iOS - Changing tabbar badge from other class - ios

Question

I've searched a lot but could not find an answer and therefore decided to ask you :).
I have an application with some views. After logging in I create a UITabBarController with 3 tabs.
Now I wish to change the second tab's badge based on how many notifications the user has.
This core works when called in the viewdidload method:
NSString *badgeValue = [NSString stringWithFormat:#"%i", [cacheNotifications count]];
if([cacheNotifications count] != 0){
[[[[[self tabBarController] viewControllers] objectAtIndex: 1] tabBarItem] setBadgeValue:badgeValue];
}
However, I have a daemon running in the background that checks for notifications every 30 seconds. It would be great if I could change the badge from this daemon.
When I call something like this:
PlatformViewController *theInstance = [[PlatformViewController alloc] init];
[theInstance updateNotificationsBadge];
It does call the function but does not update the badge. With or without the performSelectorOnMainThread.
updateNotificationsBadge:
-(void) updateNotificationsBadge{
NSString *badgeValue = [NSString stringWithFormat:#"%i", [cacheNotifications count]];
NSLog(#"Length here is: %i", [cacheNotifications count]);
if([cacheNotifications count] > 0){
NSLog(#"call..");
[self performSelectorOnMainThread:#selector(setNotification:)
withObject:badgeValue
waitUntilDone:YES];
}
}
-(void)setNotification:(NSString*)badge{
NSLog(#"Called. %#", badge);
[[[[[self tabBarController] viewControllers] objectAtIndex: 1] tabBarItem] setBadgeValue:badge];
}
How could I fix this?
Thanks in advance!
EDIT:
cacheNotifications is a global variable declared in globalVars.m. It does not get reinitialized when I call a new instance.
I call the code below from daemonClass.m
PlatformViewController *theInstance = [[PlatformViewController alloc] init];
[theInstance updateNotificationsBadge];

Answer 1

Instead of creating a new instance for platformViewController, you need to use existing reference. When you create a new one, cacheNotification array would not be initialized and no contents in it. So it will always returns 0.
and UITabBarController is a containerViewController contains all the viewControllers. So you don't need to change the tab badgeValue from the other class. You can simply change it from any class.
and in your setNotification: method, change the badgeValue like this.
[[[[self tabBarController] tabBar] items] objectAtIndex:1] setBadgeValue:badge];

Answer 2

You should use the same instance of class rather creating the new one. Which destroy the previous value. I would recommend please use NSNotificationCenter to post notification when you get a badge which will implement void getter and setter method of badge in platformViewControllerclass. then no instance would be destroy.
Hope this helps

Answer 3

I really don't know exactly your problem, but what I think I would use a subclass of nsobject and in each viewController I'd change the badge. Something similar to this: https://stackoverflow.com/a/9736559/2000162

Answer 4

func setBadge(){
let viewconrollers = self.tabBarController?.viewControllers
viewconrollers![3].tabBarItem.badgeValue = "Your String value"
viewconrollers![3].tabBarItem.badgeColor = UIColor.green
}
//call setBadge() method from view controller's viewdidload method.
// select your give number it the view controllers array for providing badge on the desired tab