[Zope] acces to file properties on a precondition - WILL SUMMARIZE

[Oliver Bleutgen]

Didier Georgieff wrote:
> Hello,
> 
> Just trying to test the new (?) policy for writing more how-tos and 
> summarized text for the community and see the right (tm) to do it ;-
> )
> 
>  - I have a subclassed file (with some more properties like 
> 'approved')
> 
>  - I want to use the precondition to check if the file is approved 
> before allowing the donwload
> 
>  - i have a dtml-method for doing it and all is fine __exept__ that the 
> context of this script seems to be the container and not the file.
> 
> The precondition method aquire the property ('approved') from the 
> container (folder) and __not__ from the file.
> 
> I tried to use lotta <dtml-with>, some aq_explicit, without luck.
> 
> 
> I also send a mail from the precondition (with the REQUEST and 
> some id/title as informations) for debugging, and it shows that 
> __everything__ comes from the container.
> 
> 
> So, I tried to see where is the problem with an external method 
> (stolen from Dieter)
> 
> def baseHasAttr(object,attrname):
>     obj= getattr(object,aq_base,object)
>     return hasattr(obj,attrname)
> 
> and calling <dtml-if "baseHasAttr(this(),'approved')> 
>>from the precondition script.
> 
> and this test shouts : __false__ even if there __is__ an 'approved' 
> property on the file object.
> 
> 
> So i'm lost, and can't figure why i can't access the object instead of 
> the container in the precondition.
> 
> Is it because of a wrong syntax ?
> Did i missed some aquisition trick ?
> Do this fails because it's derived from file ?



Didier, I might be wrong, but looking at OFS.Image (Zope 2.3.3) I see

  if self.precondition and hasattr(self,self.precondition):
             # Grab whatever precondition was defined and then
             # execute it.  The precondition will raise an exception
             # if something violates its terms.
             c=getattr(self,self.precondition)
             if hasattr(c,'isDocTemp') and c.isDocTemp:
                 c(REQUEST['PARENTS'][1],REQUEST)
             else:
                 c()
i.e. c (your precondition script) gets passed REQUEST['PARENTS'][1] as 
the "client" argument. That should explain why your precondition sees 
the parent of your file-like object.
Put it also get's passed REQUEST, so perhaps
file_obj = context.REQUEST['PARENTS'][0] should give the file-object itself?

cheers,
oliver