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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 |
792ad331 |
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 | |
100 | sub hello : Global { |
101 | my ( $self, $context ) = @_; |
102 | $context->response->body('Hello World!'); |
103 | } |
104 | |
105 | Now http://localhost:3000/hello prints "Hello World!". |
106 | |
107 | =item * B<Support for CGI, mod_perl, Apache::Request, FastCGI> |
108 | |
109 | Use L<Catalyst::Engine::Apache> or L<Catalyst::Engine::CGI>. Other |
110 | engines are also available. |
111 | |
112 | =back |
113 | |
114 | =head3 Simplicity |
115 | |
116 | The best part is that Catalyst implements all this flexibility in a very |
117 | simple way. |
118 | |
119 | =over 4 |
120 | |
121 | =item * B<Building Block Interface> |
122 | |
123 | Components interoperate very smoothly. For example, Catalyst |
124 | automatically makes a L</Context> object available to every |
125 | component. Via the context, you can access the request object, share |
126 | data between components, and control the flow of your |
127 | application. Building a Catalyst application feels a lot like snapping |
128 | together toy building blocks, and everything just works. |
129 | |
130 | =item * B<Component Auto-Discovery> |
131 | |
132 | No need to C<use> all of your components. Catalyst automatically finds |
133 | and loads them. |
134 | |
135 | =item * B<Pre-Built Components for Popular Modules> |
136 | |
137 | See L<Catalyst::Model::DBIC::Schema> for L<DBIx::Class>, or |
138 | L<Catalyst::View::TT> for L<Template Toolkit|Template>. |
139 | |
140 | =item * B<Built-in Test Framework> |
141 | |
142 | Catalyst comes with a built-in, lightweight http server and test |
143 | framework, making it easy to test applications from the web browser, |
144 | and the command line. |
145 | |
146 | =item * B<Helper Scripts> |
147 | |
148 | Catalyst provides helper scripts to quickly generate running starter |
149 | code for components and unit tests. Install L<Catalyst::Devel> and see |
150 | L<Catalyst::Helper>. |
151 | |
152 | =back |
153 | |
154 | =head2 Quickstart |
155 | |
156 | Here's how to install Catalyst and get a simple application up and |
157 | running, using the helper scripts described above. |
158 | |
159 | =head3 Install |
160 | |
161 | Installation of Catalyst can be a time-consuming and frustrating |
162 | effort, due to its large number of dependencies. The easiest way |
163 | to get up and running is to use Matt Trout's C<cat-install> |
164 | script, from L<http://www.shadowcatsystems.co.uk/static/cat-install>, |
165 | and then install L<Catalyst::Devel>. |
166 | |
167 | # perl cat-install |
168 | # perl -MCPAN -e 'install Catalyst::Devel' |
169 | |
170 | =head3 Setup |
171 | |
172 | $ catalyst.pl MyApp |
173 | # output omitted |
174 | $ cd MyApp |
175 | $ script/myapp_create.pl controller Library::Login |
176 | |
177 | =head3 Run |
178 | |
179 | $ script/myapp_server.pl |
180 | |
181 | Now visit these locations with your favorite browser or user agent to see |
182 | Catalyst in action: |
183 | |
184 | (NOTE: Although we create a controller here, we don't actually use it. |
185 | Both of these URLs should take you to the welcome page.) |
186 | |
187 | |
188 | =over 4 |
189 | |
190 | =item http://localhost:3000/ |
191 | |
192 | =item http://localhost:3000/library/login/ |
193 | |
194 | =back |
195 | |
196 | =head2 How It Works |
197 | |
198 | Let's see how Catalyst works, by taking a closer look at the components |
199 | and other parts of a Catalyst application. |
200 | |
201 | =head3 Components |
202 | |
203 | Catalyst has an uncommonly flexible component system. You can define as |
204 | many L</Models>, L</Views>, and L</Controllers> as you like. As discussed |
205 | previously, the general idea is that the View is responsible for the |
206 | output of data to the user (typically via a web browser, but a View can |
207 | also generate PDFs or e-mails, for example); the Model is responsible |
208 | for providing data (typically from a relational database); and the |
209 | Controller is responsible for interacting with the user and deciding |
210 | how user input determines what actions the application takes. |
211 | |
212 | In the world of MVC, there are frequent discussions and disagreements |
213 | about the nature of each element - whether certain types of logic |
214 | belong in the Model or the Controller, etc. Catalyst's flexibility |
215 | means that this decision is entirely up to you, the programmer; |
216 | Catalyst doesn't enforce anything. See L<Catalyst::Manual::About> for |
217 | a general discussion of these issues. |
218 | |
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219 | Model, View and Controller components must inherit from L<Catalyst::Model>, |
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220 | L<Catalyst::View> and L<Catalyst::Controller>, respectively. These, in turn, inherit |
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221 | from L<Catalyst::Component> which provides a simple class structure and some |
222 | common class methods like C<config> and C<new> (constructor). |
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223 | |
224 | package MyApp::Controller::Catalog; |
225 | |
226 | use strict; |
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227 | use base 'Catalyst::Controller'; |
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228 | |
229 | __PACKAGE__->config( foo => 'bar' ); |
230 | |
231 | 1; |
232 | |
233 | You don't have to C<use> or otherwise register Models, Views, and |
234 | Controllers. Catalyst automatically discovers and instantiates them |
235 | when you call C<setup> in the main application. All you need to do is |
236 | put them in directories named for each Component type. You can use a |
237 | short alias for each one. |
238 | |
239 | =over 4 |
240 | |
241 | =item * B<MyApp/Model/> |
242 | |
243 | =item * B<MyApp/M/> |
244 | |
245 | =item * B<MyApp/View/> |
246 | |
247 | =item * B<MyApp/V/> |
248 | |
249 | =item * B<MyApp/Controller/> |
250 | |
251 | =item * B<MyApp/C/> |
252 | |
253 | =back |
254 | |
255 | In older versions of Catalyst, the recommended practice (and the one |
256 | automatically created by helper scripts) was to name the directories |
257 | C<M/>, C<V/>, and C<C/>. Though these still work, we now recommend |
258 | the use of the full names. |
259 | |
260 | =head4 Views |
261 | |
262 | To show how to define views, we'll use an already-existing base class for the |
263 | L<Template Toolkit|Template>, L<Catalyst::View::TT>. All we need to do is |
264 | inherit from this class: |
265 | |
266 | package MyApp::View::TT; |
267 | |
268 | use strict; |
269 | use base 'Catalyst::View::TT'; |
270 | |
271 | 1; |
272 | |
273 | (You can also generate this automatically by using the helper script: |
274 | |
275 | script/myapp_create.pl view TT TT |
276 | |
277 | where the first C<TT> tells the script that the name of the view should |
278 | be C<TT>, and the second that it should be a Template Toolkit view.) |
279 | |
280 | This gives us a process() method and we can now just do |
281 | $c->forward('MyApp::View::TT') to render our templates. The base class |
282 | makes process() implicit, so we don't have to say |
283 | C<$c-E<gt>forward(qw/MyApp::View::TT process/)>. |
284 | |
285 | sub hello : Global { |
286 | my ( $self, $c ) = @_; |
287 | $c->stash->{template} = 'hello.tt'; |
288 | } |
289 | |
290 | sub end : Private { |
291 | my ( $self, $c ) = @_; |
292 | $c->forward( $c->view('TT') ); |
293 | } |
294 | |
295 | You normally render templates at the end of a request, so it's a perfect |
296 | use for the global C<end> action. |
297 | |
298 | In practice, however, you would use a default C<end> action as supplied |
299 | by L<Catalyst::Action::RenderView>. |
300 | |
301 | Also, be sure to put the template under the directory specified in |
302 | C<$c-E<gt>config-E<gt>{root}>, or you'll end up looking at the debug |
303 | screen. |
304 | |
305 | =head4 Models |
306 | |
307 | Models are providers of data. This data could come from anywhere - a |
308 | search engine index, a spreadsheet, the file system - but typically a |
309 | Model represents a database table. The data source does not |
310 | intrinsically have much to do with web applications or Catalyst - it |
311 | could just as easily be used to write an offline report generator or a |
312 | command-line tool. |
313 | |
314 | To show how to define models, again we'll use an already-existing base |
315 | class, this time for L<DBIx::Class>: L<Catalyst::Model::DBIC::Schema>. |
316 | We'll also need L<DBIx::Class::Schema::Loader>. |
317 | |
318 | But first, we need a database. |
319 | |
320 | -- myapp.sql |
321 | CREATE TABLE foo ( |
322 | id INTEGER PRIMARY KEY, |
323 | data TEXT |
324 | ); |
325 | |
326 | CREATE TABLE bar ( |
327 | id INTEGER PRIMARY KEY, |
328 | foo INTEGER REFERENCES foo, |
329 | data TEXT |
330 | ); |
331 | |
332 | INSERT INTO foo (data) VALUES ('TEST!'); |
333 | |
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334 | % sqlite3 /tmp/myapp.db < myapp.sql |
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335 | |
336 | Now we can create a DBIC::Schema model for this database. |
337 | |
338 | script/myapp_create.pl model MyModel DBIC::Schema MySchema create=static 'dbi:SQLite:/tmp/myapp.db' |
339 | |
340 | L<DBIx::Class::Schema::Loader> automatically loads table layouts and |
341 | relationships, and converts them into a static schema definition C<MySchema>, |
342 | which you can edit later. |
343 | |
344 | Use the stash to pass data to your templates. |
345 | |
346 | We add the following to MyApp/Controller/Root.pm |
347 | |
348 | sub view : Global { |
349 | my ( $self, $c, $id ) = @_; |
350 | |
351 | $c->stash->{item} = $c->model('MyModel::Foo')->find($id); |
352 | } |
353 | |
354 | 1; |
355 | |
356 | sub end : Private { |
357 | my ( $self, $c ) = @_; |
358 | |
359 | $c->stash->{template} ||= 'index.tt'; |
360 | $c->forward( $c->view('TT') ); |
361 | } |
362 | |
363 | We then create a new template file "root/index.tt" containing: |
364 | |
365 | The Id's data is [% item.data %] |
366 | |
367 | Models do not have to be part of your Catalyst application; you |
368 | can always call an outside module that serves as your Model: |
369 | |
370 | # in a Controller |
371 | sub list : Local { |
372 | my ( $self, $c ) = @_; |
373 | |
374 | $c->stash->{template} = 'list.tt'; |
375 | |
376 | use Some::Outside::Database::Module; |
377 | my @records = Some::Outside::Database::Module->search({ |
378 | artist => 'Led Zeppelin', |
379 | }); |
380 | |
381 | $c->stash->{records} = \@records; |
382 | } |
383 | |
384 | But by using a Model that is part of your Catalyst application, you |
385 | gain several things: you don't have to C<use> each component, Catalyst |
386 | will find and load it automatically at compile-time; you can |
387 | C<forward> to the module, which can only be done to Catalyst |
388 | components. Only Catalyst components can be fetched with |
389 | C<$c-E<gt>model('SomeModel')>. |
390 | |
391 | Happily, since many people have existing Model classes that they |
392 | would like to use with Catalyst (or, conversely, they want to |
393 | write Catalyst models that can be used outside of Catalyst, e.g. |
394 | in a cron job), it's trivial to write a simple component in |
395 | Catalyst that slurps in an outside Model: |
396 | |
397 | package MyApp::Model::DB; |
398 | use base qw/Catalyst::Model::DBIC::Schema/; |
399 | __PACKAGE__->config( |
400 | schema_class => 'Some::DBIC::Schema', |
401 | connect_info => ['dbi:SQLite:foo.db', '', '', {AutoCommit=>1}] |
402 | ); |
403 | 1; |
404 | |
405 | and that's it! Now C<Some::DBIC::Schema> is part of your |
406 | Cat app as C<MyApp::Model::DB>. |
407 | |
408 | Within Catalyst, the common approach to writing a model for your |
409 | application is wrapping a generic model (e.g. L<DBIx::Class::Schema>, a |
410 | bunch of XMLs, or anything really) with an object that contains |
411 | configuration data, convenience methods, and so forth. Thus you |
412 | will in effect have two models - a wrapper model that knows something |
413 | about Catalyst and your web application, and a generic model that is |
414 | totally independent of these needs. |
415 | |
416 | Technically, within Catalyst a model is a B<component> - an instance of |
417 | the model's class belonging to the application. It is important to |
418 | stress that the lifetime of these objects is per application, not per |
419 | request. |
420 | |
421 | While the model base class (L<Catalyst::Model>) provides things like |
422 | C<config> to better integrate the model into the application, sometimes |
423 | this is not enough, and the model requires access to C<$c> itself. |
424 | |
425 | Situations where this need might arise include: |
426 | |
427 | =over 4 |
428 | |
429 | =item * |
430 | |
431 | Interacting with another model |
432 | |
433 | =item * |
434 | |
435 | Using per-request data to control behavior |
436 | |
437 | =item * |
438 | |
439 | Using plugins from a Model (for example L<Catalyst::Plugin::Cache>). |
440 | |
441 | =back |
442 | |
443 | From a style perspective it's usually considered bad form to make your |
444 | model "too smart" about things - it should worry about business logic |
445 | and leave the integration details to the controllers. If, however, you |
446 | find that it does not make sense at all to use an auxillary controller |
447 | around the model, and the model's need to access C<$c> cannot be |
448 | sidestepped, there exists a power tool called L</ACCEPT_CONTEXT>. |
449 | |
450 | =head4 Controllers |
451 | |
452 | Multiple controllers are a good way to separate logical domains of your |
453 | application. |
454 | |
455 | package MyApp::Controller::Login; |
456 | |
457 | use base qw/Catalyst::Controller/; |
458 | |
459 | sub login : Path("login") { } |
460 | sub new_password : Path("new-password") { } |
461 | sub logout : Path("logout") { } |
462 | |
463 | package MyApp::Controller::Catalog; |
464 | |
465 | use base qw/Catalyst::Controller/; |
466 | |
467 | sub view : Local { } |
468 | sub list : Local { } |
469 | |
470 | package MyApp::Controller::Cart; |
471 | |
472 | use base qw/Catalyst::Controller/; |
473 | |
474 | sub add : Local { } |
475 | sub update : Local { } |
476 | sub order : Local { } |
477 | |
478 | Note that you can also supply attributes via the Controller's config so |
479 | long as you have at least one attribute on a subref to be exported |
480 | (:Action is commonly used for this) - for example the following is |
481 | equivalent to the same controller above: |
482 | |
483 | package MyApp::Controller::Login; |
484 | |
485 | use base qw/Catalyst::Controller/; |
486 | |
487 | __PACKAGE__->config( |
488 | actions => { |
489 | 'sign_in' => { Path => 'sign-in' }, |
490 | 'new_password' => { Path => 'new-password' }, |
491 | 'sign_out' => { Path => 'sign-out' }, |
492 | }, |
493 | ); |
494 | |
495 | sub sign_in : Action { } |
496 | sub new_password : Action { } |
497 | sub sign_out : Action { } |
498 | |
499 | =head3 ACCEPT_CONTEXT |
500 | |
501 | Whenever you call $c->component("Foo") you get back an object - the |
502 | instance of the model. If the component supports the C<ACCEPT_CONTEXT> |
503 | method instead of returning the model itself, the return value of C<< |
504 | $model->ACCEPT_CONTEXT( $c ) >> will be used. |
505 | |
506 | This means that whenever your model/view/controller needs to talk to C<$c> it |
507 | gets a chance to do this when it's needed. |
508 | |
509 | A typical C<ACCEPT_CONTEXT> method will either clone the model and return one |
510 | with the context object set, or it will return a thin wrapper that contains |
511 | C<$c> and delegates to the per-application model object. |
512 | |
513 | A typical C<ACCEPT_CONTEXT> method could look like this: |
514 | |
515 | sub ACCEPT_CONTEXT { |
516 | my ( $self, $c, @extra_arguments ) = @_; |
517 | bless { %$self, c => $c }, ref($self); |
518 | } |
519 | |
520 | effectively treating $self as a B<prototype object> that gets a new parameter. |
521 | C<@extra_arguments> comes from any trailing arguments to |
522 | C<< $c->component( $bah, @extra_arguments ) >> (or C<< $c->model(...) >>, |
523 | C<< $c->view(...) >> etc). |
524 | |
525 | The life time of this value is B<per usage>, and not per request. To make this |
526 | per request you can use the following technique: |
527 | |
528 | Add a field to C<$c>, like C<my_model_instance>. Then write your |
529 | C<ACCEPT_CONTEXT> method to look like this: |
530 | |
531 | sub ACCEPT_CONTEXT { |
532 | my ( $self, $c ) = @_; |
533 | |
534 | if ( my $per_request = $c->my_model_instance ) { |
535 | return $per_request; |
536 | } else { |
537 | my $new_instance = bless { %$self, c => $c }, ref($self); |
538 | Scalar::Util::weaken($new_instance->{c}); # or we have a circular reference |
539 | $c->my_model_instance( $new_instance ); |
540 | return $new_instance; |
541 | } |
542 | } |
543 | |
544 | =head3 Application Class |
545 | |
546 | In addition to the Model, View, and Controller components, there's a |
547 | single class that represents your application itself. This is where you |
548 | configure your application, load plugins, and extend Catalyst. |
549 | |
550 | package MyApp; |
551 | |
552 | use strict; |
553 | use Catalyst qw/-Debug/; # Add other plugins here, e.g. |
554 | # for session support |
555 | |
556 | MyApp->config( |
557 | name => 'My Application', |
558 | |
559 | # You can put anything else you want in here: |
560 | my_configuration_variable => 'something', |
561 | ); |
562 | 1; |
563 | |
564 | In older versions of Catalyst, the application class was where you put |
565 | global actions. However, as of version 5.66, the recommended practice is |
566 | to place such actions in a special Root controller (see L</Actions>, |
567 | below), to avoid namespace collisions. |
568 | |
569 | =over 4 |
570 | |
571 | =item * B<name> |
572 | |
573 | The name of your application. |
574 | |
575 | =back |
576 | |
577 | Optionally, you can specify a B<root> parameter for templates and static |
578 | data. If omitted, Catalyst will try to auto-detect the directory's |
579 | location. You can define as many parameters as you want for plugins or |
580 | whatever you need. You can access them anywhere in your application via |
581 | C<$context-E<gt>config-E<gt>{$param_name}>. |
582 | |
583 | =head3 Context |
584 | |
585 | Catalyst automatically blesses a Context object into your application |
586 | class and makes it available everywhere in your application. Use the |
587 | Context to directly interact with Catalyst and glue your L</Components> |
588 | together. For example, if you need to use the Context from within a |
589 | Template Toolkit template, it's already there: |
590 | |
591 | <h1>Welcome to [% c.config.name %]!</h1> |
592 | |
593 | As illustrated in our URL-to-Action dispatching example, the Context is |
594 | always the second method parameter, behind the Component object |
595 | reference or class name itself. Previously we called it C<$context> for |
596 | clarity, but most Catalyst developers just call it C<$c>: |
597 | |
598 | sub hello : Global { |
599 | my ( $self, $c ) = @_; |
600 | $c->res->body('Hello World!'); |
601 | } |
602 | |
603 | The Context contains several important objects: |
604 | |
605 | =over 4 |
606 | |
607 | =item * L<Catalyst::Request> |
608 | |
609 | $c->request |
610 | $c->req # alias |
611 | |
612 | The request object contains all kinds of request-specific information, like |
613 | query parameters, cookies, uploads, headers, and more. |
614 | |
615 | $c->req->params->{foo}; |
616 | $c->req->cookies->{sessionid}; |
617 | $c->req->headers->content_type; |
618 | $c->req->base; |
619 | $c->req->uri_with( { page = $pager->next_page } ); |
620 | |
621 | =item * L<Catalyst::Response> |
622 | |
623 | $c->response |
624 | $c->res # alias |
625 | |
626 | The response is like the request, but contains just response-specific |
627 | information. |
628 | |
629 | $c->res->body('Hello World'); |
630 | $c->res->status(404); |
631 | $c->res->redirect('http://oook.de'); |
632 | |
633 | =item * L<Catalyst::Config> |
634 | |
635 | $c->config |
636 | $c->config->{root}; |
637 | $c->config->{name}; |
638 | |
639 | =item * L<Catalyst::Log> |
640 | |
641 | $c->log |
642 | $c->log->debug('Something happened'); |
643 | $c->log->info('Something you should know'); |
644 | |
645 | =item * B<Stash> |
646 | |
647 | $c->stash |
648 | $c->stash->{foo} = 'bar'; |
649 | $c->stash->{baz} = {baz => 'qox'}; |
650 | $c->stash->{fred} = [qw/wilma pebbles/]; |
651 | |
652 | and so on. |
653 | |
654 | =back |
655 | |
656 | The last of these, the stash, is a universal hash for sharing data among |
657 | application components. For an example, we return to our 'hello' action: |
658 | |
659 | sub hello : Global { |
660 | my ( $self, $c ) = @_; |
661 | $c->stash->{message} = 'Hello World!'; |
662 | $c->forward('show_message'); |
663 | } |
664 | |
665 | sub show_message : Private { |
666 | my ( $self, $c ) = @_; |
667 | $c->res->body( $c->stash->{message} ); |
668 | } |
669 | |
670 | Note that the stash should be used only for passing data in an |
671 | individual request cycle; it gets cleared at a new request. If you need |
672 | to maintain persistent data, use a session. See |
673 | L<Catalyst::Plugin::Session> for a comprehensive set of |
674 | Catalyst-friendly session-handling tools. |
675 | |
676 | =head3 Actions |
677 | |
678 | A Catalyst controller is defined by its actions. An action is a |
679 | subroutine with a special attribute. You've already seen some examples |
680 | of actions in this document. The URL (for example |
681 | http://localhost.3000/foo/bar) consists of two parts, the base |
682 | (http://localhost:3000/ in this example) and the path (foo/bar). Please |
683 | note that the trailing slash after the hostname[:port] always belongs to |
684 | base and not to the action. |
685 | |
686 | =over 4 |
687 | |
688 | =item * B<Application Wide Actions> |
689 | |
690 | Actions which are called at the root level of the application |
691 | (e.g. http://localhost:3000/ ) go in MyApp::Controller::Root, like |
692 | this: |
693 | |
694 | package MyApp::Controller::Root; |
695 | use base 'Catalyst::Controller'; |
696 | # Sets the actions in this controller to be registered with no prefix |
697 | # so they function identically to actions created in MyApp.pm |
698 | __PACKAGE__->config->{namespace} = ''; |
699 | sub default : Private { |
700 | my ( $self, $context ) = @_; |
701 | $context->response->body('Catalyst rocks!'); |
702 | } |
703 | 1; |
704 | |
705 | =back |
706 | |
707 | =head4 Action types |
708 | |
709 | Catalyst supports several types of actions: |
710 | |
711 | =over 4 |
712 | |
713 | =item * B<Literal> (B<Path> actions) |
714 | |
715 | package MyApp::Controller::My::Controller; |
716 | sub bar : Path('foo/bar') { } |
717 | |
718 | Literal C<Path> actions will act relative to their current |
719 | namespace. The above example matches only |
720 | http://localhost:3000/my/controller/foo/bar. If you start your path with |
721 | a forward slash, it will match from the root. Example: |
722 | |
723 | package MyApp::Controller::My::Controller; |
724 | sub bar : Path('/foo/bar') { } |
725 | |
726 | Matches only http://localhost:3000/foo/bar. |
727 | |
728 | package MyApp::Controller::My::Controller; |
729 | sub bar : Path { } |
730 | |
731 | By leaving the C<Path> definition empty, it will match on the namespace |
732 | root. The above code matches http://localhost:3000/my/controller. |
733 | |
734 | =item * B<Regex> |
735 | |
736 | sub bar : Regex('^item(\d+)/order(\d+)$') { } |
737 | |
738 | Matches any URL that matches the pattern in the action key, e.g. |
739 | http://localhost:3000/item23/order42. The '' around the regexp is |
740 | optional, but perltidy likes it. :) |
741 | |
742 | Regex matches act globally, i.e. without reference to the namespace from |
743 | which it is called, so that a C<bar> method in the |
744 | C<MyApp::Controller::Catalog::Order::Process> namespace won't match any |
745 | form of C<bar>, C<Catalog>, C<Order>, or C<Process> unless you |
746 | explicitly put this in the regex. To achieve the above, you should |
747 | consider using a C<LocalRegex> action. |
748 | |
749 | =item * B<LocalRegex> |
750 | |
751 | sub bar : LocalRegex('^widget(\d+)$') { } |
752 | |
753 | LocalRegex actions act locally. If you were to use C<bar> in |
754 | C<MyApp::Controller::Catalog>, the above example would match urls like |
755 | http://localhost:3000/catalog/widget23. |
756 | |
757 | If you omit the "C<^>" from your regex, then it will match any depth |
758 | from the controller and not immediately off of the controller name. The |
759 | following example differs from the above code in that it will match |
760 | http://localhost:3000/catalog/foo/widget23 as well. |
761 | |
762 | package MyApp::Controller::Catalog; |
763 | sub bar : LocalRegex('widget(\d+)$') { } |
764 | |
765 | For both LocalRegex and Regex actions, if you use capturing parentheses |
766 | to extract values within the matching URL, those values are available in |
767 | the C<$c-E<gt>req-E<gt>captures> array. In the above example, "widget23" |
768 | would capture "23" in the above example, and |
769 | C<$c-E<gt>req-E<gt>captures-E<gt>[0]> would be "23". If you want to pass |
770 | arguments at the end of your URL, you must use regex action keys. See |
771 | L</URL Path Handling> below. |
772 | |
773 | =item * B<Top-level> (B<Global>) |
774 | |
775 | package MyApp::Controller::Foo; |
776 | sub foo : Global { } |
777 | |
778 | Matches http://localhost:3000/foo. The function name is mapped |
779 | directly to the application base. You can provide an equivalent |
780 | function in this case by doing the following: |
781 | |
782 | package MyApp::Controller::Root |
783 | sub foo : Local { } |
784 | |
785 | =item * B<Namespace-Prefixed> (B<Local>) |
786 | |
787 | package MyApp::Controller::My::Controller; |
788 | sub foo : Local { } |
789 | |
790 | Matches http://localhost:3000/my/controller/foo. |
791 | |
792 | This action type indicates that the matching URL must be prefixed with a |
793 | modified form of the component's class (package) name. This modified |
794 | class name excludes the parts that have a pre-defined meaning in |
795 | Catalyst ("MyApp::Controller" in the above example), replaces "::" with |
796 | "/", and converts the name to lower case. See L</Components> for a full |
797 | explanation of the pre-defined meaning of Catalyst component class |
798 | names. |
799 | |
800 | =item * B<Chained> |
801 | |
802 | Catalyst also provides a method to build and dispatch chains of actions, |
803 | like |
804 | |
805 | sub catalog : Chained : CaptureArgs(1) { |
806 | my ( $self, $c, $arg ) = @_; |
807 | ... |
808 | } |
809 | |
810 | sub item : Chained('catalog') : Args(1) { |
811 | my ( $self, $c, $arg ) = @_; |
812 | ... |
813 | } |
814 | |
815 | to handle a C</catalog/*/item/*> path. For further information about this |
816 | dispatch type, please see L<Catalyst::DispatchType::Chained>. |
817 | |
818 | =item * B<Private> |
819 | |
820 | sub foo : Private { } |
821 | |
822 | Matches no URL, and cannot be executed by requesting a URL that |
09f13e1d |
823 | corresponds to the action key. Catalyst's :Private attribute is |
824 | exclusive and doesn't work with other attributes (so will not work |
825 | combined with Path or Chained attributes). With the exception of the |
826 | C< index >, C< auto > and C< default > actions, Private actions can |
827 | only be executed from inside a Catalyst application, by calling the |
828 | C<forward> or C<detach> methods: |
cb93c9d7 |
829 | |
830 | $c->forward('foo'); |
09f13e1d |
831 | # or |
832 | $c->detach('foo'); |
cb93c9d7 |
833 | |
834 | See L</Flow Control> for a full explanation of C<forward>. Note that, as |
835 | discussed there, when forwarding from another component, you must use |
836 | the absolute path to the method, so that a private C<bar> method in your |
837 | C<MyApp::Controller::Catalog::Order::Process> controller must, if called |
838 | from elsewhere, be reached with |
839 | C<$c-E<gt>forward('/catalog/order/process/bar')>. |
840 | |
841 | =item * B<Args> |
842 | |
843 | Args is not an action type per se, but an action modifier - it adds a |
844 | match restriction to any action it's provided to, requiring only as many |
845 | path parts as are specified for the action to be valid - for example in |
846 | MyApp::Controller::Foo, |
847 | |
848 | sub bar :Local |
849 | |
850 | would match any URL starting /foo/bar/. To restrict this you can do |
851 | |
852 | sub bar :Local :Args(1) |
853 | |
854 | to only match /foo/bar/*/ |
855 | |
856 | =back |
857 | |
858 | B<Note:> After seeing these examples, you probably wonder what the point |
859 | is of defining names for regex and path actions. Every public action is |
860 | also a private one, so you have one unified way of addressing components |
861 | in your C<forward>s. |
862 | |
863 | =head4 Built-in Private Actions |
864 | |
865 | In response to specific application states, Catalyst will automatically |
866 | call these built-in private actions in your application class: |
867 | |
868 | =over 4 |
869 | |
870 | =item * B<default : Private> |
871 | |
872 | Called when no other action matches. Could be used, for example, for |
873 | displaying a generic frontpage for the main app, or an error page for |
874 | individual controllers. |
875 | |
876 | If C<default> isn't acting how you would expect, look at using a |
877 | L</Literal> C<Path> action (with an empty path string). The difference |
878 | is that C<Path> takes arguments relative from the namespace and |
879 | C<default> I<always> takes arguments relative from the root, regardless |
880 | of what controller it's in. Indeed, this is now the recommended way of |
881 | handling default situations; the C<default> private controller should |
882 | be considered deprecated. |
883 | |
884 | =item * B<index : Private> |
885 | |
886 | C<index> is much like C<default> except that it takes no arguments |
887 | and it is weighted slightly higher in the matching process. It is |
888 | useful as a static entry point to a controller, e.g. to have a static |
889 | welcome page. Note that it's also weighted higher than Path. |
890 | |
891 | =item * B<begin : Private> |
892 | |
893 | Called at the beginning of a request, before any matching actions are |
894 | called. |
895 | |
896 | =item * B<end : Private> |
897 | |
898 | Called at the end of a request, after all matching actions are called. |
899 | |
900 | =back |
901 | |
902 | =head4 Built-in actions in controllers/autochaining |
903 | |
904 | Package MyApp::Controller::Foo; |
905 | sub begin : Private { } |
906 | sub default : Private { } |
907 | sub auto : Private { } |
908 | |
909 | You can define built-in private actions within your controllers as |
910 | well. The actions will override the ones in less-specific controllers, |
911 | or your application class. In other words, for each of the three |
912 | built-in private actions, only one will be run in any request |
913 | cycle. Thus, if C<MyApp::Controller::Catalog::begin> exists, it will be |
914 | run in place of C<MyApp::begin> if you're in the C<catalog> namespace, |
915 | and C<MyApp::Controller::Catalog::Order::begin> would override this in |
916 | turn. |
917 | |
918 | =over 4 |
919 | |
920 | =item * B<auto : Private> |
921 | |
922 | In addition to the normal built-in actions, you have a special action |
923 | for making chains, C<auto>. Such C<auto> actions will be run after any |
924 | C<begin>, but before your action is processed. Unlike the other |
925 | built-ins, C<auto> actions I<do not> override each other; they will be |
926 | called in turn, starting with the application class and going through to |
927 | the I<most> specific class. I<This is the reverse of the order in which |
928 | the normal built-ins override each other>. |
929 | |
930 | =back |
931 | |
932 | Here are some examples of the order in which the various built-ins |
933 | would be called: |
934 | |
935 | =over 4 |
936 | |
937 | =item for a request for C</foo/foo> |
938 | |
939 | MyApp::begin |
940 | MyApp::auto |
941 | MyApp::Controller::Foo::default # in the absence of MyApp::Controller::Foo::Foo |
942 | MyApp::end |
943 | |
944 | =item for a request for C</foo/bar/foo> |
945 | |
946 | MyApp::Controller::Foo::Bar::begin |
947 | MyApp::auto |
948 | MyApp::Controller::Foo::auto |
949 | MyApp::Controller::Foo::Bar::auto |
950 | MyApp::Controller::Foo::Bar::default # for MyApp::Controller::Foo::Bar::foo |
951 | MyApp::Controller::Foo::Bar::end |
952 | |
953 | =back |
954 | |
955 | The C<auto> action is also distinguished by the fact that you can break |
956 | out of the processing chain by returning 0. If an C<auto> action returns |
957 | 0, any remaining actions will be skipped, except for C<end>. So, for the |
958 | request above, if the first auto returns false, the chain would look |
959 | like this: |
960 | |
961 | =over 4 |
962 | |
963 | =item for a request for C</foo/bar/foo> where first C<auto> returns |
964 | false |
965 | |
966 | MyApp::Controller::Foo::Bar::begin |
967 | MyApp::auto |
968 | MyApp::Controller::Foo::Bar::end |
969 | |
970 | =back |
971 | |
972 | An example of why one might use this is an authentication action: you |
973 | could set up a C<auto> action to handle authentication in your |
974 | application class (which will always be called first), and if |
975 | authentication fails, returning 0 would skip any remaining methods |
976 | for that URL. |
977 | |
978 | B<Note:> Looking at it another way, C<auto> actions have to return a |
979 | true value to continue processing! You can also C<die> in the auto |
980 | action; in that case, the request will go straight to the finalize |
981 | stage, without processing further actions. |
982 | |
983 | =head4 URL Path Handling |
984 | |
985 | You can pass variable arguments as part of the URL path, separated with |
986 | forward slashes (/). If the action is a Regex or LocalRegex, the '$' anchor |
987 | must be used. For example, suppose you want to handle C</foo/$bar/$baz>, |
988 | where C<$bar> and C<$baz> may vary: |
989 | |
990 | sub foo : Regex('^foo$') { my ($self, $context, $bar, $baz) = @_; } |
991 | |
992 | But what if you also defined actions for C</foo/boo> and C</foo/boo/hoo>? |
993 | |
994 | sub boo : Path('foo/boo') { .. } |
995 | sub hoo : Path('foo/boo/hoo') { .. } |
996 | |
997 | Catalyst matches actions in most specific to least specific order: |
998 | |
999 | /foo/boo/hoo |
1000 | /foo/boo |
1001 | /foo # might be /foo/bar/baz but won't be /foo/boo/hoo |
1002 | |
1003 | So Catalyst would never mistakenly dispatch the first two URLs to the |
1004 | '^foo$' action. |
1005 | |
1006 | If a Regex or LocalRegex action doesn't use the '$' anchor, the action will |
1007 | still match a URL containing arguments, however the arguments won't be |
1008 | available via C<@_>. |
1009 | |
1010 | =head4 Parameter Processing |
1011 | |
1012 | Parameters passed in the URL query string are handled with methods in |
1013 | the L<Catalyst::Request> class. The C<param> method is functionally |
1014 | equivalent to the C<param> method of C<CGI.pm> and can be used in |
1015 | modules that require this. |
1016 | |
1017 | # http://localhost:3000/catalog/view/?category=hardware&page=3 |
1018 | my $category = $c->req->param('category'); |
1019 | my $current_page = $c->req->param('page') || 1; |
1020 | |
1021 | # multiple values for single parameter name |
1022 | my @values = $c->req->param('scrolling_list'); |
1023 | |
1024 | # DFV requires a CGI.pm-like input hash |
1025 | my $results = Data::FormValidator->check($c->req->params, \%dfv_profile); |
1026 | |
1027 | =head3 Flow Control |
1028 | |
1029 | You control the application flow with the C<forward> method, which |
1030 | accepts the key of an action to execute. This can be an action in the |
1031 | same or another Catalyst controller, or a Class name, optionally |
1032 | followed by a method name. After a C<forward>, the control flow will |
1033 | return to the method from which the C<forward> was issued. |
1034 | |
1035 | A C<forward> is similar to a method call. The main differences are that |
1036 | it wraps the call in an C<eval> to allow exception handling; it |
1037 | automatically passes along the context object (C<$c> or C<$context>); |
1038 | and it allows profiling of each call (displayed in the log with |
1039 | debugging enabled). |
1040 | |
1041 | sub hello : Global { |
1042 | my ( $self, $c ) = @_; |
1043 | $c->stash->{message} = 'Hello World!'; |
1044 | $c->forward('check_message'); # $c is automatically included |
1045 | } |
1046 | |
1047 | sub check_message : Private { |
1048 | my ( $self, $c ) = @_; |
1049 | return unless $c->stash->{message}; |
1050 | $c->forward('show_message'); |
1051 | } |
1052 | |
1053 | sub show_message : Private { |
1054 | my ( $self, $c ) = @_; |
1055 | $c->res->body( $c->stash->{message} ); |
1056 | } |
1057 | |
1058 | A C<forward> does not create a new request, so your request object |
1059 | (C<$c-E<gt>req>) will remain unchanged. This is a key difference between |
1060 | using C<forward> and issuing a redirect. |
1061 | |
1062 | You can pass new arguments to a C<forward> by adding them |
1063 | in an anonymous array. In this case C<$c-E<gt>req-E<gt>args> |
1064 | will be changed for the duration of the C<forward> only; upon |
1065 | return, the original value of C<$c-E<gt>req-E<gt>args> will |
1066 | be reset. |
1067 | |
1068 | sub hello : Global { |
1069 | my ( $self, $c ) = @_; |
1070 | $c->stash->{message} = 'Hello World!'; |
1071 | $c->forward('check_message',[qw/test1/]); |
1072 | # now $c->req->args is back to what it was before |
1073 | } |
1074 | |
1075 | sub check_message : Private { |
1076 | my ( $self, $c ) = @_; |
1077 | my $first_argument = $c->req->args->[0]; # now = 'test1' |
1078 | # do something... |
1079 | } |
1080 | |
1081 | As you can see from these examples, you can just use the method name as |
1082 | long as you are referring to methods in the same controller. If you want |
1083 | to forward to a method in another controller, or the main application, |
1084 | you will have to refer to the method by absolute path. |
1085 | |
1086 | $c->forward('/my/controller/action'); |
1087 | $c->forward('/default'); # calls default in main application |
1088 | |
1089 | Here are some examples of how to forward to classes and methods. |
1090 | |
1091 | sub hello : Global { |
1092 | my ( $self, $c ) = @_; |
1093 | $c->forward(qw/MyApp::Model::Hello say_hello/); |
1094 | } |
1095 | |
1096 | sub bye : Global { |
1097 | my ( $self, $c ) = @_; |
1098 | $c->forward('MyApp::Model::Hello'); # no method: will try 'process' |
1099 | } |
1100 | |
1101 | package MyApp::Model::Hello; |
1102 | |
1103 | sub say_hello { |
1104 | my ( $self, $c ) = @_; |
1105 | $c->res->body('Hello World!'); |
1106 | } |
1107 | |
1108 | sub process { |
1109 | my ( $self, $c ) = @_; |
1110 | $c->res->body('Goodbye World!'); |
1111 | } |
1112 | |
1113 | Note that C<forward> returns to the calling action and continues |
1114 | processing after the action finishes. If you want all further processing |
1115 | in the calling action to stop, use C<detach> instead, which will execute |
1116 | the C<detach>ed action and not return to the calling sub. In both cases, |
1117 | Catalyst will automatically try to call process() if you omit the |
1118 | method. |
1119 | |
1120 | |
1121 | =head3 Testing |
1122 | |
1123 | Catalyst has a built-in http server for testing or local |
1124 | deployment. (Later, you can easily use a more powerful server, for |
1125 | example Apache/mod_perl or FastCGI, in a production environment.) |
1126 | |
1127 | Start your application on the command line... |
1128 | |
1129 | script/myapp_server.pl |
1130 | |
1131 | ...then visit http://localhost:3000/ in a browser to view the output. |
1132 | |
1133 | You can also do it all from the command line: |
1134 | |
1135 | script/myapp_test.pl http://localhost/ |
1136 | |
1137 | Catalyst has a number of tools for actual regression testing of |
1138 | applications. The helper scripts will automatically generate basic tests |
1139 | that can be extended as you develop your project. To write your own |
1140 | comprehensive test scripts, L<Test::WWW::Mechanize::Catalyst> is an |
1141 | invaluable tool. |
1142 | |
1143 | For more testing ideas, see L<Catalyst::Manual::Tutorial::Testing>. |
1144 | |
1145 | Have fun! |
1146 | |
1147 | =head1 SEE ALSO |
1148 | |
1149 | =over 4 |
1150 | |
1151 | =item * L<Catalyst::Manual::About> |
1152 | |
1153 | =item * L<Catalyst::Manual::Tutorial> |
1154 | |
1155 | =item * L<Catalyst> |
1156 | |
1157 | =back |
1158 | |
1159 | =head1 SUPPORT |
1160 | |
1161 | IRC: |
1162 | |
1163 | Join #catalyst on irc.perl.org. |
1164 | Join #catalyst-dev on irc.perl.org to help with development. |
1165 | |
1166 | Mailing lists: |
1167 | |
392906f2 |
1168 | http://lists.scsys.co.uk/mailman/listinfo/catalyst |
1169 | http://lists.scsys.co.uk/mailman/listinfo/catalyst-dev |
cb93c9d7 |
1170 | |
1171 | =head1 AUTHOR |
1172 | |
1173 | Sebastian Riedel, C<sri@oook.de> |
1174 | David Naughton, C<naughton@umn.edu> |
1175 | Marcus Ramberg, C<mramberg@cpan.org> |
1176 | Jesse Sheidlower, C<jester@panix.com> |
1177 | Danijel Milicevic, C<me@danijel.de> |
1178 | Kieren Diment, C<kd@totaldatasolution.com> |
1179 | Yuval Kogman, C<nothingmuch@woobling.org> |
1180 | |
1181 | =head1 COPYRIGHT |
1182 | |
1183 | This program is free software. You can redistribute it and/or modify it |
1184 | under the same terms as Perl itself. |