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1 | =head1 NAME |
2 | |
3 | Catalyst::Manual::Intro - Introduction to Catalyst |
4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | This is a brief introduction to Catalyst. It explains the most important |
8 | features of how Catalyst works and shows how to get a simple application |
9 | up and running quickly. For an introduction (without code) to Catalyst |
10 | itself, and why you should be using it, see L<Catalyst::Manual::About>. |
11 | For a systematic step-by-step introduction to writing an application |
12 | with Catalyst, see L<Catalyst::Manual::Tutorial>. |
13 | |
14 | =head2 What is Catalyst? |
15 | |
16 | Catalyst is an elegant web application framework, extremely flexible |
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17 | yet extremely simple. It's similar to Ruby on Rails, Spring (Java), and |
18 | L<Maypole|Maypole>, upon which it was originally based. Its most |
19 | important design philosphy is to provide easy access to all the tools |
20 | you need to develop web applications, with few restrictions on how you |
21 | need to use these tools. However, this does mean that it is always |
22 | possible to do things in a different way. Other web frameworks are |
23 | I<initially> simpler to use, but achieve this by locking the programmer |
24 | into a single set of tools. Catalyst's emphasis on flexibility means |
25 | that you have to think more to use it. We view this as a feature. For |
26 | example, this leads to Catalyst being more suited to system integration |
27 | tasks than other web frameworks. |
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28 | |
29 | =head3 MVC |
30 | |
31 | Catalyst follows the Model-View-Controller (MVC) design pattern, |
32 | allowing you to easily separate concerns, like content, presentation, |
33 | and flow control, into separate modules. This separation allows you to |
34 | modify code that handles one concern without affecting code that handles |
35 | the others. Catalyst promotes the re-use of existing Perl modules that |
36 | already handle common web application concerns well. |
37 | |
38 | Here's how the Model, View, and Controller map to those concerns, with |
39 | examples of well-known Perl modules you may want to use for each. |
40 | |
41 | =over 4 |
42 | |
43 | =item * B<Model> |
44 | |
45 | Access and modify content (data). L<DBIx::Class>, L<Class::DBI>, |
46 | L<Xapian>, L<Net::LDAP>... |
47 | |
48 | =item * B<View> |
49 | |
50 | Present content to the user. L<Template Toolkit|Template>, |
51 | L<Mason|HTML::Mason>, L<HTML::Template>... |
52 | |
53 | =item * B<Controller> |
54 | |
55 | Control the whole request phase, check parameters, dispatch actions, flow |
56 | control. Catalyst itself! |
57 | |
58 | =back |
59 | |
60 | If you're unfamiliar with MVC and design patterns, you may want to |
61 | check out the original book on the subject, I<Design Patterns>, by |
62 | Gamma, Helm, Johnson, and Vlissides, also known as the Gang of Four |
63 | (GoF). Many, many web application frameworks are based on MVC, which |
64 | is becoming a popular design paradigm for the world wide web. |
65 | |
66 | =head3 Flexibility |
67 | |
68 | Catalyst is much more flexible than many other frameworks. Rest assured |
69 | you can use your favorite Perl modules with Catalyst. |
70 | |
71 | =over 4 |
72 | |
73 | =item * B<Multiple Models, Views, and Controllers> |
74 | |
75 | To build a Catalyst application, you handle each type of concern inside |
76 | special modules called L</Components>. Often this code will be very |
77 | simple, just calling out to Perl modules like those listed above under |
78 | L</MVC>. Catalyst handles these components in a very flexible way. Use |
79 | as many Models, Views, and Controllers as you like, using as many |
80 | different Perl modules as you like, all in the same application. Want to |
81 | manipulate multiple databases, and retrieve some data via LDAP? No |
82 | problem. Want to present data from the same Model using L<Template |
83 | Toolkit|Template> and L<PDF::Template>? Easy. |
84 | |
85 | =item * B<Reuseable Components> |
86 | |
87 | Not only does Catalyst promote the re-use of already existing Perl |
88 | modules, it also allows you to re-use your Catalyst components in |
89 | multiple Catalyst applications. |
90 | |
91 | =item * B<Unrestrained URL-to-Action Dispatching> |
92 | |
93 | Catalyst allows you to dispatch any URLs to any application L</Actions>, |
94 | even through regular expressions! Unlike most other frameworks, it |
95 | doesn't require mod_rewrite or class and method names in URLs. |
96 | |
97 | With Catalyst you register your actions and address them directly. For |
98 | example: |
99 | |
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100 | sub hello : Local { |
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101 | my ( $self, $context ) = @_; |
102 | $context->response->body('Hello World!'); |
103 | } |
104 | |
105 | Now http://localhost:3000/hello prints "Hello World!". |
106 | |
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107 | Note that actions with the C< :Local > attribute are equivalent to |
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108 | using a C<:Path('action_name') > attribute, so our action could be |
109 | equivalently: |
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110 | |
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111 | sub hi : Path('hello') { |
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112 | my ( $self, $context ) = @_; |
113 | $context->response->body('Hello World!'); |
114 | } |
115 | |
116 | |
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117 | =item * B<Support for CGI, mod_perl, Apache::Request, FastCGI> |
118 | |
119 | Use L<Catalyst::Engine::Apache> or L<Catalyst::Engine::CGI>. Other |
120 | engines are also available. |
121 | |
122 | =back |
123 | |
124 | =head3 Simplicity |
125 | |
126 | The best part is that Catalyst implements all this flexibility in a very |
127 | simple way. |
128 | |
129 | =over 4 |
130 | |
131 | =item * B<Building Block Interface> |
132 | |
133 | Components interoperate very smoothly. For example, Catalyst |
134 | automatically makes a L</Context> object available to every |
135 | component. Via the context, you can access the request object, share |
136 | data between components, and control the flow of your |
137 | application. Building a Catalyst application feels a lot like snapping |
138 | together toy building blocks, and everything just works. |
139 | |
140 | =item * B<Component Auto-Discovery> |
141 | |
142 | No need to C<use> all of your components. Catalyst automatically finds |
143 | and loads them. |
144 | |
145 | =item * B<Pre-Built Components for Popular Modules> |
146 | |
147 | See L<Catalyst::Model::DBIC::Schema> for L<DBIx::Class>, or |
148 | L<Catalyst::View::TT> for L<Template Toolkit|Template>. |
149 | |
150 | =item * B<Built-in Test Framework> |
151 | |
152 | Catalyst comes with a built-in, lightweight http server and test |
153 | framework, making it easy to test applications from the web browser, |
154 | and the command line. |
155 | |
156 | =item * B<Helper Scripts> |
157 | |
158 | Catalyst provides helper scripts to quickly generate running starter |
159 | code for components and unit tests. Install L<Catalyst::Devel> and see |
160 | L<Catalyst::Helper>. |
161 | |
162 | =back |
163 | |
164 | =head2 Quickstart |
165 | |
166 | Here's how to install Catalyst and get a simple application up and |
167 | running, using the helper scripts described above. |
168 | |
169 | =head3 Install |
170 | |
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171 | Installation of Catalyst can be a time-consuming effort, due to its |
172 | large number of dependencies. Although most of the frustrations |
173 | associated with this are now ironed out and a simple C<cpan |
174 | Catalyst::Devel> or C<cpan Catalyst::Runtime> are now usually |
175 | straightforward, if you still have problems, you can use use Matt |
176 | Trout's C<cat-install> script, from |
177 | L<http://www.shadowcatsystems.co.uk/static/cat-install>, and then |
178 | install L<Catalyst::Devel>. |
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179 | |
180 | # perl cat-install |
181 | # perl -MCPAN -e 'install Catalyst::Devel' |
182 | |
183 | =head3 Setup |
184 | |
185 | $ catalyst.pl MyApp |
186 | # output omitted |
187 | $ cd MyApp |
188 | $ script/myapp_create.pl controller Library::Login |
189 | |
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190 | =head4 Frank Speiser's Amazon EC2 Catalyst SDK |
191 | |
192 | There are currently two flavors of publicly available Amazon Machine |
193 | Images (AMI) that include all the elements you'd need to begin |
194 | developing in a fully functional Catalyst environment within |
195 | minutes. See |
196 | L<Catalyst::Manual::Installation|Catalyst::Manual::Installation> for |
197 | more details. |
198 | |
199 | |
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200 | =head3 Run |
201 | |
202 | $ script/myapp_server.pl |
203 | |
204 | Now visit these locations with your favorite browser or user agent to see |
205 | Catalyst in action: |
206 | |
207 | (NOTE: Although we create a controller here, we don't actually use it. |
208 | Both of these URLs should take you to the welcome page.) |
209 | |
210 | |
211 | =over 4 |
212 | |
213 | =item http://localhost:3000/ |
214 | |
215 | =item http://localhost:3000/library/login/ |
216 | |
217 | =back |
218 | |
219 | =head2 How It Works |
220 | |
221 | Let's see how Catalyst works, by taking a closer look at the components |
222 | and other parts of a Catalyst application. |
223 | |
224 | =head3 Components |
225 | |
226 | Catalyst has an uncommonly flexible component system. You can define as |
227 | many L</Models>, L</Views>, and L</Controllers> as you like. As discussed |
228 | previously, the general idea is that the View is responsible for the |
229 | output of data to the user (typically via a web browser, but a View can |
230 | also generate PDFs or e-mails, for example); the Model is responsible |
231 | for providing data (typically from a relational database); and the |
232 | Controller is responsible for interacting with the user and deciding |
233 | how user input determines what actions the application takes. |
234 | |
235 | In the world of MVC, there are frequent discussions and disagreements |
236 | about the nature of each element - whether certain types of logic |
237 | belong in the Model or the Controller, etc. Catalyst's flexibility |
238 | means that this decision is entirely up to you, the programmer; |
239 | Catalyst doesn't enforce anything. See L<Catalyst::Manual::About> for |
240 | a general discussion of these issues. |
241 | |
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242 | Model, View and Controller components must inherit from L<Catalyst::Model>, |
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243 | L<Catalyst::View> and L<Catalyst::Controller>, respectively. These, in turn, inherit |
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244 | from L<Catalyst::Component> which provides a simple class structure and some |
245 | common class methods like C<config> and C<new> (constructor). |
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246 | |
247 | package MyApp::Controller::Catalog; |
248 | |
249 | use strict; |
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250 | use base 'Catalyst::Controller'; |
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251 | |
252 | __PACKAGE__->config( foo => 'bar' ); |
253 | |
254 | 1; |
255 | |
256 | You don't have to C<use> or otherwise register Models, Views, and |
257 | Controllers. Catalyst automatically discovers and instantiates them |
258 | when you call C<setup> in the main application. All you need to do is |
259 | put them in directories named for each Component type. You can use a |
260 | short alias for each one. |
261 | |
262 | =over 4 |
263 | |
264 | =item * B<MyApp/Model/> |
265 | |
266 | =item * B<MyApp/M/> |
267 | |
268 | =item * B<MyApp/View/> |
269 | |
270 | =item * B<MyApp/V/> |
271 | |
272 | =item * B<MyApp/Controller/> |
273 | |
274 | =item * B<MyApp/C/> |
275 | |
276 | =back |
277 | |
278 | In older versions of Catalyst, the recommended practice (and the one |
279 | automatically created by helper scripts) was to name the directories |
280 | C<M/>, C<V/>, and C<C/>. Though these still work, we now recommend |
281 | the use of the full names. |
282 | |
283 | =head4 Views |
284 | |
285 | To show how to define views, we'll use an already-existing base class for the |
286 | L<Template Toolkit|Template>, L<Catalyst::View::TT>. All we need to do is |
287 | inherit from this class: |
288 | |
289 | package MyApp::View::TT; |
290 | |
291 | use strict; |
292 | use base 'Catalyst::View::TT'; |
293 | |
294 | 1; |
295 | |
296 | (You can also generate this automatically by using the helper script: |
297 | |
298 | script/myapp_create.pl view TT TT |
299 | |
300 | where the first C<TT> tells the script that the name of the view should |
301 | be C<TT>, and the second that it should be a Template Toolkit view.) |
302 | |
303 | This gives us a process() method and we can now just do |
304 | $c->forward('MyApp::View::TT') to render our templates. The base class |
305 | makes process() implicit, so we don't have to say |
306 | C<$c-E<gt>forward(qw/MyApp::View::TT process/)>. |
307 | |
308 | sub hello : Global { |
309 | my ( $self, $c ) = @_; |
310 | $c->stash->{template} = 'hello.tt'; |
311 | } |
312 | |
313 | sub end : Private { |
314 | my ( $self, $c ) = @_; |
315 | $c->forward( $c->view('TT') ); |
316 | } |
317 | |
318 | You normally render templates at the end of a request, so it's a perfect |
319 | use for the global C<end> action. |
320 | |
321 | In practice, however, you would use a default C<end> action as supplied |
322 | by L<Catalyst::Action::RenderView>. |
323 | |
324 | Also, be sure to put the template under the directory specified in |
325 | C<$c-E<gt>config-E<gt>{root}>, or you'll end up looking at the debug |
326 | screen. |
327 | |
328 | =head4 Models |
329 | |
330 | Models are providers of data. This data could come from anywhere - a |
331 | search engine index, a spreadsheet, the file system - but typically a |
332 | Model represents a database table. The data source does not |
333 | intrinsically have much to do with web applications or Catalyst - it |
334 | could just as easily be used to write an offline report generator or a |
335 | command-line tool. |
336 | |
337 | To show how to define models, again we'll use an already-existing base |
338 | class, this time for L<DBIx::Class>: L<Catalyst::Model::DBIC::Schema>. |
339 | We'll also need L<DBIx::Class::Schema::Loader>. |
340 | |
341 | But first, we need a database. |
342 | |
343 | -- myapp.sql |
344 | CREATE TABLE foo ( |
345 | id INTEGER PRIMARY KEY, |
346 | data TEXT |
347 | ); |
348 | |
349 | CREATE TABLE bar ( |
350 | id INTEGER PRIMARY KEY, |
351 | foo INTEGER REFERENCES foo, |
352 | data TEXT |
353 | ); |
354 | |
355 | INSERT INTO foo (data) VALUES ('TEST!'); |
356 | |
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357 | % sqlite3 /tmp/myapp.db < myapp.sql |
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358 | |
359 | Now we can create a DBIC::Schema model for this database. |
360 | |
361 | script/myapp_create.pl model MyModel DBIC::Schema MySchema create=static 'dbi:SQLite:/tmp/myapp.db' |
362 | |
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363 | L<DBIx::Class::Schema::Loader> can automaticall load table layouts and |
364 | relationships, and convert them into a static schema definition |
365 | C<MySchema>, which you can edit later. |
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366 | |
367 | Use the stash to pass data to your templates. |
368 | |
369 | We add the following to MyApp/Controller/Root.pm |
370 | |
371 | sub view : Global { |
372 | my ( $self, $c, $id ) = @_; |
373 | |
374 | $c->stash->{item} = $c->model('MyModel::Foo')->find($id); |
375 | } |
376 | |
377 | 1; |
378 | |
379 | sub end : Private { |
380 | my ( $self, $c ) = @_; |
381 | |
382 | $c->stash->{template} ||= 'index.tt'; |
383 | $c->forward( $c->view('TT') ); |
384 | } |
385 | |
386 | We then create a new template file "root/index.tt" containing: |
387 | |
388 | The Id's data is [% item.data %] |
389 | |
390 | Models do not have to be part of your Catalyst application; you |
391 | can always call an outside module that serves as your Model: |
392 | |
393 | # in a Controller |
394 | sub list : Local { |
395 | my ( $self, $c ) = @_; |
396 | |
397 | $c->stash->{template} = 'list.tt'; |
398 | |
399 | use Some::Outside::Database::Module; |
400 | my @records = Some::Outside::Database::Module->search({ |
401 | artist => 'Led Zeppelin', |
402 | }); |
403 | |
404 | $c->stash->{records} = \@records; |
405 | } |
406 | |
407 | But by using a Model that is part of your Catalyst application, you |
408 | gain several things: you don't have to C<use> each component, Catalyst |
409 | will find and load it automatically at compile-time; you can |
410 | C<forward> to the module, which can only be done to Catalyst |
411 | components. Only Catalyst components can be fetched with |
412 | C<$c-E<gt>model('SomeModel')>. |
413 | |
414 | Happily, since many people have existing Model classes that they |
415 | would like to use with Catalyst (or, conversely, they want to |
416 | write Catalyst models that can be used outside of Catalyst, e.g. |
417 | in a cron job), it's trivial to write a simple component in |
418 | Catalyst that slurps in an outside Model: |
419 | |
420 | package MyApp::Model::DB; |
421 | use base qw/Catalyst::Model::DBIC::Schema/; |
422 | __PACKAGE__->config( |
423 | schema_class => 'Some::DBIC::Schema', |
424 | connect_info => ['dbi:SQLite:foo.db', '', '', {AutoCommit=>1}] |
425 | ); |
426 | 1; |
427 | |
428 | and that's it! Now C<Some::DBIC::Schema> is part of your |
429 | Cat app as C<MyApp::Model::DB>. |
430 | |
431 | Within Catalyst, the common approach to writing a model for your |
432 | application is wrapping a generic model (e.g. L<DBIx::Class::Schema>, a |
433 | bunch of XMLs, or anything really) with an object that contains |
434 | configuration data, convenience methods, and so forth. Thus you |
435 | will in effect have two models - a wrapper model that knows something |
436 | about Catalyst and your web application, and a generic model that is |
437 | totally independent of these needs. |
438 | |
439 | Technically, within Catalyst a model is a B<component> - an instance of |
440 | the model's class belonging to the application. It is important to |
441 | stress that the lifetime of these objects is per application, not per |
442 | request. |
443 | |
444 | While the model base class (L<Catalyst::Model>) provides things like |
445 | C<config> to better integrate the model into the application, sometimes |
446 | this is not enough, and the model requires access to C<$c> itself. |
447 | |
448 | Situations where this need might arise include: |
449 | |
450 | =over 4 |
451 | |
452 | =item * |
453 | |
454 | Interacting with another model |
455 | |
456 | =item * |
457 | |
458 | Using per-request data to control behavior |
459 | |
460 | =item * |
461 | |
462 | Using plugins from a Model (for example L<Catalyst::Plugin::Cache>). |
463 | |
464 | =back |
465 | |
466 | From a style perspective it's usually considered bad form to make your |
467 | model "too smart" about things - it should worry about business logic |
468 | and leave the integration details to the controllers. If, however, you |
469 | find that it does not make sense at all to use an auxillary controller |
470 | around the model, and the model's need to access C<$c> cannot be |
471 | sidestepped, there exists a power tool called L</ACCEPT_CONTEXT>. |
472 | |
473 | =head4 Controllers |
474 | |
475 | Multiple controllers are a good way to separate logical domains of your |
476 | application. |
477 | |
478 | package MyApp::Controller::Login; |
479 | |
480 | use base qw/Catalyst::Controller/; |
481 | |
482 | sub login : Path("login") { } |
483 | sub new_password : Path("new-password") { } |
484 | sub logout : Path("logout") { } |
485 | |
486 | package MyApp::Controller::Catalog; |
487 | |
488 | use base qw/Catalyst::Controller/; |
489 | |
490 | sub view : Local { } |
491 | sub list : Local { } |
492 | |
493 | package MyApp::Controller::Cart; |
494 | |
495 | use base qw/Catalyst::Controller/; |
496 | |
497 | sub add : Local { } |
498 | sub update : Local { } |
499 | sub order : Local { } |
500 | |
501 | Note that you can also supply attributes via the Controller's config so |
502 | long as you have at least one attribute on a subref to be exported |
503 | (:Action is commonly used for this) - for example the following is |
504 | equivalent to the same controller above: |
505 | |
506 | package MyApp::Controller::Login; |
507 | |
508 | use base qw/Catalyst::Controller/; |
509 | |
510 | __PACKAGE__->config( |
511 | actions => { |
512 | 'sign_in' => { Path => 'sign-in' }, |
513 | 'new_password' => { Path => 'new-password' }, |
514 | 'sign_out' => { Path => 'sign-out' }, |
515 | }, |
516 | ); |
517 | |
518 | sub sign_in : Action { } |
519 | sub new_password : Action { } |
520 | sub sign_out : Action { } |
521 | |
522 | =head3 ACCEPT_CONTEXT |
523 | |
524 | Whenever you call $c->component("Foo") you get back an object - the |
525 | instance of the model. If the component supports the C<ACCEPT_CONTEXT> |
526 | method instead of returning the model itself, the return value of C<< |
527 | $model->ACCEPT_CONTEXT( $c ) >> will be used. |
528 | |
529 | This means that whenever your model/view/controller needs to talk to C<$c> it |
530 | gets a chance to do this when it's needed. |
531 | |
532 | A typical C<ACCEPT_CONTEXT> method will either clone the model and return one |
533 | with the context object set, or it will return a thin wrapper that contains |
534 | C<$c> and delegates to the per-application model object. |
535 | |
536 | A typical C<ACCEPT_CONTEXT> method could look like this: |
537 | |
538 | sub ACCEPT_CONTEXT { |
539 | my ( $self, $c, @extra_arguments ) = @_; |
540 | bless { %$self, c => $c }, ref($self); |
541 | } |
542 | |
543 | effectively treating $self as a B<prototype object> that gets a new parameter. |
544 | C<@extra_arguments> comes from any trailing arguments to |
545 | C<< $c->component( $bah, @extra_arguments ) >> (or C<< $c->model(...) >>, |
546 | C<< $c->view(...) >> etc). |
547 | |
548 | The life time of this value is B<per usage>, and not per request. To make this |
549 | per request you can use the following technique: |
550 | |
551 | Add a field to C<$c>, like C<my_model_instance>. Then write your |
552 | C<ACCEPT_CONTEXT> method to look like this: |
553 | |
554 | sub ACCEPT_CONTEXT { |
555 | my ( $self, $c ) = @_; |
556 | |
557 | if ( my $per_request = $c->my_model_instance ) { |
558 | return $per_request; |
559 | } else { |
560 | my $new_instance = bless { %$self, c => $c }, ref($self); |
561 | Scalar::Util::weaken($new_instance->{c}); # or we have a circular reference |
562 | $c->my_model_instance( $new_instance ); |
563 | return $new_instance; |
564 | } |
565 | } |
566 | |
567 | =head3 Application Class |
568 | |
569 | In addition to the Model, View, and Controller components, there's a |
570 | single class that represents your application itself. This is where you |
571 | configure your application, load plugins, and extend Catalyst. |
572 | |
573 | package MyApp; |
574 | |
575 | use strict; |
ca7528df |
576 | use parent qw/Catalyst/; |
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577 | use Catalyst qw/-Debug ConfigLoader Static::Simple/; |
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578 | MyApp->config( |
579 | name => 'My Application', |
580 | |
581 | # You can put anything else you want in here: |
582 | my_configuration_variable => 'something', |
583 | ); |
584 | 1; |
585 | |
586 | In older versions of Catalyst, the application class was where you put |
587 | global actions. However, as of version 5.66, the recommended practice is |
588 | to place such actions in a special Root controller (see L</Actions>, |
589 | below), to avoid namespace collisions. |
590 | |
591 | =over 4 |
592 | |
593 | =item * B<name> |
594 | |
595 | The name of your application. |
596 | |
597 | =back |
598 | |
599 | Optionally, you can specify a B<root> parameter for templates and static |
600 | data. If omitted, Catalyst will try to auto-detect the directory's |
601 | location. You can define as many parameters as you want for plugins or |
602 | whatever you need. You can access them anywhere in your application via |
603 | C<$context-E<gt>config-E<gt>{$param_name}>. |
604 | |
605 | =head3 Context |
606 | |
607 | Catalyst automatically blesses a Context object into your application |
608 | class and makes it available everywhere in your application. Use the |
609 | Context to directly interact with Catalyst and glue your L</Components> |
610 | together. For example, if you need to use the Context from within a |
611 | Template Toolkit template, it's already there: |
612 | |
613 | <h1>Welcome to [% c.config.name %]!</h1> |
614 | |
615 | As illustrated in our URL-to-Action dispatching example, the Context is |
616 | always the second method parameter, behind the Component object |
617 | reference or class name itself. Previously we called it C<$context> for |
618 | clarity, but most Catalyst developers just call it C<$c>: |
619 | |
620 | sub hello : Global { |
621 | my ( $self, $c ) = @_; |
622 | $c->res->body('Hello World!'); |
623 | } |
624 | |
625 | The Context contains several important objects: |
626 | |
627 | =over 4 |
628 | |
629 | =item * L<Catalyst::Request> |
630 | |
631 | $c->request |
632 | $c->req # alias |
633 | |
634 | The request object contains all kinds of request-specific information, like |
635 | query parameters, cookies, uploads, headers, and more. |
636 | |
637 | $c->req->params->{foo}; |
638 | $c->req->cookies->{sessionid}; |
639 | $c->req->headers->content_type; |
640 | $c->req->base; |
641 | $c->req->uri_with( { page = $pager->next_page } ); |
642 | |
643 | =item * L<Catalyst::Response> |
644 | |
645 | $c->response |
646 | $c->res # alias |
647 | |
648 | The response is like the request, but contains just response-specific |
649 | information. |
650 | |
651 | $c->res->body('Hello World'); |
652 | $c->res->status(404); |
653 | $c->res->redirect('http://oook.de'); |
654 | |
655 | =item * L<Catalyst::Config> |
656 | |
657 | $c->config |
658 | $c->config->{root}; |
659 | $c->config->{name}; |
660 | |
661 | =item * L<Catalyst::Log> |
662 | |
663 | $c->log |
664 | $c->log->debug('Something happened'); |
665 | $c->log->info('Something you should know'); |
666 | |
667 | =item * B<Stash> |
668 | |
669 | $c->stash |
670 | $c->stash->{foo} = 'bar'; |
671 | $c->stash->{baz} = {baz => 'qox'}; |
672 | $c->stash->{fred} = [qw/wilma pebbles/]; |
673 | |
674 | and so on. |
675 | |
676 | =back |
677 | |
678 | The last of these, the stash, is a universal hash for sharing data among |
679 | application components. For an example, we return to our 'hello' action: |
680 | |
681 | sub hello : Global { |
682 | my ( $self, $c ) = @_; |
683 | $c->stash->{message} = 'Hello World!'; |
684 | $c->forward('show_message'); |
685 | } |
686 | |
687 | sub show_message : Private { |
688 | my ( $self, $c ) = @_; |
689 | $c->res->body( $c->stash->{message} ); |
690 | } |
691 | |
692 | Note that the stash should be used only for passing data in an |
693 | individual request cycle; it gets cleared at a new request. If you need |
694 | to maintain persistent data, use a session. See |
695 | L<Catalyst::Plugin::Session> for a comprehensive set of |
696 | Catalyst-friendly session-handling tools. |
697 | |
698 | =head3 Actions |
699 | |
700 | A Catalyst controller is defined by its actions. An action is a |
701 | subroutine with a special attribute. You've already seen some examples |
702 | of actions in this document. The URL (for example |
703 | http://localhost.3000/foo/bar) consists of two parts, the base |
704 | (http://localhost:3000/ in this example) and the path (foo/bar). Please |
705 | note that the trailing slash after the hostname[:port] always belongs to |
706 | base and not to the action. |
707 | |
708 | =over 4 |
709 | |
710 | =item * B<Application Wide Actions> |
711 | |
712 | Actions which are called at the root level of the application |
713 | (e.g. http://localhost:3000/ ) go in MyApp::Controller::Root, like |
714 | this: |
715 | |
716 | package MyApp::Controller::Root; |
717 | use base 'Catalyst::Controller'; |
718 | # Sets the actions in this controller to be registered with no prefix |
719 | # so they function identically to actions created in MyApp.pm |
720 | __PACKAGE__->config->{namespace} = ''; |
4299d9f5 |
721 | sub default : Path { |
cb93c9d7 |
722 | my ( $self, $context ) = @_; |
4299d9f5 |
723 | $context->response->status(404); |
724 | $context->response->body('404 not found'); |
cb93c9d7 |
725 | } |
726 | 1; |
727 | |
728 | =back |
729 | |
730 | =head4 Action types |
731 | |
732 | Catalyst supports several types of actions: |
733 | |
734 | =over 4 |
735 | |
736 | =item * B<Literal> (B<Path> actions) |
737 | |
738 | package MyApp::Controller::My::Controller; |
739 | sub bar : Path('foo/bar') { } |
740 | |
741 | Literal C<Path> actions will act relative to their current |
742 | namespace. The above example matches only |
743 | http://localhost:3000/my/controller/foo/bar. If you start your path with |
744 | a forward slash, it will match from the root. Example: |
745 | |
746 | package MyApp::Controller::My::Controller; |
747 | sub bar : Path('/foo/bar') { } |
748 | |
749 | Matches only http://localhost:3000/foo/bar. |
750 | |
751 | package MyApp::Controller::My::Controller; |
752 | sub bar : Path { } |
753 | |
754 | By leaving the C<Path> definition empty, it will match on the namespace |
755 | root. The above code matches http://localhost:3000/my/controller. |
756 | |
757 | =item * B<Regex> |
758 | |
759 | sub bar : Regex('^item(\d+)/order(\d+)$') { } |
760 | |
761 | Matches any URL that matches the pattern in the action key, e.g. |
762 | http://localhost:3000/item23/order42. The '' around the regexp is |
763 | optional, but perltidy likes it. :) |
764 | |
765 | Regex matches act globally, i.e. without reference to the namespace from |
766 | which it is called, so that a C<bar> method in the |
767 | C<MyApp::Controller::Catalog::Order::Process> namespace won't match any |
768 | form of C<bar>, C<Catalog>, C<Order>, or C<Process> unless you |
769 | explicitly put this in the regex. To achieve the above, you should |
770 | consider using a C<LocalRegex> action. |
771 | |
772 | =item * B<LocalRegex> |
773 | |
774 | sub bar : LocalRegex('^widget(\d+)$') { } |
775 | |
776 | LocalRegex actions act locally. If you were to use C<bar> in |
777 | C<MyApp::Controller::Catalog>, the above example would match urls like |
778 | http://localhost:3000/catalog/widget23. |
779 | |
780 | If you omit the "C<^>" from your regex, then it will match any depth |
781 | from the controller and not immediately off of the controller name. The |
782 | following example differs from the above code in that it will match |
783 | http://localhost:3000/catalog/foo/widget23 as well. |
784 | |
785 | package MyApp::Controller::Catalog; |
786 | sub bar : LocalRegex('widget(\d+)$') { } |
787 | |
788 | For both LocalRegex and Regex actions, if you use capturing parentheses |
789 | to extract values within the matching URL, those values are available in |
790 | the C<$c-E<gt>req-E<gt>captures> array. In the above example, "widget23" |
791 | would capture "23" in the above example, and |
792 | C<$c-E<gt>req-E<gt>captures-E<gt>[0]> would be "23". If you want to pass |
793 | arguments at the end of your URL, you must use regex action keys. See |
794 | L</URL Path Handling> below. |
795 | |
796 | =item * B<Top-level> (B<Global>) |
797 | |
798 | package MyApp::Controller::Foo; |
799 | sub foo : Global { } |
800 | |
801 | Matches http://localhost:3000/foo. The function name is mapped |
802 | directly to the application base. You can provide an equivalent |
803 | function in this case by doing the following: |
804 | |
805 | package MyApp::Controller::Root |
806 | sub foo : Local { } |
807 | |
808 | =item * B<Namespace-Prefixed> (B<Local>) |
809 | |
810 | package MyApp::Controller::My::Controller; |
811 | sub foo : Local { } |
812 | |
813 | Matches http://localhost:3000/my/controller/foo. |
814 | |
815 | This action type indicates that the matching URL must be prefixed with a |
816 | modified form of the component's class (package) name. This modified |
817 | class name excludes the parts that have a pre-defined meaning in |
818 | Catalyst ("MyApp::Controller" in the above example), replaces "::" with |
819 | "/", and converts the name to lower case. See L</Components> for a full |
820 | explanation of the pre-defined meaning of Catalyst component class |
821 | names. |
822 | |
4299d9f5 |
823 | Note that actions with the C< :Local > attribute are equivalent to the |
824 | <:Path('action_name') > so sub foo : Local { } is equivalent to - |
825 | |
826 | sub foo : Path('foo') { } |
827 | |
cb93c9d7 |
828 | =item * B<Chained> |
829 | |
830 | Catalyst also provides a method to build and dispatch chains of actions, |
831 | like |
832 | |
833 | sub catalog : Chained : CaptureArgs(1) { |
834 | my ( $self, $c, $arg ) = @_; |
835 | ... |
836 | } |
837 | |
838 | sub item : Chained('catalog') : Args(1) { |
839 | my ( $self, $c, $arg ) = @_; |
840 | ... |
841 | } |
842 | |
843 | to handle a C</catalog/*/item/*> path. For further information about this |
844 | dispatch type, please see L<Catalyst::DispatchType::Chained>. |
845 | |
846 | =item * B<Private> |
847 | |
848 | sub foo : Private { } |
849 | |
850 | Matches no URL, and cannot be executed by requesting a URL that |
09f13e1d |
851 | corresponds to the action key. Catalyst's :Private attribute is |
852 | exclusive and doesn't work with other attributes (so will not work |
853 | combined with Path or Chained attributes). With the exception of the |
854 | C< index >, C< auto > and C< default > actions, Private actions can |
855 | only be executed from inside a Catalyst application, by calling the |
856 | C<forward> or C<detach> methods: |
cb93c9d7 |
857 | |
858 | $c->forward('foo'); |
09f13e1d |
859 | # or |
860 | $c->detach('foo'); |
cb93c9d7 |
861 | |
862 | See L</Flow Control> for a full explanation of C<forward>. Note that, as |
863 | discussed there, when forwarding from another component, you must use |
864 | the absolute path to the method, so that a private C<bar> method in your |
865 | C<MyApp::Controller::Catalog::Order::Process> controller must, if called |
866 | from elsewhere, be reached with |
867 | C<$c-E<gt>forward('/catalog/order/process/bar')>. |
868 | |
869 | =item * B<Args> |
870 | |
871 | Args is not an action type per se, but an action modifier - it adds a |
872 | match restriction to any action it's provided to, requiring only as many |
873 | path parts as are specified for the action to be valid - for example in |
874 | MyApp::Controller::Foo, |
875 | |
876 | sub bar :Local |
877 | |
878 | would match any URL starting /foo/bar/. To restrict this you can do |
879 | |
880 | sub bar :Local :Args(1) |
881 | |
882 | to only match /foo/bar/*/ |
883 | |
884 | =back |
885 | |
886 | B<Note:> After seeing these examples, you probably wonder what the point |
887 | is of defining names for regex and path actions. Every public action is |
888 | also a private one, so you have one unified way of addressing components |
889 | in your C<forward>s. |
890 | |
891 | =head4 Built-in Private Actions |
892 | |
893 | In response to specific application states, Catalyst will automatically |
894 | call these built-in private actions in your application class: |
895 | |
896 | =over 4 |
897 | |
4299d9f5 |
898 | =item * B<default : Path> |
cb93c9d7 |
899 | |
900 | Called when no other action matches. Could be used, for example, for |
901 | displaying a generic frontpage for the main app, or an error page for |
955bdf3d |
902 | individual controllers. B<Note>: in older Catalyst applications you |
903 | will see C<default : Private> which is roughly speaking equivalent. |
cb93c9d7 |
904 | |
cb93c9d7 |
905 | |
4299d9f5 |
906 | =item * B<index : Path : Args (0) > |
cb93c9d7 |
907 | |
4299d9f5 |
908 | C<index> is much like C<default> except that it takes no arguments and |
909 | it is weighted slightly higher in the matching process. It is useful |
910 | as a static entry point to a controller, e.g. to have a static welcome |
911 | page. Note that it's also weighted higher than Path. Actually the sub |
912 | name C<index> can be called anything you want. The sub attributes are |
955bdf3d |
913 | what determines the behaviour of the action. B<Note>: in older |
914 | Catalyst applications, you will see C<index : Private> used, which is |
915 | roughly speaking equivalent. |
cb93c9d7 |
916 | |
917 | =item * B<begin : Private> |
918 | |
919 | Called at the beginning of a request, before any matching actions are |
920 | called. |
921 | |
922 | =item * B<end : Private> |
923 | |
924 | Called at the end of a request, after all matching actions are called. |
925 | |
926 | =back |
927 | |
928 | =head4 Built-in actions in controllers/autochaining |
929 | |
930 | Package MyApp::Controller::Foo; |
931 | sub begin : Private { } |
4299d9f5 |
932 | sub default : Path { } |
cb93c9d7 |
933 | sub auto : Private { } |
934 | |
935 | You can define built-in private actions within your controllers as |
936 | well. The actions will override the ones in less-specific controllers, |
937 | or your application class. In other words, for each of the three |
938 | built-in private actions, only one will be run in any request |
939 | cycle. Thus, if C<MyApp::Controller::Catalog::begin> exists, it will be |
940 | run in place of C<MyApp::begin> if you're in the C<catalog> namespace, |
941 | and C<MyApp::Controller::Catalog::Order::begin> would override this in |
942 | turn. |
943 | |
944 | =over 4 |
945 | |
946 | =item * B<auto : Private> |
947 | |
948 | In addition to the normal built-in actions, you have a special action |
949 | for making chains, C<auto>. Such C<auto> actions will be run after any |
950 | C<begin>, but before your action is processed. Unlike the other |
951 | built-ins, C<auto> actions I<do not> override each other; they will be |
952 | called in turn, starting with the application class and going through to |
953 | the I<most> specific class. I<This is the reverse of the order in which |
954 | the normal built-ins override each other>. |
955 | |
956 | =back |
957 | |
958 | Here are some examples of the order in which the various built-ins |
959 | would be called: |
960 | |
961 | =over 4 |
962 | |
963 | =item for a request for C</foo/foo> |
964 | |
965 | MyApp::begin |
966 | MyApp::auto |
967 | MyApp::Controller::Foo::default # in the absence of MyApp::Controller::Foo::Foo |
968 | MyApp::end |
969 | |
970 | =item for a request for C</foo/bar/foo> |
971 | |
972 | MyApp::Controller::Foo::Bar::begin |
973 | MyApp::auto |
974 | MyApp::Controller::Foo::auto |
975 | MyApp::Controller::Foo::Bar::auto |
976 | MyApp::Controller::Foo::Bar::default # for MyApp::Controller::Foo::Bar::foo |
977 | MyApp::Controller::Foo::Bar::end |
978 | |
979 | =back |
980 | |
981 | The C<auto> action is also distinguished by the fact that you can break |
982 | out of the processing chain by returning 0. If an C<auto> action returns |
983 | 0, any remaining actions will be skipped, except for C<end>. So, for the |
984 | request above, if the first auto returns false, the chain would look |
985 | like this: |
986 | |
987 | =over 4 |
988 | |
989 | =item for a request for C</foo/bar/foo> where first C<auto> returns |
990 | false |
991 | |
992 | MyApp::Controller::Foo::Bar::begin |
993 | MyApp::auto |
994 | MyApp::Controller::Foo::Bar::end |
995 | |
996 | =back |
997 | |
998 | An example of why one might use this is an authentication action: you |
999 | could set up a C<auto> action to handle authentication in your |
1000 | application class (which will always be called first), and if |
1001 | authentication fails, returning 0 would skip any remaining methods |
1002 | for that URL. |
1003 | |
1004 | B<Note:> Looking at it another way, C<auto> actions have to return a |
1005 | true value to continue processing! You can also C<die> in the auto |
1006 | action; in that case, the request will go straight to the finalize |
1007 | stage, without processing further actions. |
1008 | |
1009 | =head4 URL Path Handling |
1010 | |
1011 | You can pass variable arguments as part of the URL path, separated with |
1012 | forward slashes (/). If the action is a Regex or LocalRegex, the '$' anchor |
1013 | must be used. For example, suppose you want to handle C</foo/$bar/$baz>, |
1014 | where C<$bar> and C<$baz> may vary: |
1015 | |
1016 | sub foo : Regex('^foo$') { my ($self, $context, $bar, $baz) = @_; } |
1017 | |
1018 | But what if you also defined actions for C</foo/boo> and C</foo/boo/hoo>? |
1019 | |
1020 | sub boo : Path('foo/boo') { .. } |
1021 | sub hoo : Path('foo/boo/hoo') { .. } |
1022 | |
1023 | Catalyst matches actions in most specific to least specific order: |
1024 | |
1025 | /foo/boo/hoo |
1026 | /foo/boo |
1027 | /foo # might be /foo/bar/baz but won't be /foo/boo/hoo |
1028 | |
1029 | So Catalyst would never mistakenly dispatch the first two URLs to the |
1030 | '^foo$' action. |
1031 | |
1032 | If a Regex or LocalRegex action doesn't use the '$' anchor, the action will |
1033 | still match a URL containing arguments, however the arguments won't be |
1034 | available via C<@_>. |
1035 | |
1036 | =head4 Parameter Processing |
1037 | |
1038 | Parameters passed in the URL query string are handled with methods in |
1039 | the L<Catalyst::Request> class. The C<param> method is functionally |
1040 | equivalent to the C<param> method of C<CGI.pm> and can be used in |
1041 | modules that require this. |
1042 | |
1043 | # http://localhost:3000/catalog/view/?category=hardware&page=3 |
1044 | my $category = $c->req->param('category'); |
1045 | my $current_page = $c->req->param('page') || 1; |
1046 | |
1047 | # multiple values for single parameter name |
1048 | my @values = $c->req->param('scrolling_list'); |
1049 | |
1050 | # DFV requires a CGI.pm-like input hash |
1051 | my $results = Data::FormValidator->check($c->req->params, \%dfv_profile); |
1052 | |
1053 | =head3 Flow Control |
1054 | |
1055 | You control the application flow with the C<forward> method, which |
1056 | accepts the key of an action to execute. This can be an action in the |
1057 | same or another Catalyst controller, or a Class name, optionally |
1058 | followed by a method name. After a C<forward>, the control flow will |
1059 | return to the method from which the C<forward> was issued. |
1060 | |
1061 | A C<forward> is similar to a method call. The main differences are that |
1062 | it wraps the call in an C<eval> to allow exception handling; it |
1063 | automatically passes along the context object (C<$c> or C<$context>); |
1064 | and it allows profiling of each call (displayed in the log with |
1065 | debugging enabled). |
1066 | |
1067 | sub hello : Global { |
1068 | my ( $self, $c ) = @_; |
1069 | $c->stash->{message} = 'Hello World!'; |
1070 | $c->forward('check_message'); # $c is automatically included |
1071 | } |
1072 | |
1073 | sub check_message : Private { |
1074 | my ( $self, $c ) = @_; |
1075 | return unless $c->stash->{message}; |
1076 | $c->forward('show_message'); |
1077 | } |
1078 | |
1079 | sub show_message : Private { |
1080 | my ( $self, $c ) = @_; |
1081 | $c->res->body( $c->stash->{message} ); |
1082 | } |
1083 | |
1084 | A C<forward> does not create a new request, so your request object |
1085 | (C<$c-E<gt>req>) will remain unchanged. This is a key difference between |
1086 | using C<forward> and issuing a redirect. |
1087 | |
1088 | You can pass new arguments to a C<forward> by adding them |
1089 | in an anonymous array. In this case C<$c-E<gt>req-E<gt>args> |
1090 | will be changed for the duration of the C<forward> only; upon |
1091 | return, the original value of C<$c-E<gt>req-E<gt>args> will |
1092 | be reset. |
1093 | |
1094 | sub hello : Global { |
1095 | my ( $self, $c ) = @_; |
1096 | $c->stash->{message} = 'Hello World!'; |
1097 | $c->forward('check_message',[qw/test1/]); |
1098 | # now $c->req->args is back to what it was before |
1099 | } |
1100 | |
1101 | sub check_message : Private { |
1102 | my ( $self, $c ) = @_; |
1103 | my $first_argument = $c->req->args->[0]; # now = 'test1' |
1104 | # do something... |
1105 | } |
1106 | |
1107 | As you can see from these examples, you can just use the method name as |
1108 | long as you are referring to methods in the same controller. If you want |
1109 | to forward to a method in another controller, or the main application, |
1110 | you will have to refer to the method by absolute path. |
1111 | |
1112 | $c->forward('/my/controller/action'); |
1113 | $c->forward('/default'); # calls default in main application |
1114 | |
1115 | Here are some examples of how to forward to classes and methods. |
1116 | |
1117 | sub hello : Global { |
1118 | my ( $self, $c ) = @_; |
1119 | $c->forward(qw/MyApp::Model::Hello say_hello/); |
1120 | } |
1121 | |
1122 | sub bye : Global { |
1123 | my ( $self, $c ) = @_; |
1124 | $c->forward('MyApp::Model::Hello'); # no method: will try 'process' |
1125 | } |
1126 | |
1127 | package MyApp::Model::Hello; |
1128 | |
1129 | sub say_hello { |
1130 | my ( $self, $c ) = @_; |
1131 | $c->res->body('Hello World!'); |
1132 | } |
1133 | |
1134 | sub process { |
1135 | my ( $self, $c ) = @_; |
1136 | $c->res->body('Goodbye World!'); |
1137 | } |
1138 | |
1139 | Note that C<forward> returns to the calling action and continues |
1140 | processing after the action finishes. If you want all further processing |
1141 | in the calling action to stop, use C<detach> instead, which will execute |
1142 | the C<detach>ed action and not return to the calling sub. In both cases, |
1143 | Catalyst will automatically try to call process() if you omit the |
1144 | method. |
1145 | |
1146 | |
1147 | =head3 Testing |
1148 | |
1149 | Catalyst has a built-in http server for testing or local |
1150 | deployment. (Later, you can easily use a more powerful server, for |
1151 | example Apache/mod_perl or FastCGI, in a production environment.) |
1152 | |
1153 | Start your application on the command line... |
1154 | |
1155 | script/myapp_server.pl |
1156 | |
1157 | ...then visit http://localhost:3000/ in a browser to view the output. |
1158 | |
1159 | You can also do it all from the command line: |
1160 | |
1161 | script/myapp_test.pl http://localhost/ |
1162 | |
1163 | Catalyst has a number of tools for actual regression testing of |
1164 | applications. The helper scripts will automatically generate basic tests |
1165 | that can be extended as you develop your project. To write your own |
1166 | comprehensive test scripts, L<Test::WWW::Mechanize::Catalyst> is an |
1167 | invaluable tool. |
1168 | |
1169 | For more testing ideas, see L<Catalyst::Manual::Tutorial::Testing>. |
1170 | |
1171 | Have fun! |
1172 | |
1173 | =head1 SEE ALSO |
1174 | |
1175 | =over 4 |
1176 | |
1177 | =item * L<Catalyst::Manual::About> |
1178 | |
1179 | =item * L<Catalyst::Manual::Tutorial> |
1180 | |
1181 | =item * L<Catalyst> |
1182 | |
1183 | =back |
1184 | |
1185 | =head1 SUPPORT |
1186 | |
1187 | IRC: |
1188 | |
1189 | Join #catalyst on irc.perl.org. |
1190 | Join #catalyst-dev on irc.perl.org to help with development. |
1191 | |
1192 | Mailing lists: |
1193 | |
392906f2 |
1194 | http://lists.scsys.co.uk/mailman/listinfo/catalyst |
1195 | http://lists.scsys.co.uk/mailman/listinfo/catalyst-dev |
cb93c9d7 |
1196 | |
1197 | =head1 AUTHOR |
1198 | |
1199 | Sebastian Riedel, C<sri@oook.de> |
1200 | David Naughton, C<naughton@umn.edu> |
1201 | Marcus Ramberg, C<mramberg@cpan.org> |
1202 | Jesse Sheidlower, C<jester@panix.com> |
1203 | Danijel Milicevic, C<me@danijel.de> |
1204 | Kieren Diment, C<kd@totaldatasolution.com> |
1205 | Yuval Kogman, C<nothingmuch@woobling.org> |
1206 | |
1207 | =head1 COPYRIGHT |
1208 | |
1209 | This program is free software. You can redistribute it and/or modify it |
1210 | under the same terms as Perl itself. |