3 Catalyst::Manual::Tutorial::MoreCatalystBasics - Catalyst Tutorial - Part 3: More Catalyst Application Development Basics
8 This is B<Part 3 of 10> for the Catalyst tutorial.
10 L<Tutorial Overview|Catalyst::Manual::Tutorial>
16 L<Introduction|Catalyst::Manual::Tutorial::Intro>
20 L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics>
24 B<More Catalyst Basics>
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 This part of the tutorial builds on the work done in Part 2 to explore
60 some features that are more typical of "real world" web applications.
61 From this part of the tutorial onward, we will be building a simple
62 book database application. Although the application will be too
63 limited to be of use to anyone, it should provide a basic environment
64 where we can explore a variety of features used in virtually all web
67 You can checkout the source code for this example from the catalyst
68 subversion repository as per the instructions in
69 L<Catalyst::Manual::Tutorial::Intro>
72 =head1 CREATE A NEW APPLICATION
74 The remainder of the tutorial will build an application call C<MyApp>.
75 Use the Catalyst C<catalyst.pl> script to initialize the framework for
76 an application called C<MyApp> (make sure you aren't still inside the
77 directory of the C<Hello> application from the previous part of the
82 created "MyApp/script"
86 created "MyApp/script/myapp_create.pl"
89 This creates a similar skeletal structure to what we saw in Part 2 of
90 the tutorial, except with C<MyApp> or C<myapp> substituted for
91 C<Hello> and C<hello>.
94 =head1 EDIT THE LIST OF CATALYST PLUGINS
96 One of the greatest benefits of Catalyst is that it has such a large
97 library of plugins available. Plugins are used to seamlessly integrate
98 existing Perl modules into the overall Catalyst framework. In general,
99 they do this by adding additional methods to the C<context> object
100 (generally written as C<$c>) that Catalyst passes to every component
101 throughout the framework.
103 By default, Catalyst enables three plugins/flags:
111 Enables the Catalyst debug output you saw when we started the
112 C<script/myapp_server.pl> development server earlier. You can remove
113 this plugin when you place your application into production.
115 As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
116 Although most of the items specified on the C<use Catalyst> line of your
117 application class will be plugins, Catalyst supports a limited number of
118 flag options (of these, C<-Debug> is the most common). See the
119 documentation for C<Catalyst.pm> to get details on other flags
120 (currently C<-Engine>, C<-Home>, and C<-Log>).
122 If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
125 B<TIP>: Depending on your needs, it can be helpful to permanently
126 remove C<-Debug> from C<lib/MyApp.pm> and then use the C<-d> option
127 to C<script/myapp_server.pl> to re-enable it just for the development
128 server. We will not be using that approach in the tutorial, but feel
129 free to make use of it in your own projects.
133 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
135 C<ConfigLoader> provides an automatic way to load configurable
136 parameters for your application from a central
137 L<Config::General|Config::General> file (versus having the values
138 hard-coded inside your Perl modules). Config::General uses syntax
139 very similar to Apache configuration files. We will see how to use
140 this feature of Catalyst during the authentication and authorization
141 sections (Part 5 and Part 6).
143 B<IMPORTANT NOTE>: If you are following along in Ubuntu 8.04 or
144 otherwise using a version of Catalyst prior to v5.7014, you need to be
145 aware that Catalyst changed from a default format of YAML to the more
146 straightforward C<Config::General> format. Because Catalyst has long
147 supported both formats, this tutorial will simply use a configuration
148 file called C<myapp.conf> instead of C<myapp.yml> and Catatlyst will
149 automcatically use the new format. Just be aware that earlier versions
150 of Catalyst will still create the C<myapp.yml> file and that you will
151 need to B<remove C<myapp.yml>> and create a new C<myapp.conf> file by
152 hand, but otherwise this transition is very painless. The default
153 contents of C<myapp.conf> should only consist of one line: C<name
154 MyApp>. Also be aware that you can continue to use any format
156 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
157 L<Config::Any|Config::Any>, including YAML -- Catalyst will
158 automatically look for any of the supported configuration file formats.
160 C<TIP>: This script can be useful for converting between configuration
163 perl -Ilib -e 'use MyApp; use Config::General;
164 Config::General->new->save_file("myapp.conf", MyApp->config);'
169 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
171 C<Static::Simple> provides an easy method of serving static content such
172 as images and CSS files under the development server.
176 To modify the list of plugins, edit C<lib/MyApp.pm> (this file is
177 generally referred to as your I<application class>) and delete the line
180 use Catalyst qw/-Debug ConfigLoader Static::Simple/;
192 This tells Catalyst to start using one new plugin:
198 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>
200 Adds a stack trace to the standard Catalyst "debug screen" (this is the
201 screen Catalyst sends to your browser when an error occurs).
203 Note: L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
204 browser, not in the console window from which you're running your
205 application, which is where logging output usually goes.
209 Note that when specifying plugins on the C<use Catalyst> line, you can
210 omit C<Catalyst::Plugin::> from the name. Additionally, you can spread
211 the plugin names across multiple lines as shown here, or place them all
212 on one (or more) lines as with the default configuration.
215 =head1 CREATE A CATALYST CONTROLLER
217 As discussed earlier, controllers are where you write methods that
218 interact with user input. Typically, controller methods respond to
219 C<GET> and C<POST> messages from the user's web browser.
221 Use the Catalyst C<create> script to add a controller for book-related
224 $ script/myapp_create.pl controller Books
225 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
226 exists "/home/me/MyApp/script/../t"
227 created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm"
228 created "/home/me/MyApp/script/../t/controller_Books.t"
230 Then edit C<lib/MyApp/Controller/Books.pm> and add the following method
235 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
240 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
241 # 'Context' that's used to 'glue together' the various components
242 # that make up the application
245 # Retrieve all of the book records as book model objects and store in the
246 # stash where they can be accessed by the TT template
247 $c->stash->{books} = [$c->model('MyAppDB::Books')->all];
249 # Set the TT template to use. You will almost always want to do this
250 # in your action methods (action methods respond to user input in
252 $c->stash->{template} = 'books/list.tt2';
255 B<Note:> This won't actually work yet since you haven't set up your
258 B<Note:> Programmers experienced with object-oriented Perl should
259 recognize C<$self> as a reference to the object where this method was
260 called. On the other hand, C<$c> will be new to many Perl programmers
261 who have not used Catalyst before (it's sometimes written as
262 C<$context>). The Context object is automatically passed to all
263 Catalyst components. It is used to pass information between
264 components and provide access to Catalyst and plugin functionality.
266 B<TIP>: You may see the C<$c-E<gt>model('MyAppDB::Book')> used above
267 written as C<$c-E<gt>model('MyAppDB')-E<gt>resultset('Book)>. The two
270 B<Note:> Catalyst actions are regular Perl methods, but they make use
271 of Nicholas Clark's C<attributes> module (that's the C<: Local> next
272 to the C<sub list> in the code above) to provide additional
273 information to the Catalyst dispatcher logic. Many newer Catalyst
274 applications are switching to the use of "Literal" C<: Path> actions
275 and C<Args> attribute in lieu of C<: Local> and C<: Private>. For
276 example, C<sub any_method : Path Args(0)> can be used instead of
277 C<sub index :Private> (because no path was supplied to C<Path> it
278 matches the "empty" URL in the namespace of that module... the same
279 thing C<sub index> would do) or C<sub list : Path('list') Args(0)>
280 could be used instead of the C<sub list : Local> above (the C<list>
281 argument to C<Path> would make it match on the URL C<list> under
282 C<books>, the namespace of the current module). See "Action Types" in
283 L<Catalyst::Manual::Intro|Catalyst::Manual::Intro> as well as Part 5
284 of this tutorial (Authentication) for additional information. Another
285 popular but more advanced feature is C<Chained> actions that allow a
286 single URL to "chain together" multiple action method calls, each with
287 an appropriate number of arguments (see
288 L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
292 =head1 CATALYST VIEWS
294 As mentioned in Part 2 of the tutorial, views are where you render
295 output, typically for display in the user's web browser, but also
296 possibly using other display output- generation systems. As with
297 virtually every aspect of Catalyst, options abound when it comes to
298 the specific view technology you adopt inside your application.
299 However, most Catalyst applications use the Template Toolkit, known as
300 TT (for more information on TT, see L<http://www.template-
301 toolkit.org>). Other popular view technologies include Mason
302 (L<http://www.masonhq.com> and L<http://www.masonbook.com>) and
303 L<HTML::Template|HTML::Template> (L<http://html-
304 template.sourceforge.net>).
306 =head2 Create a Catalyst View Using C<TTSite>
308 When using TT for the Catalyst view, there are two main helper scripts:
314 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
318 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
322 Both are similar, but C<TT> merely creates the C<lib/MyApp/View/TT.pm>
323 file and leaves the creation of any hierarchical template organization
324 entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
325 test cases will be discussed in Part 8). The C<TTSite> helper creates a
326 modular and hierarchical view layout with separate Template Toolkit (TT)
327 files for common header and footer information, configuration values, a
328 CSS stylesheet, and more.
330 While TTSite is useful to bootstrap a project, we recommend that
331 unless you know what you're doing or want to pretty much use the
332 supplied templates as is, that you use the plain Template Toolkit view
333 when starting a project from scratch. This is because TTSite can be
334 tricky to customize. Additionally TT contains constructs that you
335 need to learn yourself if you're going to be a serious user of TT.
336 Our experience suggests that you're better off learning these from
337 scratch. We use TTSite here precisely because it is useful for
338 bootstrap/prototype purposes.
340 Enter the following command to enable the C<TTSite> style of view
341 rendering for this tutorial:
343 $ script/myapp_create.pl view TT TTSite
344 exists "/home/me/MyApp/script/../lib/MyApp/View"
345 exists "/home/me/MyApp/script/../t"
346 created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm"
347 created "/home/me/MyApp/script/../root/lib"
349 created "/home/me/MyApp/script/../root/src/ttsite.css"
351 This puts a number of files in the C<root/lib> and C<root/src>
352 directories that can be used to customize the look and feel of your
353 application. Also take a look at C<lib/MyApp/View/TT.pm> for config
354 values set by the C<TTSite> helper.
356 B<TIP>: Note that TTSite does one thing that could confuse people who
357 are used to the normal C<TT> Catalyst view: it redefines the Catalyst
358 context object in templates from its usual C<c> to C<Catalyst>. When
359 looking at other Catalyst examples, remember that they almost always use
360 C<c>. Note that Catalyst and TT I<do not complain> when you use the
361 wrong name to access the context object...TT simply outputs blanks for
362 that bogus logic (see next tip to change this behavior with TT C<DEBUG>
363 options). Finally, be aware that this change in name I<only>
364 applies to how the context object is accessed inside your TT templates;
365 your controllers will continue to use C<$c> (or whatever name you use
366 when fetching the reference from C<@_> inside your methods). (You can
367 change back to the "default" behavior be removing the C<CATALYST_VAR>
368 line from C<lib/MyApp/View/TT.pm>, but you will also have to edit
369 C<root/lib/config/main> and C<root/lib/config/url>. If you do this, be
370 careful not to have a collision between your own C<c> variable and the
371 Catalyst C<c> variable.)
373 B<TIP>: When troubleshooting TT it can be helpful to enable variable
374 C<DEBUG> options. You can do this in a Catalyst environment by adding
375 a C<DEBUG> line to the C<__PACKAGE__->config> declaration in
376 C<lib/MyApp/View/TT.pm>:
378 __PACKAGE__->config({
379 CATALYST_VAR => 'Catalyst',
385 B<Note:> C<__PACKAGE__> is just a shorthand way of referencing the name
386 of the package where it is used. Therefore, in C<TT.pm>,
387 C<__PACKAGE__> is equivalent to C<TT>.
389 There are a variety of options you can use, such as 'undef', 'all',
390 'service', 'context', 'parser', 'provider', and 'service'. See
391 L<Template::Constants> for more information (remove the C<DEBUG_>
392 portion of the name shown in the TT docs and convert to lower case
393 for use inside Catalyst).
395 B<NOTE:> B<Please be sure to disable TT debug options before
396 continuing the tutorial> (especially the 'undef' option -- leaving
397 this enabled will conflict with several of the conventions used
398 by this tutorial and TTSite to leave some variables undefined
402 =head2 Globally Customize Every View
404 When using TTSite, files in the subdirectories of C<root/lib> can be
405 used to make changes that will appear in every view. For example, to
406 display optional status and error messages in every view, edit
407 C<root/lib/site/layout>, updating it to match the following (the two HTML
408 C<span> elements are new):
410 <div id="header">[% PROCESS site/header %]</div>
413 <span class="message">[% status_msg %]</span>
414 <span class="error">[% error_msg %]</span>
418 <div id="footer">[% PROCESS site/footer %]</div>
420 If we set either message in the Catalyst stash (e.g.,
421 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it will
422 be displayed whenever any view used by that request is rendered. The
423 C<message> and C<error> CSS styles are automatically defined in
424 C<root/src/ttsite.css> and can be customized to suit your needs.
426 B<Note:> The Catalyst stash only lasts for a single HTTP request. If
427 you need to retain information across requests you can use
428 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
429 Catalyst sessions in the Authentication part of the tutorial).
432 =head2 Create a TT Template Page
434 To add a new page of content to the TTSite view hierarchy, just create a
435 new C<.tt2> file in C<root/src>. Only include HTML markup that goes
436 inside the HTML <body> and </body> tags, TTSite will use the contents of
437 C<root/lib/site> to add the top and bottom.
439 First create a directory for book-related TT templates:
441 $ mkdir root/src/books
443 Then create C<root/src/books/list.tt2> in your editor and enter:
445 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
446 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
447 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
448 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
450 [% # Provide a title to root/lib/site/header -%]
451 [% META title = 'Book List' -%]
454 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
455 [% # Display each book in a table row %]
456 [% FOREACH book IN books -%]
458 <td>[% book.title %]</td>
459 <td>[% book.rating %]</td>
464 As indicated by the inline comments above, the C<META title> line uses
465 TT's META feature to provide a title to C<root/lib/site/header>.
466 Meanwhile, the outer C<FOREACH> loop iterates through each C<book> model
467 object and prints the C<title> and C<rating> fields. An inner
468 C<FOREACH> loop prints the last name of each author in a comma-separated
469 list within a single table cell.
471 If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT
472 code. TT supports a wide variety of directives for "calling" other
473 files, looping, conditional logic, etc. In general, TT simplifies the
474 usual range of Perl operators down to the single dot (C<.>) operator.
475 This applies to operations as diverse as method calls, hash lookups, and
476 list index values (see
477 L<http://www.template-toolkit.org/docs/default/Manual/Variables.html>
478 for details and examples). In addition to the usual C<Template> module
479 Pod documentation, you can access the TT manual at
480 L<http://www.template-toolkit.org/docs/default/>.
482 B<NOTE>: The C<TTSite> helper creates several TT files using an
483 extension of C<.tt2>. Most other Catalyst and TT examples use an
484 extension of C<.tt>. You can use either extension (or no extension at
485 all) with TTSite and TT, just be sure to use the appropriate extension
486 for both the file itself I<and> the C<$c-E<gt>stash-E<gt>{template} =
487 ...> line in your controller. This document will use C<.tt2> for
488 consistency with the files already created by the C<TTSite> helper.
491 =head1 CREATE A SQLITE DATABASE
493 In this step, we make a text file with the required SQL commands to
494 create a database table and load some sample data. Open C<myapp01.sql>
495 in your editor and enter:
498 -- Create a very simple database to hold book and author information
501 id INTEGER PRIMARY KEY,
505 -- 'book_authors' is a many-to-many join table between books & authors
506 CREATE TABLE book_authors (
509 PRIMARY KEY (book_id, author_id)
511 CREATE TABLE authors (
512 id INTEGER PRIMARY KEY,
517 --- Load some sample data
519 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
520 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
521 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
522 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
523 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
524 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
525 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
526 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
527 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
528 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
529 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
530 INSERT INTO authors VALUES (7, 'Nathan', 'Torkington');
531 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
532 INSERT INTO book_authors VALUES (1, 1);
533 INSERT INTO book_authors VALUES (1, 2);
534 INSERT INTO book_authors VALUES (1, 3);
535 INSERT INTO book_authors VALUES (2, 4);
536 INSERT INTO book_authors VALUES (3, 5);
537 INSERT INTO book_authors VALUES (4, 6);
538 INSERT INTO book_authors VALUES (4, 7);
539 INSERT INTO book_authors VALUES (5, 8);
541 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
542 cutting and pasting example code from POD-based documents.
544 Then use the following command to build a C<myapp.db> SQLite database:
546 $ sqlite3 myapp.db < myapp01.sql
548 If you need to create the database more than once, you probably want to
549 issue the C<rm myapp.db> command to delete the database before you use
550 the C<sqlite3 myapp.db < myapp01.sql> command.
552 Once the C<myapp.db> database file has been created and initialized, you
553 can use the SQLite command line environment to do a quick dump of the
558 Enter ".help" for instructions
559 sqlite> select * from books;
560 1|CCSP SNRS Exam Certification Guide|5
561 2|TCP/IP Illustrated, Volume 1|5
562 3|Internetworking with TCP/IP Vol.1|4
564 5|Designing with Web Standards|5
570 $ sqlite3 myapp.db "select * from books"
571 1|CCSP SNRS Exam Certification Guide|5
572 2|TCP/IP Illustrated, Volume 1|5
573 3|Internetworking with TCP/IP Vol.1|4
575 5|Designing with Web Standards|5
577 As with most other SQL tools, if you are using the full "interactive"
578 environment you need to terminate your SQL commands with a ";" (it's not
579 required if you do a single SQL statement on the command line). Use
580 ".q" to exit from SQLite from the SQLite interactive mode and return to
581 your OS command prompt.
584 =head1 DATABASE ACCESS WITH C<DBIx::Class>
586 Catalyst can be used with virtually any form of persistent datastore
587 available via Perl. For example,
588 L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to
589 easily access databases through the traditional Perl C<DBI> interface.
590 However, most Catalyst applications use some form of ORM technology to
591 automatically create and save model objects as they are used. Although
592 Tony Bowden's L<Class::DBI|Class::DBI> has been a popular choice
593 in the past, Matt Trout's L<DBIx::Class|DBIx::Class> (abbreviated
594 as "DBIC") has rapidly emerged as the Perl-based ORM technology of choice.
595 Most new Catalyst applications rely on DBIC, as will this tutorial.
597 =head2 Create a dynamic DBIC Model
599 Use the C<create=dynamic> model helper option to build a model that
600 dynamically reads your database structure every time the application
603 $ script/myapp_create.pl model MyAppDB DBIC::Schema MyApp::Schema::MyAppDB create=dynamic dbi:SQLite:myapp.db
604 exists "/home/me/MyApp/script/../lib/MyApp/Model"
605 exists "/home/me/MyApp/script/../t"
606 created "/home/me/MyApp/script/../lib/MyApp/Schema"
607 created "/home/me/MyApp/script/../lib/MyApp/Schema/MyAppDB.pm"
608 created "/home/me/MyApp/script/../lib/MyApp/Model/MyAppDB.pm"
609 created "/home/me/MyApp/script/../t/model_MyAppDB.t"
612 C<MyAppDB> is the name of the model class to be created by the helper in
613 C<lib/MyApp/Model> (Catalyst has a separate directory under C<lib/MyApp>
614 for each of the three parts of MVC: C<Model>, C<View>, and C<Controller>
615 [although older Catalyst applications often use the directories C<M>,
616 C<V>, and C<C>]). C<DBIC::Schema> is the type of the model to create.
617 C<MyApp::Schema::MyAppDB> is the name of the DBIC schema file written to
618 C<lib/MyApp/Schema/MyAppDB.pm>. Because we specified C<create=dynamic>
619 to the helper, it use L<DBIx::Class::Schema::Loader> to dynamically load
620 the schema information from the database every time the application
621 starts. And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect
622 string for use with SQLite.
624 =head1 RUN THE APPLICATION
626 First, let's enable an environment variable option that causes
627 DBIx::Class to dump the SQL statements it's using to access the database
628 (this option can provide extremely helpful troubleshooting information):
630 $ export DBIC_TRACE=1
632 This assumes you are using BASH as your shell -- adjust accordingly if
633 you are using a different shell (for example, under tcsh, use
634 C<setenv DBIC_TRACE 1>).
636 B<NOTE>: You can also set this in your code using
637 C<$class-E<gt>storage-E<gt>debug(1);>. See
638 L<DBIx::Class::Manual::Troubleshooting> for details (including options
639 to log to file instead of displaying to the Catalyst development server
642 Then run the Catalyst "demo server" script:
644 $ script/myapp_server.pl
646 Your development server log output should display something like:
648 $script/myapp_server.pl
649 [debug] Debug messages enabled
650 [debug] Loaded plugins:
651 .----------------------------------------------------------------------------.
652 | Catalyst::Plugin::ConfigLoader 0.17 |
653 | Catalyst::Plugin::StackTrace 0.06 |
654 | Catalyst::Plugin::Static::Simple 0.20 |
655 '----------------------------------------------------------------------------'
657 [debug] Loaded dispatcher "Catalyst::Dispatcher"
658 [debug] Loaded engine "Catalyst::Engine::HTTP"
659 [debug] Found home "/home/me/MyApp"
660 [debug] Loaded Config "/home/me/MyApp/myapp.yml"
661 [debug] Loaded components:
662 .-----------------------------------------------------------------+----------.
664 +-----------------------------------------------------------------+----------+
665 | MyApp::Controller::Books | instance |
666 | MyApp::Controller::Root | instance |
667 | MyApp::Model::MyAppDB | instance |
668 | MyApp::Model::MyAppDB::Authors | class |
669 | MyApp::Model::MyAppDB::BookAuthors | class |
670 | MyApp::Model::MyAppDB::Books | class |
671 | MyApp::View::TT | instance |
672 '-----------------------------------------------------------------+----------'
674 [debug] Loaded Private actions:
675 .----------------------+--------------------------------------+--------------.
676 | Private | Class | Method |
677 +----------------------+--------------------------------------+--------------+
678 | /default | MyApp::Controller::Root | default |
679 | /end | MyApp::Controller::Root | end |
680 | /books/index | MyApp::Controller::Books | index |
681 | /books/list | MyApp::Controller::Books | list |
682 '----------------------+--------------------------------------+--------------'
684 [debug] Loaded Path actions:
685 .-------------------------------------+--------------------------------------.
687 +-------------------------------------+--------------------------------------+
688 | /books/list | /books/list |
689 '-------------------------------------+--------------------------------------'
691 [info] MyApp powered by Catalyst 5.7011
692 You can connect to your server at http://localhost:3000
694 B<NOTE>: Be sure you run the C<script/myapp_server.pl> command from
695 the 'base' directory of your application, not inside the C<script>
696 directory itself or it will not be able to locate the C<myapp.db>
697 database file. You can use a fully qualified or a relative path to
698 locate the database file, but we did not specify that when we ran the
699 model helper earlier.
701 Some things you should note in the output above:
707 Catalyst::Model::DBIC::Schema dynamically created three model classes,
708 one to represent each of the three tables in our database
709 (C<MyApp::Model::MyAppDB::Authors>, C<MyApp::Model::MyAppDB::BookAuthors>,
710 and C<MyApp::Model::MyAppDB::Books>).
714 The "list" action in our Books controller showed up with a path of
719 Point your browser to L<http://localhost:3000> and you should still get
720 the Catalyst welcome page.
722 Next, to view the book list, change the URL in your browser to
723 L<http://localhost:3000/books/list>. You should get a list of the five
724 books loaded by the C<myapp01.sql> script above, with TTSite providing
725 the formatting for the very simple output we generated in our template.
726 The rating for each book should appear on each row.
728 Also notice in the output of the C<script/myapp_server.pl> that DBIC
729 used the following SQL to retrieve the data:
731 SELECT me.id, me.title, me.rating FROM books me
733 because we enabled DBIC_TRACE.
735 You now the beginnings of a simple but workable web application.
736 Continue on to future sections and we will develop the application
740 =head1 A STATIC DATABASE MODEL WITH C<DBIx::Class>
742 =head2 Create Static DBIC Schema Files
744 Unlike the previous section where we had DBIC automatically discover the
745 structure of the database every time the application started, here we
746 will use static schema files for more control. This is typical of most
747 "real world" applications.
749 One option would be to create a separate schema file for each table in
750 the database, however, lets use the same L<DBIx::Class::Schema::Loader>
751 used earlier with C<create=dynamic> to build the static files for us.
752 First, lets remove the schema file created in Part 2:
754 $ rm lib/MyApp/Schema/MyAppDB.pm
756 Now regenerate the schema using the C<create=static> option:
758 $ script/myapp_create.pl model MyAppDB DBIC::Schema MyApp::Schema::MyAppDB create=static dbi:SQLite:myapp.db
759 exists "/home/me/MyApp/script/../lib/MyApp/Model"
760 exists "/home/me/MyApp/script/../t"
761 Dumping manual schema for MyApp::Schema::MyAppDB to directory /home/me/MyApp/script/../lib ...
762 Schema dump completed.
763 exists "/home/me/MyApp/script/../lib/MyApp/Model/MyAppDB.pm"
765 We could have also deleted C<lib/MyApp/Model/MyAppDB.pm>, but it would
766 have regenerated the same file (note the C<exists> in the output above).
767 If you take a look at C<lib/MyApp/Model/MyAppDB.pm>, it simply contains
768 a reference to the actual schema file in C<lib/MyApp/Schema/MyAppDB.pm>
769 along with the database connect string.
771 If you look in the C<lib/MyApp/Schema> directory, you will find that
772 C<MyAppDB.pm> is no longer using L<DBIx::Class::Schema::Loader> as its
773 base class (L<DBIx::Class::Schema::Loader> is only being used by the
774 helper to load the schema once and then create the static files for us)
775 and that it only contains a call to the C<load_classes> method. You
776 will also find that C<lib/MyApp/Schema> contains a C<MyAppDB>
777 subdirectory, with one file inside this directory for each of the tables
778 in our simple database (C<Authors.pm>, C<BookAuthors.pm>, and
779 C<Books.pm>). These three files were created based on the information
780 found by L<DBIx::Class::Schema::Loader> as the helper ran.
782 The idea with all of the files created under C<lib/MyApp/Schema> by the
783 C<create=static> option is to only edit the files below the C<# DO NOT
784 MODIFY THIS OR ANYTHING ABOVE!> warning. If you place all of your
785 changes below that point in the file, you can regenerate the
786 auto-generated information at the top of each file should your database
787 structure get updated.
789 Also note the "flow" of the model information across the various files
790 and directories. Catalyst will initially load the model from
791 C<lib/MyApp/Model/MyAppDB.pm>. This file contains a reference to
792 C<lib/MyApp/Schema/MyAppDB.pm>, so that file is loaded next. Finally,
793 the call to C<load_classes> in that file will load each of the
794 table-specific "results source" files from the C<lib/MyApp/Schema/MyAppDB>
795 subdirectory. These three table-specific DBIC schema files will then be
796 used to create three table-specific Catalyst models every time the
797 application starts (you can see these three model files listed in
798 the debug output generated when you launch the application).
801 =head2 Updating the Generated DBIC Schema Files
804 Let's manually add some relationship information to the auto-generated
805 schema files. First edit C<lib/MyApp/Schema/MyAppDB/Books.pm> and
806 add the following text below the C<# You can replace this text...>
815 # 1) Name of relationship, DBIC will create accessor with this name
816 # 2) Name of the model class referenced by this relationship
817 # 3) Column name in *foreign* table
818 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::MyAppDB::BookAuthors', 'book_id');
822 # 1) Name of relationship, DBIC will create accessor with this name
823 # 2) Name of has_many() relationship this many_to_many() is shortcut for
824 # 3) Name of belongs_to() relationship in model class of has_many() above
825 # You must already have the has_many() defined to use a many_to_many().
826 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
829 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
830 file. As with any Perl package, we need to end the last line with
831 a statement that evaluates to C<true>. This is customarily done with
832 C<1;> on a line by itself.
834 This code defines both a C<has_many> and a C<many_to_many> relationship.
835 The C<many_to_many> relationship is optional, but it makes it easier to
836 map a book to its collection of authors. Without it, we would have to
837 "walk" though the C<book_authors> table as in C<$book-E<gt>book_authors-
838 E<gt>first-E<gt>author-E<gt>last_name> (we will see examples on how to
839 use DBIC objects in your code soon, but note that because C<$book-
840 E<gt>book_authors> can return multiple authors, we have to use C<first>
841 to display a single author). C<many_to_many> allows us to use the
842 shorter C<$book-E<gt>authors-E<gt>first-E<gt>last_name>. Note that you
843 cannot define a C<many_to_many> relationship without also having the
844 C<has_many> relationship in place.
846 Then edit C<lib/MyApp/Schema/MyAppDB/Authors.pm> and add relationship
847 information as follows (again, be careful to put in above the C<1;> but
848 below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
856 # 1) Name of relationship, DBIC will create accessor with this name
857 # 2) Name of the model class referenced by this relationship
858 # 3) Column name in *foreign* table
859 __PACKAGE__->has_many(book_author => 'MyApp::Schema::MyAppDB::BookAuthors', 'author_id');
863 # 1) Name of relationship, DBIC will create accessor with this name
864 # 2) Name of has_many() relationship this many_to_many() is shortcut for
865 # 3) Name of belongs_to() relationship in model class of has_many() above
866 # You must already have the has_many() defined to use a many_to_many().
867 __PACKAGE__->many_to_many(books => 'book_author', 'book');
869 Finally, do the same for the "join table,"
870 C<lib/MyApp/Schema/MyAppDB/BookAuthors.pm>:
878 # 1) Name of relationship, DBIC will create accessor with this name
879 # 2) Name of the model class referenced by this relationship
880 # 3) Column name in *this* table
881 __PACKAGE__->belongs_to(book => 'MyApp::Schema::MyAppDB::Books', 'book_id');
885 # 1) Name of relationship, DBIC will create accessor with this name
886 # 2) Name of the model class referenced by this relationship
887 # 3) Column name in *this* table
888 __PACKAGE__->belongs_to(author => 'MyApp::Schema::MyAppDB::Authors', 'author_id');
891 =head1 RUN THE APPLICATION
893 Run the Catalyst "demo server" script with the C<DBIC_TRACE> option
894 (it might still be enabled from earlier in the tutorial, but here
895 is an alternate way to specify the option just in case):
897 $ DBIC_TRACE=1 script/myapp_server.pl
899 Make sure that the application loads correctly and that you see the
900 three dynamically created model class (one for each of the
901 table-specific schema classes we created).
903 Then hit the URL L<http://localhost:3000/books/list> and be sure that
904 the book list is displayed.
907 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
909 In some situations, it can be useful to run your application and
910 display a page without using a browser. Catalyst lets you do this
911 using the C<scripts/myapp_test.pl> script. Just supply the URL you
912 wish to display and it will run that request through the normal
913 controller dispatch logic and use the appropriate view to render the
914 output (obviously, complex pages may dump a lot of text to your
915 terminal window). For example, if you type:
917 $ script/myapp_test.pl "/books/list"
919 You should get the same text as if you visited
920 L<http://localhost:3000/books/list> with the normal development server
921 and asked your browser to view the page source.
924 =head1 UPDATING THE VIEW
926 Let's add a new column to our book list page that takes advantage of
927 the relationship information we manually added to our schema files
928 in the previous section. Edit C<root/src/books/list.tt2> add add the
929 following code below the existing table cell that contains
930 C<book.rating> (IOW, add a new table cell below the existing two
934 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
935 [% # loop in 'side effect notation' to load just the last names of the -%]
936 [% # authors into the list. Note that the 'push' TT vmethod does not -%]
937 [% # a value, so nothing will be printed here. But, if you have something -%]
938 [% # in TT that does return a method and you don't want it printed, you -%]
939 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
940 [% # call it and discard the return value. -%]
942 tt_authors.push(author.last_name) FOREACH author = book.authors %]
943 [% # Now use a TT 'virtual method' to display the author count in parens -%]
944 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
945 ([% tt_authors.size | html %])
946 [% # Use another TT vmethod to join & print the names & comma separators -%]
947 [% tt_authors.join(', ') | html %]
950 Then hit C<Ctrl+R> in your browser (not that you don't need to reload
951 the development server or use the C<-r> option when updating TT
952 templates) and you should now the the number of authors each book and
953 a comma-separated list of the author's last names.
955 If you are still running the development server with C<DBIC_TRACE>
956 enabled, you should also now see five more C<SELECT> statements in the
957 debug output (one for each book as the authors are being retrieved by
960 Also note that we are using "| html", a type of TT filter, to escape
961 characters such as E<lt> and E<gt> to < and > and avoid various
962 types of dangerous hacks against your application. In a real
963 application, you would probably want to put "| html" at the end of
964 every field where a user has control over the information that can
965 appear in that field (and can therefore inject markup or code if you
966 don't "neutralize" those fields). In addition to "| html", Template
967 Toolkit has a variety of other useful filters that can found in the
968 documentation for L<Template::Filters|Template::Filters>.
971 =head2 Using C<RenderView> for the Default View
973 B<NOTE: The rest of this part of the tutorial is optional. You can
974 skip to Part 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
977 Once your controller logic has processed the request from a user, it
978 forwards processing to your view in order to generate the appropriate
979 response output. Catalyst uses
980 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
981 default to automatically performs this operation. If you look in
982 C<lib/MyApp/Controller/Root.pm>, you should see the empty
983 definition for the C<sub end> method:
985 sub end : ActionClass('RenderView') {}
987 The following bullet points provide a quick overview of the
988 C<RenderView> process:
994 C<Root.pm> is designed to hold application-wide logic.
998 At the end of a given user request, Catalyst will call the most specific
999 C<end> method that's appropriate. For example, if the controller for a
1000 request has an C<end> method defined, it will be called. However, if
1001 the controller does not define a controller-specific C<end> method, the
1002 "global" C<end> method in C<Root.pm> will be called.
1006 Because the definition includes an C<ActionClass> attribute, the
1007 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1008 will be executed B<after> any code inside the definition of C<sub end>
1009 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1010 for more information on C<ActionClass>.
1014 Because C<sub end> is empty, this effectively just runs the default
1015 logic in C<RenderView>. However, you can easily extend the
1016 C<RenderView> logic by adding your own code inside the empty method body
1017 (C<{}>) created by the Catalyst Helpers when we first ran the
1018 C<catalyst.pl> to initialize our application. See
1019 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1020 detailed information on how to extended C<RenderView> in C<sub end>.
1025 =head2 Using The Default Template Name
1027 By default, C<Catalyst::View::TT> will look for a template that uses the
1028 same name as your controller action, allowing you to save the step of
1029 manually specifying the template name in each action. For example, this
1030 would allow us to remove the
1031 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1032 C<list> action in the Books controller. Open
1033 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1034 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1039 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1044 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1045 # 'Context' that's used to 'glue together' the various components
1046 # that make up the application
1047 my ($self, $c) = @_;
1049 # Retrieve all of the book records as book model objects and store in the
1050 # stash where they can be accessed by the TT template
1051 $c->stash->{books} = [$c->model('MyAppDB::Books')->all];
1053 # Set the TT template to use. You will almost always want to do this
1054 # in your action methods (actions methods respond to user input in
1055 # your controllers).
1056 #$c->stash->{template} = 'books/list.tt2';
1059 C<Catalyst::View::TT> defaults to looking for a template with no
1060 extension. In our case, we need to override this to look for an
1061 extension of C<.tt2>. Open C<lib/MyApp/View/TT.pm> and add the
1062 C<TEMPLATE_EXTENSION> definition as follows:
1064 __PACKAGE__->config({
1065 CATALYST_VAR => 'Catalyst',
1067 MyApp->path_to( 'root', 'src' ),
1068 MyApp->path_to( 'root', 'lib' )
1070 PRE_PROCESS => 'config/main',
1071 WRAPPER => 'site/wrapper',
1072 ERROR => 'error.tt2',
1074 TEMPLATE_EXTENSION => '.tt2',
1077 You should now be able to restart the development server as per the
1078 previous section and access the L<http://localhost:3000/books/list>
1081 B<NOTE:> Please note that if you use the default template technique,
1082 you will B<not> be able to use either the C<$c-E<gt>forward> or
1083 the C<$c-E<gt>detach> mechanisms (these are discussed in Part 2 and
1084 Part 9 of the Tutorial).
1087 =head2 Return To A Manually-Specified Template
1089 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1090 later in the tutorial, you should remove the comment from the
1091 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1093 $c->stash->{template} = 'books/list.tt2';
1095 Then delete the C<TEMPLATE_EXTENSION> line in
1096 C<lib/MyApp/View/TT.pm>.
1098 You should then be able to restart the development server and
1099 access L<http://localhost:3000/books/list> in the same manner as
1100 with earlier sections.
1105 Kennedy Clark, C<hkclark@gmail.com>
1107 Please report any errors, issues or suggestions to the author. The
1108 most recent version of the Catalyst Tutorial can be found at
1109 L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/Catalyst-Manual/lib/Catalyst/Manual/Tutorial/>.
1111 Copyright 2006, Kennedy Clark, under Creative Commons License
1112 (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).