[Catalyst] Simple literal Model

John M. Dlugosz wxju46gefd at snkmail.com
Sat Feb 26 05:22:28 GMT 2011

  On 2/25/2011 9:30 AM, Ashley Pond V apv-at-sedition.com |Catalyst/Allow to home| wrote:
> What t0m suggested is perfectly fine but if you want to mimic the DBIC
> API with a different engine, this example does that (superficially and
> as a tutorial only): http://sedition.com/a/2739 Log file model–Apache
> access log. The reason that example makes sense is because the
> underlying model/data is similar: searchable, sortable rows. If you're
> trying to shoehorn in something dissimilar, you might be making a
> mistake.
> -Ashley
I'm not sure to what extent it is wise or correct.
The whole point of "models" is that it abstracts the model and I can change where the data 
comes from later, right?  So don't they all have an underlying abstract interface 
regardless of how they are sourced?
I can see that DBIC itself abstracts which database is used; e.g. SQL Lite for testing and 
MySQL on a dedicated server for deployment.  But I was thinking that the Model, over all, 
did a similar level of abstraction:  change from a database to a XML file or other 
representation, and the data is still presented the same way.

For example, I currently have 8 items, and want to just list them in Perl so I don't have 
to worry about another data representation or parsing it.  But if needs to become 
user-changable or grows to a few dozen items, a separate XML file would be better.  And if 
it grows to a search result of a few thousand items, it should be in a database.

Clearly there are differences in capabilities of a Model:  to wit, "all in" or 
"searchable".  And a full database can return different results depending on selected 
columns, across joins, etc.  So I think the level of abstraction is that of "a list of 
records".  The View is given a list of records, and the Controller knows to pull it by 
name directly, perform a search on a more complex model, or access an attribute of a more 
encompassing model.  It obtains the list and passes it to the View via the stash.

The examples I've read using DBIC use
     [% WHILE ( item = list.next) %]
and I can imagine that in general we don't have efficient random access to the rows; in 
C++ I would characterize this as a "forward iterator" or even weaker, if I can't make a 
copy of the earlier state and go forward a second time.

I would have hoped that the TT [% FOREACH %] directive would work here.  That seems like 
the natural means of abstracting the list.  That is, the controller can set anything into 
the stash that FOREACH knows how to handle, including a plain Perl array.

So, is it an oversight of the documentation examples or of the framework that FOREACH 
isn't used on the DBIC result set?


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