if ([[UIApplication sharedApplication] currentUserNotificationSettings].types != UIUserNotificationTypeNone)
{
    NSLog(@" Push Notification ON");
}
else
{
    UIAlertController *alertController = [UIAlertController  alertControllerWithTitle:@"Push Notification Service Disable ,please enable it."  message:nil  preferredStyle:UIAlertControllerStyleAlert];
    [alertController addAction:[UIAlertAction actionWithTitle:@"Okay!" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action)
    {
           @try
           {
                NSLog(@"tapped ok");
                BOOL canOpenSettings = (UIApplicationOpenSettingsURLString != NULL);
                if (canOpenSettings)
                {
                     NSURL *url = [NSURL URLWithString:UIApplicationOpenSettingsURLString];
                     [[UIApplication sharedApplication] openURL:url];
                }
           }
           @catch (NSException *exception)
          {

          }
    }]];
   [self.view presentViewController:alertController animated:YES completion:^{}];
}