Extending Objective-C from D.

[Jeremie Pelletier via Digitalmars-d]

Hello, I'm trying to see if I can write a full Cocoa app in D, 
and I'm having trouble creating D classes when the underlying 
Objective-C interfaces have methods.

It works for the app delegate because it needs to override them, 
but for other classes the compiler says the Objective-C methods 
aren't implemented in the D subclass.

I was successful in getting a simple application to boot with 
console errors about a missing NIB file. Its impressive how much 
you can get done so far :D

Now I'm trying to manually create the app and the delegate, 
completely bypassing NSApplicationMain with mixed success. Here's 
the main function:

     auto me = new MyApplication;
     auto dg = new MyAppDelegate;
     me.setDelegate(dg);
     me.run();

I even asserted after instantiating MyApplication it is identical 
to NSApplication.sharedApplication (using the objc_lookUpClass 
trick to emulate static calls) and they're the same value. The 
delegate also creates correctly, just like it did through 
NSApplicationMain reading the Info.plist file. neat!

But I crash when calling setDelegate. I marked the methods final 
in NSApplication's definition as it was the only thing I found 
passing the compiler. Without it I get the missing implementation 
errors. I tried to new the interface and that didn't work either.

So I'm at a loss on how to declare this. I could split 
NSApplication into the interface to derive from and the one to 
call functions on, but that kind of breaks everything and I can't 
use one in all definitions and cast to the other in all 
implementations, that would be crazy :)