How to subclass UIApplication?

Question

The iPhone Reference Libary - UIApplication says I can subclass UIApplication, but if I try this I will get an exception:

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'There can only be one UIApplication instance.'

This reminds me of the Highlander "There can be only one,. :-)

Do I have to pass other argurments to UIApplicationMain? Or did I missread somthing in the libary?

http://stackoverflow.com/questions/26213279/objective-c-project-with-swift-uiapplication-subclass-error-class-not-loaded — Gangadhar, May 05 '15 at 22:41

Teemu Kurppa · Accepted Answer · 2014-04-03T14:31:07.040

27

Did you pass the name of your subclass to UIApplicationMain? Let's assume you have

@interface MyUIApp : UIApplication 
...

then in main() you should do:

NSString* appClass = @"MyUIApp";
NSString* delegateClass = nil;
int retVal = UIApplicationMain(argc, argv, appClass, delegateClass);

edited Apr 03 '14 at 14:31

answered Sep 09 '09 at 12:06

Teemu Kurppa

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Hi, I have tried the same way as suggested in answer... but i'm still getting the same error... Anything else i need to do...? – Mihir Mehta Jun 24 '10 at 05:57
How can i retrive this "MyUIApp" class's object ? – Mangesh Jan 07 '13 at 11:23
MyUIApp* app = [UIApplication sharedApplication]; – Teemu Kurppa Jan 08 '13 at 12:25
@TeemuKurppa What is for swift 4 or later ? – Jamshed Alam Oct 10 '19 at 06:12
@JamshedAlam the same but in Swift syntax. https://developer.apple.com/documentation/uikit/1622933-uiapplicationmain – Teemu Kurppa Oct 13 '19 at 08:13

score 12 · Answer 2 · answered Sep 09 '09 at 12:05

12

In your app's info.plist, make sure you change the NSPrincipalClass key to the name of your subclass. This'll make Cocoa instantiate the correct class when the applications loads - you shouldn't have to do anything other than that to get your subclass working.

answered Sep 09 '09 at 12:05

iKenndac

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There is no NSPrincipalClass key in my info.plist. Should i add it? – masche Sep 09 '09 at 13:03
Yes - there are many, many keys that could be in your Info.plist - they aren't all included by default. – iKenndac Sep 09 '09 at 13:47
3

This seems Mac OS X only, not for iPhone OS: http://developer.apple.com/iphone/library/documentation/General/Reference/InfoPlistKeyReference/Articles/CocoaKeys.html#//apple_ref/doc/uid/TP40009251-SW1 – eonil Jun 05 '10 at 19:10
Works on tvOS (and I am certain also on iOS) and should be the accepted answer. – Gerd K Oct 11 '18 at 19:56

score 1 · Answer 3 · answered Nov 18 '14 at 09:18

I know this is an old one and accepted answer is o.k., but to make it clear...

Let's say you have:

UIApplication subclassed as MyApplication

UIApplicationDelegate subclassed as MyAppDelegate

Then your main.m would look like:

#import <UIKit/UIKit.h>

#import "MyApplication.h"
#import "MyAppDelegate.h"

int main(int argc, char * argv[])
{
    @autoreleasepool
    {
        return UIApplicationMain(argc,
                                 argv,
                                 NSStringFromClass([MyApplication class]),
                                 NSStringFromClass([MyAppDelegate class]));                
    }
}

In case you did not subclass UIApplication or UIApplicationDelegate you simply pass nil to the UIApplicationMain as the respective parameter.

What would be the swift implementation ? – Jamshed Alam Oct 10 '19 at 06:13 — Jamshed Alam, Oct 10 '19 at 06:13

score -5 · Answer 4 · answered Mar 01 '11 at 07:09

-5

There can only be one UIApplication instance in an application, you should not initialize the one new application object, use the static method of the UIApplication:+ (UIApplication *)sharedApplication.

answered Mar 01 '11 at 07:09

Jack.isswhu

1

How to subclass UIApplication?

4 Answers4

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