Swift3.0 控制流

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)