Question

I am developing an iPhone alarm app based on local notifications.

On deleting an alarm, the related local notification should get cancelled. But how can I determine exactly which object from the array of local notifications is to be cancelled?

I am aware of [[UIApplication sharedApplication] cancelLocalNotification:notification] method but how can I get this ‘notification’ to cancel it?

Answer 1

You can save a unique value for key in your local notification’s userinfo.
Get all local notification, loop through the array and delete the particular notification.

Code as follows,

OBJ-C:

UIApplication *app = [UIApplication sharedApplication];
NSArray *eventArray = [app scheduledLocalNotifications];
for (int i=0; i<[eventArray count]; i++)
{
    UILocalNotification* oneEvent = [eventArray objectAtIndex:i];
    NSDictionary *userInfoCurrent = oneEvent.userInfo;
    NSString *uid=[NSString stringWithFormat:@"%@",[userInfoCurrent valueForKey:@"uid"]];
    if ([uid isEqualToString:uidtodelete])
    {
        //Cancelling local notification
        [app cancelLocalNotification:oneEvent];
        break;
    }
}

SWIFT:

var app:UIApplication = UIApplication.sharedApplication()
for oneEvent in app.scheduledLocalNotifications {
    var notification = oneEvent as UILocalNotification
    let userInfoCurrent = notification.userInfo! as [String:AnyObject]
    let uid = userInfoCurrent["uid"]! as String
    if uid == uidtodelete {
        //Cancelling local notification
        app.cancelLocalNotification(notification)
        break;
    }
}

UserNotification:

If you use UserNotification (iOS 10+), just follow this steps:

1. When creating the UserNotification content, add an unique identifier

2. Remove specific pending notification using removePendingNotificationRequests(withIdentifiers:)

3. Remove specific delivered notification using removeDeliveredNotifications(withIdentifiers:)

For more info, UNUserNotificationCenter