Swift - 控制流/控制结构说明(if,switch,for,while)
一、if 语句
let count = 7 if 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 = 3 switch 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 = 2 switch 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 = 2.0 switch 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) in print(C) } (1...10).forEach { print($0) }
四、while 循环语句
var i = 0 while i < 10 { i += 1 print(i) } repeat{ i += 1 print(i) }while i<100