OT: Templating systems (was RE: [Catalyst] New default screen for Catalyst)

[John Siracusa]

On 10/21/05 12:27 AM, Perrin Harkins wrote:
> John Siracusa wrote:
>> Er, call me crazy, but I don't want my views doing selects either.  As far
>> as I'm concerned, the only think a template is allowed to do is rearrange
>> the data I pass it and synthesize values based on that data.  No selects, no
>> db access at all.  How do I enforce it?  Er, code reviews, I guess :)
> 
> What, Rose::DB::Object doesn't do lazy-loading? :) I think that's the
> sort of select that Bill was talking about.
> 
> We had a discussion about using callbacks vs. getting the data up front
> on the TT list a while ago.  The thread is here if anyone is interested:
> http://template-toolkit.org/pipermail/templates/2002-April/003119.html
> 
> I'm not entirely decided about this.  In theory I think it's probably
> better to get the data up front, but passing Class::DBI objects to a TT
> template is so easy that it's just about irresistible.

As I replied to Bill off-list, I don't pass hashes or arrays of data to
views, nor do I pass db objects.  I pass a form object, which is already
populated with all the info I need.  (Rarely will the view also need the
associated db object, but if it does I can pass that too.)  So I'm firmly in
the "get the data up front" camp :)

The flow is like this:

    1. Instantiate and load the db object.
    2. Initialize the form object with the db object.
    3. Pass the form object to the view
       (and maybe the db object too, but usually not.)
    4. The view asks the form object to render its fields
       (or pieces of fields, or passes the fields or form object
       onto other sub-views, etc. etc.)

-John