[Catalyst] Model/Controller logic separation - best practices?

[Ian Sillitoe]

Thanks Zbigniew. Yes, I decided to take this line after finding one of Matt
Trout's replies to a related thread ("Doing work inside the DBIx::Class
model"). Seems this question is being asked a lot - someone mentions an
entry on the FAQ - if so, Matt's rule of thumb made a lot of sense to me:

"If the operation is on multiple rows, make it a resultset method.

If the operation is on a single row, make it a method on the row object.

If the operation is on a bunch of different things and neither of those
make sense, make it a method on the schema object."


Cheers,

Ian



On Sat, Mar 8, 2008 at 8:24 PM, Zbigniew Lukasiak <zzbbyy at gmail.com> wrote:

> On Tue, Mar 4, 2008 at 8:35 PM, Ian Sillitoe <catalyst at sillit.com> wrote:
> > Hopefully there is a quick and obvious answer to the following - if so,
> > apologies for the length of this email. Apologies in advance also if
> this is
> > considered off-topic and/or covered in previous threads - I have trawled
> > around for a while (and recently got Jonathan's book !) but all my
> solutions
> > seem a bit like hacks and I'm hoping for a "Best Practice".
> >
> > My problem: given a row from table A, I would like to be able to return
> > related entries from table B ideally from within a template (unless this
> is
> > committing some kind of MVC heresy), I was thinking something like the
> > following:
> >
> > Controller/TableA.pm:
> > $c->{stash}->{row_a} =3D $c->model('MyDBIC::TableA')->find('id');
> > $c->{stash}->{template} =3D 'view_a.tt2';
> > $c->forward('Catalyst::View::TT');
> >
> > /root/src/view_a.tt2:
> > [% rows_b =3D row_a.get_related_rows( optional =3D> param ) %]
> > [% FOREACH row_b =3D rows_b %]
> >   [% DisplayRow(row_b) %]
> > [% END %]
> >
> > However, there is a reasonable amount of logic required to get the
> related
> > rows - the relationship between A and B is too complicated to
> encapsulate in
> > a static "has_many" (especially with the optional params) so I can't use
> > "row_a.search_related()". Assuming this is the case (rather than my DBIC
> > incompetence):
> >
> > 1) where is the best place to put this logic? (Controller::ModelA.pm,
> > DBIC::ModelA.pm, ResultSet::ModelA.pm??)
> >
> > 2) following from 1) what is the best way of accessing this logic from
> the
> > template?
>
>
> I would create an additional method in MyDBIC::TableA and then call it
> in the template like:
>
> [% rows_b =3D row_a.the_new_method( optional =3D> param ) %]
>
> If you needed to find the rows from the TableB independently from any
> row in TableA you'd need to add that method to the TableB::ResultSet
> class (or whatever name you'd use for it).  And then you could use it
> like:
> [% rows_b =3D b_rs.the_new_method( params ) %]
>
> Cheers,
> Zbigniew Lukasiak
> http://perlalchemy.blogspot.com/
>
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