objective-c – XCode：为什么我的活动没有被添加到日历中？

NSDate * selected = [DatePicker date];
NSString * date = [selected description];

NSDateComponents *components = [[NSCalendar currentCalendar] components:NSDayCalendarUnit 
                                                              fromDate:DatePicker.date];

CalLabel1.text = [NSString stringWithFormat:@"%d",[components day]];

EKEventStore *store = [[EKEventStore alloc] init];

EKEvent *event = [EKEvent eventWithEventStore:store];
event.title = @"Test Event";
//required
event.startDate = [DatePicker date];
event.endDate = [DatePicker date];
event.calendar = store.defaultCalendarForNewEvents;
//end

NSError *err;
[store saveEvent:event span:EKSpanThisEvent error:&err];

为什么这不会在iOS日历中添加任何内容？

谢谢.