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 C<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);'
170 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
172 C<Static::Simple> provides an easy method of serving static content such
173 as images and CSS files under the development server.
177 To modify the list of plugins, edit C<lib/MyApp.pm> (this file is
178 generally referred to as your I<application class>) and delete the line
181 use Catalyst qw/-Debug ConfigLoader Static::Simple/;
193 This tells Catalyst to start using one new plugin:
199 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>
201 Adds a stack trace to the standard Catalyst "debug screen" (this is the
202 screen Catalyst sends to your browser when an error occurs).
204 Note: L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
205 browser, not in the console window from which you're running your
206 application, which is where logging output usually goes.
210 Note that when specifying plugins on the C<use Catalyst> line, you can
211 omit C<Catalyst::Plugin::> from the name. Additionally, you can spread
212 the plugin names across multiple lines as shown here, or place them all
213 on one (or more) lines as with the default configuration.
216 =head1 CREATE A CATALYST CONTROLLER
218 As discussed earlier, controllers are where you write methods that
219 interact with user input. Typically, controller methods respond to
220 C<GET> and C<POST> messages from the user's web browser.
222 Use the Catalyst C<create> script to add a controller for book-related
225 $ script/myapp_create.pl controller Books
226 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
227 exists "/home/me/MyApp/script/../t"
228 created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm"
229 created "/home/me/MyApp/script/../t/controller_Books.t"
231 Then edit C<lib/MyApp/Controller/Books.pm> and add the following method
236 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
241 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
242 # 'Context' that's used to 'glue together' the various components
243 # that make up the application
246 # Retrieve all of the book records as book model objects and store in the
247 # stash where they can be accessed by the TT template
248 $c->stash->{books} = [$c->model('MyAppDB::Books')->all];
250 # Set the TT template to use. You will almost always want to do this
251 # in your action methods (action methods respond to user input in
253 $c->stash->{template} = 'books/list.tt2';
256 B<Note:> This won't actually work yet since you haven't set up your
259 B<Note:> Programmers experienced with object-oriented Perl should
260 recognize C<$self> as a reference to the object where this method was
261 called. On the other hand, C<$c> will be new to many Perl programmers
262 who have not used Catalyst before (it's sometimes written as
263 C<$context>). The Context object is automatically passed to all
264 Catalyst components. It is used to pass information between
265 components and provide access to Catalyst and plugin functionality.
267 B<TIP>: You may see the C<$c-E<gt>model('MyAppDB::Book')> used above
268 written as C<$c-E<gt>model('MyAppDB')-E<gt>resultset('Book)>. The two
271 B<Note:> Catalyst actions are regular Perl methods, but they make use
272 of Nicholas Clark's C<attributes> module (that's the C<: Local> next
273 to the C<sub list> in the code above) to provide additional
274 information to the Catalyst dispatcher logic. Many newer Catalyst
275 applications are switching to the use of "Literal" C<: Path> actions
276 and C<Args> attribute in lieu of C<: Local> and C<: Private>. For
277 example, C<sub any_method : Path Args(0)> can be used instead of
278 C<sub index :Private> (because no path was supplied to C<Path> it
279 matches the "empty" URL in the namespace of that module... the same
280 thing C<sub index> would do) or C<sub list : Path('list') Args(0)>
281 could be used instead of the C<sub list : Local> above (the C<list>
282 argument to C<Path> would make it match on the URL C<list> under
283 C<books>, the namespace of the current module). See "Action Types" in
284 L<Catalyst::Manual::Intro|Catalyst::Manual::Intro> as well as Part 5
285 of this tutorial (Authentication) for additional information. Another
286 popular but more advanced feature is C<Chained> actions that allow a
287 single URL to "chain together" multiple action method calls, each with
288 an appropriate number of arguments (see
289 L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
293 =head1 CATALYST VIEWS
295 As mentioned in Part 2 of the tutorial, views are where you render
296 output, typically for display in the user's web browser, but also
297 possibly using other display output- generation systems. As with
298 virtually every aspect of Catalyst, options abound when it comes to
299 the specific view technology you adopt inside your application.
300 However, most Catalyst applications use the Template Toolkit, known as
301 TT (for more information on TT, see L<http://www.template-
302 toolkit.org>). Other popular view technologies include Mason
303 (L<http://www.masonhq.com> and L<http://www.masonbook.com>) and
304 L<HTML::Template|HTML::Template> (L<http://html-
305 template.sourceforge.net>).
307 =head2 Create a Catalyst View Using C<TTSite>
309 When using TT for the Catalyst view, there are two main helper scripts:
315 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
319 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
323 Both are similar, but C<TT> merely creates the C<lib/MyApp/View/TT.pm>
324 file and leaves the creation of any hierarchical template organization
325 entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
326 test cases will be discussed in Part 8). The C<TTSite> helper creates a
327 modular and hierarchical view layout with separate Template Toolkit (TT)
328 files for common header and footer information, configuration values, a
329 CSS stylesheet, and more.
331 While TTSite is useful to bootstrap a project, we recommend that
332 unless you know what you're doing or want to pretty much use the
333 supplied templates as is, that you use the plain Template Toolkit view
334 when starting a project from scratch. This is because TTSite can be
335 tricky to customize. Additionally TT contains constructs that you
336 need to learn yourself if you're going to be a serious user of TT.
337 Our experience suggests that you're better off learning these from
338 scratch. We use TTSite here precisely because it is useful for
339 bootstrap/prototype purposes.
341 Enter the following command to enable the C<TTSite> style of view
342 rendering for this tutorial:
344 $ script/myapp_create.pl view TT TTSite
345 exists "/home/me/MyApp/script/../lib/MyApp/View"
346 exists "/home/me/MyApp/script/../t"
347 created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm"
348 created "/home/me/MyApp/script/../root/lib"
350 created "/home/me/MyApp/script/../root/src/ttsite.css"
352 This puts a number of files in the C<root/lib> and C<root/src>
353 directories that can be used to customize the look and feel of your
354 application. Also take a look at C<lib/MyApp/View/TT.pm> for config
355 values set by the C<TTSite> helper.
357 B<TIP>: Note that TTSite does one thing that could confuse people who
358 are used to the normal C<TT> Catalyst view: it redefines the Catalyst
359 context object in templates from its usual C<c> to C<Catalyst>. When
360 looking at other Catalyst examples, remember that they almost always use
361 C<c>. Note that Catalyst and TT I<do not complain> when you use the
362 wrong name to access the context object...TT simply outputs blanks for
363 that bogus logic (see next tip to change this behavior with TT C<DEBUG>
364 options). Finally, be aware that this change in name I<only>
365 applies to how the context object is accessed inside your TT templates;
366 your controllers will continue to use C<$c> (or whatever name you use
367 when fetching the reference from C<@_> inside your methods). (You can
368 change back to the "default" behavior be removing the C<CATALYST_VAR>
369 line from C<lib/MyApp/View/TT.pm>, but you will also have to edit
370 C<root/lib/config/main> and C<root/lib/config/url>. If you do this, be
371 careful not to have a collision between your own C<c> variable and the
372 Catalyst C<c> variable.)
374 B<TIP>: When troubleshooting TT it can be helpful to enable variable
375 C<DEBUG> options. You can do this in a Catalyst environment by adding
376 a C<DEBUG> line to the C<__PACKAGE__->config> declaration in
377 C<lib/MyApp/View/TT.pm>:
379 __PACKAGE__->config({
380 CATALYST_VAR => 'Catalyst',
386 B<Note:> C<__PACKAGE__> is just a shorthand way of referencing the name
387 of the package where it is used. Therefore, in C<TT.pm>,
388 C<__PACKAGE__> is equivalent to C<TT>.
390 There are a variety of options you can use, such as 'undef', 'all',
391 'service', 'context', 'parser', 'provider', and 'service'. See
392 L<Template::Constants> for more information (remove the C<DEBUG_>
393 portion of the name shown in the TT docs and convert to lower case
394 for use inside Catalyst).
396 B<NOTE:> B<Please be sure to disable TT debug options before
397 continuing the tutorial> (especially the 'undef' option -- leaving
398 this enabled will conflict with several of the conventions used
399 by this tutorial and TTSite to leave some variables undefined
403 =head2 Globally Customize Every View
405 When using TTSite, files in the subdirectories of C<root/lib> can be
406 used to make changes that will appear in every view. For example, to
407 display optional status and error messages in every view, edit
408 C<root/lib/site/layout>, updating it to match the following (the two HTML
409 C<span> elements are new):
411 <div id="header">[% PROCESS site/header %]</div>
414 <span class="message">[% status_msg %]</span>
415 <span class="error">[% error_msg %]</span>
419 <div id="footer">[% PROCESS site/footer %]</div>
421 If we set either message in the Catalyst stash (e.g.,
422 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it will
423 be displayed whenever any view used by that request is rendered. The
424 C<message> and C<error> CSS styles are automatically defined in
425 C<root/src/ttsite.css> and can be customized to suit your needs.
427 B<Note:> The Catalyst stash only lasts for a single HTTP request. If
428 you need to retain information across requests you can use
429 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
430 Catalyst sessions in the Authentication part of the tutorial).
433 =head2 Create a TT Template Page
435 To add a new page of content to the TTSite view hierarchy, just create a
436 new C<.tt2> file in C<root/src>. Only include HTML markup that goes
437 inside the HTML <body> and </body> tags, TTSite will use the contents of
438 C<root/lib/site> to add the top and bottom.
440 First create a directory for book-related TT templates:
442 $ mkdir root/src/books
444 Then create C<root/src/books/list.tt2> in your editor and enter:
446 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
447 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
448 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
449 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
451 [% # Provide a title to root/lib/site/header -%]
452 [% META title = 'Book List' -%]
455 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
456 [% # Display each book in a table row %]
457 [% FOREACH book IN books -%]
459 <td>[% book.title %]</td>
460 <td>[% book.rating %]</td>
465 As indicated by the inline comments above, the C<META title> line uses
466 TT's META feature to provide a title to C<root/lib/site/header>.
467 Meanwhile, the outer C<FOREACH> loop iterates through each C<book> model
468 object and prints the C<title> and C<rating> fields. An inner
469 C<FOREACH> loop prints the last name of each author in a comma-separated
470 list within a single table cell.
472 If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT
473 code. TT supports a wide variety of directives for "calling" other
474 files, looping, conditional logic, etc. In general, TT simplifies the
475 usual range of Perl operators down to the single dot (C<.>) operator.
476 This applies to operations as diverse as method calls, hash lookups, and
477 list index values (see
478 L<http://www.template-toolkit.org/docs/default/Manual/Variables.html>
479 for details and examples). In addition to the usual C<Template> module
480 Pod documentation, you can access the TT manual at
481 L<http://www.template-toolkit.org/docs/default/>.
483 B<NOTE>: The C<TTSite> helper creates several TT files using an
484 extension of C<.tt2>. Most other Catalyst and TT examples use an
485 extension of C<.tt>. You can use either extension (or no extension at
486 all) with TTSite and TT, just be sure to use the appropriate extension
487 for both the file itself I<and> the C<$c-E<gt>stash-E<gt>{template} =
488 ...> line in your controller. This document will use C<.tt2> for
489 consistency with the files already created by the C<TTSite> helper.
492 =head1 CREATE A SQLITE DATABASE
494 In this step, we make a text file with the required SQL commands to
495 create a database table and load some sample data. Open C<myapp01.sql>
496 in your editor and enter:
499 -- Create a very simple database to hold book and author information
502 id INTEGER PRIMARY KEY,
506 -- 'book_authors' is a many-to-many join table between books & authors
507 CREATE TABLE book_authors (
510 PRIMARY KEY (book_id, author_id)
512 CREATE TABLE authors (
513 id INTEGER PRIMARY KEY,
518 --- Load some sample data
520 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
521 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
522 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
523 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
524 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
525 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
526 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
527 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
528 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
529 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
530 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
531 INSERT INTO authors VALUES (7, 'Nathan', 'Torkington');
532 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
533 INSERT INTO book_authors VALUES (1, 1);
534 INSERT INTO book_authors VALUES (1, 2);
535 INSERT INTO book_authors VALUES (1, 3);
536 INSERT INTO book_authors VALUES (2, 4);
537 INSERT INTO book_authors VALUES (3, 5);
538 INSERT INTO book_authors VALUES (4, 6);
539 INSERT INTO book_authors VALUES (4, 7);
540 INSERT INTO book_authors VALUES (5, 8);
542 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
543 cutting and pasting example code from POD-based documents.
545 Then use the following command to build a C<myapp.db> SQLite database:
547 $ sqlite3 myapp.db < myapp01.sql
549 If you need to create the database more than once, you probably want to
550 issue the C<rm myapp.db> command to delete the database before you use
551 the C<sqlite3 myapp.db < myapp01.sql> command.
553 Once the C<myapp.db> database file has been created and initialized, you
554 can use the SQLite command line environment to do a quick dump of the
559 Enter ".help" for instructions
560 sqlite> select * from books;
561 1|CCSP SNRS Exam Certification Guide|5
562 2|TCP/IP Illustrated, Volume 1|5
563 3|Internetworking with TCP/IP Vol.1|4
565 5|Designing with Web Standards|5
571 $ sqlite3 myapp.db "select * from books"
572 1|CCSP SNRS Exam Certification Guide|5
573 2|TCP/IP Illustrated, Volume 1|5
574 3|Internetworking with TCP/IP Vol.1|4
576 5|Designing with Web Standards|5
578 As with most other SQL tools, if you are using the full "interactive"
579 environment you need to terminate your SQL commands with a ";" (it's not
580 required if you do a single SQL statement on the command line). Use
581 ".q" to exit from SQLite from the SQLite interactive mode and return to
582 your OS command prompt.
585 =head1 DATABASE ACCESS WITH C<DBIx::Class>
587 Catalyst can be used with virtually any form of persistent datastore
588 available via Perl. For example,
589 L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to
590 easily access databases through the traditional Perl C<DBI> interface.
591 However, most Catalyst applications use some form of ORM technology to
592 automatically create and save model objects as they are used. Although
593 Tony Bowden's L<Class::DBI|Class::DBI> has been a popular choice
594 in the past, Matt Trout's L<DBIx::Class|DBIx::Class> (abbreviated
595 as "DBIC") has rapidly emerged as the Perl-based ORM technology of choice.
596 Most new Catalyst applications rely on DBIC, as will this tutorial.
598 =head2 Create a dynamic DBIC Model
600 Use the C<create=dynamic> model helper option to build a model that
601 dynamically reads your database structure every time the application
604 $ script/myapp_create.pl model MyAppDB DBIC::Schema MyApp::Schema::MyAppDB create=dynamic dbi:SQLite:myapp.db
605 exists "/home/me/MyApp/script/../lib/MyApp/Model"
606 exists "/home/me/MyApp/script/../t"
607 created "/home/me/MyApp/script/../lib/MyApp/Schema"
608 created "/home/me/MyApp/script/../lib/MyApp/Schema/MyAppDB.pm"
609 created "/home/me/MyApp/script/../lib/MyApp/Model/MyAppDB.pm"
610 created "/home/me/MyApp/script/../t/model_MyAppDB.t"
613 C<MyAppDB> is the name of the model class to be created by the helper in
614 C<lib/MyApp/Model> (Catalyst has a separate directory under C<lib/MyApp>
615 for each of the three parts of MVC: C<Model>, C<View>, and C<Controller>
616 [although older Catalyst applications often use the directories C<M>,
617 C<V>, and C<C>]). C<DBIC::Schema> is the type of the model to create.
618 C<MyApp::Schema::MyAppDB> is the name of the DBIC schema file written to
619 C<lib/MyApp/Schema/MyAppDB.pm>. Because we specified C<create=dynamic>
620 to the helper, it use L<DBIx::Class::Schema::Loader> to dynamically load
621 the schema information from the database every time the application
622 starts. And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect
623 string for use with SQLite.
625 B<NOTE>: Although the C<create=dynamic> option to the DBIC helper
626 makes for a nifty demonstration, is only really suitable for very
627 small applications. After this demonstration, you should almost always
628 use the C<create=static> option that we switch to below.
631 =head1 RUN THE APPLICATION
633 First, let's enable an environment variable option that causes
634 DBIx::Class to dump the SQL statements it's using to access the database
635 (this option can provide extremely helpful troubleshooting information):
637 $ export DBIC_TRACE=1
639 This assumes you are using BASH as your shell -- adjust accordingly if
640 you are using a different shell (for example, under tcsh, use
641 C<setenv DBIC_TRACE 1>).
643 B<NOTE>: You can also set this in your code using
644 C<$class-E<gt>storage-E<gt>debug(1);>. See
645 L<DBIx::Class::Manual::Troubleshooting> for details (including options
646 to log to file instead of displaying to the Catalyst development server
649 Then run the Catalyst "demo server" script:
651 $ script/myapp_server.pl
653 Your development server log output should display something like:
655 $script/myapp_server.pl
656 [debug] Debug messages enabled
657 [debug] Loaded plugins:
658 .----------------------------------------------------------------------------.
659 | Catalyst::Plugin::ConfigLoader 0.17 |
660 | Catalyst::Plugin::StackTrace 0.06 |
661 | Catalyst::Plugin::Static::Simple 0.20 |
662 '----------------------------------------------------------------------------'
664 [debug] Loaded dispatcher "Catalyst::Dispatcher"
665 [debug] Loaded engine "Catalyst::Engine::HTTP"
666 [debug] Found home "/home/me/MyApp"
667 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
668 [debug] Loaded components:
669 .-----------------------------------------------------------------+----------.
671 +-----------------------------------------------------------------+----------+
672 | MyApp::Controller::Books | instance |
673 | MyApp::Controller::Root | instance |
674 | MyApp::Model::MyAppDB | instance |
675 | MyApp::Model::MyAppDB::Authors | class |
676 | MyApp::Model::MyAppDB::BookAuthors | class |
677 | MyApp::Model::MyAppDB::Books | class |
678 | MyApp::View::TT | instance |
679 '-----------------------------------------------------------------+----------'
681 [debug] Loaded Private actions:
682 .----------------------+--------------------------------------+--------------.
683 | Private | Class | Method |
684 +----------------------+--------------------------------------+--------------+
685 | /default | MyApp::Controller::Root | default |
686 | /end | MyApp::Controller::Root | end |
687 | /books/index | MyApp::Controller::Books | index |
688 | /books/list | MyApp::Controller::Books | list |
689 '----------------------+--------------------------------------+--------------'
691 [debug] Loaded Path actions:
692 .-------------------------------------+--------------------------------------.
694 +-------------------------------------+--------------------------------------+
695 | /books/list | /books/list |
696 '-------------------------------------+--------------------------------------'
698 [info] MyApp powered by Catalyst 5.7011
699 You can connect to your server at http://localhost:3000
701 B<NOTE>: Be sure you run the C<script/myapp_server.pl> command from
702 the 'base' directory of your application, not inside the C<script>
703 directory itself or it will not be able to locate the C<myapp.db>
704 database file. You can use a fully qualified or a relative path to
705 locate the database file, but we did not specify that when we ran the
706 model helper earlier.
708 Some things you should note in the output above:
714 Catalyst::Model::DBIC::Schema dynamically created three model classes,
715 one to represent each of the three tables in our database
716 (C<MyApp::Model::MyAppDB::Authors>, C<MyApp::Model::MyAppDB::BookAuthors>,
717 and C<MyApp::Model::MyAppDB::Books>).
721 The "list" action in our Books controller showed up with a path of
726 Point your browser to L<http://localhost:3000> and you should still get
727 the Catalyst welcome page.
729 Next, to view the book list, change the URL in your browser to
730 L<http://localhost:3000/books/list>. You should get a list of the five
731 books loaded by the C<myapp01.sql> script above, with TTSite providing
732 the formatting for the very simple output we generated in our template.
733 The rating for each book should appear on each row.
735 Also notice in the output of the C<script/myapp_server.pl> that DBIC
736 used the following SQL to retrieve the data:
738 SELECT me.id, me.title, me.rating FROM books me
740 because we enabled DBIC_TRACE.
742 You now the beginnings of a simple but workable web application.
743 Continue on to future sections and we will develop the application
747 =head1 A STATIC DATABASE MODEL WITH C<DBIx::Class>
749 =head2 Create Static DBIC Schema Files
751 Unlike the previous section where we had DBIC automatically discover the
752 structure of the database every time the application started, here we
753 will use static schema files for more control. This is typical of most
754 "real world" applications.
756 One option would be to create a separate schema file for each table in
757 the database, however, lets use the same L<DBIx::Class::Schema::Loader>
758 used earlier with C<create=dynamic> to build the static files for us.
759 First, lets remove the schema file created in Part 2:
761 $ rm lib/MyApp/Schema/MyAppDB.pm
763 Now regenerate the schema using the C<create=static> option:
765 $ script/myapp_create.pl model MyAppDB DBIC::Schema MyApp::Schema::MyAppDB create=static dbi:SQLite:myapp.db
766 exists "/home/me/MyApp/script/../lib/MyApp/Model"
767 exists "/home/me/MyApp/script/../t"
768 Dumping manual schema for MyApp::Schema::MyAppDB to directory /home/me/MyApp/script/../lib ...
769 Schema dump completed.
770 exists "/home/me/MyApp/script/../lib/MyApp/Model/MyAppDB.pm"
772 We could have also deleted C<lib/MyApp/Model/MyAppDB.pm>, but it would
773 have regenerated the same file (note the C<exists> in the output above).
774 If you take a look at C<lib/MyApp/Model/MyAppDB.pm>, it simply contains
775 a reference to the actual schema file in C<lib/MyApp/Schema/MyAppDB.pm>
776 along with the database connect string.
778 If you look in the C<lib/MyApp/Schema> directory, you will find that
779 C<MyAppDB.pm> is no longer using L<DBIx::Class::Schema::Loader> as its
780 base class (L<DBIx::Class::Schema::Loader> is only being used by the
781 helper to load the schema once and then create the static files for us)
782 and that it only contains a call to the C<load_classes> method. You
783 will also find that C<lib/MyApp/Schema> contains a C<MyAppDB>
784 subdirectory, with one file inside this directory for each of the tables
785 in our simple database (C<Authors.pm>, C<BookAuthors.pm>, and
786 C<Books.pm>). These three files were created based on the information
787 found by L<DBIx::Class::Schema::Loader> as the helper ran.
789 The idea with all of the files created under C<lib/MyApp/Schema> by the
790 C<create=static> option is to only edit the files below the C<# DO NOT
791 MODIFY THIS OR ANYTHING ABOVE!> warning. If you place all of your
792 changes below that point in the file, you can regenerate the
793 auto-generated information at the top of each file should your database
794 structure get updated.
796 Also note the "flow" of the model information across the various files
797 and directories. Catalyst will initially load the model from
798 C<lib/MyApp/Model/MyAppDB.pm>. This file contains a reference to
799 C<lib/MyApp/Schema/MyAppDB.pm>, so that file is loaded next. Finally,
800 the call to C<load_classes> in that file will load each of the
801 table-specific "results source" files from the C<lib/MyApp/Schema/MyAppDB>
802 subdirectory. These three table-specific DBIC schema files will then be
803 used to create three table-specific Catalyst models every time the
804 application starts (you can see these three model files listed in
805 the debug output generated when you launch the application).
808 =head2 Updating the Generated DBIC Schema Files
811 Let's manually add some relationship information to the auto-generated
812 schema files. First edit C<lib/MyApp/Schema/MyAppDB/Books.pm> and
813 add the following text below the C<# You can replace this text...>
822 # 1) Name of relationship, DBIC will create accessor with this name
823 # 2) Name of the model class referenced by this relationship
824 # 3) Column name in *foreign* table
825 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::MyAppDB::BookAuthors', 'book_id');
829 # 1) Name of relationship, DBIC will create accessor with this name
830 # 2) Name of has_many() relationship this many_to_many() is shortcut for
831 # 3) Name of belongs_to() relationship in model class of has_many() above
832 # You must already have the has_many() defined to use a many_to_many().
833 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
836 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
837 file. As with any Perl package, we need to end the last line with
838 a statement that evaluates to C<true>. This is customarily done with
839 C<1;> on a line by itself.
841 This code defines both a C<has_many> and a C<many_to_many> relationship.
842 The C<many_to_many> relationship is optional, but it makes it easier to
843 map a book to its collection of authors. Without it, we would have to
844 "walk" though the C<book_authors> table as in C<$book-E<gt>book_authors-
845 E<gt>first-E<gt>author-E<gt>last_name> (we will see examples on how to
846 use DBIC objects in your code soon, but note that because C<$book-
847 E<gt>book_authors> can return multiple authors, we have to use C<first>
848 to display a single author). C<many_to_many> allows us to use the
849 shorter C<$book-E<gt>authors-E<gt>first-E<gt>last_name>. Note that you
850 cannot define a C<many_to_many> relationship without also having the
851 C<has_many> relationship in place.
853 Then edit C<lib/MyApp/Schema/MyAppDB/Authors.pm> and add relationship
854 information as follows (again, be careful to put in above the C<1;> but
855 below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
863 # 1) Name of relationship, DBIC will create accessor with this name
864 # 2) Name of the model class referenced by this relationship
865 # 3) Column name in *foreign* table
866 __PACKAGE__->has_many(book_author => 'MyApp::Schema::MyAppDB::BookAuthors', 'author_id');
870 # 1) Name of relationship, DBIC will create accessor with this name
871 # 2) Name of has_many() relationship this many_to_many() is shortcut for
872 # 3) Name of belongs_to() relationship in model class of has_many() above
873 # You must already have the has_many() defined to use a many_to_many().
874 __PACKAGE__->many_to_many(books => 'book_author', 'book');
876 Finally, do the same for the "join table,"
877 C<lib/MyApp/Schema/MyAppDB/BookAuthors.pm>:
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(book => 'MyApp::Schema::MyAppDB::Books', 'book_id');
892 # 1) Name of relationship, DBIC will create accessor with this name
893 # 2) Name of the model class referenced by this relationship
894 # 3) Column name in *this* table
895 __PACKAGE__->belongs_to(author => 'MyApp::Schema::MyAppDB::Authors', 'author_id');
898 =head1 RUN THE APPLICATION
900 Run the Catalyst "demo server" script with the C<DBIC_TRACE> option
901 (it might still be enabled from earlier in the tutorial, but here
902 is an alternate way to specify the option just in case):
904 $ DBIC_TRACE=1 script/myapp_server.pl
906 Make sure that the application loads correctly and that you see the
907 three dynamically created model class (one for each of the
908 table-specific schema classes we created).
910 Then hit the URL L<http://localhost:3000/books/list> and be sure that
911 the book list is displayed.
914 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
916 In some situations, it can be useful to run your application and
917 display a page without using a browser. Catalyst lets you do this
918 using the C<scripts/myapp_test.pl> script. Just supply the URL you
919 wish to display and it will run that request through the normal
920 controller dispatch logic and use the appropriate view to render the
921 output (obviously, complex pages may dump a lot of text to your
922 terminal window). For example, if you type:
924 $ script/myapp_test.pl "/books/list"
926 You should get the same text as if you visited
927 L<http://localhost:3000/books/list> with the normal development server
928 and asked your browser to view the page source.
931 =head1 UPDATING THE VIEW
933 Let's add a new column to our book list page that takes advantage of
934 the relationship information we manually added to our schema files
935 in the previous section. Edit C<root/src/books/list.tt2> add add the
936 following code below the existing table cell that contains
937 C<book.rating> (IOW, add a new table cell below the existing two
941 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
942 [% # loop in 'side effect notation' to load just the last names of the -%]
943 [% # authors into the list. Note that the 'push' TT vmethod does not -%]
944 [% # a value, so nothing will be printed here. But, if you have something -%]
945 [% # in TT that does return a method and you don't want it printed, you -%]
946 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
947 [% # call it and discard the return value. -%]
949 tt_authors.push(author.last_name) FOREACH author = book.authors %]
950 [% # Now use a TT 'virtual method' to display the author count in parens -%]
951 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
952 ([% tt_authors.size | html %])
953 [% # Use another TT vmethod to join & print the names & comma separators -%]
954 [% tt_authors.join(', ') | html %]
957 Then hit C<Ctrl+R> in your browser (not that you don't need to reload
958 the development server or use the C<-r> option when updating TT
959 templates) and you should now the the number of authors each book and
960 a comma-separated list of the author's last names.
962 If you are still running the development server with C<DBIC_TRACE>
963 enabled, you should also now see five more C<SELECT> statements in the
964 debug output (one for each book as the authors are being retrieved by
967 Also note that we are using "| html", a type of TT filter, to escape
968 characters such as E<lt> and E<gt> to < and > and avoid various
969 types of dangerous hacks against your application. In a real
970 application, you would probably want to put "| html" at the end of
971 every field where a user has control over the information that can
972 appear in that field (and can therefore inject markup or code if you
973 don't "neutralize" those fields). In addition to "| html", Template
974 Toolkit has a variety of other useful filters that can found in the
975 documentation for L<Template::Filters|Template::Filters>.
978 =head2 Using C<RenderView> for the Default View
980 B<NOTE: The rest of this part of the tutorial is optional. You can
981 skip to Part 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
984 Once your controller logic has processed the request from a user, it
985 forwards processing to your view in order to generate the appropriate
986 response output. Catalyst uses
987 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
988 default to automatically performs this operation. If you look in
989 C<lib/MyApp/Controller/Root.pm>, you should see the empty
990 definition for the C<sub end> method:
992 sub end : ActionClass('RenderView') {}
994 The following bullet points provide a quick overview of the
995 C<RenderView> process:
1001 C<Root.pm> is designed to hold application-wide logic.
1005 At the end of a given user request, Catalyst will call the most specific
1006 C<end> method that's appropriate. For example, if the controller for a
1007 request has an C<end> method defined, it will be called. However, if
1008 the controller does not define a controller-specific C<end> method, the
1009 "global" C<end> method in C<Root.pm> will be called.
1013 Because the definition includes an C<ActionClass> attribute, the
1014 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1015 will be executed B<after> any code inside the definition of C<sub end>
1016 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1017 for more information on C<ActionClass>.
1021 Because C<sub end> is empty, this effectively just runs the default
1022 logic in C<RenderView>. However, you can easily extend the
1023 C<RenderView> logic by adding your own code inside the empty method body
1024 (C<{}>) created by the Catalyst Helpers when we first ran the
1025 C<catalyst.pl> to initialize our application. See
1026 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1027 detailed information on how to extended C<RenderView> in C<sub end>.
1032 =head2 Using The Default Template Name
1034 By default, C<Catalyst::View::TT> will look for a template that uses the
1035 same name as your controller action, allowing you to save the step of
1036 manually specifying the template name in each action. For example, this
1037 would allow us to remove the
1038 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1039 C<list> action in the Books controller. Open
1040 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1041 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1046 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1051 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1052 # 'Context' that's used to 'glue together' the various components
1053 # that make up the application
1054 my ($self, $c) = @_;
1056 # Retrieve all of the book records as book model objects and store in the
1057 # stash where they can be accessed by the TT template
1058 $c->stash->{books} = [$c->model('MyAppDB::Books')->all];
1060 # Set the TT template to use. You will almost always want to do this
1061 # in your action methods (actions methods respond to user input in
1062 # your controllers).
1063 #$c->stash->{template} = 'books/list.tt2';
1066 C<Catalyst::View::TT> defaults to looking for a template with no
1067 extension. In our case, we need to override this to look for an
1068 extension of C<.tt2>. Open C<lib/MyApp/View/TT.pm> and add the
1069 C<TEMPLATE_EXTENSION> definition as follows:
1071 __PACKAGE__->config({
1072 CATALYST_VAR => 'Catalyst',
1074 MyApp->path_to( 'root', 'src' ),
1075 MyApp->path_to( 'root', 'lib' )
1077 PRE_PROCESS => 'config/main',
1078 WRAPPER => 'site/wrapper',
1079 ERROR => 'error.tt2',
1081 TEMPLATE_EXTENSION => '.tt2',
1084 You should now be able to restart the development server as per the
1085 previous section and access the L<http://localhost:3000/books/list>
1088 B<NOTE:> Please note that if you use the default template technique,
1089 you will B<not> be able to use either the C<$c-E<gt>forward> or
1090 the C<$c-E<gt>detach> mechanisms (these are discussed in Part 2 and
1091 Part 9 of the Tutorial).
1094 =head2 Return To A Manually-Specified Template
1096 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1097 later in the tutorial, you should remove the comment from the
1098 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1100 $c->stash->{template} = 'books/list.tt2';
1102 Then delete the C<TEMPLATE_EXTENSION> line in
1103 C<lib/MyApp/View/TT.pm>.
1105 You should then be able to restart the development server and
1106 access L<http://localhost:3000/books/list> in the same manner as
1107 with earlier sections.
1112 Kennedy Clark, C<hkclark@gmail.com>
1114 Please report any errors, issues or suggestions to the author. The
1115 most recent version of the Catalyst Tutorial can be found at
1116 L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/Catalyst-Manual/lib/Catalyst/Manual/Tutorial/>.
1118 Copyright 2006, Kennedy Clark, under Creative Commons License
1119 (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).