Check if Event exists on Calendar - ios

Question

I'm having trouble verifying if an event already exists on the user's calendar. I need to check this to determine if I should add it or not, so that I don't create duplicate calendar entries. Right now, I create a duplicate entry every time I run the code.
First, here is how I am creating the calendar entry:
+ (NSString *) addEventToCalenderWithDate : (NSDate *) eventDate
eventTitle : (NSString *) eventTitle
eventLocation : (NSString *) eventLocation
allDayEvent : (BOOL) isAllDay
{
EKEventStore *store = [[EKEventStore alloc] init];
[store requestAccessToEntityType:EKEntityTypeEvent completion:^(BOOL granted, NSError *error) {
if (!granted) {
returnValue = #"calendar error";
}
else if ([self eventExists:dateAndTime eventTitle:eventTitle allDayEvent:isAllDay]) {
returnValue = #"duplicate";
}
else {
EKEvent *event = [EKEvent eventWithEventStore:store];
event.title = eventTitle;
event.startDate = dateAndTime;
if (eventTimeString == (id)[NSNull null] || eventTimeString.length == 0 || isAllDay) {
event.allDay = YES;
event.endDate = dateAndTime;
} else {
event.endDate = [event.startDate dateByAddingTimeInterval:60*60]; //set 1 hour meeting
}
event.location = eventLocation;
[event setCalendar:[store defaultCalendarForNewEvents]];
NSError *err = nil;
[store saveEvent:event span:EKSpanThisEvent commit:YES error:&err];
returnValue = #"success";
}
}];
return returnValue;
}
This sets the event correctly. However, if I run it again, I expect that the else if clause will return YES and no new entry will be created. However, it always returns NO and I create a new calendar entry with each execution. Here is that method:
+ (BOOL) eventExists : (NSDate *) date
eventTitle : (NSString *) eventTitle
allDayEvent : (BOOL) isAllDay
{
EKEventStore *store = [[EKEventStore alloc] init];
NSPredicate *predicateForEventOnDate = [[NSPredicate alloc] init];
if (isAllDay)
predicateForEventOnDate = [store predicateForEventsWithStartDate:date endDate:date calendars:nil]; // nil will search through all calendars
else
predicateForEventOnDate = [store predicateForEventsWithStartDate:date endDate:[date dateByAddingTimeInterval:60*60] calendars:nil]; // nil will search through all calendars
NSArray *eventOnDate = [store eventsMatchingPredicate:predicateForEventOnDate];
NSLog(#"eventOnDate: %#", eventOnDate);
BOOL eventExists = NO;
for (EKEvent *eventToCheck in eventOnDate) {
if ([eventToCheck.title isEqualToString:eventTitle]) {
eventExists = YES;
}
}
return eventExists;
}
As I step through this method, I notice that the NSArray called eventOnDate is nil (the EKEventStore is not nil). I don't know if this means that it simply did not find any matching events or if something else is going on.
What am I doing wrong that won't allow this to identify existing events on the calendar? Thank you!

Answer 1

The problem appears to be with the date range you have selected for your predicate.
predicateForEventOnDate = [store predicateForEventsWithStartDate:date endDate:date calendars:nil];
This will look for events within a "0" second range because the start and end date of your predicate query is identical.
predicateForEventOnDate = [store predicateForEventsWithStartDate:date endDate:[date dateByAddingTimeInterval:60*60] calendars:nil];
This will only look for events that lie within an hour of the date provided.
NSCalendar *const calendar = NSCalendar.currentCalendar;
NSCalendarUnit const preservedComponents = (NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay);
//strip away hours, minutes and seconds to find date - at start of day
NSDateComponents *startComponents = [calendar components:preservedComponents fromDate:self.date];
//set finished date to 1 full day later
NSDateComponents *offset = [[NSDateComponents alloc] init];
[offset setDay:1];
NSDate *start = [calendar dateFromComponents:startComponents];
NSDate *finish = [calendar dateByAddingComponents:offset toDate:self.date options:0];
NSPredicate *predicateForEventOnDate = [[NSPredicate alloc] init];
if (isAllDay)
predicateForEventOnDate = [store predicateForEventsWithStartDate:start endDate:finish calendars:nil];
NSArray *eventOnDate = [store eventsMatchingPredicate:predicateForEventOnDate];
This will produce an array that covers events for the full day from start to finish.