[Zope-dev] ZPatterns example update....

2000-12-28 Thread Steve Spicklemire



Hi Folks,

   The Dumb ZPatterns example is updated. Now there is some more
realistic object referencing going on, borrowing of code snippets
between Specialists and suchlike. There is also more in the way of
reasonable documentation, though everything is in flux, and it still
doesn't resemble a truly completed product. I just feel the need to
get things finished enough that I can stop thinking about them for a
while. ;-) In particular there the ToDos now hold references to Doer
and Deliverable, and no 'lists' are maintained. One thing I need to do
is to have these references automatically 'fixed' when a 'referred to'
entity is removed or modified in such a way that the link should be
broken that's for the next version. If I'm not careful.. it won't
be a 'simple' example anymore. There's got to be a line here somewhere
(in the sand?).

take care,
-steve


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Re: [Zope-dev] ZPatterns question

2000-12-28 Thread Steve Alexander

Steve Spicklemire wrote:

 
 CS 2. Is it planned to provide something like a virtual folder
 CS which acts like a normal object manager but is controlled via
 CS ZPatterns (so actually something like Folder with Customizer
 CS Support just without the "anchor" in ZODB.  (would also
 CS require some mechanism asked for in 1.)
 
 Hmmm... I'm not sure what you're after here. Why not just use
 a Specialist? In what sense do you want it to be virtual?
 (Are you looking for a dynamic traversal interface that 
 would allow you to map URLs to objects that are managed by
 ZPatterns? Can you give an example?)

Reading this just after reading the source to Specialists.py, I had a 
thought; and tried it out; and it works! :-)

You can use SkinScript to define __bobo_traverse__ for a particular kind 
of DataSkin in a Specialist.

For example:

   WITH SELF COMPUTE __bobo_traverse__=traversal_method

Then, define a method in the specialist (or rack) called 
traversal_method. I used a PythonScript, and gave it the parameter list 
"REQUEST, name".
Make your method return the appropriate object to traverse to from your 
DataSkin, depending on the name passed. Something like

   return getattr(container.path.to.somewhere, name)

That's the simple version, and it won't give the traversed-to object the 
correct context most of the time. To do that, I'd need to use an 
external method, and use the __of__ method to give the returned object 
an appropriate context.

However, it is a start, and proves that it can be done.

Take a look in the __bobo_traverse__ method of Specialists.py (from 
ZPatterns) for a good algorithm for traversal. The variable _marker is 
almost always a class attribute initialized to [], to make a unique 
object, as a sentinel.

--
Steve Alexander
Software Engineer
Cat-Box limited
http://www.cat-box.net





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Re: [Zope-dev] ZPatterns question

2000-12-28 Thread Steve Alexander

Steve Alexander wrote:


   return getattr(container.path.to.somewhere, name)
 
 That's the simple version, and it won't give the traversed-to object the 
 correct context most of the time. To do that, I'd need to use an 
 external method, and use the __of__ method to give the returned object 
 an appropriate context.

However, if all you are doing is saying "does this object have the named 
attribute? if not, get it from another specialist", and you're using 
Specialist.getItem() to do the latter part, then the object you want 
comes ready-wrapped in the appropriate context, courtesy of the Rack 
that gives it to you!

-- 

Steve Alexander
Software Engineer
Cat-Box limited
http://www.cat-box.net



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