objective-c : basic Scheduling the local notifications

snippet.m

//basic Scheduling the local notifications

//ChecklistItem.h

//principles of Object-Oriented Programming is that objects can do as much as possible themselves
//therefore, it makes sense that the ChecklistItem object can schedule its own notifications.
- (void)scheduleNotification;

//ChecklistItem.m

#pragma mark - schedule notifications

//ChecklistItem object can schedule its own notifications
- (void)scheduleNotification {
    
    if (debug==1) {NSLog(@"Running %@ '%@'", self.class, NSStringFromSelector(_cmd));}
    
    //if there is a existing notification
       UILocalNotification *existingNotification = [self notificationForThisItem];
       
       if (existingNotification != nil) {
           NSLog(@"Found an existing notification %@", existingNotification);
           [[UIApplication sharedApplication] cancelLocalNotification:existingNotification];
       }

    //compares due date with current date
    //if due date is in the past, then the NSLog() will not be performed
    //call this method when the user presses the Done button after adding or editing a to-do item
    if (self.shouldRemind && [self.dueDate compare:[NSDate date]] != NSOrderedAscending) {
        
        NSLog(@"We should schedule a notification");
        
        UILocalNotification *localNotification = [[UILocalNotification alloc] init];
        
        localNotification.fireDate = self.dueDate;
        localNotification.timeZone = [NSTimeZone defaultTimeZone];
        localNotification.alertBody = self.text;
        localNotification.soundName = UILocalNotificationDefaultSoundName;
        localNotification.userInfo = @{ @"ItemID" : @(self.itemId) };
        
        [[UIApplication sharedApplication] scheduleLocalNotification:localNotification];
        
        NSLog(@"Scheduled notification %@ for itemId %d", localNotification, self.itemId);
    }
}


#pragma mark - check whether there is a existing notification

- (UILocalNotification *)notificationForThisItem {
    
    NSArray *allNotifications = [[UIApplication sharedApplication] scheduledLocalNotifications];

    for (UILocalNotification *notification in allNotifications) {
        NSNumber *number = [notification.userInfo objectForKey:@"ItemID"];
    
        if (number != nil && [number integerValue] == self.itemId) {
            return notification;
        }
    }
    return nil;
}


//ItemDetailViewController.m
//call scheduleNotification method when the user presses the Done button after adding or editing a to-do item
- (IBAction)done
{
    if (debug==1) {NSLog(@"Running %@ '%@'", self.class, NSStringFromSelector(_cmd));}
        
    [item scheduleNotification]; //ChecklistItem object can schedule its own notifications
}