[Pyobjc-dev] unbound methods

[<bb...@ma...>]

On Monday, Dec 23, 2002, at 14:30 US/Eastern, Ronald Oussoren wrote:
>>     Rethinking this, the above method call may not work in some  
>> situations.  In particular, in class clusters it is often the case  
>> that you generally interact with some private subclass.  For example,  
>> NSArray.count(someArray) will not actually do what you want because  
>> instances of NSArray are never directly instantiated-- just private  
>> subclasses.
>>
>> In [6]: a = NSArray.arrayWithArray_([1,2,3,4,5])
>> In [7]: a.count()
>> Out[7]: 5
>> In [8]: NSArray.count(a)
>> ---------------------------------------------------------------------- 
>> -----
>> ValueError                                Traceback (most recent call  
>> last)
>>
>> ?
>>
>> ValueError: NSInvalidArgumentException - *** -count only defined for  
>> abstract class.  Define -[NSCFArray count]!
>>
>
> That's just like in 'normal' python types: If you call NSArray.count  
> you get the count method defined by NSArray instead of the one defined  
> by the class of your object. That is not very Objective-C-like, but  
> this is needed to implement super(cls, self).count().

Right.   However, the ability to use unbound methods is very much a  
feature of Python that a lot of people use...

Is there a way to support this a bit more cleanly/flexibly in light of  
ObjC's ability to have a class method and an instance method of the  
same name?

I.e. say a class Foo implements both a +foo and a -foo method and you  
have an instance called aFoo.

You really want to be able to do...

     Foo.foo(aFoo)

... and call the instance method.   But you also want to be able to  
do...

     Foo.foo()

... and call the class method.  Or, maybe, you want to do...

     Foo.foo_(aFoo)

... where you are calling the class method and passing an instance as  
the argument?

This isn't terribly clear, but I'm hoping it gets across the general  
idea that we should be able to support both class and instance methods  
that are named the same....

One possibility would be to pass a kv argument that indicates that the  
class implementation should be used if there is both a class and an  
instance version-- i.e. Foo.foo(aFoo, useClassMethod=1)?

But that would not allow an unbound version of the method to be  
obtained that is explicitly tied to class or instance...?

b.bum