一、if 语句
let count = 7if count > 1{print("yes")}else{print("no")}
二、switch 语句
（1）Swift中不需要在case块中显示地使用break跳出switch。
let fruit = "apple"switch fruit {case "aaple":print("good")case "banana","orange":print("great")default:print("bad")}
（2）case分支还可以进行区间匹配
let age = 3switch age {case 0...11:print("正太")case 12...13:print("少年")default:print("中年")}
（3）case分支同样支持单侧区间匹配
let num = 2switch num {case ..<0:print("负数")case 0:print("零")case 0...:print("正数")default:print("未知")}
（4）使用元组匹配（判断属于哪个象限）
let point = (2,2)switch point {case (0,0):print("坐标在原点")case (_,0):print("坐标在x轴上")case (0,_):print("坐标在y轴上")case (-2...2,-2...2):print("坐标在长宽为4的正方形内")default:print("未知")}
（4）case中还可以使用where关键字来做额外的判断条件
var height = 2.0switch height {case 1...3 where height == 1.72:print("case 1")case 1...3 where height == 2.0:print("case 2")default:print("default")}
三、for 循环语句
（1）for-in循环
for i in 1..<10{print("\(i)")}//遍历数组let numbers = [1,2,4,7]for num in numbers{print("\(num)")}//遍历字典let nameOfAge = ["lily":18,"Candy":24]for(aName, iAge)in nameOfAge{print("\(aName) is \(iAge)")}//遍历字符串的字符"helloWorld".forEach { (C) inprint(C)}(1...10).forEach {print($0)}
四、while 循环语句
var i = 0while i < 10 {i += 1print(i)}repeat{i += 1print(i)}while i<100
