EventKit日历的最后一个事件

Question

I'm making an app in which I sync certain events to a calendar on iPhone.

The problem is, I have no way of telling which events were altered/removed/... So I need to remove all the events between today and the end date of the last event of the calendar before 'syncing' (read inserting) the new events.

As far as I've seen, the only way to do an action on multiple events at once, is by using enumerateEventsMatchingPredicate:usingBlock: and predicateForEventsWithStartDate:endDate:calendars:

But for this I need a specific end date. (and thus, the end date of the last event in my calendar)

I could always save the event identifier of the last event I insert into this calendar, but I would rather not do this: If the user uninstalls my app and installs it again later, I don't have the last event identifier anymore. (given that (s)he didn't remove the calendar manually of course)

I could just remove the calendar every time I need to sync the calendar, but then I would lose all passed events.

Any ideas or tips are much appreciated!

Answer 1

For your comment on :

I can't seem to find any way to fetch all the events of a calendar.

Actually you can fetch all the events from calendar :

NSDate *start = ...
NSDate *finish = ...

// use Dictionary for remove duplicates produced by events covered more one year segment
NSMutableDictionary *eventsDict = [NSMutableDictionary dictionaryWithCapacity:1024];

NSDate* currentStart = [NSDate dateWithTimeInterval:0 sinceDate:start];

int seconds_in_year = 60*60*24*365;

// enumerate events by one year segment because iOS do not support predicate longer than 4 year !
while ([currentStart compare:finish] == NSOrderedAscending) {

    NSDate* currentFinish = [NSDate dateWithTimeInterval:seconds_in_year sinceDate:currentStart];

    if ([currentFinish compare:finish] == NSOrderedDescending) {
        currentFinish = [NSDate dateWithTimeInterval:0 sinceDate:finish];
    }
    NSPredicate *predicate = [eventStore predicateForEventsWithStartDate:currentStart endDate:currentFinish calendars:nil];
    [eventStore enumerateEventsMatchingPredicate:predicate
                                      usingBlock:^(EKEvent *event, BOOL *stop) {

                                          if (event) {
                                              [eventsDict setObject:event forKey:event.eventIdentifier];
                                          }

                                      }];       
    currentStart = [NSDate dateWithTimeInterval:(seconds_in_year + 1) sinceDate:currentStart];

}

NSArray *events = [eventsDict allValues];