ios - NSDateComponentsFormatter 的方法 stringFromDate :ToDate: is returning a different value every second

Question

我正在尝试获取今天日期和 future 日期之间的天数。
我每秒调用以下命令:

NSDateComponents *components = [[NSDateComponents alloc] init];
[components setYear:2025];
[components setMonth:1];
[components setDay:1];

NSDate *currentDate = [NSDate date];
NSDate *futureDate = [[NSCalendar currentCalendar] dateFromComponents:components];

NSDateComponentsFormatter *formatter = [[NSDateComponentsFormatter alloc] init];
formatter.zeroFormattingBehavior = NSDateComponentsFormatterZeroFormattingBehaviorNone;
formatter.allowedUnits = NSCalendarUnitDay;
formatter.unitsStyle = NSDateComponentsFormatterUnitsStyleAbbreviated;
NSString *remainingDaysAsString = [formatter stringFromDate:currentDate toDate:futureDate];

我每秒打印一次变量 leftDaysAsString 并且它总是每天不同。

3,551d
3,551d
3,550d
3,550d
3,551d
3,550d
3,551d

有没有人经历过类似的事情？这看起来像是类(class)的错误吗？

Answer 1

这很奇怪，看起来像一个错误。 NSDateComponentsFormatter的结果如果您指定，则正确(在我的测试中)
所有单位都小到秒:

formatter.allowedUnits = NSCalendarUnitDay + NSCalendarUnitHour + NSCalendarUnitMinute  + NSCalendarUnitSecond;

获取两个日期之间的天数的一种更简单可靠的方法是

NSDateComponents *comp = [[NSCalendar currentCalendar] components:NSCalendarUnitDay
                                                      fromDate:currentDate
                                                        toDate:futureDate
                                                       options:0];
NSInteger days = comp.day;