iOS - Calling App Delegate method from ViewController

Question

What I am trying to do is click a button (that was created in code) and have it call up a different view controller then have it run a function in the new view controller.

I know it could be done relatively easily in IB but that isn't an option.

An example of what I want to do would be if you had two view controllers one with a splash screen of house. The other view controller had a walk through of the house on it that you could go through all the rooms in a set order. The splash screen would have buttons for each room that would allow you to jump to any point on the walk through.

Cristian Radu · Accepted Answer · 2011-02-22 19:29:26Z

541

You can access the delegate like this:

MainClass *appDelegate = (MainClass *)[[UIApplication sharedApplication] delegate];

Replace MainClass with the name of your application class.

Then, provided you have a property for the other view controller, you can call something like:

[appDelegate.viewController someMethod];

answered Feb 22, 2011 at 19:29

Cristian Radu

8,4122 gold badges21 silver badges11 bronze badges

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

4 Comments

Zaky German Over a year ago

might also need to import the appDelegate.h file wherever it is used, or do @class appDelegate

mharper Over a year ago

appDelegate.h file is a good candidate to go in the target's prefix/precompiled header file IMO.

Kenny Lövrin Over a year ago

If you import your app delegate in your Prefix.pch like @mharper says you can also add this at the same time: #define AppDelegate ((MyAppDelegateClass *)[UIApplication sharedApplication].delegate) which then allows you to access your app delegate like '[AppDelegate.viewController someMethod]'. It simplifies it a bit, but it also makes it easier to abuse it.

harveyslash Over a year ago

after the @end of my app delegate.h file , I added #define AppDelegate ((MyAppDelegateClass *)[UIApplication sharedApplication].delegate) Now whichever class imports app delegate can directly use [AppDelegate.viewController someMethod]

canhazbits · Accepted Answer · 2016-08-12 17:13:16Z

45

And if anyone is wondering how to do this in swift:

if let myDelegate = UIApplication.sharedApplication().delegate as? AppDelegate {
   myDelegate.someMethod()
}

edited Aug 12, 2016 at 17:13

answered Oct 17, 2014 at 3:59

canhazbits

1,7251 gold badge14 silver badges19 bronze badges

3 Comments

cbartel Over a year ago

if let appDelegate = UIApplication.sharedApplication().delegate as? AppDelegate {} is a better approach in swift.

mfaani Over a year ago

@petrsyn What do you mean the delegate can be nil? Isn't that an app ALWAYS has an AppDelegate?!

sfarbota Over a year ago

In recent versions of Swift, sharedApplication() should be replace with shared. i.e., remove "Application" and the parentheses. So the full working code as of Swift 5.2 would be: if let myDelegate = UIApplication.shared.delegate as? AppDelegate { myDelegate.someMethod() }

pablasso · Accepted Answer · 2012-03-09 04:56:26Z

41

Sounds like you just need a UINavigationController setup?

You can get the AppDelegate anywhere in the program via

YourAppDelegateName* blah = (YourAppDelegateName*)[[UIApplication sharedApplication]delegate];

In your app delegate you should have your navigation controller setup, either via IB or in code.

In code, assuming you've created your 'House overview' viewcontroller already it would be something like this in your AppDelegate didFinishLaunchingWithOptions...

self.m_window = [[[UIWindow alloc]initWithFrame:[[UIScreen mainScreen]bounds] autorelease];
self.m_navigationController = [[[UINavigationController alloc]initWithRootViewController:homeViewController]autorelease];
[m_window addSubview:self.m_navigationController.view];

After this you just need a viewcontroller per 'room' and invoke the following when a button click event is picked up...

YourAppDelegateName* blah = (YourAppDelegateName*)[[UIApplication sharedApplication]delegate];
[blah.m_navigationController pushViewController:newRoomViewController animated:YES];

I've not tested the above code so forgive any syntax errors but hope the pseudo code is of help...

edited Mar 9, 2012 at 4:56

pablasso

2,4992 gold badges26 silver badges32 bronze badges

answered Feb 22, 2011 at 19:33

sradforth

2,1862 gold badges23 silver badges39 bronze badges

1 Comment

Mytheral Over a year ago

Your answer is correct as well, I ended up using a combination of Cristian's and your answer. I wish I could split the check mark.

mikemike396 · Accepted Answer · 2013-07-08 17:44:04Z

18

This is how I do it.

[[[UIApplication sharedApplication] delegate] performSelector:@selector(nameofMethod)];

Dont forget to import.

#import "AppDelegate.h"

answered Jul 8, 2013 at 17:44

mikemike396

2,5151 gold badge28 silver badges44 bronze badges

Comments

Tunvir Rahman Tusher · Accepted Answer · 2016-11-18 07:26:46Z

13

Just Follow these steps

1.import your app delegate in your class where you want app delegate object.

#import "YourAppDelegate.h"

2.inside your class create an instance of your app delegate object(Its basically a singleton).

YourAppDelegate *appDelegate=( YourAppDelegate* )[UIApplication sharedApplication].delegate;

3.Now invoke method using selector

if([appDelegate respondsToSelector:@selector(yourMethod)]){

        [appDelegate yourMethod];
    }

or directly by

[appDelegate yourMethod];

for swift

let appdel : AppDelegate = UIApplication.shared.delegate as! AppDelegate

i will recommend the first one. Run and Go.

edited Nov 18, 2016 at 7:26

answered Jul 19, 2014 at 15:46

Tunvir Rahman Tusher

6,7102 gold badges39 silver badges33 bronze badges

1 Comment

Ammo Goettsch Over a year ago

this is specifically NOT a new instance of the delegate, but rather retrieves the singleton delegate of the singleton application

bruno.yvan.morel · Accepted Answer · 2012-02-05 21:36:39Z

11

NSObject <UIApplicationDelegate> * universalAppDelegate = 
    ( NSObject <UIApplicationDelegate> * ) [ [ UIApplication sharedApplication ] delegate ];

It avoid having to include your AppDelegate.h everywhere. It's a simple cast that goes a long way, allowing to develop independent Controller and reuse them elsewhere without to worry about class name and so on...

Enjoy

answered Feb 5, 2012 at 21:36

bruno.yvan.morel

1111 silver badge3 bronze badges

1 Comment

MGY Over a year ago

Thank you for sharing, it makes me happy for a couple of minutes, probobly it'll work some way, but what if I want to use a method like visibleViewController from it? It'll give error like this: Property 'visibleViewController' not found on object of type 'NSObject<UIApplicationDelegate> *. any solution for this?

ZaEeM ZaFaR · Accepted Answer · 2014-12-10 10:27:05Z

8

A lot of good answers are already added. Though I want to add something which suits me most of the time.

#define kAppDelegate ((YourAppDelegate *)[[UIApplication sharedApplication] delegate]);

and thats it. Use it throughout the application just like a constant.

e.g.

[kAppDelegate methodName];

Don't forget to import yourAppDelegate.h in corresponding .pch or macros file.

answered Dec 10, 2014 at 10:27

ZaEeM ZaFaR

1,53617 silver badges23 bronze badges

Comments

Daniele D. · Accepted Answer · 2016-09-15 19:51:16Z

7

If someone need the same in Xamarin (Xamarin.ios / Monotouch), this worked for me:

var myDelegate = UIApplication.SharedApplication.Delegate as AppDelegate;

(Require using UIKit;)

edited Sep 15, 2016 at 19:51

answered Jul 22, 2015 at 13:33

Daniele D.

2,7443 gold badges38 silver badges42 bronze badges

1 Comment

Phil Over a year ago

The correct statement in Swift is let appdel : AppDelegate = UIApplication.shared.delegate as! AppDelegate

iAj · Accepted Answer · 2017-11-05 05:01:49Z

6

Update for Swift 3.0 and higher

//
// Step 1:- Create a method in AppDelegate.swift
//
func someMethodInAppDelegate() {

    print("someMethodInAppDelegate called")
}

calling above method from your controller by followings

//
// Step 2:- Getting a reference to the AppDelegate & calling the require method...
//
if let appDelegate = UIApplication.shared.delegate as? AppDelegate {

    appDelegate.someMethodInAppDelegate()
}

Output:

answered Nov 5, 2017 at 5:01

iAj

3,8171 gold badge34 silver badges34 bronze badges

Comments

Marco Miltenburg · Accepted Answer · 2015-09-03 20:56:12Z

5

And in case you need access to your WatchKit extension delegate from a view controller on watchOS:

extDelegate = WKExtension.sharedExtension().delegate as WKExtensionDelegate?

answered Sep 3, 2015 at 20:56

Marco Miltenburg

6,1381 gold badge33 silver badges30 bronze badges

Comments

Pratik Shah · Accepted Answer · 2016-03-10 13:56:09Z

3

You can add #define uAppDelegate (AppDelegate *)[[UIApplication sharedApplication] delegate] in your project's Prefix.pch file and then call any method of your AppDelegate in any UIViewController with the below code.

[uAppDelegate showLoginView];

edited Mar 10, 2016 at 13:56

Pratik Shah

5634 silver badges14 bronze badges

answered Jul 8, 2015 at 11:18

Ada

4729 silver badges13 bronze badges

Comments

Breno Medeiros de Oliveira · Accepted Answer · 2020-02-03 16:07:34Z

1

In 2020, iOS13, xCode 11.3. What is working for Objective-C is:

#import "AppDelegate.h"

AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];

It's working for me, i hope the same to you! :D

answered Feb 3, 2020 at 16:07

Breno Medeiros de Oliveira

98410 silver badges12 bronze badges

Comments

ingconti · Accepted Answer · 2018-02-06 09:57:45Z

0

Even if technically feasible, is NOT a good approach. When You say: "The splash screen would have buttons for each room that would allow you to jump to any point on the walk through." So you want to pass through appdelegate to call these controllers via tohc events on buttons?

This approach does not follow Apple guidelines and has a lot of drawbacks.

answered Feb 6, 2018 at 9:57

ingconti

11.8k3 gold badges68 silver badges52 bronze badges

2 Comments

Mytheral Over a year ago

Look at the date on the question... It's from back when Interface Builder was a separate application and development was a very different beast. I haven't touched iOS development in years so I can't evaluate more modern answers.

ingconti Over a year ago

it ca be.. but my considerations are still valid

Collectives™ on Stack Overflow

iOS - Calling App Delegate method from ViewController

13 Answers 13

4 Comments

3 Comments

1 Comment

Comments

1 Comment

1 Comment

Comments

1 Comment

Comments

Comments

Comments

Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

13 Answers 13

4 Comments

3 Comments

1 Comment

Comments

1 Comment

1 Comment

Comments

1 Comment

Comments

Comments

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related