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>
55 In this part of the tutorial, we will create a very basic Catalyst web
56 application. Though simple in many respects, this section will already
57 demonstrate a number of powerful capabilities such as:
61 =item * Helper Scripts
63 Catalyst helper scripts that can be used to rapidly bootstrap the
64 skeletal structure of an application.
68 Model/View/Controller (MVC) provides an architecture that facilitates a
69 clean "separation of control" between the different portions of your
70 application. Given that many other documents cover this subject in
71 detail, MVC will not be discussed in depth here (for an excellent
72 introduction to MVC and general Catalyst concepts, please see
73 L<Catalyst::Manual::About>. In short:
79 The model usually represents a data store. In most applications, the
80 model equates to the objects that are created from and saved to your SQL
85 The view takes model objects and renders them into something for the end
86 user to look at. Normally this involves a template-generation tool that
87 creates HTML for the user's web browser, but it could easily be code
88 that generates other forms such as PDF documents, e-mails, or Excel
93 As suggested by its name, the controller takes user requests and routes
94 them to the necessary model and view.
100 The use of Object-Relational Mapping (ORM) technology for database
101 access. Specifically, ORM provides an automated and standardized means
102 to persist and restore objects to/from a relational database.
106 B<TIP>: Note that all of the code for this part of the tutorial can be
107 pulled from the Catalyst Subversion repository in one step with the
110 svn checkout http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/Tutorial -r 4609 .
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>:
124 created "MyApp/script"
128 created "MyApp/script/myapp_create.pl"
131 The C<catalyst.pl> helper script will display the names of the
132 directories and files it creates.
134 Though it's too early for any significant celebration, we already have a
135 functioning application. Run the following command to run this
136 application with the built-in development web server:
138 $ script/myapp_server.pl
139 [debug] Debug messages enabled
140 [debug] Loaded plugins:
141 .----------------------------------------------------------------------------.
142 | Catalyst::Plugin::ConfigLoader 0.06 |
143 | Catalyst::Plugin::Static::Simple 0.14 |
144 '----------------------------------------------------------------------------'
146 [debug] Loaded dispatcher "Catalyst::Dispatcher"
147 [debug] Loaded engine "Catalyst::Engine::HTTP"
148 [debug] Found home "/root/dev/MyApp"
149 [debug] Loaded components:
150 .-----------------------------------------------------------------+----------.
152 +-----------------------------------------------------------------+----------+
153 | MyApp::Controller::Root | instance |
154 '-----------------------------------------------------------------+----------'
156 [debug] Loaded Private actions:
157 .----------------------+--------------------------------------+--------------.
158 | Private | Class | Method |
159 +----------------------+--------------------------------------+--------------+
160 | /default | MyApp::Controller::Root | default |
161 | /end | MyApp::Controller::Root | end |
162 '----------------------+--------------------------------------+--------------'
164 [info] MyApp powered by Catalyst 5.7000
165 You can connect to your server at http://localhost.localdomain:3000
167 Point your web browser to L<http://localhost:3000> (substituting a
168 different hostname or IP address as appropriate) and you should be
169 greeted by the Catalyst welcome screen. Information similar to the
170 following should be appended to the logging output of the development
173 [info] *** Request 1 (0.008/s) [2822] [Mon Jul 3 12:42:43 2006] ***
174 [debug] "GET" request for "/" from "127.0.0.1"
175 [info] Request took 0.154781s (6.461/s)
176 .----------------------------------------------------------------+-----------.
178 +----------------------------------------------------------------+-----------+
179 | /default | 0.069475s |
181 '----------------------------------------------------------------+-----------'
183 Press Ctrl-C to break out of the development server.
186 =head1 CREATE A SQLITE DATABASE
188 In this step, we make a text file with the required SQL commands to
189 create a database table and load some sample data. Open C<myapp01.sql>
190 in your editor and enter:
193 -- Create a very simple database to hold book and author information
196 id INTEGER PRIMARY KEY,
200 -- 'book_authors' is a many-to-many join table between books & authors
201 CREATE TABLE book_authors (
204 PRIMARY KEY (book_id, author_id)
206 CREATE TABLE authors (
207 id INTEGER PRIMARY KEY,
212 --- Load some sample data
214 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
215 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
216 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
217 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
218 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
219 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
220 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
221 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
222 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
223 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
224 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
225 INSERT INTO authors VALUES (7, ' Nathan', 'Torkington');
226 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
227 INSERT INTO book_authors VALUES (1, 1);
228 INSERT INTO book_authors VALUES (1, 2);
229 INSERT INTO book_authors VALUES (1, 3);
230 INSERT INTO book_authors VALUES (2, 4);
231 INSERT INTO book_authors VALUES (3, 5);
232 INSERT INTO book_authors VALUES (4, 6);
233 INSERT INTO book_authors VALUES (4, 7);
234 INSERT INTO book_authors VALUES (5, 8);
236 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
237 cutting and pasting example code from POD-based documents.
239 Then use the following command to build a C<myapp.db> SQLite database:
241 $ sqlite3 myapp.db < myapp01.sql
243 If you need to create the database more than once, you probably want to
244 issue the C<rm myapp.db> command to delete the database before you use
245 the C<sqlite3 myapp.db < myapp01.sql> command.
247 Once the C<myapp.db> database file has been created and initialized, you
248 can use the SQLite command line environment to do a quick dump of the
253 Enter ".help" for instructions
254 sqlite> select * from books;
255 1|CCSP SNRS Exam Certification Guide|5
256 2|TCP/IP Illustrated, Volume 1|5
257 3|Internetworking with TCP/IP Vol.1|4
259 5|Designing with Web Standards|5
265 $ sqlite3 myapp.db "select * from books"
266 1|CCSP SNRS Exam Certification Guide|5
267 2|TCP/IP Illustrated, Volume 1|5
268 3|Internetworking with TCP/IP Vol.1|4
270 5|Designing with Web Standards|5
272 As with most other SQL tools, if you are using the full "interactive"
273 environment you need to terminate your SQL commands with a ";" (it's not
274 required if you do a single SQL statement on the command line). Use
275 ".q" to exit from SQLite from the SQLite interactive mode and return to
276 your OS command prompt.
279 =head1 EDIT THE LIST OF CATALYST PLUGINS
281 One of the greatest benefits of Catalyst is that it has such a large
282 library of plugins available. Plugins are used to seamlessly integrate
283 existing Perl modules into the overall Catalyst framework. In general,
284 they do this by adding additional methods to the C<context> object
285 (generally written as C<$c>) that Catalyst passes to every component
286 throughout the framework.
288 By default, Catalyst enables three plugins/flags:
296 Enables the Catalyst debug output you saw when we started the
297 C<script/myapp_server.pl> development server earlier. You can remove
298 this plugin when you place your application into production.
300 As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
301 Although most of the items specified on the C<use Catalyst> line of your
302 application class will be plugins, Catalyst supports a limited number of
303 flag options (of these, C<-Debug> is the most common). See the
304 documentation for C<Catalyst.pm> to get details on other flags
305 (currently C<-Engine>, C<-Home>, and C<-Log>).
307 If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
312 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
314 C<ConfigLoader> provides an automatic way to load configurable
315 parameters for your application from a central YAML file (versus having
316 the values hard-coded inside your Perl modules). If you have not been
317 exposed to YAML before, it is a human-readable data serialization format
318 that can be used to read (and write) values to/from text files. We will
319 see how to use this feature of Catalyst during the authentication and
320 authorization sections (Part 4 and Part 5).
324 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
326 C<Static::Simple> provides an easy method of serving static content such
327 as images and CSS files under the development server.
331 To modify the list of plugins, edit C<lib/MyApp.pm> (this file is
332 generally referred to as your I<application class>) and delete the line
335 use Catalyst qw/-Debug ConfigLoader Static::Simple/;
347 This tells Catalyst to start using one new plugin:
353 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>
355 Adds a stack trace to the standard Catalyst "debug screen" (this is the
356 screen Catalyst sends to your browser when an error occurs).
358 Note: L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
359 browser, not in the console window from which you're running your
360 application, which is where logging output usually goes.
364 Note that when specifying plugins on the C<use Catalyst> line, you can
365 omit C<Catalyst::Plugin::> from the name. Additionally, you can spread
366 the plugin names across multiple lines as shown here, or place them all
367 on one (or more) lines as with the default configuration.
369 B<TIP:> You may see examples that include the
370 L<Catalyst::Plugin::DefaultEnd|Catalyst::Plugin::DefaultEnd>
371 plugins. As of Catalyst 5.7000, C<DefaultEnd> has been
372 deprecated in favor of
373 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView>
374 (as the name of the package suggests, C<RenderView> is not
375 a plugin, but an action). The purpose of both is essentially the same:
376 forward processing to the view to be rendered. Applications generated
377 under 5.7000 should automatically use C<RenderView> and "just work"
378 for most applications. For more information on C<RenderView> and
379 the various options for forwarding to your view logic, please refer
380 to the "Using RenderView for the Default View" section under
381 "CATALYST VIEWS" below.
384 =head1 DATABASE ACCESS WITH C<DBIx::Class>
386 Catalyst can be used with virtually any form of persistent datastore
387 available via Perl. For example,
388 L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to
389 easily access databases through the traditional Perl C<DBI> interface.
390 However, most Catalyst applications use some form of ORM technology to
391 automatically create and save model objects as they are used. Although
392 Tony Bowden's L<Class::DBI|Class::DBI> has been the traditional
393 Perl ORM engine, Matt Trout's L<DBIx::Class|DBIx::Class> (abbreviated
394 as "DBIC") has rapidly emerged as the Perl-based ORM technology of choice.
395 Most new Catalyst applications rely on DBIC, as will this tutorial.
397 Note: See L<Catalyst:: Model::CDBI> for more information on using
398 Catalyst with L<Class::DBI|Class::DBI>.
400 =head2 Create a DBIC Schema File
402 DBIx::Class uses a schema file to load other classes that represent the
403 tables in your database (DBIC refers to these "table objects" as "result
404 sources"; see L<DBIx::Class::ResultSource>). In this case, we want to
405 load the model object for the C<books>, C<book_authors>, and C<authors>
406 tables created in the previous step.
408 Open C<lib/MyAppDB.pm> in your editor and insert:
414 MyAppDB - DBIC Schema Class
418 # Our schema needs to inherit from 'DBIx::Class::Schema'
419 use base qw/DBIx::Class::Schema/;
421 # Need to load the DB Model classes here.
422 # You can use this syntax if you want:
423 # __PACKAGE__->load_classes(qw/Book BookAuthor Author/);
424 # Also, if you simply want to load all of the classes in a directory
425 # of the same name as your schema class (as we do here) you can use:
426 # __PACKAGE__->load_classes(qw//);
427 # But the variation below is more flexible in that it can be used to
428 # load from multiple namespaces.
429 __PACKAGE__->load_classes({
430 MyAppDB => [qw/Book BookAuthor Author/]
435 B<Note:> C<__PACKAGE__> is just a shorthand way of referencing the name
436 of the package where it is used. Therefore, in C<MyAppDB.pm>,
437 C<__PACKAGE__> is equivalent to C<MyAppDB>.
440 =head2 Create the DBIC "Result Source" Files
442 In this step, we create "table classes" (again, these are called a
443 "result source" classes in DBIC) that act as model objects for the
444 C<books>, C<book_authors>, and C<authors> tables in our database.
446 First, create a directory to hold the class:
450 Then open C<lib/MyAppDB/Book.pm> in your editor and enter:
452 package MyAppDB::Book;
454 use base qw/DBIx::Class/;
456 # Load required DBIC stuff
457 __PACKAGE__->load_components(qw/PK::Auto Core/);
459 __PACKAGE__->table('books');
460 # Set columns in table
461 __PACKAGE__->add_columns(qw/id title rating/);
462 # Set the primary key for the table
463 __PACKAGE__->set_primary_key(qw/id/);
471 # 1) Name of relationship, DBIC will create accessor with this name
472 # 2) Name of the model class referenced by this relationship
473 # 3) Column name in *foreign* table
474 __PACKAGE__->has_many(book_authors => 'MyAppDB::BookAuthor', 'book_id');
478 # 1) Name of relationship, DBIC will create accessor with this name
479 # 2) Name of has_many() relationship this many_to_many() is shortcut for
480 # 3) Name of belongs_to() relationship in model class of has_many() above
481 # You must already have the has_many() defined to use a many_to_many().
482 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
487 MyAppDB::Book - A model object representing a book.
491 This is an object that represents a row in the 'books' table of your application
492 database. It uses DBIx::Class (aka, DBIC) to do ORM.
494 For Catalyst, this is designed to be used through MyApp::Model::MyAppDB.
495 Offline utilities may wish to use this class directly.
501 This defines both a C<has_many> and a C<many_to_many> relationship. The
502 C<many_to_many> relationship is optional, but it makes it easier to map
503 a book to its collection of authors. Without it, we would have to
504 "walk" though the C<book_authors> table as in
505 C<$book-E<gt>book_authors-E<gt>first-E<gt>author-E<gt>last_name> (we
506 will see examples on how to use DBIC objects in your code soon, but note
507 that because C<$book-E<gt>book_authors> can return multiple authors, we
508 have to use C<first> to display a single author). C<many_to_many> allows
509 us to use the shorter C<$book-E<gt>authors-E<gt>first-E<gt>last_name>.
510 Note that you cannot define a C<many_to_many> relationship without also
511 having the C<has_many> relationship in place.
513 Next, open C<lib/MyAppDB/Author.pm> in your editor and enter:
515 package MyAppDB::Author;
517 use base qw/DBIx::Class/;
519 # Load required DBIC stuff
520 __PACKAGE__->load_components(qw/PK::Auto Core/);
522 __PACKAGE__->table('authors');
523 # Set columns in table
524 __PACKAGE__->add_columns(qw/id first_name last_name/);
525 # Set the primary key for the table
526 __PACKAGE__->set_primary_key(qw/id/);
534 # 1) Name of relationship, DBIC will create accessor with this name
535 # 2) Name of the model class referenced by this relationship
536 # 3) Column name in *foreign* table
537 __PACKAGE__->has_many(book_author => 'MyAppDB::BookAuthor', 'author_id');
541 # 1) Name of relationship, DBIC will create accessor with this name
542 # 2) Name of has_many() relationship this many_to_many() is shortcut for
543 # 3) Name of belongs_to() relationship in model class of has_many() above
544 # You must already have the has_many() defined to use a many_to_many().
545 __PACKAGE__->many_to_many(books => 'book_author', 'book');
550 MyAppDB::Author - A model object representing an author of a book (if a book has
551 multiple authors, each will be represented be separate Author object).
555 This is an object that represents a row in the 'authors' table of your application
556 database. It uses DBIx::Class (aka, DBIC) to do ORM.
558 For Catalyst, this is designed to be used through MyApp::Model::MyAppDB.
559 Offline utilities may wish to use this class directly.
565 Finally, open C<lib/MyAppDB/BookAuthor.pm> in your editor and enter:
567 package MyAppDB::BookAuthor;
569 use base qw/DBIx::Class/;
571 # Load required DBIC stuff
572 __PACKAGE__->load_components(qw/PK::Auto Core/);
574 __PACKAGE__->table('book_authors');
575 # Set columns in table
576 __PACKAGE__->add_columns(qw/book_id author_id/);
577 # Set the primary key for the table
578 __PACKAGE__->set_primary_key(qw/book_id author_id/);
586 # 1) Name of relationship, DBIC will create accessor with this name
587 # 2) Name of the model class referenced by this relationship
588 # 3) Column name in *this* table
589 __PACKAGE__->belongs_to(book => 'MyAppDB::Book', 'book_id');
593 # 1) Name of relationship, DBIC will create accessor with this name
594 # 2) Name of the model class referenced by this relationship
595 # 3) Column name in *this* table
596 __PACKAGE__->belongs_to(author => 'MyAppDB::Author', 'author_id');
601 MyAppDB::BookAuthor - A model object representing the JOIN between an author and
606 This is an object that represents a row in the 'book_authors' table of your
607 application database. It uses DBIx::Class (aka, DBIC) to do ORM.
609 You probably won't need to use this class directly -- it will be automatically
610 used by DBIC where joins are needed.
612 For Catalyst, this is designed to be used through MyApp::Model::MyAppDB.
613 Offline utilities may wish to use this class directly.
619 B<Note:> This sample application uses a plural form for the database
620 tables (e.g., C<books> and C<authors>) and a singular form for the model
621 objects (e.g., C<Book> and C<Author>); however, Catalyst places no
622 restrictions on the naming conventions you wish to use.
624 =head2 Use C<Catalyst::Model::DBIC::Schema> To Load The Model Class
626 When L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> is
627 in use, Catalyst essentially reads an existing copy of your database
628 model and creates a new set of objects under C<MyApp::Model> for use
632 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> you
633 essentially end up with two sets of model classes (only one of which
634 you write... the other set is created automatically in memory when
635 your Catalyst application initializes). For this tutorial application,
636 the important points to remember are: you write the I<result source>
637 files in C<MyAppDB>, but I<within Catalyst> you use the I<automatically
638 created model classes> in C<MyApp::Model>.
641 L<Catalyst::Helper::Model::DBIC::Schema|Catalyst::Helper::Model::DBIC::Schema>
642 helper script to create the model class that loads up the model we
643 created in the previous step:
645 $ script/myapp_create.pl model MyAppDB DBIC::Schema MyAppDB dbi:SQLite:myapp.db '' '' '{ AutoCommit => 1 }'
646 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
647 exists "/root/dev/MyApp/script/../t"
648 created "/root/dev/MyApp/script/../lib/MyApp/Model/MyAppDB.pm"
649 created "/root/dev/MyApp/script/../t/model_MyAppDB.t"
652 Where the first C<MyAppDB> is the name of the class to be created by the
653 helper in C<lib/MyApp/Model> and the second C<MyAppDB> is the name of
654 existing schema file we created (in C<lib/MyAppDB.pm>). You can see
655 that the helper creates a model file under C<lib/MyApp/Model> (Catalyst
656 has a separate directory under C<lib/MyApp> for each of the three parts
657 of MVC: C<Model>, C<View>, and C<Controller> [although older Catalyst
658 applications often use the directories C<M>, C<V>, and C<C>]).
661 =head1 CREATE A CATALYST CONTROLLER
663 Controllers are where you write methods that interact with user
664 input--typically, controller methods respond to C<GET> and C<POST>
665 messages from the user's web browser.
667 Use the Catalyst C<create> script to add a controller for book-related
670 $ script/myapp_create.pl controller Books
671 exists "/root/dev/MyApp/script/../lib/MyApp/Controller"
672 exists "/root/dev/MyApp/script/../t"
673 created "/root/dev/MyApp/script/../lib/MyApp/Controller/Books.pm"
674 created "/root/dev/MyApp/script/../t/controller_Books.t"
676 Then edit C<lib/MyApp/Controller/Books.pm> and add the following method
681 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
686 # Retrieve the usual perl OO '$self' for this object. $c is the Catalyst
687 # 'Context' that's used to 'glue together' the various components
688 # that make up the application
691 # Retrieve all of the book records as book model objects and store in the
692 # stash where they can be accessed by the TT template
693 $c->stash->{books} = [$c->model('MyAppDB::Book')->all];
695 # Set the TT template to use. You will almost always want to do this
696 # in your action methods.
697 $c->stash->{template} = 'books/list.tt2';
700 B<Note:> Programmers experienced with object-oriented Perl should
701 recognize C<$self> as a reference to the object where this method was
702 called. On the other hand, C<$c> will be new to many Perl programmers
703 who have not used Catalyst before (it's sometimes written as
704 C<$context>). The Context object is automatically passed to all
705 Catalyst components. It is used to pass information between components
706 and provide access to Catalyst and plugin functionality.
708 B<TIP>: You may see the C<$c-E<gt>model('MyAppDB::Book')> used above
709 written as C<$c-E<gt>model('MyAppDB')-E<gt>resultset('Book)>. The two
712 B<Note:> Catalyst actions are regular Perl methods, but they make use of
713 Nicholas Clark's C<attributes> module (that's the C<: Local> next to the
714 C<sub list> in the code above) to provide additional information to the
715 Catalyst dispatcher logic.
718 =head1 CATALYST VIEWS
720 Views are where you render output, typically for display in the user's
721 web browser, but also possibly using other display output-generation
722 systems. As with virtually every aspect of Catalyst, options abound
723 when it comes to the specific view technology you adopt inside your
724 application. However, most Catalyst applications use the Template
725 Toolkit, known as TT (for more information on TT, see
726 L<http://www.template-toolkit.org>). Other popular view technologies
727 include Mason (L<http://www.masonhq.com> and
728 L<http://www.masonbook.com>) and L<HTML::Template|HTML::Template>
729 (L<http://html-template.sourceforge.net>).
731 =head2 Create a Catalyst View Using C<TTSITE>
733 When using TT for the Catalyst view, there are two main helper scripts:
739 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
743 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
747 Both are similar, but C<TT> merely creates the C<lib/MyApp/View/TT.pm>
748 file and leaves the creation of any hierarchical template organization
749 entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
750 test cases will be discussed in Part 7). The C<TTSite> helper creates a
751 modular and hierarchical view layout with separate Template Toolkit (TT)
752 files for common header and footer information, configuration values, a
753 CSS stylesheet, and more.
755 Enter the following command to enable the C<TTSite> style of view
756 rendering for this tutorial:
758 $ script/myapp_create.pl view TT TTSite
759 exists "/root/dev/MyApp/script/../lib/MyApp/View"
760 exists "/root/dev/MyApp/script/../t"
761 created "/root/dev/MyApp/script/../lib/MyApp/View/TT.pm"
762 created "/root/dev/MyApp/script/../root/lib"
764 created "/root/dev/MyApp/script/../root/src/ttsite.css"
766 This puts a number of files in the C<root/lib> and C<root/src>
767 directories that can be used to customize the look and feel of your
768 application. Also take a look at C<lib/MyApp/View/TT.pm> for config
769 values set by the C<TTSite> helper.
771 B<TIP>: Note that TTSite does one thing that could confuse people who
772 are used to the normal C<TT> Catalyst view: it redefines the Catalyst
773 context object in templates from its usual C<c> to C<Catalyst>. When
774 looking at other Catalyst examples, remember that they almost always use
775 C<c>. Note that Catalyst and TT I<do not complain> when you use the
776 wrong name to access the context object...TT simply outputs blanks for
777 that bogus logic (see next tip to change this behavior with TT C<DEBUG>
778 options). Finally, be aware that this change in name I<only>
779 applies to how the context object is accessed inside your TT templates;
780 your controllers will continue to use C<$c> (or whatever name you use
781 when fetching the reference from C<@_> inside your methods). (You can
782 change back to the "default" behavior be removing the C<CATALYST_VAR>
783 line from C<lib/MyApp/View/TT.pm>, but you will also have to edit
784 C<root/lib/config/main> and C<root/lib/config/url>. If you do this, be
785 careful not to have a collision between your own C<c> variable and the
786 Catalyst C<c> variable.)
788 B<TIP>: When troubleshooting TT it can be helpful to enable variable
789 C<DEBUG> options. You can do this in a Catalyst environment by adding
790 a C<DEBUG> line to the C<__PACKAGE__->config> declaration in
793 __PACKAGE__->config({
794 CATALYST_VAR => 'Catalyst',
800 There are a variety of options you can use, such as 'undef', 'all',
801 'service', 'context', 'parser', 'provider', and 'service'. See
802 L<Template::Constants> for more information (remove the C<DEBUG_>
803 portion of the name shown in the TT docs and convert to lower case
804 for use inside Catalyst).
807 =head2 Using C<RenderView> for the Default View
809 Once your controller logic has processed the request from a user, it
810 forwards processing to your view in order to generate the appropriate
811 response output. Catalyst v5.7000 ships with a new mechanism,
812 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView>, that
813 automatically performs this operation. If you look in
814 C<lib/MyApp/Controller/Root.pm>, you should see the this empty
815 definition for the C<sub end> method:
817 sub end : ActionClass('RenderView') {}
819 The following bullet points provide a quick overview of the
820 C<RenderView> process:
826 C<Root.pm> is designed to hold application-wide logic.
830 At the end of a given user request, Catalyst will call the most specific
831 C<end> method that's appropriate. For example, if the controller for a
832 request has an C<end> method defined, it will be called. However, if
833 the controller does not define a controller-specific C<end> method, the
834 "global" C<end> method in C<Root.pm> will be called.
838 Because the definition includes an C<ActionClass> attribute, the
839 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
840 will be executed B<after> any code inside the definition of C<sub end>
841 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
842 for more information on C<ActionClass>.
846 Because C<sub end> is empty, this effectively just runs the default
847 logic in C<RenderView>. However, you can easily extend the
848 C<RenderView> logic by adding your own code inside the empty method body
849 (C<{}>) created by the Catalyst Helpers when we first ran the
850 C<catalyst.pl> to initialize our application. See
851 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
852 detailed information on how to extended C<RenderView> in C<sub end>.
857 =head3 The History Leading Up To C<RenderView>
859 Although C<RenderView> strikes a nice balance between default
860 behavior and easy extensibility, it is a new feature that won't
861 appear in most existing Catalyst examples. This section provides
862 some brief background on the evolution of default view rendering
863 logic with an eye to how they can be migrated to C<RenderView>:
869 Private C<end> Action in Application Class
871 Older Catalyst-related documents often suggest that you add a "private
872 end action" to your application class (C<MyApp.pm>) or Root.pm
873 (C<MyApp/Controller/Root.pm>). These examples should be easily
874 converted to L<RenderView|Catalyst::Action::RenderView> by simply adding
875 C<ActionClass('RenderView')> to the C<sub end> definition. If end sub is
876 defined in your application class (C<MyApp.pm>), you should also migrate
877 it to C<MyApp/Controller/Root.pm>.
881 L<Catalyst::Plugin::DefaultEnd|Catalyst::Plugin::DefaultEnd>
883 C<DefaultEnd> represented the "next step" in passing processing from
884 your controller to your view. It has the advantage of only requiring
885 that C<DefaultEnd> be added to the list of plugins in C<lib/MyApp.pm>.
886 It also allowed you to add "dump_info=1" (precede with "?" or "&"
887 depending on where it is in the URL) to I<force> the debug screen at the
888 end of the Catalyst request processing cycle. However, it was more
889 difficult to extend the C<RenderView> mechanism, and is now deprecated.
893 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView>
895 As discussed above, the current recommended approach to handling your
897 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView>. Although
898 similar in first appearance to the "private end action" approach, it
899 utilizes Catalyst's "ActionClass" mechanism to provide both automatic
900 default behavior (you don't have to include a plugin as with
901 C<DefaultEnd>) and easy extensibility. As with C<DefaultEnd>, it allows
902 you to add "dump_info=1" (precede with "?" or "&" depending on where it
903 is in the URL) to I<force> the debug screen at the end of the Catalyst
904 request processing cycle.
908 It is recommended that all Catalyst applications use or migrate to
909 the C<RenderView> approach.
912 =head2 Globally Customize Every View
914 When using TTSite, files in the subdirectories of C<root/lib> can be
915 used to make changes that will appear in every view. For example, to
916 display optional status and error messages in every view, edit
917 C<root/lib/site/layout>, updating it to match the following (the two HTML
918 C<span> elements are new):
920 <div id="header">[% PROCESS site/header %]</div>
923 <span class="message">[% status_msg %]</span>
924 <span class="error">[% error_msg %]</span>
928 <div id="footer">[% PROCESS site/footer %]</div>
930 If we set either message in the Catalyst stash (e.g.,
931 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it will
932 be displayed whenever any view used by that request is rendered. The
933 C<message> and C<error> CSS styles are automatically defined in
934 C<root/src/ttsite.css> and can be customized to suit your needs.
936 B<Note:> The Catalyst stash only lasts for a single HTTP request. If
937 you need to retain information across requests you can use
938 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
939 Catalyst sessions in the Authentication part of the tutorial).
942 =head2 Create a TT Template Page
944 To add a new page of content to the TTSite view hierarchy, just create a
945 new C<.tt2> file in C<root/src>. Only include HTML markup that goes
946 inside the HTML <body> and </body> tags, TTSite will use the contents of
947 C<root/lib/site> to add the top and bottom.
949 First create a directory for book-related TT templates:
951 $ mkdir root/src/books
953 Then open C<root/src/books/list.tt2> in your editor and enter:
955 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
956 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
957 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
958 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
960 [% # Provide a title to root/lib/site/header -%]
961 [% META title = 'Book List' -%]
964 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
965 [% # Display each book in a table row %]
966 [% FOREACH book IN books -%]
968 <td>[% book.title %]</td>
969 <td>[% book.rating %]</td>
971 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
972 [% # loop in 'side effect notation' to load just the last names of the -%]
973 [% # authors into the list. Note that we make a bogus assignment to the -%]
974 [% # 'unused' vbl to avoid printing the size of the list after each push. -%]
976 unused = tt_authors.push(author.last_name) FOREACH author = book.authors %]
977 [% # Now use a TT 'virtual method' to display the author count in parens -%]
978 ([% tt_authors.size %])
979 [% # Use another vmethod to join & print the names with comma separators -%]
980 [% tt_authors.join(', ') %]
986 As indicated by the inline comments above, the C<META title> line uses
987 TT's META feature to provide a title to C<root/lib/site/header>.
988 Meanwhile, the outer C<FOREACH> loop iterates through each C<book> model
989 object and prints the C<title> and C<rating> fields. An inner
990 C<FOREACH> loop prints the last name of each author in a comma-separated
991 list within a single table cell.
993 If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT
994 code. TT supports a wide variety of directives for "calling" other
995 files, looping, conditional logic, etc. In general, TT simplifies the
996 usual range of Perl operators down to the single dot (C<.>) operator.
997 This applies to operations as diverse as method calls, hash lookups, and
998 list index values (see
999 L<http://www.template-toolkit.org/docs/default/Manual/Variables.html>
1000 for details and examples). In addition to the usual C<Template> module
1001 Pod documentation, you can access the TT manual at
1002 L<http://www.template-toolkit.org/docs/default/>.
1004 B<NOTE>: The C<TTSite> helper creates several TT files using an
1005 extension of C<.tt2>. Most other Catalyst and TT examples use an
1006 extension of C<.tt>. You can use either extension (or no extension at
1007 all) with TTSite and TT, just be sure to use the appropriate extension
1008 for both the file itself I<and> the C<$c-E<gt>stash-E<gt>{template} =
1009 ...> line in your controller. This document will use C<.tt2> for
1010 consistency with the files already created by the C<TTSite> helper.
1013 =head1 RUN THE APPLICATION
1015 First, let's enable an environment variable option that causes
1016 DBIx::Class to dump the SQL statements it's using to access the database
1017 (this option can provide extremely helpful troubleshooting information):
1019 $ export DBIX_CLASS_STORAGE_DBI_DEBUG=1
1021 This assumes you are using BASH as your shell -- adjust accordingly if
1022 you are using a different shell (for example, under tcsh, use
1023 C<setenv DBIX_CLASS_STORAGE_DBI_DEBUG 1>).
1025 B<NOTE>: You can also set this in your code using
1026 C<$class-E<gt>storage-E<gt>debug(1);>. See
1027 L<DBIx::Class::Manual::Troubleshooting> for details (including options
1028 to log to file instead of displaying to the Catalyst development server
1031 Then run the Catalyst "demo server" script:
1033 $ script/myapp_server.pl
1035 Your development server log output should display something like:
1037 $ script/myapp_server.pl
1038 [debug] Debug messages enabled
1039 [debug] Loaded plugins:
1040 .----------------------------------------------------------------------------.
1041 | Catalyst::Plugin::ConfigLoader 0.06 |
1042 | Catalyst::Plugin::StackTrace 0.04 |
1043 | Catalyst::Plugin::Static::Simple 0.14 |
1044 '----------------------------------------------------------------------------'
1046 [debug] Loaded dispatcher "Catalyst::Dispatcher"
1047 [debug] Loaded engine "Catalyst::Engine::HTTP"
1048 [debug] Found home "/home/me/MyApp"
1049 [debug] Loaded components:
1050 .-----------------------------------------------------------------+----------.
1052 +-----------------------------------------------------------------+----------+
1053 | MyApp::Controller::Books | instance |
1054 | MyApp::Controller::Root | instance |
1055 | MyApp::Model::MyAppDB | instance |
1056 | MyApp::Model::MyAppDB::Author | class |
1057 | MyApp::Model::MyAppDB::Book | class |
1058 | MyApp::Model::MyAppDB::BookAuthor | class |
1059 | MyApp::View::TT | instance |
1060 '-----------------------------------------------------------------+----------'
1062 [debug] Loaded Private actions:
1063 .----------------------+--------------------------------------+--------------.
1064 | Private | Class | Method |
1065 +----------------------+--------------------------------------+--------------+
1066 | /default | MyApp::Controller::Root | default |
1067 | /end | MyApp::Controller::Root | end |
1068 | /books/index | MyApp::Controller::Books | index |
1069 | /books/list | MyApp::Controller::Books | list |
1070 '----------------------+--------------------------------------+--------------'
1072 [debug] Loaded Path actions:
1073 .-------------------------------------+--------------------------------------.
1075 +-------------------------------------+--------------------------------------+
1076 | /books/list | /books/list |
1077 '-------------------------------------+--------------------------------------'
1079 [info] MyApp powered by Catalyst 5.7000
1080 You can connect to your server at http://localhost.localdomain:3000
1082 Some things you should note in the output above:
1088 Catalyst::Model::DBIC::Schema took our C<MyAppDB::Book> and made it
1089 C<MyApp::Model::MyAppDB::Book> (and similar actions were performed on
1090 C<MyAppDB::Author> and C<MyAppDB::BookAuthor>).
1094 The "list" action in our Books controller showed up with a path of
1099 Point your browser to L<http://localhost:3000> and you should still get
1100 the Catalyst welcome page.
1102 Next, to view the book list, change the URL in your browser to
1103 L<http://localhost:3000/books/list>. You should get a list of the five
1104 books loaded by the C<myapp01.sql> script above, with TTSite providing
1105 the formatting for the very simple output we generated in our template.
1106 The count and space-separated list of author last names appear on the
1109 Also notice in the output of the C<script/myapp_server.pl> that DBIC
1110 used the following SQL to retrieve the data:
1112 SELECT me.id, me.title, me.rating FROM books me
1114 Along with a list of the following commands to retrieve the authors for
1115 each book (the lines have been "word wrapped" here to improve
1118 SELECT author.id, author.first_name, author.last_name
1119 FROM book_authors me
1120 JOIN authors author ON ( author.id = me.author_id )
1121 WHERE ( me.book_id = ? ): `1'
1123 You should see 5 such lines of debug output as DBIC fetches the author
1124 information for each book.
1129 Kennedy Clark, C<hkclark@gmail.com>
1131 Please report any errors, issues or suggestions to the author. The
1132 most recent version of the Catlayst Tutorial can be found at
1133 L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/Catalyst-Runtime/lib/Catalyst/Manual/Tutorial/>.
1135 Copyright 2006, Kennedy Clark, under Creative Commons License
1136 (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).