ViewController sample code for EventKit

ViewController.m

//
//  ViewController.m
//  eventFiddler
//
//  Created by Sean Roberts on 5/17/17.
//  Copyright © 2017 Red Shed Technology. All rights reserved.
//

#import "ViewController.h"
@import EventKit;
@interface ViewController ()
@property (strong, nonatomic) EKEventStore *eventStore;
// Indicates whether app has access to event store.
@property (nonatomic) BOOL isAccessToEventStoreGranted;
// The data source for the table view
@property (strong, nonatomic) NSMutableArray *todoItems;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self updateAuthorizationStatusToAccessEventStore];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (EKEventStore *)eventStore {
    if (!_eventStore) {
        _eventStore = [[EKEventStore alloc] init];
    }
    return _eventStore;
}

- (void)updateAuthorizationStatusToAccessEventStore {
    // 2
    EKAuthorizationStatus authorizationStatus = [EKEventStore authorizationStatusForEntityType:EKEntityTypeReminder];
    
    switch (authorizationStatus) {
            // 3
        case EKAuthorizationStatusDenied:
        case EKAuthorizationStatusRestricted: {
            self.isAccessToEventStoreGranted = NO;
            UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Access Denied"
                                                                message:@"This app doesn't have access to your Reminders." delegate:nil
                                                      cancelButtonTitle:@"Dismiss" otherButtonTitles:nil];
            [alertView show];

            break;
        }
            
            // 4
        case EKAuthorizationStatusAuthorized:
            self.isAccessToEventStoreGranted = YES;

            break;
            
            // 5
        case EKAuthorizationStatusNotDetermined: {
            __weak ViewController *weakSelf = self;
            [self.eventStore requestAccessToEntityType:EKEntityTypeReminder
                                            completion:^(BOOL granted, NSError *error) {
                                                dispatch_async(dispatch_get_main_queue(), ^{
                                                    weakSelf.isAccessToEventStoreGranted = granted;
                                                    //[weakSelf.tableView reloadData];
                                                });
                                            }];
            break;
        }
    }
}

@end