Extending Objective-C from D.

[Jeremie Pelletier via Digitalmars-d]

On Sunday, 17 January 2016 at 13:21:39 UTC, Jeremie Pelletier 
wrote:
> On Sunday, 10 January 2016 at 21:51:53 UTC, Guillaume Piolat 
> wrote:
>> On Saturday, 9 January 2016 at 10:09:12 UTC, Jeremie Pelletier 
>> wrote:
>>> 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.
>>>
>>
>> If you are looking to implement/override Obj-C methods in D, I 
>> have done it here deriving from NSView
>> https://github.com/p0nce/dplug/blob/master/window/dplug/window/cocoawindow.d#L426
>>
>> Using the Obj-C runtime, the D object declares a new class 
>> object, populates it with methods (inverse mapping is done 
>> with an instance variable containing "this"). Ugly, but works.
>>
>> Example of a method callback: 
>> https://github.com/p0nce/dplug/blob/master/window/dplug/window/cocoawindow.d#L499
>> Do not forget to prepend the callback arguments with id and 
>> selector.
>
> Sweet! I can at least get started while the full DIP gets 
> implemented :)
>
> I already have the Metal bindings more or less ready to 
> publish, I'll try to work on the Cocoa ones this weekend and 
> see how much I can progress!
>
> Oh by the way, I see the DIP declares blocks with the __block 
> keyword, shouldn't it be better to reuse delegate with 
> extern(Objective-C) ? Feels cleaner and more consistent with 
> the rest of the language to me.

Turns out I can't execute most of my bindings yet :(

I used interface inheritance all over the place to fully 
reproduce Cocoa and Metal, and while it does compile correctly, 
calling a objc method from an interface inherited through another 
interface causes a segmentation fault.

For example:

interface NSObjectProtocol {
     // dispose method here
}
interface NSString : NSObjectProtocol {}

If I get an instance of NSString and call its dispose method, the 
process segfaults. If I lift the dispose method into NSString it 
works correctly.

At this point I'll wait for more support, there's just too much 
to copy/paste :)