[Dbix-class] Testing for a join

[Bill Moseley]

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 fetching
a CD or Label then don't want to add a track.deleted =3D> 0 condition, but =
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
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