Difference between presentLocalNotificationNow and scheduleLocalNotification

Question

What is the difference between presentLocalNotificationNow and scheduleLocalNotification.

For the both following function is showing notification after 1 second

-(void)showLocalNotification:(NSNotification *)notification {

    NSString *msg = @"test message";

    [[UIApplication sharedApplication] cancelAllLocalNotifications];

    UILocalNotification *_localNotification = [[UILocalNotification alloc]init];

    _localNotification.fireDate = [NSDate dateWithTimeIntervalSinceNow:1];

    _localNotification.timeZone = [NSTimeZone defaultTimeZone];

    _localNotification.alertBody = msg;

    _localNotification.soundName = UILocalNotificationDefaultSoundName;

    _localNotification.applicationIconBadgeNumber = [[UIApplication sharedApplication] applicationIconBadgeNumber]+1;

    [[UIApplication sharedApplication] scheduleLocalNotification:_localNotification];

    // or 

    //[[UIApplication sharedApplication] presentLocalNotificationNow:_localNotification];
}

Answer 1

If the application is running in the background, the local notification will not get an alert or sound, as it is directly received by the application. In that case, you need to present the notification using presentLocalNotificationNow.

- (void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification
{
    UIApplicationState applicationState = application.applicationState;
    if (applicationState == UIApplicationStateBackground) {
        [application presentLocalNotificationNow:notification];
    }
}

From Apple Documentation:

Once you have created an instance of UILocalNotification, you schedule it using one of two methods of the UIApplication class: scheduleLocalNotification: or presentLocalNotificationNow:. The former method use the fire date to schedule delivery; the latter method presents the notification immediately, regardless of the value of fireDate. You can cancel specific or all local notifications by calling cancelLocalNotification: or cancelAllLocalNotifications, respectively.