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<$c>) that Catalyst passes to every component
239 throughout the framework.
241 By default, Catalyst enables three plugins/flags:
249 Enables the Catalyst debug output you saw when we started the
250 C<script/myapp_server.pl> development server earlier. You can remove
251 this plugin when you place your application into production.
253 As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
254 Although most of the items specified on the C<use Catalyst> line of your
255 application class will be plugins, Catalyst supports a limited number of
256 flag options (of these, C<-Debug> is the most common). See the
257 documentation for C<Catalyst.pm> to get details on other flags
258 (currently C<-Engine>, C<-Home>, and C<-Log>).
260 If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
265 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
267 C<ConfigLoader> provides an automatic way to load configurable
268 parameters for your application from a central YAML file (versus having
269 the values hard-coded inside your Perl modules). If you have not been
270 exposed to YAML before, it is a human-readable data serialization format
271 that can be used to read (and write) values to/from text files. We will
272 see how to use this feature of Catalyst during the authentication and
273 authorization sections (Part 4 and Part 5).
277 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
279 C<Static::Simple> provides an easy method of serving static content such
280 as images and CSS files under the development server.
284 To modify the list of plugins, edit C<lib/MyApp.pm> (this file is
285 generally referred to as your I<application class>) and delete the line
288 use Catalyst qw/-Debug ConfigLoader Static::Simple/;
301 This tells Catalyst to start using two new plugins:
307 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>
309 Adds a stack trace to the standard Catalyst "debug screen" (this is the
310 screen Catalyst sends to your browser when an error occurs).
312 Note: L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
313 browser, not in the console window from which you're running your
314 application, which is where logging output usually goes.
318 L<Catalyst::Plugin::DefaultEnd|Catalyst::Plugin::DefaultEnd>
320 Automatically provides a Catalyst "end action" that invokes your view at
321 the end of each request. Also allows you to add "dump_info=1" (precede
322 with "?" or "&" depending on where it is in the URL) to I<force> the
323 debug screen at the end of the Catalyst request processing cycle.
325 B<TIP>: Many Catalyst-related documents predate
326 L<DefaultEnd|Catalyst::Plugin::DefaultEnd> and suggest that you add an
327 C<end> action to your application class (C<MyApp.pm>) or Root.pm
328 (C<MyApp/Controller/Root.pm>). In most of these cases, you can convert
329 to L<DefaultEnd|Catalyst::Plugin::DefaultEnd> by deleting the C<end>
330 action and using the plugin instead. There are certainly cases when
331 you'd want to write your own custom C<end> action, but for most
332 circumstances, DefaultEnd will be exactly what you want.
336 Note that when specifying plugins on the C<use Catalyst> line, you can
337 omit C<Catalyst::Plugin::> from the name. Additionally, you can spread
338 the plugin names across multiple lines as shown here, or place them all
339 on one (or more) lines as with the default configuration.
341 =head1 DATABASE ACCESS WITH C<DBIx::Class>
343 Catalyst can be used with virtually any form of persistent datastore
344 available via Perl. For example,
345 L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to
346 easily access databases through the traditional Perl C<DBI> interface.
347 However, most Catalyst applications use some form of ORM technology to
348 automatically create and save model objects as they are used. Although
349 Tony Bowden's L<Class::DBI|Class::DBI> has been the traditional
350 Perl ORM engine, Matt Trout's L<DBIx::Class|DBIx::Class> (abbreviated
351 as "DBIC") has rapidly emerged as the Perl-based ORM technology of choice.
352 Most new Catalyst applications rely on DBIC, as will this tutorial.
354 Note: See L<Catalyst:: Model::CDBI> for more information on using
355 Catalyst with L<Class::DBI|Class::DBI>.
357 =head2 Create a DBIC Schema File
359 DBIx::Class uses a schema file to load other classes that represent the
360 tables in your database (DBIC refers to these "table objects" as "result
361 sources"; see L<DBIx::Class::ResultSource>). In this case, we want to
362 load the model object for the C<books>, C<book_authors>, and C<authors>
363 tables created in the previous step.
365 Open C<lib/MyAppDB.pm> in your editor and insert:
371 MyAppDB - DBIC Schema Class
375 # Our schema needs to inherit from 'DBIx::Class::Schema'
376 use base qw/DBIx::Class::Schema/;
378 # Need to load the DB Model classes here.
379 # You can use this syntax if you want:
380 # __PACKAGE__->load_classes(qw/Book BookAuthor Author/);
381 # Also, if you simply want to load all of the classes in a directory
382 # of the same name as your schema class (as we do here) you can use:
383 # __PACKAGE__->load_classes(qw//);
384 # But the variation below is more flexible in that it can be used to
385 # load from multiple namespaces.
386 __PACKAGE__->load_classes({
387 MyAppDB => [qw/Book BookAuthor Author/]
392 B<Note:> C<__PACKAGE__> is just a shorthand way of referencing the name
393 of the package where it is used. Therefore, in C<MyAppDB.pm>,
394 C<__PACKAGE__> is equivalent to C<MyAppDB>.
397 =head2 Create the DBIC "Result Source" Files
399 In this step, we create "table classes" (again, these are called a
400 "result source" classes in DBIC) that act as model objects for the
401 C<books>, C<book_authors>, and C<authors> tables in our database.
403 First, create a directory to hold the class:
407 Then open C<lib/MyAppDB/Book.pm> in your editor and enter:
409 package MyAppDB::Book;
411 use base qw/DBIx::Class/;
413 # Load required DBIC stuff
414 __PACKAGE__->load_components(qw/PK::Auto Core/);
416 __PACKAGE__->table('books');
417 # Set columns in table
418 __PACKAGE__->add_columns(qw/id title rating/);
419 # Set the primary key for the table
420 __PACKAGE__->set_primary_key(qw/id/);
428 # 1) Name of relationship, DBIC will create accessor with this name
429 # 2) Name of the model class referenced by this relationship
430 # 3) Column name in *foreign* table
431 __PACKAGE__->has_many(book_authors => 'MyAppDB::BookAuthor', 'book_id');
435 # 1) Name of relationship, DBIC will create accessor with this name
436 # 2) Name of has_many() relationship this many_to_many() is shortcut for
437 # 3) Name of belongs_to() relationship in model class of has_many() above
438 # You must already have the has_many() defined to use a many_to_many().
439 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
444 MyAppDB::Book - A model object representing a book.
448 This is an object that represents a row in the 'books' table of your application
449 database. It uses DBIx::Class (aka, DBIC) to do ORM.
451 For Catalyst, this is designed to be used through MyApp::Model::MyAppDB.
452 Offline utilities may wish to use this class directly.
458 This defines both a C<has_many> and a C<many_to_many> relationship. The
459 C<many_to_many> relationship is optional, but it makes it easier to map
460 a book to its collection of authors. Without it, we would have to
461 "walk" though the C<book_authors> table as in
462 C<$book-E<gt>book_authors-E<gt>first-E<gt>author-E<gt>last_name> (we
463 will see examples on how to use DBIC objects in your code soon, but note
464 that because C<$book-E<gt>book_authors> can return multiple authors, we
465 have to use C<first> to display a single author). C<many_to_many> allows
466 us to use the shorter C<$book-E<gt>authors-E<gt>first-E<gt>last_name>.
467 Note that you cannot define a C<many_to_many> relationship without also
468 having the C<has_many> relationship in place.
470 Next, open C<lib/MyAppDB/Author.pm> in your editor and enter:
472 package MyAppDB::Author;
474 use base qw/DBIx::Class/;
476 # Load required DBIC stuff
477 __PACKAGE__->load_components(qw/PK::Auto Core/);
479 __PACKAGE__->table('authors');
480 # Set columns in table
481 __PACKAGE__->add_columns(qw/id first_name last_name/);
482 # Set the primary key for the table
483 __PACKAGE__->set_primary_key(qw/id/);
491 # 1) Name of relationship, DBIC will create accessor with this name
492 # 2) Name of the model class referenced by this relationship
493 # 3) Column name in *foreign* table
494 __PACKAGE__->has_many(book_author => 'MyAppDB::BookAuthor', 'author_id');
498 # 1) Name of relationship, DBIC will create accessor with this name
499 # 2) Name of has_many() relationship this many_to_many() is shortcut for
500 # 3) Name of belongs_to() relationship in model class of has_many() above
501 # You must already have the has_many() defined to use a many_to_many().
502 __PACKAGE__->many_to_many(books => 'book_author', 'book');
507 MyAppDB::Author - A model object representing an author of a book (if a book has
508 multiple authors, each will be represented be separate Author object).
512 This is an object that represents a row in the 'authors' table of your application
513 database. It uses DBIx::Class (aka, DBIC) to do ORM.
515 For Catalyst, this is designed to be used through MyApp::Model::MyAppDB.
516 Offline utilities may wish to use this class directly.
522 Finally, open C<lib/MyAppDB/BookAuthor.pm> in your editor and enter:
524 package MyAppDB::BookAuthor;
526 use base qw/DBIx::Class/;
528 # Load required DBIC stuff
529 __PACKAGE__->load_components(qw/PK::Auto Core/);
531 __PACKAGE__->table('book_authors');
532 # Set columns in table
533 __PACKAGE__->add_columns(qw/book_id author_id/);
534 # Set the primary key for the table
535 __PACKAGE__->set_primary_key(qw/book_id author_id/);
543 # 1) Name of relationship, DBIC will create accessor with this name
544 # 2) Name of the model class referenced by this relationship
545 # 3) Column name in *this* table
546 __PACKAGE__->belongs_to(book => 'MyAppDB::Book', 'book_id');
550 # 1) Name of relationship, DBIC will create accessor with this name
551 # 2) Name of the model class referenced by this relationship
552 # 3) Column name in *this* table
553 __PACKAGE__->belongs_to(author => 'MyAppDB::Author', 'author_id');
558 MyAppDB::BookAuthor - A model object representing the JOIN between an author and
563 This is an object that represents a row in the 'book_authors' table of your
564 application database. It uses DBIx::Class (aka, DBIC) to do ORM.
566 You probably won't need to use this class directly -- it will be automatically
567 used by DBIC where joins are needed.
569 For Catalyst, this is designed to be used through MyApp::Model::MyAppDB.
570 Offline utilities may wish to use this class directly.
576 B<Note:> This sample application uses a plural form for the database
577 tables (e.g., C<books> and C<authors>) and a singular form for the model
578 objects (e.g., C<Book> and C<Author>); however, Catalyst places no
579 restrictions on the naming conventions you wish to use.
581 =head2 Use C<Catalyst::Model::DBIC::Schema> To Load The Model Class
583 When L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> is
584 in use, Catalyst essentially reads an existing copy of your database
585 model and creates a new set of objects under C<MyApp::Model> for use
589 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> you
590 essentially end up with two sets of model classes (only one of which
591 you write... the other set is created automatically in memory when
592 your Catalyst application initializes). For this tutorial application,
593 the important points to remember are: you write the I<result source>
594 files in C<MyAppDB>, but I<within Catalyst> you use the I<automatically
595 created model classes> in C<MyApp::Model>.
598 L<Catalyst::Helper::Model::DBIC::Schema|Catalyst::Helper::Model::DBIC::Schema>
599 helper script to create the model class that loads up the model we
600 created in the previous step:
602 $ script/myapp_create.pl model MyAppDB DBIC::Schema MyAppDB dbi:SQLite:myapp.db '' '' '{ AutoCommit => 1 }'
604 Where the first C<MyAppDB> is the name of the class to be created by the
605 helper in C<lib/MyApp/Model> and the second C<MyAppDB> is the name of
606 existing schema file we created (in C<lib/MyAppDB.pm>). You can see
607 that the helper creates a model file under C<lib/MyApp/Model> (Catalyst
608 has a separate directory under C<lib/MyApp> for each of the three parts
609 of MVC: C<Model>, C<View>, and C<Controller> [although older Catalyst
610 applications often use the directories C<M>, C<V>, and C<C>]).
613 =head1 CREATE A CATALYST CONTROLLER
615 Controllers are where you write methods that interact with user
616 input--typically, controller methods respond to C<GET> and C<POST>
617 messages from the user's web browser.
619 Use the Catalyst C<create> script to add a controller for book-related
622 $ script/myapp_create.pl controller Books
624 Then edit C<lib/MyApp/Controller/Books.pm> and add the following method
629 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
634 # Retrieve the usual perl OO '$self' for this object. $c is the Catalyst
635 # 'Context' that's used to 'glue together' the various components
636 # that make up the application
639 # Retrieve all of the book records as book model objects and store in the
640 # stash where they can be accessed by the TT template
641 $c->stash->{books} = [$c->model('MyAppDB::Book')->all];
643 # Set the TT template to use. You will almost always want to do this
644 # in your action methods.
645 $c->stash->{template} = 'books/list.tt2';
648 B<Note:> Programmers experienced with object-oriented Perl should
649 recognize C<$self> as a reference to the object where this method was
650 called. On the other hand, C<$c> will be new to many Perl programmers
651 who have not used Catalyst before (it's sometimes written as
652 C<$context>). The Context object is automatically passed to all
653 Catalyst components. It is used to pass information between components
654 and provide access to Catalyst and plugin functionality.
656 B<TIP>: You may see the C<$c-E<gt>model('MyAppDB::Book')> used above
657 written as C<$c-E<gt>model('MyAppDB')-E<gt>resultset('Book)>. The two
660 B<Note:> Catalyst actions are regular Perl methods, but they make use of
661 Nicholas Clark's C<attributes> module (that's the C<: Local> next to the
662 C<sub list> in the code above) to provide additional information to the
663 Catalyst dispatcher logic.
665 =head1 CATALYST VIEWS
667 Views are where you render output, typically for display in the user's
668 web browser, but also possibly using other display output-generation
669 systems. As with virtually every aspect of Catalyst, options abound
670 when it comes to the specific view technology you adopt inside your
671 application. However, most Catalyst applications use the Template
672 Toolkit, known as TT (for more information on TT, see
673 L<http://www.template-toolkit.org>). Other popular View technologies
674 include Mason (L<http://www.masonhq.com> and
675 L<http://www.masonbook.com>) and L<HTML::Template|HTML::Template>
676 (L<http://html-template.sourceforge.net>).
678 =head2 Create a Catalyst View Using C<TTSITE>
680 When using TT for the Catalyst view, there are two main helper scripts:
686 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
690 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
694 Both are similar, but C<TT> merely creates the C<lib/MyApp/View/TT.pm>
695 file and leaves the creation of any hierarchical template organization
696 entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
697 test cases will be discussed in Part 7). The C<TTSite> helper creates a
698 modular and hierarchical view layout with separate Template Toolkit (TT)
699 files for common header and footer information, configuration values, a
700 CSS stylesheet, and more.
702 Enter the following command to enable the C<TTSite> style of view
703 rendering for this tutorial:
705 $ script/myapp_create.pl view TT TTSite
707 This puts a number of files in the C<root/lib> and C<root/src>
708 directories that can be used to customize the look and feel of your
709 application. Also take a look at C<lib/MyApp/View/TT.pm> for config
710 values set by the C<TTSite> helper.
712 B<TIP>: Note that TTSite does one thing that could confuse people who
713 are used to the normal C<TT> Catalyst View: it redefines the Catalyst
714 context object in templates from its usual C<c> to C<Catalyst>. When
715 looking at other Catalyst examples, remember that they almost always use
716 C<c>. Note that Catalyst and TT I<do not complain> when you use the
717 wrong name to access the context object...TT simply outputs blanks for
718 that bogus logic (see next tip to change this behavior with TT C<DEBUG>
719 options). Finally, be aware that this change in name I<only>
720 applies to how the context object is accessed inside your TT templates;
721 your controllers will continue to use C<$c> (or whatever name you use
722 when fetching the reference from C<@_> inside your methods). (You can
723 change back to the "default" behavior be removing the C<CATALYST_VAR>
724 line from C<lib/MyApp/View/TT.pm>, but you will also have to edit
725 C<root/lib/config/main> and C<root/lib/config/url>. If you do this, be
726 careful not to have a collision between your own C<c> variable and the
727 Catalyst C<c> variable.)
729 B<TIP>: When troubleshooting TT it can be helpful to enable variable
730 C<DEBUG> options. You can do this in a Catalyst environment by adding
731 a C<DEBUG> line to the C<__PACKAGE__->config> declaration in
734 __PACKAGE__->config({
735 CATALYST_VAR => 'Catalyst',
741 There are a variety of options you can use, such as 'undef', 'all',
742 'service', 'context', 'parser', 'provider', and 'service'. See
743 L<Template::Constants> for more information (remove the C<DEBUG_>
744 portion of the name shown in the TT docs and convert to lower case
745 for use inside Catalyst).
748 =head2 Globally Customize Every View
750 When using TTSite, files in the subdirectories of C<root/lib> can be
751 used to make changes that will appear in every view. For example, to
752 display optional status and error messages in every view, edit
753 C<root/lib/site/layout>, updating it to match the following (the two HTML
754 C<span> elements are new):
756 <div id="header">[% PROCESS site/header %]</div>
759 <span class="message">[% status_msg %]</span>
760 <span class="error">[% error_msg %]</span>
764 <div id="footer">[% PROCESS site/footer %]</div>
766 If we set either message in the Catalyst stash (e.g.,
767 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it will
768 be displayed whenever any view used by that request is rendered. The
769 C<message> and C<error> CSS styles are automatically defined in
770 C<root/src/ttsite.css> and can be customized to suit your needs.
772 B<Note:> The Catalyst stash only lasts for a single HTTP request. If
773 you need to retain information across requests you can use
774 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
775 Catalyst sessions in the Authentication part of the tutorial).
778 =head2 Create a TT Template Page
780 To add a new page of content to the TTSite view hierarchy, just create a
781 new C<.tt2> file in C<root/src>. Only include HTML markup that goes
782 inside the HTML <body> and </body> tags, TTSite will use the contents of
783 C<root/lib/site> to add the top and bottom.
785 First create a directory for book-related TT templates:
787 $ mkdir root/src/books
789 Then open C<root/src/books/list.tt2> in your editor and enter:
791 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
792 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
793 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
794 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
796 [% # Provide a title to root/lib/site/header -%]
797 [% META title = 'Book List' -%]
800 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
801 [% # Display each book in a table row %]
802 [% FOREACH book IN books -%]
804 <td>[% book.title %]</td>
805 <td>[% book.rating %]</td>
807 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
808 [% # loop in 'side effect notation' to load just the last names of the -%]
809 [% # authors into the list. Note that we are making a bogus assignment to -%]
810 [% # the 'xx' vbl to avoid printing the size of the list after each push. -%]
812 xx = tt_authors.push(author.last_name) FOREACH author = book.authors %]
813 [% # Now use a TT 'virtual method' to display the author count in parens -%]
814 ([% tt_authors.size %])
815 [% # Use another vmethod to join & print the names with comma separators -%]
816 [% tt_authors.join(', ') %]
822 As indicated by the inline comments above, the C<META title> line uses
823 TT's META feature to provide a title to C<root/lib/site/header>.
824 Meanwhile, the outer C<FOREACH> loop iterates through each C<book> model
825 object and prints the C<title> and C<rating> fields. An inner
826 C<FOREACH> loop prints the last name of each author in a comma-separated
827 list within a single table cell.
829 If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT
830 code. TT supports a wide variety of directives for "calling" other
831 files, looping, conditional logic, etc. In general, TT simplifies the
832 usual range of Perl operators down to the single dot (C<.>) operator.
833 This applies to operations as diverse as method calls, hash lookups, and
834 list index values (see
835 L<http://www.template-toolkit.org/docs/default/Manual/Variables.html>
836 for details and examples). In addition to the usual C<Template> module
837 Pod documentation, you can access the TT manual at
838 L<http://www.template-toolkit.org/docs/default/>.
840 B<NOTE>: The C<TTSite> helper creates several TT files using an
841 extension of C<.tt2>. Most other Catalyst and TT examples use an
842 extension of C<.tt>. You can use either extension (or no extension at
843 all) with TTSite and TT, just be sure to use the appropriate extension
844 for both the file itself I<and> the C<$c-E<gt>stash-E<gt>{template} =
845 ...> line in your controller. This document will use C<.tt2> for
846 consistency with the files already created by the C<TTSite> helper.
849 =head1 RUN THE APPLICATION
851 First, let's enable an environment variable option that causes
852 DBIx::Class to dump the SQL statements it's using to access the database
853 (this option can provide extremely helpful troubleshooting information):
855 $ export DBIX_CLASS_STORAGE_DBI_DEBUG=1
857 B<NOTE>: You can also set this in your code using
858 C<$class-E<gt>storage-E<gt>debug(1);>. See
859 L<DBIx::Class::Manual::Troubleshooting> for details (including options
860 to log to file instead of displaying to the Catalyst development server
863 Then run the Catalyst "demo server" script:
865 $ script/myapp_server.pl
867 You should get something like this:
869 $ script/myapp_server.pl
870 [Tue May 16 12:51:33 2006] [catalyst] [debug] Debug messages enabled
871 [Tue May 16 12:51:33 2006] [catalyst] [debug] Loaded plugins:
872 .------------------------------------------------------------------------------.
873 | Catalyst::Plugin::ConfigLoader 0.09 |
874 | Catalyst::Plugin::Static::Simple 0.14 |
875 | Catalyst::Plugin::StackTrace 0.04 |
876 | Catalyst::Plugin::DefaultEnd 0.06 |
877 '------------------------------------------------------------------------------'
879 [Tue May 16 12:51:33 2006] [catalyst] [debug] Loaded dispatcher "Catalyst::Dispatcher"
880 [Tue May 16 12:51:33 2006] [catalyst] [debug] Loaded engine "Catalyst::Engine::HTTP"
881 [Tue May 16 12:51:33 2006] [catalyst] [debug] Found home "/home/me/MyApp"
882 [Tue May 16 12:51:37 2006] [catalyst] [debug] Loaded components:
883 .-------------------------------------------------------------------+----------.
885 +-------------------------------------------------------------------+----------+
886 | MyApp::Controller::Books | instance |
887 | MyApp::Controller::Root | instance |
888 | MyApp::Model::MyAppDB | instance |
889 | MyApp::Model::MyAppDB::Author | class |
890 | MyApp::Model::MyAppDB::Book | class |
891 | MyApp::Model::MyAppDB::BookAuthor | class |
892 | MyApp::View::TT | instance |
893 '-------------------------------------------------------------------+----------'
895 [Tue May 16 12:51:37 2006] [catalyst] [debug] Loaded Private actions:
896 .----------------------+----------------------------------------+--------------.
897 | Private | Class | Method |
898 +----------------------+----------------------------------------+--------------+
899 | /default | MyApp::Controller::Root | default |
900 | /end | MyApp | end |
901 | /books/list | MyApp::Controller::Books | list |
902 '----------------------+----------------------------------------+--------------'
904 [Tue May 16 12:51:37 2006] [catalyst] [debug] Loaded Path actions:
905 .--------------------------------------+---------------------------------------.
907 +--------------------------------------+---------------------------------------+
908 | /books/list | /books/list |
909 '--------------------------------------+---------------------------------------'
911 [Tue May 16 12:51:37 2006] [catalyst] [info] MyApp powered by Catalyst 5.6902
912 You can connect to your server at http://localhost:3000
914 Some things you should note in the output above:
920 Catalyst::Model::DBIC::Schema took our C<MyAppDB::Book> and made it
921 C<MyApp::Model::MyAppDB::Book> (and similar actions were performed on
922 C<MyAppDB::Author> and C<MyAppDB::BookAuthor>).
926 The "list" action in our Books controller showed up with a path of
931 Point your browser to L<http://localhost:3000> and you should still get
932 the Catalyst welcome page.
934 Next, to view the book list, change the URL in your browser to
935 L<http://localhost:3000/books/list>. You should get a list of the five
936 books loaded by the C<myapp01.sql> script above, with TTSite providing
937 the formatting for the very simple output we generated in our template.
938 The count and space-separated list of author last names appear on the
941 Also notice in the output of the C<script/myapp_server.pl> that DBIC
942 used the following SQL to retrieve the data:
944 SELECT me.id, me.title, me.rating FROM books me
946 Along with a list of the following commands to retrieve the authors for
947 each book (the lines have been "word wrapped" here to improve
950 SELECT author.id, author.first_name, author.last_name
952 JOIN authors author ON ( author.id = me.author_id )
953 WHERE ( me.book_id = ? ): `1'
955 You should see 10 such lines of debug output, two for each of the five
956 author_id values (it pulls the data once for the count logic and another
957 time to actually display the list).
962 Kennedy Clark, C<hkclark@gmail.com>
964 Please report any errors, issues or suggestions to the author.
966 Copyright 2006, Kennedy Clark, under Creative Commons License
967 (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).