iOS - Calling App Delegate method from ViewController

Question

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];

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

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

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...

This is how I do it.

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

Dont forget to import.

#import "AppDelegate.h"

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.

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

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.