path: root/posts/2009-05-18-a-simple-feed-aggregator-with-modern-perl-part-4.1.org

You can thanks [[http://github.com/bobtfish][bobtfish]] for being such a
pedantic guy, 'cause now you will have a better chained examples. He
forked my repository from GitHub and fix some code that I'll explain
here.

*** lib/MyFeedReader.pm

#+BEGIN_SRC perl
     package MyFeedReader;
    +use Moose;
    +use namespace::autoclean;

    -use strict;
    -use warnings;
    -
    -use Catalyst::Runtime '5.70';
    +use Catalyst::Runtime '5.80';

    -use parent qw/Catalyst/;
    +extends 'Catalyst';
#+END_SRC

You can see that he use [[http://search.cpan.org/perldoc?Moose][Moose]],
so we can remove

#+BEGIN_SRC perl
    use strict;
    use warnings;
#+END_SRC

and have a more elegant way to inherit from
[[http://search.cpan.org/perldoc?Catalyst][Catalyst]] with

#+BEGIN_SRC perl
    extends 'Catalyst';
#+END_SRC

instead of

#+BEGIN_SRC perl
    use parent qw/Catalyst/;
#+END_SRC

He also have updated the *Catalyst::Runtime* version, and added
*namespace::autoclean*. The purpose of this module is to keep imported
methods out of you namespace. Take a look at the
"documentation":http://search.cpan.org/perldoc?namespace::autoclean,
it's easy to understand how and why it's usefull.

*** lib/MyFeedReader/Controller/Root.pm

#+BEGIN_SRC perl
    -use strict;
    -use warnings;
    -use parent 'Catalyst::Controller';
    +use Moose;
    +use namespace::autoclean;
    +BEGIN { extends 'Catalyst::Controller' }

    -sub index :Path :Args(0) {
    +sub root : Chained('/') PathPart() CaptureArgs(0) {}
    +
    +sub index : Chained('root') PathPart('') Args(0) {
            my ( $self, $c ) = @_;

            # Hello World
            $c->response->body( $c->welcome_message );
        }

    -sub default :Path {
    +sub default : Private {
            my ( $self, $c ) = @_;
            $c->response->body( 'Page not found' );
            $c->response->status(404);
#+END_SRC

A new method, =root=, that will be the root path for our application.
All our methods will be chained from this action. If start you catalyst
server and go to *http://localhost:3000/* you will be served with the
Catalyst's welcome message as before.

*** lib/MyFeedReader/Controller/Entry.pm

#+BEGIN_SRC perl
    -use warnings;
    +use Moose;
     use MyAggregator::Entry;
    -use parent 'Catalyst::Controller';
    -
    -__PACKAGE__->config->{namespace} = 'entry';
    +use namespace::autoclean;
    +BEGIN { extends 'Catalyst::Controller'; }

    -sub view : Chained('/') : PathPart('entry') : Args(1) {
    +sub view : Chained('/root') : PathPart('entry') : Args(1) {
         my ( $self, $c, $id ) = @_;

         $c->stash->{entry} = $c->model('KiokuDB')->lookup($id);
     }

    -1;
    -
    +__PACKAGE__->meta->make_immutable;
#+END_SRC

We extends the *Catalyst::Controller* in a Moose way, and the
=make_immutable= instruction is a Moose recommanded best practice (you
can alsa add =no Moose= after the make\_immutable).

*** lib/MyFeedreader/Controller/Feed.pm

#+BEGIN_SRC perl
    +use Moose;
    +use namespace::autoclean;
    +BEGIN { extends 'Catalyst::Controller' }

    -use strict;
    -use warnings;
    -use parent 'Catalyst::Controller';
    +sub feed : Chained('/root') PathPart('feed') CaptureArgs(0) {}

    -__PACKAGE__->config->{namespace} = 'feed';
    -
    -sub index : Path : Args(0) {
    +sub index : Chained('feed') PathPart('') Args(0) {
         my ( $self, $c ) = @_;

         $c->stash->{feeds}
             = [ $c->model('MyModel')->resultset('Feed')->search() ];
     }

    -sub view : Chained('/') : PathPart('feed/view') : Args(1) {
    +sub view : Chained('feed') : PathPart('view') : Args(1) {
         my ( $self, $c, $id ) = @_;

         $c->stash->{feed}
             = $c->model('MyModel')->resultset('Feed')->find($id);
     }

    -1;
    +__PACKAGE__->meta->make_immutable;
#+END_SRC

We got =feed= which is chained to root. =index= is chained to feed, and
take no arguments. This method display the list of our feeds. And we got
the =view= method, chained to feed too, but with one argument, that
display the content of an entry.

If you start the application, you will see the following routes:

#+BEGIN_EXAMPLE
    .-------------------------------------+--------------------------------------.
    | Path Spec                           | Private                              |
    +-------------------------------------+--------------------------------------+
    | /root/entry/*                       | /root (0)                            |
    |                                     | => /entry/view                       |
    | /root/feed                          | /root (0)                            |
    |                                     | -> /feed/feed (0)                    |
    |                                     | => /feed/index                       |
    | /root/feed/view/*                   | /root (0)                            |
    |                                     | -> /feed/feed (0)                    |
    |                                     | => /feed/view                        |
    | /root                               | /root (0)                            |
    |                                     | => /index                            |
    '-------------------------------------+--------------------------------------'
#+END_EXAMPLE

I hope you got a better idea about chained action in catalyst now. And
again, thanks to bobtfish for the code.