Swift 学习笔记-Basic

感谢Github上The Swift Programming Language开源翻译的中文版，感谢极客学院wiki提供的PDF版本
SwiftTour是对Swift主要的语言特性有个速览，后续的教程会逐个展开阐述。
代码上传至Github，有兴趣的可以下载下来试试

import UIKitvar str = "Hello, World!"print(str)// 变量用var声明，常量用let声明，变量类型自动推断// 可在变量后声明类型，用冒号分隔var myVariable = 42let myConstant = 42myVariable = 50let explictDouble: Double = 60// 值永远不会被隐式转换为其他类型，需要转换必须采用显式转换let label = "The width is "let width = 94let widthLabel = label + String(width)

更为常见的将值转换为字符串的方法

let apples = 3let oranges = 5let appleSummary = "I have \(apples) apples"let fruitSummary = "I have \(apples + oranges) pieces of fruit"

[]用来创建数组或字典

var shoppingList = ["catfish", "water", "tulips", "blue paint"]shoppingList[1]  = "bottle of water"var occupations = [    "Malcolm": "Captain",    "Kaylee": "Mechanic"]occupations["Jayne"] = "Public Relations"

创建一个空数组或者字典

let emptyArray1 = [String]()let emptyDictionary1 = [String: Float]()let emptyArray2: [String] = []let emptyDictionary2: [String: Float] = [:]

控制流，if和switch用于选择，for-in,for,while和repeat-while用于循环

let individualScores = [75, 43, 103, 87, 12]var teamScore = 0for score in individualScores {    if score > 50 {        teamScore += 3    } else {        teamScore += 1    }}print(teamScore)

隐式

// 由于不支持隐式转换，条件必须是一个布尔表达式// 一般采用可选值配合if和let，处理值缺失判断var optionalString: String? = "Hello"print(optionalString == nil)var optionalName: String? = "John Appleseed"var greeting = "Hello"if let name = optionalName {    greeting = "Hello, \(name)"}

Switch支持任意类型的数据以及各种比较操作

let vegetable = "red pepper"switch vegetable {case "celery" :    print("Add some raisins and make ants on a log")case "cucumber", "watercress" :    print("That woould make a good tea sandwich")case let x where x.hasSuffix("pepper") :    print("Is it a spicy \(x)?")default :    print("Everything tastes good in soup")}

使用for-in遍历字典

// 使用for-in遍历字典let interestingNumbers = [    "Prime": [2, 3, 5, 7, 11, 13],    "Fibonacci": [1, 1, 2, 3, 5, 8],    "Square": [1, 4, 9, 16, 25],]var largest = 0var numberGroup: String = "Null"for (kind, numbers) in interestingNumbers {    for number in numbers {        if number > largest {            largest = number            numberGroup = kind        }    }}print(numberGroup, largest)

while循环

// while循环var n = 2while n < 100 {    n = n * 2}print(n)var m = 2repeat {    m = m * 2} while m < 100print(m)

可以在循环中使用..<来表示范围,包含上界使用…

var firstForLoop = 0for i in 0..<4 {    firstForLoop += i}print(firstForLoop)var secondForLoop = 0for var i = 0; i < 4; ++i {    secondForLoop += i}print(secondForLoop)