3 Catalyst::Manual::Tutorial::03_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::01_Intro>
20 L<Catalyst Basics|Catalyst::Manual::Tutorial::02_CatalystBasics>
24 B<03_More Catalyst Basics>
28 L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
32 L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>
36 L<Authorization|Catalyst::Manual::Tutorial::06_Authorization>
40 L<Debugging|Catalyst::Manual::Tutorial::07_Debugging>
44 L<Testing|Catalyst::Manual::Tutorial::08_Testing>
48 L<Advanced CRUD|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
52 L<Appendices|Catalyst::Manual::Tutorial::10_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::01_Intro|Catalyst::Manual::Tutorial::01_Intro>.
72 L<Catalyst::Manual::Tutorial::01_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"
94 Change to application directory and Run "perl Makefile.PL" to make sure your install is complete
97 This creates a similar skeletal structure to what we saw in Chapter 2 of
98 the tutorial, except with C<MyApp> and C<myapp> substituted for
99 C<Hello> and C<hello>. (As noted in Chapter 2, omit the ".pl" from
100 the command if you are using Strawberry Perl.)
103 =head1 EDIT THE LIST OF CATALYST PLUGINS
105 One of the greatest benefits of Catalyst is that it has such a large
106 library of plugins and base classes available. Plugins are used to
107 seamlessly integrate existing Perl modules into the overall Catalyst
108 framework. In general, they do this by adding additional methods to the
109 C<context> object (generally written as C<$c>) that Catalyst passes to
110 every component throughout the framework.
112 By default, Catalyst enables three plugins/flags:
120 Enables the Catalyst debug output you saw when we started the
121 C<script/myapp_server.pl> development server earlier. You can remove
122 this item when you place your application into production.
124 To be technically correct, it turns out that C<-Debug> is not a plugin, but a I<flag>.
125 Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
126 line of your application class will be plugins, Catalyst supports a
127 limited number of flag options (of these, C<-Debug> is the most
128 common). See the documentation for C<Catalyst.pm> to get details on
129 other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
131 If you prefer, there are several other ways to enable debug output:
137 Use the C<$c-E<gt>debug> method
141 The C<-d> option to C<script/myapp_server.pl>
145 The C<CATALYST_DEBUG=1> environment variable (or set it to
146 zero to templorarily disable debug output).
150 B<TIP>: Depending on your needs, it can be helpful to permanently
151 remove C<-Debug> from C<lib/MyApp.pm> and then use the C<-d> option
152 to C<script/myapp_server.pl> to re-enable it just for the development
153 server. We will not be using that approach in the tutorial, but feel
154 free to make use of it in your own projects.
158 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
160 C<ConfigLoader> provides an automatic way to load configurable
161 parameters for your application from a central
162 L<Config::General|Config::General> file (versus having the values
163 hard-coded inside your Perl modules). Config::General uses syntax
164 very similar to Apache configuration files. We will see how to use
165 this feature of Catalyst during the authentication and authorization
166 sections (Chapter 5 and Chapter 6).
168 B<IMPORTANT NOTE:> If you are using a version of
169 L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, be aware
170 that Catalyst changed the default format from YAML to the more
171 straightforward C<Config::General> style. This tutorial uses the
172 newer C<myapp.conf> file for C<Config::General>. However, Catalyst
173 supports both formats and will automatically use either C<myapp.conf>
174 or C<myapp.yml> (or any other format supported by
175 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
176 L<Config::Any|Config::Any>). If you are using a version of
177 Catalyst::Devel prior to 1.06, you can convert to the newer format by
178 simply creating the C<myapp.conf> file manually and deleting
179 C<myapp.yml>. The default contents of the C<myapp.conf> you create
180 should only consist of one line:
184 B<TIP>: This script can be useful for converting between configuration
187 perl -Ilib -e 'use MyApp; use Config::General;
188 Config::General->new->save_file("myapp.conf", MyApp->config);'
192 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
194 C<Static::Simple> provides an easy way to serve static content, such
195 as images and CSS files, from the development server.
199 For our application, we want to add one new plugin into the mix. To
200 do this, edit C<lib/MyApp.pm> (this file is generally referred to as
201 your I<application class>) and delete the lines with:
203 use Catalyst qw/-Debug
207 Then replace it with:
218 B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
219 techniques to load these plugins/flags. For example, you might see
222 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
224 Don't let these variations confuse you -- they all accomplish the same
227 This tells Catalyst to start using one new plugin,
228 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
229 stack trace to the standard Catalyst "debug screen" (the screen
230 Catalyst sends to your browser when an error occurs). Be aware that
231 L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
232 browser, not in the console window from which you're running your
233 application, which is where logging output usually goes.
235 Make sure when adding new plugins you also include them as a new
236 dependancy within the Makefile.PL file. For example, after adding
237 the StackTrace plugin the Makefile.PL should include the following
240 requires 'Catalyst::Plugin::StackTrace';
249 C<__PACKAGE__> is just a shorthand way of referencing the name of the
250 package where it is used. Therefore, in C<MyApp.pm>, C<__PACKAGE__>
251 is equivalent to C<MyApp>.
255 You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
256 before you put your application into production, but it can be helpful
261 When specifying plugins, you can omit C<Catalyst::Plugin::> from the
262 name. Additionally, you can spread the plugin names across multiple
263 lines as shown here or place them all on one line.
268 =head1 CREATE A CATALYST CONTROLLER
270 As discussed earlier, controllers are where you write methods that
271 interact with user input. Typically, controller methods respond to
272 C<GET> and C<POST> requests from the user's web browser.
274 Use the Catalyst C<create> script to add a controller for book-related
277 $ script/myapp_create.pl controller Books
278 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
279 exists "/home/me/MyApp/script/../t"
280 created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm"
281 created "/home/me/MyApp/script/../t/controller_Books.t"
283 Then edit C<lib/MyApp/Controller/Books.pm> (as discussed in Chapter 2 of
284 the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
285 each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
286 and add the following method to the controller:
290 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
295 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
296 # 'Context' that's used to 'glue together' the various components
297 # that make up the application
300 # Retrieve all of the book records as book model objects and store in the
301 # stash where they can be accessed by the TT template
302 # $c->stash->{books} = [$c->model('DB::Book')->all];
303 # But, for now, use this code until we create the model later
304 $c->stash->{books} = '';
306 # Set the TT template to use. You will almost always want to do this
307 # in your action methods (action methods respond to user input in
309 $c->stash->{template} = 'books/list.tt2';
312 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
313 cutting and pasting example code from POD-based documents.
315 Programmers experienced with object-oriented Perl should recognize
316 C<$self> as a reference to the object where this method was called.
317 On the other hand, C<$c> will be new to many Perl programmers who have
318 not used Catalyst before (it's sometimes written as C<$context>). The
319 Context object is automatically passed to all Catalyst components. It
320 is used to pass information between components and provide access to
321 Catalyst and plugin functionality.
323 Catalyst actions are regular Perl methods, but they make use of
324 attributes (the "C<: Local>" next to the "C<sub list>" in the code
325 above) to provide additional information to the Catalyst dispatcher
326 logic (note that the space between the colon and the attribute name is
327 optional; you will see attributes written both ways). Most Catalyst
328 Controllers use one of five action types:
334 B<:Private> -- Use C<:Private> for methods that you want to make into
335 an action, but you do not want Catalyst to directly expose the method
336 to your users. Catalyst will not map C<:Private> methods to a URI.
337 Use them for various sorts of "special" methods (the C<begin>,
338 C<auto>, etc. discussed below) or for methods you want to be able to
339 C<forward> or C<detach> to. (If the method is a plain old "helper
340 method" that you don't want to be an action at all, then just define
341 the method without any attribute -- you can call it in your code, but
342 the Catalyst dispatcher will ignore it.)
344 There are five types of "special" build-in C<:Private> actions:
345 C<begin>, C<end>, C<default>, C<index>, and C<auto>.
351 With C<begin>, C<end>, C<default>, C<index> private actions, only the
352 most specific action of each type will be called. For example, if you
353 define a C<begin> action in your controller it will I<override> a
354 C<begin> action in your application/root controller -- I<only> the
355 action in your controller will be called.
359 Unlike the other actions where only a single method is called for each
360 request, I<every> auto action along the chain of namespaces will be
361 called. Each C<auto> action will be called I<from the application/root
362 controller down through the most specific class>.
368 B<:Path> -- C<:Path> actions let you map a method to an explicit URI
369 path. For example, "C<:Path('list')>" in
370 C<lib/MyApp/Controller/Books.pm> would match on the URL
371 C<http://localhost:3000/books/list>, but "C<:Path('/list')>" would
372 match on C<http://localhost:3000/list> (because of the leading slash).
373 You can use C<:Args()> to specify how many arguments an action should
374 accept. See L<Catalyst::Manual::Intro/Action_types> for more
375 information and examples.
379 B<:Local> -- C<:Local> is merely a shorthand for
380 "C<:Path('_name_of_method_')>". For example, these are equivalent:
381 "C<sub create_book :Local {...}>" and
382 "C<sub create_book :Path('create_book') {...}>".
386 B<:Global> -- C<:Global> is merely a shorthand for
387 "C<:Path('/_name_of_method_')>". For example, these are equivalent:
388 "C<sub create_book :Global {...}>" and
389 "C<sub create_book :Path('/create_book') {...}>".
393 B<:Chained> -- Newer Catalyst applications tend to use the Chained
394 dispatch form of action types because of its power and flexibility.
395 It allows a series of controller methods to be automatically dispatched
396 to service a single user request. See
397 L<Catalyst::Manual::Tutorial::04_BasicCRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
398 and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
399 for more information on chained actions.
403 You should refer to L<Catalyst::Manual::Intro/Action_types> for
404 additional information and for coverage of some lesser-used action
405 types not discussed here (C<Regex> and C<LocalRegex>).
408 =head1 CATALYST VIEWS
410 As mentioned in Chapter 2 of the tutorial, views are where you render
411 output, typically for display in the user's web browser (but also
412 possibly using into output-generation systems, such as PDF or JSON).
413 The code in C<lib/MyApp/View> selects the I<type> of view to use, with
414 the actual rendering template found in the C<root> directory. As with
415 virtually every aspect of Catalyst, options abound when it comes to the
416 specific view technology you adopt inside your application. However,
417 most Catalyst applications use the Template Toolkit, known as TT (for
418 more information on TT, see L<http://www.template-toolkit.org>). Other
419 somewhat popular view technologies include Mason
420 (L<http://www.masonhq.com> and L<http://www.masonbook.com>) and
421 L<HTML::Template> (L<http://html-template.sourceforge.net>).
424 =head2 Create a Catalyst View
426 When using TT for the Catalyst view, the main helper script
427 is L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>.
428 You may also come across references to
429 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>,
430 but its use is now deprecated.
432 Enter the following command to enable the C<TT> style of view
433 rendering for this tutorial:
435 $ script/myapp_create.pl view TT TT
436 exists "/home/me/MyApp/script/../lib/MyApp/View"
437 exists "/home/me/MyApp/script/../t"
438 created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm"
439 created "/home/me/MyApp/script/../t/view_TT.t"
441 This simply creates a view called C<TT> (the second 'TT' argument) in
442 a file called C<TT.pm> (the first 'TT' argument). It is now up to you
443 to decide how you want to structure your view layout. For the
444 tutorial, we will start with a very simple TT template to initially
445 demonstrate the concepts, but quickly migrate to a more typical
446 "wrapper page" type of configuration (where the "wrapper" controls the
447 overall "look and feel" of your site from a single file or set of
450 Edit C<lib/MyApp/View/TT.pm> and you should see that the default
451 contents contains something similar to the following:
453 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
455 And update it to match:
458 # Change default TT extension
459 TEMPLATE_EXTENSION => '.tt2',
460 # Set the location for TT files
462 MyApp->path_to( 'root', 'src' ),
466 B<NOTE:> Make sure to add a comma after '.tt2' outside the single
469 This changes the default extension for Template Toolkit from '.tt' to
470 '.tt2' and changes the base directory for your template files from
471 C<root> to C<root/src>. Stick with these conventions for the
472 tutorial, but feel free to use whatever options you desire in your
473 applications (as with most things Perl, there's more than one way to
476 B<Note:> We will use C<root/src> as the base directory for our
477 template files, with a full naming convention of
478 C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
479 use C<root/> as the base (with a full filename pattern of
480 C<root/_controller_name_/_action_name_.tt2>).
483 =head2 Create a TT Template Page
485 First create a directory for book-related TT templates:
487 $ mkdir -p root/src/books
489 Then create C<root/src/books/list.tt2> in your editor and enter:
491 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
492 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
493 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
494 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
496 [% # Provide a title -%]
497 [% META title = 'Book List' -%]
500 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
501 [% # Display each book in a table row %]
502 [% FOREACH book IN books -%]
504 <td>[% book.title %]</td>
505 <td>[% book.rating %]</td>
511 As indicated by the inline comments above, the C<META title> line uses
512 TT's META feature to provide a title to the "wrapper" that we will
513 create later. Meanwhile, the C<FOREACH> loop iterates through each
514 C<book> model object and prints the C<title> and C<rating> fields.
516 The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
517 supports a wide variety of directives for "calling" other files,
518 looping, conditional logic, etc. In general, TT simplifies the usual
519 range of Perl operators down to the single dot (".") operator. This
520 applies to operations as diverse as method calls, hash lookups, and list
522 L<http://search.cpan.org/perldoc?Template::Manual::Variables> for
523 details and examples). In addition to the usual L<Template> module Pod
524 documentation, you can access the TT manual at
525 L<http://search.cpan.org/perldoc?Template::Manual>.
527 B<TIP:> While you can build all sorts of complex logic into your TT
528 templates, you should in general keep the "code" part of your
529 templates as simple as possible. If you need more complex logic,
530 create helper methods in your model that abstract out a set of code
531 into a single call from your TT template. (Note that the same is true
532 of your controller logic as well -- complex sections of code in your
533 controllers should often be pulled out and placed into your model
534 objects.) In Chapter 4 of the tutorial we will explore some extremely
535 helpful and powerful features of L<DBIx::Class> that allow you to pull
536 code out of your views and controllers and place it where it
537 rightfully belongs in a model class.
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::07_Debugging> chapter 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
564 SQLite (L<http://www.sqlite.org>), a popular database that is
565 lightweight and easy to use. Be sure to get at least version 3. Open
566 create a database table and load some sample data. We will use
567 L<SQLite|http://www.sqlite.org>, a popular database that is
568 lightweight and easy to use. Be sure to get at least version 3. Open
569 C<myapp01.sql> in your editor and enter:
572 -- Create a very simple database to hold book and author information
575 id INTEGER PRIMARY KEY,
579 -- 'book_author' is a many-to-many join table between books & authors
580 CREATE TABLE book_author (
583 PRIMARY KEY (book_id, author_id)
585 CREATE TABLE author (
586 id INTEGER PRIMARY KEY,
591 --- Load some sample data
593 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
594 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
595 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
596 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
597 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
598 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
599 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
600 INSERT INTO author VALUES (3, 'Christian', 'Degu');
601 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
602 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
603 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
604 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
605 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
606 INSERT INTO book_author VALUES (1, 1);
607 INSERT INTO book_author VALUES (1, 2);
608 INSERT INTO book_author VALUES (1, 3);
609 INSERT INTO book_author VALUES (2, 4);
610 INSERT INTO book_author VALUES (3, 5);
611 INSERT INTO book_author VALUES (4, 6);
612 INSERT INTO book_author VALUES (4, 7);
613 INSERT INTO book_author VALUES (5, 8);
615 Then use the following command to build a C<myapp.db> SQLite database:
617 $ sqlite3 myapp.db < myapp01.sql
619 If you need to create the database more than once, you probably want to
620 issue the C<rm myapp.db> command to delete the database before you use
621 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
623 Once the C<myapp.db> database file has been created and initialized, you
624 can use the SQLite command line environment to do a quick dump of the
629 Enter ".help" for instructions
630 sqlite> select * from book;
631 1|CCSP SNRS Exam Certification Guide|5
632 2|TCP/IP Illustrated, Volume 1|5
633 3|Internetworking with TCP/IP Vol.1|4
635 5|Designing with Web Standards|5
641 $ sqlite3 myapp.db "select * from book"
642 1|CCSP SNRS Exam Certification Guide|5
643 2|TCP/IP Illustrated, Volume 1|5
644 3|Internetworking with TCP/IP Vol.1|4
646 5|Designing with Web Standards|5
648 As with most other SQL tools, if you are using the full "interactive"
649 environment you need to terminate your SQL commands with a ";" (it's not
650 required if you do a single SQL statement on the command line). Use
651 ".q" to exit from SQLite from the SQLite interactive mode and return to
652 your OS command prompt.
654 Please note that here we have chosen to use 'singular' table names. This
655 is because the default inflection code for L<DBIx::Class::Schema::Loader>
656 does NOT handle plurals. There has been much philosophical discussion
657 on whether table names should be plural or singular. There is no one
658 correct answer, as long as one makes a choice and remains consistent
659 with it. If you prefer plural table names (e.g. they are easier and
660 more natural to read) then you will need to pass it an inflect_map
661 option. See L<DBIx::Class::Schema::Loader> for more information.
663 For using other databases, such as PostgreSQL or MySQL, see
664 L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices>.
667 =head1 DATABASE ACCESS WITH DBIx::Class
669 Catalyst can be used with virtually any form of datastore available
670 via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
671 can be used to access databases through the traditional Perl L<DBI>
672 interface or you can use a model to access files of any type on the
673 filesystem. However, most Catalyst applications use some form of
674 object-relational mapping (ORM) technology to create objects
675 associated with tables in a relational database. Matt Trout's
676 L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
677 as the Perl-based ORM technology of choice. Most new Catalyst
678 applications rely on DBIx::Class, as will this tutorial.
680 Although DBIx::Class has included support for a C<create=dynamic> mode
681 to automatically read the database structure every time the
682 application starts, it's use is no longer recommended. While it can
683 make for "flashy" demos, the use of the C<create=static> mode we use
684 below can be implemented just as quickly and provides many advantages
685 (such as the ability to add your own methods to the overall DBIC
686 framework, a technique that we see in Chapter 4).
689 =head2 Make Sure You Have a Recent Version of the DBIx::Class Model
691 First, let's be sure we have a recent version of the DBIC helper,
692 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
693 running this command:
695 $ perl -MCatalyst::Model::DBIC::Schema -e \
696 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
699 Please note the '\' above. Depending on your environment, you might
700 be able to cut and paste the text as shown or need to remove the '\'
701 character to that the command is all on a single line.
703 You should have version 0.31 or greater if you are following along
704 with Debian 5. In other environments, you may need to run this
705 command to install it directly from CPAN:
707 $ sudo cpan Catalyst::Model::DBIC::Schema
709 And re-run the version print command to verify that you are now at
713 =head2 Create Static DBIx::Class Schema Files
715 Before you continue, make sure your C<myapp.db> database file is in
716 the application's topmost directory. Now use the model helper with
717 the C<create=static> option to read the database with
718 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
719 automatically build the required files for us:
721 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
722 create=static dbi:SQLite:myapp.db
723 exists "/home/me/MyApp/script/../lib/MyApp/Model"
724 exists "/home/me/MyApp/script/../t"
725 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
726 Schema dump completed.
727 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
728 created "/home/me/MyApp/script/../t/model_DB.t"
730 Please note the '\' above. Depending on your environment, you might
731 be able to cut and paste the text as shown or need to remove the '\'
732 character to that the command is all on a single line.
734 The C<script/myapp_create.pl> command breaks down like this:
740 C<DB> is the name of the model class to be created by the helper in
745 C<DBIC::Schema> is the type of the model to create.
749 C<MyApp::Schema> is the name of the DBIC schema file written to
750 C<lib/MyApp/Schema.pm>.
754 C<create=static> causes
755 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
756 load the schema as it runs and then write that information out
761 And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
766 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
767 only contains a call to the C<load_namespaces> method. You will also
768 find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
769 has a subdirectory called "Result". This "Result" subdirectory then
770 has files named according to each of the tables in our simple database
771 (C<Author.pm>, C<BookAuthor.pm>, and C<Book.pm>). These three
772 files are called "Result Classes" in DBIx::Class nomenclature. Although the
773 Result Class files are named after tables in our database, the classes
774 correspond to the I<row-level data> that is returned by DBIC (more on
775 this later, especially in
776 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
778 The idea with the Result Source files created under
779 C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
780 edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
781 warning. If you place all of your changes below that point in the
782 file, you can regenerate the automatically created information at the
783 top of each file should your database structure get updated.
785 Also note the "flow" of the model information across the various files
786 and directories. Catalyst will initially load the model from
787 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
788 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the
789 call to C<load_namespaces> in C<Schema.pm> will load each of the
790 "Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
791 The final outcome is that Catalyst will dynamically create three
792 table-specific Catalyst models every time the application starts (you
793 can see these three model files listed in the debug output generated
794 when you launch the application).
796 B<NOTE:> Older versions of
797 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
798 deprecated DBIx::Class C<load_classes> technique instead of the newer
799 C<load_namspaces>. For new applications, please try to use
800 C<load_namespaces> since it more easily supports a very useful DBIC
801 technique called "ResultSet Classes." If you need to convert an
802 existing application from "load_classes" to "load_namespaces," you can
803 use this process to automate the migration (but first make sure you
804 have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
806 $ # First delete the existing schema file to disable "compatibility" mode
807 $ rm lib/MyApp/Schema.pm
809 $ # Then re-run the helper to build the files for "load_namespaces"
810 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
811 create=static dbi:SQLite:myapp.db
813 $ # Now convert the existing files over
814 $ cd lib/MyApp/Schema
815 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
816 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
817 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
820 $ # And finally delete the old files
821 $ rm lib/MyApp/Schema/*.pm
823 The "C<perl -MIO::ALL ...>" script will copy all the customized
824 relationship (and other) information below "C<# DO NOT MODIFY>" line
825 from the old files in C<lib/MyApp/Schema> to the new files in
826 C<lib/MyApp/Schema/Result> (we will be starting to add some
827 "customized relationship information in the section below).
830 =head1 ENABLE THE MODEL IN THE CONTROLLER
832 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
833 left disabled earlier so that your version matches the following (un-
834 comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
835 and delete the next 2 lines):
839 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
844 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
845 # 'Context' that's used to 'glue together' the various components
846 # that make up the application
849 # Retrieve all of the book records as book model objects and store in the
850 # stash where they can be accessed by the TT template
851 $c->stash->{books} = [$c->model('DB::Book')->all];
853 # Set the TT template to use. You will almost always want to do this
854 # in your action methods (action methods respond to user input in
856 $c->stash->{template} = 'books/list.tt2';
859 B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
860 above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
861 two are equivalent. Either way, C<$c-E<gt>model> returns a
862 L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
863 against the database and iterating over the set of results that is
866 We are using the C<-E<gt>all> to fetch all of the books. DBIC
867 supports a wide variety of more advanced operations to easily do
868 things like filtering and sorting the results. For example, the
869 following could be used to sort the results by descending title:
871 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
873 Some other examples are provided in
874 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
875 additional information found at L<DBIx::Class::ResultSet/search>,
876 L<DBIx::Class::Manual::FAQ/Searching>,
877 L<DBIx::Class::Manual::Intro|DBIx::Class::Manual::Intro>
878 and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
881 =head2 Test Run The Application
883 First, let's enable an environment variable that causes DBIx::Class to
884 dump the SQL statements used to access the database. This is a
885 helpful trick when you are trying to debug your database-oriented
888 $ export DBIC_TRACE=1
890 This assumes you are using bash as your shell -- adjust accordingly if
891 you are using a different shell (for example, under tcsh, use
892 C<setenv DBIC_TRACE 1>).
894 B<NOTE:> You can also set this in your code using
895 C<$class-E<gt>storage-E<gt>debug(1);>. See
896 L<DBIx::Class::Manual::Troubleshooting> for details (including options
897 to log to a file instead of displaying to the Catalyst development server
900 Then launch the Catalyst development server. The log output should
901 display something like:
903 $ script/myapp_server.pl
904 [debug] Debug messages enabled
905 [debug] Statistics enabled
906 [debug] Loaded plugins:
907 .----------------------------------------------------------------------------.
908 | Catalyst::Plugin::ConfigLoader 0.27 |
909 | Catalyst::Plugin::StackTrace 0.11 |
910 | Catalyst::Plugin::Static::Simple 0.25 |
911 '----------------------------------------------------------------------------'
913 [debug] Loaded dispatcher "Catalyst::Dispatcher"
914 [debug] Loaded engine "Catalyst::Engine::HTTP"
915 [debug] Found home "/home/me/MyApp"
916 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
917 [debug] Loaded components:
918 .-----------------------------------------------------------------+----------.
920 +-----------------------------------------------------------------+----------+
921 | MyApp::Controller::Books | instance |
922 | MyApp::Controller::Root | instance |
923 | MyApp::Model::DB | instance |
924 | MyApp::Model::DB::Author | class |
925 | MyApp::Model::DB::Book | class |
926 | MyApp::Model::DB::BookAuthor | class |
927 | MyApp::View::TT | instance |
928 '-----------------------------------------------------------------+----------'
930 [debug] Loaded Private actions:
931 .----------------------+--------------------------------------+--------------.
932 | Private | Class | Method |
933 +----------------------+--------------------------------------+--------------+
934 | /default | MyApp::Controller::Root | default |
935 | /end | MyApp::Controller::Root | end |
936 | /index | MyApp::Controller::Root | index |
937 | /books/index | MyApp::Controller::Books | index |
938 | /books/list | MyApp::Controller::Books | list |
939 '----------------------+--------------------------------------+--------------'
941 [debug] Loaded Path actions:
942 .-------------------------------------+--------------------------------------.
944 +-------------------------------------+--------------------------------------+
947 | /books | /books/index |
948 | /books/list | /books/list |
949 '-------------------------------------+--------------------------------------'
951 [info] MyApp powered by Catalyst 5.80013
952 You can connect to your server at http://debian:3000
954 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
955 the 'base' directory of your application, not inside the C<script>
956 directory itself or it will not be able to locate the C<myapp.db>
957 database file. You can use a fully qualified or a relative path to
958 locate the database file, but we did not specify that when we ran the
959 model helper earlier.
961 Some things you should note in the output above:
967 Catalyst::Model::DBIC::Schema dynamically created three model classes,
968 one to represent each of the three tables in our database
969 (C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
970 and C<MyApp::Model::DB::Book>).
974 The "list" action in our Books controller showed up with a path of
979 Point your browser to L<http://localhost:3000> and you should still get
980 the Catalyst welcome page.
982 Next, to view the book list, change the URL in your browser to
983 L<http://localhost:3000/books/list>. You should get a list of the five
984 books loaded by the C<myapp01.sql> script above without any formatting.
985 The rating for each book should appear on each row, but the "Author(s)"
986 column will still be blank (we will fill that in later).
988 Also notice in the output of the C<script/myapp_server.pl> that
989 DBIx::Class used the following SQL to retrieve the data:
991 SELECT me.id, me.title, me.rating FROM book me
993 because we enabled DBIC_TRACE.
995 You now have the beginnings of a simple but workable web application.
996 Continue on to future sections and we will develop the application
1000 =head1 CREATE A WRAPPER FOR THE VIEW
1002 When using TT, you can (and should) create a wrapper that will
1003 literally wrap content around each of your templates. This is
1004 certainly useful as you have one main source for changing things that
1005 will appear across your entire site/application instead of having to
1006 edit many individual files.
1009 =head2 Configure TT.pm For The Wrapper
1011 In order to create a wrapper, you must first edit your TT view and
1012 tell it where to find your wrapper file.
1014 Edit you TT view in C<lib/MyApp/View/TT.pm> and change it to match the
1017 __PACKAGE__->config(
1018 # Change default TT extension
1019 TEMPLATE_EXTENSION => '.tt2',
1020 # Set the location for TT files
1022 MyApp->path_to( 'root', 'src' ),
1024 # Set to 1 for detailed timer stats in your HTML as comments
1026 # This is your wrapper template located in the 'root/src'
1027 WRAPPER => 'wrapper.tt2',
1031 =head2 Create the Wrapper Template File and Stylesheet
1033 Next you need to set up your wrapper template. Basically, you'll want
1034 to take the overall layout of your site and put it into this file.
1035 For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1037 <?xml version="1.0" encoding="UTF-8"?>
1038 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1039 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
1041 <title>[% template.title or "My Catalyst App!" %]</title>
1042 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1048 [%# Your logo could go here -%]
1049 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1050 [%# Insert the page title -%]
1051 <h1>[% template.title or site.title %]</h1>
1054 <div id="bodyblock">
1058 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1059 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1061 </div><!-- end menu -->
1064 [%# Status and error messages %]
1065 <span class="message">[% status_msg %]</span>
1066 <span class="error">[% error_msg %]</span>
1067 [%# This is where TT will stick all of your template's contents. -%]
1069 </div><!-- end content -->
1070 </div><!-- end bodyblock -->
1072 <div id="footer">Copyright (c) your name goes here</div>
1073 </div><!-- end outer -->
1078 Notice the status and error message sections in the code above:
1080 <span class="status">[% status_msg %]</span>
1081 <span class="error">[% error_msg %]</span>
1083 If we set either message in the Catalyst stash (e.g.,
1084 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1085 will be displayed whenever any view used by that request is rendered.
1086 The C<message> and C<error> CSS styles can be customized to suit your
1087 needs in the C<root/static/css/main.css> file we create below.
1095 The Catalyst stash only lasts for a single HTTP request. If
1096 you need to retain information across requests you can use
1097 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
1098 Catalyst sessions in the Authentication chapter of the tutorial).
1102 Although it is beyond the scope of this tutorial, you may wish to use
1103 a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
1104 Dojo (L<http://www.dojotoolkit.org>).
1109 =head3 Create A Basic Stylesheet
1111 First create a central location for stylesheets under the static
1114 $ mkdir root/static/css
1116 Then open the file C<root/static/css/main.css> (the file referenced in
1117 the stylesheet href link of our wrapper above) and add the following
1136 background-color: #ddd;
1142 padding: 0 0 50% 5px;
1143 font-weight: normal;
1144 background-color: #ddd;
1157 You may wish to check out a "CSS Framework" like Emastic
1158 (L<http://code.google.com/p/emastic/>) as a way to quickly
1159 provide lots of high-quality CSS functionality.
1162 =head2 Test Run The Application
1164 Restart the development server and hit "Reload" in your web browser
1165 and you should now see a formatted version of our basic book list.
1166 Although our wrapper and stylesheet are obviously very simple, you
1167 should see how it allows us to control the overall look of an entire
1168 website from two central files. To add new pages to the site, just
1169 provide a template that fills in the C<content> section of our wrapper
1170 template -- the wrapper will provide the overall feel of the page.
1173 =head2 Updating the Generated DBIx::Class Result Class Files
1175 Let's manually add some relationship information to the auto-generated
1176 Result Class files. (Note: if you are using a database other than
1177 SQLite, such as PostgreSQL, then the relationship could have been
1178 automatically placed in the Result Class files. If so, you can skip
1179 this step.) First edit C<lib/MyApp/Schema/Result/Book.pm> and add the
1180 following text below the C<# You can replace this text...> comment:
1183 # Set relationships:
1188 # 1) Name of relationship, DBIC will create accessor with this name
1189 # 2) Name of the model class referenced by this relationship
1190 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1191 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthor', 'book_id');
1195 # 1) Name of relationship, DBIC will create accessor with this name
1196 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1197 # 3) Name of belongs_to() relationship in model class of has_many() above
1198 # You must already have the has_many() defined to use a many_to_many().
1199 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1202 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1203 file. As with any Perl package, we need to end the last line with
1204 a statement that evaluates to C<true>. This is customarily done with
1205 C<1;> on a line by itself.
1207 This code defines both a C<has_many> and a C<many_to_many>
1208 relationship. The C<many_to_many> relationship is optional, but it
1209 makes it easier to map a book to its collection of authors. Without
1210 it, we would have to "walk" though the C<book_author> table as in
1211 C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
1212 will see examples on how to use DBIx::Class objects in your code soon,
1213 but note that because C<$book-E<gt>book_author> can return multiple
1214 authors, we have to use C<first> to display a single author).
1215 C<many_to_many> allows us to use the shorter
1216 C<$book-E<gt>author-E<gt>first-E<gt>last_name>. Note that you cannot
1217 define a C<many_to_many> relationship without also having the
1218 C<has_many> relationship in place.
1220 Then edit C<lib/MyApp/Schema/Result/Author.pm> and add relationship
1221 information as follows (again, be careful to put in above the C<1;> but
1222 below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1225 # Set relationships:
1230 # 1) Name of relationship, DBIC will create an accessor with this name
1231 # 2) Name of the model class referenced by this relationship
1232 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1233 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthor', 'author_id');
1237 # 1) Name of relationship, DBIC will create accessor with this name
1238 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1239 # 3) Name of belongs_to() relationship in model class of has_many() above
1240 # You must already have the has_many() defined to use a many_to_many().
1241 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
1243 Finally, do the same for the "join table,"
1244 C<lib/MyApp/Schema/Result/BookAuthor.pm>:
1247 # Set relationships:
1252 # 1) Name of relationship, DBIC will create accessor with this name
1253 # 2) Name of the model class referenced by this relationship
1254 # 3) Column name in *this* table
1255 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Book', 'book_id');
1259 # 1) Name of relationship, DBIC will create accessor with this name
1260 # 2) Name of the model class referenced by this relationship
1261 # 3) Column name in *this* table
1262 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Author', 'author_id');
1265 =head2 Run The Application
1267 Run the Catalyst development server script with the C<DBIC_TRACE> option
1268 (it might still be enabled from earlier in the tutorial, but here is an
1269 alternate way to specify the option just in case):
1271 $ DBIC_TRACE=1 script/myapp_server.pl
1273 Make sure that the application loads correctly and that you see the
1274 three dynamically created model class (one for each of the
1275 Result Classes we created).
1277 Then hit the URL L<http://localhost:3000/books/list> with your browser
1278 and be sure that the book list still displays correctly. You can leave
1279 the development server running for the next step if you wish.
1281 B<Note:> You will not see the authors yet because the view does not yet
1282 use the new relations. Read on to the next section where we update the
1283 template to do that.
1286 =head1 UPDATING THE VIEW
1288 Let's add a new column to our book list page that takes advantage of
1289 the relationship information we manually added to our schema files in
1290 the previous section. Edit C<root/src/books/list.tt2> and replace
1291 the "empty" table cell "<td></td>" with the following:
1295 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1296 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1297 [% # loop in 'side effect notation' to load just the last names of the -%]
1298 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
1299 [% # a value, so nothing will be printed here. But, if you have something -%]
1300 [% # in TT that does return a value and you don't want it printed, you -%]
1301 [% # 1) assign it to a bogus value, or -%]
1302 [% # 2) use the CALL keyword to call it and discard the return value. -%]
1303 [% tt_authors = [ ];
1304 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1305 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1306 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1307 ([% tt_authors.size | html %])
1308 [% # Use another TT vmethod to join & print the names & comma separators -%]
1309 [% tt_authors.join(', ') | html %]
1313 B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1314 possible out of your views. This kind of logic belongs in your model
1315 (the same goes for controllers -- keep them as "thin" as possible and
1316 push all of the "complicated code" out to your model objects). Avoid
1317 code like you see in the previous example -- we are only using it here
1318 to show some extra features in TT until we get to the more advanced
1319 model features we will see in Chapter 4 (see
1320 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1322 Then hit "Reload" in your browser (note that you don't need to reload
1323 the development server or use the C<-r> option when updating TT
1324 templates) and you should now see the number of authors each book has
1325 along with a comma-separated list of the authors' last names. (If you
1326 didn't leave the development server running from the previous step,
1327 you will obviously need to start it before you can refresh your
1330 If you are still running the development server with C<DBIC_TRACE>
1331 enabled, you should also now see five more C<SELECT> statements in the
1332 debug output (one for each book as the authors are being retrieved by
1335 SELECT me.id, me.title, me.rating FROM book me:
1336 SELECT author.id, author.first_name, author.last_name FROM book_author me
1337 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '1'
1338 SELECT author.id, author.first_name, author.last_name FROM book_author me
1339 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '2'
1340 SELECT author.id, author.first_name, author.last_name FROM book_author me
1341 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '3'
1342 SELECT author.id, author.first_name, author.last_name FROM book_author me
1343 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '4'
1344 SELECT author.id, author.first_name, author.last_name FROM book_author me
1345 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '5'
1347 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1348 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1349 and > and avoid various types of dangerous hacks against your
1350 application. In a real application, you would probably want to put
1351 "| html" at the end of every field where a user has control over the
1352 information that can appear in that field (and can therefore inject
1353 markup or code if you don't "neutralize" those fields). In addition to
1354 "| html", Template Toolkit has a variety of other useful filters that
1355 can found in the documentation for
1356 L<Template::Filters|Template::Filters>.
1359 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1361 In some situations, it can be useful to run your application and
1362 display a page without using a browser. Catalyst lets you do this
1363 using the C<scripts/myapp_test.pl> script. Just supply the URL you
1364 wish to display and it will run that request through the normal
1365 controller dispatch logic and use the appropriate view to render the
1366 output (obviously, complex pages may dump a lot of text to your
1367 terminal window). For example, if you type:
1369 $ script/myapp_test.pl "/books/list"
1371 You should get the same text as if you visited
1372 L<http://localhost:3000/books/list> with the normal development server
1373 and asked your browser to view the page source.
1376 =head1 OPTIONAL INFORMATION
1378 B<NOTE: The rest of this chapter of the tutorial is optional. You can
1379 skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
1383 =head2 Using 'RenderView' for the Default View
1385 Once your controller logic has processed the request from a user, it
1386 forwards processing to your view in order to generate the appropriate
1387 response output. Catalyst uses
1388 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1389 default to automatically perform this operation. If you look in
1390 C<lib/MyApp/Controller/Root.pm>, you should see the empty
1391 definition for the C<sub end> method:
1393 sub end : ActionClass('RenderView') {}
1395 The following bullet points provide a quick overview of the
1396 C<RenderView> process:
1402 C<Root.pm> is designed to hold application-wide logic.
1406 At the end of a given user request, Catalyst will call the most specific
1407 C<end> method that's appropriate. For example, if the controller for a
1408 request has an C<end> method defined, it will be called. However, if
1409 the controller does not define a controller-specific C<end> method, the
1410 "global" C<end> method in C<Root.pm> will be called.
1414 Because the definition includes an C<ActionClass> attribute, the
1415 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1416 will be executed B<after> any code inside the definition of C<sub end>
1417 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1418 for more information on C<ActionClass>.
1422 Because C<sub end> is empty, this effectively just runs the default
1423 logic in C<RenderView>. However, you can easily extend the
1424 C<RenderView> logic by adding your own code inside the empty method body
1425 (C<{}>) created by the Catalyst Helpers when we first ran the
1426 C<catalyst.pl> to initialize our application. See
1427 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1428 detailed information on how to extend C<RenderView> in C<sub end>.
1433 =head2 RenderView's "dump_info" Feature
1435 One of the nice features of C<RenderView> is that it automatically
1436 allows you to add C<dump_info=1> to the end of any URL for your
1437 application and it will force the display of the "exception dump"
1438 screen to the client browser. You can try this out by starting the
1439 development server as before and then point your browser to this URL:
1441 http://localhost:3000/books/list?dump_info=1
1443 You should get a page with the following message at the top:
1445 Caught exception in MyApp::Controller::Root->end "Forced debug -
1446 Scrubbed output at /usr/share/perl5/Catalyst/Action/RenderView.pm line 46."
1448 Along with a summary of your application's state at the end of the
1449 processing for that request. The "Stash" section should show a
1450 summarized version of the DBIC book model objects. If desired, you
1451 can adjust the summarization logic (called "scrubbing" logic) -- see
1452 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for
1455 Note that you shouldn't need to worry about "normal clients" using
1456 this technique to "reverse engineer" your application -- C<RenderView>
1457 only supports the C<dump_info=1> feature when your application is
1458 running in C<-Debug> mode (something you won't do once you have your
1459 application deployed in production).
1462 =head2 Using The Default Template Name
1464 By default, C<Catalyst::View::TT> will look for a template that uses the
1465 same name as your controller action, allowing you to save the step of
1466 manually specifying the template name in each action. For example, this
1467 would allow us to remove the
1468 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1469 C<list> action in the Books controller. Open
1470 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1471 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1476 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1481 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1482 # 'Context' that's used to 'glue together' the various components
1483 # that make up the application
1484 my ($self, $c) = @_;
1486 # Retrieve all of the book records as book model objects and store in the
1487 # stash where they can be accessed by the TT template
1488 $c->stash->{books} = [$c->model('DB::Book')->all];
1490 # Set the TT template to use. You will almost always want to do this
1491 # in your action methods (actions methods respond to user input in
1492 # your controllers).
1493 #$c->stash->{template} = 'books/list.tt2';
1497 You should now be able to restart the development server as per the
1498 previous section and access the L<http://localhost:3000/books/list>
1501 B<NOTE:> Please note that if you use the default template technique,
1502 you will B<not> be able to use either the C<$c-E<gt>forward> or
1503 the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1504 Chapter 9 of the Tutorial).
1506 B<IMPORTANT:> Make sure that you do NOT skip the following section
1507 before continuing to the next chapter 4 Basic CRUD.
1510 =head2 Return To A Manually Specified Template
1512 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1513 later in the tutorial, you should remove the comment from the
1514 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1516 $c->stash->{template} = 'books/list.tt2';
1518 Then delete the C<TEMPLATE_EXTENSION> line in
1519 C<lib/MyApp/View/TT.pm>.
1521 You should then be able to restart the development server and
1522 access L<http://localhost:3000/books/list> in the same manner as
1523 with earlier sections.
1528 Kennedy Clark, C<hkclark@gmail.com>
1530 Please report any errors, issues or suggestions to the author. The
1531 most recent version of the Catalyst Tutorial can be found at
1532 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
1534 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1535 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).