[Zope] Object method calling rules

[Jim Fulton]

TFE MMS JARVIS JOHN wrote:
> 
> Hi all,
> After being pulled away for a bit, I'm finally back to Zopeing. Yay!
> 
> I know this is explained somewhere, but I can't seem to find where...
> 
> I have a Product that looks something like:
> 
> class myProduct(
> ...
> )
> ...
> 
>     view_html=HTMLFile('viewProduct',globals())
> ...
>     def __call__(self,REQUEST=None):
>         return self.view_html(self,REQUEST)
> ...
> 
> So I can use <!--#var myObjectInst--> to render it.
> I can also use <!--#call "myObjInst.aMethod()"--> to call a method.
> 
> My objects have part numbers of the form 'xxx-xxxxx-xx' as id's, so
> they have to be expressed as _['xxx-xxxxx-xx'] in python expressions.
> What I don't understand is why <!--#call "_['myObjInst'].aMethod()"-->
> returns an error: 'string' object has no attribute 'update_properties'
> By searching my mail archive, I found that I can use
> _.getitem('myObjInst',0)
> so that <!--#call "_.getitem('myObjInst',0).aMethod()"--> works.
> 
> My question: what is the difference between myObjInst and _['myObjInst']?
>  _['myObjInst'] calls the __call__ method?

Right.  The __getitem__ operator on the namespace object, _, tries to call
the object.  _.getitem(name, 0) doesn't call the object.  The second argument
indicates whether the object should be called.  This is a little unfortunate and
a bit hard to fix, for both technical and backward compatibility reasons.
 
> Pointers to pertinent documentation would be greatly appreciated (I
> know it exists--I've read it once before :^)

This *should* be documented in the discussion of the _ variable in the DTML 
manual .... e gads it is! ;)

See: http://www.zope.org/Documentation/Guides/DTML/DTML-HTML/DTML.html#pgfId-507695

Jim

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