NSNumberFormatter maximumFractionDigits和maximumSignificantDigits错误 [英] NSNumberFormatter maximumFractionDigits and maximumSignificantDigits bug

问题描述

在iOS 8的NSNumberForamtter上同时使用maximumFractionDigits和maximumSignificantDigits时，这是一个错误吗?

Is this a bug when using maximumFractionDigits and maximumSignificantDigits together on NSNumberForamtter on iOS 8?

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
formatter.maximumFractionDigits = 2;  
formatter.maximumSignificantDigits = 3;
NSLog(@"%@", [formatter stringFromNumber:@(0.3333)]); // output 0.333 expected 0.33

如果我仅使用maximumFractionDigits

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
formatter.maximumFractionDigits = 2;
NSLog(@"%@", [formatter stringFromNumber:@(0.3333)]); // output expected .33

推荐答案

这不是错误.从文档中:

It isn't a bug. From the docs:

注意

将数字格式化程序配置为使用有效数字时，它将忽略用于设置整数或小数位的任何最小值或最大值.

When a number formatter is configured to use significant digits, it ignores any minimum or maximum values used to set integer or fraction digits.

https://developer.apple.com/documentation /foundation/nsnumberformatter/1417793-usessignificantdigits?language = objc

注意:如果maximumSignificantDigits或minimumSignificantDigits设置为任何值，则usesSignificantDigits将自动设置为true.这与maximumSignificantDigits和minimumSignificantDigits的文档相反:

Note: If either maximumSignificantDigits or minimumSignificantDigits is set to any value, then usesSignificantDigits is automatically set to true. This contradicts the docs for maximumSignificantDigits and minimumSignificantDigits which says:

您必须将usesSignificantDigits属性设置为true，以便此属性影响格式设置行为.

You must set the usesSignificantDigits property to true in order for this property to affect formatting behavior.

您无需将usesSignificantDigits设置为true，它将自身设置为true.

You don't need to set usesSignificantDigits to true, it will set itself to true.

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