Swift学习第一天

转载链接：http://www.cocoachina.com/newbie/basic/2014/0604/8675.html

备忘录：http://www.cocoachina.com/applenews/devnews/2014/0604/8663.html

1. SWift我来了，hello world！

println("hello, world")

备注：这行代码就是一个完整的程序，不需要导入库，不需要main函数入口，末尾连分号也不再需要。

2. 使用let来声明常量，使用var来声明变量

var myVariable = 42
myVariable = 50
let myConstant = 42

自动检测类型

let implicitInteger = 70
let implicitDouble = 70.0
let explicitDouble: Double = 70

值永远不会被隐式转换为其他类型。如果你需要把一个值转换成其他类型，请显式转换

例如：String() 或 \()

let width = 30
let widthLable = "The width is \(width)"
let widthLabel1 = "The width is" + String(width)
let widthLable2 = "Phone" + " width is \(width)"

3. 使用方括号[]来创建数组和字典，并使用下标或者键（key）来访问元素。

var shoppingList = ["catfish", "water", "tulips", "blue paint"]
shoppingList[1] = "bottle of water"

var occupations = [
    "key1": "value1",
]
occupations["key2"] = "value2"
occupations["key1"] = "value111"

要创建一个空数组或者字典，使用初始化语法

let emptyArray = String[]()
let emptyDictionary = Dictionary<String, Float>()

3. Swith中运行switch中匹配到的子句之后，程序会退出switch语句，并不会继续向下运行，所以不需要在每个子句结尾写break

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

let n = 2
switch n {
case 1:
    println("It's 1!")
case 2...4:
    println("It's between 2 and 4!")
case 2..4:
println("It's between 2 and 3!")
case 5, 6:
    println("It's 5 or 6")
default:
    println("Its another number!")
}

备注：...是右闭区间 ..则相反

4. 使用func来声明一个函数，使用名字和参数来调用函数。使用->来指定函数返回值。

func greet(name: String, day: String) -> String {
    return "Hello \(name), today is \(day)."
}
greet("Bob", "Tuesday")

备注：使用起来像一个闭包