How to call a method that's declared in a ViewController from the AppDelegate

Question

Novice question. I'm building an app and I want to call a method that I've declared in a ViewController - from the AppDelegate (on applicationDidBecomeActive).

So basically, In TestAppDelegate.m I have...

  - (void)applicationDidBecomeActive:(UIApplication
 *)application {
     // I want to call a method called "dothisthing" that I've defined in
 FirstViewController.m
     // This does not work:  [FirstViewController dothisthing] }

In FirstViewController.m I have...

- (void) dothisthing {
   NSLog(@"dothisthing");
}

This is my first iPhone app, so any help would be appreciated.

Jaime · Accepted Answer · 2010-07-21 19:52:46Z

3

The method is an instance method so you need to create the instance first and then call the method on the instance... or declare the method as static (+) instead of (-) before the void

FirstViewController* controller = [FirstViewController alloc];

[controller dothisthing]; 

[controller release];

edited Jul 21, 2010 at 19:52

answered Jul 21, 2010 at 16:03

Jaime

6,8142 gold badges29 silver badges43 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

buckminsterfuller Over a year ago

Thanks for the clarification. I'm not sure exactly where I should create the instance first though. In AppDelegate.m? Complete Obj-C novice here.

Jaime Over a year ago

Well, that depends on the lifetime of your controller... if this is the main/only controller in your app, then the appDelegate should 'own' the controller (declare it in the @interface), instantiate it in the applicationDidFinishLoading and release it in the dealloc)

buckminsterfuller Over a year ago

Thanks! I have things working, but one more question... I get a warning: FirstViewController may not respond to '-dothisthing' Here's the code: FirstViewController *controller = [FirstViewController alloc]; [controller dothisthing]; // this throws the warning

Jaime Over a year ago

Whith out looking at the code it may be difficult to say, but you may be missing the declaration of the dothisthing method in the interface (.h) file, or the signature may not match the way you're calling it (ie parameters in the declaration and not calling it with params)

Community · Accepted Answer · 2017-05-23 12:10:46Z

0

you could also create a notification in the FirstViewController, to have that method called when your application becomes active.

There is a similar question where I have posted the code snippets for that option

How to refresh UITableView after app comes becomes active again?

edited May 23, 2017 at 12:10

CommunityBot

11 silver badge

answered Jul 21, 2010 at 16:12

Aaron Saunders

33.4k5 gold badges64 silver badges83 bronze badges

Comments

Community · Accepted Answer · 2017-05-23 10:00:04Z

0

Use this simple NSNotificationCenter example. Works a charm!

edited May 23, 2017 at 10:00

CommunityBot

11 silver badge

answered May 31, 2011 at 9:37

Henrik Erlandsson

3,8355 gold badges46 silver badges67 bronze badges

Collectives™ on Stack Overflow

How to call a method that's declared in a ViewController from the AppDelegate

3 Answers 3

4 Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related