[MacRuby-devel] Conforming to a protocol
Laurent Sansonetti
lsansonetti at apple.com
Mon Nov 22 18:30:26 PST 2010
I fixed a bug in your fix and improved it, so that we will automatically register the given protocol in the class, therefore the second call to conformsToProtocol: will be faster.
Please give it a try guys, it should be available in tonight's nightly build.
Laurent
On Nov 22, 2010, at 3:12 PM, Eloy Duran wrote:
> I just pushed a fix for this which checks if the class, or instance, implements the required methods for the protocol given to conformsToProtocol:. Please give it a try :)
>
> Eloy
>
> On 22 nov 2010, at 02:53, Laurent Sansonetti wrote:
>
>> 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="x"d"y"d}'
>>>> type='{_NSPoint="x"f"y"f}'/>
>>>> <struct name='NSRange'
>>>> type64='{_NSRange="location"Q"length"Q}'
>>>> type='{_NSRange="location"I"length"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
>>>>
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