Matt Rosin wrote:
P.S. I should add that TT2 does not seem to let you test existence of a
related object, it just autovivifies. The .defined command and other
things I tried were not usable. However in my Perl code I am able to do
such tests (i.e. get_column, or check to see if customer is defined).
So I am not sure if the autovivification is only something from TT2 or
if it happens in the Perl code too (this is in a Catalyst environment
with MySQL). Thanks.
Matt
No, this is not limited to TT2, it is (I believe) the intended
behaviour of a belongs_to relationship. I can verify that something like:
My::Foo->belongs_to(bar => 'My::Bar', 'bar');
$foo = My::Foo->find(1);
$foo->update({bar => 1234}); # doesn't exist
unless ($foo->bar) {
die("Not found");
}
will not die, but rather create a Bar row with pk 1234. This appears
to be by design, as belongs_to creates an accessor of type "filter"
which will call find_or_create() instead of find() on the related
table (Bar in this case).
I think this only happens when the rel accessor is shared with the
column accessor for the join. Meaning that a rel named "bar" on
"bar_id" would not have this problem, because the accessor type would
be "single" instead of "filter".
I can understand the thinking that $foo->bar() should not be set if
the corresponding row doesn't exist, thus the autovivification. In
most cases this is something that would be enforced by constraints
within the DB.
But in my case I'd much rather it return undef or even throw an
exception upon not finding the related row. An exception is probably
much better than undef to differentiate from NULL.
Does this call for a new relationship type? Or maybe a different
accessor type? I must admit that I do not fully grasp "single" vs
"filter" accessors.
If it were a new relationship type, it could also default to a
join_type of 'LEFT'. Something like My::Foo->might_belong_to() maybe?
I'm sure the DBIC devs can shed some light on this discussion. There
might be some syntax I'm not aware of to force the behavior I'm
looking for.
Best,
Brian Kirkbride
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