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

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

On 8 May, 2009, at 13:44, Mic Pringle wrote:

> Okay, fantastic !
>
> Would it be possible for you to give me an example of your last point
> (re: manual annotations for some method you may use in a category) as
> this is the only part I don't have any experience with ?
>
> I am looking to add two methods to NSString, one which returns a
> string and another which returns an array.
>
> This would be greatly appreciated.

Both strings and arrays are objects and hence no manual annotation is  
needed, something like this should work:

class MyStringCategory (objc.Category(NSString)):
      def myStringValue(self):
           return u"hello"

      def myArrayValue(self):
           return [1,2]


You only need manual annotations when an argument or return value is a  
basic C type (such as a C "int" or "NSPoint"). Adding annotations is  
described in the pyobjc documentation and is definitely advanced  
behaviour because it uses some very lowlevel machinery.


Ronald
>
> 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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>>