    case let .QRCode(productCode):\n        println(\"QR code with value of \\(productCode).\")\n}\n```\n## 协议（接口）和扩展\n### 协议\n\n``` swift\nprotocol ExampleProtocol {\n    var simpleDescription: String { get }\n    mutating func adjust() //如果是枚举或结构实现此协议，在方法前加mutating，协议方法前面必须加mutating关键字。\n}\n\nclass SimpleClass: ExampleProtocol {\n    var simpleDescription: String = \"A very simple class.\"\n    var anotherProperty: Int = 69105\n    func adjust() {  //类方法前不需要加mutating\n        simpleDescription += \"  Now 100% adjusted.\"\n    }\n}\nvar a = SimpleClass()\na.adjust()\n```\n### 扩展\n\n``` swift\nextension Int: ExampleProtocol {  //对原生的类方法扩展额外的功能\n    var simpleDescription: String { //给Int型数据添加方法simpleDescription\n        return \"The number \\(self)\"\n    }\n    mutating func adjust() { //使用mutating关键词声明了一个方法adjust改动了Int结构\n        self += 42\n    }\n}\n\n或者：\nextension Int { \n    var simpleDescription: String { \n        return \"The number \\(self)\"\n    }\n}\n\nprintln(7.simpleDescription)\n```\n## 泛型\n\n``` swift\nfunc repeat\u003cItemType先预设一个未知数据类型供在参数或函数体里使用\u003e(item: ItemType, times: Int) -\u003e [ItemType] {  //ItemType 将被自动识别为String\n    var result = [ItemType]() \n    for i in 0..\u003ctimes {\n        result.append(item)\n    }\n    return result\n}\nrepeat(\"knock\", 4)\n```\n## 类和结构\n\n类和结构基本相同，最大的区别是类是**引用类型**，结构是**值类型**！\n### 闭包和函数也是 引用类型\n\n引用类型就是变量和它赋值的类、函数或闭包指向同一内存位置。参考\nhttp://numbbbbb.gitbooks.io/-the-swift-programming-language-/content/chapter2/07_Closures.html#closures_are_reference_types\n\n``` swift\n//定义一个结构，里面的变量自动生成构造\nstruct task{\n    var name = \"name\"\n    var desc = \"desc\"\n}\nvar t1 = task(name:\"1\", desc:\"222\") //结构里面的变量自动生成构造\nvar t2 = t1\nt2.name = \"name xxx\" //不影响t1的值\nprintln(t1.name)\n\n\nclass a{\n    var a = 1\n    var b = 2\n}\nvar a1 = a()\nvar a2 = a1\na2.a=3 //会影响a1的值\nprintln(a1.a)\n```\n","author":{"url":"https://github.com/aliencode","@type":"Person","name":"aliencode"},"datePublished":"2014-12-18T05:32:35.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/1/aliencode.github.io/issues/1"}