[Zope] Adding ZClass Instances Programatically -- the theory?

[Kevin Dangoor]

Hi,

----- Original Message -----
From: Matt Jacobus <ado06@dial.pipex.com>
To: <zope@zope.org>
Sent: Sunday, November 07, 1999 5:01 PM
Subject: [Zope] Adding ZClass Instances Programatically -- the theory?


>
> In the How-To written by tazzzzz it is explained that in order to add an
> instance of a zclass you need to make the following call:
>
> <dtml-call "YourZClass_add(_.None, _, NoRedir=1)">
>
> As per the DTML doc, generally a folder or DTMLDocument is passed in as
the
> first argument and the REQUEST is passed as the second.  Would someone be
> kind enough to describe the theory behind passing in None as the client
and
> "_" as the REQUEST mapping.

Michel Pelletier talks about this a bit here:
http://lists.zope.org/pipermail/zope/1999-September/010933.html

Generally, AFAIK, the idea is that you need to pass *something* along to
tell the method its context. We don't necessarily need to pass a client.
Passing in the _ namespace works just fine to give the right context.

> In my code I end up using the following so that the new instance will be
> created in a subfolder:
>
>     <dtml-with subfolder>
>     <dtml-with "manage_addProduct['YourProduct']">
>        <dtml-call "YourZClass_add(_.None, _, NoRedir=1)">
>     </dtml-with>
>     </dtml-with>
>
> But once again I'm not entirely sure *why* it is that pushing the
> subfolder's namespace on top of the stack and then passing the stack into
> the REQUEST argument for YourZClass_add results in the instance being
added
> into subfolder.
>
> Intuition would tell me to simply pass in the subfolder and the REQUEST
> object as opposed to manipulating the stack directly and passing None and
_.
>
> What I think I'm really trying to understand is how the
> createInObjectManager method resulting from:
> <dtml-with "YourZClass.createInObjectManager(REQUEST['id'], REQUEST)">
> ends up with self populated with the correct folder.

Ahh.. I see why this is somewhat confusing. This is, in fact, a function of
"createInObjectManager". Basically, createInObjectManager expects to be
called a couple levels down from the target ObjectManager. Why? Because of
the manage_addProduct that stands in between. This is how
createInObjectManager is designed to work...

When I wrote that howto, I figured out a lot of it by looking at the
management interface. If you just take a look at the HTML source of pages in
the management interface, you can kind of see how manage_addProduct is
called to add objects. Then createinObjectManager will create the new object
in the ObjectManager that called manage_addProduct.

I hope this is more helpful than confusing :)

Kevin