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-=head1 Maypole Model Classes
-
-=head2 Class::DBI
-
-=head2 Maypole::Model::CDBI
-
-Maypole model classes are pretty evil. The very first thing a Maypole
-model class will do in a Maypole application is to cause a load of
-table-based classes to come into being, and then assimilate them.
-
-What I mean by this is that when you set up a Maypole application, in
-your driver class, you'll say something like this:
-
- BeerDB->setup("dbi:mysql:beerdb");
-
-C<setup> is a Maypole method, and it hands its parameter to the model
-class. In our case, the model class is a DBI connect string, because
-that's what C<Maypole::Model::CDBI>, the C<Class::DBI>-based model
-expects. C<Maypole::Model::CDBI> has a method called C<setup_database>
-that creates all the C<Class::DBI> table classes after connecting to the
-database with that connect string. It does this by using
-C<Class::DBI::Loader>, a utility module which asks a database
-about its schema and sets up classes such as C<BeerDB::Beer> to inherit
-from C<Class::DBI>. This is just doing automatically what we did
-manually in our examples above.
-
-Now it gets interesting. The names of these classes are stashed away in
-the application's configuration, and then Maypole forcibly has these
-classes inherit from the model class. Our C<BeerDB::Beer> now inherits
-both from C<Class::DBI> and C<Maypole::Model::CDBI>.
-
-This is useful for two reasons. The first reason is that
-C<Maypole::Model::CDBI> is stuffed full of C<Class::DBI> goodies that
-make writing Maypole applications a lot easier:
-
- package Maypole::Model::CDBI;
- use base qw(Maypole::Model::Base Class::DBI);
- use Class::DBI::AsForm;
- use Class::DBI::FromCGI;
- use Class::DBI::Loader;
- use Class::DBI::AbstractSearch;
- use Class::DBI::Plugin::RetrieveAll;
- use Class::DBI::Pager;
-
-We'll meet most of these goodies in L<StandardTemplates.pod>, where we
-explain how C<Maypole::Model::CDBI> works.
-
-The second reason why we want our table classes to inherit from
-C<Maypole::Model::CDBI> is because C<CDBI> provides a useful set of
-default actions. So what's an action, and why are they useful?
-
-=head2 Extending a model class with actions
-
-Maypole operates primarily by turning URLs into method calls on a model
-class. All that the model stage of Maypole's operation does, when it
-comes down to it, is maintain a mapping of tables to classes, and
-despatch a HTTP request to a method call on the relevant table class. This
-means that if you request a URL such as
-
- http://localhost/beerdb/brewery/delete/20
-
-Maypole's first stage of operation is to turn that into
-C<BeerDB::Brewery-E<gt>delete(20)>. Now, it's slightly more complex than
-that. Firstly because it doesn't actually pass the parameter C<20>, but
-it passes an object representing row 20 in the database, but we can
-gloss over that for the second. No, the real issue is that Maypole does
-not allow you to call any method in the table class; that would be
-somewhat insecure.
-
-Instead, Maypole makes a distinction between the kind of methods that
-only the class itself and other Perl code can call, and the kind of
-methods that anyone can call from a URL. This latter set of methods are
-called B<exported> methods, and exporting is done with by means of Perl
-attributes. You define a method to be exported like so:
-
- sub drink :Exported {
-
-This will allow the user to access C</beerdb/beer/drink> over the web.
-An exported method accompanied with a template to render its output is
-sometimes called an B<action>.
-
-Maypole model classes like C<Maypole::Model::CDBI> come with a
-relatively handy set of actions which are all you need to set up a CRUD
-database front-end: viewing a row in a database, editing it, adding a
-new one, deleting, and so on. The most important thing about Maypole,
-though, is that it doesn't stop there. You can add your own.
-
-For instance, in our beer database application, we could create a
-C<BeerDB::Beer> package, and put some additional actions in there.
-
- package BeerDB::Beer;
- sub top_five :Exported {
- my ($class, $r) = @_;
- $r->{objects} = [ ($r->retrieve_all_sorted_by("score"))[-5..-1] ];
- }
-
-Our action is called as a class method with the Maypole request object.
-It uses the C<Class::DBI::Plugin::RetrieveAll> module's
-C<retrieve_all_sorted_by> mixin to get the top five scoring beers, and
-puts these in the C<objects> slot of the request of object. Next, the
-view class will come along and process the C<top_five> template with
-these five beers.
-
-We'll look more at how to put together actions in the
-L<StandardTemplates.pod> chapter and our case studies.
-
-=head2 What Maypole wants from a model
-
-=head2 Building your own model class
projects / maypole.git / blobdiff