Thanks for opening a ticket and describing the issue so well!
I'm not sure how this should be solved, but I was wondering how things
currently work for other C structs like NSRect or NSPoint. Are these handled as
special cases, or is there a more general way to deal with C structs?
Would it make sense to think about somehow mapping C structs to the Ruby Struct
class, or maybe a special CStruct class? It would be nice if this at least
offered a way to perform equality checks (==, eql?, equals?). For structs that
have defined attributes it would be great if this allowed getting and setting
attribute values (similar to what you can do with NSRect and NSPoint).
I might be totally off, so maybe someone who knows more about the internals of
MacRuby can comment?
On Nov 17, 2010, at 11:33 , Thibault Martin-Lagardette wrote:
> This is because protocols, in the Obj-C runtime, are not Obj-C objets per
> say, they are C structs.
> +protocolWithName returns an (id) (aka obj-c objet), but the actual returned
> pointer is just a pointer to a C struct, which causes the runtime to issue
> those warnings. It says "Hey, this method returned an objet, but it doesn't
> look like one!". Which is expected, but this should be improved.
> While it is true that in the Obj-C runtime, classes and objects are C structs
> too, they are obviously not the same kind of structures, which is why it
> doesn't work :-).
>
> In MacRuby, `Protocol` IS a real Obj-C objet, but not what the
> +protocolWithName method returns. This means that whatever you do with the
> returned valiue, it will crash, because it is not a real objet, and thus does
> not respond to any message.
> This also means that you cannot even do something like that:
> Protocol.protocolWithName("NSCoding") ==
> Protocol.protocolWithName("NSCoding")
> Simply because doing this will call the `#==` method on the left-most value,
> which is a C struct for a protocol, and not an Obj-C object.
>
> I created https://www.macruby.org/trac/ticket/999 , related to protocols.
> Please be aware that the attached patch still does not make it possible to
> override conformsToProtocol:, because calling `#==` on non-objets will crash,
> which is why I think MacRuby could handle Protocols a little better, right
> now I'm not sure it's "usable" per say.
>
> Sorry if I do repeat myself a little, but I want to make sure you understand
> why this does not work yet, and what you can and cannot do with protocols as
> of today :-).
>
> --
> Thibault Martin-Lagardette
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