Swift，闭包

闭包（相当于匿名函数）的几种情况

利用sorted()排序方法来进行示例

1、sorted()正常引用的情况

var str=["d","a","c","b"]
var sort=str.sorted()　　//["a", "b", "c", "d"]

2、设置函数导致sorted()倒序

var str=["d","a","c","b"]
func sortdown(a:String,b:String)->Bool{
　　return	a>b
}
var sort1=str.sorted(by:sortdown)　　//["d", "c", "b", "a"]

3、闭包进行改写

（1）最正常的改写

var str=["d","a","c","b"]
var sort1=str.sorted{(a:String,b:String)->Bool in　　//["d","c","b","a"]
　　return a>b
}

（2）利用函数自动推断，参数和返回值都可以自动推断，return也可以省略

var str=["d","a","c","b"]
var sort1=str.sorted{(a,b)in
　　a>b　　//["d","c","b","a"]
}

（3）利用快捷参数直接引用

var str=["d","a","c","b"]
var sort1=str.sorted{$0>$1}　　//["d","c","b","a"]