swift(01)基础学习

//常量和变量

var myNumber = 42

let myConst = 32

var myVar:Double = 20

let myFloat:Float = 15

//字符串

let label = "hello width"

let width = 20

let widthLabel = label+String(width)

print(widthLabel)

//值转为字符串,直接使用反斜杠转换()

let apples = 3

let oringle = 5

let applesummary = "i have (apples)"

print(applesummary)

//数组,直接赋值

var fruitList = ["apple","oriangle","banana"]

print(fruitList)

//创建空数组

let emptyArray = [String]()

print(emptyArray)

//字典,27)"> var fruitDis = ["1":"apple","2":"orignale"]

print(fruitDis)

//创建空字典

let emptyDic = [String]()

print(emptyDic)

//控制流if,switch,for-in for while repeat-while

//需要注意的是它们之间的空格必须要有.并且在if语句中,条件必须要是一个布尔表达式,系统不会默认给判断

let indiviNumber = [11,21,31,41]

var teamScore = 0

for score in indiviNumber{

if score > 21

{

teamScore += 1

}else{

teamScore += 2

}

}

print(teamScore)

//这里加一个问号是说明可选字符串

var optionString:String? = "lihuan"

print(optionString == nil)

//switch语句

let vegetable = "red pepper"

switch vegetable {

case "apple":print("hello")

case "red pepper":print("right")

default:print("wrong")

}

//for in 遍历的使用,遍历字典

let intestNumber = ["prime":[1,2,3,4],"fibonacci":[5,6,7,8],]

var largest = 0

for(kind,numbers) in intestNumber {

for number in numbers {

if number > largest {

largest = number

}

}

}

print(largest)

//while 的使用

var n = 2

while n < 100 {

n = n*2

}

print(n)

//repeat-while的使用

var m = 5

repeat {

m = m*5

} while m < 100

print(m)

//for 循环

var loopNumber = 0

for i in 0..<4 {

loopNumber += i

}

print(loopNumber)

//另一种写法,不建议使用

var loopSecond = 0

for var i = 0; i < 4; ++i {

loopSecond += i

}

print(loopSecond)

// 函数和闭包

// 使用func 来生明,使用名字和参数来调用函数 使用 -> 来指定函数返回值的类型

//greet是函数名,name和day是变量 void是返回值类型

func greet (name:String,day:String) -> Void {

print ("hello (name),today is (day)")

}

//使用函数

greet("lee",day:"monday")

//计算参数平均值方法

func avergae (numbers:[Double],index:Int) -> Double {

var sum:Double = 0

for number in numbers {

sum += number

}

return sum/Double(index)

}

print(avergae([1,2.3,3],index: 3))

（编辑：李大同）

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