Update label in another View Controller from the appDelegate

Question

I would like to update a label in one of my ViewControllers from the appDelegate. The Label in the view controller is all linked up in IB and has properties set.

In the AppDelegate .h

I am creating an ivar for the view controller so I can access the label on the view controller from the delegate like this.

someViewController *myView;

and in the AppDelegate.m file

myView.theLabel.text = @"Whatever";

I've also tried myView.theLabel setText: @"whatever";

Ive also tried making myView a property and synthesising it. I've tried the code in applicationDidFinishLaunching and applicationWillEnterForeground however the label never updates. Whats the best way to do this?

Do you instantiate the controller in your app delegate, or by any other means get a reference to an instance of this controller? — Alladinian, Jun 22 '12 at 19:58
@Alladinian in the .h as mentioned I create a ivar someViewController *myView and access the label this way. The someViewController.h header is added to appDelegate.h and appDelegate.m other than that not sure what you mean. Thanks for replying. — Alex McPherson, Jun 25 '12 at 16:10
@Alladinian sorry me bing thick no I do not instantiate the view controller from the appdelegate should I be doing above the label I am accessing someViewController *myView = [[someViewController alloc]initWithNibName:@"someViewController" blah blah? — Alex McPherson, Jun 25 '12 at 16:14
To set the label in your controller, you'll have to grab a reference of it _after_ you have alloc/init/present it. Where and how is your view controller added to the window? — Alladinian, Jun 25 '12 at 16:16

Highrule · Answer 1 · 2012-06-29T15:14:56.733

I would imagine that myView hasn't been created yet, so you have a null reference.

Try this to test that theory:

someViewController *myView;
if(myView)
    NSLog(@"Object has been created");
else
    NSLog(@"You have a null reference - The Object hasn't been created yet");

If this is the case, change the line to this to create it:

someViewController *myView = [[someViewController alloc] initWithNibName:@"SomeViewController" bundle:nil];
myView.theLabel.text = @"Something";
self.window.rootViewController = myView;

Yes, you create your first view in appDelegate, then set the rootViewController to that first view.

Update label in another View Controller from the appDelegate

1 Answers1