Var 定义变量

Let 定义常量

printf() 打印

var num = 1 //int变量

var num = 10.0 //double 变量

字符串

NSString ---> String "String" 直接双引号 可以像脚本语言一样直接对字符串想加减,可以带入变量

let c = "cap"

let d = "I have \(c) apples"// \(c)将常量c填充入字符串，类似format、

数组

NSArray --->声明空数组的话使用[] 或者let emptyArray = [String]()

let arr = ["a","b","c"]

NSMutableArray--->

var arr = ["a","c"]

arr[0] = "apple" //替换元素

字典

NSDictionary--->声明空字典的话使用[:] 或者let emptyDictionary = [String: Float]()

let dic = ["keyA":"A","keyB":"b","keyC":"c"]

NSMutableDictionary--->

var dic = ["keyA":"A","keyC":"c"]

//addobject 添加

dic["KeyD"]="D" //相当于字典addobject

//setobject 设置

dic["D"] = "Dan"

print("dic=",dic)

//removeObjectForKey 移除某个key和对应的键值

dic["D"] = nil

//removeAllobject 移除所有

dic = [:]

print("dic)