学步园

1 常量变量

var myVariable = 42 //变量
myVariable = 50
let 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." 
}