1，if语句

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if count >=3 {      println ( "yes" ) } else {      println ( "no" ) }

2，switch语句 

（1）Swift中不需要在case块中显示地使用break跳出switch。如果想要实现C风格的落入特性，可以给需要的case分支插入fallthrough语句

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var fruit = "apple" switch fruit{      case "apple" :          println ( "good" )          fallthrough      case "banana" , "orange" :          println ( "great" )      default :          println ( "bad" ) }

（2）case分支还可以进行区间匹配

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var age = 5 switch age {      case 0...11:          println ( "正太" )      case 12...30:          println ( "少年" )      default :          println ( "大叔" ) }

（3）使用元组匹配（判断属于哪个象限）

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let point = (2,2) switch point {      case (0,0):          println ( "坐标在原点" )      case (_,0):          println ( "坐标在x轴上" )      case (0,_):          println ( "坐标在y轴上" )      case (-3...3, -3...3):          println ( "坐标在长宽为6的正方形内" )      default :          println ( "在什么地方" ) }

（4）case中还可以使用where关键字来做额外的判断条件

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var height = 1.72 switch height{      case 1...3 where height == 1.72:          println ( "case 1" )      case 1...3 where height == 2:          println ( "case 2" )      default :          println ( "default" ) }

3，for循环语句 

（1）for条件递增循环

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for var i=1; i<100; i++ {      println ( "\(i)" ) }

（2）for-in循环

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for i in 1..<100{      println ( "\(i)" ) }   //遍历数组元素 let numbers = [1,2,4,7] for num in numbers{      println ( "\(num)" ) }   //遍历字典 let nameOfAge = [ "lily" :18, "Candy" :24] for (aName, iAge) in nameOfAge{      println ( "\(aName) is \(iAge)" ) }   //遍历字符串的字符 for chare in "hangge" {      println (chare) }

4，while循环语句

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while i<100 {      i++ }   do{      i++ } while i<100