[MacRuby-devel] Conforming to a protocol

Sun Nov 21 17:53:06 PST 2010

I commented the #999 ticket, I believe there is a way to make MacRuby classes automatically conform to protocols (once all required methods are implemented).

Let's try to get that done for the upcoming release :)

Laurent

On Nov 20, 2010, at 2:28 PM, Charles Steinman wrote:

> In case anyone needs it in the meantime, here is a working
> implementation of conformsToProtocol:
> 
> def conformsToProtocol(protocol)
>   supported = %w( AProtocol SomeOtherProtocol YetAnotherProtocol
> ).map {|name| Protocol.protocolWithName name} # List the protocols you
> want to conform to between the parns
>   supported.any? {|candidate| protocol.isEqual candidate } or super
> end
> 
> The reason this works is because Protocol *is* a real class, but it's
> derived from a base class different from NSObject. Obviously we'll
> want a better solution for MacRuby, but this will work in the
> meantime.
> 
> — Chuck
> 
> On Wed, Nov 17, 2010 at 4:42 AM, Eloy Duran <eloy.de.enige at gmail.com> wrote:
>> Regardless of the current state, having a real Protocol class and objects
>> that you can use to check against should be the goal. Let's discuss this
>> further on the ticket from now on, for completeness sake.
>> On Nov 17, 2010, at 12:44 PM, Thibault Martin-Lagardette wrote:
>> 
>> These structures are currently handled by Foundation's BridgeSupport file
>> (/System/Library/Frameworks/Foundation.framework/Resources/BridgeSupport/Foundation.bridgesupport)
>> <struct name='NSPoint' type64='{CGPoint=&quot;x&quot;d&quot;y&quot;d}'
>> type='{_NSPoint=&quot;x&quot;f&quot;y&quot;f}'/>
>> <struct name='NSRange'
>> type64='{_NSRange=&quot;location&quot;Q&quot;length&quot;Q}'
>> type='{_NSRange=&quot;location&quot;I&quot;length&quot;I}'/>
>> It's not very humanly readable, but MacRuby understands what this means, and
>> then knows NSPoint is a structure :-).
>> However, just for proving myself wrong, there IS a Protocol Obj-C objet (
>> see http://opensource.apple.com/source/objc4/objc4-437.1/runtime/Protocol.h ).
>> But I think my point stands, as I do think what is returned is the C struct,
>> not the class.
>> I think Laurent might know a little better though :-)
>> --
>> Thibault Martin-Lagardette
>> 
>> 
>> On Nov 17, 2010, at 12:19, Martijn Walraven wrote:
>> 
>> 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
>> 
>> _______________________________________________
>> MacRuby-devel mailing list
>> MacRuby-devel at lists.macosforge.org
>> http://lists.macosforge.org/mailman/listinfo.cgi/macruby-devel
>> 
>> _______________________________________________
>> MacRuby-devel mailing list
>> MacRuby-devel at lists.macosforge.org
>> http://lists.macosforge.org/mailman/listinfo.cgi/macruby-devel
>> 
>> 
>> _______________________________________________
>> MacRuby-devel mailing list
>> MacRuby-devel at lists.macosforge.org
>> http://lists.macosforge.org/mailman/listinfo.cgi/macruby-devel
>> 
>> 
> _______________________________________________
> MacRuby-devel mailing list
> MacRuby-devel at lists.macosforge.org
> http://lists.macosforge.org/mailman/listinfo.cgi/macruby-devel

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.macosforge.org/pipermail/macruby-devel/attachments/20101121/6ba14eb0/attachment-0001.html>