[Dbix-class] Re: Testing for a join

[Bill Moseley]

To be a bit more succinct:

Is there a method to see if a given $rs will join to (or query from) table
"foo" and if so what alias is used?

I guess I could use $rs->as_query and a regular expression but wondered if
there might be a way that doesn't need to build the entire query.



On Thu, Dec 16, 2010 at 4:59 PM, Bill Moseley <moseley at hank.org> wrote:

>
> Music Database:  label -> cd -> track -> movement -> note
>
> So, there's a hierarchy of objects.
>
> Say, label has a "deleted" flag that always needs to be checked.  So, one
> option is to join and then add the check constraint in the base class:
>
> $rs =3D $schema->resultset( 'Track' )->join_label->check_deleted;
> $rs =3D $schema->resultset( 'Cd' )->join_label->check_deleted;
> $rs =3D $schema->resultset( 'Note' )->join_label->check_deleted;
>
>
> Where join_label() is a method in the specific resultset class -- e.g.
> ResultSet::CD has method join_label { return shift->search( undef, { join=
 =3D>
> 'label' } ) }, and likewise, ResultSet::Note has a join_label method that
> joins from note all the way to label.
>
> And then in the base ResultSet class check_deleted adds this to the
> resultset: sub check_deleted { return shift->search( { 'label.deleted' =
=3D> 0
> } ); }
>
> That works because every object is joined to the label object.
>
>
> Now, assume there's also a "deleted" flag on the track object.  If fetchi=
ng
> a CD or Label then don't want to add a track.deleted =3D> 0 condition, bu=
t if
> fetching track, movement, or a note I do want to add that condition.
>
> Is it possible to "know" in the base "check_deleted' method that the $rs =
is
> fetching either a track (or is joined to track) and then conditionally add
> the track.deleted check?
>
>
> --
> Bill Moseley
> moseley at hank.org
>



-- =

Bill Moseley
moseley at hank.org
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