3 Catalyst::Manual::Tutorial::02_CatalystBasics - Catalyst Tutorial - Chapter 2: Catalyst Application Development Basics
8 This is B<Chapter 2 of 10> for the Catalyst tutorial.
10 L<Tutorial Overview|Catalyst::Manual::Tutorial>
16 L<Introduction|Catalyst::Manual::Tutorial::01_Intro>
24 L<More Catalyst Basics|Catalyst::Manual::Tutorial::03_MoreCatalystBasics>
28 L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
32 L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>
36 L<Authorization|Catalyst::Manual::Tutorial::06_Authorization>
40 L<Debugging|Catalyst::Manual::Tutorial::07_Debugging>
44 L<Testing|Catalyst::Manual::Tutorial::08_Testing>
48 L<Advanced CRUD|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
52 L<Appendices|Catalyst::Manual::Tutorial::10_Appendices>
59 In this chapter of the tutorial, we will create a very basic Catalyst
60 web application, demonstrating a number of powerful capabilities, such
65 =item * Helper Scripts
67 Catalyst helper scripts that can be used to rapidly bootstrap the
68 skeletal structure of an application.
72 Model/View/Controller (MVC) provides an architecture that facilitates a
73 clean "separation of control" between the different portions of your
74 application. Given that many other documents cover this subject in
75 detail, MVC will not be discussed in depth here (for an excellent
76 introduction to MVC and general Catalyst concepts, please see
77 L<Catalyst::Manual::About|Catalyst::Manual::About>). In short:
83 The model usually represents a data store. In most applications, the
84 model equates to the objects that are created from and saved to your SQL
89 The view takes model objects and renders them into something for the end
90 user to look at. Normally this involves a template-generation tool that
91 creates HTML for the user's web browser, but it could easily be code
92 that generates other forms such as PDF documents, e-mails, spreadsheets,
93 or even "behind the scenes" formats such as XML and JSON.
97 As suggested by its name, the controller takes user requests and routes
98 them to the necessary model and view.
104 The use of Object-Relational Mapping (ORM) technology for database
105 access. Specifically, ORM provides an automated and standardized means
106 to persist and restore objects to/from a relational database and will
107 automatically create our Catalyst model for use with a database.
111 You can checkout the source code for this example from the catalyst
112 subversion repository as per the instructions in
113 L<Catalyst::Manual::Tutorial::01_Intro|Catalyst::Manual::Tutorial::01_Intro>.
116 =head1 CREATE A CATALYST PROJECT
118 Catalyst provides a number of helper scripts that can be used to
119 quickly flesh out the basic structure of your application. All
120 Catalyst projects begin with the C<catalyst.pl> helper (see
121 L<Catalyst::Helper|Catalyst::Helper> for more information on helpers).
122 Also note that as of Catalyst 5.7000, you will not have the helper
123 scripts unless you install both L<Catalyst::Runtime|Catalyst::Runtime>
124 and L<Catalyst::Devel|Catalyst::Devel>.
126 In this first chapter of the tutorial, use the Catalyst C<catalyst.pl>
127 script to initialize the framework for an application called C<Hello>:
131 created "Hello/script"
135 created "Hello/script/hello_create.pl"
136 Change to application directory and Run "perl Makefile.PL" to make sure your install is complete
139 Note: If you are using Strawberry Perl on Win32, drop the ".pl"
140 from the end of the "catalyst.pl" command and simply use
143 The C<catalyst.pl> helper script will display the names of the
144 directories and files it creates:
146 Changes # Record of application changes
147 lib # Lib directory for your app's Perl modules
148 Hello # Application main code directory
149 Controller # Directory for Controller modules
150 Model # Directory for Models
151 View # Directory for Views
152 Hello.pm # Base application module
153 Makefile.PL # Makefile to build application
154 hello.conf # Application configuration file
156 root # Equiv of htdocs, dir for templates, css, javascript
158 static # Directory for static files
159 images # Directory for image files used in welcome screen
160 script # Directory for Perl scripts
161 hello_cgi.pl # To run your app as a cgi (not recommended)
162 hello_create.pl # To create models, views, controllers
163 hello_fastcgi.pl # To run app as a fastcgi program
164 hello_server.pl # The normal development server
165 hello_test.pl # Test your app from the command line
166 t # Directory for tests
167 01app.t # Test scaffold
172 Catalyst will "auto-discover" modules in the Controller, Model, and
173 View directories. When you use the hello_create.pl script it will
174 create Perl module scaffolds in those directories, plus test files in
175 the "t" directory. The default location for templates is in the "root"
176 directory. The scripts in the script directory will always start with
177 the lowercased version of your application name. If your app is
178 MaiTai, then the create script would be "maitai_create.pl".
180 Though it's too early for any significant celebration, we already have
181 a functioning application. We can use the Catalyst supplied script to
182 start up a development server and view the default Catalyst page in
183 your browser. All scripts in the script directory should be run from
184 the base directory of your application, so change to the Hello
187 Run the following command to start up the built-in development web
188 server (make sure you didn't forget the "C<cd Hello>" from the
191 $ script/hello_server.pl
192 [debug] Debug messages enabled
193 [debug] Statistics enabled
194 [debug] Loaded plugins:
195 .----------------------------------------------------------------------------.
196 | Catalyst::Plugin::ConfigLoader 0.27 |
197 '----------------------------------------------------------------------------'
199 [debug] Loaded dispatcher "Catalyst::Dispatcher"
200 [debug] Loaded engine "Catalyst::Engine::HTTP"
201 [debug] Found home "/home/me/Hello"
202 [debug] Loaded Config "/home/me/Hello/hello.conf"
203 [debug] Loaded components:
204 .-----------------------------------------------------------------+----------.
206 +-----------------------------------------------------------------+----------+
207 | Hello::Controller::Root | instance |
208 '-----------------------------------------------------------------+----------'
210 [debug] Loaded Private actions:
211 .----------------------+--------------------------------------+--------------.
212 | Private | Class | Method |
213 +----------------------+--------------------------------------+--------------+
214 | /default | Hello::Controller::Root | default |
215 | /end | Hello::Controller::Root | end |
216 | /index | Hello::Controller::Root | index |
217 '----------------------+--------------------------------------+--------------'
219 [debug] Loaded Path actions:
220 .-------------------------------------+--------------------------------------.
222 +-------------------------------------+--------------------------------------+
225 '-------------------------------------+--------------------------------------'
227 [info] Hello powered by Catalyst 5.80018
228 You can connect to your server at http://debian:3000
230 Point your web browser to L<http://localhost:3000> (substituting a
231 different hostname or IP address as appropriate) and you should be
232 greeted by the Catalyst welcome screen (if you get some other welcome
233 screen or an "Index" screen, you probably forgot to specify port 3000
234 in your URL). Information similar to the following should be appended
235 to the logging output of the development server:
237 [info] *** Request 1 (0.005/s) [20712] [Sun Oct 11 11:58:51 2009] ***
238 [debug] "GET" request for "/" from "172.0.0.1"
239 [info] Request took 0.007342s (136.203/s)
240 .----------------------------------------------------------------+-----------.
242 +----------------------------------------------------------------+-----------+
243 | /index | 0.000491s |
245 '----------------------------------------------------------------+-----------'
247 Press Ctrl-C to break out of the development server.
252 =head2 The Simplest Way
254 The Root.pm controller is a place to put global actions that usually
255 execute on the root URL. Open the C<lib/Hello/Controller/Root.pm> file in
256 your editor. You will see the "index" subroutine, which is
257 responsible for displaying the welcome screen that you just saw in
258 your browser. Later on you'll want to change that to something more
259 reasonable, such as a "404" message or a redirect, but for now just
262 sub index :Path :Args(0) {
263 my ( $self, $c ) = @_;
266 $c->response->body( $c->welcome_message );
269 The "C<$c>" here refers to the Catalyst context, which is used to
270 access the Catalyst application. In addition to many other things,
271 the Catalyst context provides access to "response" and "request"
272 objects. (See L<Catalyst|Catalyst>,
273 L<Catalyst::Response|Catalyst::Response>, and
274 L<Catalyst::Request|Catalyst::Request>)
276 C<$c-E<gt>response-E<gt>body> sets the HTTP response (see
277 L<Catalyst::Response|Catalyst::Response>), while C<$c-E<gt>welcome_message>
278 is a special method that returns the welcome message that you saw in
281 The ":Path :Args(0)" after the method name are attributes which
282 determine which URLs will be dispatched to this method. (You might see
283 ":Private" if you are using an older version of Catalyst, but using
284 that with 'default' or 'index' is currently deprecated. If so, you
285 should also probably upgrade before continuing the tutorial.)
287 Some MVC frameworks handle dispatching in a central place. Catalyst,
288 by policy, prefers to handle URL dispatching with attributes on
289 controller methods. There is a lot of flexibility in specifying which
290 URLs to match. This particular method will match all URLs, because it
291 doesn't specify the path (nothing comes after "Path"), but will only
292 accept a URL without any args because of the ":Args(0)".
294 The default is to map URLs to controller names, and because of the way
295 that Perl handles namespaces through package names, it is simple to
296 create hierarchical structures in Catalyst. This means that you can
297 create controllers with deeply nested actions in a clean and logical
298 way. For example, the URL C<http://hello.com/admin/articles/create>
299 maps to the package C<Hello::Controller::Admin::Articles>, and the
302 Add the following subroutine to your C<lib/Hello/Controller/Root.pm>
306 my ( $self, $c ) = @_;
308 $c->response->body("Hello, World!");
311 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
312 cutting and pasting example code from POD-based documents.
314 Here you're sending your own string to the webpage.
316 Save the file, start the server (stop and restart it if it's still
317 running), and go to L<http://localhost:3000/hello> to
318 see "Hello, World!" Also notice that a new action is listed under
319 "Loaded Private actions" in the development server debug output.
322 =head2 Hello, World! Using a View and a Template
324 In the Catalyst world a "View" itself is not a page of XHTML or a
325 template designed to present a page to a browser. Rather, it is the
326 module that determines the I<type> of view -- HTML, pdf, XML, etc. For
327 the thing that generates the I<content> of that view (such as the a
328 Toolkit Template template file), the actual templates go under the
331 To create a TT view, run:
333 $ script/hello_create.pl view TT TT
335 This creates the C<lib/Hello/View/TT.pm> module, which is a subclass of
336 C<Catalyst::View::TT>.
342 The "view" keyword tells the create script that you are creating a view.
346 The first "TT" tells the script to name the View module "TT.pm", which is a
347 commonly used name for TT views. (You can name it anything you want, such as
352 The final "TT" tells Catalyst the I<type> of the view, with "TT"
353 indicating that you want to a Template Toolkit view.
357 If you look at C<lib/Hello/View/TT.pm> you will find that it only
358 contains a config statement to set the TT extension to ".tt".
360 Now that the TT.pm "View" exists, Catalyst will autodiscover it and be
361 able to use it to display the view templates using the "process"
362 method that it inherits from the C<Catalyst::View::TT class>.
364 Template Toolkit is a very full featured template facility, with
365 excellent documentation at L<http://template-toolkit.org/>,
366 but since this is not a TT tutorial, we'll stick to only basic TT
367 usage here (and explore some of the more common TT features in later
368 chapters of the tutorial).
370 Create a C<root/hello.tt> template file (put it in the C<root> under
371 the C<Hello> directory that is the base of your application). Here is
375 This is a TT view template, called '[% template.name %]'.
378 [% and %] are markers for the TT parts of the template. Inside you can
379 access Perl variables and classes, and use TT directives. In this
380 case, we're using a special TT variable that defines the name of the
381 template file (C<hello.tt>). The rest of the template is normal HTML.
383 Change the hello method in C<lib/Hello/Controller/Root.pm> to the
387 my ( $self, $c ) = @_;
389 $c->stash->{template} = 'hello.tt';
392 This time, instead of doing C<$c-E<gt>response-E<gt>body()>, you are
393 setting the value of the "template" hash key in the Catalyst "stash",
394 an area for putting information to share with other parts of your
395 application. The "template" key determines which template will be
396 displayed at the end of the request cycle. Catalyst controllers have a
397 default "end" action for all methods which causes the first (or
398 default) view to be rendered (unless there's a C<$c-E<gt>response-
399 E<gt>body()> statement). So your template will be magically displayed
400 at the end of your method.
402 After saving the file, restart the development server, and look at
403 L<http://localhost:3000/hello> again. You should
404 see the template that you just made.
407 =head1 CREATE A SIMPLE CONTROLLER AND AN ACTION
409 Create a controller named "Site" by executing the create script:
411 $ script/hello_create.pl controller Site
413 This will create a C<lib/Hello/Controller/Site.pm> file (and a test
414 file). Bring Site.pm up in your editor, and you can see that there's
417 In C<lib/Hello/Controller/Site.pm>, add the following method:
420 my ( $self, $c ) = @_;
422 $c->stash->{username} = "John";
423 $c->stash->{template} = 'site/test.tt';
426 Notice the "Local" attribute on the C<test> method. This will cause
427 the C<test> action (now that we have assigned an "action type" to the
428 method it appears as a "controller action" to Catalyst) to be executed
429 on the "controller/method" URL, or, in this case, "site/test". We
430 will see additional information on controller actions throughout the
431 rest of the tutorial, but if you are curious take a look at
432 L<Catalyst::Manual::Intro/Actions>.
434 It's not actually necessary to set the template value as we do here.
435 By default TT will attempt to render a template that follows the
436 naming pattern "controller/method.tt", and we're following that
437 pattern here. However, in other situations you will need to specify
438 the template (such as if you've "forwarded" to the method, or if it
439 doesn't follow the default naming convention).
441 We've also put the variable "username" into the stash, for use in the
444 Make a subdirectory "site" in the "root" directory. Copy the hello.tt
445 file into the directory as C<root/site/test.tt>, or create a new
446 template file at that location. Include a line like:
448 <p>Hello, [% username %]!</p>
450 Bring up or restart the server. Notice in the server output that
451 C</site/test> is listed in the Loaded Path actions. Go to
452 L<http://localhost:3000/site/test> in your browser.
454 You should see your test.tt file displayed, including the name "John"
455 that you set in the controller.
460 Gerda Shank, C<gerda.shank@gmail.com>
461 Kennedy Clark, C<hkclark@gmail.com>
463 Please report any errors, issues or suggestions to the author. The
464 most recent version of the Catalyst Tutorial can be found at
465 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
467 Copyright 2006-2008, Kennedy Clark & Gerda Shank, under Creative Commons License
468 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).