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 except. 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>
506 As indicated by the inline comments above, the C<META title> line uses
507 TT's META feature to provide a title to the "wrapper" that we will
508 create later. Meanwhile, the C<FOREACH> loop iterates through each
509 C<book> model object and prints the C<title> and C<rating> fields.
511 The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
512 supports a wide variety of directives for "calling" other files,
513 looping, conditional logic, etc. In general, TT simplifies the usual
514 range of Perl operators down to the single dot (C<.>) operator. This
515 applies to operations as diverse as method calls, hash lookups, and list
517 L<http://search.cpan.org/perldoc?Template::Manual::Variables> for
518 details and examples). In addition to the usual C<Template> module Pod
519 documentation, you can access the TT manual at
520 L<http://search.cpan.org/perldoc?Template::Manual>.
522 B<TIP:> While you can build all sorts of complex logic into your TT
523 templates, you should in general keep the "code" part of your templates
524 as simple as possible. If you need more complex logic, create helper
525 methods in your model that abstract out a set of code into a single call
526 from your TT template. (Note that the same is true of your controller
527 logic as well -- complex sections of code in your controllers should
528 often be pulled out and placed into your model objects.)
531 =head2 Test Run The Application
533 To test your work so far, first start the development server:
535 $ script/myapp_server.pl
537 Then point your browser to L<http://localhost:3000> and you should
538 still get the Catalyst welcome page. Next, change the URL in your
539 browser to L<http://localhost:3000/books/list>. If you have
540 everything working so far, you should see a web page that displays
541 nothing other than our column headers for "Title", "Rating", and
542 "Author(s)" -- we will not see any books until we get the database and
545 If you run into problems getting your application to run correctly, it
546 might be helpful to refer to some of the debugging techniques covered in
547 the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the
551 =head1 CREATE A SQLITE DATABASE
553 In this step, we make a text file with the required SQL commands to
554 create a database table and load some sample data. We will use SQLite,
555 a popular database that is lightweight and easy to use. Open
556 C<myapp01.sql> in your editor and enter:
559 -- Create a very simple database to hold book and author information
562 id INTEGER PRIMARY KEY,
566 -- 'book_authors' is a many-to-many join table between books & authors
567 CREATE TABLE book_authors (
570 PRIMARY KEY (book_id, author_id)
572 CREATE TABLE authors (
573 id INTEGER PRIMARY KEY,
578 --- Load some sample data
580 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
581 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
582 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
583 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
584 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
585 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
586 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
587 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
588 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
589 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
590 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
591 INSERT INTO authors VALUES (7, 'Nathan', 'Torkington');
592 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
593 INSERT INTO book_authors VALUES (1, 1);
594 INSERT INTO book_authors VALUES (1, 2);
595 INSERT INTO book_authors VALUES (1, 3);
596 INSERT INTO book_authors VALUES (2, 4);
597 INSERT INTO book_authors VALUES (3, 5);
598 INSERT INTO book_authors VALUES (4, 6);
599 INSERT INTO book_authors VALUES (4, 7);
600 INSERT INTO book_authors VALUES (5, 8);
602 Then use the following command to build a C<myapp.db> SQLite database:
604 $ sqlite3 myapp.db < myapp01.sql
606 If you need to create the database more than once, you probably want to
607 issue the C<rm myapp.db> command to delete the database before you use
608 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
610 Once the C<myapp.db> database file has been created and initialized, you
611 can use the SQLite command line environment to do a quick dump of the
616 Enter ".help" for instructions
617 sqlite> select * from books;
618 1|CCSP SNRS Exam Certification Guide|5
619 2|TCP/IP Illustrated, Volume 1|5
620 3|Internetworking with TCP/IP Vol.1|4
622 5|Designing with Web Standards|5
628 $ sqlite3 myapp.db "select * from books"
629 1|CCSP SNRS Exam Certification Guide|5
630 2|TCP/IP Illustrated, Volume 1|5
631 3|Internetworking with TCP/IP Vol.1|4
633 5|Designing with Web Standards|5
635 As with most other SQL tools, if you are using the full "interactive"
636 environment you need to terminate your SQL commands with a ";" (it's not
637 required if you do a single SQL statement on the command line). Use
638 ".q" to exit from SQLite from the SQLite interactive mode and return to
639 your OS command prompt.
641 For using other databases, such as PostgreSQL or MySQL, see
642 L<Appendix 2|Catalyst::Manual::Tutorial::Appendices>.
645 =head1 DATABASE ACCESS WITH DBIx::Class
647 Catalyst can be used with virtually any form of datastore available via
648 Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be
649 used to access databases through the traditional Perl C<DBI>
650 interface. However, most Catalyst applications use some form of
651 object-relational mapping (ORM) technology to create objects associated
652 with tables in a relational database. Although L<Class::DBI|Class::DBI>
653 has been a popular choice in the past, Matt Trout's
654 L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
655 as the Perl-based ORM technology of choice. Most new Catalyst
656 applications rely on DBIC, as will this tutorial.
659 =head2 Create a Dynamic DBIC Model
661 Use the C<create=dynamic> model helper option to build a model that
662 dynamically reads your database structure every time the application
665 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
666 create=dynamic dbi:SQLite:myapp.db
667 exists "/home/me/MyApp/script/../lib/MyApp/Model"
668 exists "/home/me/MyApp/script/../t"
669 exists "/home/me/MyApp/script/../lib/MyApp"
670 created "/home/me/MyApp/script/../lib/MyApp/Schema.pm"
671 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
672 created "/home/me/MyApp/script/../t/model_DB.t"
675 The C<script/myapp_create.pl> command breaks down like this:
681 C<DB> is the name of the model class to be created by the helper in
686 C<DBIC::Schema> is the type of the model to create.
690 C<MyApp::Schema> is the name of the DBIC schema file written to
691 C<lib/MyApp/Schema.pm>.
695 Because we specified C<create=dynamic> to the helper, it use
696 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
697 dynamically load the schema information from the database every time
698 the application starts.
702 And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
707 B<NOTE:> Although the C<create=dynamic> option to the DBIC helper
708 makes for a nifty demonstration, is only really suitable for very
709 small applications. After this demonstration, you should almost always
710 use the C<create=static> option that we will switch to below.
713 =head1 ENABLE THE MODEL IN THE CONTROLLER
715 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
716 left disabled earlier so that your version matches the following (un-
717 comment the line containing C<[$c-E<gt>model('DB::Books')-E<gt>all]>
718 and delete the next 2 lines):
722 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
727 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
728 # 'Context' that's used to 'glue together' the various components
729 # that make up the application
732 # Retrieve all of the book records as book model objects and store in the
733 # stash where they can be accessed by the TT template
734 $c->stash->{books} = [$c->model('DB::Books')->all];
736 # Set the TT template to use. You will almost always want to do this
737 # in your action methods (action methods respond to user input in
739 $c->stash->{template} = 'books/list.tt2';
742 B<TIP>: You may see the C<$c-E<gt>model('DB::Books')> un-commented
743 above written as C<$c-E<gt>model('DB')-E<gt>resultset('Books')>. The
744 two are equivalent. Either way, C<$c-E<gt>model> returns a
745 L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
746 against the database and iterating over the set of results that is
749 We are using the C<-E<gt>all> to fetch all of the books. DBIC
750 supports a wide variety of more advanced operations to easily do
751 things like filtering and sorting the results. For example, the
752 following could be used to sort the results by descending title:
754 $c->model('DB::Books')->search({}, {order_by => 'title DESC'});
756 Some other examples are provided in
757 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
758 additional information found at L<DBIx::Class::ResultSet/search>,
759 L<DBIx::Class::Manual::FAQ/Searching>,
760 L<DBIx::Class::Manual::Intro|DBIx::Class::Manual::Intro>
761 and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
764 =head2 Test Run The Application
766 First, let's enable an environment variable that causes DBIx::Class to
767 dump the SQL statements used to access the database. This is a
768 helpful trick when you are trying to debug your database-oriented
771 $ export DBIC_TRACE=1
773 This assumes you are using bash as your shell -- adjust accordingly if
774 you are using a different shell (for example, under tcsh, use
775 C<setenv DBIC_TRACE 1>).
777 B<NOTE:> You can also set this in your code using
778 C<$class-E<gt>storage-E<gt>debug(1);>. See
779 L<DBIx::Class::Manual::Troubleshooting> for details (including options
780 to log to a file instead of displaying to the Catalyst development server
783 Then launch the Catalyst development server. The log output should
784 display something like:
786 $ script/myapp_server.pl
787 [debug] Debug messages enabled
788 [debug] Statistics enabled
789 [debug] Loaded plugins:
790 .----------------------------------------------------------------------------.
791 | Catalyst::Plugin::ConfigLoader 0.20 |
792 | Catalyst::Plugin::StackTrace 0.08 |
793 | Catalyst::Plugin::Static::Simple 0.20 |
794 '----------------------------------------------------------------------------'
796 [debug] Loaded dispatcher "Catalyst::Dispatcher"
797 [debug] Loaded engine "Catalyst::Engine::HTTP"
798 [debug] Found home "/home/me/MyApp"
799 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
800 [debug] Loaded components:
801 .-----------------------------------------------------------------+----------.
803 +-----------------------------------------------------------------+----------+
804 | MyApp::Controller::Books | instance |
805 | MyApp::Controller::Root | instance |
806 | MyApp::Model::DB | instance |
807 | MyApp::Model::DB::Authors | class |
808 | MyApp::Model::DB::BookAuthors | class |
809 | MyApp::Model::DB::Books | class |
810 | MyApp::View::TT | instance |
811 '-----------------------------------------------------------------+----------'
813 [debug] Loaded Private actions:
814 .----------------------+--------------------------------------+--------------.
815 | Private | Class | Method |
816 +----------------------+--------------------------------------+--------------+
817 | /default | MyApp::Controller::Root | default |
818 | /end | MyApp::Controller::Root | end |
819 | /index | MyApp::Controller::Root | index |
820 | /books/index | MyApp::Controller::Books | index |
821 | /books/list | MyApp::Controller::Books | list |
822 '----------------------+--------------------------------------+--------------'
824 [debug] Loaded Path actions:
825 .-------------------------------------+--------------------------------------.
827 +-------------------------------------+--------------------------------------+
830 | /books | /books/index |
831 | /books/list | /books/list |
832 '-------------------------------------+--------------------------------------'
834 [info] MyApp powered by Catalyst 5.71000
835 You can connect to your server at http://debian:3000
837 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
838 the 'base' directory of your application, not inside the C<script>
839 directory itself or it will not be able to locate the C<myapp.db>
840 database file. You can use a fully qualified or a relative path to
841 locate the database file, but we did not specify that when we ran the
842 model helper earlier.
844 Some things you should note in the output above:
850 Catalyst::Model::DBIC::Schema dynamically created three model classes,
851 one to represent each of the three tables in our database
852 (C<MyApp::Model::DB::Authors>, C<MyApp::Model::DB::BookAuthors>,
853 and C<MyApp::Model::DB::Books>).
857 The "list" action in our Books controller showed up with a path of
862 Point your browser to L<http://localhost:3000> and you should still get
863 the Catalyst welcome page.
865 Next, to view the book list, change the URL in your browser to
866 L<http://localhost:3000/books/list>. You should get a list of the five
867 books loaded by the C<myapp01.sql> script above without any formatting.
868 The rating for each book should appear on each row, but the "Author(s)"
869 column will still be blank (we will fill that in later).
871 Also notice in the output of the C<script/myapp_server.pl> that DBIC
872 used the following SQL to retrieve the data:
874 SELECT me.id, me.title, me.rating FROM books me
876 because we enabled DBIC_TRACE.
878 You now have the beginnings of a simple but workable web application.
879 Continue on to future sections and we will develop the application
883 =head1 CREATE A WRAPPER FOR THE VIEW
885 When using TT, you can (and should) create a wrapper that will
886 literally wrap content around each of your templates. This is
887 certainly useful as you have one main source for changing things that
888 will appear across your entire site/application instead of having to
889 edit many individual files.
892 =head2 Configure TT.pm For The Wrapper
894 In order to create a wrapper, you must first edit your TT view and
895 tell it where to find your wrapper file. Your TT view is located in
896 C<lib/MyApp/View/TT.pm>.
898 Edit C<lib/MyApp/View/TT.pm> and change it to match the following:
901 # Change default TT extension
902 TEMPLATE_EXTENSION => '.tt2',
903 # Set the location for TT files
905 MyApp->path_to( 'root', 'src' ),
907 # Set to 1 for detailed timer stats in your HTML as comments
909 # This is your wrapper template located in the 'root/src'
910 WRAPPER => 'wrapper.tt2',
914 =head2 Create the Wrapper Template File and Stylesheet
916 Next you need to set up your wrapper template. Basically, you'll want
917 to take the overall layout of your site and put it into this file.
918 For the tutorial, open C<root/src/wrapper.tt2> and input the following:
920 <?xml version="1.0" encoding="UTF-8"?>
921 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
922 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
924 <title>[% template.title or "My Catalyst App!" %]</title>
925 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
931 [%# Your logo could go here -%]
932 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
933 [%# Insert the page title -%]
934 <h1>[% template.title or site.title %]</h1>
941 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
942 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
944 </div><!-- end menu -->
947 [%# Status and error messages %]
948 <span class="message">[% status_msg %]</span>
949 <span class="error">[% error_msg %]</span>
950 [%# This is where TT will stick all of your template's contents. -%]
952 </div><!-- end content -->
953 </div><!-- end bodyblock -->
955 <div id="footer">Copyright (c) your name goes here</div>
956 </div><!-- end outer -->
961 Notice the status and error message sections in the code above:
963 <span class="status">[% status_msg %]</span>
964 <span class="error">[% error_msg %]</span>
966 If we set either message in the Catalyst stash (e.g.,
967 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
968 will be displayed whenever any view used by that request is rendered.
969 The C<message> and C<error> CSS styles can be customized to suit your
970 needs in the C<root/static/css/main.css> file we create below.
978 The Catalyst stash only lasts for a single HTTP request. If
979 you need to retain information across requests you can use
980 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
981 Catalyst sessions in the Authentication chapter of the tutorial).
985 Although it is beyond the scope of this tutorial, you may wish to use
986 a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
987 Dojo (L<http://www.dojotoolkit.org>).
992 =head3 Create A Basic Stylesheet
994 First create a central location for stylesheets under the static
997 $ mkdir root/static/css
999 Then open the file C<root/static/css/main.css> (the file referenced in
1000 the stylesheet href link of our wrapper above) and add the following
1019 background-color: #ddd;
1025 padding: 0 0 50% 5px;
1026 font-weight: normal;
1027 background-color: #ddd;
1040 You may wish to check out a "CSS Framework" like Emastic
1041 (L<http://code.google.com/p/emastic/>) as a way to quickly
1042 provide lots of high-quality CSS functionality.
1045 =head2 Test Run The Application
1047 Restart the development server and hit "Reload" in your web browser
1048 and you should now see a formatted version of our basic book list.
1049 Although our wrapper and stylesheet are obviously very simple, you
1050 should see how it allows us to control the overall look of an entire
1051 website from two central files. To add new pages to the site, just
1052 provide a template that fills in the C<content> section of our wrapper
1053 template -- the wrapper will provide the overall feel of the page.
1056 =head1 A STATIC DATABASE MODEL WITH DBIx::Class
1058 First, let's be sure we have a recent version of the DBIC helper,
1059 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
1060 running this command:
1062 $ perl -MCatalyst::Model::DBIC::Schema -e \
1063 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
1066 If you don't have version 0.23 or higher, please run this command
1067 to install it directly from CPAN:
1069 $ sudo cpan Catalyst::Model::DBIC::Schema
1071 And re-run the version print command to verify that you are now at
1075 =head2 Create Static DBIC Schema Files
1077 Unlike the previous DBIC section where we had C<create=dynamic>
1078 automatically discover the structure of the database every time the
1079 application started, here we will use static schema files for more
1080 control. This is typical of most "real world" applications.
1082 One option would be to manually create a separate schema file for each
1083 table in the database. However, let's use the same
1084 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> we used
1085 earlier with C<create=dynamic> to build the static files for us.
1086 First, let's remove the schema file created earlier:
1088 $ rm lib/MyApp/Schema.pm
1090 Now regenerate the schema using the C<create=static> option:
1092 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
1093 create=static components=TimeStamp dbi:SQLite:myapp.db
1094 exists "/home/me/MyApp/script/../lib/MyApp/Model"
1095 exists "/home/me/MyApp/script/../t"
1096 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
1097 Schema dump completed.
1098 exists "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
1100 We could have also deleted C<lib/MyApp/Model/DB.pm>, but it would
1101 have regenerated the same file (note the C<exists> in the output above).
1102 If you take a look at C<lib/MyApp/Model/DB.pm>, it simply contains
1103 a reference to the actual schema file in C<lib/MyApp/Schema.pm>
1104 along with the database connect string.
1106 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
1108 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> as its base
1109 class (L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> is
1110 only being used by the helper to load the schema once and then create
1111 the static files for us) and C<Schema.pm> only contains a call to the
1112 C<load_namespaces> method. You will also find that C<lib/MyApp>
1113 contains a C<Schema> subdirectory, which then has a subdirectory
1114 called "Result". This "Result" subdirectory then has files named
1115 according to each of the tables in our simple database (C<Authors.pm>,
1116 C<BookAuthors.pm>, and C<Books.pm>). These three files are called
1117 "Result Classes" in DBIC nomenclature. Although the Result Class files
1118 are named after tables in our database, the classes correspond to the
1119 I<row-level data> that is returned by DBIC (more on this later,
1121 L<Catalyst::Manual::Tutorial::BasicCRUD/EXPLORING THE POWER OF DBIC>).
1123 The idea with the Result Source files created under
1124 C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
1125 edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
1126 warning. If you place all of your changes below that point in the
1127 file, you can regenerate the automatically created information at the
1128 top of each file should your database structure get updated.
1130 Also note the "flow" of the model information across the various files
1131 and directories. Catalyst will initially load the model from
1132 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
1133 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the
1134 call to C<load_namespaces> in C<Schema.pm> will load each of the
1135 "Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
1136 The final outcome is that Catalyst will dynamically create three
1137 table-specific Catalyst models every time the application starts (you
1138 can see these three model files listed in the debug output generated
1139 when you launch the application).
1141 B<NOTE:> Older versions of
1142 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
1143 deprecated DBIC C<load_classes> technique instead of the newer
1144 C<load_namspaces>. For new applications, please try to use
1145 C<load_namespaces> since it more easily supports a very useful DBIC
1146 technique called "ResultSet Classes." If you need to convert an
1147 existing application from "load_classes" to "load_namespaces," you can
1148 use this process to automate the migration (but first make sure you
1149 have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
1151 $ # First delete the existing schema file to disable "compatibility" mode
1152 $ rm lib/MyApp/Schema.pm
1154 $ # Then re-run the helper to build the files for "load_namespaces"
1155 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
1156 create=static components=TimeStamp dbi:SQLite:myapp.db
1158 $ # Now convert the existing files over
1159 $ cd lib/MyApp/Schema
1160 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
1161 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
1162 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
1165 $ # And finally delete the old files
1166 $ rm lib/MyApp/Schema/*.pm
1168 The "C<perl -MIO::ALL ...>" script will copy all the customized
1169 relationship (and other) information below "C<# DO NOT MODIFY>" line
1170 from the old files in C<lib/MyApp/Schema> to the new files in
1171 C<lib/MyApp/Schema/Result> (we will be starting to add some
1172 "customized relationship information in the section below).
1175 =head2 Updating the Generated DBIC Result Class Files
1177 Let's manually add some relationship information to the auto-generated
1178 Result Class files. (Note: if you are using a database other than
1179 SQLite, such as PostgreSQL, then the relationship could have been
1180 automatically placed in the Result Class files. If so, you can skip
1181 this step.) First edit C<lib/MyApp/Schema/Result/Books.pm> and add the
1182 following text below the C<# You can replace this text...> comment:
1185 # Set relationships:
1190 # 1) Name of relationship, DBIC will create accessor with this name
1191 # 2) Name of the model class referenced by this relationship
1192 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1193 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthors', 'book_id');
1197 # 1) Name of relationship, DBIC will create accessor with this name
1198 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1199 # 3) Name of belongs_to() relationship in model class of has_many() above
1200 # You must already have the has_many() defined to use a many_to_many().
1201 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1204 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1205 file. As with any Perl package, we need to end the last line with
1206 a statement that evaluates to C<true>. This is customarily done with
1207 C<1;> on a line by itself.
1209 C<Important Note:> Although this tutorial uses plural names for both
1210 the names of the SQL tables and therefore the Result Classes (after
1211 all, C<Schema::Loader> automatically named the Result Classes from the
1212 names of the SQL tables it found), DBIC users prefer singular names
1213 for these items. B<Please try to use singular table and DBIC
1214 model/Result Class names in your applications.> This tutorial will
1215 migrate to singular names as soon as possible (patches welcomed).
1216 B<Note that while singular is preferred for the DBIC model, plural is
1217 perfectly acceptable for the names of the controller classes.> After
1218 all, the C<Books.pm> controller operates on multiple books.
1220 This code defines both a C<has_many> and a C<many_to_many> relationship.
1221 The C<many_to_many> relationship is optional, but it makes it easier to
1222 map a book to its collection of authors. Without it, we would have to
1223 "walk" though the C<book_authors> table as in
1224 C<$book-E<gt>book_authors-E<gt>first-E<gt>author-E<gt>last_name>
1225 (we will see examples on how to use DBIC objects in your code soon,
1226 but note that because C<$book-E<gt>book_authors> can return multiple
1227 authors, we have to use C<first> to display a single author).
1228 C<many_to_many> allows us to use the shorter
1229 C<$book-E<gt>authors-E<gt>first-E<gt>last_name>.
1230 Note that you cannot define a C<many_to_many> relationship without
1231 also having the C<has_many> relationship in place.
1233 Then edit C<lib/MyApp/Schema/Result/Authors.pm> and add relationship
1234 information as follows (again, be careful to put in above the C<1;> but
1235 below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1238 # Set relationships:
1243 # 1) Name of relationship, DBIC will create an accessor with this name
1244 # 2) Name of the model class referenced by this relationship
1245 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1246 __PACKAGE__->has_many(book_author => 'MyApp::Schema::Result::BookAuthors', 'author_id');
1250 # 1) Name of relationship, DBIC will create accessor with this name
1251 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1252 # 3) Name of belongs_to() relationship in model class of has_many() above
1253 # You must already have the has_many() defined to use a many_to_many().
1254 __PACKAGE__->many_to_many(books => 'book_author', 'book');
1256 Finally, do the same for the "join table,"
1257 C<lib/MyApp/Schema/Result/BookAuthors.pm>:
1260 # Set relationships:
1265 # 1) Name of relationship, DBIC will create accessor with this name
1266 # 2) Name of the model class referenced by this relationship
1267 # 3) Column name in *this* table
1268 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Books', 'book_id');
1272 # 1) Name of relationship, DBIC will create accessor with this name
1273 # 2) Name of the model class referenced by this relationship
1274 # 3) Column name in *this* table
1275 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Authors', 'author_id');
1278 =head2 Run The Application
1280 Run the Catalyst development server script with the C<DBIC_TRACE> option
1281 (it might still be enabled from earlier in the tutorial, but here is an
1282 alternate way to specify the option just in case):
1284 $ DBIC_TRACE=1 script/myapp_server.pl
1286 Make sure that the application loads correctly and that you see the
1287 three dynamically created model class (one for each of the
1288 Result Classes we created).
1290 Then hit the URL L<http://localhost:3000/books/list> with your browser
1291 and be sure that the book list is displayed via the relationships
1292 established above. You can leave the development server running for
1293 the next step if you wish.
1295 B<Note:> You will not see the authors yet because the view does not yet
1296 use the new relations. Read on to the next section where we update the
1297 template to do that.
1300 =head1 UPDATING THE VIEW
1302 Let's add a new column to our book list page that takes advantage of
1303 the relationship information we manually added to our schema files in
1304 the previous section. Edit C<root/src/books/list.tt2> and add the
1305 following code below the existing table cell that contains
1306 C<book.rating> (IOW, add a new table cell below the existing two
1307 C<E<lt>tdE<gt>> tags but above the closing C<E<lt>/trE<gt>> and
1308 C<E<lt>/tableE<gt>> tags):
1312 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1313 [% # loop in 'side effect notation' to load just the last names of the -%]
1314 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1315 [% # a value, so nothing will be printed here. But, if you have something -%]
1316 [% # in TT that does return a method and you don't want it printed, you -%]
1317 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1318 [% # call it and discard the return value. -%]
1319 [% tt_authors = [ ];
1320 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1321 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1322 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1323 ([% tt_authors.size | html %])
1324 [% # Use another TT vmethod to join & print the names & comma separators -%]
1325 [% tt_authors.join(', ') | html %]
1329 Then hit "Reload" in your browser (note that you don't need to reload
1330 the development server or use the C<-r> option when updating TT
1331 templates) and you should now see the number of authors each book has
1332 along with a comma-separated list of the authors' last names. (If you
1333 didn't leave the development server running from the previous step,
1334 you will obviously need to start it before you can refresh your
1337 If you are still running the development server with C<DBIC_TRACE>
1338 enabled, you should also now see five more C<SELECT> statements in the
1339 debug output (one for each book as the authors are being retrieved by
1342 SELECT me.id, me.title, me.rating FROM books me:
1343 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1344 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '1'
1345 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1346 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '2'
1347 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1348 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '3'
1349 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1350 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '4'
1351 SELECT author.id, author.first_name, author.last_name FROM book_authors me
1352 JOIN authors author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '5'
1354 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1355 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1356 and > and avoid various types of dangerous hacks against your
1357 application. In a real application, you would probably want to put
1358 "| html" at the end of every field where a user has control over the
1359 information that can appear in that field (and can therefore inject
1360 markup or code if you don't "neutralize" those fields). In addition to
1361 "| html", Template Toolkit has a variety of other useful filters that
1362 can found in the documentation for
1363 L<Template::Filters|Template::Filters>.
1366 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1368 In some situations, it can be useful to run your application and
1369 display a page without using a browser. Catalyst lets you do this
1370 using the C<scripts/myapp_test.pl> script. Just supply the URL you
1371 wish to display and it will run that request through the normal
1372 controller dispatch logic and use the appropriate view to render the
1373 output (obviously, complex pages may dump a lot of text to your
1374 terminal window). For example, if you type:
1376 $ script/myapp_test.pl "/books/list"
1378 You should get the same text as if you visited
1379 L<http://localhost:3000/books/list> with the normal development server
1380 and asked your browser to view the page source.
1383 =head1 OPTIONAL INFORMATION
1385 B<NOTE: The rest of this chapter of the tutorial is optional. You can
1386 skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
1390 =head2 Using 'RenderView' for the Default View
1392 Once your controller logic has processed the request from a user, it
1393 forwards processing to your view in order to generate the appropriate
1394 response output. Catalyst uses
1395 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1396 default to automatically perform this operation. If you look in
1397 C<lib/MyApp/Controller/Root.pm>, you should see the empty
1398 definition for the C<sub end> method:
1400 sub end : ActionClass('RenderView') {}
1402 The following bullet points provide a quick overview of the
1403 C<RenderView> process:
1409 C<Root.pm> is designed to hold application-wide logic.
1413 At the end of a given user request, Catalyst will call the most specific
1414 C<end> method that's appropriate. For example, if the controller for a
1415 request has an C<end> method defined, it will be called. However, if
1416 the controller does not define a controller-specific C<end> method, the
1417 "global" C<end> method in C<Root.pm> will be called.
1421 Because the definition includes an C<ActionClass> attribute, the
1422 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1423 will be executed B<after> any code inside the definition of C<sub end>
1424 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1425 for more information on C<ActionClass>.
1429 Because C<sub end> is empty, this effectively just runs the default
1430 logic in C<RenderView>. However, you can easily extend the
1431 C<RenderView> logic by adding your own code inside the empty method body
1432 (C<{}>) created by the Catalyst Helpers when we first ran the
1433 C<catalyst.pl> to initialize our application. See
1434 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1435 detailed information on how to extend C<RenderView> in C<sub end>.
1440 =head2 Using The Default Template Name
1442 By default, C<Catalyst::View::TT> will look for a template that uses the
1443 same name as your controller action, allowing you to save the step of
1444 manually specifying the template name in each action. For example, this
1445 would allow us to remove the
1446 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1447 C<list> action in the Books controller. Open
1448 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1449 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1454 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1459 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1460 # 'Context' that's used to 'glue together' the various components
1461 # that make up the application
1462 my ($self, $c) = @_;
1464 # Retrieve all of the book records as book model objects and store in the
1465 # stash where they can be accessed by the TT template
1466 $c->stash->{books} = [$c->model('DB::Books')->all];
1468 # Set the TT template to use. You will almost always want to do this
1469 # in your action methods (actions methods respond to user input in
1470 # your controllers).
1471 #$c->stash->{template} = 'books/list.tt2';
1475 You should now be able to restart the development server as per the
1476 previous section and access the L<http://localhost:3000/books/list>
1479 B<NOTE:> Please note that if you use the default template technique,
1480 you will B<not> be able to use either the C<$c-E<gt>forward> or
1481 the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1482 Chapter 9 of the Tutorial).
1485 =head2 Return To A Manually Specified Template
1487 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1488 later in the tutorial, you should remove the comment from the
1489 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1491 $c->stash->{template} = 'books/list.tt2';
1493 Then delete the C<TEMPLATE_EXTENSION> line in
1494 C<lib/MyApp/View/TT.pm>.
1496 You should then be able to restart the development server and
1497 access L<http://localhost:3000/books/list> in the same manner as
1498 with earlier sections.
1503 Kennedy Clark, C<hkclark@gmail.com>
1505 Please report any errors, issues or suggestions to the author. The
1506 most recent version of the Catalyst Tutorial can be found at
1507 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
1509 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1510 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).