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.
216 Make sure that when adding new plugins that you include them as a new
217 dependancies within the Makefile.PL file. For example, after adding
218 the StackTrace plugin the Makefile.PL should include the following
221 requires 'Catalyst::Plugin::StackTrace';
230 C<__PACKAGE__> is just a shorthand way of referencing the name of the
231 package where it is used. Therefore, in C<MyApp.pm>, C<__PACKAGE__>
232 is equivalent to C<MyApp>.
236 You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
237 before you put your application into production, but it can be helpful
242 When specifying plugins on the C<__PACKAGE__-E<gt>setup> line, you can
243 omit C<Catalyst::Plugin::> from the name. Additionally, you can
244 spread the plugin names across multiple lines as shown here, or place
245 them all on one (or more) lines as with the default configuration.
250 =head1 CREATE A CATALYST CONTROLLER
252 As discussed earlier, controllers are where you write methods that
253 interact with user input. Typically, controller methods respond to
254 C<GET> and C<POST> requests from the user's web browser.
256 Use the Catalyst C<create> script to add a controller for book-related
259 $ script/myapp_create.pl controller Books
260 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
261 exists "/home/me/MyApp/script/../t"
262 created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm"
263 created "/home/me/MyApp/script/../t/controller_Books.t"
265 Then edit C<lib/MyApp/Controller/Books.pm> (as discussed in Chapter 2 of
266 the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
267 each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
268 and add the following method to the controller:
272 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
277 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
278 # 'Context' that's used to 'glue together' the various components
279 # that make up the application
282 # Retrieve all of the book records as book model objects and store in the
283 # stash where they can be accessed by the TT template
284 # $c->stash->{books} = [$c->model('DB::Book')->all];
285 # But, for now, use this code until we create the model later
286 $c->stash->{books} = '';
288 # Set the TT template to use. You will almost always want to do this
289 # in your action methods (action methods respond to user input in
291 $c->stash->{template} = 'books/list.tt2';
294 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
295 cutting and pasting example code from POD-based documents.
297 Programmers experienced with object-oriented Perl should recognize
298 C<$self> as a reference to the object where this method was called.
299 On the other hand, C<$c> will be new to many Perl programmers who have
300 not used Catalyst before (it's sometimes written as C<$context>). The
301 Context object is automatically passed to all Catalyst components. It
302 is used to pass information between components and provide access to
303 Catalyst and plugin functionality.
305 Catalyst actions are regular Perl methods, but they make use of
306 attributes (the "C<: Local>" next to the "C<sub list>" in the code
307 above) to provide additional information to the Catalyst dispatcher
308 logic (note that the space between the colon and the attribute name is
309 optional; you will see attributes written both ways). Most Catalyst
310 Controllers use one of five action types:
316 B<:Private> -- Use C<:Private> for methods that you want to make into
317 an action, but you do not want Catalyst to directly expose
318 to your users. Catalyst will not map C<:Private> methods to a URI.
319 Use them for various sorts of "special" methods (the C<begin>,
320 C<auto>, etc. discussed below) or for methods you want to be able to
321 C<forward> or C<detach> to. (If the method is a plain old "helper
322 method" that you don't want to be an action at all, then just define
323 the method without any attribute -- you can call it in your code, but
324 the Catalyst dispatcher will ignore it.)
326 There are five types of "special" build-in C<:Private> actions:
327 C<begin>, C<end>, C<default>, C<index>, and C<auto>.
333 With C<begin>, C<end>, C<default>, C<index> private actions, only the
334 most specific action of each type will be called. For example, if you
335 define a C<begin> action in your controller it will I<override> a
336 C<begin> action in your application/root controller -- I<only> the
337 action in your controller will be called.
341 Unlike the other actions where only a single method is called for each
342 request, I<every> auto action along the chain of namespaces will be
343 called. Each C<auto> action will be called I<from the application/root
344 controller down through the most specific class>.
350 B<:Path> -- C<:Path> actions let you map a method to an explicit URI
351 path. For example, "C<:Path('list')>" in
352 C<lib/MyApp/Controller/Books.pm> would match on the URL
353 C<http://localhost:3000/books/list> but "C<:Path('/list')>" would match
354 on C<http://localhost:3000/list>. You can use C<:Args()> to specify
355 how many arguments an action should accept. See
356 L<Catalyst::Manual::Intro/Action_types> for more information and a few
361 B<:Local> -- C<:Local> is merely a shorthand for
362 "C<:Path('_name_of_method_')>". For example, these are equivalent:
363 "C<sub create_book :Local {...}>" and
364 "C<sub create_book :Path('create_book') {...}>".
368 B<:Global> -- C<:Global> is merely a shorthand for
369 "C<:Path('/_name_of_method_')>". For example, these are equivalent:
370 "C<sub create_book :Global {...}>" and
371 "C<sub create_book :Path('/create_book') {...}>".
375 B<:Chained> -- Newer Catalyst applications tend to use the Chained
376 dispatch form of action types because of its power and flexibility.
377 It allows a series of controller methods to be automatically dispatched
378 to service a single user request. See
379 L<Catalyst::Manual::Tutorial::BasicCRUD|Catalyst::Manual::Tutorial::BasicCRUD>
380 and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
381 for more information on chained actions.
385 You should refer to L<Catalyst::Manual::Intro/Action_types> for
386 additional information and for coverage of some lesser-used action
387 types not discussed here (C<Regex> and C<LocalRegex>).
390 =head1 CATALYST VIEWS
392 As mentioned in Chapter 2 of the tutorial, views are where you render
393 output, typically for display in the user's web browser (but also
394 possibly using into output-generation systems, such as PDF or JSON).
395 The code in C<lib/MyApp/View> selects the I<type> of view to use, with
396 the actual rendering template found in the C<root> directory. As with
397 virtually every aspect of Catalyst, options abound when it comes to the
398 specific view technology you adopt inside your application. However,
399 most Catalyst applications use the Template Toolkit, known as TT (for
400 more information on TT, see L<http://www.template-toolkit.org>). Other
401 somewhat popular view technologies include Mason
402 (L<http://www.masonhq.com> and L<http://www.masonbook.com>) and
403 L<HTML::Template> (L<http://html-template.sourceforge.net>).
406 =head2 Create a Catalyst View
408 When using TT for the Catalyst view, there are two main helper scripts:
414 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
418 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
422 Both helpers are similar. C<TT> creates the C<lib/MyApp/View/TT.pm>
423 file and leaves the creation of any hierarchical template organization
424 entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
425 test cases will be discussed in Chapter 8.) C<TTSite>, on the other hand,
426 creates a modular and hierarchical view layout with
427 separate Template Toolkit (TT) files for common header and footer
428 information, configuration values, a CSS stylesheet, and more.
430 While C<TTSite> was useful to bootstrap a project, its use is now
431 deprecated and it should be considered historical. For most Catalyst
432 applications it adds redundant functionality and structure; many in the
433 Catalyst community recommend that it's easier to learn both Catalyst and
434 Template Toolkit if you use the more basic C<TT> approach.
435 Consequently, this tutorial will use "plain old TT."
437 Enter the following command to enable the C<TT> style of view
438 rendering for this tutorial:
440 $ script/myapp_create.pl view TT TT
441 exists "/home/me/MyApp/script/../lib/MyApp/View"
442 exists "/home/me/MyApp/script/../t"
443 created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm"
444 created "/home/me/MyApp/script/../t/view_TT.t"
446 This simply creates a view called C<TT> (the second 'TT' argument) in
447 a file called C<TT.pm> (the first 'TT' argument). It is now up to you
448 to decide how you want to structure your view layout. For the
449 tutorial, we will start with a very simple TT template to initially
450 demonstrate the concepts, but quickly migrate to a more typical
451 "wrapper page" type of configuration (where the "wrapper" controls the
452 overall "look and feel" of your site from a single file or set of
455 Edit C<lib/MyApp/View/TT.pm> and you should see that the default
456 contents contains something similar to the following:
458 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
460 And update it to match:
463 # Change default TT extension
464 TEMPLATE_EXTENSION => '.tt2',
465 # Set the location for TT files
467 MyApp->path_to( 'root', 'src' ),
471 B<NOTE:> Make sure to add a comma after '.tt2' outside the single
474 This changes the default extension for Template Toolkit from '.tt' to
475 '.tt2' and changes the base directory for your template files from
476 C<root> to C<root/src>. These changes from the default are done mostly
477 to facilitate the application we're developing in this tutorial; as with
478 most things Perl, there's more than one way to do it...
480 B<Note:> We will use C<root/src> as the base directory for our
481 template files, which a full naming convention of
482 C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
483 use C<root/> as the base (with a full filename pattern of
484 C<root/_controller_name_/_action_name_.tt2>).
487 =head2 Create a TT Template Page
489 First create a directory for book-related TT templates:
491 $ mkdir -p root/src/books
493 Then create C<root/src/books/list.tt2> in your editor and enter:
495 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
496 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
497 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
498 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
500 [% # Provide a title -%]
501 [% META title = 'Book List' -%]
504 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
505 [% # Display each book in a table row %]
506 [% FOREACH book IN books -%]
508 <td>[% book.title %]</td>
509 <td>[% book.rating %]</td>
515 As indicated by the inline comments above, the C<META title> line uses
516 TT's META feature to provide a title to the "wrapper" that we will
517 create later. Meanwhile, the C<FOREACH> loop iterates through each
518 C<book> model object and prints the C<title> and C<rating> fields.
520 The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
521 supports a wide variety of directives for "calling" other files,
522 looping, conditional logic, etc. In general, TT simplifies the usual
523 range of Perl operators down to the single dot (C<.>) operator. This
524 applies to operations as diverse as method calls, hash lookups, and list
526 L<http://search.cpan.org/perldoc?Template::Manual::Variables> for
527 details and examples). In addition to the usual C<Template> module Pod
528 documentation, you can access the TT manual at
529 L<http://search.cpan.org/perldoc?Template::Manual>.
531 B<TIP:> While you can build all sorts of complex logic into your TT
532 templates, you should in general keep the "code" part of your templates
533 as simple as possible. If you need more complex logic, create helper
534 methods in your model that abstract out a set of code into a single call
535 from your TT template. (Note that the same is true of your controller
536 logic as well -- complex sections of code in your controllers should
537 often be pulled out and placed into your model objects.)
540 =head2 Test Run The Application
542 To test your work so far, first start the development server:
544 $ script/myapp_server.pl
546 Then point your browser to L<http://localhost:3000> and you should
547 still get the Catalyst welcome page. Next, change the URL in your
548 browser to L<http://localhost:3000/books/list>. If you have
549 everything working so far, you should see a web page that displays
550 nothing other than our column headers for "Title", "Rating", and
551 "Author(s)" -- we will not see any books until we get the database and
554 If you run into problems getting your application to run correctly, it
555 might be helpful to refer to some of the debugging techniques covered in
556 the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the
560 =head1 CREATE A SQLITE DATABASE
562 In this step, we make a text file with the required SQL commands to
563 create a database table and load some sample data. We will use SQLite,
564 a popular database that is lightweight and easy to use. Open
565 C<myapp01.sql> in your editor and enter:
568 -- Create a very simple database to hold book and author information
571 id INTEGER PRIMARY KEY,
575 -- 'book_author' is a many-to-many join table between books & authors
576 CREATE TABLE book_author (
579 PRIMARY KEY (book_id, author_id)
581 CREATE TABLE author (
582 id INTEGER PRIMARY KEY,
587 --- Load some sample data
589 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
590 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
591 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
592 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
593 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
594 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
595 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
596 INSERT INTO author VALUES (3, 'Christian', 'Degu');
597 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
598 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
599 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
600 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
601 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
602 INSERT INTO book_author VALUES (1, 1);
603 INSERT INTO book_author VALUES (1, 2);
604 INSERT INTO book_author VALUES (1, 3);
605 INSERT INTO book_author VALUES (2, 4);
606 INSERT INTO book_author VALUES (3, 5);
607 INSERT INTO book_author VALUES (4, 6);
608 INSERT INTO book_author VALUES (4, 7);
609 INSERT INTO book_author VALUES (5, 8);
611 Then use the following command to build a C<myapp.db> SQLite database:
613 $ sqlite3 myapp.db < myapp01.sql
615 If you need to create the database more than once, you probably want to
616 issue the C<rm myapp.db> command to delete the database before you use
617 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
619 Once the C<myapp.db> database file has been created and initialized, you
620 can use the SQLite command line environment to do a quick dump of the
625 Enter ".help" for instructions
626 sqlite> select * from book;
627 1|CCSP SNRS Exam Certification Guide|5
628 2|TCP/IP Illustrated, Volume 1|5
629 3|Internetworking with TCP/IP Vol.1|4
631 5|Designing with Web Standards|5
637 $ sqlite3 myapp.db "select * from book"
638 1|CCSP SNRS Exam Certification Guide|5
639 2|TCP/IP Illustrated, Volume 1|5
640 3|Internetworking with TCP/IP Vol.1|4
642 5|Designing with Web Standards|5
644 As with most other SQL tools, if you are using the full "interactive"
645 environment you need to terminate your SQL commands with a ";" (it's not
646 required if you do a single SQL statement on the command line). Use
647 ".q" to exit from SQLite from the SQLite interactive mode and return to
648 your OS command prompt.
650 Please note that here we have chosen to use 'singular' table names. This
651 is because the default inflection code for L<DBIx::Class:Schema::Loader>
652 does NOT handle plurals. There has been much philosophical discussion
653 on whether table names should be plural or singular. There is no one
654 correct answer, as long as one makes a choice and remains consistent
655 with it. If you prefer plural table names (e.g. they are easier and
656 more natural to read) then you will need to pass it an inflect_map
657 option. See L<DBIx::Class:Schema::Loader> for more information.
659 For using other databases, such as PostgreSQL or MySQL, see
660 L<Appendix 2|Catalyst::Manual::Tutorial::Appendices>.
663 =head1 DATABASE ACCESS WITH DBIx::Class
665 Catalyst can be used with virtually any form of datastore available
666 via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
667 can be used to access databases through the traditional Perl C<DBI>
668 interface or you can use a model to access files of any type on the
669 filesystem. However, most Catalyst applications use some form of
670 object-relational mapping (ORM) technology to create objects
671 associated with tables in a relational database. Matt Trout's
672 L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
673 as the Perl-based ORM technology of choice. Most new Catalyst
674 applications rely on DBIx::Class, as will this tutorial.
676 Although DBIx::Class has included support for a C<create=dynamic> mode
677 to automatically read the database structure every time the
678 application starts, it's use is no longer recommended. While it can
679 make for "flashy" demos, the use of the C<create=static> mode we use
680 below can be implemented just as quickly and provides many advantages
681 (such as the ability to add your own methods to the overall DBIC
682 framework, a technique that we see in Chapter 4).
685 =head2 Make Sure You Have a Recent Version of the DBIx::Class Model
687 First, let's be sure we have a recent version of the DBIC helper,
688 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
689 running this command:
691 $ perl -MCatalyst::Model::DBIC::Schema -e \
692 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
695 (please note that the '\' above is a line continuation marker and
696 should NOT be included as part of the command)
698 If you don't have version 0.23 or higher, please run this command
699 to install it directly from CPAN:
701 $ sudo cpan Catalyst::Model::DBIC::Schema
703 And re-run the version print command to verify that you are now at
707 =head2 Create Static DBIx::Class Schema Files
709 Before you continue, make sure your C<myapp.db> database file is in
710 the application's topmost directory. Now use the model helper with
711 the C<create=static> option to read the database with
712 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
713 automatically build the required files for us:
715 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
716 create=static components=TimeStamp dbi:SQLite:myapp.db
717 exists "/home/me/MyApp/script/../lib/MyApp/Model"
718 exists "/home/me/MyApp/script/../t"
719 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
720 Schema dump completed.
721 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
722 created "/home/me/MyApp/script/../t/model_DB.t"
724 (please note that the '\' above is a line continuation marker and
725 should NOT be included as part of the command)
727 The C<script/myapp_create.pl> command breaks down like this:
733 C<DB> is the name of the model class to be created by the helper in
738 C<DBIC::Schema> is the type of the model to create.
742 C<MyApp::Schema> is the name of the DBIC schema file written to
743 C<lib/MyApp/Schema.pm>.
747 C<create=static> causes
748 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
749 load the schema as it runs and then write that information out
754 C<components=TimeStamp> causes the help to include the
755 L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp> DBIC component.
759 And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
764 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
765 only contains a call to the C<load_namespaces> method. You will also
766 find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
767 has a subdirectory called "Result". This "Result" subdirectory then
768 has files named according to each of the tables in our simple database
769 (C<Author.pm>, C<BookAuthor.pm>, and C<Book.pm>). These three
770 files are called "Result Classes" in DBIx::Class nomenclature. Although the
771 Result Class files are named after tables in our database, the classes
772 correspond to the I<row-level data> that is returned by DBIC (more on
773 this later, especially in
774 L<Catalyst::Manual::Tutorial::BasicCRUD/EXPLORING THE POWER OF DBIC>).
776 The idea with the Result Source files created under
777 C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
778 edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
779 warning. If you place all of your changes below that point in the
780 file, you can regenerate the automatically created information at the
781 top of each file should your database structure get updated.
783 Also note the "flow" of the model information across the various files
784 and directories. Catalyst will initially load the model from
785 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
786 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the
787 call to C<load_namespaces> in C<Schema.pm> will load each of the
788 "Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
789 The final outcome is that Catalyst will dynamically create three
790 table-specific Catalyst models every time the application starts (you
791 can see these three model files listed in the debug output generated
792 when you launch the application).
794 B<NOTE:> Older versions of
795 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
796 deprecated DBIx::Class C<load_classes> technique instead of the newer
797 C<load_namspaces>. For new applications, please try to use
798 C<load_namespaces> since it more easily supports a very useful DBIC
799 technique called "ResultSet Classes." If you need to convert an
800 existing application from "load_classes" to "load_namespaces," you can
801 use this process to automate the migration (but first make sure you
802 have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
804 $ # First delete the existing schema file to disable "compatibility" mode
805 $ rm lib/MyApp/Schema.pm
807 $ # Then re-run the helper to build the files for "load_namespaces"
808 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
809 create=static components=TimeStamp dbi:SQLite:myapp.db
811 $ # Note that the '\' above is a line continuation marker and
812 $ # should NOT be included as part of the command
815 $ # Now convert the existing files over
816 $ cd lib/MyApp/Schema
817 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
818 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
819 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
822 $ # And finally delete the old files
823 $ rm lib/MyApp/Schema/*.pm
825 The "C<perl -MIO::ALL ...>" script will copy all the customized
826 relationship (and other) information below "C<# DO NOT MODIFY>" line
827 from the old files in C<lib/MyApp/Schema> to the new files in
828 C<lib/MyApp/Schema/Result> (we will be starting to add some
829 "customized relationship information in the section below).
832 =head1 ENABLE THE MODEL IN THE CONTROLLER
834 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
835 left disabled earlier so that your version matches the following (un-
836 comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
837 and delete the next 2 lines):
841 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
846 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
847 # 'Context' that's used to 'glue together' the various components
848 # that make up the application
851 # Retrieve all of the book records as book model objects and store in the
852 # stash where they can be accessed by the TT template
853 $c->stash->{books} = [$c->model('DB::Book')->all];
855 # Set the TT template to use. You will almost always want to do this
856 # in your action methods (action methods respond to user input in
858 $c->stash->{template} = 'books/list.tt2';
861 B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
862 above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
863 two are equivalent. Either way, C<$c-E<gt>model> returns a
864 L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
865 against the database and iterating over the set of results that is
868 We are using the C<-E<gt>all> to fetch all of the books. DBIC
869 supports a wide variety of more advanced operations to easily do
870 things like filtering and sorting the results. For example, the
871 following could be used to sort the results by descending title:
873 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
875 Some other examples are provided in
876 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
877 additional information found at L<DBIx::Class::ResultSet/search>,
878 L<DBIx::Class::Manual::FAQ/Searching>,
879 L<DBIx::Class::Manual::Intro|DBIx::Class::Manual::Intro>
880 and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
883 =head2 Test Run The Application
885 First, let's enable an environment variable that causes DBIx::Class to
886 dump the SQL statements used to access the database. This is a
887 helpful trick when you are trying to debug your database-oriented
890 $ export DBIC_TRACE=1
892 This assumes you are using bash as your shell -- adjust accordingly if
893 you are using a different shell (for example, under tcsh, use
894 C<setenv DBIC_TRACE 1>).
896 B<NOTE:> You can also set this in your code using
897 C<$class-E<gt>storage-E<gt>debug(1);>. See
898 L<DBIx::Class::Manual::Troubleshooting> for details (including options
899 to log to a file instead of displaying to the Catalyst development server
902 Then launch the Catalyst development server. The log output should
903 display something like:
905 $ script/myapp_server.pl
906 [debug] Debug messages enabled
907 [debug] Statistics enabled
908 [debug] Loaded plugins:
909 .----------------------------------------------------------------------------.
910 | Catalyst::Plugin::ConfigLoader 0.23 |
911 | Catalyst::Plugin::StackTrace 0.10 |
912 | Catalyst::Plugin::Static::Simple 0.21 |
913 '----------------------------------------------------------------------------'
915 [debug] Loaded dispatcher "Catalyst::Dispatcher"
916 [debug] Loaded engine "Catalyst::Engine::HTTP"
917 [debug] Found home "/home/me/MyApp"
918 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
919 [debug] Loaded components:
920 .-----------------------------------------------------------------+----------.
922 +-----------------------------------------------------------------+----------+
923 | MyApp::Controller::Books | instance |
924 | MyApp::Controller::Root | instance |
925 | MyApp::Model::DB | instance |
926 | MyApp::Model::DB::Author | class |
927 | MyApp::Model::DB::Book | class |
928 | MyApp::Model::DB::BookAuthor | class |
929 | MyApp::View::TT | instance |
930 '-----------------------------------------------------------------+----------'
932 [debug] Loaded Private actions:
933 .----------------------+--------------------------------------+--------------.
934 | Private | Class | Method |
935 +----------------------+--------------------------------------+--------------+
936 | /default | MyApp::Controller::Root | default |
937 | /end | MyApp::Controller::Root | end |
938 | /index | MyApp::Controller::Root | index |
939 | /books/index | MyApp::Controller::Books | index |
940 | /books/list | MyApp::Controller::Books | list |
941 '----------------------+--------------------------------------+--------------'
943 [debug] Loaded Path actions:
944 .-------------------------------------+--------------------------------------.
946 +-------------------------------------+--------------------------------------+
949 | /books | /books/index |
950 | /books/list | /books/list |
951 '-------------------------------------+--------------------------------------'
953 [info] MyApp powered by Catalyst 5.80003
954 You can connect to your server at http://debian:3000
956 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
957 the 'base' directory of your application, not inside the C<script>
958 directory itself or it will not be able to locate the C<myapp.db>
959 database file. You can use a fully qualified or a relative path to
960 locate the database file, but we did not specify that when we ran the
961 model helper earlier.
963 Some things you should note in the output above:
969 Catalyst::Model::DBIC::Schema dynamically created three model classes,
970 one to represent each of the three tables in our database
971 (C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
972 and C<MyApp::Model::DB::Book>).
976 The "list" action in our Books controller showed up with a path of
981 Point your browser to L<http://localhost:3000> and you should still get
982 the Catalyst welcome page.
984 Next, to view the book list, change the URL in your browser to
985 L<http://localhost:3000/books/list>. You should get a list of the five
986 books loaded by the C<myapp01.sql> script above without any formatting.
987 The rating for each book should appear on each row, but the "Author(s)"
988 column will still be blank (we will fill that in later).
990 Also notice in the output of the C<script/myapp_server.pl> that
991 DBIx::Class used the following SQL to retrieve the data:
993 SELECT me.id, me.title, me.rating FROM books me
995 because we enabled DBIC_TRACE.
997 You now have the beginnings of a simple but workable web application.
998 Continue on to future sections and we will develop the application
1002 =head1 CREATE A WRAPPER FOR THE VIEW
1004 When using TT, you can (and should) create a wrapper that will
1005 literally wrap content around each of your templates. This is
1006 certainly useful as you have one main source for changing things that
1007 will appear across your entire site/application instead of having to
1008 edit many individual files.
1011 =head2 Configure TT.pm For The Wrapper
1013 In order to create a wrapper, you must first edit your TT view and
1014 tell it where to find your wrapper file. Your TT view is located in
1015 C<lib/MyApp/View/TT.pm>.
1017 Edit C<lib/MyApp/View/TT.pm> and change it to match the following:
1019 __PACKAGE__->config(
1020 # Change default TT extension
1021 TEMPLATE_EXTENSION => '.tt2',
1022 # Set the location for TT files
1024 MyApp->path_to( 'root', 'src' ),
1026 # Set to 1 for detailed timer stats in your HTML as comments
1028 # This is your wrapper template located in the 'root/src'
1029 WRAPPER => 'wrapper.tt2',
1033 =head2 Create the Wrapper Template File and Stylesheet
1035 Next you need to set up your wrapper template. Basically, you'll want
1036 to take the overall layout of your site and put it into this file.
1037 For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1039 <?xml version="1.0" encoding="UTF-8"?>
1040 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1041 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
1043 <title>[% template.title or "My Catalyst App!" %]</title>
1044 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1050 [%# Your logo could go here -%]
1051 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1052 [%# Insert the page title -%]
1053 <h1>[% template.title or site.title %]</h1>
1056 <div id="bodyblock">
1060 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1061 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1063 </div><!-- end menu -->
1066 [%# Status and error messages %]
1067 <span class="message">[% status_msg %]</span>
1068 <span class="error">[% error_msg %]</span>
1069 [%# This is where TT will stick all of your template's contents. -%]
1071 </div><!-- end content -->
1072 </div><!-- end bodyblock -->
1074 <div id="footer">Copyright (c) your name goes here</div>
1075 </div><!-- end outer -->
1080 Notice the status and error message sections in the code above:
1082 <span class="status">[% status_msg %]</span>
1083 <span class="error">[% error_msg %]</span>
1085 If we set either message in the Catalyst stash (e.g.,
1086 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1087 will be displayed whenever any view used by that request is rendered.
1088 The C<message> and C<error> CSS styles can be customized to suit your
1089 needs in the C<root/static/css/main.css> file we create below.
1097 The Catalyst stash only lasts for a single HTTP request. If
1098 you need to retain information across requests you can use
1099 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
1100 Catalyst sessions in the Authentication chapter of the tutorial).
1104 Although it is beyond the scope of this tutorial, you may wish to use
1105 a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
1106 Dojo (L<http://www.dojotoolkit.org>).
1111 =head3 Create A Basic Stylesheet
1113 First create a central location for stylesheets under the static
1116 $ mkdir root/static/css
1118 Then open the file C<root/static/css/main.css> (the file referenced in
1119 the stylesheet href link of our wrapper above) and add the following
1138 background-color: #ddd;
1144 padding: 0 0 50% 5px;
1145 font-weight: normal;
1146 background-color: #ddd;
1159 You may wish to check out a "CSS Framework" like Emastic
1160 (L<http://code.google.com/p/emastic/>) as a way to quickly
1161 provide lots of high-quality CSS functionality.
1164 =head2 Test Run The Application
1166 Restart the development server and hit "Reload" in your web browser
1167 and you should now see a formatted version of our basic book list.
1168 Although our wrapper and stylesheet are obviously very simple, you
1169 should see how it allows us to control the overall look of an entire
1170 website from two central files. To add new pages to the site, just
1171 provide a template that fills in the C<content> section of our wrapper
1172 template -- the wrapper will provide the overall feel of the page.
1175 =head2 Updating the Generated DBIx::Class 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/Book.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_author => 'MyApp::Schema::Result::BookAuthor', '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(author => 'book_author', '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 This code defines both a C<has_many> and a C<many_to_many>
1210 relationship. The C<many_to_many> relationship is optional, but it
1211 makes it easier to map a book to its collection of authors. Without
1212 it, we would have to "walk" though the C<book_author> table as in
1213 C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
1214 will see examples on how to use DBIx::Class objects in your code soon,
1215 but note that because C<$book-E<gt>book_author> can return multiple
1216 authors, we have to use C<first> to display a single author).
1217 C<many_to_many> allows us to use the shorter C<$book-E<gt>author-
1218 E<gt>first-E<gt>last_name>. Note that you cannot define a
1219 C<many_to_many> relationship without also having the C<has_many>
1220 relationship in place.
1222 Then edit C<lib/MyApp/Schema/Result/Author.pm> and add relationship
1223 information as follows (again, be careful to put in above the C<1;> but
1224 below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1227 # Set relationships:
1232 # 1) Name of relationship, DBIC will create an accessor with this name
1233 # 2) Name of the model class referenced by this relationship
1234 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1235 __PACKAGE__->has_many(book_author => 'MyApp::Schema::Result::BookAuthor', 'author_id');
1239 # 1) Name of relationship, DBIC will create accessor with this name
1240 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1241 # 3) Name of belongs_to() relationship in model class of has_many() above
1242 # You must already have the has_many() defined to use a many_to_many().
1243 __PACKAGE__->many_to_many(book => 'book_author', 'book');
1245 Finally, do the same for the "join table,"
1246 C<lib/MyApp/Schema/Result/BookAuthor.pm>:
1249 # Set relationships:
1254 # 1) Name of relationship, DBIC will create accessor with this name
1255 # 2) Name of the model class referenced by this relationship
1256 # 3) Column name in *this* table
1257 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Book', 'book_id');
1261 # 1) Name of relationship, DBIC will create accessor with this name
1262 # 2) Name of the model class referenced by this relationship
1263 # 3) Column name in *this* table
1264 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Author', 'author_id');
1267 =head2 Run The Application
1269 Run the Catalyst development server script with the C<DBIC_TRACE> option
1270 (it might still be enabled from earlier in the tutorial, but here is an
1271 alternate way to specify the option just in case):
1273 $ DBIC_TRACE=1 script/myapp_server.pl
1275 Make sure that the application loads correctly and that you see the
1276 three dynamically created model class (one for each of the
1277 Result Classes we created).
1279 Then hit the URL L<http://localhost:3000/books/list> with your browser
1280 and be sure that the book list is displayed via the relationships
1281 established above. You can leave the development server running for
1282 the next step if you wish.
1284 B<Note:> You will not see the authors yet because the view does not yet
1285 use the new relations. Read on to the next section where we update the
1286 template to do that.
1289 =head1 UPDATING THE VIEW
1291 Let's add a new column to our book list page that takes advantage of
1292 the relationship information we manually added to our schema files in
1293 the previous section. Edit C<root/src/books/list.tt2> and replace
1294 the "empty" table cell "<td></td>" with the following:
1298 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1299 [% # loop in 'side effect notation' to load just the last names of the -%]
1300 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1301 [% # a value, so nothing will be printed here. But, if you have something -%]
1302 [% # in TT that does return a method and you don't want it printed, you -%]
1303 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1304 [% # call it and discard the return value. -%]
1305 [% tt_authors = [ ];
1306 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1307 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1308 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1309 ([% tt_authors.size | html %])
1310 [% # Use another TT vmethod to join & print the names & comma separators -%]
1311 [% tt_authors.join(', ') | html %]
1315 Then hit "Reload" in your browser (note that you don't need to reload
1316 the development server or use the C<-r> option when updating TT
1317 templates) and you should now see the number of authors each book has
1318 along with a comma-separated list of the authors' last names. (If you
1319 didn't leave the development server running from the previous step,
1320 you will obviously need to start it before you can refresh your
1323 If you are still running the development server with C<DBIC_TRACE>
1324 enabled, you should also now see five more C<SELECT> statements in the
1325 debug output (one for each book as the authors are being retrieved by
1328 SELECT me.id, me.title, me.rating FROM books me:
1329 SELECT author.id, author.first_name, author.last_name FROM book_author me
1330 JOIN author author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '1'
1331 SELECT author.id, author.first_name, author.last_name FROM book_author me
1332 JOIN author author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '2'
1333 SELECT author.id, author.first_name, author.last_name FROM book_author me
1334 JOIN author author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '3'
1335 SELECT author.id, author.first_name, author.last_name FROM book_author me
1336 JOIN author author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '4'
1337 SELECT author.id, author.first_name, author.last_name FROM book_author me
1338 JOIN author author ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '5'
1340 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1341 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1342 and > and avoid various types of dangerous hacks against your
1343 application. In a real application, you would probably want to put
1344 "| html" at the end of every field where a user has control over the
1345 information that can appear in that field (and can therefore inject
1346 markup or code if you don't "neutralize" those fields). In addition to
1347 "| html", Template Toolkit has a variety of other useful filters that
1348 can found in the documentation for
1349 L<Template::Filters|Template::Filters>.
1352 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1354 In some situations, it can be useful to run your application and
1355 display a page without using a browser. Catalyst lets you do this
1356 using the C<scripts/myapp_test.pl> script. Just supply the URL you
1357 wish to display and it will run that request through the normal
1358 controller dispatch logic and use the appropriate view to render the
1359 output (obviously, complex pages may dump a lot of text to your
1360 terminal window). For example, if you type:
1362 $ script/myapp_test.pl "/books/list"
1364 You should get the same text as if you visited
1365 L<http://localhost:3000/books/list> with the normal development server
1366 and asked your browser to view the page source.
1369 =head1 OPTIONAL INFORMATION
1371 B<NOTE: The rest of this chapter of the tutorial is optional. You can
1372 skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
1376 =head2 Using 'RenderView' for the Default View
1378 Once your controller logic has processed the request from a user, it
1379 forwards processing to your view in order to generate the appropriate
1380 response output. Catalyst uses
1381 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1382 default to automatically perform this operation. If you look in
1383 C<lib/MyApp/Controller/Root.pm>, you should see the empty
1384 definition for the C<sub end> method:
1386 sub end : ActionClass('RenderView') {}
1388 The following bullet points provide a quick overview of the
1389 C<RenderView> process:
1395 C<Root.pm> is designed to hold application-wide logic.
1399 At the end of a given user request, Catalyst will call the most specific
1400 C<end> method that's appropriate. For example, if the controller for a
1401 request has an C<end> method defined, it will be called. However, if
1402 the controller does not define a controller-specific C<end> method, the
1403 "global" C<end> method in C<Root.pm> will be called.
1407 Because the definition includes an C<ActionClass> attribute, the
1408 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1409 will be executed B<after> any code inside the definition of C<sub end>
1410 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1411 for more information on C<ActionClass>.
1415 Because C<sub end> is empty, this effectively just runs the default
1416 logic in C<RenderView>. However, you can easily extend the
1417 C<RenderView> logic by adding your own code inside the empty method body
1418 (C<{}>) created by the Catalyst Helpers when we first ran the
1419 C<catalyst.pl> to initialize our application. See
1420 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1421 detailed information on how to extend C<RenderView> in C<sub end>.
1426 =head2 Using The Default Template Name
1428 By default, C<Catalyst::View::TT> will look for a template that uses the
1429 same name as your controller action, allowing you to save the step of
1430 manually specifying the template name in each action. For example, this
1431 would allow us to remove the
1432 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1433 C<list> action in the Books controller. Open
1434 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1435 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1440 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1445 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1446 # 'Context' that's used to 'glue together' the various components
1447 # that make up the application
1448 my ($self, $c) = @_;
1450 # Retrieve all of the book records as book model objects and store in the
1451 # stash where they can be accessed by the TT template
1452 $c->stash->{books} = [$c->model('DB::Book')->all];
1454 # Set the TT template to use. You will almost always want to do this
1455 # in your action methods (actions methods respond to user input in
1456 # your controllers).
1457 #$c->stash->{template} = 'books/list.tt2';
1461 You should now be able to restart the development server as per the
1462 previous section and access the L<http://localhost:3000/books/list>
1465 B<NOTE:> Please note that if you use the default template technique,
1466 you will B<not> be able to use either the C<$c-E<gt>forward> or
1467 the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1468 Chapter 9 of the Tutorial).
1470 B<IMPORTANT:> Make sure that you do NOT skip the following section
1471 before continuing to the next chapter 4 Basic CRUD.
1473 =head2 Return To A Manually Specified Template
1475 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1476 later in the tutorial, you should remove the comment from the
1477 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1479 $c->stash->{template} = 'books/list.tt2';
1481 Then delete the C<TEMPLATE_EXTENSION> line in
1482 C<lib/MyApp/View/TT.pm>.
1484 You should then be able to restart the development server and
1485 access L<http://localhost:3000/books/list> in the same manner as
1486 with earlier sections.
1491 Kennedy Clark, C<hkclark@gmail.com>
1493 Please report any errors, issues or suggestions to the author. The
1494 most recent version of the Catalyst Tutorial can be found at
1495 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
1497 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1498 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).