features of how Catalyst works and shows how to get a simple application
up and running quickly. For an introduction (without code) to Catalyst
itself, and why you should be using it, see L<Catalyst::Manual::About>.
+For a systematic step-by-step introduction to writing an application
+with Catalyst, see L<Catalyst::Manual::Tutorial>.
=head2 What is Catalyst?
Catalyst is an elegant web application framework, extremely flexible yet
extremely simple. It's similar to Ruby on Rails, Spring (Java), and
-L<Maypole>, upon which it was originally based.
+L<Maypole>, upon which it was originally based. Its most important
+design philosphy is to provide easy access to all the tools you need to
+develop web applications, with few restrictions on how you need to use
+these tools. Under Catalyst, it is always possible to do things in a
+different way. However, this does mean that it is always possible to do
+things in a different way. Other web frameworks are simpler to use and
+easy to get up and running, but achieve this by locking the programmer
+into a single set of tools. Catalyst's emphasis on flexibility means
+that you have to think more to use it. We view this as a feature.
=head3 MVC
=item * B<Model>
Access and modify content (data). L<DBIx::Class>, L<Class::DBI>,
-L<Plucene>, L<Net::LDAP>...
+L<Xapian>, L<Net::LDAP>...
=item * B<View>
);
1;
+In older versions of Catalyst, the application class was where you put
+global actions. However, as of version 5.66, the recommended practice is
+to place such actions in a special Root controller (see L</Actions>,
+below), to avoid namespace collisions.
+
=over 4
=item * B<name>
$c->req->cookies->{sessionid};
$c->req->headers->content_type;
$c->req->base;
+ $c->req->uri_with( { page = $pager->next_page } );
=item * L<Catalyst::Response>
Note that the stash should be used only for passing data in an
individual request cycle; it gets cleared at a new request. If you need
-to maintain more persistent data, use a session.
+to maintain persistent data, use a session. See
+L<Catalyst::Plugin::Session> for a comprehensive set of
+Catalyst-friendly session-handling tools.
=head3 Actions
-
-
A Catalyst controller is defined by its actions. An action is a
subroutine with a special attribute. You've already seen some examples
of actions in this document. The URL (for example
=item * B<Application Wide Actions>
Actions which are called at the root level of the application
-(e.g. http:///localhost:3000/ ) go in MyApp::Controller::Root, like
+(e.g. http://localhost:3000/ ) go in MyApp::Controller::Root, like
this:
package MyApp::Controller::Root;
}
1;
-
=back
-For most applications, Catalyst requires you to define only one config
-parameter:
-
=head4 Action types
Catalyst supports several types of actions:
explanation of the pre-defined meaning of Catalyst component class
names.
+=item * B<Chained>
+
+Catalyst also provides a method to build and dispatch chains of actions,
+like
+
+ sub foo : Chained : CaptureArgs(1) {
+ my ( $self, $c, $arg ) = @_;
+ ...
+ }
+
+ sub bar : Chained('foo') : Args(1) {
+ my ( $self, $c, $arg ) = @_;
+ ...
+ }
+
+to handle a C</foo/*/bar/*> path. For extensive information about this
+dispatch type, please see L<Catalyst::DispatchType::Chained>.
+
=item * B<Private>
sub foo : Private { }
individual controllers.
If C<default> isn't acting how you would expect, look at using a
-L</Literal> C<Path> action (with an empty path string). The difference is
-that C<Path> takes arguments relative from the namespace and C<default>
-I<always> takes arguments relative from the root, regardless of what
-controller it's in.
+L</Literal> C<Path> action (with an empty path string). The difference
+is that C<Path> takes arguments relative from the namespace and
+C<default> I<always> takes arguments relative from the root, regardless
+of what controller it's in. Indeed, this is now the recommended way of
+handling default situations; the C<default> private controller should
+be considered deprecated.
=item * B<index : Private>
$c->res->body( $c->stash->{message} );
}
-A C<forward> does not create a new request, so your request
-object (C<$c-E<gt>req>) will remain unchanged. This is a
-key difference between using C<forward> and issuing a
-redirect.
+A C<forward> does not create a new request, so your request object
+(C<$c-E<gt>req>) will remain unchanged. This is a key difference between
+using C<forward> and issuing a redirect.
You can pass new arguments to a C<forward> by adding them
in an anonymous array. In this case C<$c-E<gt>req-E<gt>args>
Controllers. Catalyst automatically discovers and instantiates them
when you call C<setup> in the main application. All you need to do is
put them in directories named for each Component type. Notice that you
-can use some very terse aliases for each one.
+can use a terse alias for each one.
=over 4
=back
+In older versions of Catalyst, the recommended practice (and the one
+automatically created by helper scripts) was to name the directories
+C<M/>, C<V/>, and C<C/>. Though these still work, we now recommend
+the use of the full names.
+
=head4 Views
To show how to define views, we'll use an already-existing base class for the
}
You normally render templates at the end of a request, so it's a perfect
-use for the global C<end> action.
+use for the global C<end> action. (In practice, however, you would use a
+default C<end> action as supplied by L<Catalyst::Action::RenderView>.)
Also, be sure to put the template under the directory specified in
-C<$c-E<gt>config-E<gt>{root}>, or you'll be forced to look at our
-eyecandy debug screen. ;)
+C<$c-E<gt>config-E<gt>{root}>, or you'll end up looking at the debug
+screen.
=head4 Models
$c->stash->{template} = 'list.tt';
- use Some::Outside::DBIC::Module;
- my @records = Some::Outside::DBIC::Module->search({
- artist => 'sri',
+ use Some::Outside::Database::Module;
+ my @records = Some::Outside::Database::Module->search({
+ artist => 'Led Zeppelin',
});
$c->stash->{records} = \@records;
=back
-From a style perspective usually it's bad to make your model "too smart" about
-things - it should worry about business logic and leave the integration details
-to the controllers. If, however, you find that it does not make sense at all to
-use an auxillary controller around the model, and the model's need to access
-C<$c> cannot be sidestepped, there exists a power tool called C<ACCEPT_CONTEXT>.
+From a style perspective usually it's bad to make your model "too smart"
+about things - it should worry about business logic and leave the
+integration details to the controllers. If, however, you find that it
+does not make sense at all to use an auxillary controller around the
+model, and the model's need to access C<$c> cannot be sidestepped, there
+exists a power tool called C<ACCEPT_CONTEXT>.
#### editor note: this part is "generic" - it also applies to views and
#### controllers.
=head3 ACCEPT_CONTEXT
-Whenever you call $c->component("Foo") you get back an object - the instance of
-the model. If the component supports the C<ACCEPT_CONTEXT> method instead of
-returning the model itself, the return value of
-C<< $model->ACCEPT_CONTEXT( $c ) >> will be used.
+Whenever you call $c->component("Foo") you get back an object - the
+instance of the model. If the component supports the C<ACCEPT_CONTEXT>
+method instead of returning the model itself, the return value of C<<
+$model->ACCEPT_CONTEXT( $c ) >> will be used.
This means that whenever your model/view/controller needs to talk to C<$c> it
gets a chance to do this when it's needed.
with the context object set, or it will return a thin wrapper that contains
C<$c> and delegates to the per-application model object.
-A typicall C<ACCEPT_CONTEXT> method could look like this:
+A typical C<ACCEPT_CONTEXT> method could look like this:
sub ACCEPT_CONTEXT {
my ( $self, $c, @extra_arguments ) = @_;
Add a field to C<$c>, like C<my_model_instance>. Then write your
C<ACCEPT_CONTEXT> method to look like this:
- sub ACCEPT_CONTEXT {
- my ( $self, $c ) = @_;
-
- if ( my $per_request = $c->my_model_instance ) {
- return $per_request;
- } else {
- my $new_instance = bless { %$self, c => $c }, ref($self);
- Scalar::Util::weaken($new_instance->{c}); # or we have a circular reference
- $c->my_model_instance( $new_instance );
- return $new_instance;
- }
- }
+ sub ACCEPT_CONTEXT {
+ my ( $self, $c ) = @_;
+ if ( my $per_request = $c->my_model_instance ) {
+ return $per_request;
+ } else {
+ my $new_instance = bless { %$self, c => $c }, ref($self);
+ Scalar::Util::weaken($new_instance->{c}); # or we have a circular reference
+ $c->my_model_instance( $new_instance );
+ return $new_instance;
+ }
+ }
=head3 Testing
-Catalyst has a built-in http server for testing! (Later, you can easily
-use a more powerful server, e.g. Apache/mod_perl, in a production
-environment.)
+Catalyst has a built-in http server for testing. (Later, you can easily
+use a more powerful server, e.g. Apache/mod_perl or FastCGI, in a
+production environment.)
Start your application on the command line...
projects / catagits/Catalyst-Runtime.git / blobdiff