=head1 DESCRIPTION
-This is a brief overview of why and how to use Catalyst. It explains how Catalyst works and shows how to quickly get a simple application up and running.
+This is a brief overview of why and how to use Catalyst. It explains how Catalyst works and shows how to get a simple application up and running quickly.
=head2 What is Catalyst?
=head3 MVC
-Catalyst follows the Model-View-Controller (MVC) design pattern, allowing you to easily separate concerns, like content, presentation and flow control, into separate modules. This separation allows you to modify code that handles one concern without affecting code that handles the others. Catalyst promotes re-use of existing Perl modules that already handle common web application concerns well.
+Catalyst follows the Model-View-Controller (MVC) design pattern, allowing you to easily separate concerns, like content, presentation, and flow control, into separate modules. This separation allows you to modify code that handles one concern without affecting code that handles the others. Catalyst promotes the re-use of existing Perl modules that already handle common web application concerns well.
-Here's how the M, V and C map to those concerns, with examples of well-known Perl modules you may want to use for each.
+Here's how the M, V, and C map to those concerns, with examples of well-known Perl modules you may want to use for each.
=over 4
=item * B<View>
-Present content to the user. L<Template Toolkit|Template>, L<Mason|HTML::Mason>...
+Present content to the user. L<Template Toolkit|Template>, L<Mason|HTML::Mason>, L<HTML::Template>...
=item * B<Controller>
=back
-If you're unfamiliar with MVC and design patterns, you may want to check out the original book on the subject, I<Design Patterns>, by Gamma, Helm, Johson and Vlissides, a.k.a. the Gang of Four (GoF). Or just search the web. Many, many web application frameworks follow MVC, including all those listed above.
+If you're unfamiliar with MVC and design patterns, you may want to check out the original book on the subject, I<Design Patterns>, by Gamma, Helm, Johson and Vlissides, also known as the Gang of Four (GoF). You can also just google it. Many, many web application frameworks are based on MVC, including all those listed above.
=head3 Flexibility
-Catalyst is much more flexible than many other frameworks.
+Catalyst is much more flexible than many other frameworks. We'll talk more about this later, but rest assured you can use your favorite Perl modules with Catalyst.
=over 4
-=item * B<Multiple Models, Views and Controllers>
+=item * B<Multiple Models, Views, and Controllers>
-To build a Catalyst application, you handle each type of concern inside special modules called L</Components>. Often this code will be very simple, just calling out to Perl modules like those listed above under L</MVC>. Catalyst is very flexible about these Components. Use as many Models, Views and Controllers as you like, using as many different Perl modules as you like, all in the same application. Want to manipulate multiple databases, plus retrieve some data via LDAP? No problem. Want to present data from the same Model using L<Template Toolkit|Template> and L<PDF::Template>? Easy.
+To build a Catalyst application, you handle each type of concern inside special modules called L</Components>. Often this code will be very simple, just calling out to Perl modules like those listed above under L</MVC>. Catalyst handles these components in a very flexible way. Use as many Models, Views, and Controllers as you like, using as many different Perl modules as you like, all in the same application. Want to manipulate multiple databases, and retrieve some data via LDAP? No problem. Want to present data from the same Model using L<Template Toolkit|Template> and L<PDF::Template>? Easy.
-=item * B<Re-Useable Components>
+=item * B<Reuseable Components>
-Not only does Catalyst promote the re-use of already-existing Perl modules, it also allows you to re-use your Catalyst components in multiple Catalyst applications.
+Not only does Catalyst promote the re-use of already existing Perl modules, it also allows you to re-use your Catalyst components in multiple Catalyst applications.
=item * B<Unrestrained URL-to-Action Dispatching>
-Catalyst allows you to dispatch any URLs to any application L<Actions>, even via regular expressions! Unlike some other frameworks, it doesn't require mod_rewrite or class and method names in URLs.
+Catalyst allows you to dispatch any URLs to any application L<Actions>, even through regular expressions! Unlike most other frameworks, it doesn't require mod_rewrite or class and method names in URLs.
With Catalyst you register your actions and address them directly. For example:
- MyApp->action( 'hello' => sub {
+ sub hello : Global {
my ( $self, $context ) = @_;
$context->response->output('Hello World!');
- });
+ }
Now http://localhost:3000/hello prints "Hello World!".
The best part is that Catalyst implements all this flexibility in a very simple way.
+=over 4
+
=item * B<Building Block Interface>
-Components interoperate very smoothly. For example, Catalyst automatically makes a L<Context> object available in every component. Via the context, you can access the request object, share data between components, and control the flow of your application. Building a Catalyst application feels a lot like snapping together toy building blocks, and everything just works.
+Components interoperate very smoothly. For example, Catalyst automatically makes a L<Context> object available to every component. Via the context, you can access the request object, share data between components, and control the flow of your application. Building a Catalyst application feels a lot like snapping together toy building blocks, and everything just works.
=item * B<Component Auto-Discovery>
See L<Catalyst::Model::CDBI> for L<Class::DBI>, or L<Catalyst::View::TT> for L<Template Toolkit|Template>. You can even get an instant web database front end with L<Catalyst::Model::CDBI::CRUD>.
-=item * B<Builtin Test Framework>
+=item * B<Built-in Test Framework>
-Catalyst comes with a builtin, lightweight http server and test framework, making it easy to test applications from the command line.
+Catalyst comes with a built-in, lightweight http server and test framework, making it easy to test applications from the command line.
=item * B<Helper Scripts>
Catalyst provides helper scripts to quickly generate running starter code for components and unit tests.
+=back
+
=head2 Quickstart
Here's how to install Catalyst and get a simple application up and running, using the helper scripts described above.
=head3 Setup
- $ catalyst.pl My::App
- $ cd My-App
- $ script/create.pl controller My::Controller
+ $ catalyst.pl MyApp
+ # output omitted
+ $ cd MyApp
+ $ script/myapp_create.pl controller Library::Login
=head3 Run
- $ script/server.pl
+ $ script/myapp_server.pl
Now visit these locations with your favorite browser or user agent to see Catalyst in action:
=item http://localhost:3000/
-=item http://localhost:3000/my_controller/
+=item http://localhost:3000/library/login/
=back
=head3 Application Class
-In addition to the Model, View and Controller components, there's a single class that represents your application itself. This is where you configure your application, load plugins, define application-wide actions and extend Catalyst.
+In addition to the Model, View, and Controller components, there's a single class that represents your application itself. This is where you configure your application, load plugins, define application-wide actions, and extend Catalyst.
package MyApp;
name => 'My Application',
root => '/home/joeuser/myapp/root',
- # You can put whatever you want in here:
- # my_param_name => $my_param_value,
+ # You can put anything else you want in here:
+ my_configuration_variable => 'something',
);
- MyApp->action( '!default' => sub {
+ sub default : Private {
my ( $self, $context ) = @_;
$context->response->output('Catalyst rockz!');
- });
+ }
1;
=item * B<root>
-Path to additional files like templates, images or other static data.
+Path to additional files such as templates, images, or other static data.
=back
=head3 Context
-Catalyst automatically blesses a Context object into your application class and makes it available everywhere in your application. Use the Context to directly interact with Catalyst and glue your L<Components> together.
+Catalyst automatically blesses a Context object into your application class and makes it available everywhere in your application. Use the Context to directly interact with Catalyst and glue your L<Components> together. For example, if you need to use the Context from within a Template Toolkit template, it's already there:
+
+ <h1>Welcome to [% c.config.name %]!</h1>
As illustrated earlier in our URL-to-Action dispatching example, the Context is always the second method parameter, behind the Component object reference or class name itself. Previously we called it C<$context> for clarity, but most Catalyst developers just call it C<$c>:
- MyApp->action( 'hello' => sub {
+ sub hello : Global {
my ( $self, $c ) = @_;
$c->res->output('Hello World!');
- });
+ }
The Context contains several important objects:
$c->request
$c->req # alias
-The request contains all kinds of request-specific information, like query parameters, cookies, uploads, headers and more.
+The request object contains all kinds of request-specific information, like query parameters, cookies, uploads, headers, and more.
$c->req->params->{foo};
$c->req->cookies->{sessionid};
The last of these, the stash, is a universal hash for sharing data among application components. For an example, we return to our 'hello' action:
- MyApp->action(
-
- 'hello' => sub {
- my ( $self, $c ) = @_;
- $c->stash->{message} = 'Hello World!';
- $c->forward('!show-message');
- },
+ sub hello : Global {
+ my ( $self, $c ) = @_;
+ $c->stash->{message} = 'Hello World!';
+ $c->forward('show_message');
+ }
- '!show-message' => sub {
- my ( $self, $c ) = @_;
- $c->res->output( $c->stash->{message} );
- },
+ sub show_message : Private {
+ my ( $self, $c ) = @_;
+ $c->res->output( $c->stash->{message} );
+ }
- );
+Note that the stash should be used only for passing data in an individual request cycle; it gets cleared at a new request. If you need to maintain more persistent data, use a session.
=head3 Actions
-To define a Catalyst action, register it into your application with the C<action> method. C<action> accepts a key-value pair, where the key represents one or more URLs or application states and the value is a code reference, the action to execute in reponse to the URL(s) or application state(s).
+A Catalyst controller is defined by its actions. An action is a sub with
+a special attribute. You've already seen some examples of actions in
+this document.
-Catalyst supports several ways to define Actions:
+Catalyst supports several types of actions:
=over 4
=item * B<Literal>
- MyApp->action( 'foo/bar' => sub { } );
+ sub bar : Path('foo/bar') { }
Matches only http://localhost:3000/foo/bar.
=item * B<Regex>
- MyApp->action( '/^foo(\d+)/bar(\d+)$/' => sub { } );
+ sub bar : Regex('^item(\d+)/order(\d+)$') { }
+
+Matches any URL that matches the pattern in the action key, e.g. http://localhost:3000/item23/order42. The '' around the regexp is optional, but perltidy likes it. :)
-Matches any URL that matches the pattern in the action key, e.g. http://localhost:3000/foo23/bar42. The pattern must be enclosed with forward slashes, i.e. '/$pattern/'.
+Regex matches act globally, i.e. without reference to the namespace from which it is called, so that a C<bar> method in the C<MyApp::Controller::Catalog::Order::Process> namespace won't match any form of C<bar>, C<Catalog>, C<Order>, or C<Process> unless you explicitly put this in the regex.
-If you use capturing parantheses to extract values within the matching URL (23, 42 in the above example), those values are available in the $c->req->snippets array. If you want to pass arguments at the end of your URL, you must use regex action keys. See L</URL Argument Handling> below.
+If you use capturing parentheses to extract values within the matching URL (23, 42 in the above example), those values are available in the $c->req->snippets array. If you want to pass arguments at the end of your URL, you must use regex action keys. See L</URL Argument Handling> below.
+
+=item * B<Top-level>
+
+ package MyApp;
+ sub foo : Global { }
+
+Matches http://localhost:3000/foo. The function name is mapped directly
+to the application base.
=item * B<Namespace-Prefixed>
- package MyApp::Controller::My::Controller;
- MyApp->action( '?foo' => sub { } );
+ package MyApp::C::My::Controller;
+ sub foo : Local { }
-Matches http://localhost:3000/my_controller/foo. The action key must be prefixed with '?'.
+Matches http://localhost:3000/my/controller/foo.
-Prefixing the action key with '?' indicates that the matching URL must be prefixed with a modified form of the component's class (package) name. This modified class name excludes the parts that have a pre-defined meaning in Catalyst ("MyApp::Controller" in the above example), replaces "::" with "_" and converts the name to lower case. See L</Components> for a full explanation of the pre-defined meaning of Catalyst component class names.
+This action type indicates that the matching URL must be prefixed with a modified form of the component's class (package) name. This modified class name excludes the parts that have a pre-defined meaning in Catalyst ("MyApp::C" in the above example), replaces "::" with "/", and converts the name to lower case. See L</Components> for a full explanation of the pre-defined meaning of Catalyst component class names.
=item * B<Private>
- MyApp->action( '!foo' => sub { } );
+ sub foo : Private { }
Matches no URL, and cannot be executed by requesting a URL that corresponds to the action key. Private actions can be executed only inside a Catalyst application, by calling the C<forward> method:
- $c->forward('!foo');
+ $c->forward('foo');
-See L</Flow Control> for a full explanation of C<forward>.
+See L</Flow Control> for a full explanation of C<forward>. Note that, as discussed there, when forwarding from another component, you must use the absolute path to the method, so that a private C<bar> method in your C<MyApp::Controller::Catalog::Order::Process> controller must, if called from elsewhere, be reach with C<$c-E<gt>forward('/catalog/order/process/bar')>.
=back
-=head4 Builtin Private Actions
+B<Note:> After seeing these examples, you probably wonder what the point
+is of defining names for regex and path actions. Actually, every public
+action is also a private one, so you have one unified way of addressing
+components in your C<forward>s.
-In response to specific application states, Catalyst will automatically call these built in private actions:
+=head4 Built-in Private Actions
+
+In response to specific application states, Catalyst will automatically call these built-in private actions:
=over 4
-=item * B<!default>
+=item * B<default : Private>
Called when no other action matches.
-=item * B<!begin>
+=item * B<begin : Private>
Called at the beginning of a request, before any matching actions are called.
-=item * B<!end>
+=item * B<end : Private>
=back
Called at the end of a request, after all matching actions are called.
-=head4 B<Namespace-Prefixed Private Actions>
+=head4 B<Built-in actions in controllers/autochaining>
+
+ Package MyApp::C::Foo;
+ sub begin : Private { }
+ sub default : Private { }
- MyApp->action( '!?foo' => sub { } );
- MyApp->action( '!?default' => sub { } );
+You can define the Built-in Private Actions within your controllers as
+well. The actions will override the ones in lower level controllers or
+your global application.
+
+In addition to the normal built-ins, you have a special action for
+making inheritance chains, 'auto'. These will be run after C<begin>,
+but before your action is processed.
+
+=over 4
+
+=item for a request for /foo/foo
+
+ MyApp::begin
+ MyApp::auto
+ MyApp::C::Foo::default
+ MyApp::end
+
+=item for a request for /foo/bar/foo
+
+ MyApp::C::Foo::Bar::begin
+ MyApp::auto
+ MyApp::C::Foo::auto
+ MyApp::C::Foo::Bar::default
+ MyApp::C::Foo::Bar::end
+
+=back
+
+Also, if you need to break out of the chain in one of your auto
+actions, you can return 0, if so, your action will not be processed,
+but the end will, so for the request above, if the first auto returns
+false, it would look like this:
+
+=over 4
+
+=item for a request for /foo/bar/foo where auto returns false
+
+ MyApp::C::Foo::Bar::begin
+ MyApp::auto
+ MyApp::C::Foo::Bar::end
+
+=back
+
+B<Note:> auto actions have to return a true value to continue
+processing! You can also die in the autochain action, in that case, the
+request will go straight to the finalize stage, without processing
+further actions.
-The leading '!?' indicates that these are namespace-prefixed private actions. These override any application-wide private actions with the same names, and can be called only from within the namespace in which they are defined. Any private action can be namespace-prefixed, including the builtins. One use for this might be to give a Controller its own !?default, !?begin and !?end.
=head4 B<URL Argument Handling>
If you want to pass variable arguments at the end of a URL, you must use regex actions keys with '^' and '$' anchors, and the arguments must be separated with forward slashes (/) in the URL. For example, suppose you want to handle /foo/$bar/$baz, where $bar and $baz may vary:
- MyApp->action( '/^foo$/' => sub { my ($self, $context, $bar, $baz) = @_; } );
+ sub foo : Regex('^foo$') { my ($self, $context, $bar, $baz) = @_; }
But what if you also defined actions for /foo/boo and /foo/boo/hoo ?
- MyApp->action( '/foo/boo' => sub { .. } );
- MyApp->action( '/foo/boo/hoo' => sub { .. } );
+ sub boo : Path('foo/boo') { .. }
+ sub hoo : Path('foo/boo/hoo') { .. }
Catalyst matches actions in most specific to least specific order:
/foo/boo
/foo # might be /foo/bar/baz
-So Catalyst would never mistakenly dispatch the first two URLs to the '/^foo$/' action.
+So Catalyst would never mistakenly dispatch the first two URLs to the '^foo$' action.
=head3 Flow Control
-Control the application flow with the C<forward> method, which accepts the key of an action to execute.
+You control the application flow with the C<forward> method, which accepts the key of an action to execute.
- MyApp->action(
-
- 'hello' => sub {
- my ( $self, $c ) = @_;
- $c->stash->{message} = 'Hello World!';
- $c->forward('!check-message');
- },
+ sub hello : Global {
+ my ( $self, $c ) = @_;
+ $c->stash->{message} = 'Hello World!';
+ $c->forward('check_message');
+ }
- '!check-message' => sub {
- my ( $self, $c ) = @_;
- return unless $c->stash->{message};
- $c->forward('!show-message');
- },
+ sub check_message : Private {
+ my ( $self, $c ) = @_;
+ return unless $c->stash->{message};
+ $c->forward('show_message');
+ }
- '!show-message' => sub {
- my ( $self, $c ) = @_;
- $c->res->output( $c->stash->{message} );
- },
+ sub show_message : Private {
+ my ( $self, $c ) = @_;
+ $c->res->output( $c->stash->{message} );
+ }
+
+As you can see from these examples, you can just use the method name as long as you are referring to methods in the same controller. If you want to forward to a method in another controller, or the main application, you will have to refer to the method by absolute path.
- );
+ $c->forward('/my/controller/action');
+ $c->forward('/default');
You can also forward to classes and methods.
- MyApp->action(
-
- 'hello' => sub {
- my ( $self, $c ) = @_;
- $c->forward(qw/MyApp::M::Hello say_hello/);
- },
-
- 'bye' => sub {
- my ( $self, $c ) = @_;
- $c->forward('MyApp::M::Hello');
- },
+ sub hello : Global {
+ my ( $self, $c ) = @_;
+ $c->forward(qw/MyApp::M::Hello say_hello/);
+ }
- );
+ sub bye : Global {
+ my ( $self, $c ) = @_;
+ $c->forward('MyApp::M::Hello');
+ }
package MyApp::M::Hello;
$c->res->output('Goodbye World!');
}
-Note that C<forward> returns after processing.
+Note that C<forward> returns to the calling action and continues processing after the action finishes.
Catalyst will automatically try to call process() if you omit the method.
=head3 Components
-Again, Catalyst has an uncommonly flexible component system. You can define as many L<Models>, L<Views> and L<Controllers> as you like.
+Catalyst has an uncommonly flexible component system. You can define as many L<Models>, L<Views>, and L<Controllers> as you like.
All components must inherit from L<Catalyst::Base>, which provides a simple class structure and some common class methods like C<config> and C<new> (constructor).
- package MyApp::Controller::MyController;
+ package MyApp::C::Catalog;
use strict;
use base 'Catalyst::Base';
1;
-You don't have to C<use> or otherwise register Models, Views and Controllers. Catalyst automatically discovers and instantiates them, at startup. 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.
+You don't have to C<use> or otherwise register Models, Views, and 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.
=over 4
1;
-This gives us a process() method and we can now just do $c->forward('MyApp::V::TT') to render our templates. The base class makes process() implicit, so we don't have to say C<$c-E<gt>forward(qw/MyApp::V::TT process/)>.
+(You can also generate this automatically by using the helper script:
- MyApp->action(
+ script/myapp_create.pl view TT TT
- 'hello' => sub {
- my ( $self, $c ) = @_;
- $c->stash->{template} = 'hello.tt';
- },
+where the first C<TT> tells the script to create a Template Toolkit
+view, and the second tells the script that its name should be C<TT>.)
- '!end' => sub {
- my ( $self, $c ) = @_;
- $c->forward('MyApp::View::TT');
- },
+This gives us a process() method and we can now just do $c->forward('MyApp::V::TT') to render our templates. The base class makes process() implicit, so we don't have to say C<$c-E<gt>forward(qw/MyApp::V::TT process/)>.
- );
+ sub hello : Global {
+ my ( $self, $c ) = @_;
+ $c->stash->{template} = 'hello.tt';
+ }
-You normally render templates at the end of a request, so it's a perfect use for the !end action.
+ sub end : Private {
+ my ( $self, $c ) = @_;
+ $c->forward('MyApp::V::TT');
+ }
+
+You normally render templates at the end of a request, so it's a perfect use for the global C<end> action.
-Also, be sure to put the template under the directory specified in C<$c-E<gt>config->{root}>, or you'll be forced to look at our eyecandy debug screen. ;)
+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. ;)
=head4 Models
name => 'My Application',
root => '/home/joeuser/myapp/root'
);
+
+ __PACKAGE__->setup;
- __PACKAGE__->action(
-
- '!end' => sub {
- my ( $self, $c ) = @_;
- $c->stash->{template} ||= 'index.tt';
- $c->forward('MyApp::V::TT');
- },
-
- 'view' => sub {
- my ( $self, $c, $id ) = @_;
- $c->stash->{item} = MyApp::M::CDBI::Foo->retrieve($id);
- }
+ sub end : Private {
+ my ( $self, $c ) = @_;
+ $c->stash->{template} ||= 'index.tt';
+ $c->forward('MyApp::V::TT');
+ }
- );
+ sub view : Global {
+ my ( $self, $c, $id ) = @_;
+ $c->stash->{item} = MyApp::M::CDBI::Foo->retrieve($id);
+ }
1;
=head4 Controllers
-Multiple Controllers are a good way to separate logical domains of your application.
+Multiple controllers are a good way to separate logical domains of your application.
package MyApp::C::Login;
- MyApp->action(
- '?sign-in' => sub { },
- '?new-password' => sub { },
- '?sign-out' => sub { },
- );
+ sign-in : Local { }
+ new-password : Local { }
+ sign-out : Local { }
package MyApp::C::Catalog;
- MyApp->action(
- '?view' => sub { },
- '?list' => sub { },
- );
+ sub view : Local { }
+ sub list : Local { }
package MyApp::C::Cart;
- MyApp->action(
- '?add' => sub { },
- '?update' => sub { },
- '?order' => sub { },
- );
+ sub add : Local { }
+ sub update : Local { }
+ sub order : Local { }
=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, in a production environment.)
Start your application on the command line...
- perl bin/server
-
-or
-
- perl -I/home/joeuser/myapp/lib -MCatalyst::Test=MyApp -e1 3000
+ script/myapp_server.pl
...then visit http://localhost:3000/ in a browser to view the output.
You can also do it all from the command line:
- perl bin/test http://localhost/
+ script/myapp_test.pl http://localhost/
-or
+Have fun!
- perl -I/home/joeuser/myapp/lib -MCatalyst::Test=MyApp -e1 http://localhost/
+=head1 SUPPORT
-Have fun!
+IRC:
+
+ Join #catalyst on irc.perl.org.
+
+Mailing-lists:
+
+ http://lists.rawmode.org/mailman/listinfo/catalyst
+ http://lists.rawmode.org/mailman/listinfo/catalyst-dev
=head1 AUTHOR
-Sebastian Riedel, C<sri@oook.de> and David Naughton, C<naughton@umn.edu>
+Sebastian Riedel, C<sri@oook.de>
+David Naughton, C<naughton@umn.edu>
+Marcus Ramberg, C<mramberg@cpan.org>
+Jesse Sheidlower, C<jester@panix.com>
=head1 COPYRIGHT
projects / catagits/Catalyst-Runtime.git / blobdiff