Programmatically create iCal event, and test for event existence

Question

An example of how to programmatically create an iCAL event in the default calendar, using Objective-C. The code checks if the event already exists, and sets the button state accordingly. I hope this example is useful.

-(void)initCalendar {

 // An array of 1 dictionary object, containing START and END values.
 NSMutableArray* pvDict  = [[NSMutableArray alloc] initWithContentsOfURL:[NSURL URLWithString:PV_URL ]];

 // Check if the private view event already exists in the default calendar.
 // Then set the calendar button state.

 // Get a entry point to the Calendar database.
 self.store = [[EKEventStore alloc ] init ];

 // Get an array of all the calendars.
 NSArray *calendars = store.calendars;

 // Get the default calendar, set by the user in preferences.
 EKCalendar *defaultCal = store.defaultCalendarForNewEvents;

 // Find out if this calendar is modifiable.
  BOOL isDefaultCalModifiable = defaultCal.allowsContentModifications ;

 // Create an event in the default calendar.

  self.event = [ EKEvent eventWithEventStore:store ];

 self.event.title = CHELSEA_SPACE ;
 self.event.location = CHELSEA_ADDRESS ;

 NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
 [dateFormatter setDateFormat:@"yyy-MM-dd HH:mm:ss.S"];

 NSString *startString = [[ pvDict objectAtIndex:0] objectForKey:@"starts" ];
 NSDate *dateStart = [dateFormatter dateFromString:startString];

 NSString *endString = [[ pvDict objectAtIndex:0] objectForKey:@"ends" ];
 NSDate *dateEnd = [dateFormatter dateFromString:endString];

    self.event.startDate = dateStart;
 self.event.endDate   = dateEnd; 

 self.event.calendar = defaultCal ;

 // Alternative code to add 2.5 hours to start time.
 // [[NSDate alloc] initWithTimeInterval:9000 sinceDate:event.startDate];

 // Search for events which match this date/time start and end.
 // Compare the matched events by event TITLE.

 NSPredicate *predicate = [store predicateForEventsWithStartDate:event.startDate 
           endDate:event.endDate calendars:calendars];

 NSArray *matchingEvents = [store eventsMatchingPredicate:predicate];

 self.calendarButton.enabled = NO;

 if( ! isDefaultCalModifiable ) {
  // The default calendar is not modifiable
  return ;
 } 

 if ( [ matchingEvents count ] > 0 ) {

  // There are already event(s) which match this date/time start and end.
   // Check if this event is the PV

  EKEvent *anEvent;  
  int j;

  for ( j=0; j < [ matchingEvents count]; j++) {

   anEvent = [ matchingEvents objectAtIndex:j ] ;
   if([ CHELSEA_SPACE isEqualToString: anEvent.title ]) {
    // PV event already exists in calendar.
    return;
   }
  }
  [ anEvent release ];
 }

 self.calendarButton.enabled = YES;

 [ pvDict release ];
}

-(void)addEventToCalendar:(id)sender {

 NSError *error;
 BOOL saved = [self.store saveEvent:self.event span:EKSpanThisEvent error:&error]; 

 NSLog(@"Saved calendar event = %@\n", (saved ? @"YES" : @"NO"));
 self.calendarButton.enabled = NO;

}