NSCFCalendar dateFromComponents：组件不能为零

Question

执行以下代码后

NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *expiryDateComponents = [calendar components:(NSCalendarUnitEra|NSCalendarUnitYear|NSCalendarUnitMonth|NSCalendarUnitDay) fromDate:aDate];

你得到以下非崩溃异常

*** -[__NSCFCalendar dateFromComponents:]: components cannot be nil
Future exception.
A few of these errors are going to be reported with this complaint, then further violations will simply be ignored.

Answer 1

tl; dr 确保fromDate参数不是。

解释：

当你给它一个零NSCalendar时，

NSDate不知道如何处理这种情况。 API会向您发出警告，而不是抛出崩溃异常。请注意，由于API更改，此行为可能会发生变化并可能导致将来崩溃。