At 06:41 PM 06/12/02 +0100, Jeff AA wrote:
>Ok - full-circle back to encoding page state in links and hidden fields
>on the page itself, but it was an interesting loop!
[from a thread about saving state in links on the mod_perl list]
The other day Perrin and I discussed this state info, and where in MVC it
should be dealt with. I think I don't allow my Templates (or the View) to
do enough work building links -- instead I have often done it in the model.
The example is an application that has a search interface, where you might
get a page of results at a time and you need to save state from request to
request. And how best to track all the parameters that need to be passed
on every request.
This is a MVC-no-no I guess, but in my model (that knows what it needs to
do a query) I would setup the URL parameters for links back to the query
(such as prev|next links).
In the model I might do something like
$navigation = {
next => $self->build_search_href( 'start' => $next_page ),
prev => $self->build_search_href( 'start' => $prev_page ),
};
where build_search_href() knows all the state info that's used by the query
model. The build_search_href() function might build a query string, which
database to search, limit parameters and so on, for example, in addition to
the start offset.
and then in the template use:
<a href="[% search.navigation.prev %]">Prev</a> |
<a href="[% search.navigation.next %]">Next</a>
(but I'd add logic to see if there was a Next or Prev, of course)
But I guess that's the wrong way since it's placing HTML in the model.
It's also bad because other models can't add info to that link, such as
advanced/standard search form to use, "skin", brief/full view, etc.
So, the controller might do:
if ( $apr->param('query') ) {
# Decode query string
my $request = Controller::SearchArgs->new( $apr );
# Run query
my $results = Model::Query->new( $request );
$vars->{results} = $results;
# Now for the View
if ( $results->num_records ) {
$template->process( $results_template, $vars )
|| die $template->error();
return;
}
# See if we can offer some spelling help
if ( my $dictionary = $dict->lookup( $request->query_string ) ) {
$vars->{dictionary} = $dictionary;
}
$template->process( $no_results_template, $vars )
|| die $template->error();
}
Now, it's nice to be able to have template variables like
[% search.navigation.next_page %]
So, should the controller or the templates (view) build those links? I
kind of feel it's the programmer's responsibility to build the URLs so that
the controller will get them as expected -- and make the templates simple.
Anyone have good examples of how to build these state-saving links for use
in templates? Do you do them in the templates? Or do you have a view
module that builds them before calling process()?
Thanks,
--
Bill Moseley
mailto:[EMAIL PROTECTED]
