Commit | Line | Data |
fc7ec1d9 |
1 | =head1 NAME |
2 | |
3 | Catalyst::Manual::Intro - Introduction to Catalyst |
4 | |
5 | =head1 DESCRIPTION |
6 | |
670b3d78 |
7 | This is a brief introduction to Catalyst. It explains the most important |
aa2b0d97 |
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>. |
6c5c02ba |
11 | For a systematic step-by-step introduction to writing an application |
12 | with Catalyst, see L<Catalyst::Manual::Tutorial>. |
fc7ec1d9 |
13 | |
14 | =head2 What is Catalyst? |
15 | |
129cfe74 |
16 | Catalyst is an elegant web application framework, extremely flexible yet |
56d8daeb |
17 | extremely simple. It's similar to Ruby on Rails, Spring (Java), and |
6c5c02ba |
18 | L<Maypole>, upon which it was originally based. Its most important |
19 | design philosphy is to provide easy access to all the tools you need to |
20 | develop web applications, with few restrictions on how you need to use |
21 | these tools. Under Catalyst, it is always possible to do things in a |
22 | different way. However, this does mean that it is always possible to do |
23 | things in a different way. Other web frameworks are simpler to use and |
24 | easy to get up and running, but achieve this by locking the programmer |
25 | into a single set of tools. Catalyst's emphasis on flexibility means |
26 | that you have to think more to use it. We view this as a feature. |
fc7ec1d9 |
27 | |
28 | =head3 MVC |
29 | |
e178a66a |
30 | Catalyst follows the Model-View-Controller (MVC) design pattern, |
31 | allowing you to easily separate concerns, like content, presentation, |
32 | and flow control, into separate modules. This separation allows you to |
33 | modify code that handles one concern without affecting code that handles |
34 | the others. Catalyst promotes the re-use of existing Perl modules that |
35 | already handle common web application concerns well. |
fc7ec1d9 |
36 | |
7f71afbe |
37 | Here's how the Model, View, and Controller map to those concerns, with |
38 | examples of well-known Perl modules you may want to use for each. |
fc7ec1d9 |
39 | |
40 | =over 4 |
41 | |
4a6895ce |
42 | =item * B<Model> |
fc7ec1d9 |
43 | |
e112461a |
44 | Access and modify content (data). L<DBIx::Class>, L<Class::DBI>, |
6c5c02ba |
45 | L<Xapian>, L<Net::LDAP>... |
fc7ec1d9 |
46 | |
4a6895ce |
47 | =item * B<View> |
fc7ec1d9 |
48 | |
e178a66a |
49 | Present content to the user. L<Template Toolkit|Template>, |
50 | L<Mason|HTML::Mason>, L<HTML::Template>... |
fc7ec1d9 |
51 | |
4a6895ce |
52 | =item * B<Controller> |
fc7ec1d9 |
53 | |
129cfe74 |
54 | Control the whole request phase, check parameters, dispatch actions, flow |
56d8daeb |
55 | control. Catalyst itself! |
fc7ec1d9 |
56 | |
57 | =back |
58 | |
d4ef4999 |
59 | If you're unfamiliar with MVC and design patterns, you may want to |
60 | check out the original book on the subject, I<Design Patterns>, by |
61 | Gamma, Helm, Johnson, and Vlissides, also known as the Gang of Four |
62 | (GoF). Many, many web application frameworks are based on MVC, which |
63 | is becoming a popular design method for web applications. |
fc7ec1d9 |
64 | |
65 | =head3 Flexibility |
66 | |
7f71afbe |
67 | Catalyst is much more flexible than many other frameworks. Rest assured |
68 | you can use your favorite Perl modules with Catalyst. |
fc7ec1d9 |
69 | |
70 | =over 4 |
71 | |
72d9bfc7 |
72 | =item * B<Multiple Models, Views, and Controllers> |
fc7ec1d9 |
73 | |
e178a66a |
74 | To build a Catalyst application, you handle each type of concern inside |
75 | special modules called L</Components>. Often this code will be very |
76 | simple, just calling out to Perl modules like those listed above under |
77 | L</MVC>. Catalyst handles these components in a very flexible way. Use |
78 | as many Models, Views, and Controllers as you like, using as many |
79 | different Perl modules as you like, all in the same application. Want to |
80 | manipulate multiple databases, and retrieve some data via LDAP? No |
81 | problem. Want to present data from the same Model using L<Template |
82 | Toolkit|Template> and L<PDF::Template>? Easy. |
fc7ec1d9 |
83 | |
cda8d1ac |
84 | =item * B<Reuseable Components> |
fc7ec1d9 |
85 | |
e178a66a |
86 | Not only does Catalyst promote the re-use of already existing Perl |
87 | modules, it also allows you to re-use your Catalyst components in |
88 | multiple Catalyst applications. |
fc7ec1d9 |
89 | |
4a6895ce |
90 | =item * B<Unrestrained URL-to-Action Dispatching> |
fc7ec1d9 |
91 | |
cccc887d |
92 | Catalyst allows you to dispatch any URLs to any application L</Actions>, |
e178a66a |
93 | even through regular expressions! Unlike most other frameworks, it |
94 | doesn't require mod_rewrite or class and method names in URLs. |
fc7ec1d9 |
95 | |
e178a66a |
96 | With Catalyst you register your actions and address them directly. For |
97 | example: |
fc7ec1d9 |
98 | |
e3dc9d78 |
99 | sub hello : Global { |
fc7ec1d9 |
100 | my ( $self, $context ) = @_; |
66f6e959 |
101 | $context->response->body('Hello World!'); |
5a8ed4fe |
102 | } |
fc7ec1d9 |
103 | |
104 | Now http://localhost:3000/hello prints "Hello World!". |
105 | |
7f71afbe |
106 | =item * B<Support for CGI, mod_perl, Apache::Request, FastCGI> |
fc7ec1d9 |
107 | |
7f71afbe |
108 | Use L<Catalyst::Engine::Apache> or L<Catalyst::Engine::CGI>. Other |
109 | engines are also available. |
fc7ec1d9 |
110 | |
111 | =back |
112 | |
113 | =head3 Simplicity |
114 | |
e178a66a |
115 | The best part is that Catalyst implements all this flexibility in a very |
116 | simple way. |
fc7ec1d9 |
117 | |
6f4e1683 |
118 | =over 4 |
119 | |
4a6895ce |
120 | =item * B<Building Block Interface> |
fc7ec1d9 |
121 | |
e178a66a |
122 | Components interoperate very smoothly. For example, Catalyst |
cccc887d |
123 | automatically makes a L</Context> object available to every |
e178a66a |
124 | component. Via the context, you can access the request object, share |
125 | data between components, and control the flow of your |
126 | application. Building a Catalyst application feels a lot like snapping |
129cfe74 |
127 | together toy building blocks, and everything just works. |
fc7ec1d9 |
128 | |
4a6895ce |
129 | =item * B<Component Auto-Discovery> |
fc7ec1d9 |
130 | |
e178a66a |
131 | No need to C<use> all of your components. Catalyst automatically finds |
132 | and loads them. |
fc7ec1d9 |
133 | |
4a6895ce |
134 | =item * B<Pre-Built Components for Popular Modules> |
fc7ec1d9 |
135 | |
e112461a |
136 | See L<Catalyst::Model::DBIC::Schema> for L<DBIx::Class>, or |
137 | L<Catalyst::View::TT> for L<Template Toolkit|Template>. |
fc7ec1d9 |
138 | |
72d9bfc7 |
139 | =item * B<Built-in Test Framework> |
fc7ec1d9 |
140 | |
e178a66a |
141 | Catalyst comes with a built-in, lightweight http server and test |
142 | framework, making it easy to test applications from the command line. |
fc7ec1d9 |
143 | |
4a6895ce |
144 | =item * B<Helper Scripts> |
fc7ec1d9 |
145 | |
e178a66a |
146 | Catalyst provides helper scripts to quickly generate running starter |
7f71afbe |
147 | code for components and unit tests. Install L<Catalyst::Devel> and see |
148 | L<Catalyst::Helper>. |
fc7ec1d9 |
149 | |
6f4e1683 |
150 | =back |
151 | |
fc7ec1d9 |
152 | =head2 Quickstart |
153 | |
e178a66a |
154 | Here's how to install Catalyst and get a simple application up and |
155 | running, using the helper scripts described above. |
fc7ec1d9 |
156 | |
157 | =head3 Install |
158 | |
7f71afbe |
159 | Installation of Catalyst can be a time-consuming and frustrating |
160 | effort, due to its large number of dependencies. The easiest way |
161 | to get up and running is to use Matt Trout's C<cat-install> |
162 | script, from L<http://www.shadowcatsystems.co.uk/static/cat-install>, |
163 | and then install L<Catalyst::Devel>. |
164 | |
165 | # perl cat-install |
166 | # perl -MCPAN -e 'install Catalyst::Devel' |
fc7ec1d9 |
167 | |
168 | =head3 Setup |
169 | |
2feb6632 |
170 | $ catalyst.pl MyApp |
b33ed88c |
171 | # output omitted |
2feb6632 |
172 | $ cd MyApp |
ac4a0ae0 |
173 | $ script/myapp_create.pl controller Library::Login |
fc7ec1d9 |
174 | |
175 | =head3 Run |
176 | |
b33ed88c |
177 | $ script/myapp_server.pl |
fc7ec1d9 |
178 | |
129cfe74 |
179 | Now visit these locations with your favorite browser or user agent to see |
180 | Catalyst in action: |
fc7ec1d9 |
181 | |
51aec62b |
182 | (NOTE: Although we create a controller here, we don't actually use it. |
183 | Both of these URLs should take you to the welcome page.) |
184 | |
185 | |
fc7ec1d9 |
186 | =over 4 |
187 | |
188 | =item http://localhost:3000/ |
189 | |
ac4a0ae0 |
190 | =item http://localhost:3000/library/login/ |
fc7ec1d9 |
191 | |
192 | =back |
193 | |
56d8daeb |
194 | Easy! |
fc7ec1d9 |
195 | |
196 | =head2 How It Works |
197 | |
e178a66a |
198 | Let's see how Catalyst works, by taking a closer look at the components |
199 | and other parts of a Catalyst application. |
fc7ec1d9 |
200 | |
201 | =head3 Application Class |
202 | |
e178a66a |
203 | In addition to the Model, View, and Controller components, there's a |
204 | single class that represents your application itself. This is where you |
c37916b0 |
205 | configure your application, load plugins, and extend Catalyst. |
fc7ec1d9 |
206 | |
207 | package MyApp; |
208 | |
209 | use strict; |
7f71afbe |
210 | use Catalyst qw/-Debug/; # Add other plugins here, e.g. |
211 | # for session support |
fc7ec1d9 |
212 | |
213 | MyApp->config( |
214 | name => 'My Application', |
fc7ec1d9 |
215 | |
b33ed88c |
216 | # You can put anything else you want in here: |
217 | my_configuration_variable => 'something', |
fc7ec1d9 |
218 | ); |
fc7ec1d9 |
219 | 1; |
220 | |
6c5c02ba |
221 | In older versions of Catalyst, the application class was where you put |
222 | global actions. However, as of version 5.66, the recommended practice is |
3c4913b0 |
223 | to place such actions in a special Root controller (see L</Actions>, |
224 | below), to avoid namespace collisions. |
6c5c02ba |
225 | |
fc7ec1d9 |
226 | =over 4 |
227 | |
4a6895ce |
228 | =item * B<name> |
fc7ec1d9 |
229 | |
56d8daeb |
230 | The name of your application. |
fc7ec1d9 |
231 | |
fc7ec1d9 |
232 | =back |
233 | |
e178a66a |
234 | Optionally, you can specify a B<root> parameter for templates and static |
235 | data. If omitted, Catalyst will try to auto-detect the directory's |
236 | location. You can define as many parameters as you want for plugins or |
237 | whatever you need. You can access them anywhere in your application via |
238 | C<$context-E<gt>config-E<gt>{$param_name}>. |
fc7ec1d9 |
239 | |
240 | =head3 Context |
241 | |
e178a66a |
242 | Catalyst automatically blesses a Context object into your application |
243 | class and makes it available everywhere in your application. Use the |
cccc887d |
244 | Context to directly interact with Catalyst and glue your L</Components> |
e178a66a |
245 | together. For example, if you need to use the Context from within a |
246 | Template Toolkit template, it's already there: |
c42f5bbf |
247 | |
248 | <h1>Welcome to [% c.config.name %]!</h1> |
fc7ec1d9 |
249 | |
e178a66a |
250 | As illustrated in our URL-to-Action dispatching example, the Context is |
251 | always the second method parameter, behind the Component object |
252 | reference or class name itself. Previously we called it C<$context> for |
253 | clarity, but most Catalyst developers just call it C<$c>: |
fc7ec1d9 |
254 | |
e3dc9d78 |
255 | sub hello : Global { |
fc7ec1d9 |
256 | my ( $self, $c ) = @_; |
66f6e959 |
257 | $c->res->body('Hello World!'); |
5a8ed4fe |
258 | } |
fc7ec1d9 |
259 | |
260 | The Context contains several important objects: |
261 | |
262 | =over 4 |
263 | |
264 | =item * L<Catalyst::Request> |
265 | |
266 | $c->request |
267 | $c->req # alias |
268 | |
129cfe74 |
269 | The request object contains all kinds of request-specific information, like |
270 | query parameters, cookies, uploads, headers, and more. |
fc7ec1d9 |
271 | |
272 | $c->req->params->{foo}; |
273 | $c->req->cookies->{sessionid}; |
274 | $c->req->headers->content_type; |
275 | $c->req->base; |
3c4913b0 |
276 | $c->req->uri_with( { page = $pager->next_page } ); |
fc7ec1d9 |
277 | |
afdca3a3 |
278 | =item * L<Catalyst::Response> |
fc7ec1d9 |
279 | |
280 | $c->response |
281 | $c->res # alias |
282 | |
129cfe74 |
283 | The response is like the request, but contains just response-specific |
284 | information. |
fc7ec1d9 |
285 | |
66f6e959 |
286 | $c->res->body('Hello World'); |
fc7ec1d9 |
287 | $c->res->status(404); |
288 | $c->res->redirect('http://oook.de'); |
289 | |
290 | =item * L<Catalyst::Config> |
291 | |
292 | $c->config |
fc7ec1d9 |
293 | $c->config->root; |
294 | $c->config->name; |
295 | |
296 | =item * L<Catalyst::Log> |
297 | |
298 | $c->log |
fc7ec1d9 |
299 | $c->log->debug('Something happened'); |
300 | $c->log->info('Something you should know'); |
301 | |
4a6895ce |
302 | =item * B<Stash> |
fc7ec1d9 |
303 | |
304 | $c->stash |
fc7ec1d9 |
305 | $c->stash->{foo} = 'bar'; |
d4ef4999 |
306 | $c->stash->{baz} = {baz => 'qox'}; |
7f71afbe |
307 | $c->stash->{fred} = [qw/wilma pebbles/]; |
d4ef4999 |
308 | |
309 | and so on. |
fc7ec1d9 |
310 | |
311 | =back |
312 | |
129cfe74 |
313 | The last of these, the stash, is a universal hash for sharing data among |
314 | application components. For an example, we return to our 'hello' action: |
fc7ec1d9 |
315 | |
e3dc9d78 |
316 | sub hello : Global { |
5a8ed4fe |
317 | my ( $self, $c ) = @_; |
318 | $c->stash->{message} = 'Hello World!'; |
4c6807d2 |
319 | $c->forward('show_message'); |
5a8ed4fe |
320 | } |
fc7ec1d9 |
321 | |
4c6807d2 |
322 | sub show_message : Private { |
5a8ed4fe |
323 | my ( $self, $c ) = @_; |
66f6e959 |
324 | $c->res->body( $c->stash->{message} ); |
5a8ed4fe |
325 | } |
fc7ec1d9 |
326 | |
e178a66a |
327 | Note that the stash should be used only for passing data in an |
328 | individual request cycle; it gets cleared at a new request. If you need |
3c4913b0 |
329 | to maintain persistent data, use a session. See |
330 | L<Catalyst::Plugin::Session> for a comprehensive set of |
331 | Catalyst-friendly session-handling tools. |
dd25a192 |
332 | |
fc7ec1d9 |
333 | =head3 Actions |
334 | |
56d8daeb |
335 | A Catalyst controller is defined by its actions. An action is a |
336 | subroutine with a special attribute. You've already seen some examples |
337 | of actions in this document. The URL (for example |
338 | http://localhost.3000/foo/bar) consists of two parts, the base |
339 | (http://localhost:3000/ in this example) and the path (foo/bar). Please |
340 | note that the trailing slash after the hostname[:port] always belongs to |
341 | base and not to the action. |
cda8d1ac |
342 | |
c37916b0 |
343 | =over 4 |
344 | |
345 | =item * B<Application Wide Actions> |
346 | |
347 | Actions which are called at the root level of the application |
6c5c02ba |
348 | (e.g. http://localhost:3000/ ) go in MyApp::Controller::Root, like |
c37916b0 |
349 | this: |
350 | |
351 | package MyApp::Controller::Root; |
352 | use base 'Catalyst::Controller'; |
353 | # Sets the actions in this controller to be registered with no prefix |
354 | # so they function identically to actions created in MyApp.pm |
355 | __PACKAGE__->config->{namespace} = ''; |
356 | sub default : Private { |
357 | my ( $self, $context ) = @_; |
358 | $context->response->body('Catalyst rocks!'); |
359 | } |
360 | 1; |
361 | |
c37916b0 |
362 | =back |
363 | |
c37916b0 |
364 | =head4 Action types |
365 | |
cda8d1ac |
366 | Catalyst supports several types of actions: |
fc7ec1d9 |
367 | |
368 | =over 4 |
369 | |
56d8daeb |
370 | =item * B<Literal> (B<Path> actions) |
fc7ec1d9 |
371 | |
e178a66a |
372 | package MyApp::Controller::My::Controller; |
f29c48dd |
373 | sub bar : Path('foo/bar') { } |
fc7ec1d9 |
374 | |
e178a66a |
375 | Literal C<Path> actions will act relative to their current |
376 | namespace. The above example matches only |
377 | http://localhost:3000/my/controller/foo/bar. If you start your path with |
378 | a forward slash, it will match from the root. Example: |
0cf56dbc |
379 | |
e178a66a |
380 | package MyApp::Controller::My::Controller; |
0cf56dbc |
381 | sub bar : Path('/foo/bar') { } |
382 | |
fc7ec1d9 |
383 | Matches only http://localhost:3000/foo/bar. |
384 | |
e178a66a |
385 | package MyApp::Controller::My::Controller; |
0cf56dbc |
386 | sub bar : Path { } |
387 | |
e178a66a |
388 | By leaving the C<Path> definition empty, it will match on the namespace |
389 | root. The above code matches http://localhost:3000/my/controller. |
0cf56dbc |
390 | |
4a6895ce |
391 | =item * B<Regex> |
fc7ec1d9 |
392 | |
b33ed88c |
393 | sub bar : Regex('^item(\d+)/order(\d+)$') { } |
fc7ec1d9 |
394 | |
129cfe74 |
395 | Matches any URL that matches the pattern in the action key, e.g. |
e178a66a |
396 | http://localhost:3000/item23/order42. The '' around the regexp is |
397 | optional, but perltidy likes it. :) |
b33ed88c |
398 | |
e178a66a |
399 | Regex matches act globally, i.e. without reference to the namespace from |
400 | which it is called, so that a C<bar> method in the |
401 | C<MyApp::Controller::Catalog::Order::Process> namespace won't match any |
402 | form of C<bar>, C<Catalog>, C<Order>, or C<Process> unless you |
403 | explicitly put this in the regex. To achieve the above, you should |
404 | consider using a C<LocalRegex> action. |
66f6e959 |
405 | |
406 | =item * B<LocalRegex> |
407 | |
408 | sub bar : LocalRegex('^widget(\d+)$') { } |
fc7ec1d9 |
409 | |
66f6e959 |
410 | LocalRegex actions act locally. If you were to use C<bar> in |
0cf56dbc |
411 | C<MyApp::Controller::Catalog>, the above example would match urls like |
412 | http://localhost:3000/catalog/widget23. |
413 | |
e178a66a |
414 | If you omit the "C<^>" from your regex, then it will match any depth |
415 | from the controller and not immediately off of the controller name. The |
416 | following example differs from the above code in that it will match |
0cf56dbc |
417 | http://localhost:3000/catalog/foo/widget23 as well. |
418 | |
419 | package MyApp::Controller::Catalog; |
420 | sub bar : LocalRegex('widget(\d+)$') { } |
66f6e959 |
421 | |
e178a66a |
422 | For both LocalRegex and Regex actions, if you use capturing parentheses |
423 | to extract values within the matching URL, those values are available in |
2982e768 |
424 | the C<$c-E<gt>req-E<gt>captures> array. In the above example, "widget23" |
e178a66a |
425 | would capture "23" in the above example, and |
2982e768 |
426 | C<$c-E<gt>req-E<gt>captures-E<gt>[0]> would be "23". If you want to pass |
e178a66a |
427 | arguments at the end of your URL, you must use regex action keys. See |
428 | L</URL Path Handling> below. |
fc7ec1d9 |
429 | |
56d8daeb |
430 | =item * B<Top-level> (B<Global>) |
cda8d1ac |
431 | |
c37916b0 |
432 | package MyApp::Controller::Foo; |
cda8d1ac |
433 | sub foo : Global { } |
434 | |
c37916b0 |
435 | Matches http://localhost:3000/foo. The function name is mapped |
436 | directly to the application base. You can provide an equivalent |
437 | function in this case by doing the following: |
438 | |
439 | package MyApp::Controller::Root |
440 | sub foo : Local { } |
cda8d1ac |
441 | |
56d8daeb |
442 | =item * B<Namespace-Prefixed> (B<Local>) |
fc7ec1d9 |
443 | |
e178a66a |
444 | package MyApp::Controller::My::Controller; |
e3dc9d78 |
445 | sub foo : Local { } |
fc7ec1d9 |
446 | |
cda8d1ac |
447 | Matches http://localhost:3000/my/controller/foo. |
fc7ec1d9 |
448 | |
129cfe74 |
449 | This action type indicates that the matching URL must be prefixed with a |
e178a66a |
450 | modified form of the component's class (package) name. This modified |
451 | class name excludes the parts that have a pre-defined meaning in |
452 | Catalyst ("MyApp::Controller" in the above example), replaces "::" with |
453 | "/", and converts the name to lower case. See L</Components> for a full |
454 | explanation of the pre-defined meaning of Catalyst component class |
455 | names. |
fc7ec1d9 |
456 | |
05a90578 |
457 | =item * B<Chained> |
458 | |
459 | Catalyst also provides a method to build and dispatch chains of actions, |
460 | like |
461 | |
7f71afbe |
462 | sub catalog : Chained : CaptureArgs(1) { |
05a90578 |
463 | my ( $self, $c, $arg ) = @_; |
464 | ... |
465 | } |
466 | |
7f71afbe |
467 | sub item : Chained('catalog') : Args(1) { |
05a90578 |
468 | my ( $self, $c, $arg ) = @_; |
469 | ... |
470 | } |
471 | |
7f71afbe |
472 | to handle a C</catalog/*/item/*> path. For extensive information about this |
3c4913b0 |
473 | dispatch type, please see L<Catalyst::DispatchType::Chained>. |
05a90578 |
474 | |
4a6895ce |
475 | =item * B<Private> |
fc7ec1d9 |
476 | |
5a8ed4fe |
477 | sub foo : Private { } |
fc7ec1d9 |
478 | |
e178a66a |
479 | Matches no URL, and cannot be executed by requesting a URL that |
480 | corresponds to the action key. Private actions can be executed only |
481 | inside a Catalyst application, by calling the C<forward> method: |
fc7ec1d9 |
482 | |
5a8ed4fe |
483 | $c->forward('foo'); |
fc7ec1d9 |
484 | |
129cfe74 |
485 | See L</Flow Control> for a full explanation of C<forward>. Note that, as |
fc9c8698 |
486 | discussed there, when forwarding from another component, you must use |
487 | the absolute path to the method, so that a private C<bar> method in your |
488 | C<MyApp::Controller::Catalog::Order::Process> controller must, if called |
489 | from elsewhere, be reached with |
490 | C<$c-E<gt>forward('/catalog/order/process/bar')>. |
fc7ec1d9 |
491 | |
baf5120b |
492 | =item * B<Args> |
493 | |
7f71afbe |
494 | Args is not an action type per se, but an action modifier - it adds a |
495 | match restriction to any action it's provided to, requiring only as many |
496 | path parts as are specified for the action to be valid - for example in |
baf5120b |
497 | MyApp::Controller::Foo, |
498 | |
499 | sub bar :Local |
500 | |
501 | would match any URL starting /foo/bar/. To restrict this you can do |
502 | |
503 | sub bar :Local :Args(1) |
504 | |
505 | to only match /foo/bar/*/ |
506 | |
fc7ec1d9 |
507 | =back |
508 | |
b33ed88c |
509 | B<Note:> After seeing these examples, you probably wonder what the point |
56d8daeb |
510 | is of defining names for regex and path actions. Every public action is |
511 | also a private one, so you have one unified way of addressing components |
512 | in your C<forward>s. |
cda8d1ac |
513 | |
72d9bfc7 |
514 | =head4 Built-in Private Actions |
fc7ec1d9 |
515 | |
fc9c8698 |
516 | In response to specific application states, Catalyst will automatically |
517 | call these built-in private actions in your application class: |
fc7ec1d9 |
518 | |
519 | =over 4 |
520 | |
cda8d1ac |
521 | =item * B<default : Private> |
fc7ec1d9 |
522 | |
fc9c8698 |
523 | Called when no other action matches. Could be used, for example, for |
524 | displaying a generic frontpage for the main app, or an error page for |
525 | individual controllers. |
fc7ec1d9 |
526 | |
0cf56dbc |
527 | If C<default> isn't acting how you would expect, look at using a |
3c4913b0 |
528 | L</Literal> C<Path> action (with an empty path string). The difference |
529 | is that C<Path> takes arguments relative from the namespace and |
530 | C<default> I<always> takes arguments relative from the root, regardless |
531 | of what controller it's in. Indeed, this is now the recommended way of |
532 | handling default situations; the C<default> private controller should |
533 | be considered deprecated. |
0cf56dbc |
534 | |
66f6e959 |
535 | =item * B<index : Private> |
536 | |
537 | C<index> is much like C<default> except that it takes no arguments |
e178a66a |
538 | and it is weighted slightly higher in the matching process. It is |
539 | useful as a static entry point to a controller, e.g. to have a static |
61a9002d |
540 | welcome page. Note that it's also weighted higher than Path. |
66f6e959 |
541 | |
cda8d1ac |
542 | =item * B<begin : Private> |
fc7ec1d9 |
543 | |
fc9c8698 |
544 | Called at the beginning of a request, before any matching actions are |
545 | called. |
fc7ec1d9 |
546 | |
cda8d1ac |
547 | =item * B<end : Private> |
4a6895ce |
548 | |
fc7ec1d9 |
549 | Called at the end of a request, after all matching actions are called. |
550 | |
fc9c8698 |
551 | =back |
552 | |
6b10c72b |
553 | =head4 Built-in actions in controllers/autochaining |
fc7ec1d9 |
554 | |
e178a66a |
555 | Package MyApp::Controller::Foo; |
cda8d1ac |
556 | sub begin : Private { } |
5a8ed4fe |
557 | sub default : Private { } |
eff5f524 |
558 | sub auto : Private { } |
fc7ec1d9 |
559 | |
fc9c8698 |
560 | You can define built-in private actions within your controllers as |
561 | well. The actions will override the ones in less-specific controllers, |
562 | or your application class. In other words, for each of the three |
563 | built-in private actions, only one will be run in any request |
e178a66a |
564 | cycle. Thus, if C<MyApp::Controller::Catalog::begin> exists, it will be |
565 | run in place of C<MyApp::begin> if you're in the C<catalog> namespace, |
566 | and C<MyApp::Controller::Catalog::Order::begin> would override this in |
567 | turn. |
fc9c8698 |
568 | |
7f71afbe |
569 | =item * B<auto : Private> |
570 | |
eff5f524 |
571 | In addition to the normal built-in actions, you have a special action |
572 | for making chains, C<auto>. Such C<auto> actions will be run after any |
fc9c8698 |
573 | C<begin>, but before your action is processed. Unlike the other |
eff5f524 |
574 | built-ins, C<auto> actions I<do not> override each other; they will be |
575 | called in turn, starting with the application class and going through to |
576 | the I<most> specific class. I<This is the reverse of the order in which |
577 | the normal built-ins override each other>. |
fc9c8698 |
578 | |
579 | Here are some examples of the order in which the various built-ins |
580 | would be called: |
cda8d1ac |
581 | |
582 | =over 4 |
583 | |
fc9c8698 |
584 | =item for a request for C</foo/foo> |
cda8d1ac |
585 | |
586 | MyApp::begin |
80ef2e6d |
587 | MyApp::auto |
e178a66a |
588 | MyApp::Controller::Foo::default # in the absence of MyApp::Controller::Foo::Foo |
cda8d1ac |
589 | MyApp::end |
590 | |
fc9c8698 |
591 | =item for a request for C</foo/bar/foo> |
cda8d1ac |
592 | |
e178a66a |
593 | MyApp::Controller::Foo::Bar::begin |
80ef2e6d |
594 | MyApp::auto |
e178a66a |
595 | MyApp::Controller::Foo::auto |
596 | MyApp::Controller::Foo::Bar::auto |
597 | MyApp::Controller::Foo::Bar::default # for MyApp::Controller::Foo::Bar::foo |
598 | MyApp::Controller::Foo::Bar::end |
80ef2e6d |
599 | |
600 | =back |
601 | |
fc9c8698 |
602 | The C<auto> action is also distinguished by the fact that you can break |
603 | out of the processing chain by returning 0. If an C<auto> action returns |
604 | 0, any remaining actions will be skipped, except for C<end>. So, for the |
605 | request above, if the first auto returns false, the chain would look |
606 | like this: |
80ef2e6d |
607 | |
608 | =over 4 |
609 | |
fc9c8698 |
610 | =item for a request for C</foo/bar/foo> where first C<auto> returns |
611 | false |
80ef2e6d |
612 | |
e178a66a |
613 | MyApp::Controller::Foo::Bar::begin |
80ef2e6d |
614 | MyApp::auto |
e178a66a |
615 | MyApp::Controller::Foo::Bar::end |
cda8d1ac |
616 | |
617 | =back |
4a6895ce |
618 | |
fc9c8698 |
619 | An example of why one might use this is an authentication action: you |
620 | could set up a C<auto> action to handle authentication in your |
621 | application class (which will always be called first), and if |
622 | authentication fails, returning 0 would skip any remaining methods |
623 | for that URL. |
03805733 |
624 | |
fc9c8698 |
625 | B<Note:> Looking at it another way, C<auto> actions have to return a |
7f71afbe |
626 | true value to continue processing! You can also C<die> in the auto |
fc9c8698 |
627 | action; in that case, the request will go straight to the finalize |
628 | stage, without processing further actions. |
03805733 |
629 | |
6b10c72b |
630 | =head4 URL Path Handling |
4a6895ce |
631 | |
70d5ae49 |
632 | You can pass variable arguments as part of the URL path, separated with |
633 | forward slashes (/). If the action is a Regex or LocalRegex, the '$' anchor |
634 | must be used. For example, suppose you want to handle C</foo/$bar/$baz>, |
635 | where C<$bar> and C<$baz> may vary: |
4a6895ce |
636 | |
cda8d1ac |
637 | sub foo : Regex('^foo$') { my ($self, $context, $bar, $baz) = @_; } |
4a6895ce |
638 | |
fc9c8698 |
639 | But what if you also defined actions for C</foo/boo> and C</foo/boo/hoo>? |
4a6895ce |
640 | |
f29c48dd |
641 | sub boo : Path('foo/boo') { .. } |
642 | sub hoo : Path('foo/boo/hoo') { .. } |
4a6895ce |
643 | |
644 | Catalyst matches actions in most specific to least specific order: |
645 | |
646 | /foo/boo/hoo |
647 | /foo/boo |
fc9c8698 |
648 | /foo # might be /foo/bar/baz but won't be /foo/boo/hoo |
4a6895ce |
649 | |
fc9c8698 |
650 | So Catalyst would never mistakenly dispatch the first two URLs to the |
651 | '^foo$' action. |
fc7ec1d9 |
652 | |
70d5ae49 |
653 | If a Regex or LocalRegex action doesn't use the '$' anchor, the action will |
654 | still match a URL containing arguments, however the arguments won't be |
655 | available via C<@_>. |
656 | |
6b10c72b |
657 | =head4 Parameter Processing |
2ef2fb0f |
658 | |
fc9c8698 |
659 | Parameters passed in the URL query string are handled with methods in |
660 | the L<Catalyst::Request> class. The C<param> method is functionally |
661 | equivalent to the C<param> method of C<CGI.pm> and can be used in |
662 | modules that require this. |
2ef2fb0f |
663 | |
664 | # http://localhost:3000/catalog/view/?category=hardware&page=3 |
665 | my $category = $c->req->param('category'); |
666 | my $current_page = $c->req->param('page') || 1; |
667 | |
668 | # multiple values for single parameter name |
669 | my @values = $c->req->param('scrolling_list'); |
670 | |
671 | # DFV requires a CGI.pm-like input hash |
672 | my $results = Data::FormValidator->check($c->req->params, \%dfv_profile); |
673 | |
fc7ec1d9 |
674 | =head3 Flow Control |
675 | |
d08ced28 |
676 | You control the application flow with the C<forward> method, which |
677 | accepts the key of an action to execute. This can be an action in the |
678 | same or another Catalyst controller, or a Class name, optionally |
679 | followed by a method name. After a C<forward>, the control flow will |
680 | return to the method from which the C<forward> was issued. |
681 | |
682 | A C<forward> is similar to a method call. The main differences are that |
683 | it wraps the call in an C<eval> to allow exception handling; it |
684 | automatically passes along the context object (C<$c> or C<$context>); |
685 | and it allows profiling of each call (displayed in the log with |
686 | debugging enabled). |
fc7ec1d9 |
687 | |
e3dc9d78 |
688 | sub hello : Global { |
5a8ed4fe |
689 | my ( $self, $c ) = @_; |
690 | $c->stash->{message} = 'Hello World!'; |
d08ced28 |
691 | $c->forward('check_message'); # $c is automatically included |
5a8ed4fe |
692 | } |
fc7ec1d9 |
693 | |
4c6807d2 |
694 | sub check_message : Private { |
5a8ed4fe |
695 | my ( $self, $c ) = @_; |
696 | return unless $c->stash->{message}; |
4c6807d2 |
697 | $c->forward('show_message'); |
5a8ed4fe |
698 | } |
fc7ec1d9 |
699 | |
4c6807d2 |
700 | sub show_message : Private { |
5a8ed4fe |
701 | my ( $self, $c ) = @_; |
66f6e959 |
702 | $c->res->body( $c->stash->{message} ); |
5a8ed4fe |
703 | } |
3323f920 |
704 | |
6c5c02ba |
705 | A C<forward> does not create a new request, so your request object |
706 | (C<$c-E<gt>req>) will remain unchanged. This is a key difference between |
707 | using C<forward> and issuing a redirect. |
3323f920 |
708 | |
d08ced28 |
709 | You can pass new arguments to a C<forward> by adding them |
710 | in an anonymous array. In this case C<$c-E<gt>req-E<gt>args> |
711 | will be changed for the duration of the C<forward> only; upon |
712 | return, the original value of C<$c-E<gt>req-E<gt>args> will |
713 | be reset. |
3323f920 |
714 | |
715 | sub hello : Global { |
716 | my ( $self, $c ) = @_; |
717 | $c->stash->{message} = 'Hello World!'; |
d08ced28 |
718 | $c->forward('check_message',[qw/test1/]); |
719 | # now $c->req->args is back to what it was before |
3323f920 |
720 | } |
721 | |
d08ced28 |
722 | sub check_message : Private { |
723 | my ( $self, $c ) = @_; |
fabf3a10 |
724 | my $first_argument = $c->req->args->[0]; # now = 'test1' |
d08ced28 |
725 | # do something... |
726 | } |
b248fa4a |
727 | |
d08ced28 |
728 | As you can see from these examples, you can just use the method name as |
729 | long as you are referring to methods in the same controller. If you want |
730 | to forward to a method in another controller, or the main application, |
731 | you will have to refer to the method by absolute path. |
cda8d1ac |
732 | |
733 | $c->forward('/my/controller/action'); |
d08ced28 |
734 | $c->forward('/default'); # calls default in main application |
fc7ec1d9 |
735 | |
d08ced28 |
736 | Here are some examples of how to forward to classes and methods. |
fc7ec1d9 |
737 | |
e3dc9d78 |
738 | sub hello : Global { |
5a8ed4fe |
739 | my ( $self, $c ) = @_; |
e178a66a |
740 | $c->forward(qw/MyApp::Model::Hello say_hello/); |
5a8ed4fe |
741 | } |
fc7ec1d9 |
742 | |
e3dc9d78 |
743 | sub bye : Global { |
5a8ed4fe |
744 | my ( $self, $c ) = @_; |
e178a66a |
745 | $c->forward('MyApp::Model::Hello'); # no method: will try 'process' |
5a8ed4fe |
746 | } |
fc7ec1d9 |
747 | |
e178a66a |
748 | package MyApp::Model::Hello; |
fc7ec1d9 |
749 | |
750 | sub say_hello { |
751 | my ( $self, $c ) = @_; |
66f6e959 |
752 | $c->res->body('Hello World!'); |
fc7ec1d9 |
753 | } |
754 | |
755 | sub process { |
756 | my ( $self, $c ) = @_; |
66f6e959 |
757 | $c->res->body('Goodbye World!'); |
fc7ec1d9 |
758 | } |
759 | |
d08ced28 |
760 | Note that C<forward> returns to the calling action and continues |
13436c14 |
761 | processing after the action finishes. If you want all further processing |
762 | in the calling action to stop, use C<detach> instead, which will execute |
763 | the C<detach>ed action and not return to the calling sub. In both cases, |
764 | Catalyst will automatically try to call process() if you omit the |
765 | method. |
fc7ec1d9 |
766 | |
767 | =head3 Components |
768 | |
56d8daeb |
769 | Catalyst has an uncommonly flexible component system. You can define as |
cccc887d |
770 | many L</Models>, L</Views>, and L</Controllers> as you like. |
fc7ec1d9 |
771 | |
56d8daeb |
772 | All components must inherit from L<Catalyst::Base>, which provides a |
773 | simple class structure and some common class methods like C<config> and |
774 | C<new> (constructor). |
fc7ec1d9 |
775 | |
e178a66a |
776 | package MyApp::Controller::Catalog; |
fc7ec1d9 |
777 | |
778 | use strict; |
779 | use base 'Catalyst::Base'; |
780 | |
781 | __PACKAGE__->config( foo => 'bar' ); |
782 | |
783 | 1; |
784 | |
6b10c72b |
785 | You don't have to C<use> or otherwise register Models, Views, and |
786 | Controllers. Catalyst automatically discovers and instantiates them |
787 | when you call C<setup> in the main application. All you need to do is |
788 | put them in directories named for each Component type. Notice that you |
6c5c02ba |
789 | can use a terse alias for each one. |
fc7ec1d9 |
790 | |
791 | =over 4 |
792 | |
4a6895ce |
793 | =item * B<MyApp/Model/> |
fc7ec1d9 |
794 | |
4a6895ce |
795 | =item * B<MyApp/M/> |
fc7ec1d9 |
796 | |
4a6895ce |
797 | =item * B<MyApp/View/> |
fc7ec1d9 |
798 | |
4a6895ce |
799 | =item * B<MyApp/V/> |
fc7ec1d9 |
800 | |
4a6895ce |
801 | =item * B<MyApp/Controller/> |
fc7ec1d9 |
802 | |
4a6895ce |
803 | =item * B<MyApp/C/> |
fc7ec1d9 |
804 | |
805 | =back |
806 | |
6c5c02ba |
807 | In older versions of Catalyst, the recommended practice (and the one |
808 | automatically created by helper scripts) was to name the directories |
809 | C<M/>, C<V/>, and C<C/>. Though these still work, we now recommend |
810 | the use of the full names. |
811 | |
fc7ec1d9 |
812 | =head4 Views |
813 | |
129cfe74 |
814 | To show how to define views, we'll use an already-existing base class for the |
815 | L<Template Toolkit|Template>, L<Catalyst::View::TT>. All we need to do is |
816 | inherit from this class: |
fc7ec1d9 |
817 | |
e178a66a |
818 | package MyApp::View::TT; |
fc7ec1d9 |
819 | |
820 | use strict; |
821 | use base 'Catalyst::View::TT'; |
822 | |
823 | 1; |
824 | |
b33ed88c |
825 | (You can also generate this automatically by using the helper script: |
826 | |
827 | script/myapp_create.pl view TT TT |
828 | |
fb9257c1 |
829 | where the first C<TT> tells the script that the name of the view should |
830 | be C<TT>, and the second that it should be a Template Toolkit view.) |
b33ed88c |
831 | |
129cfe74 |
832 | This gives us a process() method and we can now just do |
e178a66a |
833 | $c->forward('MyApp::View::TT') to render our templates. The base class |
834 | makes process() implicit, so we don't have to say |
835 | C<$c-E<gt>forward(qw/MyApp::View::TT process/)>. |
fc7ec1d9 |
836 | |
e3dc9d78 |
837 | sub hello : Global { |
5a8ed4fe |
838 | my ( $self, $c ) = @_; |
839 | $c->stash->{template} = 'hello.tt'; |
840 | } |
fc7ec1d9 |
841 | |
5a8ed4fe |
842 | sub end : Private { |
843 | my ( $self, $c ) = @_; |
e178a66a |
844 | $c->forward('MyApp::View::TT'); |
5a8ed4fe |
845 | } |
fc7ec1d9 |
846 | |
6b10c72b |
847 | You normally render templates at the end of a request, so it's a perfect |
7f71afbe |
848 | use for the global C<end> action. |
849 | |
850 | In practice, however, you would use a default C<end> action as supplied |
851 | by L<Catalyst::Action::RenderView>. |
fc7ec1d9 |
852 | |
129cfe74 |
853 | Also, be sure to put the template under the directory specified in |
3c4913b0 |
854 | C<$c-E<gt>config-E<gt>{root}>, or you'll end up looking at the debug |
855 | screen. |
fc7ec1d9 |
856 | |
857 | =head4 Models |
858 | |
e178a66a |
859 | To show how to define models, again we'll use an already-existing base |
e112461a |
860 | class, this time for L<DBIx::Class>: L<Catalyst::Model::DBIC::Schema>. |
861 | We'll also need L<DBIx::Class::Schema::Loader>. |
fc7ec1d9 |
862 | |
863 | But first, we need a database. |
864 | |
865 | -- myapp.sql |
866 | CREATE TABLE foo ( |
867 | id INTEGER PRIMARY KEY, |
868 | data TEXT |
869 | ); |
870 | |
871 | CREATE TABLE bar ( |
872 | id INTEGER PRIMARY KEY, |
873 | foo INTEGER REFERENCES foo, |
874 | data TEXT |
875 | ); |
876 | |
877 | INSERT INTO foo (data) VALUES ('TEST!'); |
878 | |
879 | |
880 | % sqlite /tmp/myapp.db < myapp.sql |
881 | |
e112461a |
882 | Now we can create a DBIC::SchemaLoader component for this database. |
fc7ec1d9 |
883 | |
e112461a |
884 | script/myapp_create.pl model DBIC DBIC::SchemaLoader 'dbi:SQLite:/tmp/myapp.db' |
fc7ec1d9 |
885 | |
e112461a |
886 | L<DBIx::Class::Schema::Loader> automatically loads table layouts and |
887 | relationships. Use the stash to pass data to your templates. |
fc7ec1d9 |
888 | |
e112461a |
889 | We add the following to MyApp/Controller/Root.pm |
b248fa4a |
890 | |
e112461a |
891 | sub view : Global { |
892 | my ( $self, $c, $id ) = @_; |
893 | |
894 | $c->stash->{item} = $c->model('DBIC::Foo')->find($id); |
895 | } |
fc7ec1d9 |
896 | |
e112461a |
897 | 1; |
898 | |
5a8ed4fe |
899 | sub end : Private { |
900 | my ( $self, $c ) = @_; |
e112461a |
901 | |
5a8ed4fe |
902 | $c->stash->{template} ||= 'index.tt'; |
e112461a |
903 | $c->forward( $c->view('TT') ); |
5a8ed4fe |
904 | } |
fc7ec1d9 |
905 | |
e112461a |
906 | We then create a new template file "root/index.tt" containing: |
fc7ec1d9 |
907 | |
e112461a |
908 | The Id's data is [% item.data %] |
fc7ec1d9 |
909 | |
6b10c72b |
910 | Models do not have to be part of your Catalyst application; you |
911 | can always call an outside module that serves as your Model: |
912 | |
913 | # in a Controller |
914 | sub list : Local { |
915 | my ( $self, $c ) = @_; |
e112461a |
916 | |
6b10c72b |
917 | $c->stash->{template} = 'list.tt'; |
e112461a |
918 | |
3c4913b0 |
919 | use Some::Outside::Database::Module; |
920 | my @records = Some::Outside::Database::Module->search({ |
921 | artist => 'Led Zeppelin', |
e112461a |
922 | }); |
923 | |
6b10c72b |
924 | $c->stash->{records} = \@records; |
925 | } |
926 | |
927 | But by using a Model that is part of your Catalyst application, you gain |
928 | several things: you don't have to C<use> each component, Catalyst will |
929 | find and load it automatically at compile-time; you can C<forward> to |
26e73131 |
930 | the module, which can only be done to Catalyst components; and only |
6b10c72b |
931 | Catalyst components can be fetched with |
e178a66a |
932 | C<$c-E<gt>model('SomeModel')>. |
6b10c72b |
933 | |
934 | Happily, since many people have existing Model classes that they |
935 | would like to use with Catalyst (or, conversely, they want to |
936 | write Catalyst models that can be used outside of Catalyst, e.g. |
937 | in a cron job), it's trivial to write a simple component in |
938 | Catalyst that slurps in an outside Model: |
939 | |
e112461a |
940 | package MyApp::Model::DB; |
941 | use base qw/Catalyst::Model::DBIC::Schema/; |
942 | __PACKAGE__->config( |
943 | schema_class => 'Some::DBIC::Schema', |
cccc887d |
944 | connect_info => ['dbi:SQLite:foo.db', '', '', {AutoCommit=>1}] |
e112461a |
945 | ); |
6b10c72b |
946 | 1; |
947 | |
e112461a |
948 | and that's it! Now C<Some::DBIC::Schema> is part of your |
949 | Cat app as C<MyApp::Model::DB>. |
6b10c72b |
950 | |
fc7ec1d9 |
951 | =head4 Controllers |
952 | |
129cfe74 |
953 | Multiple controllers are a good way to separate logical domains of your |
954 | application. |
fc7ec1d9 |
955 | |
e178a66a |
956 | package MyApp::Controller::Login; |
fc7ec1d9 |
957 | |
c02f7490 |
958 | use base qw/Catalyst::Controller/; |
959 | |
960 | sub sign_in : Path("sign-in") { } |
961 | sub new_password : Path("new-password") { } |
962 | sub sign_out : Path("sign-out") { } |
fc7ec1d9 |
963 | |
e178a66a |
964 | package MyApp::Controller::Catalog; |
fc7ec1d9 |
965 | |
c02f7490 |
966 | use base qw/Catalyst::Controller/; |
967 | |
e3dc9d78 |
968 | sub view : Local { } |
969 | sub list : Local { } |
fc7ec1d9 |
970 | |
e178a66a |
971 | package MyApp::Controller::Cart; |
fc7ec1d9 |
972 | |
c02f7490 |
973 | use base qw/Catalyst::Controller/; |
974 | |
e3dc9d78 |
975 | sub add : Local { } |
976 | sub update : Local { } |
977 | sub order : Local { } |
fc7ec1d9 |
978 | |
c02f7490 |
979 | Note that you can also supply attributes via the Controller's config so long |
980 | as you have at least one attribute on a subref to be exported (:Action is |
981 | commonly used for this) - for example the following is equivalent to the same |
982 | controller above |
983 | |
984 | package MyApp::Controller::Login; |
985 | |
986 | use base qw/Catalyst::Controller/; |
987 | |
988 | __PACKAGE__->config( |
989 | actions => { |
990 | 'sign_in' => { Path => 'sign-in' }, |
991 | 'new_password' => { Path => 'new-password' }, |
992 | 'sign_out' => { Path => 'sign-out' }, |
993 | }, |
994 | ); |
995 | |
996 | sub sign_in : Action { } |
997 | sub new_password : Action { } |
998 | sub sign_out : Action { } |
999 | |
24cda51b |
1000 | =head3 Models |
1001 | |
7f71afbe |
1002 | Models are providers of data. This data could come from anywhere - a |
1003 | search engine index, a database table, etc. Typically the data source |
1004 | does not have much to do with web applications or Catalyst - it could be |
1005 | used to write an offline report generator or a command line tool just |
1006 | the same. |
24cda51b |
1007 | |
7f71afbe |
1008 | The common approach to writing a Catalyst-style model for your |
1009 | application is wrapping a generic model (e.g. L<DBIx::Class::Schema>, a |
1010 | bunch of XMLs, or anything really) with an object that contains |
1011 | configuration data, convenience methods, and so forth. |
24cda51b |
1012 | |
1013 | #### editor: move this part to =head3 Components somehow, right after this |
1014 | #### section - this will require deeply rephrasing this paragraph. |
1015 | |
7f71afbe |
1016 | Technically, within Catalyst a model is a B<component> - an instance of |
1017 | the model's class belonging to the application. It is important to |
1018 | stress that the lifetime of these objects is per application, not per |
1019 | request. |
24cda51b |
1020 | |
7f71afbe |
1021 | While the model base class (L<Catalyst::Model>) provides things like |
1022 | C<config> and stuff to better integrate the model into the application, |
1023 | sometimes this is not enough, and the model requires access to C<$c> |
1024 | itself. |
24cda51b |
1025 | |
1026 | Situations where this need might arise include: |
1027 | |
1028 | =over 4 |
1029 | |
1030 | =item * |
1031 | |
1032 | Interacting with another model |
1033 | |
1034 | =item * |
1035 | |
1036 | Using per-request data to control behavior |
1037 | |
1038 | =item * |
1039 | |
1040 | Using plugins in (for example L<Catalyst::Plugin::Cache>). |
1041 | |
1042 | =back |
1043 | |
6c5c02ba |
1044 | From a style perspective usually it's bad to make your model "too smart" |
1045 | about things - it should worry about business logic and leave the |
1046 | integration details to the controllers. If, however, you find that it |
1047 | does not make sense at all to use an auxillary controller around the |
1048 | model, and the model's need to access C<$c> cannot be sidestepped, there |
1049 | exists a power tool called C<ACCEPT_CONTEXT>. |
24cda51b |
1050 | |
1051 | #### editor note: this part is "generic" - it also applies to views and |
1052 | #### controllers. |
1053 | |
1054 | =head3 ACCEPT_CONTEXT |
1055 | |
6c5c02ba |
1056 | Whenever you call $c->component("Foo") you get back an object - the |
1057 | instance of the model. If the component supports the C<ACCEPT_CONTEXT> |
1058 | method instead of returning the model itself, the return value of C<< |
1059 | $model->ACCEPT_CONTEXT( $c ) >> will be used. |
24cda51b |
1060 | |
1061 | This means that whenever your model/view/controller needs to talk to C<$c> it |
1062 | gets a chance to do this when it's needed. |
1063 | |
1064 | A typical C<ACCEPT_CONTEXT> method will either clone the model and return one |
1065 | with the context object set, or it will return a thin wrapper that contains |
1066 | C<$c> and delegates to the per-application model object. |
1067 | |
6c5c02ba |
1068 | A typical C<ACCEPT_CONTEXT> method could look like this: |
24cda51b |
1069 | |
7f71afbe |
1070 | sub ACCEPT_CONTEXT { |
1071 | my ( $self, $c, @extra_arguments ) = @_; |
1072 | bless { %$self, c => $c }, ref($self); |
1073 | } |
24cda51b |
1074 | |
1075 | effectively treating $self as a B<prototype object> that gets a new parameter. |
1076 | C<@extra_arguments> comes from any trailing arguments to |
1077 | C<< $c->component( $bah, @extra_arguments ) >> (or C<< $c->model(...) >>, |
1078 | C<< $c->view(...) >> etc). |
1079 | |
1080 | The life time of this value is B<per usage>, and not per request. To make this |
1081 | per request you can use the following technique: |
1082 | |
1083 | Add a field to C<$c>, like C<my_model_instance>. Then write your |
1084 | C<ACCEPT_CONTEXT> method to look like this: |
1085 | |
5403ad42 |
1086 | sub ACCEPT_CONTEXT { |
1087 | my ( $self, $c ) = @_; |
1088 | |
1089 | if ( my $per_request = $c->my_model_instance ) { |
1090 | return $per_request; |
1091 | } else { |
1092 | my $new_instance = bless { %$self, c => $c }, ref($self); |
1093 | Scalar::Util::weaken($new_instance->{c}); # or we have a circular reference |
1094 | $c->my_model_instance( $new_instance ); |
1095 | return $new_instance; |
1096 | } |
1097 | } |
24cda51b |
1098 | |
1099 | |
fc7ec1d9 |
1100 | =head3 Testing |
1101 | |
6c5c02ba |
1102 | Catalyst has a built-in http server for testing. (Later, you can easily |
1103 | use a more powerful server, e.g. Apache/mod_perl or FastCGI, in a |
1104 | production environment.) |
fc7ec1d9 |
1105 | |
1106 | Start your application on the command line... |
1107 | |
b33ed88c |
1108 | script/myapp_server.pl |
fc7ec1d9 |
1109 | |
1110 | ...then visit http://localhost:3000/ in a browser to view the output. |
1111 | |
1112 | You can also do it all from the command line: |
1113 | |
b33ed88c |
1114 | script/myapp_test.pl http://localhost/ |
fc7ec1d9 |
1115 | |
1116 | Have fun! |
1117 | |
3cb1db8c |
1118 | =head1 SUPPORT |
1119 | |
1120 | IRC: |
1121 | |
1122 | Join #catalyst on irc.perl.org. |
1123 | |
72d9bfc7 |
1124 | Mailing-lists: |
3cb1db8c |
1125 | |
1126 | http://lists.rawmode.org/mailman/listinfo/catalyst |
1127 | http://lists.rawmode.org/mailman/listinfo/catalyst-dev |
1128 | |
fc7ec1d9 |
1129 | =head1 AUTHOR |
1130 | |
cda8d1ac |
1131 | Sebastian Riedel, C<sri@oook.de> |
1132 | David Naughton, C<naughton@umn.edu> |
1133 | Marcus Ramberg, C<mramberg@cpan.org> |
f531dd37 |
1134 | Jesse Sheidlower, C<jester@panix.com> |
129cfe74 |
1135 | Danijel Milicevic, C<me@danijel.de> |
c37916b0 |
1136 | Kieren Diment, C<kd@totaldatasolution.com> |
24cda51b |
1137 | Yuval Kogman, C<nothingmuch@woobling.org> |
fc7ec1d9 |
1138 | |
1139 | =head1 COPYRIGHT |
1140 | |
aa2b0d97 |
1141 | This program is free software, you can redistribute it and/or modify it |
1142 | under the same terms as Perl itself. |