前言
在OC中对一个数组排序，以及字典的排序往往都是自己写一个函数去实现。swift中就不用再自己再去做这样的事了。Swift提供了sort函数，可以让数组和字典很方便的实现排序。
简单使用
降序
let a = ["2","1","3"] let i = a.sort { (s1, s2) -> Bool in return s1 > s2} print("\(t)")//打印结果：["3","2","1"]
升序
let a = ["2","1","3"] let i = a.sort { (s1, s2) -> Boolin return s1 < s2} print("\(i)")//打印结果：["1","2","3"]
优化版
let a = ["2","1","3"] let i = a.sort{$0<$1} print("\(i)")//打印结果：["1","2","3"]
在Swift中闭包参数是可以缺省的，可以根据类型推断直接省略参数类型和参数名，用$0代表闭包的第一个参数，$1代表闭包的第二个参数......以此类推。同时也可以省略in关键字。
最简版
let a = ["2","1","3"] let i = a.sort(<) print("\(i)")//打印结果：["1","2","3"]
