Re: [Pyobjc-dev] Catergory Question ...

[Ronald O. <ron...@ma...>]

On 10 May, 2009, at 19:06, Mic Pringle wrote:

> Ronald,
>
> So is there no way at all the be able to call a Python pyobj-c class
> from Obj-C as from your earlier response you did imply this ??
>
> '...the same is true for methods you add in a subclass, those can be
> called from ObjC as well...'

You can call methods on a class that's defined in Python. You cannot  
have direct references to a class that's defined in Python though.

That is:

	BKTextile* object = [BKTextile new];		// This get's you a link-time  
error
	BKTextile* object = [NSClassFromString(@"BKTextile") new] // This  
should work



>
> I'm mainly a Obj-C programmer, and have only recently turned to
> PyObj-c as a way to utilise many libraries that simply aren't
> available to Obj-C, such as for processing Textile and Yaml ?
>
> I have got it working so far using another method I found on the
> internet which involves creating a wrapper class for the Python part
> and using NSClassFromString to instantiate the class, but I was hoping
> to drop these two extra files in favour of just using a header file
> and the original Python file like with the category stuff. Is this
> then not possible ?

AFAIK the only limitation is that you cannot have [APythonClass  
classmethod] in your code, you must use NSClassFromString to access  
the class object. This is purely for technical limitations, the ObjC  
compiler needs link-time access to the class when you call a  
classmethod, and that's impossible to arrange for using PyObjC.

Ronald
>
> Thank
>
> -Mic
>
>
> 2009/5/10 Ronald Oussoren <ron...@ma...>:
>> Mic,
>>
>> You cannot refer to the class directly in Objective-C, that's  
>> because PyObjC
>> will create the class at runtime and your ObjC code tries to link  
>> to it at
>> compile-time.
>>
>> I tend to write all my code in Python, using ObjC as a way to  
>> optimize code
>> where needed and to access API's that are not available in Python.   
>> This
>> means I tend to be able to get away with creating instances in  
>> Python code,
>> while still calling methods on them in ObjC.
>>
>> Ronald
>>
>> On 10 May, 2009, at 18:26, Mic Pringle wrote:
>>
>>> Hi Ronald,
>>>
>>> As you have probably seen, I now have categories working fine,  
>>> thanks
>>> to your help.
>>>
>>> You mentioned in one of your earlier replies that I can also do the
>>> same for subclasses, not just categories. So following this I have
>>> created a header file in Objective-C with the following contents ...
>>>
>>> #import <Cocoa/Cocoa.h>
>>>
>>> @interface BKTextile : NSObject
>>>
>>> - (NSString *)decodeTextile:(NSString *)aString;
>>>
>>> @end
>>>
>>> And then created the following Python implementation ...
>>>
>>> from Foundation import *
>>> import textile
>>>
>>> class BKTextile(NSObject):
>>>
>>>        def decodeTextile_(self, aString):
>>>                return u"it worked!"
>>>
>>> Which is pretty much what I've done to get the category to work,
>>> except when I try to compile I get the following error ...
>>>
>>> .objc_class_name_BKTextile referenced from:
>>> literal-pointer@_OBJC@__cls_refs@BKTextile in PythonServerTest.o
>>> symbol(s) not found
>>>
>>> Any ideas ??
>>>
>>> Thanks,
>>>
>>> Mic
>>>
>>>
>>> 2009/5/8 Ronald Oussoren <ron...@ma...>:
>>>>
>>>> On Friday, May 08, 2009, at 10:59AM, "Mic Pringle" <mic...@gm... 
>>>> >
>>>> wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> Just a quick question regarding categories.
>>>>>
>>>>> I have a hybrid Obj-c/PyObj-c application and I'd like to know  
>>>>> if I
>>>>> add a category in a PyObj-c module, will it be availble to use  
>>>>> in the
>>>>> Obj-c side of the project ??
>>>>>
>>>>> If so, does it just work or are there any special instructions I  
>>>>> need
>>>>> to follow to get it working ?
>>>>
>>>> Methods you add using an Python category are available in ObjC as  
>>>> well
>>>> (the same is true for methods you add in a subclass, those can be  
>>>> called
>>>> from ObjC as well).
>>>>
>>>> Two possible sources for confusion/problems:
>>>>
>>>> * Unless the methods you add are already known to the compiler  
>>>> you'll
>>>> have to write a header file that the ObjC compiler
>>>>  can use. You'll get compiler warnings otherwise.
>>>>
>>>> * Methods that you add in python by default have arguments and a  
>>>> return
>>>> value of type 'id'. This can be overridden by:
>>>>
>>>>  - information extracted from the superclass (if you override a  
>>>> method
>>>> PyObjC knows the new method should have the
>>>>    same signature as the one in a superclass).
>>>>  - the method is defined in an informal_protocol that's known to  
>>>> PyObjC,
>>>> the method signature is then extracted from
>>>>    that protocol
>>>>  - manual annotations (objc.accessor, objc.selector, ....)
>>>>
>>>> Ronald
>>>>>
>>>>> Thanks
>>>>>
>>>>> -Mic
>>>>>
>>>>>
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>>>>> _______________________________________________
>>>>> Pyobjc-dev mailing list
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>>>>>
>>>>>
>>>>
>>
>>