[Catalyst] Template::Toolkit + Empty Lists
list at markblythe.com
Tue Aug 1 07:37:58 CEST 2006
This is slightly off-topic, but since I'm running into this problem
while using Catalyst, I'm hoping that others on the list may have
already solved it.
I was writing a simple template today, using TT + DBIC. I had an
object and was exercising a has_many relationship. I simply wanted to
see if any rows had been returned. It seemed simple enough:
[% SET children = parent.children %]
[% IF children.list.size %]
[% END %]
Well, it turns out that the size will always be >= 1, because TT can't
seem to handle an empty list. If the method called (parent.children)
returns an empty list, TT will substitute the return value with an
empty string: '''.
I tried to think of a general idiom to check for a non-empty list
[% IF children.defined %] # no, because the empty string is defined
[% IF children %] # breaks if you return a single-element list with a
zero: ( 0 )
[% IF children != '' %] # breaks if you return a single-element list
with an empty string: ( '' )
Of those three, the last one seems to be the least-common valid use
case, so I'm thinking I'll use that. It's painfully stupid looking,
so I may hide it (actually, the reverse) in an "is_empty" vmethod.
I know I can get around this specific DBIx use case by using a
resultset instead. However, I just know this will bite me again under
other circumstances, and I want to have a workable solution for
dealing with empty lists under TT.
Has anybody solved this reasonably well? Am I missing something basic?
More information about the Catalyst