Swift - 数字格式化转成字符串（保留两位小数，十六进制前面补0等）

1、下面是一个浮点类型的数字转成String字符串的例子

var f = 123.32342342
var s:String = "\(f)" //123.32342342

2、如果要保留两位小数

var f = 123.32342342
var s = String(format: "%.2f", f) //123.32

3、转成十六进制格式字符串

let i = 255
let s:String = String(format: "%x", i) //ff

4、不足六位前面补0

let i = 255
let s:String = String(format: "%06x", i) //0000ff

https://www.hangge.com/blog/cache/detail_699.html