How can I force list context in Template Toolkit with RDBO? - perl

Question

I have a TT plugin that does the trivial unique ids:
sub get_unique_uid_tt {
my ( $classname, $o ) = #_;
my %h;
foreach my $item ( #{$o} ) {
unless ( exists $h{ $item->id } ) {
$h{ $item->id } = 1;
}
}
return keys %h;
}
where the template call is simply:
[% Namespace.get_unique_uid_tt( data.users ) %]
and "data" is an RDB Object, users being one of its relationships. I have verified that the ".users" returns a list in Perl directly, whether the relationship has one or many elements.
However, it appears that TT returns the element for single-element lists, while properly returning lists for multiple element.
I looked this up and found that you can force list context with ".list":
[% Namespace.get_unique_uid_tt( data.users.list ) %]
This does not work as intended for single-element lists, as a Data::Dumper revealed:
$VAR1 = [
{
'value' => 1,
'key' => '__xrdbopriv_in_db'
},
{
'value' => bless(
... snip ...
),
'key' => 'db'
},
{
'value' => '1',
'key' => 'id'
}
];
instead of the expected
$VAR1 = [
bless( {
'__xrdbopriv_in_db' => 1,
'id' => '1',
'db' => ... snip ...
}, 'DataClass' )
];
Is there any other simple way in TT to get a list of objects, even on single-element lists? (One approach is to rewrite the function, but one that does not would be preferable)

Answer 1

Found this on the TT mailing list:
http://lists.template-toolkit.org/pipermail/templates/2009-December/011061.html
seems like TT's ".list" has trouble converting objects to lists in general, not just RDBOs.
The suggestion is make a vmethod:
$Template::Stash::LIST_OPS->{ as_list } = sub {
return ref( $_[0] ) eq 'ARRAY' ? shift : [shift];
};
I added this to my context object (same idea):
$context->define_vmethod(
'list',
'as_list',
sub {
return ref( $_[0] ) eq 'ARRAY' ? shift : [shift];
},
);

Answer 2

It's not quite what you're after, but could you alter the TT plugin to handle both lists and single items?
sub get_unique_uid_tt {
my ( $classname, $o ) = #_;
my %h;
if (ref $o eq 'ARRAY') {
foreach my $item ( #{$o} ) {
unless ( exists $h{ $item->id } ) {
$h{ $item->id } = 1;
}
}
}
else {
return ($o->id);
}
return keys %h;
}