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1 | =head1 NAME |
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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 | |
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119 | Use L<Catalyst::Engine::Apache> or L<Catalyst::Engine::CGI>. Another |
120 | interesting engine is L<Catalyst::Engine::HTTP::Prefork> - available from CPAN |
121 | separately - which will turn the built server into a fully fledged production |
122 | ready server (although you'll probably want to run it behind a front end proxy |
123 | if you end up using it). |
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124 | |
125 | =back |
126 | |
127 | =head3 Simplicity |
128 | |
129 | The best part is that Catalyst implements all this flexibility in a very |
130 | simple way. |
131 | |
132 | =over 4 |
133 | |
134 | =item * B<Building Block Interface> |
135 | |
136 | Components interoperate very smoothly. For example, Catalyst |
137 | automatically makes a L</Context> object available to every |
138 | component. Via the context, you can access the request object, share |
139 | data between components, and control the flow of your |
140 | application. Building a Catalyst application feels a lot like snapping |
141 | together toy building blocks, and everything just works. |
142 | |
143 | =item * B<Component Auto-Discovery> |
144 | |
145 | No need to C<use> all of your components. Catalyst automatically finds |
146 | and loads them. |
147 | |
148 | =item * B<Pre-Built Components for Popular Modules> |
149 | |
150 | See L<Catalyst::Model::DBIC::Schema> for L<DBIx::Class>, or |
151 | L<Catalyst::View::TT> for L<Template Toolkit|Template>. |
152 | |
153 | =item * B<Built-in Test Framework> |
154 | |
155 | Catalyst comes with a built-in, lightweight http server and test |
156 | framework, making it easy to test applications from the web browser, |
157 | and the command line. |
158 | |
159 | =item * B<Helper Scripts> |
160 | |
161 | Catalyst provides helper scripts to quickly generate running starter |
162 | code for components and unit tests. Install L<Catalyst::Devel> and see |
163 | L<Catalyst::Helper>. |
164 | |
165 | =back |
166 | |
167 | =head2 Quickstart |
168 | |
169 | Here's how to install Catalyst and get a simple application up and |
170 | running, using the helper scripts described above. |
171 | |
172 | =head3 Install |
173 | |
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174 | Installation of Catalyst should be straightforward: |
175 | |
176 | # perl -MCPAN -e 'install Catalyst::Runtime' |
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177 | # perl -MCPAN -e 'install Catalyst::Devel' |
178 | |
179 | =head3 Setup |
180 | |
181 | $ catalyst.pl MyApp |
182 | # output omitted |
183 | $ cd MyApp |
184 | $ script/myapp_create.pl controller Library::Login |
185 | |
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186 | =head4 Frank Speiser's Amazon EC2 Catalyst SDK |
187 | |
188 | There are currently two flavors of publicly available Amazon Machine |
189 | Images (AMI) that include all the elements you'd need to begin |
190 | developing in a fully functional Catalyst environment within |
191 | minutes. See |
192 | L<Catalyst::Manual::Installation|Catalyst::Manual::Installation> for |
193 | more details. |
194 | |
195 | |
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196 | =head3 Run |
197 | |
198 | $ script/myapp_server.pl |
199 | |
200 | Now visit these locations with your favorite browser or user agent to see |
201 | Catalyst in action: |
202 | |
203 | (NOTE: Although we create a controller here, we don't actually use it. |
204 | Both of these URLs should take you to the welcome page.) |
205 | |
206 | |
207 | =over 4 |
208 | |
209 | =item http://localhost:3000/ |
210 | |
211 | =item http://localhost:3000/library/login/ |
212 | |
213 | =back |
214 | |
215 | =head2 How It Works |
216 | |
217 | Let's see how Catalyst works, by taking a closer look at the components |
218 | and other parts of a Catalyst application. |
219 | |
220 | =head3 Components |
221 | |
222 | Catalyst has an uncommonly flexible component system. You can define as |
223 | many L</Models>, L</Views>, and L</Controllers> as you like. As discussed |
224 | previously, the general idea is that the View is responsible for the |
225 | output of data to the user (typically via a web browser, but a View can |
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226 | also generate PDFs or e-mails, for example); the Model is responsible |
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227 | for providing data (typically from a relational database); and the |
228 | Controller is responsible for interacting with the user and deciding |
229 | how user input determines what actions the application takes. |
230 | |
231 | In the world of MVC, there are frequent discussions and disagreements |
232 | about the nature of each element - whether certain types of logic |
233 | belong in the Model or the Controller, etc. Catalyst's flexibility |
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234 | means that this decision is entirely up to you, the programmer; |
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235 | Catalyst doesn't enforce anything. See L<Catalyst::Manual::About> for |
236 | a general discussion of these issues. |
237 | |
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238 | Model, View and Controller components must inherit from L<Catalyst::Model>, |
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239 | L<Catalyst::View> and L<Catalyst::Controller>, respectively. These, in turn, inherit |
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240 | from L<Catalyst::Component> which provides a simple class structure and some |
241 | common class methods like C<config> and C<new> (constructor). |
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242 | |
243 | package MyApp::Controller::Catalog; |
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244 | use Moose; |
245 | use namespace::autoclean; |
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246 | |
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247 | BEGIN { extends 'Catalyst::Controller' } |
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248 | |
249 | __PACKAGE__->config( foo => 'bar' ); |
250 | |
251 | 1; |
252 | |
253 | You don't have to C<use> or otherwise register Models, Views, and |
254 | Controllers. Catalyst automatically discovers and instantiates them |
255 | when you call C<setup> in the main application. All you need to do is |
256 | put them in directories named for each Component type. You can use a |
257 | short alias for each one. |
258 | |
259 | =over 4 |
260 | |
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261 | =item * B<MyApp/Model/> |
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262 | |
263 | =item * B<MyApp/M/> |
264 | |
265 | =item * B<MyApp/View/> |
266 | |
267 | =item * B<MyApp/V/> |
268 | |
269 | =item * B<MyApp/Controller/> |
270 | |
271 | =item * B<MyApp/C/> |
272 | |
273 | =back |
274 | |
275 | In older versions of Catalyst, the recommended practice (and the one |
276 | automatically created by helper scripts) was to name the directories |
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277 | C<M/>, C<V/>, and C<C/>. Though these still work, they are deprecated |
278 | and we now recommend the use of the full names. |
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279 | |
280 | =head4 Views |
281 | |
282 | To show how to define views, we'll use an already-existing base class for the |
283 | L<Template Toolkit|Template>, L<Catalyst::View::TT>. All we need to do is |
284 | inherit from this class: |
285 | |
286 | package MyApp::View::TT; |
287 | |
288 | use strict; |
289 | use base 'Catalyst::View::TT'; |
290 | |
291 | 1; |
292 | |
293 | (You can also generate this automatically by using the helper script: |
294 | |
295 | script/myapp_create.pl view TT TT |
296 | |
297 | where the first C<TT> tells the script that the name of the view should |
298 | be C<TT>, and the second that it should be a Template Toolkit view.) |
299 | |
300 | This gives us a process() method and we can now just do |
301 | $c->forward('MyApp::View::TT') to render our templates. The base class |
302 | makes process() implicit, so we don't have to say |
303 | C<$c-E<gt>forward(qw/MyApp::View::TT process/)>. |
304 | |
305 | sub hello : Global { |
306 | my ( $self, $c ) = @_; |
307 | $c->stash->{template} = 'hello.tt'; |
308 | } |
309 | |
310 | sub end : Private { |
311 | my ( $self, $c ) = @_; |
312 | $c->forward( $c->view('TT') ); |
313 | } |
314 | |
315 | You normally render templates at the end of a request, so it's a perfect |
316 | use for the global C<end> action. |
317 | |
318 | In practice, however, you would use a default C<end> action as supplied |
319 | by L<Catalyst::Action::RenderView>. |
320 | |
321 | Also, be sure to put the template under the directory specified in |
322 | C<$c-E<gt>config-E<gt>{root}>, or you'll end up looking at the debug |
323 | screen. |
324 | |
325 | =head4 Models |
326 | |
327 | Models are providers of data. This data could come from anywhere - a |
328 | search engine index, a spreadsheet, the file system - but typically a |
329 | Model represents a database table. The data source does not |
330 | intrinsically have much to do with web applications or Catalyst - it |
331 | could just as easily be used to write an offline report generator or a |
332 | command-line tool. |
333 | |
334 | To show how to define models, again we'll use an already-existing base |
335 | class, this time for L<DBIx::Class>: L<Catalyst::Model::DBIC::Schema>. |
336 | We'll also need L<DBIx::Class::Schema::Loader>. |
337 | |
338 | But first, we need a database. |
339 | |
340 | -- myapp.sql |
341 | CREATE TABLE foo ( |
342 | id INTEGER PRIMARY KEY, |
343 | data TEXT |
344 | ); |
345 | |
346 | CREATE TABLE bar ( |
347 | id INTEGER PRIMARY KEY, |
348 | foo INTEGER REFERENCES foo, |
349 | data TEXT |
350 | ); |
351 | |
352 | INSERT INTO foo (data) VALUES ('TEST!'); |
353 | |
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354 | % sqlite3 /tmp/myapp.db < myapp.sql |
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355 | |
356 | Now we can create a DBIC::Schema model for this database. |
357 | |
358 | script/myapp_create.pl model MyModel DBIC::Schema MySchema create=static 'dbi:SQLite:/tmp/myapp.db' |
359 | |
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360 | L<DBIx::Class::Schema::Loader> can automatically load table layouts and |
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361 | relationships, and convert them into a static schema definition |
362 | C<MySchema>, which you can edit later. |
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363 | |
364 | Use the stash to pass data to your templates. |
365 | |
366 | We add the following to MyApp/Controller/Root.pm |
367 | |
368 | sub view : Global { |
369 | my ( $self, $c, $id ) = @_; |
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370 | |
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371 | $c->stash->{item} = $c->model('MyModel::Foo')->find($id); |
372 | } |
373 | |
374 | 1; |
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375 | |
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376 | sub end : Private { |
377 | my ( $self, $c ) = @_; |
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378 | |
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379 | $c->stash->{template} ||= 'index.tt'; |
380 | $c->forward( $c->view('TT') ); |
381 | } |
382 | |
383 | We then create a new template file "root/index.tt" containing: |
384 | |
385 | The Id's data is [% item.data %] |
386 | |
387 | Models do not have to be part of your Catalyst application; you |
388 | can always call an outside module that serves as your Model: |
389 | |
390 | # in a Controller |
391 | sub list : Local { |
392 | my ( $self, $c ) = @_; |
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393 | |
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394 | $c->stash->{template} = 'list.tt'; |
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395 | |
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396 | use Some::Outside::Database::Module; |
397 | my @records = Some::Outside::Database::Module->search({ |
398 | artist => 'Led Zeppelin', |
399 | }); |
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400 | |
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401 | $c->stash->{records} = \@records; |
402 | } |
403 | |
404 | But by using a Model that is part of your Catalyst application, you |
405 | gain several things: you don't have to C<use> each component, Catalyst |
406 | will find and load it automatically at compile-time; you can |
407 | C<forward> to the module, which can only be done to Catalyst |
408 | components. Only Catalyst components can be fetched with |
409 | C<$c-E<gt>model('SomeModel')>. |
410 | |
411 | Happily, since many people have existing Model classes that they |
412 | would like to use with Catalyst (or, conversely, they want to |
413 | write Catalyst models that can be used outside of Catalyst, e.g. |
414 | in a cron job), it's trivial to write a simple component in |
415 | Catalyst that slurps in an outside Model: |
416 | |
417 | package MyApp::Model::DB; |
418 | use base qw/Catalyst::Model::DBIC::Schema/; |
419 | __PACKAGE__->config( |
420 | schema_class => 'Some::DBIC::Schema', |
421 | connect_info => ['dbi:SQLite:foo.db', '', '', {AutoCommit=>1}] |
422 | ); |
423 | 1; |
424 | |
425 | and that's it! Now C<Some::DBIC::Schema> is part of your |
426 | Cat app as C<MyApp::Model::DB>. |
427 | |
428 | Within Catalyst, the common approach to writing a model for your |
429 | application is wrapping a generic model (e.g. L<DBIx::Class::Schema>, a |
430 | bunch of XMLs, or anything really) with an object that contains |
431 | configuration data, convenience methods, and so forth. Thus you |
432 | will in effect have two models - a wrapper model that knows something |
433 | about Catalyst and your web application, and a generic model that is |
434 | totally independent of these needs. |
435 | |
436 | Technically, within Catalyst a model is a B<component> - an instance of |
437 | the model's class belonging to the application. It is important to |
438 | stress that the lifetime of these objects is per application, not per |
439 | request. |
440 | |
441 | While the model base class (L<Catalyst::Model>) provides things like |
442 | C<config> to better integrate the model into the application, sometimes |
443 | this is not enough, and the model requires access to C<$c> itself. |
444 | |
445 | Situations where this need might arise include: |
446 | |
447 | =over 4 |
448 | |
449 | =item * |
450 | |
451 | Interacting with another model |
452 | |
453 | =item * |
454 | |
455 | Using per-request data to control behavior |
456 | |
457 | =item * |
458 | |
459 | Using plugins from a Model (for example L<Catalyst::Plugin::Cache>). |
460 | |
461 | =back |
462 | |
463 | From a style perspective it's usually considered bad form to make your |
464 | model "too smart" about things - it should worry about business logic |
465 | and leave the integration details to the controllers. If, however, you |
466 | find that it does not make sense at all to use an auxillary controller |
467 | around the model, and the model's need to access C<$c> cannot be |
468 | sidestepped, there exists a power tool called L</ACCEPT_CONTEXT>. |
469 | |
470 | =head4 Controllers |
471 | |
472 | Multiple controllers are a good way to separate logical domains of your |
473 | application. |
474 | |
475 | package MyApp::Controller::Login; |
476 | |
477 | use base qw/Catalyst::Controller/; |
478 | |
479 | sub login : Path("login") { } |
480 | sub new_password : Path("new-password") { } |
481 | sub logout : Path("logout") { } |
482 | |
483 | package MyApp::Controller::Catalog; |
484 | |
485 | use base qw/Catalyst::Controller/; |
486 | |
487 | sub view : Local { } |
488 | sub list : Local { } |
489 | |
490 | package MyApp::Controller::Cart; |
491 | |
492 | use base qw/Catalyst::Controller/; |
493 | |
494 | sub add : Local { } |
495 | sub update : Local { } |
496 | sub order : Local { } |
497 | |
498 | Note that you can also supply attributes via the Controller's config so |
499 | long as you have at least one attribute on a subref to be exported |
500 | (:Action is commonly used for this) - for example the following is |
501 | equivalent to the same controller above: |
502 | |
503 | package MyApp::Controller::Login; |
504 | |
505 | use base qw/Catalyst::Controller/; |
506 | |
507 | __PACKAGE__->config( |
508 | actions => { |
509 | 'sign_in' => { Path => 'sign-in' }, |
510 | 'new_password' => { Path => 'new-password' }, |
511 | 'sign_out' => { Path => 'sign-out' }, |
512 | }, |
513 | ); |
514 | |
515 | sub sign_in : Action { } |
516 | sub new_password : Action { } |
517 | sub sign_out : Action { } |
518 | |
519 | =head3 ACCEPT_CONTEXT |
520 | |
521 | Whenever you call $c->component("Foo") you get back an object - the |
522 | instance of the model. If the component supports the C<ACCEPT_CONTEXT> |
523 | method instead of returning the model itself, the return value of C<< |
524 | $model->ACCEPT_CONTEXT( $c ) >> will be used. |
525 | |
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526 | This means that whenever your model/view/controller needs to talk to |
527 | C<$c> it gets a chance to do this when it's needed. |
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528 | |
529 | A typical C<ACCEPT_CONTEXT> method will either clone the model and return one |
530 | with the context object set, or it will return a thin wrapper that contains |
531 | C<$c> and delegates to the per-application model object. |
532 | |
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533 | Generally it's a bad idea to expose the context object (C<$c>) in your |
534 | model or view code. Instead you use the C<ACCEPT_CONTEXT> subroutine |
535 | to grab the bits of the context object that you need, and provide |
536 | accessors to them in the model. This ensures that C<$c> is only in |
537 | scope where it is neaded which reduces maintenance and debugging |
538 | headaches. So, if for example you needed two |
539 | L<Catalyst::Model::DBIC::Schema> models in the same Catalyst model |
540 | code, you might do something like this: |
541 | |
542 | __PACKAGE__->mk_accessors(qw(model1_schema model2_schema)); |
543 | sub ACCEPT_CONTEXT { |
544 | my ( $self, $c, @extra_arguments ) = @_; |
545 | $self = bless({ %$self, |
546 | model1_schema => $c->model('Model1')->schema, |
547 | model2_schema => $c->model('Model2')->schema |
548 | }, ref($self)); |
549 | return $self; |
550 | } |
551 | |
552 | This effectively treats $self as a B<prototype object> that gets a new |
553 | parameter. C<@extra_arguments> comes from any trailing arguments to |
554 | C<< $c->component( $bah, @extra_arguments ) >> (or C<< $c->model(...) |
555 | >>, C<< $c->view(...) >> etc). |
556 | |
557 | In a subroutine in the model code, we can then do this: |
558 | |
559 | sub whatever { |
560 | my ($self) = @_; |
561 | my $schema1 = $self->model1_schema; |
562 | my $schema2 = $self->model2_schema; |
563 | ... |
564 | } |
565 | |
566 | Note that we still want the Catalyst models to be a thin wrapper |
567 | around classes that will work independently of the Catalyst |
568 | application to promote reusability of code. Here we might just want |
569 | to grab the $c->model('DB')->schema so as to get the connection |
570 | information from the Catalyst application's configuration for example. |
571 | |
572 | The life time of this value is B<per usage>, and not per request. To |
573 | make this per request you can use the following technique: |
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574 | |
575 | Add a field to C<$c>, like C<my_model_instance>. Then write your |
576 | C<ACCEPT_CONTEXT> method to look like this: |
577 | |
578 | sub ACCEPT_CONTEXT { |
579 | my ( $self, $c ) = @_; |
580 | |
581 | if ( my $per_request = $c->my_model_instance ) { |
582 | return $per_request; |
583 | } else { |
584 | my $new_instance = bless { %$self, c => $c }, ref($self); |
585 | Scalar::Util::weaken($new_instance->{c}); # or we have a circular reference |
586 | $c->my_model_instance( $new_instance ); |
587 | return $new_instance; |
588 | } |
589 | } |
590 | |
0cc6ab50 |
591 | For a similar technique to grab a new component instance on each |
592 | request, see L<Catalyst::Component::InstancePerContext>. |
593 | |
cb93c9d7 |
594 | =head3 Application Class |
595 | |
596 | In addition to the Model, View, and Controller components, there's a |
597 | single class that represents your application itself. This is where you |
598 | configure your application, load plugins, and extend Catalyst. |
599 | |
600 | package MyApp; |
601 | |
602 | use strict; |
ca7528df |
603 | use parent qw/Catalyst/; |
b411df01 |
604 | use Catalyst qw/-Debug ConfigLoader Static::Simple/; |
cb93c9d7 |
605 | MyApp->config( |
606 | name => 'My Application', |
607 | |
608 | # You can put anything else you want in here: |
609 | my_configuration_variable => 'something', |
610 | ); |
611 | 1; |
612 | |
613 | In older versions of Catalyst, the application class was where you put |
614 | global actions. However, as of version 5.66, the recommended practice is |
615 | to place such actions in a special Root controller (see L</Actions>, |
616 | below), to avoid namespace collisions. |
617 | |
618 | =over 4 |
619 | |
620 | =item * B<name> |
621 | |
622 | The name of your application. |
623 | |
624 | =back |
625 | |
626 | Optionally, you can specify a B<root> parameter for templates and static |
627 | data. If omitted, Catalyst will try to auto-detect the directory's |
628 | location. You can define as many parameters as you want for plugins or |
629 | whatever you need. You can access them anywhere in your application via |
630 | C<$context-E<gt>config-E<gt>{$param_name}>. |
631 | |
632 | =head3 Context |
633 | |
634 | Catalyst automatically blesses a Context object into your application |
635 | class and makes it available everywhere in your application. Use the |
636 | Context to directly interact with Catalyst and glue your L</Components> |
637 | together. For example, if you need to use the Context from within a |
638 | Template Toolkit template, it's already there: |
639 | |
640 | <h1>Welcome to [% c.config.name %]!</h1> |
641 | |
642 | As illustrated in our URL-to-Action dispatching example, the Context is |
643 | always the second method parameter, behind the Component object |
644 | reference or class name itself. Previously we called it C<$context> for |
645 | clarity, but most Catalyst developers just call it C<$c>: |
646 | |
647 | sub hello : Global { |
648 | my ( $self, $c ) = @_; |
649 | $c->res->body('Hello World!'); |
650 | } |
651 | |
652 | The Context contains several important objects: |
653 | |
654 | =over 4 |
655 | |
656 | =item * L<Catalyst::Request> |
657 | |
658 | $c->request |
659 | $c->req # alias |
660 | |
661 | The request object contains all kinds of request-specific information, like |
662 | query parameters, cookies, uploads, headers, and more. |
663 | |
664 | $c->req->params->{foo}; |
665 | $c->req->cookies->{sessionid}; |
666 | $c->req->headers->content_type; |
667 | $c->req->base; |
668 | $c->req->uri_with( { page = $pager->next_page } ); |
669 | |
670 | =item * L<Catalyst::Response> |
671 | |
672 | $c->response |
673 | $c->res # alias |
674 | |
675 | The response is like the request, but contains just response-specific |
676 | information. |
677 | |
678 | $c->res->body('Hello World'); |
679 | $c->res->status(404); |
680 | $c->res->redirect('http://oook.de'); |
681 | |
709ea2fc |
682 | =item * config |
cb93c9d7 |
683 | |
684 | $c->config |
685 | $c->config->{root}; |
686 | $c->config->{name}; |
687 | |
688 | =item * L<Catalyst::Log> |
689 | |
690 | $c->log |
691 | $c->log->debug('Something happened'); |
692 | $c->log->info('Something you should know'); |
693 | |
694 | =item * B<Stash> |
695 | |
696 | $c->stash |
697 | $c->stash->{foo} = 'bar'; |
698 | $c->stash->{baz} = {baz => 'qox'}; |
699 | $c->stash->{fred} = [qw/wilma pebbles/]; |
700 | |
701 | and so on. |
702 | |
703 | =back |
704 | |
705 | The last of these, the stash, is a universal hash for sharing data among |
706 | application components. For an example, we return to our 'hello' action: |
707 | |
708 | sub hello : Global { |
709 | my ( $self, $c ) = @_; |
710 | $c->stash->{message} = 'Hello World!'; |
711 | $c->forward('show_message'); |
712 | } |
713 | |
714 | sub show_message : Private { |
715 | my ( $self, $c ) = @_; |
716 | $c->res->body( $c->stash->{message} ); |
717 | } |
718 | |
719 | Note that the stash should be used only for passing data in an |
720 | individual request cycle; it gets cleared at a new request. If you need |
721 | to maintain persistent data, use a session. See |
722 | L<Catalyst::Plugin::Session> for a comprehensive set of |
723 | Catalyst-friendly session-handling tools. |
724 | |
725 | =head3 Actions |
726 | |
d6ea2bcb |
727 | You've already seen some examples of actions in this document: |
728 | subroutines with C<:Path> and C<:Local> attributes attached. |
729 | Here, we explain what actions are and how these attributes affect |
730 | what's happening. |
731 | |
732 | When Catalyst processes a webpage request, it looks for actions to |
733 | take that will deal with the incoming request and produce a response |
734 | such as a webpage. You create these actions for your application by |
735 | writing subroutines within your controller and marking them with |
736 | special attributes. The attributes, the namespace, and the function |
737 | name determine when Catalyst will call the subroutine. |
738 | |
739 | These action subroutines call certain functions to say what response |
740 | the webserver will give to the web request. They can also tell |
741 | Catalyst to run other actions on the request (one example of this is |
742 | called forwarding the request; this is discussed later). |
743 | |
744 | Action subroutines must have a special attribute on to show that they |
745 | are actions - as well as marking when to call them, this shows that |
746 | they take a specific set of arguments and behave in a specific way. |
747 | At startup, Catalyst looks for all the actions in controllers, |
748 | registers them and creates L<Catalyst::Action> objects describing |
749 | them. When requests come in, Catalyst chooses which actions should be |
750 | called to handle the request. |
751 | |
752 | (Occasionally, you might use the action objects directly, but in |
753 | general, when we talk about actions, we're talking about the |
754 | subroutines in your application that do things to process a request.) |
755 | |
756 | You can choose one of several attributes for action subroutines; these |
757 | specify which requests are processed by that subroutine. Catalyst |
758 | will look at the URL it is processing, and the actions that it has |
759 | found, and automatically call the actions it finds that match the |
760 | circumstances of the request. |
761 | |
caf6e9ce |
762 | The URL (for example http://localhost:3000/foo/bar) consists of two |
d6ea2bcb |
763 | parts, the base, describing how to connect to the server |
764 | (http://localhost:3000/ in this example) and the path, which the |
765 | server uses to decide what to return (foo/bar). Please note that the |
766 | trailing slash after the hostname[:port] always belongs to base and |
767 | not to the path. Catalyst uses only the path part when trying to find |
768 | actions to process. |
769 | |
770 | Depending on the type of action used, the URLs may match a combination |
771 | of the controller namespace, the arguments passed to the action |
772 | attribute, and the name of the subroutine. |
cb93c9d7 |
773 | |
774 | =over 4 |
775 | |
d6ea2bcb |
776 | =item * B<Controller namespaces> |
777 | |
778 | The namespace is a modified form of the component's class (package) |
779 | name. This modified class name excludes the parts that have a |
780 | pre-defined meaning in Catalyst ("MyApp::Controller" in the above |
781 | example), replaces "::" with "/", and converts the name to lower case. |
782 | See L</Components> for a full explanation of the pre-defined meaning |
783 | of Catalyst component class names. |
784 | |
785 | =item * B<Overriding the namespace> |
786 | |
19a5b486 |
787 | Note that I<< __PACKAGE__->config->(namespace => ... ) >> can be used to override the |
d6ea2bcb |
788 | current namespace when matching. So: |
789 | |
790 | package MyApp::Controller::Example; |
791 | |
792 | would normally use 'example' as its namespace for matching, but if |
793 | this is specially overridden with |
794 | |
19a5b486 |
795 | __PACKAGE__->config( namespace => 'thing' ); |
d6ea2bcb |
796 | |
797 | it matches using the namespace 'thing' instead. |
798 | |
cb93c9d7 |
799 | =item * B<Application Wide Actions> |
800 | |
d6ea2bcb |
801 | MyApp::Controller::Root, as created by the catalyst.pl script, will |
802 | typically contain actions which are called for the top level of the |
803 | application (e.g. http://localhost:3000/ ): |
cb93c9d7 |
804 | |
805 | package MyApp::Controller::Root; |
806 | use base 'Catalyst::Controller'; |
807 | # Sets the actions in this controller to be registered with no prefix |
808 | # so they function identically to actions created in MyApp.pm |
19a5b486 |
809 | __PACKAGE__->config( namespace => ''); |
4299d9f5 |
810 | sub default : Path { |
cb93c9d7 |
811 | my ( $self, $context ) = @_; |
4299d9f5 |
812 | $context->response->status(404); |
813 | $context->response->body('404 not found'); |
cb93c9d7 |
814 | } |
815 | 1; |
816 | |
d6ea2bcb |
817 | |
818 | The code |
819 | |
19a5b486 |
820 | __PACKAGE__->config( namespace => '' ); |
d6ea2bcb |
821 | |
822 | makes the controller act as if its namespace is empty. As you'll see |
823 | below, an empty namespace makes many of the URL-matching attributes, |
824 | such as :Path, :Local and :Global matches, match at the start of the |
825 | URL path. |
826 | |
cb93c9d7 |
827 | =back |
828 | |
829 | =head4 Action types |
830 | |
d6ea2bcb |
831 | Catalyst supports several types of actions. These mainly correspond |
832 | to ways of matching a URL to an action subroutine. Internally, these |
833 | matching types are implemented by L<Catalyst::DispatchType>-derived |
834 | classes; the documentation there can be helpful in seeing how they |
835 | work. |
836 | |
837 | They will all attempt to match the start of the path. The remainder |
838 | of the path is passed as arguments. |
cb93c9d7 |
839 | |
840 | =over 4 |
841 | |
d6ea2bcb |
842 | =item * Namespace-prefixed (C<:Local>) |
843 | |
b1a08fe1 |
844 | package MyApp::Controller::My::Controller; |
d6ea2bcb |
845 | sub foo : Local { } |
846 | |
847 | Matches any URL beginning with> http://localhost:3000/my/controller/foo. The namespace and |
848 | subroutine name together determine the path. |
849 | |
0a52c718 |
850 | =item * Root-level (C<:Global>) |
d6ea2bcb |
851 | |
852 | package MyApp::Controller::Foo; |
853 | sub foo : Global { } |
854 | |
855 | Matches http://localhost:3000/foo - that is, the action is mapped |
b1a08fe1 |
856 | directly to the controller namespace, ignoring the function name. |
d6ea2bcb |
857 | |
0a52c718 |
858 | C<:Global> always matches from root: it is sugar for C<:Path('/methodname')>. |
859 | C<:Local> is simply sugar for C<:Path('methodname')>, which takes the package |
860 | namespace as described above. |
d6ea2bcb |
861 | |
862 | package MyApp::Controller::Root; |
19a5b486 |
863 | __PACKAGE__->config( namespace => ''); |
d6ea2bcb |
864 | sub foo : Local { } |
865 | |
866 | Use whichever makes the most sense for your application. |
867 | |
845ef405 |
868 | =item * Changing handler behaviour: eating arguments (C<:Args>) |
d6ea2bcb |
869 | |
870 | Args is not an action type per se, but an action modifier - it adds a |
871 | match restriction to any action it's provided to, additionally |
872 | requiring as many path parts as are specified for the action to be |
873 | matched. For example, in MyApp::Controller::Foo, |
874 | |
875 | sub bar :Local |
876 | |
877 | would match any URL starting /foo/bar. To restrict this you can do |
878 | |
879 | sub bar :Local :Args(1) |
880 | |
881 | to only match URLs starting /foo/bar/* - with one additional path |
882 | element required after 'bar'. |
883 | |
b1a08fe1 |
884 | NOTE that adding C<:Args(0)> and missing out :Args completely are B<not> |
845ef405 |
885 | the same thing. |
886 | |
b1a08fe1 |
887 | C<:Args(0)> means that no arguments are taken. Thus, the URL and path must |
845ef405 |
888 | match precisely. |
889 | |
b1a08fe1 |
890 | No :Args at all means that B<any number> of arguments are taken. Thus, any |
0a52c718 |
891 | URL that B<starts with> the controller's path will match. Obviously, this means |
892 | you cannot chain from an action that does not specify args, as the next action |
893 | in the chain will be swallowed as an arg to the first! |
845ef405 |
894 | |
895 | |
d6ea2bcb |
896 | =item * Literal match (C<:Path>) |
897 | |
898 | C<Path> actions match things starting with a precise specified path, |
899 | and nothing else. |
900 | |
901 | C<Path> actions without a leading forward slash match a specified path |
902 | relative to their current namespace. This example matches URLs |
903 | starting http://localhost:3000/my/controller/foo/bar : |
cb93c9d7 |
904 | |
905 | package MyApp::Controller::My::Controller; |
906 | sub bar : Path('foo/bar') { } |
907 | |
d6ea2bcb |
908 | C<Path> actions B<with> a leading slash ignore their namespace, and |
909 | match from the start of the URL path. Example: |
cb93c9d7 |
910 | |
911 | package MyApp::Controller::My::Controller; |
912 | sub bar : Path('/foo/bar') { } |
913 | |
d6ea2bcb |
914 | This matches URLs beginning http://localhost:3000/foo/bar. |
915 | |
916 | Empty C<Path> definitions match on the namespace only, exactly like |
917 | C<:Global>. |
cb93c9d7 |
918 | |
919 | package MyApp::Controller::My::Controller; |
920 | sub bar : Path { } |
921 | |
d6ea2bcb |
922 | The above code matches http://localhost:3000/my/controller. |
923 | |
924 | Actions with the C<:Local> attribute are similarly equivalent to |
925 | C<:Path('action_name')>: |
cb93c9d7 |
926 | |
b1a08fe1 |
927 | sub foo : Local { } |
cb93c9d7 |
928 | |
b1a08fe1 |
929 | is equivalent to |
d6ea2bcb |
930 | |
931 | sub foo : Path('foo') { } |
932 | |
933 | =item * Pattern-match (C<:Regex> and C<:LocalRegex>) |
b1a08fe1 |
934 | |
d6ea2bcb |
935 | package MyApp::Controller::My::Controller; |
cb93c9d7 |
936 | sub bar : Regex('^item(\d+)/order(\d+)$') { } |
937 | |
d6ea2bcb |
938 | This matches any URL that matches the pattern in the action key, e.g. |
cb93c9d7 |
939 | http://localhost:3000/item23/order42. The '' around the regexp is |
940 | optional, but perltidy likes it. :) |
941 | |
d6ea2bcb |
942 | C<:Regex> matches act globally, i.e. without reference to the namespace |
943 | from which they are called. So the above will B<not> match |
944 | http://localhost:3000/my/controller/item23/order42 - use a |
945 | C<:LocalRegex> action instead. |
cb93c9d7 |
946 | |
d6ea2bcb |
947 | package MyApp::Controller::My::Controller; |
cb93c9d7 |
948 | sub bar : LocalRegex('^widget(\d+)$') { } |
949 | |
d6ea2bcb |
950 | C<:LocalRegex> actions act locally, i.e. the namespace is matched |
951 | first. The above example would match urls like |
952 | http://localhost:3000/my/controller/widget23. |
cb93c9d7 |
953 | |
d6ea2bcb |
954 | If you omit the "C<^>" from either sort of regex, then it will match any depth |
955 | from the base path: |
cb93c9d7 |
956 | |
957 | package MyApp::Controller::Catalog; |
958 | sub bar : LocalRegex('widget(\d+)$') { } |
959 | |
d6ea2bcb |
960 | This differs from the previous example in that it will match |
961 | http://localhost:3000/my/controller/foo/widget23 - and a number of |
962 | other paths. |
cb93c9d7 |
963 | |
d6ea2bcb |
964 | For both C<:LocalRegex> and C<:Regex> actions, if you use capturing |
965 | parentheses to extract values within the matching URL, those values |
966 | are available in the C<$c-E<gt>req-E<gt>captures> array. In the above |
967 | example, "widget23" would capture "23" in the above example, and |
968 | C<$c-E<gt>req-E<gt>captures-E<gt>[0]> would be "23". If you want to |
969 | pass arguments at the end of your URL, you must use regex action |
970 | keys. See L</URL Path Handling> below. |
cb93c9d7 |
971 | |
d6ea2bcb |
972 | =item * Chained handlers (C<:Chained>) |
cb93c9d7 |
973 | |
974 | Catalyst also provides a method to build and dispatch chains of actions, |
975 | like |
976 | |
977 | sub catalog : Chained : CaptureArgs(1) { |
978 | my ( $self, $c, $arg ) = @_; |
979 | ... |
980 | } |
981 | |
982 | sub item : Chained('catalog') : Args(1) { |
983 | my ( $self, $c, $arg ) = @_; |
984 | ... |
985 | } |
986 | |
d6ea2bcb |
987 | to handle a C</catalog/*/item/*> path. Matching actions are called |
988 | one after another - C<catalog()> gets called and handed one path |
989 | element, then C<item()> gets called with another one. For further |
990 | information about this dispatch type, please see |
991 | L<Catalyst::DispatchType::Chained>. |
cb93c9d7 |
992 | |
993 | =item * B<Private> |
994 | |
995 | sub foo : Private { } |
996 | |
d6ea2bcb |
997 | This will never match a URL - it provides a private action which can |
998 | be called programmatically from within Catalyst, but is never called |
999 | automatically due to the URL being requested. |
1000 | |
1001 | Catalyst's C<:Private> attribute is exclusive and doesn't work with other |
1002 | attributes (so will not work combined with C<:Path> or C<:Chained> |
1003 | attributes, for instance). |
1004 | |
1005 | Private actions can only be executed explicitly from inside a Catalyst |
1006 | application. You might do this in your controllers by calling |
1007 | catalyst methods such as C<forward> or C<detach> to fire them: |
cb93c9d7 |
1008 | |
1009 | $c->forward('foo'); |
09f13e1d |
1010 | # or |
1011 | $c->detach('foo'); |
cb93c9d7 |
1012 | |
d6ea2bcb |
1013 | See L</Flow Control> for a full explanation of how you can pass |
1014 | requests on to other actions. Note that, as discussed there, when |
1015 | forwarding from another component, you must use the absolute path to |
1016 | the method, so that a private C<bar> method in your |
1017 | C<MyApp::Controller::Catalog::Order::Process> controller must, if |
1018 | called from elsewhere, be reached with |
cb93c9d7 |
1019 | C<$c-E<gt>forward('/catalog/order/process/bar')>. |
1020 | |
cb93c9d7 |
1021 | =back |
1022 | |
d6ea2bcb |
1023 | B<Note:> After seeing these examples, you probably wonder what the |
1024 | point is of defining subroutine names for regex and path |
1025 | actions. However, every public action is also a private one with a |
1026 | path corresponding to its namespace and subroutine name, so you have |
1027 | one unified way of addressing components in your C<forward>s. |
1028 | |
1029 | =head4 Built-in special actions |
cb93c9d7 |
1030 | |
d6ea2bcb |
1031 | If present, the special actions C< index >, C< auto >, C<begin>, |
1032 | C<end> and C< default > are called at certain points in the request |
1033 | cycle. |
cb93c9d7 |
1034 | |
1035 | In response to specific application states, Catalyst will automatically |
d6ea2bcb |
1036 | call these built-in actions in your application class: |
cb93c9d7 |
1037 | |
1038 | =over 4 |
1039 | |
4299d9f5 |
1040 | =item * B<default : Path> |
cb93c9d7 |
1041 | |
d6ea2bcb |
1042 | This is called when no other action matches. It could be used, for |
1043 | example, for displaying a generic frontpage for the main app, or an |
1044 | error page for individual controllers. B<Note>: in older Catalyst |
1045 | applications you will see C<default : Private> which is roughly |
1046 | speaking equivalent. |
cb93c9d7 |
1047 | |
cb93c9d7 |
1048 | |
4299d9f5 |
1049 | =item * B<index : Path : Args (0) > |
cb93c9d7 |
1050 | |
4299d9f5 |
1051 | C<index> is much like C<default> except that it takes no arguments and |
1052 | it is weighted slightly higher in the matching process. It is useful |
1053 | as a static entry point to a controller, e.g. to have a static welcome |
1054 | page. Note that it's also weighted higher than Path. Actually the sub |
1055 | name C<index> can be called anything you want. The sub attributes are |
955bdf3d |
1056 | what determines the behaviour of the action. B<Note>: in older |
1057 | Catalyst applications, you will see C<index : Private> used, which is |
1058 | roughly speaking equivalent. |
cb93c9d7 |
1059 | |
1060 | =item * B<begin : Private> |
1061 | |
d6ea2bcb |
1062 | Called at the beginning of a request, once the controller that will |
1063 | run has been identified, but before any URL-matching actions are |
1064 | called. Catalyst will call the C<begin> function in the controller |
1065 | which contains the action matching the URL. |
cb93c9d7 |
1066 | |
1067 | =item * B<end : Private> |
1068 | |
d6ea2bcb |
1069 | Called at the end of a request, after all URL-matching actions are called. |
1070 | Catalyst will call the C<end> function in the controller |
1071 | which contains the action matching the URL. |
1072 | |
1073 | =item * B<auto : Private> |
1074 | |
1075 | In addition to the normal built-in actions, you have a special action |
1076 | for making chains, C<auto>. C<auto> actions will be run after any |
1077 | C<begin>, but before your URL-matching action is processed. Unlike the other |
1078 | built-ins, multiple C<auto> actions can be called; they will be |
1079 | called in turn, starting with the application class and going through |
1080 | to the most specific class. |
cb93c9d7 |
1081 | |
1082 | =back |
1083 | |
1084 | =head4 Built-in actions in controllers/autochaining |
1085 | |
f76813a2 |
1086 | package MyApp::Controller::Foo; |
cb93c9d7 |
1087 | sub begin : Private { } |
4299d9f5 |
1088 | sub default : Path { } |
d6ea2bcb |
1089 | sub end : Path { } |
1090 | |
1091 | You can define built-in actions within your controllers as well as on |
1092 | your application class. In other words, for each of the three built-in |
1093 | actions above, only one will be run in any request cycle. Thus, if |
1094 | C<MyApp::Controller::Catalog::begin> exists, it will be run in place |
1095 | of C<MyApp::begin> if you're in the C<catalog> namespace, and |
1096 | C<MyApp::Controller::Catalog::Order::begin> would override this in |
cb93c9d7 |
1097 | turn. |
1098 | |
d6ea2bcb |
1099 | sub auto : Private { } |
cb93c9d7 |
1100 | |
d6ea2bcb |
1101 | C<auto>, however, doesn't override like this: providing they exist, |
a696baf6 |
1102 | C<MyApp::Controller::Root::auto>, C<MyApp::Controller::Catalog::auto> and |
d6ea2bcb |
1103 | C<MyApp::Catalog::Order::auto> would be called in turn. |
cb93c9d7 |
1104 | |
1105 | Here are some examples of the order in which the various built-ins |
1106 | would be called: |
1107 | |
1108 | =over 4 |
1109 | |
1110 | =item for a request for C</foo/foo> |
1111 | |
f76813a2 |
1112 | MyApp::Controller::Foo::auto |
cb93c9d7 |
1113 | MyApp::Controller::Foo::default # in the absence of MyApp::Controller::Foo::Foo |
f76813a2 |
1114 | MyApp::Controller::Foo::end |
cb93c9d7 |
1115 | |
1116 | =item for a request for C</foo/bar/foo> |
1117 | |
1118 | MyApp::Controller::Foo::Bar::begin |
cb93c9d7 |
1119 | MyApp::Controller::Foo::auto |
1120 | MyApp::Controller::Foo::Bar::auto |
1121 | MyApp::Controller::Foo::Bar::default # for MyApp::Controller::Foo::Bar::foo |
1122 | MyApp::Controller::Foo::Bar::end |
1123 | |
1124 | =back |
1125 | |
1126 | The C<auto> action is also distinguished by the fact that you can break |
1127 | out of the processing chain by returning 0. If an C<auto> action returns |
1128 | 0, any remaining actions will be skipped, except for C<end>. So, for the |
1129 | request above, if the first auto returns false, the chain would look |
1130 | like this: |
1131 | |
1132 | =over 4 |
1133 | |
1134 | =item for a request for C</foo/bar/foo> where first C<auto> returns |
1135 | false |
1136 | |
1137 | MyApp::Controller::Foo::Bar::begin |
d6ea2bcb |
1138 | MyApp::Controller::Foo::auto # returns false, skips some calls: |
1139 | # MyApp::Controller::Foo::Bar::auto - never called |
1140 | # MyApp::Controller::Foo::Bar::foo - never called |
cb93c9d7 |
1141 | MyApp::Controller::Foo::Bar::end |
1142 | |
d6ea2bcb |
1143 | You can also C<die> in the auto action; in that case, the request will |
1144 | go straight to the finalize stage, without processing further |
1145 | actions. So in the above example, C<MyApp::Controller::Foo::Bar::end> |
1146 | is skipped as well. |
1147 | |
cb93c9d7 |
1148 | =back |
1149 | |
d6ea2bcb |
1150 | An example of why one might use C<auto> is an authentication action: |
1151 | you could set up a C<auto> action to handle authentication in your |
cb93c9d7 |
1152 | application class (which will always be called first), and if |
d6ea2bcb |
1153 | authentication fails, returning 0 would skip any remaining methods for |
1154 | that URL. |
cb93c9d7 |
1155 | |
1156 | B<Note:> Looking at it another way, C<auto> actions have to return a |
b1a08fe1 |
1157 | true value to continue processing! |
cb93c9d7 |
1158 | |
1159 | =head4 URL Path Handling |
1160 | |
d6ea2bcb |
1161 | You can pass arguments as part of the URL path, separated with forward |
1162 | slashes (/). If the action is a Regex or LocalRegex, the '$' anchor |
1163 | must be used. For example, suppose you want to handle |
1164 | C</foo/$bar/$baz>, where C<$bar> and C<$baz> may vary: |
cb93c9d7 |
1165 | |
1166 | sub foo : Regex('^foo$') { my ($self, $context, $bar, $baz) = @_; } |
1167 | |
1168 | But what if you also defined actions for C</foo/boo> and C</foo/boo/hoo>? |
1169 | |
1170 | sub boo : Path('foo/boo') { .. } |
1171 | sub hoo : Path('foo/boo/hoo') { .. } |
1172 | |
d6ea2bcb |
1173 | Catalyst matches actions in most specific to least specific order - that is, whatever matches the most pieces of the path wins: |
cb93c9d7 |
1174 | |
1175 | /foo/boo/hoo |
1176 | /foo/boo |
1177 | /foo # might be /foo/bar/baz but won't be /foo/boo/hoo |
1178 | |
1179 | So Catalyst would never mistakenly dispatch the first two URLs to the |
1180 | '^foo$' action. |
1181 | |
b1a08fe1 |
1182 | If a Regex or LocalRegex action doesn't use the '$' anchor, the action will |
1183 | still match a URL containing arguments; however the arguments won't be |
d6ea2bcb |
1184 | available via C<@_>, because the Regex will 'eat' them. |
1185 | |
1186 | Beware! If you write two matchers, that match the same path, with the |
1187 | same specificity (that is, they match the same quantity of the path), |
1188 | there's no guarantee which will actually get called. Non-regex |
1189 | matchers get tried first, followed by regex ones, but if you have, for |
1190 | instance: |
1191 | |
1192 | package MyApp::Controller::Root; |
1193 | |
1194 | sub match1 :Path('/a/b') { } |
1195 | |
1196 | package MyApp::Controller::A; |
1197 | |
1198 | sub b :Local { } # Matches /a/b |
1199 | |
1200 | then Catalyst will call the one it finds first. In summary, Don't Do |
1201 | This. |
cb93c9d7 |
1202 | |
d6ea2bcb |
1203 | =head4 Query Parameter Processing |
cb93c9d7 |
1204 | |
1205 | Parameters passed in the URL query string are handled with methods in |
1206 | the L<Catalyst::Request> class. The C<param> method is functionally |
1207 | equivalent to the C<param> method of C<CGI.pm> and can be used in |
1208 | modules that require this. |
1209 | |
1210 | # http://localhost:3000/catalog/view/?category=hardware&page=3 |
1211 | my $category = $c->req->param('category'); |
1212 | my $current_page = $c->req->param('page') || 1; |
1213 | |
1214 | # multiple values for single parameter name |
b1a08fe1 |
1215 | my @values = $c->req->param('scrolling_list'); |
cb93c9d7 |
1216 | |
1217 | # DFV requires a CGI.pm-like input hash |
1218 | my $results = Data::FormValidator->check($c->req->params, \%dfv_profile); |
1219 | |
1220 | =head3 Flow Control |
1221 | |
1222 | You control the application flow with the C<forward> method, which |
1223 | accepts the key of an action to execute. This can be an action in the |
1224 | same or another Catalyst controller, or a Class name, optionally |
1225 | followed by a method name. After a C<forward>, the control flow will |
1226 | return to the method from which the C<forward> was issued. |
1227 | |
1228 | A C<forward> is similar to a method call. The main differences are that |
1229 | it wraps the call in an C<eval> to allow exception handling; it |
1230 | automatically passes along the context object (C<$c> or C<$context>); |
1231 | and it allows profiling of each call (displayed in the log with |
1232 | debugging enabled). |
1233 | |
1234 | sub hello : Global { |
1235 | my ( $self, $c ) = @_; |
1236 | $c->stash->{message} = 'Hello World!'; |
1237 | $c->forward('check_message'); # $c is automatically included |
1238 | } |
1239 | |
1240 | sub check_message : Private { |
1241 | my ( $self, $c ) = @_; |
1242 | return unless $c->stash->{message}; |
1243 | $c->forward('show_message'); |
1244 | } |
1245 | |
1246 | sub show_message : Private { |
1247 | my ( $self, $c ) = @_; |
1248 | $c->res->body( $c->stash->{message} ); |
1249 | } |
1250 | |
1251 | A C<forward> does not create a new request, so your request object |
1252 | (C<$c-E<gt>req>) will remain unchanged. This is a key difference between |
1253 | using C<forward> and issuing a redirect. |
1254 | |
1255 | You can pass new arguments to a C<forward> by adding them |
1256 | in an anonymous array. In this case C<$c-E<gt>req-E<gt>args> |
1257 | will be changed for the duration of the C<forward> only; upon |
1258 | return, the original value of C<$c-E<gt>req-E<gt>args> will |
1259 | be reset. |
1260 | |
1261 | sub hello : Global { |
1262 | my ( $self, $c ) = @_; |
1263 | $c->stash->{message} = 'Hello World!'; |
1264 | $c->forward('check_message',[qw/test1/]); |
1265 | # now $c->req->args is back to what it was before |
1266 | } |
1267 | |
eecdf6ee |
1268 | sub check_message : Action { |
1269 | my ( $self, $c, $first_argument ) = @_; |
1270 | my $also_first_argument = $c->req->args->[0]; # now = 'test1' |
cb93c9d7 |
1271 | # do something... |
1272 | } |
1273 | |
1274 | As you can see from these examples, you can just use the method name as |
1275 | long as you are referring to methods in the same controller. If you want |
1276 | to forward to a method in another controller, or the main application, |
1277 | you will have to refer to the method by absolute path. |
1278 | |
1279 | $c->forward('/my/controller/action'); |
1280 | $c->forward('/default'); # calls default in main application |
1281 | |
eecdf6ee |
1282 | You can also forward to classes and methods. |
08cb655f |
1283 | |
cb93c9d7 |
1284 | sub hello : Global { |
1285 | my ( $self, $c ) = @_; |
eecdf6ee |
1286 | $c->forward(qw/MyApp::View:Hello say_hello/); |
cb93c9d7 |
1287 | } |
1288 | |
1289 | sub bye : Global { |
1290 | my ( $self, $c ) = @_; |
1291 | $c->forward('MyApp::Model::Hello'); # no method: will try 'process' |
1292 | } |
1293 | |
eecdf6ee |
1294 | package MyApp::View::Hello; |
cb93c9d7 |
1295 | |
1296 | sub say_hello { |
1297 | my ( $self, $c ) = @_; |
1298 | $c->res->body('Hello World!'); |
1299 | } |
1300 | |
1301 | sub process { |
1302 | my ( $self, $c ) = @_; |
1303 | $c->res->body('Goodbye World!'); |
1304 | } |
1305 | |
eecdf6ee |
1306 | This mechanism is used by L<Catalyst::Action::RenderView> to forward |
1307 | to the C<process> method in a view class. |
1308 | |
1309 | It should be noted that whilst forward is useful, it is not the only way |
1310 | of calling other code in Catalyst. Forward just gives you stats in the debug |
1311 | screen, wraps the code you're calling in an exception handler and localises |
1312 | C<< $c->request->args >>. |
1313 | |
1314 | If you don't want or need these features then it's perfectly acceptable |
1315 | (and faster) to do something like this: |
1316 | |
e8556dab |
1317 | sub hello : Global { |
1318 | my ( $self, $c ) = @_; |
1319 | $c->stash->{message} = 'Hello World!'; |
1320 | $self->check_message( $c, 'test1' ); |
1321 | } |
1322 | |
1323 | sub check_message { |
1324 | my ( $self, $c, $first_argument ) = @_; |
1325 | # do something... |
1326 | } |
eecdf6ee |
1327 | |
cb93c9d7 |
1328 | Note that C<forward> returns to the calling action and continues |
1329 | processing after the action finishes. If you want all further processing |
1330 | in the calling action to stop, use C<detach> instead, which will execute |
1331 | the C<detach>ed action and not return to the calling sub. In both cases, |
1332 | Catalyst will automatically try to call process() if you omit the |
1333 | method. |
1334 | |
cb93c9d7 |
1335 | =head3 Testing |
1336 | |
1337 | Catalyst has a built-in http server for testing or local |
1338 | deployment. (Later, you can easily use a more powerful server, for |
1339 | example Apache/mod_perl or FastCGI, in a production environment.) |
1340 | |
1341 | Start your application on the command line... |
1342 | |
1343 | script/myapp_server.pl |
1344 | |
1345 | ...then visit http://localhost:3000/ in a browser to view the output. |
1346 | |
1347 | You can also do it all from the command line: |
1348 | |
1349 | script/myapp_test.pl http://localhost/ |
1350 | |
1351 | Catalyst has a number of tools for actual regression testing of |
1352 | applications. The helper scripts will automatically generate basic tests |
1353 | that can be extended as you develop your project. To write your own |
1354 | comprehensive test scripts, L<Test::WWW::Mechanize::Catalyst> is an |
1355 | invaluable tool. |
1356 | |
1357 | For more testing ideas, see L<Catalyst::Manual::Tutorial::Testing>. |
1358 | |
1359 | Have fun! |
1360 | |
1361 | =head1 SEE ALSO |
1362 | |
1363 | =over 4 |
1364 | |
1365 | =item * L<Catalyst::Manual::About> |
1366 | |
1367 | =item * L<Catalyst::Manual::Tutorial> |
1368 | |
1369 | =item * L<Catalyst> |
1370 | |
1371 | =back |
1372 | |
1373 | =head1 SUPPORT |
1374 | |
1375 | IRC: |
1376 | |
1377 | Join #catalyst on irc.perl.org. |
1378 | Join #catalyst-dev on irc.perl.org to help with development. |
1379 | |
1380 | Mailing lists: |
1381 | |
392906f2 |
1382 | http://lists.scsys.co.uk/mailman/listinfo/catalyst |
1383 | http://lists.scsys.co.uk/mailman/listinfo/catalyst-dev |
cb93c9d7 |
1384 | |
fed95b6c |
1385 | Wiki: |
1386 | |
1387 | http://dev.catalystframework.org/wiki |
1388 | |
1389 | FAQ: |
1390 | |
1391 | http://dev.catalystframework.org/wiki/faq |
1392 | |
bbddff00 |
1393 | =head1 AUTHORS |
cb93c9d7 |
1394 | |
bbddff00 |
1395 | Catalyst Contributors, see Catalyst.pm |
cb93c9d7 |
1396 | |
1397 | =head1 COPYRIGHT |
1398 | |
bbddff00 |
1399 | This library is free software. You can redistribute it and/or modify it under |
1400 | the same terms as Perl itself. |
b1a08fe1 |
1401 | |
1402 | =cut |