Re: [Pyobjc-dev] Access to 'hidden' class-methods

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

On Saturday, Jan 11, 2003, at 17:31 US/Eastern, Ronald Oussoren wrote:
> Some time ago there was a discussion about access to class-methods 
> with the same name as an instance-method. Currently this is not 
> possible.
>
> One of suggestions was to add pyobjc-specific attributes to proxy 
> objects. I've implemented, but not yet fully tested this. After I 
> check this in you can do:
>
> 	NSObject.pyobjc_classMethods.description()	# Call +description
> 	a = NSObject.new()
> 	a.pyobjc_classMethods.description()  # Also call +description
> 	a.pyobjc_instanceMethods.description() # Call -description
>
Could this be simplified by requiring the developer to go through 
class() to get to the class method?

NSObject.pyobjc_classMethods.description() # invoke class method
a = NSObject.new()
a.class().description() # invoke class method
a.description() # invoke instance method

This doesn't solve the overall problem that Ronald's solution 
addresses, but it would work most of the time [I think].

> I've not yet added an pyobjc_instanceMethods attribute to 
> class-proxies. Another restriction is that reflection doesn't work yet 
> for the contents of these attributes, 
> dir(NSObject.pyobjc_classMethods) will not return a list of class 
> methods.

Since we have to go through this extra hoop anyway, maybe the answer is 
to hang the classMethods and instanceMethods attribute off of the class 
object?

a.class().pyobjc_classMethod('description')
a.class().pyobjc_instanceMethod('description')

Actually -- maybe the right thing to do is to bridge the following two 
methods on NSObject...

     - (IMP)methodForSelector:(SEL)aSelector;
     + (IMP)instanceMethodForSelector:(SEL)aSelector;

... such that they return unbound class/instance methods, as 
appropriate.  This would make it possible to do:

     a.class().methodForSelector_("description")(a.class())
     a.class().instanceMethodForSelector("description")(a)

May look odd, but it is certainly 'pythonic' in that returning a 
callable from a method/function is fairly common practice.

This also obviates the need for doing introspection at the level of 
generating an inventory of methods for the class with some 
categorization.

> I'm not yet completely happy with this solution because you cannot 
> override these hidden methods in subclasses, that is you cannot define 
> a class-method 'description' in your subclass of NSObject(*). But 
> because this should rarely be necessary I can live with this.

Still a problem with the above ...  but more a problem with method 
declarations themselves.

Maybe the answer is to have specific API for adding methods to a class. 
  I.e.:

     a.class().pyobjc_addClassMethod("description", <callable>)
     a.class().pyobjc_addInstanceMethod("description", <callable>)

The developer could declare this something like:

class MyClass(NSObject):
     def class_description(self):
	    ... do whatever here ...

MyClass.pyobjc_addClassMethod("description", MyClass.class_description)

Or something like that.

b.bum