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