[Zope] RE: Two newbie questions

[Chris Fassnacht]

Evan,

> [Essentially: Why doesn't acquisition scan the whole database?]
>
> Did you realize that this is what your questions boil down
> to? <wink>  Do you
> really want to wake up every object in the ODB if you make a
> typo in a property
> name?  Be sure to specify what order objects are searched;
> this is important!
>

Yeah, this is basically what I was saying.  Sounds pretty simple-minded when
you put it that way.  Another one of those "seemed like a good idea at the
time" sort of things.

> Seriously, one of the most powerful aspects of acquisition is
> the way it lets
> you control the search context and ordering.  You decide
> which objects should
> be included and which are irrelevant, and what overrides what.
>
> It's not clear whether you understand the distinction between
> the containment
> hierarchy and the acquisition context.  The normal structure

I think you've hit the nail on the head.  I didn't understand that there was
any difference between the two.  I thought the acquisition context was
rigidly defined by the hierarchy.

> of the ZODB, with
> nested folders containing methods and objects, is a familiar
> organizational
> convenience.  Object IDs are unique *within their container*, but not

Right, and I understand "their container" to mean the default acquisition
context provided by the hierarchy, not just an object's folder.

> globally.  The hierarchy also provides a *default*
> acquisition context for each
> object, since the bare minimum context for an object is the
> straight line
> defined by its absolute URL -- the list of containing objects.
>
> Acquisition context can be much more convoluted than simple
> containment,
> however.  At *each step* in the resolution of a URL, an
> object can be acquired
> from *any previous object* in the URL.  This means that given
> "A/B/C/D", "A"
> must be in the root, "B" must be in "A" *or the root*, "C"
> must be in "A", "B",
> or the root, etc.  Essentially, a URL builds an "environment"
> (I prefer
> 'context') step-by-step.  You can leap around in the current
> environment with
> each new step, and then the target object or method is
> rendered in this
> environment.
>
> The canonical example of this is the standard_html_* objects.
>  The root always
> contains default values for these, which can be overridden by
> including a
> folder in your URL which contains objects of the same name.
> You can thus
> refine your requirements by inserting objects into the URL.
> One could, for
> instance, have a URL like
> "/styles/fancy/framed/extras/js/flash/docs/MyDoc"
> which accesses the same object as "/docs/MyDoc", but tells it
> to render using
> fancy, framed HTML with JScript and Flash animations.
>

Wow.  This is a fairly mind-blowing concept.  You're saying I can pick and
choose the stops I make on my way to an object and thereby create a unique
collection of contexts (with their associated methods) that can be used to
render the final object in the URL?  So if I wanted the same information,
say Info1, to be formatted for three different audiences, Aud1, Aud2, and
Aud3, then I could (after writing the necessarily individualized methods for
each audience) have three links like this: Root/Aud1/Info1, Root/Aud2/Info1,
Root/Aud3/Info1, even though the containment hierarchy didn't actually
reflect any of these URLs in its structure?  I'm going to have to think
about this some more.  It seems almost like a kind of on-the-fly method
inheritance.  Zope gets deeper every time I look at it.

> > I think Zope is a marvelous programming environment, and I think it
> > represents a much bigger shift in the web development
> paradigm than it seems
> > at first glance.  Regardless of my complaints about
> acquisition, I'll be
> > sticking with it.
>
> True enough, and good for you!
>
>

By the way, did you have any suggestions on my problem with getting a
"multi-context" path (e.g., Root/Aud1/Info1 or Root.Aud1.Info1) out of a
lines property and rendered using the looping construct you showed me
earlier?  I know it's something simple, but I can't find a helpful reference
to it anywhere.

Thanks again for your time and patience.

Chris