摘要：
//: Playground - noun: a place where people can play import UIKit var str = "Hello, playground" //赋值符号 //var a = 3 //控制流 （顺序结构， 循环结构， 选择结构） //循环结构 //f 阅读全文
摘要：
//: Playground - noun: a place where people can play import UIKit var str = "Hello, playground" //常量 let let maxNum = 1000 //maxNum = 2000 //变量 var va 阅读全文