3 Catalyst::Manual::Tutorial::CatalystBasics - Catalyst Tutorial - Part 2: Catalyst Application Development Basics
8 This is B<Part 2 of 9> for the Catalyst tutorial.
10 L<Tutorial Overview|Catalyst::Manual::Tutorial>
16 L<Introduction|Catalyst::Manual::Tutorial::Intro>
24 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>
28 L<Authentication|Catalyst::Manual::Tutorial::Authentication>
32 L<Authorization|Catalyst::Manual::Tutorial::Authorization>
36 L<Debugging|Catalyst::Manual::Tutorial::Debugging>
40 L<Testing|Catalyst::Manual::Tutorial::Testing>
44 L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
48 L<Appendices|Catalyst::Manual::Tutorial::Appendicies>
54 In this part of the tutorial, we will create a very basic Catalyst web
55 application. Though simple in many respects, this section will already
56 demonstrate a number of powerful capabilities such as:
60 =item * Helper Scripts
62 Catalyst helper scripts that can be used to rapidly bootstrap the
63 skeletal structure of an application.
67 Model/View/Controller (MVC) provides an architecture that facilitates a
68 clean "separation of control" between the different portions of your
69 application. Given that many other documents cover this subject in
70 detail, MVC will not be discussed in depth here (for an excellent
71 introduction to MVC and general Catalyst concepts, please see
72 L<Catalyst::Manual::About>. In short:
78 The model usually represents a data store. In most applications, the
79 model equates to the objects that are created from and saved to your SQL
84 The view takes model objects and renders them into something for the end
85 user to look at. Normally this involves a template-generation tool that
86 creates HTML for the user's web browser, but it could easily be code
87 that generates other forms such as PDF documents, e-mails, or Excel
92 As suggested by its name, the controller takes user requests and routes
93 them to the necessary model and view.
99 The use of Object-Relational Mapping (ORM) technology for database
100 access. Specifically, ORM provides an automated and standardized means
101 to persist and restore objects to/from a relational database.
105 B<TIP>: Note that all of the code for this part of the tutorial can be
106 pulled from the Catalyst Subversion repository in one step with the
109 svn checkout http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/Tutorial@###
110 IMPORTANT: Does not work yet. Will be completed for final version.
113 =head1 CREATE A CATALYST PROJECT
115 Catalyst provides a number of helper scripts that can be used to quickly
116 flesh out the basic structure of your application. All Catalyst projects
117 begin with the C<catalyst.pl> helper.
119 In the case of this tutorial, use the Catalyst C<catalyst.pl> script to
120 initialize the framework for an application called C<MyApp>:
125 The C<catalyst.pl> helper script will display the names of the
126 directories and files it creates.
128 Though it's too early for any significant celebration, we already have a
129 functioning application. Run the following command to run this
130 application with the built-in development web server:
132 $ script/myapp_server.pl
134 Point your web browser to L<http://localhost:3000> (substituting a
135 different hostname or IP address as appropriate) and you should be
136 greeted by the Catalyst welcome screen. Press Ctrl-C to break out of
137 the development server.
139 =head1 CREATE A SQLITE DATABASE
141 In this step, we make a text file with the required SQL commands to
142 create a database table and load some sample data. Open C<myapp01.sql>
143 in your editor and enter:
146 -- Create a very simple database to hold book and author information
149 id INTEGER PRIMARY KEY,
153 -- 'book_authors' is a many-to-many join table between books & authors
154 CREATE TABLE book_authors (
157 PRIMARY KEY (book_id, author_id)
159 CREATE TABLE authors (
160 id INTEGER PRIMARY KEY,
165 --- Load some sample data
167 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
168 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
169 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
170 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
171 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
172 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
173 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
174 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
175 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
176 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
177 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
178 INSERT INTO authors VALUES (7, ' Nathan', 'Torkington');
179 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
180 INSERT INTO book_authors VALUES (1, 1);
181 INSERT INTO book_authors VALUES (1, 2);
182 INSERT INTO book_authors VALUES (1, 3);
183 INSERT INTO book_authors VALUES (2, 4);
184 INSERT INTO book_authors VALUES (3, 5);
185 INSERT INTO book_authors VALUES (4, 6);
186 INSERT INTO book_authors VALUES (4, 7);
187 INSERT INTO book_authors VALUES (5, 8);
189 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
190 cutting and pasting example code from POD documents.
192 Then use the following command to build a C<myapp.db> SQLite database:
194 $ sqlite3 myapp.db < myapp01.sql
196 If you need to create the database more than once, you probably want to
197 issue the C<rm myapp.db> command to delete the database before you use
198 the C<sqlite3 myapp.db < myapp01.sql> command.
200 Once the C<myapp.db> database file has been created and initialized, you
201 can use the SQLite command line environment to do a quick dump of the
206 Enter ".help" for instructions
207 sqlite> select * from books;
208 1|CCSP SNRS Exam Certification Guide|5
209 2|TCP/IP Illustrated, Volume 1|5
210 3|Internetworking with TCP/IP Vol.1|4
212 5|Designing with Web Standards|5
218 $ sqlite3 myapp.db "select * from books"
219 1|CCSP SNRS Exam Certification Guide|5
220 2|TCP/IP Illustrated, Volume 1|5
221 3|Internetworking with TCP/IP Vol.1|4
223 5|Designing with Web Standards|5
225 As with most other SQL tools, if you are using the full "interactive"
226 environment you need to terminate your SQL commands with a ";" (it's not
227 required if you do a single SQL statement on the command line). Use
228 ".q" to exit from SQLite from the SQLite interactive mode and return to
229 your OS command prompt.
232 =head1 EDIT THE LIST OF CATALYST PLUGINS
234 One of the greatest benefits of Catalyst is that it has such a large
235 library of plugins available. Plugins are used to seamlessly integrate
236 existing Perl modules into the overall Catalyst framework. In general,
237 they do this by adding additional methods to the C<context> object
238 (generally written as C<$c>) that Catalyst passes to every component
239 throughout the framework.
241 By default, Catalyst enables three plugins/flags:
249 Enables the Catalyst debug output you saw when we started the
250 C<script/myapp_server.pl> development server earlier. You can remove
251 this plugin when you place your application into production.
253 As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
254 Although most of the items specified on the C<use Catalyst> line of your
255 application class will be plugins, Catalyst supports a limited number of
256 flag options (of these, C<-Debug> is the most common).
258 If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
263 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
265 C<ConfigLoader> provides an automatic way to load configurable
266 parameters for your application from a central YAML file (versus having
267 the values hard-coded inside your Perl modules). If you have not been
268 exposed to YAML before, it is a human-readable data serialization format
269 that can be used to read (and write) values to/from text files. We will
270 see how to use this feature of Catalyst during the authentication and
271 authorization sections (Part 4 and Part 5).
275 L<Catalyst::Plugin::Static::Simple>
277 C<Static::Simple> provides an easy method of serving static content such
278 as images and CSS files under the development server.
282 To modify the list of plugins, edit C<lib/MyApp.pm> (this file is
283 generally referred to as your I<application class>) and delete the line
286 use Catalyst qw/-Debug ConfigLoader Static::Simple/;
300 This tells Catalyst to start using three new plugins:
306 L<Catalyst::Plugin::Dumper>
308 Allows you to easily use L<Data::Dumper> to dump variables
309 to the logs, for example:
311 $c->log->dumper($myvar);
313 When running your application under the development server, the logs
314 will be printed to your screen along with the other debug information
315 generated by the C<-Debug> flag.
319 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>
321 Adds a stack trace to the standard Catalyst "debug screen" (this is the
322 screen Catalyst sends to your browser when an error occurs).
324 Note: L<Dumper|Catalyst::Plugin::Dumper> output appears on the console
325 window where you issue the C<script/myapp_server.pl> command.
326 L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
331 L<Catalyst::Plugin::DefaultEnd|Catalyst::Plugin::DefaultEnd>
333 Automatically provides a Catalyst "end action" that invokes your view at
334 the end of each request. Also allows you to add "dump_info=1" (precede
335 with "?" or "&" depending on where it is in the URL) to I<force> the
336 debug screen at the end of the Catalyst request processing cycle.
338 B<TIP>: Many Catalyst-related documents predate
339 L<DefaultEnd|Catalyst::Plugin::DefaultEnd> and suggest that you add an
340 C<end> action to your application class (C<MyApp.pm>) or Root.pm
341 (C<MyApp/Controller/Root.pm>). In most of these cases, you can convert
342 to L<DefaultEnd|Catalyst::Plugin::DefaultEnd> by deleting the C<end>
343 action and using the plugin instead.
347 Note that when specifying plugins on the C<use Catalyst> line, you can
348 omit C<Catalyst::Plugin> from the name. Additionally, you can spread
349 the plugin names across multiple lines as shown here, or place them all
350 on one (or more) lines as with the default configuration.
352 =head1 DATABASE ACCESS WITH C<DBIx::Class>
354 Catalyst can be used with virtually any form of persistent datastore
355 available via Perl. For example,
356 L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to easily
357 access databases through the traditional Perl DBI interface. However,
358 most Catalyst applications use some form of ORM technology to
359 automatically create and save model objects as they are used. Although
360 Tony Bowden's L<Class::DBI|Class::DBI> has been the traditional Perl ORM
361 engine, Matt Trout's L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC")
362 has rapidly emerged as the Perl-based ORM technology of choice. Most
363 new Catalyst applications rely on DBIC, as will this tutorial.
365 Note: See L<Catalyst::Model::CDBI| Catalyst:: Model::CDBI > for more
366 information on using Catalyst with L<Class::DBI|Class::DBI>. Catalyst
367 can also be used with "plain old DBI"; see L<Catalyst::Model::DBI|
368 Catalyst::Model::DBI>.
371 =head2 Create a DBIC Schema File
373 DBIx::Class uses a schema file to load other classes that represent the
374 tables in your database (DBIC refers to these "table objects" as "result
375 sources," see L<DBIx::Class::ResultSource|DBIx::Class::ResultSource>).
376 In this case, we want to load the model object for the C<books>,
377 C<book_authors>, and C<authors> tables created in the previous step.
379 Open C<lib/MyAppDB.pm> in your editor and insert:
385 MyAppDB -- DBIC Schema Class
389 # Our schema needs to inherit from 'DBIx::Class::Schema'
390 use base qw/DBIx::Class::Schema/;
392 # Need to load the DB Model classes here.
393 # You can use this syntax if you want:
394 # __PACKAGE__->load_classes(qw/Book BookAuthor Author/);
395 # Also, if you simply want to load all of the classes in a directory
396 # of the same name as your schema class (as we do here) you can use:
397 # __PACKAGE__->load_classes(qw//);
398 # But the variation below is more flexible in that it can be used to
399 # load from multiple namespaces.
400 __PACKAGE__->load_classes({
401 MyAppDB => [qw/Book BookAuthor Author/]
406 B<Note:> C<__PACKAGE__> is just a shorthand way of referencing the name
407 of the package where it is used. Therefore, in C<MyAppDB.pm>,
408 C<__PACKAGE> is equivalent to C<MyAppDB>
411 =head2 Create the DBIC "Result Source" Files
413 In this step, we create "table classes" (again, these are called a
414 "result source" classes in DBIC) that acts as model objects for the
415 C<books>, C<book_authors>, and C<authors> tables in our database.
417 First, create a directory to hold the class:
421 Then open C<lib/MyAppDB/Book.pm> in your editor and enter:
423 package MyAppDB::Book;
425 use base qw/DBIx::Class/;
427 # Load required DBIC stuff
428 __PACKAGE__->load_components(qw/PK::Auto Core/);
430 __PACKAGE__->table('books');
431 # Set columns in table
432 __PACKAGE__->add_columns(qw/id title rating/);
433 # Set the primary key for the table
434 __PACKAGE__->set_primary_key(qw/id/);
442 # 1) Name of relationship, DBIC will create accessor with this name
443 # 2) Name of the model class referenced by this relationship
444 # 3) Column name in *foreign* table
445 __PACKAGE__->has_many(book_authors => 'MyAppDB::BookAuthor', 'book_id');
449 # 1) Name of relationship, DBIC will create accessor with this name
450 # 2) Name of has_many() relationship this many_to_many() is shortcut for
451 # 3) Name of belongs_to() relationship in model class of has_many() above
452 # You must already have the has_many() defined to use a many_to_many().
453 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
458 MyAppDB::Book - A model object representing a book.
462 This is an object that represents a row in the 'books' table of your application
463 database. It uses DBIx::Class (aka, DBIC) to do ORM.
465 For Catalyst, this is designed to be used through MyApp::Model::MyAppDB.
466 Offline utilities may wish to use this class directly.
472 This defines both a C<has_many> and a C<many_to_many> relationship. The
473 C<many_to_many> relationship is optional, but it makes it easier to map
474 a book to its collection of authors. Without it, we would have to
475 "walk" though the C<book_authors> table as in
476 C<$book-E<gt>book_authors-E<gt>first-E<gt>author-E<gt>last_name> (we
477 will see examples on how to use DBIC objects in your code soon, but note
478 that because C<$book-E<gt>book_authors> can return multiple authors, we
479 have to use C<first> to display a single author). C<many_to_many>
480 allows us to use the shorter
481 C<$book-E<gt>authors-E<gt>first-E<gt>last_name>. Note that you cannot
482 define a C<many_to_many> relationship without also having the
483 C<has_many> relationship in place.
485 Next, open C<lib/MyAppDB/Author.pm> in your editor and enter:
487 package MyAppDB::Author;
489 use base qw/DBIx::Class/;
491 # Load required DBIC stuff
492 __PACKAGE__->load_components(qw/PK::Auto Core/);
494 __PACKAGE__->table('authors');
495 # Set columns in table
496 __PACKAGE__->add_columns(qw/id first_name last_name/);
497 # Set the primary key for the table
498 __PACKAGE__->set_primary_key(qw/id/);
506 # 1) Name of relationship, DBIC will create accessor with this name
507 # 2) Name of the model class referenced by this relationship
508 # 3) Column name in *foreign* table
509 __PACKAGE__->has_many(book_author => 'MyAppDB::BookAuthor', 'author_id');
513 # 1) Name of relationship, DBIC will create accessor with this name
514 # 2) Name of has_many() relationship this many_to_many() is shortcut for
515 # 3) Name of belongs_to() relationship in model class of has_many() above
516 # You must already have the has_many() defined to use a many_to_many().
517 __PACKAGE__->many_to_many(books => 'book_author', 'book');
522 MyAppDB::Author - A model object representing an author of a book (if a book has
523 multiple authors, each will be represented be separate Author object).
527 This is an object that represents a row in the 'authors' table of your application
528 database. It uses DBIx::Class (aka, DBIC) to do ORM.
530 For Catalyst, this is designed to be used through MyApp::Model::MyAppDB.
531 Offline utilities may wish to use this class directly.
537 Finally, open C<lib/MyAppDB/BookAuthor.pm> in your editor and enter:
539 package MyAppDB::BookAuthor;
541 use base qw/DBIx::Class/;
543 # Load required DBIC stuff
544 __PACKAGE__->load_components(qw/PK::Auto Core/);
546 __PACKAGE__->table('book_authors');
547 # Set columns in table
548 __PACKAGE__->add_columns(qw/book_id author_id/);
549 # Set the primary key for the table
550 __PACKAGE__->set_primary_key(qw/book_id author_id/);
558 # 1) Name of relationship, DBIC will create accessor with this name
559 # 2) Name of the model class referenced by this relationship
560 # 3) Column name in *this* table
561 __PACKAGE__->belongs_to(book => 'MyAppDB::Book', 'book_id');
565 # 1) Name of relationship, DBIC will create accessor with this name
566 # 2) Name of the model class referenced by this relationship
567 # 3) Column name in *this* table
568 __PACKAGE__->belongs_to(author => 'MyAppDB::Author', 'author_id');
573 MyAppDB::BookAuthor - A model object representing the JOIN between an author and
578 This is an object that represents a row in the 'book_authors' table of your
579 application database. It uses DBIx::Class (aka, DBIC) to do ORM.
581 You probably won't need to use this class directly -- it will be automatically
582 used by DBIC where joins are needed.
584 For Catalyst, this is designed to be used through MyApp::Model::MyAppDB.
585 Offline utilities may wish to use this class directly.
591 B<Note:> This sample application uses a plural form for the database
592 tables (e.g., C<books> and C<authors>) and a singular form for the model
593 objects (e.g., C<Book> and C<Author>); however, Catalyst places no
594 restrictions on the naming conventions you wish to use.
597 =head2 Use C<Catalyst::Model::DBIC::Schema> To Load The Model Class
599 When L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> is
600 in use, Catalyst essentially reads an existing copy of your database
601 model and creates a new set of objects under C<MyApp::Model> for use
605 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> you
606 essentially end up with two sets of model classes (only one of which you
607 write... the other set is created automatically in memory when your
608 Catalyst application initializes). For this tutorial application, the
609 important points to remember are: you write the I<result source> files
610 in C<MyAppDB>, but I<within Catalyst> you use the I<automatically
611 created model classes> in C<MyApp::Model>.
613 Use the L<Catalyst::Helper::Model::DBIC::Schema|
614 Catalyst::Helper::Model::DBIC::Schema > helper script to create the
615 model class that loads up the model we created in the previous step:
617 $ script/myapp_create.pl model MyAppDB DBIC::Schema MyAppDB dbi:SQLite:myapp.db '' '' '{ AutoCommit => 1 }'
619 Where the first C<MyAppDB> is the name of the class to be created by the
620 helper in C<lib/MyApp/Model> and the second C<MyAppDB> is the name of
621 existing schema file we created (in C<lib/MyAppDB.pm>). You can see
622 that the helper creates a model file under C<lib/MyApp/Model> (Catalyst
623 has a separate directory under C<lib/MyApp> for each of the three parts
624 of MVC: C<Model>, C<View>, and C<Controller> [although older Catalyst
625 applications often use the directories C<M>, C<V>, and C<C>]).
629 =head1 CREATE A CATALYST CONTROLLER
631 Controllers are where you write methods that respond to C<GET> and C<POST> messages from the user's web browser.
633 Use the Catalyst C<create> script to add a controller for book-related actions:
635 $ script/myapp_create.pl controller Books
637 Then edit C<lib/MyApp/Controller/Books.pm> and add the following method
642 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
647 # Retrieve the usual perl OO '$self' for this object. $c is the Catalyst
648 # 'Context' that's used to 'glue together' the various components
649 # that make up the application
652 # Retrieve all of the book records as book model objects and store in the
653 # stash where they can be accessed by the TT template
654 $c->stash->{books} = [$c->model('MyAppDB::Book')->all];
656 # Set the TT template to use. You will almost always want to do this
657 # in your action methods.
658 $c->stash->{template} = 'books/list.tt2';
661 B<Note:> Programmers experienced with object-oriented Perl should
662 recognize C<$self> as a reference to the object where this method was
663 called. On the other hand, C<$c> will be new to many Perl programmers
664 who have not used Catalyst before (it's sometimes written as
665 C<$context>). The Context object is automatically passed to all
666 Catalyst components. It is used to pass information between components
667 and provide access to Catalyst and plugin functionality.
669 B<TIP>: You may see the C<$c-E<gt>model('MyAppDB::Book')> used above
670 written as C<$c-E<gt>model('MyAppDB')-E<gt>resultset('Book)>. The two
673 B<Note:> Catalyst actions are regular Perl methods, but they make use of
674 Nicholas Clark's C<attributes> module to provide additional information
675 to the Catalyst dispatcher logic.
678 =head1 CATALYST VIEWS
680 Views are where you render output for display in the user's web browser
681 (or possibly using other display technology). As with virtually every
682 aspect of Catalyst, options abound when it comes to the specific view
683 technology you adopt inside your application. However, most Catalyst
684 applications use the Template Toolkit, known as TT (for more information
685 on TT, see L<http://www.template-toolkit.org>). Other popular View
686 technologies include Mason (L<http://www.masonhq.com> and
687 L<http://www.masonbook.com>) and L<HTML::Template|HTML::Template>
688 (L<http://html-template.sourceforge.net>).
691 =head2 Create a Catalyst View Using C<TTSITE>
693 When using TT for the Catalyst view, there are two main helper scripts:
699 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
703 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
707 Both are similar, but C<TT> merely creates the C<lib/MyApp/View/TT.pm>
708 file and leaves the creation of any hierarchical template organization
709 entirely up to you (it also creates a C<t/view_TT.t> file for testing;
710 test cases will be discussed in Part 7). Conversely, the C<TTSite>
711 helper creates a modular and hierarchical view layout with separate
712 Template Toolkit (TT) files for common header and footer information,
713 configuration values, a CSS stylesheet, etc.
715 Enter the following command to enable the C<TTSite> style of view
716 rendering for the tutorial:
718 $ script/myapp_create.pl view TT TTSite
720 This puts a number of files in the C<root/lib> and C<root/src>
721 directories that can be used to customize the look and feel of your
722 application. Also take a look at C<lib/MyApp/View/TT.pm> for config
723 values set by the C<TTSite> helper.
725 B<TIP>: Note that TTSite does one thing that could confuse people who
726 are used to the normal C<TT> Catalyst View: it redefines the Catalyst
727 context object in templates from its usual C<c> to C<Catalyst>. Also
728 keep this in mind when looking at other Catalyst examples (they almost
729 always use C<c>). Note that Catalyst and TT I<do not complain> when you
730 use the wrong name to access the context... it simply outputs blanks for
731 that bogus logic. Finally, be aware that this change in name I<only>
732 applies to how the context object is accessed inside your TT templates,
733 your controllers will continue to use C<$c> (or whatever name you use
734 when fetching the reference from C<@_> inside your methods). (You can
735 change back to the "default" behavior be removing the C<CATALYST_VAR>
736 line from C<lib/MyApp/View/TT.pm>, but you will also have to edit
737 C<root/lib/config/main> and C<root/lib/config/url>. If you do this, be
738 careful not to have a collision between your own C<c> variable and the
739 Catalyst C<c> variable.)
743 =head2 Globally Customize Every View
745 When using TTSite, files in the subdirectories of C<root/lib> can be
746 used to make changes that will appear in every view. For example, to
747 display optional status and error messages in every view, edit
748 C<root/lib/site/layout> update it to match the following (the two HTML
749 C<span> elements are new):
751 <div id="header">[% PROCESS site/header %]</div>
754 <span class="message">[% status_msg %]</span>
755 <span class="error">[% error_msg %]</span>
759 <div id="footer">[% PROCESS site/footer %]</div>
761 If we set either message in the Catalyst stash (e.g.,
762 C<$c-E<gt>stash-E<gt>{status_msg} = 'Hello world'>) it will be displayed
763 whenever any view used by that request is rendered. The C<message> and
764 C<error> CSS styles are automatically defined in C<root/src/ttsite.css>
765 and can be customized to suit your needs.
767 B<Note:> The Catalyst stash only lasts for a single HTTP request. If
768 you need to retain information across requests you can use
769 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
770 Catalyst sessions in the Authentication part).
773 =head2 Create a TT Template Page
775 To add a new page of content to the TTSite view hierarchy, just create a
776 new C<.tt2> file in C<root/src>. Only include HTML markup that goes
777 inside the HTML <body> and </body> tags, TTSite will use the contents of
778 C<root/lib/site> to add the top and bottom.
780 First create a directory for book-related TT templates:
782 $ mkdir root/src/books
784 Then open C<root/src/books/list.tt2> in your editor and enter:
786 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
787 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
788 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
789 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
791 [% # Provide a title to root/lib/site/header -%]
792 [% META title = 'Book List' -%]
795 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
796 [% # Display each book in a table row %]
797 [% FOREACH book IN books -%]
799 <td>[% book.title %]</td>
800 <td>[% book.rating %]</td>
802 [% # Print author count in parens. 'book.authors' uses the 'many_to_many' -%]
803 [% # relationship to retrieve all of the authors of a book. 'size' is a -%]
804 [% # TT VMethod to get the number of elements in a list. -%]
805 ([% book.authors.size %])
806 [% # Use an alternate form of a FOREACH loop to display authors. -%]
807 [% # _ below is the TT string concatenation operator. -%]
808 [% author.last_name _' ' FOREACH author = book.authors %]
809 [% # Note: if many_to_many relationship not used in Authors.pm, you could -%]
810 [% # have used the following to 'walk' through the 'join table objects' -%]
811 [% # bk_author.author.last_name _' ' FOREACH bk_author = book.book_authors %]
817 As indicated by the inline comments above, the C<META title> line uses
818 TT's META feature to provide a title to C<root/lib/site/header>.
819 Meanwhile, the outer C<FOREACH> loop iterates through each C<book> model
820 object and prints the C<title> and C<rating> fields. An inner
821 C<FOREACH> loop prints the last name of each author in a single table
822 cell (a simple space is used between the names; in reality you would
823 probably want to modify the code to use a comma as a separator).
825 If you are new to TT, the [% and %] tags are used to delimit "variable
826 text". TT supports a wide variety of directives for "calling" other
827 files, looping, conditional logic, etc. In general, TT simplifies the
828 usual range of Perl operators down to the single dot (C<.>) operator.
829 This applies to operations as diverse as method calls, hash lookups, and
830 list index values (see
831 L<http://www.template-toolkit.org/docs/default/Manual/Variables.html>
832 for details and examples). In addition to the usual C<Template> module
833 Pod documentation, you can access the TT manual at
834 L<http://www.template-toolkit.org/docs/default/>.
836 B<NOTE>: The C<TTSite> helper creates several TT files using an
837 extension of C<.tt2>. Most other Catalyst and TT examples use an
838 extension of C<.tt>. You can use either extension (or no extension at
839 all) with TTSite and TT, just be sure to use the appropriate extension
840 for both the file itself I<and> the C<$c-E<gt>stash-E<gt>{template} =
841 ...> line in your controller. This document will use C<.tt2> for
842 consistency with the files already created by the C<TTSite> helper.
846 =head1 RUN THE APPLICATION
848 First, let's enable an environment variable option that causes
849 DBIx::Class to dump the SQL statements it's using to access the database
850 (this option can provide extremely helpful troubleshooting information):
852 $ export DBIX_CLASS_STORAGE_DBI_DEBUG=1
854 B<NOTE>: You can also set this in your code using
855 C<$class-E<gt>storage-E<gt>debug(1);>. See
856 L<DBIx::Class::Manual::Troubleshooting|DBIx::Class::Manual::Troubleshooting>
857 for details (including options to log to file vs. the Catalyst
858 development server log.
860 Then run the Catalyst "demo server" script:
862 $ script/myapp_server.pl
864 You should get something like this:
866 $ script/myapp_server.pl
867 [Tue May 16 12:51:33 2006] [catalyst] [debug] Debug messages enabled
868 [Tue May 16 12:51:33 2006] [catalyst] [debug] Loaded plugins:
869 .------------------------------------------------------------------------------.
870 | Catalyst::Plugin::ConfigLoader 0.07 |
871 | Catalyst::Plugin::Static::Simple 0.14 |
872 | Catalyst::Plugin::Dumper 0.000002 |
873 | Catalyst::Plugin::StackTrace 0.04 |
874 | Catalyst::Plugin::DefaultEnd 0.06 |
875 '------------------------------------------------------------------------------'
877 [Tue May 16 12:51:33 2006] [catalyst] [debug] Loaded dispatcher "Catalyst::Dispatcher"
878 [Tue May 16 12:51:33 2006] [catalyst] [debug] Loaded engine "Catalyst::Engine::HTTP"
879 [Tue May 16 12:51:33 2006] [catalyst] [debug] Found home "/home/me/MyApp"
880 [Tue May 16 12:51:37 2006] [catalyst] [debug] Loaded components:
881 .-------------------------------------------------------------------+----------.
883 +-------------------------------------------------------------------+----------+
884 | MyApp::Controller::Books | instance |
885 | MyApp::Controller::Root | instance |
886 | MyApp::Model::MyAppDB | instance |
887 | MyApp::Model::MyAppDB::Author | class |
888 | MyApp::Model::MyAppDB::Book | class |
889 | MyApp::Model::MyAppDB::BookAuthor | class |
890 | MyApp::View::TT | instance |
891 '-------------------------------------------------------------------+----------'
893 [Tue May 16 12:51:37 2006] [catalyst] [debug] Loaded Private actions:
894 .----------------------+----------------------------------------+--------------.
895 | Private | Class | Method |
896 +----------------------+----------------------------------------+--------------+
897 | /default | MyApp::Controller::Root | default |
898 | /end | MyApp | end |
899 | /books/list | MyApp::Controller::Books | list |
900 '----------------------+----------------------------------------+--------------'
902 [Tue May 16 12:51:37 2006] [catalyst] [debug] Loaded Path actions:
903 .--------------------------------------+---------------------------------------.
905 +--------------------------------------+---------------------------------------+
906 | /books/list | /books/list |
907 '--------------------------------------+---------------------------------------'
909 [Tue May 16 12:51:37 2006] [catalyst] [info] MyApp powered by Catalyst 5.6902
910 You can connect to your server at http://localhost:3000
912 Some things you should note in the output above:
918 Catalyst::Model::DBIC::Schema took our C<MyAppDB::Book> and made it
919 C<MyApp::Model::MyAppDB::Book> (and similar actions were performed on
920 C<MyAppDB::Author> and C<MyAppDB::BookAuthor>).
924 The "list" action in our Books controller showed up with a path of
930 Point your browser to L<http://localhost:3000> and you should still get
931 the Catalyst welcome page.
933 Next, to view the book list, change the URL in your browser to
934 L<http://localhost:3000/books/list>. You should get a list of the five
935 books loaded by the C<myapp01.sql> script above, with TTSite providing
936 the formatting for the very simple output we generated in our template.
937 The count and space-separated list of author last names appear on the
940 Also notice in the output of the C<script/myapp_server.pl> that DBIC
941 used the following SQL to retrieve the data:
943 SELECT me.id, me.title, me.rating FROM books me
945 Along with a list of the following commands to retrieve the authors for
946 each book (the lines have been "word wrapped" here to improve
949 SELECT author.id, author.first_name, author.last_name
951 JOIN authors author ON ( author.id = me.author_id )
952 WHERE ( me.book_id = ? ): `1'
954 You should see 10 such lines of debug output, two for each of the five
955 author_id values (it pulls the data once for the count logic and another
956 time to actually display the list).
961 Kennedy Clark, C<hkclark@gmail.com>
963 Please report any errors, issues or suggestions to the author.
965 Copyright 2006, Kennedy Clark, under Creative Commons License (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).