inlined ConfigLoader and ConfigLoader::YAML
[catagits/Catalyst-Runtime.git] / lib / Catalyst / Manual / Intro.pod
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fc7ec1d9 1=head1 NAME
2
3Catalyst::Manual::Intro - Introduction to Catalyst
4
5=head1 DESCRIPTION
6
670b3d78 7This is a brief introduction to Catalyst. It explains the most important
aa2b0d97 8features of how Catalyst works and shows how to get a simple application
9up and running quickly. For an introduction (without code) to Catalyst
10itself, and why you should be using it, see L<Catalyst::Manual::About>.
fc7ec1d9 11
12=head2 What is Catalyst?
13
129cfe74 14Catalyst is an elegant web application framework, extremely flexible yet
e178a66a 15extremely simple. It's similar to Ruby on Rails, Spring (Java) and
16L<Maypole>, upon which it was originally based.
fc7ec1d9 17
18=head3 MVC
19
e178a66a 20Catalyst follows the Model-View-Controller (MVC) design pattern,
21allowing you to easily separate concerns, like content, presentation,
22and flow control, into separate modules. This separation allows you to
23modify code that handles one concern without affecting code that handles
24the others. Catalyst promotes the re-use of existing Perl modules that
25already handle common web application concerns well.
fc7ec1d9 26
e178a66a 27Here's how the M, V, and C map to those concerns, with examples of
28well-known Perl modules you may want to use for each.
fc7ec1d9 29
30=over 4
31
4a6895ce 32=item * B<Model>
fc7ec1d9 33
34Access and modify content (data). L<Class::DBI>, L<Plucene>, L<Net::LDAP>...
35
4a6895ce 36=item * B<View>
fc7ec1d9 37
e178a66a 38Present content to the user. L<Template Toolkit|Template>,
39L<Mason|HTML::Mason>, L<HTML::Template>...
fc7ec1d9 40
4a6895ce 41=item * B<Controller>
fc7ec1d9 42
129cfe74 43Control the whole request phase, check parameters, dispatch actions, flow
44control. Catalyst!
fc7ec1d9 45
46=back
47
26e73131 48If you're unfamiliar with MVC and design patterns, you may want to check
49out the original book on the subject, I<Design Patterns>, by Gamma,
50Helm, Johnson, and Vlissides, also known as the Gang of Four (GoF). You
51can also just Google it. Many, many web application frameworks are
52based on MVC, including all those listed above.
fc7ec1d9 53
54=head3 Flexibility
55
e178a66a 56Catalyst is much more flexible than many other frameworks. We'll talk
57more about this later, but rest assured you can use your favorite Perl
58modules with Catalyst.
fc7ec1d9 59
60=over 4
61
72d9bfc7 62=item * B<Multiple Models, Views, and Controllers>
fc7ec1d9 63
e178a66a 64To build a Catalyst application, you handle each type of concern inside
65special modules called L</Components>. Often this code will be very
66simple, just calling out to Perl modules like those listed above under
67L</MVC>. Catalyst handles these components in a very flexible way. Use
68as many Models, Views, and Controllers as you like, using as many
69different Perl modules as you like, all in the same application. Want to
70manipulate multiple databases, and retrieve some data via LDAP? No
71problem. Want to present data from the same Model using L<Template
72Toolkit|Template> and L<PDF::Template>? Easy.
fc7ec1d9 73
cda8d1ac 74=item * B<Reuseable Components>
fc7ec1d9 75
e178a66a 76Not only does Catalyst promote the re-use of already existing Perl
77modules, it also allows you to re-use your Catalyst components in
78multiple Catalyst applications.
fc7ec1d9 79
4a6895ce 80=item * B<Unrestrained URL-to-Action Dispatching>
fc7ec1d9 81
e178a66a 82Catalyst allows you to dispatch any URLs to any application L<Actions>,
83even through regular expressions! Unlike most other frameworks, it
84doesn't require mod_rewrite or class and method names in URLs.
fc7ec1d9 85
e178a66a 86With Catalyst you register your actions and address them directly. For
87example:
fc7ec1d9 88
e3dc9d78 89 sub hello : Global {
fc7ec1d9 90 my ( $self, $context ) = @_;
66f6e959 91 $context->response->body('Hello World!');
5a8ed4fe 92 }
fc7ec1d9 93
94Now http://localhost:3000/hello prints "Hello World!".
95
4a6895ce 96=item * B<Support for CGI, mod_perl, Apache::Request>
fc7ec1d9 97
98Use L<Catalyst::Engine::Apache> or L<Catalyst::Engine::CGI>.
99
100=back
101
102=head3 Simplicity
103
e178a66a 104The best part is that Catalyst implements all this flexibility in a very
105simple way.
fc7ec1d9 106
6f4e1683 107=over 4
108
4a6895ce 109=item * B<Building Block Interface>
fc7ec1d9 110
e178a66a 111Components interoperate very smoothly. For example, Catalyst
112automatically makes a L<Context> object available to every
113component. Via the context, you can access the request object, share
114data between components, and control the flow of your
115application. Building a Catalyst application feels a lot like snapping
129cfe74 116together toy building blocks, and everything just works.
fc7ec1d9 117
4a6895ce 118=item * B<Component Auto-Discovery>
fc7ec1d9 119
e178a66a 120No need to C<use> all of your components. Catalyst automatically finds
121and loads them.
fc7ec1d9 122
4a6895ce 123=item * B<Pre-Built Components for Popular Modules>
fc7ec1d9 124
e178a66a 125See L<Catalyst::Model::CDBI> for L<Class::DBI>, or L<Catalyst::View::TT>
126for L<Template Toolkit|Template>.
fc7ec1d9 127
72d9bfc7 128=item * B<Built-in Test Framework>
fc7ec1d9 129
e178a66a 130Catalyst comes with a built-in, lightweight http server and test
131framework, making it easy to test applications from the command line.
fc7ec1d9 132
4a6895ce 133=item * B<Helper Scripts>
fc7ec1d9 134
e178a66a 135Catalyst provides helper scripts to quickly generate running starter
136code for components and unit tests. See L<Catalyst::Helper>.
fc7ec1d9 137
6f4e1683 138=back
139
fc7ec1d9 140=head2 Quickstart
141
e178a66a 142Here's how to install Catalyst and get a simple application up and
143running, using the helper scripts described above.
fc7ec1d9 144
145=head3 Install
146
d538823f 147 $ perl -MCPAN -e 'install Task::Catalyst'
fc7ec1d9 148
149=head3 Setup
150
2feb6632 151 $ catalyst.pl MyApp
b33ed88c 152 # output omitted
2feb6632 153 $ cd MyApp
ac4a0ae0 154 $ script/myapp_create.pl controller Library::Login
fc7ec1d9 155
156=head3 Run
157
b33ed88c 158 $ script/myapp_server.pl
fc7ec1d9 159
129cfe74 160Now visit these locations with your favorite browser or user agent to see
161Catalyst in action:
fc7ec1d9 162
163=over 4
164
165=item http://localhost:3000/
166
ac4a0ae0 167=item http://localhost:3000/library/login/
fc7ec1d9 168
169=back
170
171Dead easy!
172
173=head2 How It Works
174
e178a66a 175Let's see how Catalyst works, by taking a closer look at the components
176and other parts of a Catalyst application.
fc7ec1d9 177
178=head3 Application Class
179
e178a66a 180In addition to the Model, View, and Controller components, there's a
181single class that represents your application itself. This is where you
182configure your application, load plugins, define application-wide
183actions, and extend Catalyst.
fc7ec1d9 184
185 package MyApp;
186
187 use strict;
188 use Catalyst qw/-Debug/;
189
190 MyApp->config(
191 name => 'My Application',
fc7ec1d9 192
b33ed88c 193 # You can put anything else you want in here:
194 my_configuration_variable => 'something',
fc7ec1d9 195 );
196
5a8ed4fe 197 sub default : Private {
fc7ec1d9 198 my ( $self, $context ) = @_;
e178a66a 199 $context->response->body('Catalyst rocks!');
5a8ed4fe 200 }
fc7ec1d9 201
202 1;
203
66f6e959 204For most applications, Catalyst requires you to define only one config
205parameter:
fc7ec1d9 206
207=over 4
208
4a6895ce 209=item * B<name>
fc7ec1d9 210
211Name of your application.
212
fc7ec1d9 213=back
214
e178a66a 215Optionally, you can specify a B<root> parameter for templates and static
216data. If omitted, Catalyst will try to auto-detect the directory's
217location. You can define as many parameters as you want for plugins or
218whatever you need. You can access them anywhere in your application via
219C<$context-E<gt>config-E<gt>{$param_name}>.
fc7ec1d9 220
221=head3 Context
222
e178a66a 223Catalyst automatically blesses a Context object into your application
224class and makes it available everywhere in your application. Use the
225Context to directly interact with Catalyst and glue your L<Components>
226together. For example, if you need to use the Context from within a
227Template Toolkit template, it's already there:
c42f5bbf 228
229 <h1>Welcome to [% c.config.name %]!</h1>
fc7ec1d9 230
e178a66a 231As illustrated in our URL-to-Action dispatching example, the Context is
232always the second method parameter, behind the Component object
233reference or class name itself. Previously we called it C<$context> for
234clarity, but most Catalyst developers just call it C<$c>:
fc7ec1d9 235
e3dc9d78 236 sub hello : Global {
fc7ec1d9 237 my ( $self, $c ) = @_;
66f6e959 238 $c->res->body('Hello World!');
5a8ed4fe 239 }
fc7ec1d9 240
241The Context contains several important objects:
242
243=over 4
244
245=item * L<Catalyst::Request>
246
247 $c->request
248 $c->req # alias
249
129cfe74 250The request object contains all kinds of request-specific information, like
251query parameters, cookies, uploads, headers, and more.
fc7ec1d9 252
253 $c->req->params->{foo};
254 $c->req->cookies->{sessionid};
255 $c->req->headers->content_type;
256 $c->req->base;
257
afdca3a3 258=item * L<Catalyst::Response>
fc7ec1d9 259
260 $c->response
261 $c->res # alias
262
129cfe74 263The response is like the request, but contains just response-specific
264information.
fc7ec1d9 265
66f6e959 266 $c->res->body('Hello World');
fc7ec1d9 267 $c->res->status(404);
268 $c->res->redirect('http://oook.de');
269
270=item * L<Catalyst::Config>
271
272 $c->config
fc7ec1d9 273 $c->config->root;
274 $c->config->name;
275
276=item * L<Catalyst::Log>
277
278 $c->log
279
280 $c->log->debug('Something happened');
281 $c->log->info('Something you should know');
282
4a6895ce 283=item * B<Stash>
fc7ec1d9 284
285 $c->stash
fc7ec1d9 286 $c->stash->{foo} = 'bar';
287
288=back
289
129cfe74 290The last of these, the stash, is a universal hash for sharing data among
291application components. For an example, we return to our 'hello' action:
fc7ec1d9 292
e3dc9d78 293 sub hello : Global {
5a8ed4fe 294 my ( $self, $c ) = @_;
295 $c->stash->{message} = 'Hello World!';
4c6807d2 296 $c->forward('show_message');
5a8ed4fe 297 }
fc7ec1d9 298
4c6807d2 299 sub show_message : Private {
5a8ed4fe 300 my ( $self, $c ) = @_;
66f6e959 301 $c->res->body( $c->stash->{message} );
5a8ed4fe 302 }
fc7ec1d9 303
e178a66a 304Note that the stash should be used only for passing data in an
305individual request cycle; it gets cleared at a new request. If you need
306to maintain more persistent data, use a session.
dd25a192 307
fc7ec1d9 308=head3 Actions
309
e178a66a 310A Catalyst controller is defined by its actions. An action is a sub with
311a special attribute. You've already seen some examples of actions in
312this document. The URL (for example http://localhost.3000/foo/bar)
313consists of two parts, the base (http://localhost:3000/ in this example)
314and the path (foo/bar). Please note that the trailing slash after the
315hostname[:port] always belongs to base and not to the action.
cda8d1ac 316
317Catalyst supports several types of actions:
fc7ec1d9 318
319=over 4
320
4a6895ce 321=item * B<Literal>
fc7ec1d9 322
e178a66a 323 package MyApp::Controller::My::Controller;
f29c48dd 324 sub bar : Path('foo/bar') { }
fc7ec1d9 325
e178a66a 326Literal C<Path> actions will act relative to their current
327namespace. The above example matches only
328http://localhost:3000/my/controller/foo/bar. If you start your path with
329a forward slash, it will match from the root. Example:
0cf56dbc 330
e178a66a 331 package MyApp::Controller::My::Controller;
0cf56dbc 332 sub bar : Path('/foo/bar') { }
333
fc7ec1d9 334Matches only http://localhost:3000/foo/bar.
335
e178a66a 336 package MyApp::Controller::My::Controller;
0cf56dbc 337 sub bar : Path { }
338
e178a66a 339By leaving the C<Path> definition empty, it will match on the namespace
340root. The above code matches http://localhost:3000/my/controller.
0cf56dbc 341
4a6895ce 342=item * B<Regex>
fc7ec1d9 343
b33ed88c 344 sub bar : Regex('^item(\d+)/order(\d+)$') { }
fc7ec1d9 345
129cfe74 346Matches any URL that matches the pattern in the action key, e.g.
e178a66a 347http://localhost:3000/item23/order42. The '' around the regexp is
348optional, but perltidy likes it. :)
b33ed88c 349
e178a66a 350Regex matches act globally, i.e. without reference to the namespace from
351which it is called, so that a C<bar> method in the
352C<MyApp::Controller::Catalog::Order::Process> namespace won't match any
353form of C<bar>, C<Catalog>, C<Order>, or C<Process> unless you
354explicitly put this in the regex. To achieve the above, you should
355consider using a C<LocalRegex> action.
66f6e959 356
357=item * B<LocalRegex>
358
359 sub bar : LocalRegex('^widget(\d+)$') { }
fc7ec1d9 360
66f6e959 361LocalRegex actions act locally. If you were to use C<bar> in
0cf56dbc 362C<MyApp::Controller::Catalog>, the above example would match urls like
363http://localhost:3000/catalog/widget23.
364
e178a66a 365If you omit the "C<^>" from your regex, then it will match any depth
366from the controller and not immediately off of the controller name. The
367following example differs from the above code in that it will match
0cf56dbc 368http://localhost:3000/catalog/foo/widget23 as well.
369
370 package MyApp::Controller::Catalog;
371 sub bar : LocalRegex('widget(\d+)$') { }
66f6e959 372
e178a66a 373For both LocalRegex and Regex actions, if you use capturing parentheses
374to extract values within the matching URL, those values are available in
375the C<$c-E<gt>req-E<gt>snippets> array. In the above example, "widget23"
376would capture "23" in the above example, and
377C<$c-E<gt>req-E<gt>snippets-E<gt>[0]> would be "23". If you want to pass
378arguments at the end of your URL, you must use regex action keys. See
379L</URL Path Handling> below.
fc7ec1d9 380
72d9bfc7 381=item * B<Top-level>
cda8d1ac 382
383 package MyApp;
384 sub foo : Global { }
385
b33ed88c 386Matches http://localhost:3000/foo. The function name is mapped directly
387to the application base.
cda8d1ac 388
4a6895ce 389=item * B<Namespace-Prefixed>
fc7ec1d9 390
e178a66a 391 package MyApp::Controller::My::Controller;
e3dc9d78 392 sub foo : Local { }
fc7ec1d9 393
cda8d1ac 394Matches http://localhost:3000/my/controller/foo.
fc7ec1d9 395
129cfe74 396This action type indicates that the matching URL must be prefixed with a
e178a66a 397modified form of the component's class (package) name. This modified
398class name excludes the parts that have a pre-defined meaning in
399Catalyst ("MyApp::Controller" in the above example), replaces "::" with
400"/", and converts the name to lower case. See L</Components> for a full
401explanation of the pre-defined meaning of Catalyst component class
402names.
fc7ec1d9 403
4a6895ce 404=item * B<Private>
fc7ec1d9 405
5a8ed4fe 406 sub foo : Private { }
fc7ec1d9 407
e178a66a 408Matches no URL, and cannot be executed by requesting a URL that
409corresponds to the action key. Private actions can be executed only
410inside a Catalyst application, by calling the C<forward> method:
fc7ec1d9 411
5a8ed4fe 412 $c->forward('foo');
fc7ec1d9 413
129cfe74 414See L</Flow Control> for a full explanation of C<forward>. Note that, as
fc9c8698 415discussed there, when forwarding from another component, you must use
416the absolute path to the method, so that a private C<bar> method in your
417C<MyApp::Controller::Catalog::Order::Process> controller must, if called
418from elsewhere, be reached with
419C<$c-E<gt>forward('/catalog/order/process/bar')>.
fc7ec1d9 420
421=back
422
b33ed88c 423B<Note:> After seeing these examples, you probably wonder what the point
424is of defining names for regex and path actions. Actually, every public
425action is also a private one, so you have one unified way of addressing
426components in your C<forward>s.
cda8d1ac 427
72d9bfc7 428=head4 Built-in Private Actions
fc7ec1d9 429
fc9c8698 430In response to specific application states, Catalyst will automatically
431call these built-in private actions in your application class:
fc7ec1d9 432
433=over 4
434
cda8d1ac 435=item * B<default : Private>
fc7ec1d9 436
fc9c8698 437Called when no other action matches. Could be used, for example, for
438displaying a generic frontpage for the main app, or an error page for
439individual controllers.
fc7ec1d9 440
0cf56dbc 441If C<default> isn't acting how you would expect, look at using a
e178a66a 442L<Literal> C<Path> action (with an empty path string). The difference is
443that C<Path> takes arguments relative from the namespace and C<default>
444I<always> takes arguments relative from the root, regardless of what
445controller it's in.
0cf56dbc 446
66f6e959 447=item * B<index : Private>
448
449C<index> is much like C<default> except that it takes no arguments
e178a66a 450and it is weighted slightly higher in the matching process. It is
451useful as a static entry point to a controller, e.g. to have a static
61a9002d 452welcome page. Note that it's also weighted higher than Path.
66f6e959 453
cda8d1ac 454=item * B<begin : Private>
fc7ec1d9 455
fc9c8698 456Called at the beginning of a request, before any matching actions are
457called.
fc7ec1d9 458
cda8d1ac 459=item * B<end : Private>
4a6895ce 460
fc7ec1d9 461Called at the end of a request, after all matching actions are called.
462
fc9c8698 463=back
464
6b10c72b 465=head4 Built-in actions in controllers/autochaining
fc7ec1d9 466
e178a66a 467 Package MyApp::Controller::Foo;
cda8d1ac 468 sub begin : Private { }
5a8ed4fe 469 sub default : Private { }
eff5f524 470 sub auto : Private { }
fc7ec1d9 471
fc9c8698 472You can define built-in private actions within your controllers as
473well. The actions will override the ones in less-specific controllers,
474or your application class. In other words, for each of the three
475built-in private actions, only one will be run in any request
e178a66a 476cycle. Thus, if C<MyApp::Controller::Catalog::begin> exists, it will be
477run in place of C<MyApp::begin> if you're in the C<catalog> namespace,
478and C<MyApp::Controller::Catalog::Order::begin> would override this in
479turn.
fc9c8698 480
eff5f524 481In addition to the normal built-in actions, you have a special action
482for making chains, C<auto>. Such C<auto> actions will be run after any
fc9c8698 483C<begin>, but before your action is processed. Unlike the other
eff5f524 484built-ins, C<auto> actions I<do not> override each other; they will be
485called in turn, starting with the application class and going through to
486the I<most> specific class. I<This is the reverse of the order in which
487the normal built-ins override each other>.
fc9c8698 488
489Here are some examples of the order in which the various built-ins
490would be called:
cda8d1ac 491
492=over 4
493
fc9c8698 494=item for a request for C</foo/foo>
cda8d1ac 495
496 MyApp::begin
80ef2e6d 497 MyApp::auto
e178a66a 498 MyApp::Controller::Foo::default # in the absence of MyApp::Controller::Foo::Foo
cda8d1ac 499 MyApp::end
500
fc9c8698 501=item for a request for C</foo/bar/foo>
cda8d1ac 502
e178a66a 503 MyApp::Controller::Foo::Bar::begin
80ef2e6d 504 MyApp::auto
e178a66a 505 MyApp::Controller::Foo::auto
506 MyApp::Controller::Foo::Bar::auto
507 MyApp::Controller::Foo::Bar::default # for MyApp::Controller::Foo::Bar::foo
508 MyApp::Controller::Foo::Bar::end
80ef2e6d 509
510=back
511
fc9c8698 512The C<auto> action is also distinguished by the fact that you can break
513out of the processing chain by returning 0. If an C<auto> action returns
5140, any remaining actions will be skipped, except for C<end>. So, for the
515request above, if the first auto returns false, the chain would look
516like this:
80ef2e6d 517
518=over 4
519
fc9c8698 520=item for a request for C</foo/bar/foo> where first C<auto> returns
521false
80ef2e6d 522
e178a66a 523 MyApp::Controller::Foo::Bar::begin
80ef2e6d 524 MyApp::auto
e178a66a 525 MyApp::Controller::Foo::Bar::end
cda8d1ac 526
527=back
4a6895ce 528
fc9c8698 529An example of why one might use this is an authentication action: you
530could set up a C<auto> action to handle authentication in your
531application class (which will always be called first), and if
532authentication fails, returning 0 would skip any remaining methods
533for that URL.
03805733 534
fc9c8698 535B<Note:> Looking at it another way, C<auto> actions have to return a
536true value to continue processing! You can also C<die> in the autochain
537action; in that case, the request will go straight to the finalize
538stage, without processing further actions.
03805733 539
6b10c72b 540=head4 URL Path Handling
4a6895ce 541
70d5ae49 542You can pass variable arguments as part of the URL path, separated with
543forward slashes (/). If the action is a Regex or LocalRegex, the '$' anchor
544must be used. For example, suppose you want to handle C</foo/$bar/$baz>,
545where C<$bar> and C<$baz> may vary:
4a6895ce 546
cda8d1ac 547 sub foo : Regex('^foo$') { my ($self, $context, $bar, $baz) = @_; }
4a6895ce 548
fc9c8698 549But what if you also defined actions for C</foo/boo> and C</foo/boo/hoo>?
4a6895ce 550
f29c48dd 551 sub boo : Path('foo/boo') { .. }
552 sub hoo : Path('foo/boo/hoo') { .. }
4a6895ce 553
554Catalyst matches actions in most specific to least specific order:
555
556 /foo/boo/hoo
557 /foo/boo
fc9c8698 558 /foo # might be /foo/bar/baz but won't be /foo/boo/hoo
4a6895ce 559
fc9c8698 560So Catalyst would never mistakenly dispatch the first two URLs to the
561'^foo$' action.
fc7ec1d9 562
70d5ae49 563If a Regex or LocalRegex action doesn't use the '$' anchor, the action will
564still match a URL containing arguments, however the arguments won't be
565available via C<@_>.
566
6b10c72b 567=head4 Parameter Processing
2ef2fb0f 568
fc9c8698 569Parameters passed in the URL query string are handled with methods in
570the L<Catalyst::Request> class. The C<param> method is functionally
571equivalent to the C<param> method of C<CGI.pm> and can be used in
572modules that require this.
2ef2fb0f 573
574 # http://localhost:3000/catalog/view/?category=hardware&page=3
575 my $category = $c->req->param('category');
576 my $current_page = $c->req->param('page') || 1;
577
578 # multiple values for single parameter name
579 my @values = $c->req->param('scrolling_list');
580
581 # DFV requires a CGI.pm-like input hash
582 my $results = Data::FormValidator->check($c->req->params, \%dfv_profile);
583
fc7ec1d9 584=head3 Flow Control
585
d08ced28 586You control the application flow with the C<forward> method, which
587accepts the key of an action to execute. This can be an action in the
588same or another Catalyst controller, or a Class name, optionally
589followed by a method name. After a C<forward>, the control flow will
590return to the method from which the C<forward> was issued.
591
592A C<forward> is similar to a method call. The main differences are that
593it wraps the call in an C<eval> to allow exception handling; it
594automatically passes along the context object (C<$c> or C<$context>);
595and it allows profiling of each call (displayed in the log with
596debugging enabled).
fc7ec1d9 597
e3dc9d78 598 sub hello : Global {
5a8ed4fe 599 my ( $self, $c ) = @_;
600 $c->stash->{message} = 'Hello World!';
d08ced28 601 $c->forward('check_message'); # $c is automatically included
5a8ed4fe 602 }
fc7ec1d9 603
4c6807d2 604 sub check_message : Private {
5a8ed4fe 605 my ( $self, $c ) = @_;
606 return unless $c->stash->{message};
4c6807d2 607 $c->forward('show_message');
5a8ed4fe 608 }
fc7ec1d9 609
4c6807d2 610 sub show_message : Private {
5a8ed4fe 611 my ( $self, $c ) = @_;
66f6e959 612 $c->res->body( $c->stash->{message} );
5a8ed4fe 613 }
3323f920 614
d08ced28 615A C<forward> does not create a new request, so your request
616object (C<$c-E<gt>req>) will remain unchanged. This is a
617key difference between using C<forward> and issuing a
618redirect.
3323f920 619
d08ced28 620You can pass new arguments to a C<forward> by adding them
621in an anonymous array. In this case C<$c-E<gt>req-E<gt>args>
622will be changed for the duration of the C<forward> only; upon
623return, the original value of C<$c-E<gt>req-E<gt>args> will
624be reset.
3323f920 625
626 sub hello : Global {
627 my ( $self, $c ) = @_;
628 $c->stash->{message} = 'Hello World!';
d08ced28 629 $c->forward('check_message',[qw/test1/]);
630 # now $c->req->args is back to what it was before
3323f920 631 }
632
d08ced28 633 sub check_message : Private {
634 my ( $self, $c ) = @_;
635 my $first_argument = $c->req->args[0]; # now = 'test1'
636 # do something...
637 }
cda8d1ac 638
d08ced28 639As you can see from these examples, you can just use the method name as
640long as you are referring to methods in the same controller. If you want
641to forward to a method in another controller, or the main application,
642you will have to refer to the method by absolute path.
cda8d1ac 643
644 $c->forward('/my/controller/action');
d08ced28 645 $c->forward('/default'); # calls default in main application
fc7ec1d9 646
d08ced28 647Here are some examples of how to forward to classes and methods.
fc7ec1d9 648
e3dc9d78 649 sub hello : Global {
5a8ed4fe 650 my ( $self, $c ) = @_;
e178a66a 651 $c->forward(qw/MyApp::Model::Hello say_hello/);
5a8ed4fe 652 }
fc7ec1d9 653
e3dc9d78 654 sub bye : Global {
5a8ed4fe 655 my ( $self, $c ) = @_;
e178a66a 656 $c->forward('MyApp::Model::Hello'); # no method: will try 'process'
5a8ed4fe 657 }
fc7ec1d9 658
e178a66a 659 package MyApp::Model::Hello;
fc7ec1d9 660
661 sub say_hello {
662 my ( $self, $c ) = @_;
66f6e959 663 $c->res->body('Hello World!');
fc7ec1d9 664 }
665
666 sub process {
667 my ( $self, $c ) = @_;
66f6e959 668 $c->res->body('Goodbye World!');
fc7ec1d9 669 }
670
d08ced28 671Note that C<forward> returns to the calling action and continues
13436c14 672processing after the action finishes. If you want all further processing
673in the calling action to stop, use C<detach> instead, which will execute
674the C<detach>ed action and not return to the calling sub. In both cases,
675Catalyst will automatically try to call process() if you omit the
676method.
fc7ec1d9 677
678=head3 Components
679
129cfe74 680Catalyst has an uncommonly flexible component system. You can define as many
681L<Models>, L<Views>, and L<Controllers> as you like.
fc7ec1d9 682
129cfe74 683All components must inherit from L<Catalyst::Base>, which provides a simple
684class structure and some common class methods like C<config> and C<new>
685(constructor).
fc7ec1d9 686
e178a66a 687 package MyApp::Controller::Catalog;
fc7ec1d9 688
689 use strict;
690 use base 'Catalyst::Base';
691
692 __PACKAGE__->config( foo => 'bar' );
693
694 1;
695
6b10c72b 696You don't have to C<use> or otherwise register Models, Views, and
697Controllers. Catalyst automatically discovers and instantiates them
698when you call C<setup> in the main application. All you need to do is
699put them in directories named for each Component type. Notice that you
700can use some very terse aliases for each one.
fc7ec1d9 701
702=over 4
703
4a6895ce 704=item * B<MyApp/Model/>
fc7ec1d9 705
4a6895ce 706=item * B<MyApp/M/>
fc7ec1d9 707
4a6895ce 708=item * B<MyApp/View/>
fc7ec1d9 709
4a6895ce 710=item * B<MyApp/V/>
fc7ec1d9 711
4a6895ce 712=item * B<MyApp/Controller/>
fc7ec1d9 713
4a6895ce 714=item * B<MyApp/C/>
fc7ec1d9 715
716=back
717
718=head4 Views
719
129cfe74 720To show how to define views, we'll use an already-existing base class for the
721L<Template Toolkit|Template>, L<Catalyst::View::TT>. All we need to do is
722inherit from this class:
fc7ec1d9 723
e178a66a 724 package MyApp::View::TT;
fc7ec1d9 725
726 use strict;
727 use base 'Catalyst::View::TT';
728
729 1;
730
b33ed88c 731(You can also generate this automatically by using the helper script:
732
733 script/myapp_create.pl view TT TT
734
fb9257c1 735where the first C<TT> tells the script that the name of the view should
736be C<TT>, and the second that it should be a Template Toolkit view.)
b33ed88c 737
129cfe74 738This gives us a process() method and we can now just do
e178a66a 739$c->forward('MyApp::View::TT') to render our templates. The base class
740makes process() implicit, so we don't have to say
741C<$c-E<gt>forward(qw/MyApp::View::TT process/)>.
fc7ec1d9 742
e3dc9d78 743 sub hello : Global {
5a8ed4fe 744 my ( $self, $c ) = @_;
745 $c->stash->{template} = 'hello.tt';
746 }
fc7ec1d9 747
5a8ed4fe 748 sub end : Private {
749 my ( $self, $c ) = @_;
e178a66a 750 $c->forward('MyApp::View::TT');
5a8ed4fe 751 }
fc7ec1d9 752
6b10c72b 753You normally render templates at the end of a request, so it's a perfect
754use for the global C<end> action.
fc7ec1d9 755
129cfe74 756Also, be sure to put the template under the directory specified in
6b10c72b 757C<$c-E<gt>config-E<gt>{root}>, or you'll be forced to look at our
758eyecandy debug screen. ;)
fc7ec1d9 759
760=head4 Models
761
e178a66a 762To show how to define models, again we'll use an already-existing base
763class, this time for L<Class::DBI>: L<Catalyst::Model::CDBI>.
fc7ec1d9 764
765But first, we need a database.
766
767 -- myapp.sql
768 CREATE TABLE foo (
769 id INTEGER PRIMARY KEY,
770 data TEXT
771 );
772
773 CREATE TABLE bar (
774 id INTEGER PRIMARY KEY,
775 foo INTEGER REFERENCES foo,
776 data TEXT
777 );
778
779 INSERT INTO foo (data) VALUES ('TEST!');
780
781
782 % sqlite /tmp/myapp.db < myapp.sql
783
784Now we can create a CDBI component for this database.
785
e178a66a 786 package MyApp::Model::CDBI;
fc7ec1d9 787
788 use strict;
789 use base 'Catalyst::Model::CDBI';
790
791 __PACKAGE__->config(
792 dsn => 'dbi:SQLite:/tmp/myapp.db',
793 relationships => 1
794 );
795
796 1;
797
e178a66a 798Catalyst automatically loads table layouts and relationships. Use the
799stash to pass data to your templates.
fc7ec1d9 800
801 package MyApp;
802
803 use strict;
804 use Catalyst '-Debug';
805
806 __PACKAGE__->config(
807 name => 'My Application',
808 root => '/home/joeuser/myapp/root'
809 );
cda8d1ac 810
811 __PACKAGE__->setup;
fc7ec1d9 812
5a8ed4fe 813 sub end : Private {
814 my ( $self, $c ) = @_;
815 $c->stash->{template} ||= 'index.tt';
e178a66a 816 $c->forward('MyApp::View::TT');
5a8ed4fe 817 }
fc7ec1d9 818
e3dc9d78 819 sub view : Global {
5a8ed4fe 820 my ( $self, $c, $id ) = @_;
e178a66a 821 $c->stash->{item} = MyApp::Model::CDBI::Foo->retrieve($id);
5a8ed4fe 822 }
fc7ec1d9 823
824 1;
825
6b10c72b 826 # Then, in a TT template:
fc7ec1d9 827 The id is [% item.data %]
828
6b10c72b 829Models do not have to be part of your Catalyst application; you
830can always call an outside module that serves as your Model:
831
832 # in a Controller
833 sub list : Local {
834 my ( $self, $c ) = @_;
835 $c->stash->{template} = 'list.tt';
836 use Some::Outside::CDBI::Module;
837 my @records = Some::Outside::CDBI::Module->retrieve_all;
838 $c->stash->{records} = \@records;
839 }
840
841But by using a Model that is part of your Catalyst application, you gain
842several things: you don't have to C<use> each component, Catalyst will
843find and load it automatically at compile-time; you can C<forward> to
26e73131 844the module, which can only be done to Catalyst components; and only
6b10c72b 845Catalyst components can be fetched with
e178a66a 846C<$c-E<gt>model('SomeModel')>.
6b10c72b 847
848Happily, since many people have existing Model classes that they
849would like to use with Catalyst (or, conversely, they want to
850write Catalyst models that can be used outside of Catalyst, e.g.
851in a cron job), it's trivial to write a simple component in
852Catalyst that slurps in an outside Model:
853
e178a66a 854 package MyApp::Model::Catalog;
6b10c72b 855 use base qw/Catalyst::Base Some::Other::CDBI::Module::Catalog/;
856 1;
857
858and that's it! Now C<Some::Other::CDBI::Module::Catalog> is part of your
e178a66a 859Cat app as C<MyApp::Model::Catalog>.
6b10c72b 860
fc7ec1d9 861=head4 Controllers
862
129cfe74 863Multiple controllers are a good way to separate logical domains of your
864application.
fc7ec1d9 865
e178a66a 866 package MyApp::Controller::Login;
fc7ec1d9 867
fb9257c1 868 sub sign-in : Local { }
869 sub new-password : Local { }
870 sub sign-out : Local { }
fc7ec1d9 871
e178a66a 872 package MyApp::Controller::Catalog;
fc7ec1d9 873
e3dc9d78 874 sub view : Local { }
875 sub list : Local { }
fc7ec1d9 876
e178a66a 877 package MyApp::Controller::Cart;
fc7ec1d9 878
e3dc9d78 879 sub add : Local { }
880 sub update : Local { }
881 sub order : Local { }
fc7ec1d9 882
883=head3 Testing
884
e178a66a 885Catalyst has a built-in http server for testing! (Later, you can easily
886use a more powerful server, e.g. Apache/mod_perl, in a production
887environment.)
fc7ec1d9 888
889Start your application on the command line...
890
b33ed88c 891 script/myapp_server.pl
fc7ec1d9 892
893...then visit http://localhost:3000/ in a browser to view the output.
894
895You can also do it all from the command line:
896
b33ed88c 897 script/myapp_test.pl http://localhost/
fc7ec1d9 898
899Have fun!
900
3cb1db8c 901=head1 SUPPORT
902
903IRC:
904
905 Join #catalyst on irc.perl.org.
906
72d9bfc7 907Mailing-lists:
3cb1db8c 908
909 http://lists.rawmode.org/mailman/listinfo/catalyst
910 http://lists.rawmode.org/mailman/listinfo/catalyst-dev
911
fc7ec1d9 912=head1 AUTHOR
913
cda8d1ac 914Sebastian Riedel, C<sri@oook.de>
915David Naughton, C<naughton@umn.edu>
916Marcus Ramberg, C<mramberg@cpan.org>
f531dd37 917Jesse Sheidlower, C<jester@panix.com>
129cfe74 918Danijel Milicevic, C<me@danijel.de>
fc7ec1d9 919
920=head1 COPYRIGHT
921
aa2b0d97 922This program is free software, you can redistribute it and/or modify it
923under the same terms as Perl itself.