3 Catalyst::Manual::Tutorial::MoreCatalystBasics - Catalyst Tutorial - Part 3: More Catalyst Application Development Basics
8 This is B<Part 3 of 10> for the Catalyst tutorial.
10 L<Tutorial Overview|Catalyst::Manual::Tutorial>
16 L<Introduction|Catalyst::Manual::Tutorial::Intro>
20 L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics>
24 B<More Catalyst Basics>
28 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>
32 L<Authentication|Catalyst::Manual::Tutorial::Authentication>
36 L<Authorization|Catalyst::Manual::Tutorial::Authorization>
40 L<Debugging|Catalyst::Manual::Tutorial::Debugging>
44 L<Testing|Catalyst::Manual::Tutorial::Testing>
48 L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
52 L<Appendices|Catalyst::Manual::Tutorial::Appendices>
59 This part of the tutorial builds on the work done in Part 2 to explore
60 some features that are more typical of "real world" web applications.
61 From this part of the tutorial onward, we will be building a simple
62 book database application. Although the application will be too
63 limited to be of use to anyone, it should provide a basic environment
64 where we can explore a variety of features used in virtually all web
67 You can checkout the source code for this example from the catalyst
68 subversion repository as per the instructions in
69 L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>.
72 =head1 CREATE A NEW APPLICATION
74 The remainder of the tutorial will build an application called C<MyApp>.
75 First use the Catalyst C<catalyst.pl> script to initialize the framework
76 for the C<MyApp> application (make sure you aren't still inside the
77 directory of the C<Hello> application from the previous part of the
78 tutorial or in a directory that already has a "MyApp" subdirectory):
82 created "MyApp/script"
86 created "MyApp/script/myapp_create.pl"
89 This creates a similar skeletal structure to what we saw in Part 2 of
90 the tutorial, except with C<MyApp> and C<myapp> substituted for
91 C<Hello> and C<hello>.
94 =head1 EDIT THE LIST OF CATALYST PLUGINS
96 One of the greatest benefits of Catalyst is that it has such a large
97 library of plugins and base classes available. Plugins are used to
98 seamlessly integrate existing Perl modules into the overall Catalyst
99 framework. In general, they do this by adding additional methods to the
100 C<context> object (generally written as C<$c>) that Catalyst passes to
101 every component throughout the framework.
103 By default, Catalyst enables three plugins/flags:
111 Enables the Catalyst debug output you saw when we started the
112 C<script/myapp_server.pl> development server earlier. You can remove
113 this item when you place your application into production.
115 As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
116 Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
117 line of your application class will be plugins, Catalyst supports a
118 limited number of flag options (of these, C<-Debug> is the most
119 common). See the documentation for C<Catalyst.pm> to get details on
120 other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
122 If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
125 B<TIP>: Depending on your needs, it can be helpful to permanently
126 remove C<-Debug> from C<lib/MyApp.pm> and then use the C<-d> option
127 to C<script/myapp_server.pl> to re-enable it just for the development
128 server. We will not be using that approach in the tutorial, but feel
129 free to make use of it in your own projects.
133 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
135 C<ConfigLoader> provides an automatic way to load configurable
136 parameters for your application from a central
137 L<Config::General|Config::General> file (versus having the values
138 hard-coded inside your Perl modules). Config::General uses syntax
139 very similar to Apache configuration files. We will see how to use
140 this feature of Catalyst during the authentication and authorization
141 sections (Part 5 and Part 6).
143 B<IMPORTANT NOTE:> If you are using a version of
144 L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, be aware
145 that Catalyst changed the default format from YAML to the more
146 straightforward C<Config::General> style. This tutorial uses the
147 newer C<myapp.conf> file for C<Config::General>. However, Catalyst
148 supports both formats and will automatically use either C<myapp.conf>
149 or C<myapp.yml> (or any other format supported by
150 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
151 L<Config::Any|Config::Any>). If you are using a version of
152 Catalyst::Devel prior to 1.06, you can convert to the newer format by
153 simply creating the C<myapp.conf> file manually and deleting
154 C<myapp.yml>. The default contents of the C<myapp.conf> you create
155 should only consist of one line:
159 B<TIP>: This script can be useful for converting between configuration
162 perl -Ilib -e 'use MyApp; use Config::General;
163 Config::General->new->save_file("myapp.conf", MyApp->config);'
167 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
169 C<Static::Simple> provides an easy method of serving static content such
170 as images and CSS files under the development server.
174 For our application, we want to add one new plugin into the mix. To
175 do this, edit C<lib/MyApp.pm> (this file is generally referred to as
176 your I<application class>) and delete the lines with:
178 use Catalyst qw/-Debug
182 Then replace it with:
185 use Catalyst qw/-Debug
192 B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
193 techniques to load these plugins/flags. For example, you might see
196 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
198 Don't let these variations confuse you -- they all accomplish the same
201 This tells Catalyst to start using one new plugin,
202 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
203 stack trace to the standard Catalyst "debug screen" (the screen
204 Catalyst sends to your browser when an error occurs). Be aware that
205 L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
206 browser, not in the console window from which you're running your
207 application, which is where logging output usually goes.
215 C<__PACKAGE__> is just a shorthand way of referencing the name of the
216 package where it is used. Therefore, in C<MyApp.pm>, C<__PACKAGE__>
217 is equivalent to C<MyApp>.
221 You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
222 before you put your application into production, but it can be helpful
227 When specifying plugins on the C<__PACKAGE__-E<gt>setup> line, you can
228 omit C<Catalyst::Plugin::> from the name. Additionally, you can
229 spread the plugin names across multiple lines as shown here, or place
230 them all on one (or more) lines as with the default configuration.
235 =head1 CREATE A CATALYST CONTROLLER
237 As discussed earlier, controllers are where you write methods that
238 interact with user input. Typically, controller methods respond to
239 C<GET> and C<POST> messages from the user's web browser.
241 Use the Catalyst C<create> script to add a controller for book-related
244 $ script/myapp_create.pl controller Books
245 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
246 exists "/home/me/MyApp/script/../t"
247 created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm"
248 created "/home/me/MyApp/script/../t/controller_Books.t"
250 Then edit C<lib/MyApp/Controller/Books.pm> (as discussed in Part 2 of
251 the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
252 each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
253 and add the following method to the controller:
257 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
262 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
263 # 'Context' that's used to 'glue together' the various components
264 # that make up the application
267 # Retrieve all of the book records as book model objects and store in the
268 # stash where they can be accessed by the TT template
269 # $c->stash->{books} = [$c->model('DB::Books')->all];
270 # But, for now, use this code until we create the model later
271 $c->stash->{books} = '';
273 # Set the TT template to use. You will almost always want to do this
274 # in your action methods (action methods respond to user input in
276 $c->stash->{template} = 'books/list.tt2';
279 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
280 cutting and pasting example code from POD-based documents.
282 Programmers experienced with object-oriented Perl should recognize
283 C<$self> as a reference to the object where this method was called.
284 On the other hand, C<$c> will be new to many Perl programmers who have
285 not used Catalyst before (it's sometimes written as C<$context>). The
286 Context object is automatically passed to all Catalyst components. It
287 is used to pass information between components and provide access to
288 Catalyst and plugin functionality.
290 Catalyst actions are regular Perl methods, but they make use of
291 attributes (the "C<: Local>" next to the "C<sub list>" in the code
292 above) to provide additional information to the Catalyst dispatcher
293 logic (note that the space between the colon and the attribute name is
294 optional... you will see attributes written both ways). Most Catalyst
295 Controllers use one of five action types:
301 B<:Private> -- Use C<:Private> for methods that you want to make into
302 an action, but you do not want Catalyst to directly expose the action
303 to your users. Catalyst will not map C<:Private> methods to a URI.
304 Use them for various sorts of "special" methods (the C<begin>,
305 C<auto>, etc. discussed below) or for methods you want to be able to
306 C<forward> or C<detach> to. (If the method is a plain old "helper
307 method" that you don't want to be an action at all, then just define
308 the method without any attribute -- you can call it in your code, but
309 the Catalyst dispatcher will ignore it.)
311 There are five types of "special" build-in C<:Private> actions:
312 C<begin>, C<end>, C<default>, C<index>, and C<auto>.
318 With C<begin>, C<end>, C<default>, C<index> private actions, only the
319 most specific action of each type will be called. For example, if you
320 define a C<begin> action in your controller it will I<override> a
321 C<begin> action in your application/root controller -- I<only> the
322 action in your controller will be called.
326 Unlike the other actions where only a single method is called for each
327 request, I<every> auto action along the chain of namespaces will be
328 called. Each C<auto> action will be called I<from the application/root
329 controller down through the most specific class>.
335 B<:Path> -- C<:Path> actions let you map a method to an explicit URI
336 path. For example, "C<:Path('list')>" in
337 C<lib/MyApp/Controller/Books.pm> would match on the URL
338 C<http://localhost:3000/books/list> but "C<:Path('/list')>" would match
339 on C<http://localhost:3000/list>. You can use C<:Args()> to specify
340 how many arguments an action should except. See
341 L<Catalyst::Manual::Intro/Action_types> for more information and a few
346 B<:Local> -- C<:Local> is merely a shorthand for
347 "C<:Path('_name_of_method_')>". For example, these are equivalent:
348 "C<sub create_book :Local {...}>" and
349 "C<sub create_book :Path('create_book') {...}>".
353 B<:Global> -- C<:Global> is merely a shorthand for
354 "C<:Path('/_name_of_method_')>". For example, these are equivalent:
355 "C<sub create_book :Global {...}>" and
356 "C<sub create_book :Path('/create_book') {...}>".
360 B<:Chained> -- Newer Catalyst applications tend to use the Chained
361 dispatch form of action types because of its power and flexibility.
362 It allows a series of controller methods to automatically be dispatched
363 to service a single user request. See
364 L<Catalyst::Manual::Tutorial::BasicCRUD|Catalyst::Manual::Tutorial::BasicCRUD>
365 and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
366 for more information on chained actions.
370 You should refer to L<Catalyst::Manual::Intro/Action_types> for
371 additional information and for coverage of some lesser-used action
372 types not discussed here (C<Regex> and C<LocalRegex>).
375 =head1 CATALYST VIEWS
377 As mentioned in Part 2 of the tutorial, views are where you render
378 output, typically for display in the user's web browser (but also
379 possibly using other display output-generation systems). The code in
380 C<lib/MyApp/View> selects the I<type> of view to use, with the actual
381 rendering template found in the C<root> directory. As with virtually
382 every aspect of Catalyst, options abound when it comes to the specific
383 view technology you adopt inside your application. However, most
384 Catalyst applications use the Template Toolkit, known as TT (for more
385 information on TT, see L<http://www.template-toolkit.org>). Other
386 somewhat popular view technologies include Mason
387 (L<http://www.masonhq.com> and L<http://www.masonbook.com>) and
388 L<HTML::Template> (L<http://html-template.sourceforge.net>).
391 =head2 Create a Catalyst View
393 When using TT for the Catalyst view, there are two main helper scripts:
399 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
403 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
407 Both helpers are similar. C<TT> creates the C<lib/MyApp/View/TT.pm>
408 file and leaves the creation of any hierarchical template organization
409 entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
410 test cases will be discussed in Part 8.) C<TTSite>, on the other hand,
411 creates a modular and hierarchical view layout with
412 separate Template Toolkit (TT) files for common header and footer
413 information, configuration values, a CSS stylesheet, and more.
415 While C<TTSite> was useful to bootstrap a project, its use is now
416 deprecated and to be considered historical. For most Catalyst
417 applications it adds redundant functionality and structure; many in the
418 Catalyst community recommend that it's easier to learn both Catalyst and
419 Template Toolkit if you use the more basic C<TT> approach.
420 Consequently, this tutorial will use "plain old TT."
422 Enter the following command to enable the C<TT> style of view
423 rendering for this tutorial:
425 $ script/myapp_create.pl view TT TT
426 exists "/home/me/MyApp/script/../lib/MyApp/View"
427 exists "/home/me/MyApp/script/../t"
428 created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm"
429 created "/home/me/MyApp/script/../t/view_TT.t"
431 This simply creates a view called C<TT> (the second 'TT' argument) in
432 a file called C<TT.pm> (the first 'TT' argument). It is now up to you
433 to decide how you want to structure your view layout. For the
434 tutorial, we will start with a very simple TT template to initially
435 demonstrate the concepts, but quickly migrate to a more typical
436 "wrapper page" type of configuration (where the "wrapper" controls the
437 overall "look and feel" of your site from a single file or set of
440 Edit C<lib/MyApp/View/TT.pm> and you should see that the default
441 contents contains something similar to the following:
443 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
445 And update it to match:
448 # Change default TT extension
449 TEMPLATE_EXTENSION => '.tt2',
450 # Set the location for TT files
452 MyApp->path_to( 'root', 'src' ),
456 B<NOTE:> Make sure to add a comma after '.tt2' outside the single
459 This changes the default extension for Template Toolkit from '.tt' to
460 '.tt2' and changes the base directory for your template files from
461 C<root> to C<root/src>. These changes from the default are done mostly
462 to facilitate the application we're developing in this tutorial; as with
463 most things Perl, there's more than one way to do it...
465 B<Note:> We will use C<root/src> as the base directory for our
466 template files, which a full naming convention of
467 C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
468 use C<root/> as the base (with a full filename pattern of
469 C<root/_controller_name_/_action_name_.tt2>).
472 =head2 Create a TT Template Page
474 First create a directory for book-related TT templates:
476 $ mkdir -p root/src/books
478 Then create C<root/src/books/list.tt2> in your editor and enter:
480 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
481 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
482 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
483 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
485 [% # Provide a title -%]
486 [% META title = 'Book List' -%]
489 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
490 [% # Display each book in a table row %]
491 [% FOREACH book IN books -%]
493 <td>[% book.title %]</td>
494 <td>[% book.rating %]</td>
499 As indicated by the inline comments above, the C<META title> line uses
500 TT's META feature to provide a title to the "wrapper" that we will
501 create later. Meanwhile, the C<FOREACH> loop iterates through each
502 C<book> model object and prints the C<title> and C<rating> fields.
504 If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT
505 code. TT supports a wide variety of directives for "calling" other
506 files, looping, conditional logic, etc. In general, TT simplifies the
507 usual range of Perl operators down to the single dot (C<.>) operator.
508 This applies to operations as diverse as method calls, hash lookups, and
509 list index values (see
510 L<http://search.cpan.org/perldoc?Template::Manual::Variables>
511 for details and examples). In addition to the usual C<Template> module
512 Pod documentation, you can access the TT manual at
513 L<http://search.cpan.org/perldoc?Template::Manual>.
515 B<TIP:> While you can build all sorts of complex logic into your TT
516 templates, you should in general keep the "code" part of your templates
517 as simple as possible. If you need more complex logic, create helper
518 methods in your model that abstract out a set of code into a single call
519 from your TT template. (Note that the same is true of your controller
520 logic as well -- complex sections of code in your controllers should
521 often be pulled out and placed into your model objects.)
524 =head2 Test Run The Application
526 To test your work so far, first start the development server:
528 $ script/myapp_server.pl
530 Then point your browser to L<http://localhost:3000> and you should
531 still get the Catalyst welcome page. Next, change the URL in your
532 browser to L<http://localhost:3000/books/list>. If you have
533 everything working so far, you should see a web page that displays
534 nothing other than our column headers for "Title", "Rating", and
535 "Author(s)" -- we will not see any books until we get the database and
538 If you run into problems getting your application to run correctly, it
539 might be helpful to refer to some of the debugging techniques covered in
540 the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the
544 =head1 CREATE A SQLITE DATABASE
546 In this step, we make a text file with the required SQL commands to
547 create a database table and load some sample data. We will use SQLite,
548 a popular database that is lightweight and easy to use. Open
549 C<myapp01.sql> in your editor and enter:
552 -- Create a very simple database to hold book and author information
555 id INTEGER PRIMARY KEY,
559 -- 'book_authors' is a many-to-many join table between books & authors
560 CREATE TABLE book_authors (
563 PRIMARY KEY (book_id, author_id)
565 CREATE TABLE authors (
566 id INTEGER PRIMARY KEY,
571 --- Load some sample data
573 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
574 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
575 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
576 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
577 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
578 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
579 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
580 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
581 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
582 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
583 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
584 INSERT INTO authors VALUES (7, 'Nathan', 'Torkington');
585 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
586 INSERT INTO book_authors VALUES (1, 1);
587 INSERT INTO book_authors VALUES (1, 2);
588 INSERT INTO book_authors VALUES (1, 3);
589 INSERT INTO book_authors VALUES (2, 4);
590 INSERT INTO book_authors VALUES (3, 5);
591 INSERT INTO book_authors VALUES (4, 6);
592 INSERT INTO book_authors VALUES (4, 7);
593 INSERT INTO book_authors VALUES (5, 8);
595 Then use the following command to build a C<myapp.db> SQLite database:
597 $ sqlite3 myapp.db < myapp01.sql
599 If you need to create the database more than once, you probably want to
600 issue the C<rm myapp.db> command to delete the database before you use
601 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
603 Once the C<myapp.db> database file has been created and initialized, you
604 can use the SQLite command line environment to do a quick dump of the
609 Enter ".help" for instructions
610 sqlite> select * from books;
611 1|CCSP SNRS Exam Certification Guide|5
612 2|TCP/IP Illustrated, Volume 1|5
613 3|Internetworking with TCP/IP Vol.1|4
615 5|Designing with Web Standards|5
621 $ sqlite3 myapp.db "select * from books"
622 1|CCSP SNRS Exam Certification Guide|5
623 2|TCP/IP Illustrated, Volume 1|5
624 3|Internetworking with TCP/IP Vol.1|4
626 5|Designing with Web Standards|5
628 As with most other SQL tools, if you are using the full "interactive"
629 environment you need to terminate your SQL commands with a ";" (it's not
630 required if you do a single SQL statement on the command line). Use
631 ".q" to exit from SQLite from the SQLite interactive mode and return to
632 your OS command prompt.
634 For using other databases, such as PostgreSQL or MySQL, see
635 L<Appendix 2|Catalyst::Manual::Tutorial::Appendices>.
638 =head1 DATABASE ACCESS WITH C<DBIx::Class>
640 Catalyst can be used with virtually any form of persistent datastore
641 available via Perl. For example,
642 L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to easily
643 access databases through the traditional Perl C<DBI> interface. However,
644 most Catalyst applications use some form of ORM technology to
645 automatically create and save model objects as they are used. Although
646 L<Class::DBI|Class::DBI> has been a popular choice in the past, Matt
647 Trout's L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly
648 emerged as the Perl-based ORM technology of choice. Most new Catalyst
649 applications rely on DBIC, as will this tutorial.
652 =head2 Create a Dynamic DBIC Model
654 Use the C<create=dynamic> model helper option to build a model that
655 dynamically reads your database structure every time the application
658 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=dynamic dbi:SQLite:myapp.db
659 exists "/home/me/MyApp/script/../lib/MyApp/Model"
660 exists "/home/me/MyApp/script/../t"
661 exists "/home/me/MyApp/script/../lib/MyApp"
662 created "/home/me/MyApp/script/../lib/MyApp/Schema.pm"
663 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
664 created "/home/me/MyApp/script/../t/model_DB.t"
667 The C<script/myapp_create.pl> command breaks down like this:
673 C<DB> is the name of the model class to be created by the helper in
678 C<DBIC::Schema> is the type of the model to create.
682 C<MyApp::Schema> is the name of the DBIC schema file written to
683 C<lib/MyApp/Schema.pm>.
687 Because we specified C<create=dynamic> to the helper, it use
688 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
689 dynamically load the schema information from the database every time
690 the application starts.
694 And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
699 B<NOTE:> Although the C<create=dynamic> option to the DBIC helper
700 makes for a nifty demonstration, is only really suitable for very
701 small applications. After this demonstration, you should almost always
702 use the C<create=static> option that we switch to below.
705 =head1 ENABLE THE MODEL IN THE CONTROLLER
707 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
708 left disabled earlier so that your version matches the following (un-
709 comment the line containing C<[$c-E<gt>model('DB::Books')-E<gt>all]>
710 and delete the next 2 lines):
714 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
719 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
720 # 'Context' that's used to 'glue together' the various components
721 # that make up the application
724 # Retrieve all of the book records as book model objects and store in the
725 # stash where they can be accessed by the TT template
726 $c->stash->{books} = [$c->model('DB::Books')->all];
728 # Set the TT template to use. You will almost always want to do this
729 # in your action methods (action methods respond to user input in
731 $c->stash->{template} = 'books/list.tt2';
734 B<TIP>: You may see the C<$c-E<gt>model('DB::Books')> un-commented
735 above written as C<$c-E<gt>model('DB')-E<gt>resultset('Books')>. The
736 two are equivalent. Either way, C<$c-E<gt>model> returns a
737 L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
738 against the database and iterating over the set of results that are
741 We are using the C<-E<gt>all> to fetch all of the books. DBIC
742 supports a wide variety of more advanced operations to easily do
743 things like filtering and sorting the results. For example, the
744 following could be used to sort the results by descending title:
746 $c->model('DB::Books')->search({}, {order_by => 'title DESC'});
748 Some other examples are provided in
749 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
750 additional information found at L<DBIx::Class::ResultSet/search>,
751 L<DBIx::Class::Manual::FAQ/Searching>,
752 L<DBIx::Class::Manual::Intro|DBIx::Class::Manual::Intro>
753 and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
756 =head2 Test Run The Application
758 First, let's enable an environment variable that causes DBIx::Class to
759 dump the SQL statements used to access the database. This is a
760 helpful trick when you are trying to debug your database-oriented
763 $ export DBIC_TRACE=1
765 This assumes you are using BASH as your shell -- adjust accordingly if
766 you are using a different shell (for example, under tcsh, use
767 C<setenv DBIC_TRACE 1>).
769 B<NOTE:> You can also set this in your code using
770 C<$class-E<gt>storage-E<gt>debug(1);>. See
771 L<DBIx::Class::Manual::Troubleshooting> for details (including options
772 to log to file instead of displaying to the Catalyst development server
775 Then launch the Catalyst development server. The log output should
776 display something like:
778 $ script/myapp_server.pl
779 [debug] Debug messages enabled
780 [debug] Statistics enabled
781 [debug] Loaded plugins:
782 .----------------------------------------------------------------------------.
783 | Catalyst::Plugin::ConfigLoader 0.20 |
784 | Catalyst::Plugin::StackTrace 0.08 |
785 | Catalyst::Plugin::Static::Simple 0.20 |
786 '----------------------------------------------------------------------------'
788 [debug] Loaded dispatcher "Catalyst::Dispatcher"
789 [debug] Loaded engine "Catalyst::Engine::HTTP"
790 [debug] Found home "/home/me/MyApp"
791 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
792 [debug] Loaded components:
793 .-----------------------------------------------------------------+----------.
795 +-----------------------------------------------------------------+----------+
796 | MyApp::Controller::Books | instance |
797 | MyApp::Controller::Root | instance |
798 | MyApp::Model::DB | instance |
799 | MyApp::Model::DB::Authors | class |
800 | MyApp::Model::DB::BookAuthors | class |
801 | MyApp::Model::DB::Books | class |
802 | MyApp::View::TT | instance |
803 '-----------------------------------------------------------------+----------'
805 [debug] Loaded Private actions:
806 .----------------------+--------------------------------------+--------------.
807 | Private | Class | Method |
808 +----------------------+--------------------------------------+--------------+
809 | /default | MyApp::Controller::Root | default |
810 | /end | MyApp::Controller::Root | end |
811 | /index | MyApp::Controller::Root | index |
812 | /books/index | MyApp::Controller::Books | index |
813 | /books/list | MyApp::Controller::Books | list |
814 '----------------------+--------------------------------------+--------------'
816 [debug] Loaded Path actions:
817 .-------------------------------------+--------------------------------------.
819 +-------------------------------------+--------------------------------------+
822 | /books | /books/index |
823 | /books/list | /books/list |
824 '-------------------------------------+--------------------------------------'
826 [info] MyApp powered by Catalyst 5.71000
827 You can connect to your server at http://debian:3000
829 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
830 the 'base' directory of your application, not inside the C<script>
831 directory itself or it will not be able to locate the C<myapp.db>
832 database file. You can use a fully qualified or a relative path to
833 locate the database file, but we did not specify that when we ran the
834 model helper earlier.
836 Some things you should note in the output above:
842 Catalyst::Model::DBIC::Schema dynamically created three model classes,
843 one to represent each of the three tables in our database
844 (C<MyApp::Model::DB::Authors>, C<MyApp::Model::DB::BookAuthors>,
845 and C<MyApp::Model::DB::Books>).
849 The "list" action in our Books controller showed up with a path of
854 Point your browser to L<http://localhost:3000> and you should still get
855 the Catalyst welcome page.
857 Next, to view the book list, change the URL in your browser to
858 L<http://localhost:3000/books/list>. You should get a list of the five
859 books loaded by the C<myapp01.sql> script above without any formatting.
860 The rating for each book should appear on each row, but the "Author(s)"
861 column will still be blank (we will fill that in later).
863 Also notice in the output of the C<script/myapp_server.pl> that DBIC
864 used the following SQL to retrieve the data:
866 SELECT me.id, me.title, me.rating FROM books me
868 because we enabled DBIC_TRACE.
870 You now have the beginnings of a simple but workable web application.
871 Continue on to future sections and we will develop the application
875 =head1 CREATE A WRAPPER FOR THE VIEW
877 When using TT, you can (and should) create a wrapper that will
878 literally wrap content around each of your templates. This is
879 certainly useful as you have one main source for changing things that
880 will appear across your entire site/application instead of having to
881 edit many individual files.
884 =head2 Configure TT.pm For The Wrapper
886 In order to create a wrapper, you must first edit your TT view and
887 tell it where to find your wrapper file. Your TT view is located in
888 C<lib/MyApp/View/TT.pm>.
890 Edit C<lib/MyApp/View/TT.pm> and change it to match the following:
893 # Change default TT extension
894 TEMPLATE_EXTENSION => '.tt2',
895 # Set the location for TT files
897 MyApp->path_to( 'root', 'src' ),
899 # Set to 1 for detailed timer stats in your HTML as comments
901 # This is your wrapper template located in the 'root/src'
902 WRAPPER => 'wrapper.tt2',
906 =head2 Create the Wrapper Template File and Stylesheet
908 Next you need to set up your wrapper template. Basically, you'll want
909 to take the overall layout of your site and put it into this file.
910 For the tutorial, open C<root/src/wrapper.tt2> and input the following:
912 <?xml version="1.0" encoding="UTF-8"?>
913 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
914 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
916 <title>[% template.title or "My Catalyst App!" %]</title>
917 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
923 [%# Your logo could go here -%]
924 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
925 [%# Insert the page title -%]
926 <h1>[% template.title or site.title %]</h1>
933 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
934 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
936 </div><!-- end menu -->
939 [%# Status and error messages %]
940 <span class="message">[% status_msg %]</span>
941 <span class="error">[% error_msg %]</span>
942 [%# This is where TT will stick all of your template's contents. -%]
944 </div><!-- end content -->
945 </div><!-- end bodyblock -->
947 <div id="footer">Copyright (c) your name goes here</div>
948 </div><!-- end outer -->
953 Notice the status and error message sections in the code above:
955 <span class="status">[% status_msg %]</span>
956 <span class="error">[% error_msg %]</span>
958 If we set either message in the Catalyst stash (e.g.,
959 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
960 will be displayed whenever any view used by that request is rendered.
961 The C<message> and C<error> CSS styles can be customized to suit your
962 needs in the C<root/static/css/main.css> file we create below.
970 The Catalyst stash only lasts for a single HTTP request. If
971 you need to retain information across requests you can use
972 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
973 Catalyst sessions in the Authentication part of the tutorial).
977 Although it is beyond the scope of this tutorial, you may wish to use
978 a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
979 Dojo (L<http://www.dojotoolkit.org>).
984 =head3 Create A Basic Stylesheet
986 First create a central location for stylesheets under the static
989 $ mkdir root/static/css
991 Then open the file C<root/static/css/main.css> (the file referenced in
992 the stylesheet href link of our wrapper above) and add the following
1011 background-color: #ddd;
1017 padding: 0 0 50% 5px;
1018 font-weight: normal;
1019 background-color: #ddd;
1032 You may wish to check out a "CSS Framework" like Emastic
1033 (L<http://code.google.com/p/emastic/>) as a way to quickly
1034 provide lots of high-quality CSS functionality.
1037 =head2 Test Run The Application
1039 Restart the development server and hit "Reload" in your web browser
1040 and you should now see a formatted version of our basic book list.
1041 Although our wrapper and stylesheet are obviously very simple, you
1042 should see how it allows us to control the overall look of an entire
1043 website from two central files. To add new pages to the site, just
1044 provide a template that fills in the C<content> section of our wrapper
1045 template -- the wrapper will provide the overall feel of the page.
1048 =head1 A STATIC DATABASE MODEL WITH C<DBIx::Class>
1050 =head2 Create Static DBIC Schema Files
1052 Unlike the previous DBIC section where we had C<create=dynamic>
1053 automatically discover the structure of the database every time the
1054 application started, here we will use static schema files for more
1055 control. This is typical of most "real world" applications.
1057 One option would be to manually create a separate schema file for each
1058 table in the database, however, lets use the same
1059 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> used
1060 earlier with C<create=dynamic> to build the static files for us.
1061 First, lets remove the schema file created earlier:
1063 $ rm lib/MyApp/Schema.pm
1065 Now regenerate the schema using the C<create=static> option:
1067 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=static dbi:SQLite:myapp.db
1068 exists "/home/me/MyApp/script/../lib/MyApp/Model"
1069 exists "/home/me/MyApp/script/../t"
1070 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
1071 Schema dump completed.
1072 exists "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
1074 We could have also deleted C<lib/MyApp/Model/DB.pm>, but it would
1075 have regenerated the same file (note the C<exists> in the output above).
1076 If you take a look at C<lib/MyApp/Model/DB.pm>, it simply contains
1077 a reference to the actual schema file in C<lib/MyApp/Schema.pm>
1078 along with the database connect string.
1080 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
1082 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> as its base
1083 class (L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> is
1084 only being used by the helper to load the schema once and then create
1085 the static files for us) and C<Schema.pm> only contains a call to the
1086 C<load_classes> method. You will also find that C<lib/MyApp> contains
1087 a C<Schema> subdirectory, with files inside this directory named
1088 according to each of the tables in our simple database (C<Authors.pm>,
1089 C<BookAuthors.pm>, and C<Books.pm>). These three files are called
1090 "Result Classes" in DBIC nomenclature. Although the Result Class files
1091 are named after tables in our database, the classes correspond to the
1092 I<row-level data> that is returned by DBIC (more on this later,
1094 L<Catalyst::Manual::Tutorial::BasicCRUD/EXPLORING THE POWER OF DBIC>.
1096 The idea with the Result Source files created under
1097 C<lib/MyApp/Schema> by the C<create=static> option is to only edit the
1098 files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> warning.
1099 If you place all of your changes below that point in the file, you can
1100 regenerate the automatically created information at the top of each
1101 file should your database structure get updated.
1103 Also note the "flow" of the model information across the various files
1104 and directories. Catalyst will initially load the model from
1105 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
1106 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the
1107 call to C<load_classes> in C<Schema.pm> will load each of the "result
1108 class" files from the C<lib/MyApp/Schema> subdirectory. The end
1109 result is that Catalyst will dynamically create three table-specific
1110 Catalyst models every time the application starts (you can see these
1111 three model files listed in the debug output generated when you launch
1114 B<NOTE:> The version of
1115 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> in
1116 Debian 5 uses the older DBIC C<load_classes> vs. the newer
1117 C<load_namspaces> technique. For new applications, please try to use
1118 C<load_namespaces> since it more easily supports a very useful DBIC
1119 technique called "ResultSet Classes." We will migrate to
1120 C<load_namespaces> in Part 4 (BasicCRUD) of this tutorial.
1123 =head2 Updating the Generated DBIC Schema Files
1125 Let's manually add some relationship information to the auto-generated
1126 Result Class files. (Note: if you are using a database other than
1127 SQLite, such as PostgreSQL, then the relationship could have been
1128 automatically placed in the Result Class files. If so, you can skip
1129 this step.) First edit C<lib/MyApp/Schema/Books.pm> and add the
1130 following text below the C<# You can replace this text...> comment:
1133 # Set relationships:
1138 # 1) Name of relationship, DBIC will create accessor with this name
1139 # 2) Name of the model class referenced by this relationship
1140 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1141 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::BookAuthors', 'book_id');
1145 # 1) Name of relationship, DBIC will create accessor with this name
1146 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1147 # 3) Name of belongs_to() relationship in model class of has_many() above
1148 # You must already have the has_many() defined to use a many_to_many().
1149 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1152 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1153 file. As with any Perl package, we need to end the last line with
1154 a statement that evaluates to C<true>. This is customarily done with
1155 C<1;> on a line by itself.
1157 C<Important Note:> Although this tutorial uses plural names for both
1158 the names of the SQL tables and therefore the Result Classes (after
1159 all, C<Schema::Loader> automatically named the Result Classes from the
1160 names of the SQL tables it found), DBIC users prefer singular names
1161 for these items. B<Please try to use singular table and DBIC
1162 model/Result Class names in your applications.> This tutorial will
1163 migrate to singular names as soon as possible (patches welcomed).
1164 B<Note that while singular is preferred for the DBIC model, plural is
1165 perfectly acceptable for the names of the controller classes.> After
1166 all, the C<Books.pm> controller operates on multiple books.
1168 This code defines both a C<has_many> and a C<many_to_many> relationship.
1169 The C<many_to_many> relationship is optional, but it makes it easier to
1170 map a book to its collection of authors. Without it, we would have to
1171 "walk" though the C<book_authors> table as in
1172 C<$book-E<gt>book_authors-E<gt>first-E<gt>author-E<gt>last_name>
1173 (we will see examples on how to use DBIC objects in your code soon,
1174 but note that because C<$book-E<gt>book_authors> can return multiple
1175 authors, we have to use C<first> to display a single author).
1176 C<many_to_many> allows us to use the shorter
1177 C<$book-E<gt>authors-E<gt>first-E<gt>last_name>.
1178 Note that you cannot define a C<many_to_many> relationship without
1179 also having the C<has_many> relationship in place.
1181 Then edit C<lib/MyApp/Schema/Authors.pm> and add relationship
1182 information as follows (again, be careful to put in above the C<1;> but
1183 below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1186 # Set relationships:
1191 # 1) Name of relationship, DBIC will create accessor with this name
1192 # 2) Name of the model class referenced by this relationship
1193 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1194 __PACKAGE__->has_many(book_author => 'MyApp::Schema::BookAuthors', 'author_id');
1198 # 1) Name of relationship, DBIC will create accessor with this name
1199 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1200 # 3) Name of belongs_to() relationship in model class of has_many() above
1201 # You must already have the has_many() defined to use a many_to_many().
1202 __PACKAGE__->many_to_many(books => 'book_author', 'book');
1204 Finally, do the same for the "join table,"
1205 C<lib/MyApp/Schema/BookAuthors.pm>:
1208 # Set relationships:
1213 # 1) Name of relationship, DBIC will create accessor with this name
1214 # 2) Name of the model class referenced by this relationship
1215 # 3) Column name in *this* table
1216 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Books', 'book_id');
1220 # 1) Name of relationship, DBIC will create accessor with this name
1221 # 2) Name of the model class referenced by this relationship
1222 # 3) Column name in *this* table
1223 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Authors', 'author_id');
1226 =head2 Run The Application
1228 Run the Catalyst "demo server" script with the C<DBIC_TRACE> option
1229 (it might still be enabled from earlier in the tutorial, but here
1230 is an alternate way to specify the option just in case):
1232 $ DBIC_TRACE=1 script/myapp_server.pl
1234 Make sure that the application loads correctly and that you see the
1235 three dynamically created model class (one for each of the
1236 table-specific schema classes we created).
1238 Then hit the URL L<http://localhost:3000/books/list> with your browser
1239 and be sure that the book list is displayed via the relationships
1240 established above. You can leave the development server running for
1241 the next step if you wish.
1243 B<Note:> You will not see the authors yet because the view does not yet
1244 use the new relations. Read on to the next section where we update the
1245 template to do that.
1248 =head1 UPDATING THE VIEW
1250 Let's add a new column to our book list page that takes advantage of
1251 the relationship information we manually added to our schema files in
1252 the previous section. Edit C<root/src/books/list.tt2> add add the
1253 following code below the existing table cell that contains
1254 C<book.rating> (IOW, add a new table cell below the existing two
1255 C<E<lt>tdE<gt>> tags but above the closing C<E<lt>/trE<gt>> and
1256 C<E<lt>/tableE<gt>> tags):
1260 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1261 [% # loop in 'side effect notation' to load just the last names of the -%]
1262 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1263 [% # a value, so nothing will be printed here. But, if you have something -%]
1264 [% # in TT that does return a method and you don't want it printed, you -%]
1265 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1266 [% # call it and discard the return value. -%]
1267 [% tt_authors = [ ];
1268 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1269 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1270 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1271 ([% tt_authors.size | html %])
1272 [% # Use another TT vmethod to join & print the names & comma separators -%]
1273 [% tt_authors.join(', ') | html %]
1277 Then hit "Reload" in your browser (note that you don't need to reload
1278 the development server or use the C<-r> option when updating TT
1279 templates) and you should now see the number of authors each book has
1280 along with a comma-separated list of the authors' last names. (If you
1281 didn't leave the development server running from the previous step,
1282 you will obviously need to start it before you can refresh your
1285 If you are still running the development server with C<DBIC_TRACE>
1286 enabled, you should also now see five more C<SELECT> statements in the
1287 debug output (one for each book as the authors are being retrieved by
1290 SELECT me.id, me.title, me.rating FROM books me:
1291 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1292 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '1'
1293 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1294 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '2'
1295 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1296 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '3'
1297 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1298 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '4'
1299 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1300 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '5'
1302 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1303 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1304 and > and avoid various types of dangerous hacks against your
1305 application. In a real application, you would probably want to put
1306 "| html" at the end of every field where a user has control over the
1307 information that can appear in that field (and can therefore inject
1308 markup or code if you don't "neutralize" those fields). In addition to
1309 "| html", Template Toolkit has a variety of other useful filters that
1310 can found in the documentation for
1311 L<Template::Filters|Template::Filters>.
1314 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1316 In some situations, it can be useful to run your application and
1317 display a page without using a browser. Catalyst lets you do this
1318 using the C<scripts/myapp_test.pl> script. Just supply the URL you
1319 wish to display and it will run that request through the normal
1320 controller dispatch logic and use the appropriate view to render the
1321 output (obviously, complex pages may dump a lot of text to your
1322 terminal window). For example, if you type:
1324 $ script/myapp_test.pl "/books/list"
1326 You should get the same text as if you visited
1327 L<http://localhost:3000/books/list> with the normal development server
1328 and asked your browser to view the page source.
1331 =head1 OPTIONAL INFORMATION
1333 B<NOTE: The rest of this part of the tutorial is optional. You can
1334 skip to Part 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
1338 =head2 Using C<RenderView> for the Default View
1340 Once your controller logic has processed the request from a user, it
1341 forwards processing to your view in order to generate the appropriate
1342 response output. Catalyst uses
1343 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1344 default to automatically performs this operation. If you look in
1345 C<lib/MyApp/Controller/Root.pm>, you should see the empty
1346 definition for the C<sub end> method:
1348 sub end : ActionClass('RenderView') {}
1350 The following bullet points provide a quick overview of the
1351 C<RenderView> process:
1357 C<Root.pm> is designed to hold application-wide logic.
1361 At the end of a given user request, Catalyst will call the most specific
1362 C<end> method that's appropriate. For example, if the controller for a
1363 request has an C<end> method defined, it will be called. However, if
1364 the controller does not define a controller-specific C<end> method, the
1365 "global" C<end> method in C<Root.pm> will be called.
1369 Because the definition includes an C<ActionClass> attribute, the
1370 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1371 will be executed B<after> any code inside the definition of C<sub end>
1372 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1373 for more information on C<ActionClass>.
1377 Because C<sub end> is empty, this effectively just runs the default
1378 logic in C<RenderView>. However, you can easily extend the
1379 C<RenderView> logic by adding your own code inside the empty method body
1380 (C<{}>) created by the Catalyst Helpers when we first ran the
1381 C<catalyst.pl> to initialize our application. See
1382 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1383 detailed information on how to extended C<RenderView> in C<sub end>.
1388 =head2 Using The Default Template Name
1390 By default, C<Catalyst::View::TT> will look for a template that uses the
1391 same name as your controller action, allowing you to save the step of
1392 manually specifying the template name in each action. For example, this
1393 would allow us to remove the
1394 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1395 C<list> action in the Books controller. Open
1396 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1397 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1402 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1407 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1408 # 'Context' that's used to 'glue together' the various components
1409 # that make up the application
1410 my ($self, $c) = @_;
1412 # Retrieve all of the book records as book model objects and store in the
1413 # stash where they can be accessed by the TT template
1414 $c->stash->{books} = [$c->model('DB::Books')->all];
1416 # Set the TT template to use. You will almost always want to do this
1417 # in your action methods (actions methods respond to user input in
1418 # your controllers).
1419 #$c->stash->{template} = 'books/list.tt2';
1423 You should now be able to restart the development server as per the
1424 previous section and access the L<http://localhost:3000/books/list>
1427 B<NOTE:> Please note that if you use the default template technique,
1428 you will B<not> be able to use either the C<$c-E<gt>forward> or
1429 the C<$c-E<gt>detach> mechanisms (these are discussed in Part 2 and
1430 Part 9 of the Tutorial).
1433 =head2 Return To A Manually-Specified Template
1435 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1436 later in the tutorial, you should remove the comment from the
1437 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1439 $c->stash->{template} = 'books/list.tt2';
1441 Then delete the C<TEMPLATE_EXTENSION> line in
1442 C<lib/MyApp/View/TT.pm>.
1444 You should then be able to restart the development server and
1445 access L<http://localhost:3000/books/list> in the same manner as
1446 with earlier sections.
1451 Kennedy Clark, C<hkclark@gmail.com>
1453 Please report any errors, issues or suggestions to the author. The
1454 most recent version of the Catalyst Tutorial can be found at
1455 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
1457 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1458 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).