3 Catalyst::Manual::Tutorial::CatalystBasics - Catalyst Tutorial - Part 2: Catalyst Application Development Basics
8 This is B<Part 2 of 10> for the Catalyst tutorial.
10 L<Tutorial Overview|Catalyst::Manual::Tutorial>
16 L<Introduction|Catalyst::Manual::Tutorial::Intro>
24 L<More Catalyst Basics|Catalyst::Manual::Tutorial::MoreCatalystBasics>
28 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>
32 L<Authentication|Catalyst::Manual::Tutorial::Authentication>
36 L<Authorization|Catalyst::Manual::Tutorial::Authorization>
40 L<Debugging|Catalyst::Manual::Tutorial::Debugging>
44 L<Testing|Catalyst::Manual::Tutorial::Testing>
48 L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
52 L<Appendices|Catalyst::Manual::Tutorial::Appendices>
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:
64 =item * Helper Scripts
66 Catalyst helper scripts that can be used to rapidly bootstrap the
67 skeletal structure of an application.
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
76 L<Catalyst::Manual::About|Catalyst::Manual::About>. In short:
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
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
91 that generates other forms such as PDF documents, e-mails, or Excel
96 As suggested by its name, the controller takes user requests and routes
97 them to the necessary model and view.
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.
109 You can checkout the source code for this example from the catalyst
110 subversion repository as per the instructions in
111 L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>
114 =head1 CREATE A CATALYST PROJECT
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>.
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>:
130 created "Hello/script"
134 created "Hello/script/hello_create.pl"
137 The C<catalyst.pl> helper script will display the names of the
138 directories and files it creates:
140 Changes # Record of application changes
141 lib # Lib directory for Perl modules
142 Hello # Application code directory
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
148 hello.conf # Application configuration file
150 root # Equiv of htdocs, dir for templates, css, javascript
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
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".
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
181 Run the following command to start up the built-in development web
184 $ script/hello_server.pl
185 [debug] Debug messages enabled
186 [debug] Loaded plugins:
187 .----------------------------------------------------------------------------.
188 | Catalyst::Plugin::ConfigLoader 0.17 |
189 | Catalyst::Plugin::Static::Simple 0.20 |
190 '----------------------------------------------------------------------------'
192 [debug] Loaded dispatcher "Catalyst::Dispatcher"
193 [debug] Loaded engine "Catalyst::Engine::HTTP"
194 [debug] Found home "/home/me/Hello"
195 [debug] Loaded Config "/home/me/Hello/hello.conf"
196 [debug] Loaded components:
197 .-----------------------------------------------------------------+----------.
199 +-----------------------------------------------------------------+----------+
200 | Hello::Controller::Root | instance |
201 '-----------------------------------------------------------------+----------'
203 [debug] Loaded Private actions:
204 .----------------------+--------------------------------------+--------------.
205 | Private | Class | Method |
206 +----------------------+--------------------------------------+--------------+
207 | /default | Hello::Controller::Root | default |
208 | /end | Hello::Controller::Root | end |
209 '----------------------+--------------------------------------+--------------'
211 [info] Hello powered by Catalyst 5.7011
212 You can connect to your server at http://localhost:3000
214 Point your web browser to
215 L<http://localhost:3000|http://localhost:3000> (substituting a
216 different hostname or IP address as appropriate) and you should be
217 greeted by the Catalyst welcome screen. Information similar to the
218 following should be appended to the logging output of the development
221 [info] *** Request 1 (1.000/s) [10301] [Sun May 18 10:11:36 2008] ***
222 [debug] "GET" request for "/" from "127.0.0.1"
223 [info] Request took 0.017964s (55.667/s)
224 .----------------------------------------------------------------+-----------.
226 +----------------------------------------------------------------+-----------+
227 | /default | 0.000540s |
229 '----------------------------------------------------------------+-----------'
231 Press Ctrl-C to break out of the development server.
236 =head2 The Simplest Way
238 The Root.pm controller is a place to put global actions that usually
239 execute on the root URL. Open the C<lib/Hello/Controller/Root.pm> file in
240 your editor. You will see the "default" subroutine, which is
241 responsible for displaying the welcome screen that you just saw in
242 your browser. Later on you'll want to change that to something more
243 reasonable, such as a "404" message but for now just leave it alone.
245 sub default :Path :Args {
246 my ( $self, $c ) = @_;
248 $c->response->body( $c->welcome_message );
251 The "C<$c>" here refers to the Catalyst context, which is used to
252 access the Catalyst application. In addition to many other things,
253 the Catalyst context provides access to "response" and "request"
254 objects. (See L<Catalyst|Catalyst>,
255 L<Catalyst::Response|Catalyst::Response>, and
256 L<Catalyst::Request|Catalyst::Request>)
258 C<$c-E<gt>response-E<gt>body> sets the HTTP response (see
259 L<Catalyst::Response|Catalyst::Response>), while C<$c-E<gt>welcome_message>
260 is a special method that returns the welcome message that you saw in
263 The ":Path :Args" after the method name are attributes which determine
264 which URLs will be dispatched to this method. (Depending on your version of
265 Catalyst, it used to say "Private" but using that with default is
266 currently deprecated.)
268 Some MVC frameworks handle dispatching in a central place. Catalyst,
269 by policy, prefers to handle URL dispatching with attributes on
270 controller methods. There is a lot of flexibility in specifying which
271 URLs to match. This particular method will match all URLs, because it
272 doesn't specify the path (nothing comes after "Path"), and will accept
273 any number of args (nothing after args).
275 The default is to map URLs to controller names, and because of
276 the way that Perl handles namespaces through package names,
277 it is simple to create hierarchical structures in
278 Catalyst. This means that you can create controllers with deeply
279 nested actions in a clean and logical way.
281 For example, the URL C<http://hello.com/admin/articles/create> maps
282 to the package C<Hello::Controller::Admin::Articles>, and the C<create>
286 Add the following subroutine to your C<lib/Hello/Controller/Root.pm>
290 my ( $self, $c ) = @_;
292 $c->response->body("Hello, World!");
295 Here you're sending your own string to the webpage.
297 Save the file, start the server (stop and restart it if it's still
298 up), and go to L<http://localhost:3000/hello> to
301 =head2 Hello, World! Using a View and a Template
303 In the Catalyst world a "View" is not a page of XHTML or a template
304 designed to present a page to a browser. It is the module that
305 determines the type of view--HTML, pdf, XML. For the case of a
306 template view (such as the default Toolkit Template) the actual
307 templates go under the "root" directory.
309 To create a TT view, run:
311 $ script/hello_create.pl view TT TT
313 This creates the C<lib/Hello/View/TT.pm> module, which is a subclass of
314 C<Catalyst::View::TT>. The "view" keyword tells the create script that
315 you are creating a view, the first "TT" tells it that you are creating
316 a Template Toolkit view, and the second "TT" tells the script to name
317 the View module "TT.pm", which is a commonly used name for TT views.
318 (You can name it anything you want, such as "HTML.pm".) If you look at
319 TT.pm, you will find that it only contains a config statement to set
320 the TT extension to ".tt".
322 Now that the TT.pm "View" exists, Catalyst will autodiscover it and be
323 able to use it to display the view templates, using the "process"
324 method that it inherits from the C<Catalyst::View::TT class>.
326 Template Toolkit is a very full featured template facility, with
327 excellent documentation at
328 L<http://template-tookit.org/>,
329 but since this is not a TT tutorial, we'll stick to only basic TT
330 usage here (and explore some of the more common TT features in later
331 parts of the tutorial).
333 Create a C<root/hello.tt> template file (put it in the C<root> under
334 the C<Hello> directory that is the base of your application). Here is
337 [% META title = 'Hello, World!' %]
339 This is a TT view template, located in the 'root/' directory.
342 [% and %] are markers for the TT parts of the template. Inside you can
343 access Perl variables and classes, and use TT directives. The rest of
344 the template is normal HTML. Change the hello method in
345 C<lib/Hello/Controller/Root.pm> to the following:
348 my ( $self, $c ) = @_;
350 $c->stash->{template} = 'hello.tt';
353 This time, instead of doing C<$c-E<gt>response->body()>, you are setting
354 the value of the "template" hash key in the Catalyst "stash", an area
355 for putting information to share with other parts of your application.
356 The "template" key determines which template will be displayed at the
357 end of the method. Catalyst controllers have a default "end" action
358 for all methods which causes the first (or default) view to be
359 rendered (unless there's a C<$c-E<gt>response->body()> statement). So your
360 template will be magically displayed at the end of your method.
362 After saving the file, restart the development server, and look at
363 L<http://localhost:3000/hello> again. You should
364 see the template that you just made.
367 =head1 CREATE A SIMPLE CONTROLLER AND AN ACTION
369 Create a controller named "Site" by executing the create script:
371 $ script/hello_create.pl controller Site
373 This will create a C<lib/Hello/Controller/Site.pm> file (and a test
374 file). Bring Site.pm up in your editor, and you can see that there's
375 not much there. Most people probably don't bother to use the create
376 script to make controllers after they're used to using Catalyst.
378 In C<lib/Hello/Controller/Site.pm>, add the following method:
381 my ( $self, $c ) = @_;
383 $c->stash->{username} = "John";
384 $c->stash->{template} = 'site/test.tt';
387 Notice the "Local" attribute on the method. This will allow the action
388 to be executed on the "controller/method" URL, or, in this case,
389 "site/test", instead of at the root site URL, like "Global". It's not
390 actually necessary to set the template value, since by default TT will
391 attempt to render a template that follows the naming pattern
392 "controller/method.tt", and we're following that pattern here, but in
393 other situations you will need to specify the template (such as if
394 you've "forwarded" to the method, or if it doesn't follow the default
395 naming convention). We've also put the variable "name" into the stash,
396 for use in the template.
398 Make a subdirectory "site" in the "root" directory. Copy the hello.tt
399 file into the directory as C<root/site/test.tt>, or create a new
400 template file at that location. Include a line like:
402 <p>Hello, [% username %]!</p>
404 Bring up or restart the server. Notice in the server output that
405 C</site/test> is listed in the Loaded Path actions. Go to
406 L<http://localhost:3000/site/test>
408 You should see your test.tt file displayed, including the name "John"
409 that you set in the controller.
414 Gerda Shank, C<gerda.shank@gmail.com>
415 Kennedy Clark, C<hkclark@gmail.com>
417 Please report any errors, issues or suggestions to the author. The
418 most recent version of the Catalyst Tutorial can be found at
419 L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/Catalyst-Manual/lib/Catalyst/Manual/Tutorial/>.
421 Copyright 2006-2008, Kennedy Clark & Gerda Shank, under Creative Commons License
422 (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).