NSTimer in AppDelegate does not update UILabel in UIViewController - objective-c

Question

My goal is to start a timer in the app delegate and use it to call methods in other view controllers. When these methods are called they will update the text of the UILabel. I'm performing the method on the main thread but I can't figure out why the UILabel is not being updated. I know the method in the view controller is being called but the UILabel doesn't get updated. I also verified the IBOutlet connection in Interface Builder. I am using storyboard to lay out my views and attach the view controllers to those views. What am I doing wrong?
In my AppDelegate.m:
#import "AppDelegate.h"
#import "GreyViewController.h"
#interface AppDelegate ()
#property (nonatomic) int counter;
#property (strong, nonatomic) GreyViewController *greyClass;
#end
#implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
NSTimer *timer;
timer = [NSTimer scheduledTimerWithTimeInterval:2.0
target:self
selector:#selector(performOnMain)
userInfo:nil
repeats:YES];
return YES;
}
- (GreyViewController *)greyClass {
if (!_greyClass) {
_greyClass = [[GreyViewController alloc] init];
}
return _greyClass;
}
- (void)performOnMain {
[self performSelectorOnMainThread:#selector(updateLabel) withObject:nil waitUntilDone:YES];
}
- (void)updateLabel {
self.counter++;
NSLog(#"appdelegate counter %i", self.counter);
[self.greyClass updateGreyLabel:[NSString stringWithFormat:#"%i", self.counter]];
}
#end
The GreyViewController.h is:
#import <UIKit/UIKit.h>
#interface GreyViewController : UIViewController
#property (strong, nonatomic) NSString *greyString;
#property (weak, nonatomic) IBOutlet UILabel *greyLabel;
- (void)updateGreyLabel:(NSString *)string;
#end
The method in my GreyViewController.m:
- (void)updateGreyLabel:(NSString *)string {
self.greyLabel.text = string;
NSLog(#"greyviewcontroller string %#", string);
}

Answer 1

Every time you call:
GreyViewController *greyClass = [[GreyViewController alloc] init];
in your "updateLabel" method (i.e. every two seconds) you're instantiating a new GreyViewController. It's very likely you do not want to do that.
Instead, instantiate/create it once (or create it in your storyboard or XIB file) and the update the label which is connected to an outlet.