常用的一些判断方式
//for in let numberList = [1, 2, 3, 4, 5] //获取第一个元素 !拆包 print(numberList.first!)//1 //获取最后一个元素 print(numberList.last!)//5 //获取元素下标,和对应的元素 for num in numberList.enumerated() { print("\(num.offset)\(num.element)") } //元素倒序 for (index, item) in numberList.enumerated().reversed() { print("\(index)\(item)") } //过滤元素(filter) for (index, item) in numberList.enumerated().filter({ (index, item) in index > 1 && index < 3 }) { print("\(index):\(item)") } for(index,item) in numberList.enumerated().filter({ (i,g) -> Bool in i > 2}){ print("\(index):\(item)") }
//if let time = 10 if time < 8 { print("继续睡觉") }else{ print("起床") } } //guard 与 if 相似, 当条件为false ,才会执行 func guardCase(){ let time = 10 guard time == 8 else { print("出去打球") return } print("下雨了") } //switch let dot = (0,0) switch dot { case (0,0): print("原点") break case (10,0): print("x轴上的点") break case (0,50): print("y轴上的点") break default: break } //repeat - while 条件成立会继续执行 var i = 0 repeat { i += 1 print(i) }while i < 10 print(i) //while var g = 20 while g > 0 { g -= 2 print(g) } //g 等于0 的时候回跳出while循环 print(g)