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1 | =head1 NAME |
2 | |
3 | Catalyst::Manual::Tutorial::CatalystBasics - Catalyst Tutorial - Part 2: Catalyst Application Development Basics |
4 | |
5 | |
6 | =head1 OVERVIEW |
7 | |
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8 | This is B<Part 2 of 10> for the Catalyst tutorial. |
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9 | |
10 | L<Tutorial Overview|Catalyst::Manual::Tutorial> |
11 | |
12 | =over 4 |
13 | |
14 | =item 1 |
15 | |
16 | L<Introduction|Catalyst::Manual::Tutorial::Intro> |
17 | |
18 | =item 2 |
19 | |
20 | B<Catalyst Basics> |
21 | |
22 | =item 3 |
23 | |
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24 | L<More Catalyst Basics|Catalyst::Manual::Tutorial::MoreCatalystBasics> |
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25 | |
26 | =item 4 |
27 | |
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28 | L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD> |
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29 | |
30 | =item 5 |
31 | |
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32 | L<Authentication|Catalyst::Manual::Tutorial::Authentication> |
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33 | |
34 | =item 6 |
35 | |
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36 | L<Authorization|Catalyst::Manual::Tutorial::Authorization> |
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37 | |
38 | =item 7 |
39 | |
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40 | L<Debugging|Catalyst::Manual::Tutorial::Debugging> |
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41 | |
42 | =item 8 |
43 | |
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44 | L<Testing|Catalyst::Manual::Tutorial::Testing> |
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45 | |
46 | =item 9 |
47 | |
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48 | L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD> |
49 | |
50 | =item 10 |
51 | |
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52 | L<Appendices|Catalyst::Manual::Tutorial::Appendices> |
53 | |
54 | =back |
55 | |
56 | |
57 | =head1 DESCRIPTION |
58 | |
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59 | In this part of the tutorial, we will create a very basic Catalyst web |
60 | application, demonstrating a number of powerful capabilities, such as: |
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61 | |
62 | =over 4 |
63 | |
64 | =item * Helper Scripts |
65 | |
66 | Catalyst helper scripts that can be used to rapidly bootstrap the |
67 | skeletal structure of an application. |
68 | |
69 | =item * MVC |
70 | |
71 | Model/View/Controller (MVC) provides an architecture that facilitates a |
72 | clean "separation of control" between the different portions of your |
73 | application. Given that many other documents cover this subject in |
74 | detail, MVC will not be discussed in depth here (for an excellent |
75 | introduction to MVC and general Catalyst concepts, please see |
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76 | L<Catalyst::Manual::About|Catalyst::Manual::About>). In short: |
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77 | |
78 | =over 4 |
79 | |
80 | =item * Model |
81 | |
82 | The model usually represents a data store. In most applications, the |
83 | model equates to the objects that are created from and saved to your SQL |
84 | database. |
85 | |
86 | =item * View |
87 | |
88 | The view takes model objects and renders them into something for the end |
89 | user to look at. Normally this involves a template-generation tool that |
90 | creates HTML for the user's web browser, but it could easily be code |
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91 | that generates other forms such as PDF documents, e-mails, spreadsheets, |
92 | or even "behind the scenes" formats such as XML and JSON. |
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93 | |
94 | =item * Controller |
95 | |
96 | As suggested by its name, the controller takes user requests and routes |
97 | them to the necessary model and view. |
98 | |
99 | =back |
100 | |
101 | =item * ORM |
102 | |
103 | The use of Object-Relational Mapping (ORM) technology for database |
104 | access. Specifically, ORM provides an automated and standardized means |
105 | to persist and restore objects to/from a relational database. |
106 | |
107 | =back |
108 | |
109 | You can checkout the source code for this example from the catalyst |
110 | subversion repository as per the instructions in |
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111 | L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>. |
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112 | |
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113 | |
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114 | =head1 CREATE A CATALYST PROJECT |
115 | |
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116 | Catalyst provides a number of helper scripts that can be used to |
117 | quickly flesh out the basic structure of your application. All |
118 | Catalyst projects begin with the C<catalyst.pl> helper (see |
119 | L<Catalyst::Helper|Catalyst::Helper> for more information on helpers). |
120 | Also note that as of Catalyst 5.7000, you will not have the helper |
121 | scripts unless you install both L<Catalyst::Runtime|Catalyst::Runtime> |
122 | and L<Catalyst::Devel|Catalyst::Devel>. |
123 | |
124 | In this first part of the tutorial, use the Catalyst |
125 | C<catalyst.pl> script to initialize the framework for an |
126 | application called C<Hello>: |
127 | |
128 | $ catalyst.pl Hello |
129 | created "Hello" |
130 | created "Hello/script" |
131 | created "Hello/lib" |
132 | created "Hello/root" |
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133 | ... |
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134 | created "Hello/script/hello_create.pl" |
135 | $ cd Hello |
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136 | |
137 | The C<catalyst.pl> helper script will display the names of the |
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138 | directories and files it creates: |
139 | |
140 | Changes # Record of application changes |
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141 | lib # Lib directory for your app's Perl modules |
142 | Hello # Application main code directory |
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143 | Controller # Directory for Controller modules |
144 | Model # Directory for Models |
145 | View # Directory for Views |
146 | Hello.pm # Base application module |
147 | Makefile.PL # Makefile to build application |
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148 | hello.conf # Application configuration file |
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149 | README # README file |
150 | root # Equiv of htdocs, dir for templates, css, javascript |
151 | favicon.ico |
152 | static # Directory for static files |
153 | images # Directory for image files used in welcome screen |
154 | script # Directory for Perl scripts |
155 | hello_cgi.pl # To run your app as a cgi (not recommended) |
156 | hello_create.pl # To create models, views, controllers |
157 | hello_fastcgi.pl # To run app as a fastcgi program |
158 | hello_server.pl # The normal development server |
159 | hello_test.pl # Test your app from the command line |
160 | t # Directory for tests |
161 | 01app.t # Test scaffold |
162 | 02pod.t |
163 | 03podcoverage.t |
164 | |
165 | |
166 | Catalyst will "auto-discover" modules in the Controller, Model, and |
167 | View directories. When you use the hello_create.pl script it will |
168 | create Perl module scaffolds in those directories, plus test files in |
169 | the "t" directory. The default location for templates is in the "root" |
170 | directory. The scripts in the script directory will always start with |
171 | the lowercased version of your application name. If your app is |
172 | MaiTai, then the create script would be "maitai_create.pl". |
173 | |
174 | Though it's too early for any significant celebration, we already have |
175 | a functioning application. We can use the Catalyst supplied script to |
176 | start up a development server and view the default Catalyst page in |
177 | your browser. All scripts in the script directory should be run from |
178 | the base directory of your application, so change to the Hello |
179 | directory. |
180 | |
181 | Run the following command to start up the built-in development web |
182 | server: |
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183 | |
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184 | $ script/hello_server.pl |
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185 | [debug] Debug messages enabled |
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186 | [debug] Statistics enabled |
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187 | [debug] Loaded plugins: |
188 | .----------------------------------------------------------------------------. |
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189 | | Catalyst::Plugin::ConfigLoader 0.20 | |
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190 | | Catalyst::Plugin::Static::Simple 0.20 | |
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191 | '----------------------------------------------------------------------------' |
192 | |
193 | [debug] Loaded dispatcher "Catalyst::Dispatcher" |
194 | [debug] Loaded engine "Catalyst::Engine::HTTP" |
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195 | [debug] Found home "/home/me/Hello" |
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196 | [debug] Loaded Config "/home/me/Hello/hello.conf" |
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197 | [debug] Loaded components: |
198 | .-----------------------------------------------------------------+----------. |
199 | | Class | Type | |
200 | +-----------------------------------------------------------------+----------+ |
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201 | | Hello::Controller::Root | instance | |
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202 | '-----------------------------------------------------------------+----------' |
203 | |
204 | [debug] Loaded Private actions: |
205 | .----------------------+--------------------------------------+--------------. |
206 | | Private | Class | Method | |
207 | +----------------------+--------------------------------------+--------------+ |
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208 | | /default | Hello::Controller::Root | default | |
209 | | /end | Hello::Controller::Root | end | |
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210 | '----------------------+--------------------------------------+--------------' |
211 | |
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212 | [debug] Loaded Path actions: |
213 | .-------------------------------------+--------------------------------------. |
214 | | Path | Private | |
215 | +-------------------------------------+--------------------------------------+ |
216 | | / | /default | |
217 | | / | /index | |
218 | '-------------------------------------+--------------------------------------' |
219 | |
220 | [info] Hello powered by Catalyst 5.7014 |
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221 | You can connect to your server at http://localhost:3000 |
222 | |
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223 | Point your web browser to |
224 | L<http://localhost:3000|http://localhost:3000> (substituting a |
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225 | different hostname or IP address as appropriate) and you should be |
226 | greeted by the Catalyst welcome screen. Information similar to the |
227 | following should be appended to the logging output of the development |
228 | server: |
229 | |
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230 | [info] *** Request 1 (1.000/s) [10301] [Sun Nov 23 10:11:36 2008] *** |
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231 | [debug] "GET" request for "/" from "127.0.0.1" |
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232 | [info] Request took 0.017964s (55.667/s) |
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233 | .----------------------------------------------------------------+-----------. |
234 | | Action | Time | |
235 | +----------------------------------------------------------------+-----------+ |
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236 | | /default | 0.000540s | |
237 | | /end | 0.001246s | |
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238 | '----------------------------------------------------------------+-----------' |
239 | |
240 | Press Ctrl-C to break out of the development server. |
241 | |
242 | |
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243 | =head1 HELLO WORLD |
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244 | |
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245 | =head2 The Simplest Way |
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246 | |
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247 | The Root.pm controller is a place to put global actions that usually |
248 | execute on the root URL. Open the C<lib/Hello/Controller/Root.pm> file in |
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249 | your editor. You will see the "index" subroutine, which is |
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250 | responsible for displaying the welcome screen that you just saw in |
251 | your browser. Later on you'll want to change that to something more |
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252 | reasonable, such as a "404" message or a redirect, but for now just |
253 | leave it alone. |
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254 | |
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255 | sub index :Path :Args(0) { |
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256 | my ( $self, $c ) = @_; |
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257 | |
258 | # Hello World |
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259 | $c->response->body( $c->welcome_message ); |
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260 | } |
261 | |
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262 | The "C<$c>" here refers to the Catalyst context, which is used to |
263 | access the Catalyst application. In addition to many other things, |
264 | the Catalyst context provides access to "response" and "request" |
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265 | objects. (See L<Catalyst|Catalyst>, |
266 | L<Catalyst::Response|Catalyst::Response>, and |
267 | L<Catalyst::Request|Catalyst::Request>) |
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268 | |
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269 | C<$c-E<gt>response-E<gt>body> sets the HTTP response (see |
270 | L<Catalyst::Response|Catalyst::Response>), while C<$c-E<gt>welcome_message> |
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271 | is a special method that returns the welcome message that you saw in |
272 | your browser. |
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273 | |
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274 | The ":Path :Args(0)" after the method name are attributes which determine |
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275 | which URLs will be dispatched to this method. (Depending on your version of |
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276 | Catalyst, it used to say "Private" but using that with 'default' or 'index' |
277 | is currently deprecated.) |
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278 | |
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279 | Some MVC frameworks handle dispatching in a central place. Catalyst, |
280 | by policy, prefers to handle URL dispatching with attributes on |
281 | controller methods. There is a lot of flexibility in specifying which |
282 | URLs to match. This particular method will match all URLs, because it |
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283 | doesn't specify the path (nothing comes after "Path"), but will only |
284 | accept a single args because of the ":Args(0)". |
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285 | |
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286 | The default is to map URLs to controller names, and because of |
287 | the way that Perl handles namespaces through package names, |
288 | it is simple to create hierarchical structures in |
289 | Catalyst. This means that you can create controllers with deeply |
290 | nested actions in a clean and logical way. |
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291 | |
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292 | For example, the URL C<http://hello.com/admin/articles/create> maps |
293 | to the package C<Hello::Controller::Admin::Articles>, and the C<create> |
294 | method. |
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295 | |
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296 | Add the following subroutine to your C<lib/Hello/Controller/Root.pm> |
297 | file: |
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298 | |
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299 | sub hello : Global { |
300 | my ( $self, $c ) = @_; |
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301 | |
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302 | $c->response->body("Hello, World!"); |
303 | } |
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304 | |
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305 | Here you're sending your own string to the webpage. |
306 | |
307 | Save the file, start the server (stop and restart it if it's still |
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308 | up), and go to L<http://localhost:3000/hello> to |
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309 | see "Hello, World!" |
310 | |
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311 | |
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312 | =head2 Hello, World! Using a View and a Template |
313 | |
314 | In the Catalyst world a "View" is not a page of XHTML or a template |
315 | designed to present a page to a browser. It is the module that |
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316 | determines the I<type> of view -- HTML, pdf, XML, etc. For the |
317 | thing that generates the I<content> of that view, (such as the |
318 | default Toolkit Template) the actual templates go under the |
319 | "root" directory. |
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320 | |
321 | To create a TT view, run: |
322 | |
323 | $ script/hello_create.pl view TT TT |
324 | |
325 | This creates the C<lib/Hello/View/TT.pm> module, which is a subclass of |
326 | C<Catalyst::View::TT>. The "view" keyword tells the create script that |
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327 | you are creating a view, the second "TT" tells it that you are creating |
328 | a Template Toolkit view, and the first "TT" tells the script to name |
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329 | the View module "TT.pm", which is a commonly used name for TT views. |
330 | (You can name it anything you want, such as "HTML.pm".) If you look at |
331 | TT.pm, you will find that it only contains a config statement to set |
332 | the TT extension to ".tt". |
333 | |
334 | Now that the TT.pm "View" exists, Catalyst will autodiscover it and be |
335 | able to use it to display the view templates, using the "process" |
336 | method that it inherits from the C<Catalyst::View::TT class>. |
337 | |
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338 | Template Toolkit is a very full featured template facility, with |
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339 | excellent documentation at L<http://template-toolkit.org/>, |
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340 | but since this is not a TT tutorial, we'll stick to only basic TT |
341 | usage here (and explore some of the more common TT features in later |
342 | parts of the tutorial). |
343 | |
344 | Create a C<root/hello.tt> template file (put it in the C<root> under |
345 | the C<Hello> directory that is the base of your application). Here is |
346 | a simple sample: |
347 | |
348 | [% META title = 'Hello, World!' %] |
349 | <p> |
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350 | This is a TT view template, located in the 'root/' directory. |
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351 | </p> |
352 | |
353 | [% and %] are markers for the TT parts of the template. Inside you can |
354 | access Perl variables and classes, and use TT directives. The rest of |
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355 | the template is normal HTML. Change the hello method in |
356 | C<lib/Hello/Controller/Root.pm> to the following: |
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357 | |
358 | sub hello : Global { |
359 | my ( $self, $c ) = @_; |
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360 | |
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361 | $c->stash->{template} = 'hello.tt'; |
362 | } |
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363 | |
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364 | This time, instead of doing C<$c-E<gt>response->body()>, you are setting |
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365 | the value of the "template" hash key in the Catalyst "stash", an area |
366 | for putting information to share with other parts of your application. |
367 | The "template" key determines which template will be displayed at the |
368 | end of the method. Catalyst controllers have a default "end" action |
369 | for all methods which causes the first (or default) view to be |
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370 | rendered (unless there's a C<$c-E<gt>response->body()> statement). So your |
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371 | template will be magically displayed at the end of your method. |
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372 | |
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373 | After saving the file, restart the development server, and look at |
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374 | L<http://localhost:3000/hello> again. You should |
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375 | see the template that you just made. |
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376 | |
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377 | |
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378 | =head1 CREATE A SIMPLE CONTROLLER AND AN ACTION |
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379 | |
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380 | Create a controller named "Site" by executing the create script: |
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381 | |
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382 | $ script/hello_create.pl controller Site |
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383 | |
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384 | This will create a C<lib/Hello/Controller/Site.pm> file (and a test |
385 | file). Bring Site.pm up in your editor, and you can see that there's |
386 | not much there. Most people probably don't bother to use the create |
387 | script to make controllers after they're used to using Catalyst. |
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388 | |
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389 | In C<lib/Hello/Controller/Site.pm>, add the following method: |
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390 | |
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391 | sub test : Local { |
392 | my ( $self, $c ) = @_; |
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393 | |
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394 | $c->stash->{username} = "John"; |
395 | $c->stash->{template} = 'site/test.tt'; |
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396 | } |
397 | |
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398 | Notice the "Local" attribute on the method. This will allow the action |
399 | to be executed on the "controller/method" URL, or, in this case, |
400 | "site/test", instead of at the root site URL, like "Global". It's not |
401 | actually necessary to set the template value, since by default TT will |
402 | attempt to render a template that follows the naming pattern |
403 | "controller/method.tt", and we're following that pattern here, but in |
404 | other situations you will need to specify the template (such as if |
405 | you've "forwarded" to the method, or if it doesn't follow the default |
406 | naming convention). We've also put the variable "name" into the stash, |
407 | for use in the template. |
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408 | |
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409 | Make a subdirectory "site" in the "root" directory. Copy the hello.tt |
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410 | file into the directory as C<root/site/test.tt>, or create a new |
411 | template file at that location. Include a line like: |
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412 | |
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413 | <p>Hello, [% username %]!</p> |
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414 | |
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415 | Bring up or restart the server. Notice in the server output that |
416 | C</site/test> is listed in the Loaded Path actions. Go to |
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417 | L<http://localhost:3000/site/test> in your browser. |
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418 | |
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419 | You should see your test.tt file displayed, including the name "John" |
420 | that you set in the controller. |
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421 | |
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422 | |
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423 | =head1 AUTHORS |
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424 | |
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425 | Gerda Shank, C<gerda.shank@gmail.com> |
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426 | Kennedy Clark, C<hkclark@gmail.com> |
427 | |
428 | Please report any errors, issues or suggestions to the author. The |
429 | most recent version of the Catalyst Tutorial can be found at |
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430 | L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>. |
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431 | |
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432 | Copyright 2006-2008, Kennedy Clark & Gerda Shank, under Creative Commons License |
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433 | (L<http://creativecommons.org/licenses/by-sa/3.0/us/>). |