一、简单类型

println("say goodbey")　　　　//无需添加”;“ ，也不用java，c等添加main{}函数

let strName = 1024;　　　  　//定义常亮，一次定义多次使用，#default kXXX 45类似

var strPhoneNumber = "hehe";　　//定义变量，系统会自动识别你的类型

let strName :Double = 90.0;　　　//这里可以在初始化时定义其类型

//这里是转换类型

let label = "The width is "
let width = 94
let widthLabel = label + String(width)

//这里实现跟上边一样，两种方式而已

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

//创建数组，字典

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

var occupations = [
"Malcolm": "Captain",
"Kaylee": "Mechanic",
]
occupations["Jayne"] = "Public Relations”

//初始化一个空数组，字典（如果你用过java、c#那么你对泛型有一定理解咯）

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

当然如果不能确定类型可以用

let emptyArray = []()
let emptyDictionary = [:]()

二、逻辑控制

使用if，switch，for in，for，while，do-while，（小括号可省略，方法体的大括号是必须的）

let individualScores = [75, 43, 103, 87, 12]
var teamScore = 0
for score in individualScores{

　　if score > 50 {
　　　　teamScore += 3
　　} else {
　　　　teamScore += 1
　　}
}
teamScore

//下边optionalString变量的类型后有一个问号，代表Hello这个是可选值，当然也可以置为nil表明不存在

var optionalString: String? = "Hello"
optionalString == nil

//if和let一起使用可以防止值丢失

var optionalName: String? = "John Appleseed"
var greeting = "Hello!"
if let name = optionalName {
　　greeting = "Hello, \(name)"
}

//switch与传统的区别在于不在对条件限制为int，而是多种类型，进入case后会跳出，所以不用在写break;这点倒很像apple风格：）

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)?"

}

使用for in即foreach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 = 0
for (kind, numbers) in interestingNumbers {
　　for number in numbers {
　　　　if number > largest {
　　　　　　largest = number
　　　　}
　　}
}
largest

var n = 2
while n < 100 {
　　n = n * 2
}
n

var m = 2
do {
　　m = m * 2
} while m < 100
m

//..的意思是0-3，一个范围：）

var firstForLoop = 0

for i in 0..3 {
　　firstForLoop += i
}
firstForLoop

var secondForLoop = 0
for var i = 0; i < 3; ++i {
　　secondForLoop += 1
}
secondForLoop