Swift 语言概览 -自己在Xcode6 动手写1

原文:Swift 语言概览 -自己在Xcode6
动手写1

Swift是什么？

Swift是苹果于WWDC
2014发布的编程语言，这里引用The
Swift Programming Language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：

1. Swift用来写iOS和OS
   X程序。（估计也不会支持其它屌丝系统）


2. Swift吸取了C和Objective-C的优点，且更加强大易用。


3. Swift可以使用现有的Cocoa和Cocoa
   Touch框架。


4. 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 play

import Cocoa
var str = "Hello, playground"

var str1 = "Hello Wrold!!!"

var str2 = "O(∩_∩)O哈哈~"
// Hello, world

println("Hello, world")
// 变量与常量

// Swift 使用 var 声明 变量 ， let 声明常量

var myVariable = 42

myVariable = 50

let 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 = 94

let width1 = label + String(width)
// 使用 \(item) 的形式进行 字符串格式化

let apples = 3

let orages = 5

let 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<String, Float>()

Xcode贴图

Swift 语言概览 -自己在Xcode6 动手写1