[Pyobjc-dev] Re: 1.0?

[Ronald O. <ous...@ci...>]

On Wednesday, Jun 18, 2003, at 20:00 Europe/Amsterdam, Just van Rossum 
wrote:

> Ronald Oussoren wrote:
>
>> I think this is related to finding all classes for the frameworks when
>> loading. I'm going to test if this is really true. It it is true we
>> need to add a module-like object to sys.modules when someone imports
>> Foundation/AppKit/.... That object should initialize classes only when
>> someone tries to use them, instead of always initializing all classes.
>> E.g. it will have a __getattr__ like this:
>>
>>   def  __getattr__(self, name):
>>       cls = objc.lookUpClass(name)
>>       if definedInBundle(self.__bundle, cls):
>>           setattr(self, name, cls)
>>           return cls
>>       else:
>>           raise ValueError, "No such attribute"
>>
>> Additional work is needed because of 'from AppKit import *', if
>> someone accesses __all__ we still have to find all classes at once.
>
> Quick idea: why not use a static list of class names, if that can save
> us time?
That is a bit risky, if the __all__ contains names that are not 
available you'll get an import-error
when doing an 'import *'. Maybe we can find an easy way to detect what 
classes are available, it will
probably suffice to do something like this:

CLASSNAMES=(
	# 10.1
	( 'NSObject', ... ),
	# 10.2
	( ... ),
	# ...
)
__all__ = []

for nameList in CLASSNAMES:
	try:
		objc.lookUpClass(nameList[0])
		all.extend(nameList)
	except objc.error:
		pass

E.g. probe for one of the classes added in a release and then add all 
classes defined in that release.
That should be a lot cheaper than what we currently do.

>
> Something in between: make __all__ a static list, but have the
> __getattr__ do a dynamic lookup anyway if the name isn't in the list.
>
> I noticed that for even minorly complex apps "from AppKit import *" is
> indispensible, so I don't think a solution that only works if you
> _don't_ do that is out of the question.
>
> To what extent could class objects be lazy? Ideal would be if
>
>     from AppKit import NSSomeClass
>
> was really cheap, and that the class was only fully initialized if it
> was used (subclasses or instantiated).

We already build minimally initialized classes, the problem is that 
[NSBundle bundleForClass:] seems to be very expensive. That is at least 
what I remembered from the previous time this came up, I think 
bundleForClass did a lot of I/O for every class we look at. At the time 
there were more important issues, but I think this is the major 
technical issue with the bridge at the moment.

Ronald