Re: [Zope] How can a method know if it was acquired?

8 Jul 2003

      Thanks, Dieter!

Argh... this should be easy to do... another thing Zope should be doing 
for us...

On Tuesday, July 8, 2003, at 03:55 AM, Dieter Maurer wrote:
...
Itai Tavor wrote at 2003-7-7 20:00 +1000:
...
I got a folderish python product with the following method:
def SKU(self):
         """ Return our SKU for the catalog """
         return self.sku
The problem is that when objects contained in instances of this 
product
are cataloged, they acquire the SKU method, so they also get the sku
property. That is bad. So what I need is something like this:
def SKU(self):
         """ Return our SKU for the catalog """
         if (I was acquired):
             return None
         else:
             return self.sku
But I can't figure out how to do that. Help?
I fear this is impossible and would not be the right way either.
The right way (in my view) would be to make indexes manageable
and allow to set 3 boolean properties:
ALLOW_ACQUISITION= 1 # to indicate that attributes may be acquired
  HIDE_EXCEPTIONS= 1   # silently ignore (most) exceptions during calls
  ALLOW_CALL= 1        # indicate that attributes are called when 
callable
I have implemented an "IndexBase" class that determines the value
of object "obj" for index "id" in the following way:
def getValue(self,obj,default= None):
    '''the value of *obj* with respect to this index.'''
    marker= self
# determine base value
    id= self.id
    if self.ALLOW_ACQUISITION:
      val= getattr(obj,id,default)
    elif hasattr(aq_base(obj), id): val= getattr(obj,id)
    else: val= default
if safe_callable(val):
      if not self.ALLOW_CALL: return default
      try: val= val()
      except EXCEPTIONS_NOT_TO_BE_CAUGHT: raise
      except:
        if self.HIDE_EXCEPTIONS: return default
        raise
    return val
Dieter
Itai Tavor                       "Je sautille, donc je suis."
itai@iinet.net.au                           - Kermit the Frog
-- "Supposing a tree fell down, Pooh, when we were underneath it?"
-- "Supposing it didn't," said Pooh after careful thought.