yes but what if you don't own the base class?

-----Original Message----- From: Steve Spicklemire [mailto:steve@spvi.com] Sent: Friday, February 11, 2000 3:35 PM To: jfarr@real.com Cc: djay@lucent.com; zope@zope.org Subject: Re: [Zope] Zope and Polymorphism

Hi Johnothan,

I think the problem with these (issubclass, isinstance) is that they deal with class objects, and they may not be that easy to handle in dtml. On the other hand, meta_types are just strings... so they can be easily created/changed. I still like the idea of simply defining some property in the base class that I can quickly check for in any instance

i.e.,

<dtml-in objectValues> <dtml-if "_.hasattr(_['sequence-item'],'iCanDoTheChaCha')">

blah blah blah....

</dtml-if> </dtml-in>

but if you're dead set against that I don't understand why you couldn't use something like:

<dtml-in objectValues> <dtml-if "checkObjectMetaType(_['sequence-item'], metaTypeToCheck)">

blah blah blah....

</dtml-if> </dtml-in>

where 'metaTypeToCheck' could be "Dokument" as mentioned in another post, and 'checkObjectMetaType' is defined as below.

-steve

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# # # Check a classes base types for a certain meta_type... a little # safer this time..... # #

def checkClassMetaType(theClass, meta_type): """ check a class... and all super classess for meta_type...."""

result = 0

if hasattr(theClass, 'meta_type') and theClass.meta_type == meta_type: result = 1 else: for subClass in theClass.__bases__: result = checkClassMetaType( subClass, meta_type) if result: break

return result

def checkObjectMetaType(self, object, meta_type): """ check and object for an ancestral meta_type..."""

try: if hasattr(object, 'meta_type') and object.meta_type == meta_type: return 1 else: return checkClassMetaType(object.__class__, meta_type) except AttributeError: return 0

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"Jonothan" == Jonothan Farr <jfarr@real.com> writes:

>> Isn't there some method like >> _.inheritsfrom(_['sequence-item'],'Folder')

Jonothan> There's issubclass() in Python. Is this what you're Jonothan> looking for?

Jonothan> issubclass (class1, class2) Return true if class1 is a Jonothan> subclass (direct or indirect) of class2. A class is Jonothan> considered a subclass of itself. If either argument is Jonothan> not a class object, a TypeError exception is raised.

Jonothan> -jfarr