[Zope-dev] SOLVED: Using recursion with a SQL method

[Jim Cain]

I finally figured this out for myself. Apparently something like:

<dtml-var "some_object(parameter_name=value)">

results in a namespace stack in some_object that has *only*
parameter_name defined, and no other namespaces may be accessed. As a
result, using this for recursion fails.

The solution was to call some_object this way instead:

<dtml-with "_.namespace(parameter_name=value)">
   <dtml-var some_object>
</dtml-with>

This creates a new namspace on the stack with the proper value of
parameter_name, but other namespaces, including the one containing other
Zope objects, are still accessible.

An alternative method is:

<dtml-call "REQUEST.set('parameter_name', value)">
<dtml-var some_object>

but this is slightly different in that parameter_name is now defined
within the scope of the object calling some_object, not just during the
call to some_object.

It seems that I'm finally getting the hang of the namespace stack. It is
similar to dictionaries in PostScript, from what I can remember of them.

If I have explained something incorrectly, I would appreciate being
enlightened. :-)

Cheers,
Jim

---Original Message---

All,

I have a MySQL table "category" with the following schema:

id         number
name       char
parent_id  number

The table is self-referencing in that the parent_id points back to an
ID. This structure renders a hierarchical listing of categories, with the
root categories having a parent_id of -1.

I have a SQL method to select category names and IDs by their parent ID:

ID:        Query_category_by_parid
Arguments: parent_id:required:int
Query:     select id, name from category
           where <dtml-sqltest parent_id type=int>
           order by name

I have a DTML method which calls itself recursively to find a list of
categories starting with the specified parent:

ID: list_categories

  <dtml-in "Query_category_by_parid(parent_id=parent_id)">
    <p><dtml-var name> (<dtml-var id>)</p>
    <dtml-var "list_categories(parent_id=id)">
  </dtml-in>

This however, doesn't work. It appears that the second call to
Query_category_by_parid, within the second call to list_categories, fails.

Here is the URL: /list_categories?parent_id=-1

This is the error I receive:

  Error Type: NameError
  Error Value: Query_category_by_parid 

And here is the traceback:

[snip]

I have a feeling I'm missing something obvious, such as a problem
with the namespaces. Any help would be greatly appreciated.

Cheers,
Jim