开始swift

1.var声明变量，let声明常量

var myVariable = 42
myVariable = 50
let myConstant = 42

 

2.指定类型时

let explicitDouble : Double = 70

 

3.强转类型

let str = "my age is "+(String)22

 

4.字符串拼接

let age = 18
let str   =  "my age is "+(String)age 
let str2 =  "my age is \(age )"

5.数字和字典

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