[Zope3-Users] need guidance

Duncan McGreggor duncan.mcgreggor at gmail.com
Wed Nov 30 04:44:22 EST 2005

On Nov 29, 2005, at 10:57 PM, Brad Allen wrote:

>> It sounds like a pain, and to be honest, at first it is a bit 
>> arduous. Not only does it get faster and become second nature, but 
>> chunks of it can be generalized and reused. It really doesn't take 
>> that long to get accustomed to it. And once you start doing it 
>> regularly, you gain a tremendous amount. Not just in the mere 
>> knowledge acquired, either... there's a subtle shift in your 
>> programming where you give extra attention to the 
>> data-generating/-populating code, which in turn makes you architect 
>> your information better ahd brings higher overall levels of 
>> organization to your project.
> So this style of Zope 3 development involves not using
> ZODB so much for permanent storage, but instead as a
> temporary scaffolding on which to hang the current version
> of class instances and their content. When you refactor
> your classes and interfaces, you just re-instantiate everything
> into the ZODB to recreate the site.

Like Chris said, a qualified "yes" -- i.e., during development. For a 
production alternative, he pointed to the generations tool. I haven't 
had a need to use it yet, but I've heard folks talking about it.

> It sounds great, except not all data can be simply regenerated.
> For stuff like port numbers and configuration, fine, it can be
> in ZCML or embedded in Python scripts.  But the site content
> generated by end users has to be stored somewhere, too.

I have several sites with base content that is pre-populated from 
python scripts and external files.

> If you throw away your ZODB and regenerate it, what happens
> to that data? Does your regeneration script transfer
> all that data to the newly generated ZODB?

Whenever I am told by client that they want me to build an application 
for them, and they want to be able to add data/content while I do it, I 
either gently educate them on the proven process that we use, or I walk 
away from the project. Maintaining content during development is almost 
always a nightmare. There are tools to use to enable this... 
approach... but in my mind (and many others') it's just not a good way 
to do development.

To come a little closer to answering your question, the only time that 
I have ever needed this kind of thing is on projects where we were 
delivering a product to multiple clients, pre-populated with default 
content. All of that content was added via python.

> I'd be interested in seeing the particulars of how
> you guys do that stuff. I've yet to run across a direct
> mention of how to create an arbitrary ZODB and
> start reading and writing objects.

As soon as you create an instance of a content object, you've written 
to the ZODB. Whenever you render a page that presents a content object, 
you've read from the ZODB. z3 "protects" the developer from the ZODB. 
You never have to do direct reads/writes. You're simply operating 
within a z3 "app"...

As for particulars, there are several emails in the archives for this 
list that detail z3 site setups. Even better, there are examples in the 
wild. IIRC, the cubic project had an example for this, and the 
"worldcookery" demo site might too. I'd certainly check out schooltool 
to see what they have done. Code-based site 
creation/setup/configuration will provide you with lots of ideas, 
hands-on examples, and a good sense of how to approach this.

> That seems to
> be a big piece missing from my understanding
> of how to work with Zope 3. Every ZODB example
> I've seen in the books seems to involve creating a content
> object that can be added via the ZMI.  However, I'm
> not finished with either book, and I have very likely
> missed something.

Yeah, I think you're looking for code-based content addition -- is that 
right? If so, you're going to want to spend some time looking at 
zope.app.zapi (a lot of which comes from zope.component). In 
particular, the createObject() function. Take a look at those projects 
I mentioned above... and other folks may have good suggestions for code 
examples on site creation and pre-population of content.

Hang in there ;-)


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