[cgiapp] Model design in C::A/Titanium

[Richard Jones]

I know we've been around here before in some related topics, but I would 
appreciate some feedback on a possible MVC structure for a 
Titanium/CGI::App that I am currently building.

I'm using CA::Dispatch to allow multiple apps with a small number of 
rm's each. Views are handled by CAP::TT. Just the Model aspect is 
proving a little challenging. I'm trying to ensure that all database 
calls are handled outside the controllers, and to this end am using a 
module called WebApp::Model

#####################
package WebApp::Model;

BEGIN {
   setmoduledirs('/path/to/app'); # Module::Find
   useall WebApp::DB; # Rose::DB::Object classes
}

sub new {
     my $class = shift;
     bless { }, $class;
}

sub get_foo { }
sub update_bar { }
sub delete_baz { }
#####################

WebApp::Model initially loads all WebApp::DB::* (Rose::DB::Object) 
classes, and is made available to the WebApp object via cgiapp_init:

#################
sub cgiapp_init {
   my $c = shift;
   ..
   $c->param( 'model' => WebApp::Model->new );
}
################

Each controller run-mode uses $c->param( 'model') to get its data:

######################################
sub foo : Runmode { # CAP::AutoRunmode
   my $c = shift;
   ..
   my $data = $c->param('model')->get_foo;
}
######################################

This seems to work well, but the problem is that WebApp::Model is 
growing, as ever more (unrelated) db-related methods are added. Perhaps 
I could/should sub-class this one? Ideally I would move the 
WebApp::Model methods into their respective WebApp::DB class (eg 
get_foo() goes into WebApp::DB::Foo), but then I can't access it any 
longer from $c->param('model')->get_foo.

But the main question is whether this is the right approach to start 
with - stuffing WebApp::Model into the WebApp object and retrieving it 
in the run-modes via a param_name. Advantages include decoupling the 
model from the controllers - they don't know/care how get_foo() gets its 
data, and I can change the db-related stuff (eg RDBO <=> DBIC) without 
affecting the controllers. Disadvantage (so far) is lumping all methods 
into one (WebApp::Model) module. Comments & thoughts most welcome.
-- 
Richard Jones