Swift是什么？
Swift是苹果于WWDC 2014发布的编程语言，这里引用的原话：
Swift is a new programming language for iOS and OS X apps that builds on the best of C and Objective-C, without the constraints of C compatibility.
Swift adopts safe programming patterns and adds modern features to make programming easier, more flexible and more fun.
Swift’s clean slate, backed by the mature and much-loved Cocoa and Cocoa Touch frameworks, is an opportunity to imagine how software development works.
Swift is the first industrial-quality systems programming language that is as expressive and enjoyable as a scripting language.
简单的说：
- Swift用来写iOS和OS X程序。（估计也不会支持其它屌丝系统）
- Swift吸取了C和Objective-C的优点，且更加强大易用。
- Swift可以使用现有的Cocoa和Cocoa Touch框架。
- Swift兼具编译语言的高性能（Performance）和脚本语言的交互性（Interactive）。
Swift语言概览
// Playground - noun: a place where people can playimport Cocoavar str = "Hello, playground"var str1 = "Hello Wrold!!!"var str2 = "O(∩_∩)O哈哈~"// Hello, worldprintln("Hello, world")// 变量与常量// Swift 使用 var 声明 变量 ， let 声明常量var myVariable = 42myVariable = 50let myConstant = 42// 类型推导let explicitDouble : Double = 70// Swift 不支持隐式 类型转换 （所以需要显式类型转换）let label = "The width is"let width = 94let width1 = label + String(width)// 使用 \(item) 的形式进行 字符串格式化let apples = 3let orages = 5let sum = "I have \(apples) apples."let sum1 = "I have \(apples + orages) pieces of fruit."// 数组和字典// Swift 使用[] 操作符声明 数组（array）和字典 （dictionary）var listArr = ["fish","water","apple","rice"]listArr[1] = "bottle of water"var dict = [ "name": "melody", "age" : "26",]dict["sex"] = "female"// 一般使用初始化器（initializer）语法创建空数组和空字典let emptyArray = String[]()let emptyDict = Dictionary () Xcode贴图
