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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> |
fc7ec1d9 |
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. |
fc7ec1d9 |
74 | |
cda8d1ac |
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 | |
4a6895ce |
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 ) = @_; |
66f6e959 |
92 | $context->response->body('Hello World!'); |
5a8ed4fe |
93 | } |
fc7ec1d9 |
94 | |
95 | Now http://localhost:3000/hello prints "Hello World!". |
96 | |
4a6895ce |
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> |
fc7ec1d9 |
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/ |
fc7ec1d9 |
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 |
187 | configure your application, load plugins, define application-wide |
188 | actions, and extend Catalyst. |
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189 | |
190 | package MyApp; |
191 | |
192 | use strict; |
193 | use Catalyst qw/-Debug/; |
194 | |
195 | MyApp->config( |
196 | name => 'My Application', |
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197 | |
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198 | # You can put anything else you want in here: |
199 | my_configuration_variable => 'something', |
fc7ec1d9 |
200 | ); |
201 | |
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202 | sub default : Private { |
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203 | my ( $self, $context ) = @_; |
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204 | $context->response->body('Catalyst rocks!'); |
5a8ed4fe |
205 | } |
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206 | |
207 | 1; |
208 | |
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209 | For most applications, Catalyst requires you to define only one config |
210 | parameter: |
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211 | |
212 | =over 4 |
213 | |
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214 | =item * B<name> |
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215 | |
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216 | The name of your application. |
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217 | |
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218 | =back |
219 | |
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220 | Optionally, you can specify a B<root> parameter for templates and static |
221 | data. If omitted, Catalyst will try to auto-detect the directory's |
222 | location. You can define as many parameters as you want for plugins or |
223 | whatever you need. You can access them anywhere in your application via |
224 | C<$context-E<gt>config-E<gt>{$param_name}>. |
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225 | |
226 | =head3 Context |
227 | |
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228 | Catalyst automatically blesses a Context object into your application |
229 | class and makes it available everywhere in your application. Use the |
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230 | Context to directly interact with Catalyst and glue your L</Components> |
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231 | together. For example, if you need to use the Context from within a |
232 | Template Toolkit template, it's already there: |
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233 | |
234 | <h1>Welcome to [% c.config.name %]!</h1> |
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235 | |
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236 | As illustrated in our URL-to-Action dispatching example, the Context is |
237 | always the second method parameter, behind the Component object |
238 | reference or class name itself. Previously we called it C<$context> for |
239 | clarity, but most Catalyst developers just call it C<$c>: |
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240 | |
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241 | sub hello : Global { |
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242 | my ( $self, $c ) = @_; |
66f6e959 |
243 | $c->res->body('Hello World!'); |
5a8ed4fe |
244 | } |
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245 | |
246 | The Context contains several important objects: |
247 | |
248 | =over 4 |
249 | |
250 | =item * L<Catalyst::Request> |
251 | |
252 | $c->request |
253 | $c->req # alias |
254 | |
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255 | The request object contains all kinds of request-specific information, like |
256 | query parameters, cookies, uploads, headers, and more. |
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257 | |
258 | $c->req->params->{foo}; |
259 | $c->req->cookies->{sessionid}; |
260 | $c->req->headers->content_type; |
261 | $c->req->base; |
262 | |
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263 | =item * L<Catalyst::Response> |
fc7ec1d9 |
264 | |
265 | $c->response |
266 | $c->res # alias |
267 | |
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268 | The response is like the request, but contains just response-specific |
269 | information. |
fc7ec1d9 |
270 | |
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271 | $c->res->body('Hello World'); |
fc7ec1d9 |
272 | $c->res->status(404); |
273 | $c->res->redirect('http://oook.de'); |
274 | |
275 | =item * L<Catalyst::Config> |
276 | |
277 | $c->config |
fc7ec1d9 |
278 | $c->config->root; |
279 | $c->config->name; |
280 | |
281 | =item * L<Catalyst::Log> |
282 | |
283 | $c->log |
fc7ec1d9 |
284 | $c->log->debug('Something happened'); |
285 | $c->log->info('Something you should know'); |
286 | |
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287 | =item * B<Stash> |
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288 | |
289 | $c->stash |
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290 | $c->stash->{foo} = 'bar'; |
291 | |
292 | =back |
293 | |
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294 | The last of these, the stash, is a universal hash for sharing data among |
295 | application components. For an example, we return to our 'hello' action: |
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296 | |
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297 | sub hello : Global { |
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298 | my ( $self, $c ) = @_; |
299 | $c->stash->{message} = 'Hello World!'; |
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300 | $c->forward('show_message'); |
5a8ed4fe |
301 | } |
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302 | |
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303 | sub show_message : Private { |
5a8ed4fe |
304 | my ( $self, $c ) = @_; |
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305 | $c->res->body( $c->stash->{message} ); |
5a8ed4fe |
306 | } |
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307 | |
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308 | Note that the stash should be used only for passing data in an |
309 | individual request cycle; it gets cleared at a new request. If you need |
310 | to maintain more persistent data, use a session. |
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311 | |
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312 | =head3 Actions |
313 | |
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314 | A Catalyst controller is defined by its actions. An action is a |
315 | subroutine with a special attribute. You've already seen some examples |
316 | of actions in this document. The URL (for example |
317 | http://localhost.3000/foo/bar) consists of two parts, the base |
318 | (http://localhost:3000/ in this example) and the path (foo/bar). Please |
319 | note that the trailing slash after the hostname[:port] always belongs to |
320 | base and not to the action. |
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321 | |
322 | Catalyst supports several types of actions: |
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323 | |
324 | =over 4 |
325 | |
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326 | =item * B<Literal> (B<Path> actions) |
fc7ec1d9 |
327 | |
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328 | package MyApp::Controller::My::Controller; |
f29c48dd |
329 | sub bar : Path('foo/bar') { } |
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330 | |
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331 | Literal C<Path> actions will act relative to their current |
332 | namespace. The above example matches only |
333 | http://localhost:3000/my/controller/foo/bar. If you start your path with |
334 | a forward slash, it will match from the root. Example: |
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335 | |
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336 | package MyApp::Controller::My::Controller; |
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337 | sub bar : Path('/foo/bar') { } |
338 | |
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339 | Matches only http://localhost:3000/foo/bar. |
340 | |
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341 | package MyApp::Controller::My::Controller; |
0cf56dbc |
342 | sub bar : Path { } |
343 | |
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344 | By leaving the C<Path> definition empty, it will match on the namespace |
345 | root. The above code matches http://localhost:3000/my/controller. |
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346 | |
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347 | =item * B<Regex> |
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348 | |
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349 | sub bar : Regex('^item(\d+)/order(\d+)$') { } |
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350 | |
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351 | Matches any URL that matches the pattern in the action key, e.g. |
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352 | http://localhost:3000/item23/order42. The '' around the regexp is |
353 | optional, but perltidy likes it. :) |
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354 | |
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355 | Regex matches act globally, i.e. without reference to the namespace from |
356 | which it is called, so that a C<bar> method in the |
357 | C<MyApp::Controller::Catalog::Order::Process> namespace won't match any |
358 | form of C<bar>, C<Catalog>, C<Order>, or C<Process> unless you |
359 | explicitly put this in the regex. To achieve the above, you should |
360 | consider using a C<LocalRegex> action. |
66f6e959 |
361 | |
362 | =item * B<LocalRegex> |
363 | |
364 | sub bar : LocalRegex('^widget(\d+)$') { } |
fc7ec1d9 |
365 | |
66f6e959 |
366 | LocalRegex actions act locally. If you were to use C<bar> in |
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367 | C<MyApp::Controller::Catalog>, the above example would match urls like |
368 | http://localhost:3000/catalog/widget23. |
369 | |
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370 | If you omit the "C<^>" from your regex, then it will match any depth |
371 | from the controller and not immediately off of the controller name. The |
372 | following example differs from the above code in that it will match |
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373 | http://localhost:3000/catalog/foo/widget23 as well. |
374 | |
375 | package MyApp::Controller::Catalog; |
376 | sub bar : LocalRegex('widget(\d+)$') { } |
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377 | |
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378 | For both LocalRegex and Regex actions, if you use capturing parentheses |
379 | to extract values within the matching URL, those values are available in |
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380 | the C<$c-E<gt>req-E<gt>captures> array. In the above example, "widget23" |
e178a66a |
381 | would capture "23" in the above example, and |
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382 | C<$c-E<gt>req-E<gt>captures-E<gt>[0]> would be "23". If you want to pass |
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383 | arguments at the end of your URL, you must use regex action keys. See |
384 | L</URL Path Handling> below. |
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385 | |
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386 | =item * B<Top-level> (B<Global>) |
cda8d1ac |
387 | |
388 | package MyApp; |
389 | sub foo : Global { } |
390 | |
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391 | Matches http://localhost:3000/foo. The function name is mapped directly |
392 | to the application base. |
cda8d1ac |
393 | |
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394 | =item * B<Namespace-Prefixed> (B<Local>) |
fc7ec1d9 |
395 | |
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396 | package MyApp::Controller::My::Controller; |
e3dc9d78 |
397 | sub foo : Local { } |
fc7ec1d9 |
398 | |
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399 | Matches http://localhost:3000/my/controller/foo. |
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400 | |
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401 | This action type indicates that the matching URL must be prefixed with a |
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402 | modified form of the component's class (package) name. This modified |
403 | class name excludes the parts that have a pre-defined meaning in |
404 | Catalyst ("MyApp::Controller" in the above example), replaces "::" with |
405 | "/", and converts the name to lower case. See L</Components> for a full |
406 | explanation of the pre-defined meaning of Catalyst component class |
407 | names. |
fc7ec1d9 |
408 | |
4a6895ce |
409 | =item * B<Private> |
fc7ec1d9 |
410 | |
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411 | sub foo : Private { } |
fc7ec1d9 |
412 | |
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413 | Matches no URL, and cannot be executed by requesting a URL that |
414 | corresponds to the action key. Private actions can be executed only |
415 | inside a Catalyst application, by calling the C<forward> method: |
fc7ec1d9 |
416 | |
5a8ed4fe |
417 | $c->forward('foo'); |
fc7ec1d9 |
418 | |
129cfe74 |
419 | See L</Flow Control> for a full explanation of C<forward>. Note that, as |
fc9c8698 |
420 | discussed there, when forwarding from another component, you must use |
421 | the absolute path to the method, so that a private C<bar> method in your |
422 | C<MyApp::Controller::Catalog::Order::Process> controller must, if called |
423 | from elsewhere, be reached with |
424 | C<$c-E<gt>forward('/catalog/order/process/bar')>. |
fc7ec1d9 |
425 | |
426 | =back |
427 | |
b33ed88c |
428 | B<Note:> After seeing these examples, you probably wonder what the point |
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429 | is of defining names for regex and path actions. Every public action is |
430 | also a private one, so you have one unified way of addressing components |
431 | in your C<forward>s. |
cda8d1ac |
432 | |
72d9bfc7 |
433 | =head4 Built-in Private Actions |
fc7ec1d9 |
434 | |
fc9c8698 |
435 | In response to specific application states, Catalyst will automatically |
436 | call these built-in private actions in your application class: |
fc7ec1d9 |
437 | |
438 | =over 4 |
439 | |
cda8d1ac |
440 | =item * B<default : Private> |
fc7ec1d9 |
441 | |
fc9c8698 |
442 | Called when no other action matches. Could be used, for example, for |
443 | displaying a generic frontpage for the main app, or an error page for |
444 | individual controllers. |
fc7ec1d9 |
445 | |
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446 | If C<default> isn't acting how you would expect, look at using a |
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447 | L</Literal> C<Path> action (with an empty path string). The difference is |
e178a66a |
448 | that C<Path> takes arguments relative from the namespace and C<default> |
449 | I<always> takes arguments relative from the root, regardless of what |
450 | controller it's in. |
0cf56dbc |
451 | |
66f6e959 |
452 | =item * B<index : Private> |
453 | |
454 | C<index> is much like C<default> except that it takes no arguments |
e178a66a |
455 | and it is weighted slightly higher in the matching process. It is |
456 | useful as a static entry point to a controller, e.g. to have a static |
61a9002d |
457 | welcome page. Note that it's also weighted higher than Path. |
66f6e959 |
458 | |
cda8d1ac |
459 | =item * B<begin : Private> |
fc7ec1d9 |
460 | |
fc9c8698 |
461 | Called at the beginning of a request, before any matching actions are |
462 | called. |
fc7ec1d9 |
463 | |
cda8d1ac |
464 | =item * B<end : Private> |
4a6895ce |
465 | |
fc7ec1d9 |
466 | Called at the end of a request, after all matching actions are called. |
467 | |
fc9c8698 |
468 | =back |
469 | |
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470 | =head4 Built-in actions in controllers/autochaining |
fc7ec1d9 |
471 | |
e178a66a |
472 | Package MyApp::Controller::Foo; |
cda8d1ac |
473 | sub begin : Private { } |
5a8ed4fe |
474 | sub default : Private { } |
eff5f524 |
475 | sub auto : Private { } |
fc7ec1d9 |
476 | |
fc9c8698 |
477 | You can define built-in private actions within your controllers as |
478 | well. The actions will override the ones in less-specific controllers, |
479 | or your application class. In other words, for each of the three |
480 | built-in private actions, only one will be run in any request |
e178a66a |
481 | cycle. Thus, if C<MyApp::Controller::Catalog::begin> exists, it will be |
482 | run in place of C<MyApp::begin> if you're in the C<catalog> namespace, |
483 | and C<MyApp::Controller::Catalog::Order::begin> would override this in |
484 | turn. |
fc9c8698 |
485 | |
eff5f524 |
486 | In addition to the normal built-in actions, you have a special action |
487 | for making chains, C<auto>. Such C<auto> actions will be run after any |
fc9c8698 |
488 | C<begin>, but before your action is processed. Unlike the other |
eff5f524 |
489 | built-ins, C<auto> actions I<do not> override each other; they will be |
490 | called in turn, starting with the application class and going through to |
491 | the I<most> specific class. I<This is the reverse of the order in which |
492 | the normal built-ins override each other>. |
fc9c8698 |
493 | |
494 | Here are some examples of the order in which the various built-ins |
495 | would be called: |
cda8d1ac |
496 | |
497 | =over 4 |
498 | |
fc9c8698 |
499 | =item for a request for C</foo/foo> |
cda8d1ac |
500 | |
501 | MyApp::begin |
80ef2e6d |
502 | MyApp::auto |
e178a66a |
503 | MyApp::Controller::Foo::default # in the absence of MyApp::Controller::Foo::Foo |
cda8d1ac |
504 | MyApp::end |
505 | |
fc9c8698 |
506 | =item for a request for C</foo/bar/foo> |
cda8d1ac |
507 | |
e178a66a |
508 | MyApp::Controller::Foo::Bar::begin |
80ef2e6d |
509 | MyApp::auto |
e178a66a |
510 | MyApp::Controller::Foo::auto |
511 | MyApp::Controller::Foo::Bar::auto |
512 | MyApp::Controller::Foo::Bar::default # for MyApp::Controller::Foo::Bar::foo |
513 | MyApp::Controller::Foo::Bar::end |
80ef2e6d |
514 | |
515 | =back |
516 | |
fc9c8698 |
517 | The C<auto> action is also distinguished by the fact that you can break |
518 | out of the processing chain by returning 0. If an C<auto> action returns |
519 | 0, any remaining actions will be skipped, except for C<end>. So, for the |
520 | request above, if the first auto returns false, the chain would look |
521 | like this: |
80ef2e6d |
522 | |
523 | =over 4 |
524 | |
fc9c8698 |
525 | =item for a request for C</foo/bar/foo> where first C<auto> returns |
526 | false |
80ef2e6d |
527 | |
e178a66a |
528 | MyApp::Controller::Foo::Bar::begin |
80ef2e6d |
529 | MyApp::auto |
e178a66a |
530 | MyApp::Controller::Foo::Bar::end |
cda8d1ac |
531 | |
532 | =back |
4a6895ce |
533 | |
fc9c8698 |
534 | An example of why one might use this is an authentication action: you |
535 | could set up a C<auto> action to handle authentication in your |
536 | application class (which will always be called first), and if |
537 | authentication fails, returning 0 would skip any remaining methods |
538 | for that URL. |
03805733 |
539 | |
fc9c8698 |
540 | B<Note:> Looking at it another way, C<auto> actions have to return a |
541 | true value to continue processing! You can also C<die> in the autochain |
542 | action; in that case, the request will go straight to the finalize |
543 | stage, without processing further actions. |
03805733 |
544 | |
6b10c72b |
545 | =head4 URL Path Handling |
4a6895ce |
546 | |
70d5ae49 |
547 | You can pass variable arguments as part of the URL path, separated with |
548 | forward slashes (/). If the action is a Regex or LocalRegex, the '$' anchor |
549 | must be used. For example, suppose you want to handle C</foo/$bar/$baz>, |
550 | where C<$bar> and C<$baz> may vary: |
4a6895ce |
551 | |
cda8d1ac |
552 | sub foo : Regex('^foo$') { my ($self, $context, $bar, $baz) = @_; } |
4a6895ce |
553 | |
fc9c8698 |
554 | But what if you also defined actions for C</foo/boo> and C</foo/boo/hoo>? |
4a6895ce |
555 | |
f29c48dd |
556 | sub boo : Path('foo/boo') { .. } |
557 | sub hoo : Path('foo/boo/hoo') { .. } |
4a6895ce |
558 | |
559 | Catalyst matches actions in most specific to least specific order: |
560 | |
561 | /foo/boo/hoo |
562 | /foo/boo |
fc9c8698 |
563 | /foo # might be /foo/bar/baz but won't be /foo/boo/hoo |
4a6895ce |
564 | |
fc9c8698 |
565 | So Catalyst would never mistakenly dispatch the first two URLs to the |
566 | '^foo$' action. |
fc7ec1d9 |
567 | |
70d5ae49 |
568 | If a Regex or LocalRegex action doesn't use the '$' anchor, the action will |
569 | still match a URL containing arguments, however the arguments won't be |
570 | available via C<@_>. |
571 | |
6b10c72b |
572 | =head4 Parameter Processing |
2ef2fb0f |
573 | |
fc9c8698 |
574 | Parameters passed in the URL query string are handled with methods in |
575 | the L<Catalyst::Request> class. The C<param> method is functionally |
576 | equivalent to the C<param> method of C<CGI.pm> and can be used in |
577 | modules that require this. |
2ef2fb0f |
578 | |
579 | # http://localhost:3000/catalog/view/?category=hardware&page=3 |
580 | my $category = $c->req->param('category'); |
581 | my $current_page = $c->req->param('page') || 1; |
582 | |
583 | # multiple values for single parameter name |
584 | my @values = $c->req->param('scrolling_list'); |
585 | |
586 | # DFV requires a CGI.pm-like input hash |
587 | my $results = Data::FormValidator->check($c->req->params, \%dfv_profile); |
588 | |
fc7ec1d9 |
589 | =head3 Flow Control |
590 | |
d08ced28 |
591 | You control the application flow with the C<forward> method, which |
592 | accepts the key of an action to execute. This can be an action in the |
593 | same or another Catalyst controller, or a Class name, optionally |
594 | followed by a method name. After a C<forward>, the control flow will |
595 | return to the method from which the C<forward> was issued. |
596 | |
597 | A C<forward> is similar to a method call. The main differences are that |
598 | it wraps the call in an C<eval> to allow exception handling; it |
599 | automatically passes along the context object (C<$c> or C<$context>); |
600 | and it allows profiling of each call (displayed in the log with |
601 | debugging enabled). |
fc7ec1d9 |
602 | |
e3dc9d78 |
603 | sub hello : Global { |
5a8ed4fe |
604 | my ( $self, $c ) = @_; |
605 | $c->stash->{message} = 'Hello World!'; |
d08ced28 |
606 | $c->forward('check_message'); # $c is automatically included |
5a8ed4fe |
607 | } |
fc7ec1d9 |
608 | |
4c6807d2 |
609 | sub check_message : Private { |
5a8ed4fe |
610 | my ( $self, $c ) = @_; |
611 | return unless $c->stash->{message}; |
4c6807d2 |
612 | $c->forward('show_message'); |
5a8ed4fe |
613 | } |
fc7ec1d9 |
614 | |
4c6807d2 |
615 | sub show_message : Private { |
5a8ed4fe |
616 | my ( $self, $c ) = @_; |
66f6e959 |
617 | $c->res->body( $c->stash->{message} ); |
5a8ed4fe |
618 | } |
3323f920 |
619 | |
d08ced28 |
620 | A C<forward> does not create a new request, so your request |
621 | object (C<$c-E<gt>req>) will remain unchanged. This is a |
622 | key difference between using C<forward> and issuing a |
623 | redirect. |
3323f920 |
624 | |
d08ced28 |
625 | You can pass new arguments to a C<forward> by adding them |
626 | in an anonymous array. In this case C<$c-E<gt>req-E<gt>args> |
627 | will be changed for the duration of the C<forward> only; upon |
628 | return, the original value of C<$c-E<gt>req-E<gt>args> will |
629 | be reset. |
3323f920 |
630 | |
631 | sub hello : Global { |
632 | my ( $self, $c ) = @_; |
633 | $c->stash->{message} = 'Hello World!'; |
d08ced28 |
634 | $c->forward('check_message',[qw/test1/]); |
635 | # now $c->req->args is back to what it was before |
3323f920 |
636 | } |
637 | |
d08ced28 |
638 | sub check_message : Private { |
639 | my ( $self, $c ) = @_; |
fabf3a10 |
640 | my $first_argument = $c->req->args->[0]; # now = 'test1' |
d08ced28 |
641 | # do something... |
642 | } |
b248fa4a |
643 | |
d08ced28 |
644 | As you can see from these examples, you can just use the method name as |
645 | long as you are referring to methods in the same controller. If you want |
646 | to forward to a method in another controller, or the main application, |
647 | you will have to refer to the method by absolute path. |
cda8d1ac |
648 | |
649 | $c->forward('/my/controller/action'); |
d08ced28 |
650 | $c->forward('/default'); # calls default in main application |
fc7ec1d9 |
651 | |
d08ced28 |
652 | Here are some examples of how to forward to classes and methods. |
fc7ec1d9 |
653 | |
e3dc9d78 |
654 | sub hello : Global { |
5a8ed4fe |
655 | my ( $self, $c ) = @_; |
e178a66a |
656 | $c->forward(qw/MyApp::Model::Hello say_hello/); |
5a8ed4fe |
657 | } |
fc7ec1d9 |
658 | |
e3dc9d78 |
659 | sub bye : Global { |
5a8ed4fe |
660 | my ( $self, $c ) = @_; |
e178a66a |
661 | $c->forward('MyApp::Model::Hello'); # no method: will try 'process' |
5a8ed4fe |
662 | } |
fc7ec1d9 |
663 | |
e178a66a |
664 | package MyApp::Model::Hello; |
fc7ec1d9 |
665 | |
666 | sub say_hello { |
667 | my ( $self, $c ) = @_; |
66f6e959 |
668 | $c->res->body('Hello World!'); |
fc7ec1d9 |
669 | } |
670 | |
671 | sub process { |
672 | my ( $self, $c ) = @_; |
66f6e959 |
673 | $c->res->body('Goodbye World!'); |
fc7ec1d9 |
674 | } |
675 | |
d08ced28 |
676 | Note that C<forward> returns to the calling action and continues |
13436c14 |
677 | processing after the action finishes. If you want all further processing |
678 | in the calling action to stop, use C<detach> instead, which will execute |
679 | the C<detach>ed action and not return to the calling sub. In both cases, |
680 | Catalyst will automatically try to call process() if you omit the |
681 | method. |
fc7ec1d9 |
682 | |
683 | =head3 Components |
684 | |
56d8daeb |
685 | Catalyst has an uncommonly flexible component system. You can define as |
cccc887d |
686 | many L</Models>, L</Views>, and L</Controllers> as you like. |
fc7ec1d9 |
687 | |
56d8daeb |
688 | All components must inherit from L<Catalyst::Base>, which provides a |
689 | simple class structure and some common class methods like C<config> and |
690 | C<new> (constructor). |
fc7ec1d9 |
691 | |
e178a66a |
692 | package MyApp::Controller::Catalog; |
fc7ec1d9 |
693 | |
694 | use strict; |
695 | use base 'Catalyst::Base'; |
696 | |
697 | __PACKAGE__->config( foo => 'bar' ); |
698 | |
699 | 1; |
700 | |
6b10c72b |
701 | You don't have to C<use> or otherwise register Models, Views, and |
702 | Controllers. Catalyst automatically discovers and instantiates them |
703 | when you call C<setup> in the main application. All you need to do is |
704 | put them in directories named for each Component type. Notice that you |
705 | can use some very terse aliases for each one. |
fc7ec1d9 |
706 | |
707 | =over 4 |
708 | |
4a6895ce |
709 | =item * B<MyApp/Model/> |
fc7ec1d9 |
710 | |
4a6895ce |
711 | =item * B<MyApp/M/> |
fc7ec1d9 |
712 | |
4a6895ce |
713 | =item * B<MyApp/View/> |
fc7ec1d9 |
714 | |
4a6895ce |
715 | =item * B<MyApp/V/> |
fc7ec1d9 |
716 | |
4a6895ce |
717 | =item * B<MyApp/Controller/> |
fc7ec1d9 |
718 | |
4a6895ce |
719 | =item * B<MyApp/C/> |
fc7ec1d9 |
720 | |
721 | =back |
722 | |
723 | =head4 Views |
724 | |
129cfe74 |
725 | To show how to define views, we'll use an already-existing base class for the |
726 | L<Template Toolkit|Template>, L<Catalyst::View::TT>. All we need to do is |
727 | inherit from this class: |
fc7ec1d9 |
728 | |
e178a66a |
729 | package MyApp::View::TT; |
fc7ec1d9 |
730 | |
731 | use strict; |
732 | use base 'Catalyst::View::TT'; |
733 | |
734 | 1; |
735 | |
b33ed88c |
736 | (You can also generate this automatically by using the helper script: |
737 | |
738 | script/myapp_create.pl view TT TT |
739 | |
fb9257c1 |
740 | where the first C<TT> tells the script that the name of the view should |
741 | be C<TT>, and the second that it should be a Template Toolkit view.) |
b33ed88c |
742 | |
129cfe74 |
743 | This gives us a process() method and we can now just do |
e178a66a |
744 | $c->forward('MyApp::View::TT') to render our templates. The base class |
745 | makes process() implicit, so we don't have to say |
746 | C<$c-E<gt>forward(qw/MyApp::View::TT process/)>. |
fc7ec1d9 |
747 | |
e3dc9d78 |
748 | sub hello : Global { |
5a8ed4fe |
749 | my ( $self, $c ) = @_; |
750 | $c->stash->{template} = 'hello.tt'; |
751 | } |
fc7ec1d9 |
752 | |
5a8ed4fe |
753 | sub end : Private { |
754 | my ( $self, $c ) = @_; |
e178a66a |
755 | $c->forward('MyApp::View::TT'); |
5a8ed4fe |
756 | } |
fc7ec1d9 |
757 | |
6b10c72b |
758 | You normally render templates at the end of a request, so it's a perfect |
759 | use for the global C<end> action. |
fc7ec1d9 |
760 | |
129cfe74 |
761 | Also, be sure to put the template under the directory specified in |
6b10c72b |
762 | C<$c-E<gt>config-E<gt>{root}>, or you'll be forced to look at our |
763 | eyecandy debug screen. ;) |
fc7ec1d9 |
764 | |
765 | =head4 Models |
766 | |
e178a66a |
767 | To show how to define models, again we'll use an already-existing base |
e112461a |
768 | class, this time for L<DBIx::Class>: L<Catalyst::Model::DBIC::Schema>. |
769 | We'll also need L<DBIx::Class::Schema::Loader>. |
fc7ec1d9 |
770 | |
771 | But first, we need a database. |
772 | |
773 | -- myapp.sql |
774 | CREATE TABLE foo ( |
775 | id INTEGER PRIMARY KEY, |
776 | data TEXT |
777 | ); |
778 | |
779 | CREATE TABLE bar ( |
780 | id INTEGER PRIMARY KEY, |
781 | foo INTEGER REFERENCES foo, |
782 | data TEXT |
783 | ); |
784 | |
785 | INSERT INTO foo (data) VALUES ('TEST!'); |
786 | |
787 | |
788 | % sqlite /tmp/myapp.db < myapp.sql |
789 | |
e112461a |
790 | Now we can create a DBIC::SchemaLoader component for this database. |
fc7ec1d9 |
791 | |
e112461a |
792 | script/myapp_create.pl model DBIC DBIC::SchemaLoader 'dbi:SQLite:/tmp/myapp.db' |
fc7ec1d9 |
793 | |
e112461a |
794 | L<DBIx::Class::Schema::Loader> automatically loads table layouts and |
795 | relationships. Use the stash to pass data to your templates. |
fc7ec1d9 |
796 | |
e112461a |
797 | We add the following to MyApp/Controller/Root.pm |
b248fa4a |
798 | |
e112461a |
799 | sub view : Global { |
800 | my ( $self, $c, $id ) = @_; |
801 | |
802 | $c->stash->{item} = $c->model('DBIC::Foo')->find($id); |
803 | } |
fc7ec1d9 |
804 | |
e112461a |
805 | 1; |
806 | |
5a8ed4fe |
807 | sub end : Private { |
808 | my ( $self, $c ) = @_; |
e112461a |
809 | |
5a8ed4fe |
810 | $c->stash->{template} ||= 'index.tt'; |
e112461a |
811 | $c->forward( $c->view('TT') ); |
5a8ed4fe |
812 | } |
fc7ec1d9 |
813 | |
e112461a |
814 | We then create a new template file "root/index.tt" containing: |
fc7ec1d9 |
815 | |
e112461a |
816 | The Id's data is [% item.data %] |
fc7ec1d9 |
817 | |
6b10c72b |
818 | Models do not have to be part of your Catalyst application; you |
819 | can always call an outside module that serves as your Model: |
820 | |
821 | # in a Controller |
822 | sub list : Local { |
823 | my ( $self, $c ) = @_; |
e112461a |
824 | |
6b10c72b |
825 | $c->stash->{template} = 'list.tt'; |
e112461a |
826 | |
827 | use Some::Outside::DBIC::Module; |
828 | my @records = Some::Outside::DBIC::Module->search({ |
829 | artist => 'sri', |
830 | }); |
831 | |
6b10c72b |
832 | $c->stash->{records} = \@records; |
833 | } |
834 | |
835 | But by using a Model that is part of your Catalyst application, you gain |
836 | several things: you don't have to C<use> each component, Catalyst will |
837 | find and load it automatically at compile-time; you can C<forward> to |
26e73131 |
838 | the module, which can only be done to Catalyst components; and only |
6b10c72b |
839 | Catalyst components can be fetched with |
e178a66a |
840 | C<$c-E<gt>model('SomeModel')>. |
6b10c72b |
841 | |
842 | Happily, since many people have existing Model classes that they |
843 | would like to use with Catalyst (or, conversely, they want to |
844 | write Catalyst models that can be used outside of Catalyst, e.g. |
845 | in a cron job), it's trivial to write a simple component in |
846 | Catalyst that slurps in an outside Model: |
847 | |
e112461a |
848 | package MyApp::Model::DB; |
849 | use base qw/Catalyst::Model::DBIC::Schema/; |
850 | __PACKAGE__->config( |
851 | schema_class => 'Some::DBIC::Schema', |
cccc887d |
852 | connect_info => ['dbi:SQLite:foo.db', '', '', {AutoCommit=>1}] |
e112461a |
853 | ); |
6b10c72b |
854 | 1; |
855 | |
e112461a |
856 | and that's it! Now C<Some::DBIC::Schema> is part of your |
857 | Cat app as C<MyApp::Model::DB>. |
6b10c72b |
858 | |
fc7ec1d9 |
859 | =head4 Controllers |
860 | |
129cfe74 |
861 | Multiple controllers are a good way to separate logical domains of your |
862 | application. |
fc7ec1d9 |
863 | |
e178a66a |
864 | package MyApp::Controller::Login; |
fc7ec1d9 |
865 | |
fb9257c1 |
866 | sub sign-in : Local { } |
867 | sub new-password : Local { } |
868 | sub sign-out : Local { } |
fc7ec1d9 |
869 | |
e178a66a |
870 | package MyApp::Controller::Catalog; |
fc7ec1d9 |
871 | |
e3dc9d78 |
872 | sub view : Local { } |
873 | sub list : Local { } |
fc7ec1d9 |
874 | |
e178a66a |
875 | package MyApp::Controller::Cart; |
fc7ec1d9 |
876 | |
e3dc9d78 |
877 | sub add : Local { } |
878 | sub update : Local { } |
879 | sub order : Local { } |
fc7ec1d9 |
880 | |
881 | =head3 Testing |
882 | |
e178a66a |
883 | Catalyst has a built-in http server for testing! (Later, you can easily |
884 | use a more powerful server, e.g. Apache/mod_perl, in a production |
885 | environment.) |
fc7ec1d9 |
886 | |
887 | Start your application on the command line... |
888 | |
b33ed88c |
889 | script/myapp_server.pl |
fc7ec1d9 |
890 | |
891 | ...then visit http://localhost:3000/ in a browser to view the output. |
892 | |
893 | You can also do it all from the command line: |
894 | |
b33ed88c |
895 | script/myapp_test.pl http://localhost/ |
fc7ec1d9 |
896 | |
897 | Have fun! |
898 | |
3cb1db8c |
899 | =head1 SUPPORT |
900 | |
901 | IRC: |
902 | |
903 | Join #catalyst on irc.perl.org. |
904 | |
72d9bfc7 |
905 | Mailing-lists: |
3cb1db8c |
906 | |
907 | http://lists.rawmode.org/mailman/listinfo/catalyst |
908 | http://lists.rawmode.org/mailman/listinfo/catalyst-dev |
909 | |
fc7ec1d9 |
910 | =head1 AUTHOR |
911 | |
cda8d1ac |
912 | Sebastian Riedel, C<sri@oook.de> |
913 | David Naughton, C<naughton@umn.edu> |
914 | Marcus Ramberg, C<mramberg@cpan.org> |
f531dd37 |
915 | Jesse Sheidlower, C<jester@panix.com> |
129cfe74 |
916 | Danijel Milicevic, C<me@danijel.de> |
fc7ec1d9 |
917 | |
918 | =head1 COPYRIGHT |
919 | |
aa2b0d97 |
920 | This program is free software, you can redistribute it and/or modify it |
921 | under the same terms as Perl itself. |