如何防止iPhone NSNumberFormatter四舍五入？

问题描述

我要尝试格式化大型货币数字，例如：

  NSNumber * testVal = [NSDecimalNumber decimalNumberWithString：@999999999999999993.00 ]; 
 NSNumberFormatter * formatter = [[NSNumberFormatter alloc] init]; 
 [formatter setNumberStyle：NSNumberFormatterCurrencyStyle]; 
 [formatter setMaximumIntegerDigits：19]; 
 [formatter setMaximumFractionDigits：0]; 
 NSNumberFormatter * formatter = [Formatters numberFormatterForField：f]; 
 NSLog（[formatter stringFromNumber：testVal]）; 
 

忽略Locale的影响一会儿，我发现我一直得到以下输出，舍入：

  1,000,000,000,000,000,000 
  


b $ b

我期望：

  999,999,999,999,999,993 
  

我试过改变舍入没有效果。为什么 NSNumberFormatter 坚持舍入？

解决方案

NSNumberFormatter 在显示之前将数字转换为double，这不是你想要的。 NSDecimalNumber 有一个符合您需要的 descriptionWithLocale：方法。

请参阅以下答案：

I'm trying to format large currency numbers like this:

NSNumber *testVal = [NSDecimalNumber decimalNumberWithString: @"999999999999999993.00"];
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setNumberStyle:NSNumberFormatterCurrencyStyle];
[formatter setMaximumIntegerDigits:19];
[formatter setMaximumFractionDigits:0];
NSNumberFormatter *formatter = [Formatters numberFormatterForField:f];
NSLog([formatter stringFromNumber:testVal]);

Ignoring the effect of Locale for a moment, I find that I consistently get the following output regardless of the rounding:

1,000,000,000,000,000,000

I expect:

999,999,999,999,999,993

I've tried changing the rounding with no effect. Why does NSNumberFormatter insist on rounding up?

解决方案

NSNumberFormatter converts the number to a double before displaying, so that's not what you want. NSDecimalNumber has a descriptionWithLocale: method that should suit your needs.

See this answer: link

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