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 L<Catalyst::Devel|Catalyst::Devel> prior
145 to version 1.06, you need to be aware that Catalyst changed from a
146 default format of YAML to the more straightforward C<Config::General>
147 format. Because Catalyst has long supported both formats, this
148 tutorial will simply use a configuration file called C<myapp.conf>
149 instead of C<myapp.yml> and Catatlyst will automcatically use the new
150 format. Just be aware that earlier versions of Catalyst will still
151 create the C<myapp.yml> file and that you will need to B<remove
152 C<myapp.yml>> and create a new C<myapp.conf> file by hand, but
153 otherwise this transition is very painless. The default contents of
154 C<myapp.conf> should only consist of one line: C<name MyApp>. Also be
155 aware that you can continue to use any format supported by
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
161 B<TIP>: This script can be useful for converting between configuration
164 perl -Ilib -e 'use MyApp; use Config::General;
165 Config::General->new->save_file("myapp.conf", MyApp->config);'
167 B<NOTE:> The default C<myapp.conf> should look like:
173 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
175 C<Static::Simple> provides an easy method of serving static content such
176 as images and CSS files under the development server.
180 To modify the list of plugins, edit C<lib/MyApp.pm> (this file is
181 generally referred to as your I<application class>) and delete the line
184 use Catalyst qw/-Debug ConfigLoader Static::Simple/;
196 This tells Catalyst to start using one new plugin:
202 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>
204 Adds a stack trace to the standard Catalyst "debug screen" (this is the
205 screen Catalyst sends to your browser when an error occurs).
207 Note: L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
208 browser, not in the console window from which you're running your
209 application, which is where logging output usually goes.
213 Note that when specifying plugins on the C<use Catalyst> line, you can
214 omit C<Catalyst::Plugin::> from the name. Additionally, you can spread
215 the plugin names across multiple lines as shown here, or place them all
216 on one (or more) lines as with the default configuration.
219 =head1 CREATE A CATALYST CONTROLLER
221 As discussed earlier, controllers are where you write methods that
222 interact with user input. Typically, controller methods respond to
223 C<GET> and C<POST> messages from the user's web browser.
225 Use the Catalyst C<create> script to add a controller for book-related
228 $ script/myapp_create.pl controller Books
229 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
230 exists "/home/me/MyApp/script/../t"
231 created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm"
232 created "/home/me/MyApp/script/../t/controller_Books.t"
234 Then edit C<lib/MyApp/Controller/Books.pm> and add the following method
239 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
244 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
245 # 'Context' that's used to 'glue together' the various components
246 # that make up the application
249 # Retrieve all of the book records as book model objects and store in the
250 # stash where they can be accessed by the TT template
251 $c->stash->{books} = [$c->model('DB::Books')->all];
253 # Set the TT template to use. You will almost always want to do this
254 # in your action methods (action methods respond to user input in
256 $c->stash->{template} = 'books/list.tt2';
259 B<Note:> This won't actually work yet since you haven't set up your
260 model yet. We will be covering the model soon.
262 B<Note:> Programmers experienced with object-oriented Perl should
263 recognize C<$self> as a reference to the object where this method was
264 called. On the other hand, C<$c> will be new to many Perl programmers
265 who have not used Catalyst before (it's sometimes written as
266 C<$context>). The Context object is automatically passed to all
267 Catalyst components. It is used to pass information between
268 components and provide access to Catalyst and plugin functionality.
270 B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> used above
271 written as C<$c-E<gt>model('DB')-E<gt>resultset('Book)>. The two
274 B<Note:> Catalyst actions are regular Perl methods, but they make use
275 of Nicholas Clark's C<attributes> module (that's the C<: Local> next
276 to the C<sub list> in the code above) to provide additional
277 information to the Catalyst dispatcher logic. Many newer Catalyst
278 applications are switching to the use of "Literal" C<: Path> actions
279 and C<Args> attribute in lieu of C<: Local> and C<: Private>. For
280 example, C<sub any_method : Path Args(0)> can be used instead of
281 C<sub index :Private> (because no path was supplied to C<Path> it
282 matches the "empty" URL in the namespace of that module... the same
283 thing C<sub index> would do) or C<sub list : Path('list') Args(0)>
284 could be used instead of the C<sub list : Local> above (the C<list>
285 argument to C<Path> would make it match on the URL C<list> under
286 C<books>, the namespace of the current module). See "Action Types" in
287 L<Catalyst::Manual::Intro|Catalyst::Manual::Intro> as well as Part 5
288 of this tutorial (Authentication) for additional information. Another
289 popular but more advanced feature is C<Chained> actions that allow a
290 single URL to "chain together" multiple action method calls, each with
291 an appropriate number of arguments (see
292 L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
296 =head1 CATALYST VIEWS
298 As mentioned in Part 2 of the tutorial, views are where you render
299 output, typically for display in the user's web browser, but also
300 possibly using other display output- generation systems. As with
301 virtually every aspect of Catalyst, options abound when it comes to
302 the specific view technology you adopt inside your application.
303 However, most Catalyst applications use the Template Toolkit, known as
304 TT (for more information on TT, see
305 L<http://www.template-toolkit.org>). Other popular view technologies
306 include Mason (L<http://www.masonhq.com> and
307 L<http://www.masonbook.com>) and L<HTML::Template>
308 (L<http://html- template.sourceforge.net>).
310 =head2 Create a Catalyst View Using C<TTSite>
312 When using TT for the Catalyst view, there are two main helper scripts:
318 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
322 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
326 Both are similar, but C<TT> merely creates the C<lib/MyApp/View/TT.pm>
327 file and leaves the creation of any hierarchical template organization
328 entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
329 test cases will be discussed in Part 8). The C<TTSite> helper creates a
330 modular and hierarchical view layout with separate Template Toolkit (TT)
331 files for common header and footer information, configuration values, a
332 CSS stylesheet, and more.
334 While TTSite is useful to bootstrap a project, we recommend that
335 unless you know what you're doing or want to pretty much use the
336 supplied templates as is, that you use the plain Template Toolkit view
337 when starting a project from scratch. This is because TTSite can be
338 tricky to customize. Additionally TT contains constructs that you
339 need to learn yourself if you're going to be a serious user of TT.
340 Our experience suggests that you're better off learning these from
341 scratch. We use TTSite here precisely because it is useful for
342 bootstrap/prototype purposes.
344 Enter the following command to enable the C<TTSite> style of view
345 rendering for this tutorial:
347 $ script/myapp_create.pl view TT TTSite
348 exists "/home/me/MyApp/script/../lib/MyApp/View"
349 exists "/home/me/MyApp/script/../t"
350 created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm"
351 created "/home/me/MyApp/script/../root/lib"
353 created "/home/me/MyApp/script/../root/src/ttsite.css"
355 This puts a number of files in the C<root/lib> and C<root/src>
356 directories that can be used to customize the look and feel of your
357 application. Also take a look at C<lib/MyApp/View/TT.pm> for config
358 values set by the C<TTSite> helper.
360 B<TIP>: Note that TTSite does one thing that could confuse people who
361 are used to the normal C<TT> Catalyst view: it redefines the Catalyst
362 context object in templates from its usual C<c> to C<Catalyst>. When
363 looking at other Catalyst examples, remember that they almost always use
364 C<c>. Note that Catalyst and TT I<do not complain> when you use the
365 wrong name to access the context object...TT simply outputs blanks for
366 that bogus logic (see next tip to change this behavior with TT C<DEBUG>
367 options). Finally, be aware that this change in name I<only>
368 applies to how the context object is accessed inside your TT templates;
369 your controllers will continue to use C<$c> (or whatever name you use
370 when fetching the reference from C<@_> inside your methods). (You can
371 change back to the "default" behavior be removing the C<CATALYST_VAR>
372 line from C<lib/MyApp/View/TT.pm>, but you will also have to edit
373 C<root/lib/config/main> and C<root/lib/config/url>. If you do this, be
374 careful not to have a collision between your own C<c> variable and the
375 Catalyst C<c> variable.)
377 B<TIP>: When troubleshooting TT it can be helpful to enable variable
378 C<DEBUG> options. You can do this in a Catalyst environment by adding
379 a C<DEBUG> line to the C<__PACKAGE__->config> declaration in
380 C<lib/MyApp/View/TT.pm>:
382 __PACKAGE__->config({
383 CATALYST_VAR => 'Catalyst',
389 B<Note:> C<__PACKAGE__> is just a shorthand way of referencing the name
390 of the package where it is used. Therefore, in C<TT.pm>,
391 C<__PACKAGE__> is equivalent to C<TT>.
393 There are a variety of options you can use, such as 'undef', 'all',
394 'service', 'context', 'parser', 'provider', and 'service'. See
395 L<Template::Constants> for more information (remove the C<DEBUG_>
396 portion of the name shown in the TT docs and convert to lower case
397 for use inside Catalyst).
399 B<NOTE:> B<Please be sure to disable TT debug options before
400 continuing the tutorial> (especially the 'undef' option -- leaving
401 this enabled will conflict with several of the conventions used
402 by this tutorial and TTSite to leave some variables undefined
406 =head2 Globally Customize Every View
408 When using TTSite, files in the subdirectories of C<root/lib> can be
409 used to make changes that will appear in every view. For example, to
410 display optional status and error messages in every view, edit
411 C<root/lib/site/layout>, updating it to match the following (the two HTML
412 C<span> elements are new):
414 <div id="header">[% PROCESS site/header %]</div>
417 <span class="message">[% status_msg %]</span>
418 <span class="error">[% error_msg %]</span>
422 <div id="footer">[% PROCESS site/footer %]</div>
424 If we set either message in the Catalyst stash (e.g.,
425 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it will
426 be displayed whenever any view used by that request is rendered. The
427 C<message> and C<error> CSS styles are automatically defined in
428 C<root/src/ttsite.css> and can be customized to suit your needs.
430 B<Note:> The Catalyst stash only lasts for a single HTTP request. If
431 you need to retain information across requests you can use
432 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
433 Catalyst sessions in the Authentication part of the tutorial).
436 =head2 Create a TT Template Page
438 To add a new page of content to the TTSite view hierarchy, just create a
439 new C<.tt2> file in C<root/src>. Only include HTML markup that goes
440 inside the HTML <body> and </body> tags, TTSite will use the contents of
441 C<root/lib/site> to add the top and bottom.
443 First create a directory for book-related TT templates:
445 $ mkdir root/src/books
447 Then create C<root/src/books/list.tt2> in your editor and enter:
449 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
450 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
451 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
452 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
454 [% # Provide a title to root/lib/site/header -%]
455 [% META title = 'Book List' -%]
458 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
459 [% # Display each book in a table row %]
460 [% FOREACH book IN books -%]
462 <td>[% book.title %]</td>
463 <td>[% book.rating %]</td>
468 As indicated by the inline comments above, the C<META title> line uses
469 TT's META feature to provide a title to C<root/lib/site/header>.
470 Meanwhile, the outer C<FOREACH> loop iterates through each C<book> model
471 object and prints the C<title> and C<rating> fields. An inner
472 C<FOREACH> loop prints the last name of each author in a comma-separated
473 list within a single table cell.
475 If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT
476 code. TT supports a wide variety of directives for "calling" other
477 files, looping, conditional logic, etc. In general, TT simplifies the
478 usual range of Perl operators down to the single dot (C<.>) operator.
479 This applies to operations as diverse as method calls, hash lookups, and
480 list index values (see
481 L<http://www.template-toolkit.org/docs/default/Manual/Variables.html>
482 for details and examples). In addition to the usual C<Template> module
483 Pod documentation, you can access the TT manual at
484 L<http://www.template-toolkit.org/docs/default/>.
486 B<NOTE:> The C<TTSite> helper creates several TT files using an
487 extension of C<.tt2>. Most other Catalyst and TT examples use an
488 extension of C<.tt>. You can use either extension (or no extension at
489 all) with TTSite and TT, just be sure to use the appropriate extension
490 for both the file itself I<and> the C<$c-E<gt>stash-E<gt>{template} =
491 ...> line in your controller. This document will use C<.tt2> for
492 consistency with the files already created by the C<TTSite> helper.
495 =head1 CREATE A SQLITE DATABASE
497 In this step, we make a text file with the required SQL commands to
498 create a database table and load some sample data. Open C<myapp01.sql>
499 in your editor and enter:
502 -- Create a very simple database to hold book and author information
505 id INTEGER PRIMARY KEY,
509 -- 'book_authors' is a many-to-many join table between books & authors
510 CREATE TABLE book_authors (
513 PRIMARY KEY (book_id, author_id)
515 CREATE TABLE authors (
516 id INTEGER PRIMARY KEY,
521 --- Load some sample data
523 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
524 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
525 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
526 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
527 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
528 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
529 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
530 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
531 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
532 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
533 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
534 INSERT INTO authors VALUES (7, 'Nathan', 'Torkington');
535 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
536 INSERT INTO book_authors VALUES (1, 1);
537 INSERT INTO book_authors VALUES (1, 2);
538 INSERT INTO book_authors VALUES (1, 3);
539 INSERT INTO book_authors VALUES (2, 4);
540 INSERT INTO book_authors VALUES (3, 5);
541 INSERT INTO book_authors VALUES (4, 6);
542 INSERT INTO book_authors VALUES (4, 7);
543 INSERT INTO book_authors VALUES (5, 8);
545 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
546 cutting and pasting example code from POD-based documents.
548 Then use the following command to build a C<myapp.db> SQLite database:
550 $ sqlite3 myapp.db < myapp01.sql
552 If you need to create the database more than once, you probably want to
553 issue the C<rm myapp.db> command to delete the database before you use
554 the C<sqlite3 myapp.db < myapp01.sql> command.
556 Once the C<myapp.db> database file has been created and initialized, you
557 can use the SQLite command line environment to do a quick dump of the
562 Enter ".help" for instructions
563 sqlite> select * from books;
564 1|CCSP SNRS Exam Certification Guide|5
565 2|TCP/IP Illustrated, Volume 1|5
566 3|Internetworking with TCP/IP Vol.1|4
568 5|Designing with Web Standards|5
574 $ sqlite3 myapp.db "select * from books"
575 1|CCSP SNRS Exam Certification Guide|5
576 2|TCP/IP Illustrated, Volume 1|5
577 3|Internetworking with TCP/IP Vol.1|4
579 5|Designing with Web Standards|5
581 As with most other SQL tools, if you are using the full "interactive"
582 environment you need to terminate your SQL commands with a ";" (it's not
583 required if you do a single SQL statement on the command line). Use
584 ".q" to exit from SQLite from the SQLite interactive mode and return to
585 your OS command prompt.
588 =head1 DATABASE ACCESS WITH C<DBIx::Class>
590 Catalyst can be used with virtually any form of persistent datastore
591 available via Perl. For example,
592 L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to
593 easily access databases through the traditional Perl C<DBI> interface.
594 However, most Catalyst applications use some form of ORM technology to
595 automatically create and save model objects as they are used. Although
596 Tony Bowden's L<Class::DBI|Class::DBI> has been a popular choice
597 in the past, Matt Trout's L<DBIx::Class|DBIx::Class> (abbreviated
598 as "DBIC") has rapidly emerged as the Perl-based ORM technology of choice.
599 Most new Catalyst applications rely on DBIC, as will this tutorial.
601 =head2 Create a dynamic DBIC Model
603 Use the C<create=dynamic> model helper option to build a model that
604 dynamically reads your database structure every time the application
607 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=dynamic dbi:SQLite:myapp.db
608 exists "/home/kclark/dev/MyApp/script/../lib/MyApp/Model"
609 exists "/home/kclark/dev/MyApp/script/../t"
610 exists "/home/kclark/dev/MyApp/script/../lib/MyApp"
611 created "/home/kclark/dev/MyApp/script/../lib/MyApp/Schema.pm"
612 created "/home/kclark/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
613 created "/home/kclark/dev/MyApp/script/../t/model_DB.t"
616 C<DB> is the name of the model class to be created by the helper in
617 C<lib/MyApp/Model> (Catalyst has a separate directory under C<lib/MyApp>
618 for each of the three parts of MVC: C<Model>, C<View>, and C<Controller>).
619 C<DBIC::Schema> is the type of the model to create.
620 C<MyApp::Schema> is the name of the DBIC schema file written to
621 C<lib/MyApp/Schema.pm>. Because we specified C<create=dynamic>
622 to the helper, it use L<DBIx::Class::Schema::Loader> to dynamically load
623 the schema information from the database every time the application
624 starts. And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect
625 string for use with SQLite.
627 B<NOTE:> Although the C<create=dynamic> option to the DBIC helper
628 makes for a nifty demonstration, is only really suitable for very
629 small applications. After this demonstration, you should almost always
630 use the C<create=static> option that we switch to below.
633 =head1 RUN THE APPLICATION
635 First, let's enable an environment variable option that causes
636 DBIx::Class to dump the SQL statements it's using to access the database
637 (this option can provide extremely helpful troubleshooting information):
639 $ export DBIC_TRACE=1
641 This assumes you are using BASH as your shell -- adjust accordingly if
642 you are using a different shell (for example, under tcsh, use
643 C<setenv DBIC_TRACE 1>).
645 B<NOTE:> You can also set this in your code using
646 C<$class-E<gt>storage-E<gt>debug(1);>. See
647 L<DBIx::Class::Manual::Troubleshooting> for details (including options
648 to log to file instead of displaying to the Catalyst development server
651 Then run the Catalyst "demo server" script:
653 $ script/myapp_server.pl
655 Your development server log output should display something like:
657 $script/myapp_server.pl
658 [debug] Debug messages enabled
659 [debug] Loaded plugins:
660 .----------------------------------------------------------------------------.
661 | Catalyst::Plugin::ConfigLoader 0.17 |
662 | Catalyst::Plugin::StackTrace 0.06 |
663 | Catalyst::Plugin::Static::Simple 0.20 |
664 '----------------------------------------------------------------------------'
666 [debug] Loaded dispatcher "Catalyst::Dispatcher"
667 [debug] Loaded engine "Catalyst::Engine::HTTP"
668 [debug] Found home "/home/me/MyApp"
669 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
670 [debug] Loaded components:
671 .-----------------------------------------------------------------+----------.
673 +-----------------------------------------------------------------+----------+
674 | MyApp::Controller::Books | instance |
675 | MyApp::Controller::Root | instance |
676 | MyApp::Model::DB | instance |
677 | MyApp::Model::DB::Authors | class |
678 | MyApp::Model::DB::BookAuthors | class |
679 | MyApp::Model::DB::Books | class |
680 | MyApp::View::TT | instance |
681 '-----------------------------------------------------------------+----------'
683 [debug] Loaded Private actions:
684 .----------------------+--------------------------------------+--------------.
685 | Private | Class | Method |
686 +----------------------+--------------------------------------+--------------+
687 | /default | MyApp::Controller::Root | default |
688 | /end | MyApp::Controller::Root | end |
689 | /books/index | MyApp::Controller::Books | index |
690 | /books/list | MyApp::Controller::Books | list |
691 '----------------------+--------------------------------------+--------------'
693 [debug] Loaded Path actions:
694 .-------------------------------------+--------------------------------------.
696 +-------------------------------------+--------------------------------------+
697 | /books/list | /books/list |
698 '-------------------------------------+--------------------------------------'
700 [info] MyApp powered by Catalyst 5.7011
701 You can connect to your server at http://localhost:3000
703 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
704 the 'base' directory of your application, not inside the C<script>
705 directory itself or it will not be able to locate the C<myapp.db>
706 database file. You can use a fully qualified or a relative path to
707 locate the database file, but we did not specify that when we ran the
708 model helper earlier.
710 Some things you should note in the output above:
716 Catalyst::Model::DBIC::Schema dynamically created three model classes,
717 one to represent each of the three tables in our database
718 (C<MyApp::Model::DB::Authors>, C<MyApp::Model::DB::BookAuthors>,
719 and C<MyApp::Model::DB::Books>).
723 The "list" action in our Books controller showed up with a path of
728 Point your browser to L<http://localhost:3000> and you should still get
729 the Catalyst welcome page.
731 Next, to view the book list, change the URL in your browser to
732 L<http://localhost:3000/books/list>. You should get a list of the five
733 books loaded by the C<myapp01.sql> script above, with TTSite providing
734 the formatting for the very simple output we generated in our template.
735 The rating for each book should appear on each row.
737 Also notice in the output of the C<script/myapp_server.pl> that DBIC
738 used the following SQL to retrieve the data:
740 SELECT me.id, me.title, me.rating FROM books me
742 because we enabled DBIC_TRACE.
744 You now the beginnings of a simple but workable web application.
745 Continue on to future sections and we will develop the application
749 =head1 A STATIC DATABASE MODEL WITH C<DBIx::Class>
751 =head2 Create Static DBIC Schema Files
753 Unlike the previous section where we had DBIC automatically discover the
754 structure of the database every time the application started, here we
755 will use static schema files for more control. This is typical of most
756 "real world" applications.
758 One option would be to create a separate schema file for each table in
759 the database, however, lets use the same L<DBIx::Class::Schema::Loader>
760 used earlier with C<create=dynamic> to build the static files for us.
761 First, lets remove the schema file created in Part 2:
763 $ rm lib/MyApp/Schema.pm
765 Now regenerate the schema using the C<create=static> option:
767 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=static dbi:SQLite:myapp.db
768 exists "/home/kclark/dev/MyApp/script/../lib/MyApp/Model"
769 exists "/home/kclark/dev/MyApp/script/../t"
770 Dumping manual schema for MyApp::Schema to directory /home/kclark/dev/MyApp/script/../lib ...
771 Schema dump completed.
772 exists "/home/kclark/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
774 We could have also deleted C<lib/MyApp/Model/DB.pm>, but it would
775 have regenerated the same file (note the C<exists> in the output above).
776 If you take a look at C<lib/MyApp/Model/DB.pm>, it simply contains
777 a reference to the actual schema file in C<lib/MyApp/Schema.pm>
778 along with the database connect string.
780 If you look in the C<lib/MyApp/Schema> directory, you will find that
781 C<DB.pm> is no longer using L<DBIx::Class::Schema::Loader> as its
782 base class (L<DBIx::Class::Schema::Loader> is only being used by the
783 helper to load the schema once and then create the static files for us)
784 and that it only contains a call to the C<load_classes> method. You
785 will also find that C<lib/MyApp/Schema> contains a C<Schema>
786 subdirectory, with one file inside this directory for each of the tables
787 in our simple database (C<Authors.pm>, C<BookAuthors.pm>, and
788 C<Books.pm>). These three files were created based on the information
789 found by L<DBIx::Class::Schema::Loader> as the helper ran.
791 The idea with all of the files created under C<lib/MyApp/Schema> by the
792 C<create=static> option is to only edit the files below the C<# DO NOT
793 MODIFY THIS OR ANYTHING ABOVE!> warning. If you place all of your
794 changes below that point in the file, you can regenerate the
795 auto-generated information at the top of each file should your database
796 structure get updated.
798 Also note the "flow" of the model information across the various files
799 and directories. Catalyst will initially load the model from
800 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
801 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally,
802 the call to C<load_classes> in that file will load each of the
803 table-specific "results source" files from the C<lib/MyApp/Schema>
804 subdirectory. These three table-specific DBIC schema files will then be
805 used to create three table-specific Catalyst models every time the
806 application starts (you can see these three model files listed in
807 the debug output generated when you launch the application).
810 =head2 Updating the Generated DBIC Schema Files
813 Let's manually add some relationship information to the auto-generated
814 schema files. First edit C<lib/MyApp/Schema/Books.pm> and
815 add the following text below the C<# You can replace this text...>
824 # 1) Name of relationship, DBIC will create accessor with this name
825 # 2) Name of the model class referenced by this relationship
826 # 3) Column name in *foreign* table
827 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::BookAuthors', 'book_id');
831 # 1) Name of relationship, DBIC will create accessor with this name
832 # 2) Name of has_many() relationship this many_to_many() is shortcut for
833 # 3) Name of belongs_to() relationship in model class of has_many() above
834 # You must already have the has_many() defined to use a many_to_many().
835 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
838 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
839 file. As with any Perl package, we need to end the last line with
840 a statement that evaluates to C<true>. This is customarily done with
841 C<1;> on a line by itself.
843 This code defines both a C<has_many> and a C<many_to_many> relationship.
844 The C<many_to_many> relationship is optional, but it makes it easier to
845 map a book to its collection of authors. Without it, we would have to
846 "walk" though the C<book_authors> table as in C<$book-E<gt>book_authors-
847 E<gt>first-E<gt>author-E<gt>last_name> (we will see examples on how to
848 use DBIC objects in your code soon, but note that because C<$book-
849 E<gt>book_authors> can return multiple authors, we have to use C<first>
850 to display a single author). C<many_to_many> allows us to use the
851 shorter C<$book-E<gt>authors-E<gt>first-E<gt>last_name>. Note that you
852 cannot define a C<many_to_many> relationship without also having the
853 C<has_many> relationship in place.
855 Then edit C<lib/MyApp/Schema/Authors.pm> and add relationship
856 information as follows (again, be careful to put in above the C<1;> but
857 below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
865 # 1) Name of relationship, DBIC will create accessor with this name
866 # 2) Name of the model class referenced by this relationship
867 # 3) Column name in *foreign* table
868 __PACKAGE__->has_many(book_author => 'MyApp::Schema::BookAuthors', 'author_id');
872 # 1) Name of relationship, DBIC will create accessor with this name
873 # 2) Name of has_many() relationship this many_to_many() is shortcut for
874 # 3) Name of belongs_to() relationship in model class of has_many() above
875 # You must already have the has_many() defined to use a many_to_many().
876 __PACKAGE__->many_to_many(books => 'book_author', 'book');
878 Finally, do the same for the "join table,"
879 C<lib/MyApp/Schema/BookAuthors.pm>:
887 # 1) Name of relationship, DBIC will create accessor with this name
888 # 2) Name of the model class referenced by this relationship
889 # 3) Column name in *this* table
890 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Books', 'book_id');
894 # 1) Name of relationship, DBIC will create accessor with this name
895 # 2) Name of the model class referenced by this relationship
896 # 3) Column name in *this* table
897 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Authors', 'author_id');
900 =head1 RUN THE APPLICATION
902 Run the Catalyst "demo server" script with the C<DBIC_TRACE> option
903 (it might still be enabled from earlier in the tutorial, but here
904 is an alternate way to specify the option just in case):
906 $ DBIC_TRACE=1 script/myapp_server.pl
908 Make sure that the application loads correctly and that you see the
909 three dynamically created model class (one for each of the
910 table-specific schema classes we created).
912 Then hit the URL L<http://localhost:3000/books/list> and be sure that
913 the book list is displayed.
916 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
918 In some situations, it can be useful to run your application and
919 display a page without using a browser. Catalyst lets you do this
920 using the C<scripts/myapp_test.pl> script. Just supply the URL you
921 wish to display and it will run that request through the normal
922 controller dispatch logic and use the appropriate view to render the
923 output (obviously, complex pages may dump a lot of text to your
924 terminal window). For example, if you type:
926 $ script/myapp_test.pl "/books/list"
928 You should get the same text as if you visited
929 L<http://localhost:3000/books/list> with the normal development server
930 and asked your browser to view the page source.
933 =head1 UPDATING THE VIEW
935 Let's add a new column to our book list page that takes advantage of
936 the relationship information we manually added to our schema files
937 in the previous section. Edit C<root/src/books/list.tt2> add add the
938 following code below the existing table cell that contains
939 C<book.rating> (IOW, add a new table cell below the existing two
943 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
944 [% # loop in 'side effect notation' to load just the last names of the -%]
945 [% # authors into the list. Note that the 'push' TT vmethod does not -%]
946 [% # a value, so nothing will be printed here. But, if you have something -%]
947 [% # in TT that does return a method and you don't want it printed, you -%]
948 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
949 [% # call it and discard the return value. -%]
951 tt_authors.push(author.last_name) FOREACH author = book.authors %]
952 [% # Now use a TT 'virtual method' to display the author count in parens -%]
953 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
954 ([% tt_authors.size | html %])
955 [% # Use another TT vmethod to join & print the names & comma separators -%]
956 [% tt_authors.join(', ') | html %]
959 Then hit C<Ctrl+R> in your browser (not that you don't need to reload
960 the development server or use the C<-r> option when updating TT
961 templates) and you should now the the number of authors each book and
962 a comma-separated list of the author's last names.
964 If you are still running the development server with C<DBIC_TRACE>
965 enabled, you should also now see five more C<SELECT> statements in the
966 debug output (one for each book as the authors are being retrieved by
969 Also note that we are using "| html", a type of TT filter, to escape
970 characters such as E<lt> and E<gt> to < and > and avoid various
971 types of dangerous hacks against your application. In a real
972 application, you would probably want to put "| html" at the end of
973 every field where a user has control over the information that can
974 appear in that field (and can therefore inject markup or code if you
975 don't "neutralize" those fields). In addition to "| html", Template
976 Toolkit has a variety of other useful filters that can found in the
977 documentation for L<Template::Filters|Template::Filters>.
980 =head2 Using C<RenderView> for the Default View
982 B<NOTE: The rest of this part of the tutorial is optional. You can
983 skip to Part 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
986 Once your controller logic has processed the request from a user, it
987 forwards processing to your view in order to generate the appropriate
988 response output. Catalyst uses
989 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
990 default to automatically performs this operation. If you look in
991 C<lib/MyApp/Controller/Root.pm>, you should see the empty
992 definition for the C<sub end> method:
994 sub end : ActionClass('RenderView') {}
996 The following bullet points provide a quick overview of the
997 C<RenderView> process:
1003 C<Root.pm> is designed to hold application-wide logic.
1007 At the end of a given user request, Catalyst will call the most specific
1008 C<end> method that's appropriate. For example, if the controller for a
1009 request has an C<end> method defined, it will be called. However, if
1010 the controller does not define a controller-specific C<end> method, the
1011 "global" C<end> method in C<Root.pm> will be called.
1015 Because the definition includes an C<ActionClass> attribute, the
1016 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1017 will be executed B<after> any code inside the definition of C<sub end>
1018 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1019 for more information on C<ActionClass>.
1023 Because C<sub end> is empty, this effectively just runs the default
1024 logic in C<RenderView>. However, you can easily extend the
1025 C<RenderView> logic by adding your own code inside the empty method body
1026 (C<{}>) created by the Catalyst Helpers when we first ran the
1027 C<catalyst.pl> to initialize our application. See
1028 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1029 detailed information on how to extended C<RenderView> in C<sub end>.
1034 =head2 Using The Default Template Name
1036 By default, C<Catalyst::View::TT> will look for a template that uses the
1037 same name as your controller action, allowing you to save the step of
1038 manually specifying the template name in each action. For example, this
1039 would allow us to remove the
1040 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1041 C<list> action in the Books controller. Open
1042 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1043 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1048 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1053 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1054 # 'Context' that's used to 'glue together' the various components
1055 # that make up the application
1056 my ($self, $c) = @_;
1058 # Retrieve all of the book records as book model objects and store in the
1059 # stash where they can be accessed by the TT template
1060 $c->stash->{books} = [$c->model('DB::Books')->all];
1062 # Set the TT template to use. You will almost always want to do this
1063 # in your action methods (actions methods respond to user input in
1064 # your controllers).
1065 #$c->stash->{template} = 'books/list.tt2';
1068 C<Catalyst::View::TT> defaults to looking for a template with no
1069 extension. In our case, we need to override this to look for an
1070 extension of C<.tt2>. Open C<lib/MyApp/View/TT.pm> and add the
1071 C<TEMPLATE_EXTENSION> definition as follows:
1073 __PACKAGE__->config({
1074 CATALYST_VAR => 'Catalyst',
1076 MyApp->path_to( 'root', 'src' ),
1077 MyApp->path_to( 'root', 'lib' )
1079 PRE_PROCESS => 'config/main',
1080 WRAPPER => 'site/wrapper',
1081 ERROR => 'error.tt2',
1083 TEMPLATE_EXTENSION => '.tt2',
1086 You should now be able to restart the development server as per the
1087 previous section and access the L<http://localhost:3000/books/list>
1090 B<NOTE:> Please note that if you use the default template technique,
1091 you will B<not> be able to use either the C<$c-E<gt>forward> or
1092 the C<$c-E<gt>detach> mechanisms (these are discussed in Part 2 and
1093 Part 9 of the Tutorial).
1096 =head2 Return To A Manually-Specified Template
1098 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1099 later in the tutorial, you should remove the comment from the
1100 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1102 $c->stash->{template} = 'books/list.tt2';
1104 Then delete the C<TEMPLATE_EXTENSION> line in
1105 C<lib/MyApp/View/TT.pm>.
1107 You should then be able to restart the development server and
1108 access L<http://localhost:3000/books/list> in the same manner as
1109 with earlier sections.
1114 Kennedy Clark, C<hkclark@gmail.com>
1116 Please report any errors, issues or suggestions to the author. The
1117 most recent version of the Catalyst Tutorial can be found at
1118 L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/Catalyst-Manual/lib/Catalyst/Manual/Tutorial/>.
1120 Copyright 2006, Kennedy Clark, under Creative Commons License
1121 (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).