NSCalendar为所有值返回nil和0？

Question

NSCalendar *cal = [[NSCalendar alloc] init];
NSDateComponents *tcomponents = [cal components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear|NSCalendarUnitMinute|NSCalendarUnitHour fromDate:[NSDate date]];

NSLog(@"-%@",cal); //gets null
NSLog(@"-%@",tcomponents); //gets null

它有什么不对吗？

Answer 1

您的日历不存在

指定的初始化程序是

- (id)initWithCalendarIdentifier:(NSString *)string

带

NSString * const NSGregorianCalendar;
NSString * const NSBuddhistCalendar;
NSString * const NSChineseCalendar;
NSString * const NSHebrewCalendar;
NSString * const NSIslamicCalendar;
NSString * const NSIslamicCivilCalendar;
NSString * const NSJapaneseCalendar;
NSString * const NSRepublicOfChinaCalendar;
NSString * const NSPersianCalendar;
NSString * const NSIndianCalendar;
NSString * const NSISO8601Calendar;

是有效的标识符。

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或只是

NSCalendar *cal = [NSCalendar currentCalendar];