Swift基础1_简单数据类型和循环

1 常量变量

var myVariable = 42 //变量myVariable = 50let myConstant = 42 //常量

2 显示指明变量类型

let explicitDouble: Double = 70

3 数组和字典

var shoppingList = ["catfish", "water", "tulips", "blue paint"] shoppingList[1] = "bottle of water"   var occupations = [     "Malcolm": "Captain", //前面是key 后面是value    "Kaylee": "Mechanic", ] occupations["Jayne"] = "Public Relations"

4 创建初始化数组和字典

let emptyArray = String[]() let emptyDictionary = Dictionary<String, Float>() 

5数组添加

var emptyarry = String[]()emptyarry.append("dfd")

6 for循环

let sss = [11,12,43,554,12,434]for i in 0..4 {     print("\(i) = \(sss[i])");         print("\n");      }for i in sss{      print(i);         print("\n");      }

7switch

let vegetable = "red pepper" switch vegetable { case "celery":     let vegetableComment = "Add some raisins and make ants on a log." case "cucumber", "watercress":     let vegetableComment = "That would make a good tea sandwich." case let x where x.hasSuffix("pepper"):     let vegetableComment = "Is it a spicy \(x)?" fallthrough default:     let vegetableComment = "Everything tastes good in soup." }