3 Catalyst::Manual::Tutorial::MoreCatalystBasics - Catalyst Tutorial - Chapter 3: More Catalyst Application Development Basics
8 This is B<Chapter 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 chapter of the tutorial builds on the work done in Chapter 2 to
60 explore some features that are more typical of "real world" web
61 applications. From this chapter of the tutorial onward, we will be
62 building a simple book database application. Although the application
63 will be too limited to be of use to anyone, it should provide a basic
64 environment where we can explore a variety of features used in
65 virtually all web applications.
67 You can check out 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 L<Catalyst::Manual::Tutorial::Intro/CATALYST INSTALLATION> before
73 doing the rest of this tutorial. Although the tutorial should work
74 correctly under most any recent version of Perl running on any
75 operating system, the tutorial has been written using Debian 5 and
76 tested to be sure it runs correctly in this environment.
79 =head1 CREATE A NEW APPLICATION
81 The remainder of the tutorial will build an application called C<MyApp>.
82 First use the Catalyst C<catalyst.pl> script to initialize the framework
83 for the C<MyApp> application (make sure you aren't still inside the
84 directory of the C<Hello> application from the previous chapter of the
85 tutorial or in a directory that already has a "MyApp" subdirectory):
89 created "MyApp/script"
93 created "MyApp/script/myapp_create.pl"
96 This creates a similar skeletal structure to what we saw in Chapter 2 of
97 the tutorial, except with C<MyApp> and C<myapp> substituted for
98 C<Hello> and C<hello>.
101 =head1 EDIT THE LIST OF CATALYST PLUGINS
103 One of the greatest benefits of Catalyst is that it has such a large
104 library of plugins and base classes available. Plugins are used to
105 seamlessly integrate existing Perl modules into the overall Catalyst
106 framework. In general, they do this by adding additional methods to the
107 C<context> object (generally written as C<$c>) that Catalyst passes to
108 every component throughout the framework.
110 By default, Catalyst enables three plugins/flags:
118 Enables the Catalyst debug output you saw when we started the
119 C<script/myapp_server.pl> development server earlier. You can remove
120 this item when you place your application into production.
122 As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
123 Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
124 line of your application class will be plugins, Catalyst supports a
125 limited number of flag options (of these, C<-Debug> is the most
126 common). See the documentation for C<Catalyst.pm> to get details on
127 other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
129 If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
132 B<TIP>: Depending on your needs, it can be helpful to permanently
133 remove C<-Debug> from C<lib/MyApp.pm> and then use the C<-d> option
134 to C<script/myapp_server.pl> to re-enable it just for the development
135 server. We will not be using that approach in the tutorial, but feel
136 free to make use of it in your own projects.
140 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
142 C<ConfigLoader> provides an automatic way to load configurable
143 parameters for your application from a central
144 L<Config::General|Config::General> file (versus having the values
145 hard-coded inside your Perl modules). Config::General uses syntax
146 very similar to Apache configuration files. We will see how to use
147 this feature of Catalyst during the authentication and authorization
148 sections (Chapter 5 and Chapter 6).
150 B<IMPORTANT NOTE:> If you are using a version of
151 L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, be aware
152 that Catalyst changed the default format from YAML to the more
153 straightforward C<Config::General> style. This tutorial uses the
154 newer C<myapp.conf> file for C<Config::General>. However, Catalyst
155 supports both formats and will automatically use either C<myapp.conf>
156 or C<myapp.yml> (or any other format supported by
157 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
158 L<Config::Any|Config::Any>). If you are using a version of
159 Catalyst::Devel prior to 1.06, you can convert to the newer format by
160 simply creating the C<myapp.conf> file manually and deleting
161 C<myapp.yml>. The default contents of the C<myapp.conf> you create
162 should only consist of one line:
166 B<TIP>: This script can be useful for converting between configuration
169 perl -Ilib -e 'use MyApp; use Config::General;
170 Config::General->new->save_file("myapp.conf", MyApp->config);'
174 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
176 C<Static::Simple> provides an easy way to serve static content, such
177 as images and CSS files, from the development server.
181 For our application, we want to add one new plugin into the mix. To
182 do this, edit C<lib/MyApp.pm> (this file is generally referred to as
183 your I<application class>) and delete the lines with:
185 use Catalyst qw/-Debug
189 Then replace it with:
192 use Catalyst qw/-Debug
199 B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
200 techniques to load these plugins/flags. For example, you might see
203 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
205 Don't let these variations confuse you -- they all accomplish the same
208 This tells Catalyst to start using one new plugin,
209 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
210 stack trace to the standard Catalyst "debug screen" (the screen
211 Catalyst sends to your browser when an error occurs). Be aware that
212 L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
213 browser, not in the console window from which you're running your
214 application, which is where logging output usually goes.
222 C<__PACKAGE__> is just a shorthand way of referencing the name of the
223 package where it is used. Therefore, in C<MyApp.pm>, C<__PACKAGE__>
224 is equivalent to C<MyApp>.
228 You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
229 before you put your application into production, but it can be helpful
234 When specifying plugins on the C<__PACKAGE__-E<gt>setup> line, you can
235 omit C<Catalyst::Plugin::> from the name. Additionally, you can
236 spread the plugin names across multiple lines as shown here, or place
237 them all on one (or more) lines as with the default configuration.
242 =head1 CREATE A CATALYST CONTROLLER
244 As discussed earlier, controllers are where you write methods that
245 interact with user input. Typically, controller methods respond to
246 C<GET> and C<POST> requests from the user's web browser.
248 Use the Catalyst C<create> script to add a controller for book-related
251 $ script/myapp_create.pl controller Books
252 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
253 exists "/home/me/MyApp/script/../t"
254 created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm"
255 created "/home/me/MyApp/script/../t/controller_Books.t"
257 Then edit C<lib/MyApp/Controller/Books.pm> (as discussed in Chapter 2 of
258 the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
259 each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
260 and add the following method to the controller:
264 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
269 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
270 # 'Context' that's used to 'glue together' the various components
271 # that make up the application
274 # Retrieve all of the book records as book model objects and store in the
275 # stash where they can be accessed by the TT template
276 # $c->stash->{books} = [$c->model('DB::Books')->all];
277 # But, for now, use this code until we create the model later
278 $c->stash->{books} = '';
280 # Set the TT template to use. You will almost always want to do this
281 # in your action methods (action methods respond to user input in
283 $c->stash->{template} = 'books/list.tt2';
286 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
287 cutting and pasting example code from POD-based documents.
289 Programmers experienced with object-oriented Perl should recognize
290 C<$self> as a reference to the object where this method was called.
291 On the other hand, C<$c> will be new to many Perl programmers who have
292 not used Catalyst before (it's sometimes written as C<$context>). The
293 Context object is automatically passed to all Catalyst components. It
294 is used to pass information between components and provide access to
295 Catalyst and plugin functionality.
297 Catalyst actions are regular Perl methods, but they make use of
298 attributes (the "C<: Local>" next to the "C<sub list>" in the code
299 above) to provide additional information to the Catalyst dispatcher
300 logic (note that the space between the colon and the attribute name is
301 optional; you will see attributes written both ways). Most Catalyst
302 Controllers use one of five action types:
308 B<:Private> -- Use C<:Private> for methods that you want to make into
309 an action, but you do not want Catalyst to directly expose
310 to your users. Catalyst will not map C<:Private> methods to a URI.
311 Use them for various sorts of "special" methods (the C<begin>,
312 C<auto>, etc. discussed below) or for methods you want to be able to
313 C<forward> or C<detach> to. (If the method is a plain old "helper
314 method" that you don't want to be an action at all, then just define
315 the method without any attribute -- you can call it in your code, but
316 the Catalyst dispatcher will ignore it.)
318 There are five types of "special" build-in C<:Private> actions:
319 C<begin>, C<end>, C<default>, C<index>, and C<auto>.
325 With C<begin>, C<end>, C<default>, C<index> private actions, only the
326 most specific action of each type will be called. For example, if you
327 define a C<begin> action in your controller it will I<override> a
328 C<begin> action in your application/root controller -- I<only> the
329 action in your controller will be called.
333 Unlike the other actions where only a single method is called for each
334 request, I<every> auto action along the chain of namespaces will be
335 called. Each C<auto> action will be called I<from the application/root
336 controller down through the most specific class>.
342 B<:Path> -- C<:Path> actions let you map a method to an explicit URI
343 path. For example, "C<:Path('list')>" in
344 C<lib/MyApp/Controller/Books.pm> would match on the URL
345 C<http://localhost:3000/books/list> but "C<:Path('/list')>" would match
346 on C<http://localhost:3000/list>. You can use C<:Args()> to specify
347 how many arguments an action should accept. See
348 L<Catalyst::Manual::Intro/Action_types> for more information and a few
353 B<:Local> -- C<:Local> is merely a shorthand for
354 "C<:Path('_name_of_method_')>". For example, these are equivalent:
355 "C<sub create_book :Local {...}>" and
356 "C<sub create_book :Path('create_book') {...}>".
360 B<:Global> -- C<:Global> is merely a shorthand for
361 "C<:Path('/_name_of_method_')>". For example, these are equivalent:
362 "C<sub create_book :Global {...}>" and
363 "C<sub create_book :Path('/create_book') {...}>".
367 B<:Chained> -- Newer Catalyst applications tend to use the Chained
368 dispatch form of action types because of its power and flexibility.
369 It allows a series of controller methods to be automatically dispatched
370 to service a single user request. See
371 L<Catalyst::Manual::Tutorial::BasicCRUD|Catalyst::Manual::Tutorial::BasicCRUD>
372 and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
373 for more information on chained actions.
377 You should refer to L<Catalyst::Manual::Intro/Action_types> for
378 additional information and for coverage of some lesser-used action
379 types not discussed here (C<Regex> and C<LocalRegex>).
382 =head1 CATALYST VIEWS
384 As mentioned in Chapter 2 of the tutorial, views are where you render
385 output, typically for display in the user's web browser (but also
386 possibly using into output-generation systems, such as PDF or JSON).
387 The code in C<lib/MyApp/View> selects the I<type> of view to use, with
388 the actual rendering template found in the C<root> directory. As with
389 virtually every aspect of Catalyst, options abound when it comes to the
390 specific view technology you adopt inside your application. However,
391 most Catalyst applications use the Template Toolkit, known as TT (for
392 more information on TT, see L<http://www.template-toolkit.org>). Other
393 somewhat popular view technologies include Mason
394 (L<http://www.masonhq.com> and L<http://www.masonbook.com>) and
395 L<HTML::Template> (L<http://html-template.sourceforge.net>).
398 =head2 Create a Catalyst View
400 When using TT for the Catalyst view, there are two main helper scripts:
406 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
410 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
414 Both helpers are similar. C<TT> creates the C<lib/MyApp/View/TT.pm>
415 file and leaves the creation of any hierarchical template organization
416 entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
417 test cases will be discussed in Chapter 8.) C<TTSite>, on the other hand,
418 creates a modular and hierarchical view layout with
419 separate Template Toolkit (TT) files for common header and footer
420 information, configuration values, a CSS stylesheet, and more.
422 While C<TTSite> was useful to bootstrap a project, its use is now
423 deprecated and it should be considered historical. For most Catalyst
424 applications it adds redundant functionality and structure; many in the
425 Catalyst community recommend that it's easier to learn both Catalyst and
426 Template Toolkit if you use the more basic C<TT> approach.
427 Consequently, this tutorial will use "plain old TT."
429 Enter the following command to enable the C<TT> style of view
430 rendering for this tutorial:
432 $ script/myapp_create.pl view TT TT
433 exists "/home/me/MyApp/script/../lib/MyApp/View"
434 exists "/home/me/MyApp/script/../t"
435 created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm"
436 created "/home/me/MyApp/script/../t/view_TT.t"
438 This simply creates a view called C<TT> (the second 'TT' argument) in
439 a file called C<TT.pm> (the first 'TT' argument). It is now up to you
440 to decide how you want to structure your view layout. For the
441 tutorial, we will start with a very simple TT template to initially
442 demonstrate the concepts, but quickly migrate to a more typical
443 "wrapper page" type of configuration (where the "wrapper" controls the
444 overall "look and feel" of your site from a single file or set of
447 Edit C<lib/MyApp/View/TT.pm> and you should see that the default
448 contents contains something similar to the following:
450 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
452 And update it to match:
455 # Change default TT extension
456 TEMPLATE_EXTENSION => '.tt2',
457 # Set the location for TT files
459 MyApp->path_to( 'root', 'src' ),
463 B<NOTE:> Make sure to add a comma after '.tt2' outside the single
466 This changes the default extension for Template Toolkit from '.tt' to
467 '.tt2' and changes the base directory for your template files from
468 C<root> to C<root/src>. These changes from the default are done mostly
469 to facilitate the application we're developing in this tutorial; as with
470 most things Perl, there's more than one way to do it...
472 B<Note:> We will use C<root/src> as the base directory for our
473 template files, which a full naming convention of
474 C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
475 use C<root/> as the base (with a full filename pattern of
476 C<root/_controller_name_/_action_name_.tt2>).
479 =head2 Create a TT Template Page
481 First create a directory for book-related TT templates:
483 $ mkdir -p root/src/books
485 Then create C<root/src/books/list.tt2> in your editor and enter:
487 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
488 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
489 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
490 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
492 [% # Provide a title -%]
493 [% META title = 'Book List' -%]
496 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
497 [% # Display each book in a table row %]
498 [% FOREACH book IN books -%]
500 <td>[% book.title %]</td>
501 <td>[% book.rating %]</td>
507 As indicated by the inline comments above, the C<META title> line uses
508 TT's META feature to provide a title to the "wrapper" that we will
509 create later. Meanwhile, the C<FOREACH> loop iterates through each
510 C<book> model object and prints the C<title> and C<rating> fields.
512 The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
513 supports a wide variety of directives for "calling" other files,
514 looping, conditional logic, etc. In general, TT simplifies the usual
515 range of Perl operators down to the single dot (C<.>) operator. This
516 applies to operations as diverse as method calls, hash lookups, and list
518 L<http://search.cpan.org/perldoc?Template::Manual::Variables> for
519 details and examples). In addition to the usual C<Template> module Pod
520 documentation, you can access the TT manual at
521 L<http://search.cpan.org/perldoc?Template::Manual>.
523 B<TIP:> While you can build all sorts of complex logic into your TT
524 templates, you should in general keep the "code" part of your templates
525 as simple as possible. If you need more complex logic, create helper
526 methods in your model that abstract out a set of code into a single call
527 from your TT template. (Note that the same is true of your controller
528 logic as well -- complex sections of code in your controllers should
529 often be pulled out and placed into your model objects.)
532 =head2 Test Run The Application
534 To test your work so far, first start the development server:
536 $ script/myapp_server.pl
538 Then point your browser to L<http://localhost:3000> and you should
539 still get the Catalyst welcome page. Next, change the URL in your
540 browser to L<http://localhost:3000/books/list>. If you have
541 everything working so far, you should see a web page that displays
542 nothing other than our column headers for "Title", "Rating", and
543 "Author(s)" -- we will not see any books until we get the database and
546 If you run into problems getting your application to run correctly, it
547 might be helpful to refer to some of the debugging techniques covered in
548 the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the
552 =head1 CREATE A SQLITE DATABASE
554 In this step, we make a text file with the required SQL commands to
555 create a database table and load some sample data. We will use SQLite,
556 a popular database that is lightweight and easy to use. Open
557 C<myapp01.sql> in your editor and enter:
560 -- Create a very simple database to hold book and author information
563 id INTEGER PRIMARY KEY,
567 -- 'book_authors' is a many-to-many join table between books & authors
568 CREATE TABLE book_authors (
571 PRIMARY KEY (book_id, author_id)
573 CREATE TABLE authors (
574 id INTEGER PRIMARY KEY,
579 --- Load some sample data
581 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
582 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
583 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
584 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
585 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
586 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
587 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
588 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
589 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
590 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
591 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
592 INSERT INTO authors VALUES (7, 'Nathan', 'Torkington');
593 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
594 INSERT INTO book_authors VALUES (1, 1);
595 INSERT INTO book_authors VALUES (1, 2);
596 INSERT INTO book_authors VALUES (1, 3);
597 INSERT INTO book_authors VALUES (2, 4);
598 INSERT INTO book_authors VALUES (3, 5);
599 INSERT INTO book_authors VALUES (4, 6);
600 INSERT INTO book_authors VALUES (4, 7);
601 INSERT INTO book_authors VALUES (5, 8);
603 Then use the following command to build a C<myapp.db> SQLite database:
605 $ sqlite3 myapp.db < myapp01.sql
607 If you need to create the database more than once, you probably want to
608 issue the C<rm myapp.db> command to delete the database before you use
609 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
611 Once the C<myapp.db> database file has been created and initialized, you
612 can use the SQLite command line environment to do a quick dump of the
617 Enter ".help" for instructions
618 sqlite> select * from books;
619 1|CCSP SNRS Exam Certification Guide|5
620 2|TCP/IP Illustrated, Volume 1|5
621 3|Internetworking with TCP/IP Vol.1|4
623 5|Designing with Web Standards|5
629 $ sqlite3 myapp.db "select * from books"
630 1|CCSP SNRS Exam Certification Guide|5
631 2|TCP/IP Illustrated, Volume 1|5
632 3|Internetworking with TCP/IP Vol.1|4
634 5|Designing with Web Standards|5
636 As with most other SQL tools, if you are using the full "interactive"
637 environment you need to terminate your SQL commands with a ";" (it's not
638 required if you do a single SQL statement on the command line). Use
639 ".q" to exit from SQLite from the SQLite interactive mode and return to
640 your OS command prompt.
642 For using other databases, such as PostgreSQL or MySQL, see
643 L<Appendix 2|Catalyst::Manual::Tutorial::Appendices>.
646 =head1 DATABASE ACCESS WITH DBIx::Class
648 Catalyst can be used with virtually any form of datastore available
649 via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
650 can be used to access databases through the traditional Perl C<DBI>
651 interface or you can use a model to access files of any type on the
652 filesystem. However, most Catalyst applications use some form of
653 object-relational mapping (ORM) technology to create objects
654 associated with tables in a relational database. Matt Trout's
655 L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
656 as the Perl-based ORM technology of choice. Most new Catalyst
657 applications rely on DBIx::Class, as will this tutorial.
659 Although DBIx::Class has included support for a C<create=dynamic> mode
660 to automatically read the database structure every time the
661 application starts, it's use is no longer recommended. While it can
662 make for "flashy" demos, the use of the C<create=static> mode we use
663 below can be implemented just as quickly and provides many advantages
664 (such as the ability to add your own methods to the overall DBIC
665 framework, a technique that we see in Chapter 4).
668 =head2 Make Sure You Have a Recent Version of the DBIx::Class Model
670 First, let's be sure we have a recent version of the DBIC helper,
671 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
672 running this command:
674 $ perl -MCatalyst::Model::DBIC::Schema -e \
675 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
678 If you don't have version 0.23 or higher, please run this command
679 to install it directly from CPAN:
681 $ sudo cpan Catalyst::Model::DBIC::Schema
683 And re-run the version print command to verify that you are now at
687 =head2 Create Static DBIx::Class Schema Files
689 Before you continue, make sure your C<myapp.db> database file is in
690 the application's topmost directory. Now use the model helper with
691 the C<create=static> option to read the database with
692 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
693 automatically build the required files for us:
695 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
696 create=static components=TimeStamp dbi:SQLite:myapp.db
697 exists "/home/me/MyApp/script/../lib/MyApp/Model"
698 exists "/home/me/MyApp/script/../t"
699 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
700 Schema dump completed.
701 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
702 created "/home/me/MyApp/script/../t/model_DB.t"
704 The C<script/myapp_create.pl> command breaks down like this:
710 C<DB> is the name of the model class to be created by the helper in
715 C<DBIC::Schema> is the type of the model to create.
719 C<MyApp::Schema> is the name of the DBIC schema file written to
720 C<lib/MyApp/Schema.pm>.
724 C<create=static> causes
725 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
726 load the schema as it runs and then write that information out
731 C<components=TimeStamp> causes the help to include the
732 L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp> DBIC component.
736 And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
741 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
742 only contains a call to the C<load_namespaces> method. You will also
743 find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
744 has a subdirectory called "Result". This "Result" subdirectory then
745 has files named according to each of the tables in our simple database
746 (C<Authors.pm>, C<BookAuthors.pm>, and C<Books.pm>). These three
747 files are called "Result Classes" in DBIx::Class nomenclature. Although the
748 Result Class files are named after tables in our database, the classes
749 correspond to the I<row-level data> that is returned by DBIC (more on
750 this later, especially in
751 L<Catalyst::Manual::Tutorial::BasicCRUD/EXPLORING THE POWER OF DBIC>).
753 The idea with the Result Source files created under
754 C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
755 edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
756 warning. If you place all of your changes below that point in the
757 file, you can regenerate the automatically created information at the
758 top of each file should your database structure get updated.
760 Also note the "flow" of the model information across the various files
761 and directories. Catalyst will initially load the model from
762 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
763 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the
764 call to C<load_namespaces> in C<Schema.pm> will load each of the
765 "Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
766 The final outcome is that Catalyst will dynamically create three
767 table-specific Catalyst models every time the application starts (you
768 can see these three model files listed in the debug output generated
769 when you launch the application).
771 B<NOTE:> Older versions of
772 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
773 deprecated DBIx::Class C<load_classes> technique instead of the newer
774 C<load_namspaces>. For new applications, please try to use
775 C<load_namespaces> since it more easily supports a very useful DBIC
776 technique called "ResultSet Classes." If you need to convert an
777 existing application from "load_classes" to "load_namespaces," you can
778 use this process to automate the migration (but first make sure you
779 have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
781 $ # First delete the existing schema file to disable "compatibility" mode
782 $ rm lib/MyApp/Schema.pm
784 $ # Then re-run the helper to build the files for "load_namespaces"
785 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
786 create=static components=TimeStamp dbi:SQLite:myapp.db
788 $ # Now convert the existing files over
789 $ cd lib/MyApp/Schema
790 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
791 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
792 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
795 $ # And finally delete the old files
796 $ rm lib/MyApp/Schema/*.pm
798 The "C<perl -MIO::ALL ...>" script will copy all the customized
799 relationship (and other) information below "C<# DO NOT MODIFY>" line
800 from the old files in C<lib/MyApp/Schema> to the new files in
801 C<lib/MyApp/Schema/Result> (we will be starting to add some
802 "customized relationship information in the section below).
805 =head1 ENABLE THE MODEL IN THE CONTROLLER
807 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
808 left disabled earlier so that your version matches the following (un-
809 comment the line containing C<[$c-E<gt>model('DB::Books')-E<gt>all]>
810 and delete the next 2 lines):
814 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
819 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
820 # 'Context' that's used to 'glue together' the various components
821 # that make up the application
824 # Retrieve all of the book records as book model objects and store in the
825 # stash where they can be accessed by the TT template
826 $c->stash->{books} = [$c->model('DB::Books')->all];
828 # Set the TT template to use. You will almost always want to do this
829 # in your action methods (action methods respond to user input in
831 $c->stash->{template} = 'books/list.tt2';
834 B<TIP>: You may see the C<$c-E<gt>model('DB::Books')> un-commented
835 above written as C<$c-E<gt>model('DB')-E<gt>resultset('Books')>. The
836 two are equivalent. Either way, C<$c-E<gt>model> returns a
837 L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
838 against the database and iterating over the set of results that is
841 We are using the C<-E<gt>all> to fetch all of the books. DBIC
842 supports a wide variety of more advanced operations to easily do
843 things like filtering and sorting the results. For example, the
844 following could be used to sort the results by descending title:
846 $c->model('DB::Books')->search({}, {order_by => 'title DESC'});
848 Some other examples are provided in
849 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
850 additional information found at L<DBIx::Class::ResultSet/search>,
851 L<DBIx::Class::Manual::FAQ/Searching>,
852 L<DBIx::Class::Manual::Intro|DBIx::Class::Manual::Intro>
853 and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
856 =head2 Test Run The Application
858 First, let's enable an environment variable that causes DBIx::Class to
859 dump the SQL statements used to access the database. This is a
860 helpful trick when you are trying to debug your database-oriented
863 $ export DBIC_TRACE=1
865 This assumes you are using bash as your shell -- adjust accordingly if
866 you are using a different shell (for example, under tcsh, use
867 C<setenv DBIC_TRACE 1>).
869 B<NOTE:> You can also set this in your code using
870 C<$class-E<gt>storage-E<gt>debug(1);>. See
871 L<DBIx::Class::Manual::Troubleshooting> for details (including options
872 to log to a file instead of displaying to the Catalyst development server
875 Then launch the Catalyst development server. The log output should
876 display something like:
878 $ script/myapp_server.pl
879 [debug] Debug messages enabled
880 [debug] Statistics enabled
881 [debug] Loaded plugins:
882 .----------------------------------------------------------------------------.
883 | Catalyst::Plugin::ConfigLoader 0.20 |
884 | Catalyst::Plugin::StackTrace 0.08 |
885 | Catalyst::Plugin::Static::Simple 0.20 |
886 '----------------------------------------------------------------------------'
888 [debug] Loaded dispatcher "Catalyst::Dispatcher"
889 [debug] Loaded engine "Catalyst::Engine::HTTP"
890 [debug] Found home "/home/me/MyApp"
891 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
892 [debug] Loaded components:
893 .-----------------------------------------------------------------+----------.
895 +-----------------------------------------------------------------+----------+
896 | MyApp::Controller::Books | instance |
897 | MyApp::Controller::Root | instance |
898 | MyApp::Model::DB | instance |
899 | MyApp::Model::DB::Authors | class |
900 | MyApp::Model::DB::BookAuthors | class |
901 | MyApp::Model::DB::Books | class |
902 | MyApp::View::TT | instance |
903 '-----------------------------------------------------------------+----------'
905 [debug] Loaded Private actions:
906 .----------------------+--------------------------------------+--------------.
907 | Private | Class | Method |
908 +----------------------+--------------------------------------+--------------+
909 | /default | MyApp::Controller::Root | default |
910 | /end | MyApp::Controller::Root | end |
911 | /index | MyApp::Controller::Root | index |
912 | /books/index | MyApp::Controller::Books | index |
913 | /books/list | MyApp::Controller::Books | list |
914 '----------------------+--------------------------------------+--------------'
916 [debug] Loaded Path actions:
917 .-------------------------------------+--------------------------------------.
919 +-------------------------------------+--------------------------------------+
922 | /books | /books/index |
923 | /books/list | /books/list |
924 '-------------------------------------+--------------------------------------'
926 [info] MyApp powered by Catalyst 5.71000
927 You can connect to your server at http://debian:3000
929 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
930 the 'base' directory of your application, not inside the C<script>
931 directory itself or it will not be able to locate the C<myapp.db>
932 database file. You can use a fully qualified or a relative path to
933 locate the database file, but we did not specify that when we ran the
934 model helper earlier.
936 Some things you should note in the output above:
942 Catalyst::Model::DBIC::Schema dynamically created three model classes,
943 one to represent each of the three tables in our database
944 (C<MyApp::Model::DB::Authors>, C<MyApp::Model::DB::BookAuthors>,
945 and C<MyApp::Model::DB::Books>).
949 The "list" action in our Books controller showed up with a path of
954 Point your browser to L<http://localhost:3000> and you should still get
955 the Catalyst welcome page.
957 Next, to view the book list, change the URL in your browser to
958 L<http://localhost:3000/books/list>. You should get a list of the five
959 books loaded by the C<myapp01.sql> script above without any formatting.
960 The rating for each book should appear on each row, but the "Author(s)"
961 column will still be blank (we will fill that in later).
963 Also notice in the output of the C<script/myapp_server.pl> that
964 DBIx::Class used the following SQL to retrieve the data:
966 SELECT me.id, me.title, me.rating FROM books me
968 because we enabled DBIC_TRACE.
970 You now have the beginnings of a simple but workable web application.
971 Continue on to future sections and we will develop the application
975 =head1 CREATE A WRAPPER FOR THE VIEW
977 When using TT, you can (and should) create a wrapper that will
978 literally wrap content around each of your templates. This is
979 certainly useful as you have one main source for changing things that
980 will appear across your entire site/application instead of having to
981 edit many individual files.
984 =head2 Configure TT.pm For The Wrapper
986 In order to create a wrapper, you must first edit your TT view and
987 tell it where to find your wrapper file. Your TT view is located in
988 C<lib/MyApp/View/TT.pm>.
990 Edit C<lib/MyApp/View/TT.pm> and change it to match the following:
993 # Change default TT extension
994 TEMPLATE_EXTENSION => '.tt2',
995 # Set the location for TT files
997 MyApp->path_to( 'root', 'src' ),
999 # Set to 1 for detailed timer stats in your HTML as comments
1001 # This is your wrapper template located in the 'root/src'
1002 WRAPPER => 'wrapper.tt2',
1006 =head2 Create the Wrapper Template File and Stylesheet
1008 Next you need to set up your wrapper template. Basically, you'll want
1009 to take the overall layout of your site and put it into this file.
1010 For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1012 <?xml version="1.0" encoding="UTF-8"?>
1013 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1014 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
1016 <title>[% template.title or "My Catalyst App!" %]</title>
1017 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1023 [%# Your logo could go here -%]
1024 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1025 [%# Insert the page title -%]
1026 <h1>[% template.title or site.title %]</h1>
1029 <div id="bodyblock">
1033 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1034 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1036 </div><!-- end menu -->
1039 [%# Status and error messages %]
1040 <span class="message">[% status_msg %]</span>
1041 <span class="error">[% error_msg %]</span>
1042 [%# This is where TT will stick all of your template's contents. -%]
1044 </div><!-- end content -->
1045 </div><!-- end bodyblock -->
1047 <div id="footer">Copyright (c) your name goes here</div>
1048 </div><!-- end outer -->
1053 Notice the status and error message sections in the code above:
1055 <span class="status">[% status_msg %]</span>
1056 <span class="error">[% error_msg %]</span>
1058 If we set either message in the Catalyst stash (e.g.,
1059 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1060 will be displayed whenever any view used by that request is rendered.
1061 The C<message> and C<error> CSS styles can be customized to suit your
1062 needs in the C<root/static/css/main.css> file we create below.
1070 The Catalyst stash only lasts for a single HTTP request. If
1071 you need to retain information across requests you can use
1072 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
1073 Catalyst sessions in the Authentication chapter of the tutorial).
1077 Although it is beyond the scope of this tutorial, you may wish to use
1078 a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
1079 Dojo (L<http://www.dojotoolkit.org>).
1084 =head3 Create A Basic Stylesheet
1086 First create a central location for stylesheets under the static
1089 $ mkdir root/static/css
1091 Then open the file C<root/static/css/main.css> (the file referenced in
1092 the stylesheet href link of our wrapper above) and add the following
1111 background-color: #ddd;
1117 padding: 0 0 50% 5px;
1118 font-weight: normal;
1119 background-color: #ddd;
1132 You may wish to check out a "CSS Framework" like Emastic
1133 (L<http://code.google.com/p/emastic/>) as a way to quickly
1134 provide lots of high-quality CSS functionality.
1137 =head2 Test Run The Application
1139 Restart the development server and hit "Reload" in your web browser
1140 and you should now see a formatted version of our basic book list.
1141 Although our wrapper and stylesheet are obviously very simple, you
1142 should see how it allows us to control the overall look of an entire
1143 website from two central files. To add new pages to the site, just
1144 provide a template that fills in the C<content> section of our wrapper
1145 template -- the wrapper will provide the overall feel of the page.
1148 =head2 Updating the Generated DBIx::Class Result Class Files
1150 Let's manually add some relationship information to the auto-generated
1151 Result Class files. (Note: if you are using a database other than
1152 SQLite, such as PostgreSQL, then the relationship could have been
1153 automatically placed in the Result Class files. If so, you can skip
1154 this step.) First edit C<lib/MyApp/Schema/Result/Books.pm> and add the
1155 following text below the C<# You can replace this text...> comment:
1158 # Set relationships:
1163 # 1) Name of relationship, DBIC will create accessor with this name
1164 # 2) Name of the model class referenced by this relationship
1165 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1166 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthors', 'book_id');
1170 # 1) Name of relationship, DBIC will create accessor with this name
1171 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1172 # 3) Name of belongs_to() relationship in model class of has_many() above
1173 # You must already have the has_many() defined to use a many_to_many().
1174 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1177 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1178 file. As with any Perl package, we need to end the last line with
1179 a statement that evaluates to C<true>. This is customarily done with
1180 C<1;> on a line by itself.
1182 C<Important Note:> Although this tutorial uses plural names for both
1183 the names of the SQL tables and therefore the Result Classes (after
1184 all, C<Schema::Loader> automatically named the Result Classes from the
1185 names of the SQL tables it found), DBIx::Class users prefer singular
1186 names for these items. B<Please try to use singular table and DBIC
1187 model/Result Class names in your applications.> This tutorial will
1188 migrate to singular names as soon as possible (patches welcomed).
1189 B<Note that while singular is preferred for the DBIC model, plural is
1190 perfectly acceptable for the names of the controller classes.> After
1191 all, the C<Books.pm> controller operates on multiple books.
1193 This code defines both a C<has_many> and a C<many_to_many>
1194 relationship. The C<many_to_many> relationship is optional, but it
1195 makes it easier to map a book to its collection of authors. Without
1196 it, we would have to "walk" though the C<book_authors> table as in
1197 C<$book-E<gt>book_authors-E<gt>first-E<gt>author-E<gt>last_name> (we
1198 will see examples on how to use DBIx::Class objects in your code soon,
1199 but note that because C<$book-E<gt>book_authors> can return multiple
1200 authors, we have to use C<first> to display a single author).
1201 C<many_to_many> allows us to use the shorter C<$book-E<gt>authors-
1202 E<gt>first-E<gt>last_name>. Note that you cannot define a
1203 C<many_to_many> relationship without also having the C<has_many>
1204 relationship in place.
1206 Then edit C<lib/MyApp/Schema/Result/Authors.pm> and add relationship
1207 information as follows (again, be careful to put in above the C<1;> but
1208 below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1211 # Set relationships:
1216 # 1) Name of relationship, DBIC will create an accessor with this name
1217 # 2) Name of the model class referenced by this relationship
1218 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1219 __PACKAGE__->has_many(book_author => 'MyApp::Schema::Result::BookAuthors', 'author_id');
1223 # 1) Name of relationship, DBIC will create accessor with this name
1224 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1225 # 3) Name of belongs_to() relationship in model class of has_many() above
1226 # You must already have the has_many() defined to use a many_to_many().
1227 __PACKAGE__->many_to_many(books => 'book_author', 'book');
1229 Finally, do the same for the "join table,"
1230 C<lib/MyApp/Schema/Result/BookAuthors.pm>:
1233 # Set relationships:
1238 # 1) Name of relationship, DBIC will create accessor with this name
1239 # 2) Name of the model class referenced by this relationship
1240 # 3) Column name in *this* table
1241 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Books', 'book_id');
1245 # 1) Name of relationship, DBIC will create accessor with this name
1246 # 2) Name of the model class referenced by this relationship
1247 # 3) Column name in *this* table
1248 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Authors', 'author_id');
1251 =head2 Run The Application
1253 Run the Catalyst development server script with the C<DBIC_TRACE> option
1254 (it might still be enabled from earlier in the tutorial, but here is an
1255 alternate way to specify the option just in case):
1257 $ DBIC_TRACE=1 script/myapp_server.pl
1259 Make sure that the application loads correctly and that you see the
1260 three dynamically created model class (one for each of the
1261 Result Classes we created).
1263 Then hit the URL L<http://localhost:3000/books/list> with your browser
1264 and be sure that the book list is displayed via the relationships
1265 established above. You can leave the development server running for
1266 the next step if you wish.
1268 B<Note:> You will not see the authors yet because the view does not yet
1269 use the new relations. Read on to the next section where we update the
1270 template to do that.
1273 =head1 UPDATING THE VIEW
1275 Let's add a new column to our book list page that takes advantage of
1276 the relationship information we manually added to our schema files in
1277 the previous section. Edit C<root/src/books/list.tt2> and replace
1278 the "empty" tabase cell with the following:
1282 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1283 [% # loop in 'side effect notation' to load just the last names of the -%]
1284 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1285 [% # a value, so nothing will be printed here. But, if you have something -%]
1286 [% # in TT that does return a method and you don't want it printed, you -%]
1287 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1288 [% # call it and discard the return value. -%]
1289 [% tt_authors = [ ];
1290 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1291 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1292 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1293 ([% tt_authors.size | html %])
1294 [% # Use another TT vmethod to join & print the names & comma separators -%]
1295 [% tt_authors.join(', ') | html %]
1299 Then hit "Reload" in your browser (note that you don't need to reload
1300 the development server or use the C<-r> option when updating TT
1301 templates) and you should now see the number of authors each book has
1302 along with a comma-separated list of the authors' last names. (If you
1303 didn't leave the development server running from the previous step,
1304 you will obviously need to start it before you can refresh your
1307 If you are still running the development server with C<DBIC_TRACE>
1308 enabled, you should also now see five more C<SELECT> statements in the
1309 debug output (one for each book as the authors are being retrieved by
1312 SELECT me.id, me.title, me.rating FROM books me:
1313 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1314 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '1'
1315 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1316 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '2'
1317 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1318 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '3'
1319 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1320 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '4'
1321 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1322 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '5'
1324 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1325 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1326 and > and avoid various types of dangerous hacks against your
1327 application. In a real application, you would probably want to put
1328 "| html" at the end of every field where a user has control over the
1329 information that can appear in that field (and can therefore inject
1330 markup or code if you don't "neutralize" those fields). In addition to
1331 "| html", Template Toolkit has a variety of other useful filters that
1332 can found in the documentation for
1333 L<Template::Filters|Template::Filters>.
1336 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1338 In some situations, it can be useful to run your application and
1339 display a page without using a browser. Catalyst lets you do this
1340 using the C<scripts/myapp_test.pl> script. Just supply the URL you
1341 wish to display and it will run that request through the normal
1342 controller dispatch logic and use the appropriate view to render the
1343 output (obviously, complex pages may dump a lot of text to your
1344 terminal window). For example, if you type:
1346 $ script/myapp_test.pl "/books/list"
1348 You should get the same text as if you visited
1349 L<http://localhost:3000/books/list> with the normal development server
1350 and asked your browser to view the page source.
1353 =head1 OPTIONAL INFORMATION
1355 B<NOTE: The rest of this chapter of the tutorial is optional. You can
1356 skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
1360 =head2 Using 'RenderView' for the Default View
1362 Once your controller logic has processed the request from a user, it
1363 forwards processing to your view in order to generate the appropriate
1364 response output. Catalyst uses
1365 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1366 default to automatically perform this operation. If you look in
1367 C<lib/MyApp/Controller/Root.pm>, you should see the empty
1368 definition for the C<sub end> method:
1370 sub end : ActionClass('RenderView') {}
1372 The following bullet points provide a quick overview of the
1373 C<RenderView> process:
1379 C<Root.pm> is designed to hold application-wide logic.
1383 At the end of a given user request, Catalyst will call the most specific
1384 C<end> method that's appropriate. For example, if the controller for a
1385 request has an C<end> method defined, it will be called. However, if
1386 the controller does not define a controller-specific C<end> method, the
1387 "global" C<end> method in C<Root.pm> will be called.
1391 Because the definition includes an C<ActionClass> attribute, the
1392 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1393 will be executed B<after> any code inside the definition of C<sub end>
1394 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1395 for more information on C<ActionClass>.
1399 Because C<sub end> is empty, this effectively just runs the default
1400 logic in C<RenderView>. However, you can easily extend the
1401 C<RenderView> logic by adding your own code inside the empty method body
1402 (C<{}>) created by the Catalyst Helpers when we first ran the
1403 C<catalyst.pl> to initialize our application. See
1404 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1405 detailed information on how to extend C<RenderView> in C<sub end>.
1410 =head2 Using The Default Template Name
1412 By default, C<Catalyst::View::TT> will look for a template that uses the
1413 same name as your controller action, allowing you to save the step of
1414 manually specifying the template name in each action. For example, this
1415 would allow us to remove the
1416 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1417 C<list> action in the Books controller. Open
1418 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1419 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1424 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1429 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1430 # 'Context' that's used to 'glue together' the various components
1431 # that make up the application
1432 my ($self, $c) = @_;
1434 # Retrieve all of the book records as book model objects and store in the
1435 # stash where they can be accessed by the TT template
1436 $c->stash->{books} = [$c->model('DB::Books')->all];
1438 # Set the TT template to use. You will almost always want to do this
1439 # in your action methods (actions methods respond to user input in
1440 # your controllers).
1441 #$c->stash->{template} = 'books/list.tt2';
1445 You should now be able to restart the development server as per the
1446 previous section and access the L<http://localhost:3000/books/list>
1449 B<NOTE:> Please note that if you use the default template technique,
1450 you will B<not> be able to use either the C<$c-E<gt>forward> or
1451 the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1452 Chapter 9 of the Tutorial).
1455 =head2 Return To A Manually Specified Template
1457 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1458 later in the tutorial, you should remove the comment from the
1459 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1461 $c->stash->{template} = 'books/list.tt2';
1463 Then delete the C<TEMPLATE_EXTENSION> line in
1464 C<lib/MyApp/View/TT.pm>.
1466 You should then be able to restart the development server and
1467 access L<http://localhost:3000/books/list> in the same manner as
1468 with earlier sections.
1473 Kennedy Clark, C<hkclark@gmail.com>
1475 Please report any errors, issues or suggestions to the author. The
1476 most recent version of the Catalyst Tutorial can be found at
1477 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
1479 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1480 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).