在小数点分隔符之前和之后打印两位数字的双精度打印

使用方式如下:

let str = NSString(format: "%05.2f",  myValueToPrint as! Double)

NumberFormatter

let a_double: Double = 2.348

let formatter: NumberFormatter = NumberFormatter()
formatter.numberStyle = .decimal
formatter.format = "#,##00.00"


if let the_value = formatter.string(from: NSNumber(value: a_double))
{
    print(the_value) // 02.35
}