[Zope-dev] more __call__ ...

[Chris Withers]

(moving back onto list, hopefully my head/wall contact will save others
braincells ;-)

Jim Fulton wrote:
> > On an (almost) related matter, are there any docs (other than the code
> > ;-) for how __call__ is handles WRT to <dtml-var something>?
> > I had a look at DTMLMethod.py and PythonMethod.py and ended up very
> > confused...
> 
> Currently, DTML looks at something that it is going to render
> and tries to decide if it's callable. If it is, it checks to
> see if it has a true isDocTemp attribute. If an object is callable
> and has a true isDocTemp, then it is called with None and the DTML
> namespace. Otherwise, if an object is callable, it is just called.

So, if I give my product a class attribute of isDocTemp=1, what
signature should I give my product's __call__ method so it picks up the
DTML namespace?

> We are going to provide an alternate interface, so that if
> an object has a special method, then this will be called instead.

okay... which proposal/project is this in?

> > I think the 'client', rather than 'self' is what I'm after, but how can
> > I get it inside my product's __call__ method?

Hmmm... I don't suppose there's a nice definition of what the 'client'
is, what's likely to be in the namespace stack and what self is likely
to be in these circumstances lying around anywhere, is there? ;-)

> You can't really.  You should be able to infer it from the acquisition
> context. For example, 'client' should be aq_parent. 

    def __call__(self):
        """ """
        print self.aq_parent.id

This is called by a <dtml-var myObject> in standard_html_header which is
also called with a dtml-var in, lets say, the DTML documnet: myDocument.

The above code prints the id of this product instance's container. I was
expecting it to print the id of myDocument. Is this me misunderstanding
what the 'client' is, or is something else going on?

In either case, what do I need to go to get hold of what would be
PARENTS[0-1], if you see what I mean?

> Note that subtemplates
> are not invoked on the objects they are found in, but in the namespace
> they are called in. This is a bit weird and not really intensional. :(

I think I'm probably going to be relying on this, and I _think_ it makes
sense to me. I presume subtemplate calls are things like doing <dtml-var
myObject>? In which case it seems sensible to keep playing in the
namespace and just popping myObject on top as an instanceDict. I'm note
quite sure how you think this area should work adn what difference it
would make, could you elaborate? :-S

> > PS: In python product terms, whats' the difference between implementing
> > __call__, __str__ or render?
> 
> render?

Yeah, that's what I thought, but a coupla people have mentioned it.
Maybe they're thinking of DTML tags?

> __call__ implements the () operator (in C++ terms). It is the method
> you implement to make your object callable.
> 
> __str__ is the method you implement to control how your object is
> converted to a human readable string.

So what's the difference in terms of doing <dtml-var myobject> and
http://site.com/myobject, if there is any?

cheers,

Chris

PS: What I'm actually looking for out of all of this is the
getPhysicalPath() of the final object that was traversed through the
URL.
e.g: If the URL was http://www.nipltd.com/folder/somethingelse/myobject,
I'm looking for something like:
[<Application Instance at 0x000000> (Zope) , <Folder Instance at
0x000000> (folder) , <DTMLDocument Instance at 0x000000> (myobject)]

If there's an easier way to get this from within the __call__ method of
a python product, someone PLEASE tell me! ;-)