Swift将大数字转换为小数字并附加＆＃39; K＆＃39;或者＆＃39; M＆＃39;

Question

我想用NumberFormatter将一个大数字转换为一个小数字。

910 => 91
45893 => 45

但是我的程序对这个例子不起作用：

910394529348 => 0

我的代码对于小数字是正确的，但是当我的变量＆＃39; powCalc＆＃39;大于7位NumberFormatter返回0.实际上我认为乘数类型（NSNumber）和限制。这是对的吗？

import Foundation
import UIKit

let maximumSignificantDigits: Double = 2
var myValue = 910394529348
let len = ceil (log10 ( Double(myValue)))
var short = Int(len - maximumSignificantDigits)

short -= (short % 3)

var positiveFormat = ""

switch short {
case 0:
    positiveFormat = ""
case 3:
    positiveFormat = "K"
case 6:
    positiveFormat = "M"
default:
    positiveFormat = "etc"
}

let powCalc = 1.0 / pow(10, Double(short))

let numberFormatter = NumberFormatter()
numberFormatter.multiplier =  powCalc as NSNumber!
numberFormatter.maximumFractionDigits = 0

numberFormatter.positiveFormat = "0" + positiveFormat

stride(from: 0, to: myValue, by: myValue / 10).map {counter in
    print(counter, Double(counter) * powCalc, numberFormatter.string(from: NSNumber(value: counter))!)
}

返回＆＃39; myValue＆＃39; 0！

但是如果你将myValue更改为523478或其他程序，那么程序就可以正常工作。