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