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 virtually
67 Source code for the tutorial in included in the F</home/catalyst/Final>
68 directory of the Tutorial Virtual machine (one subdirectory per
69 chapter). There are also instructions for downloading the code in
70 L<Catalyst::Manual::Tutorial::01_Intro>.
73 L<Catalyst::Manual::Tutorial::01_Intro/STARTING WITH THE TUTORIAL VIRTUAL MACHINE>
74 before doing the rest of this tutorial. Although the tutorial should
75 work correctly under most any recent version of Perl running on any
76 operating system, the tutorial has been written using the virtual
77 machine that is available for download. The entire tutorial has been
78 tested to be sure it runs correctly in this environment, so it is
79 the most trouble-free way to get started with Catalyst.
82 =head1 CREATE A NEW APPLICATION
84 The remainder of the tutorial will build an application called C<MyApp>.
85 First use the Catalyst C<catalyst.pl> script to initialize the framework
86 for the C<MyApp> application (make sure you aren't still inside the
87 directory of the C<Hello> application from the previous chapter of the
88 tutorial or in a directory that already has a "MyApp" subdirectory):
92 created "MyApp/script"
96 created "MyApp/script/myapp_create.pl"
97 Change to application directory and Run "perl Makefile.PL" to make sure your install is complete
99 And change the "MyApp" directory the helper created:
103 This creates a similar skeletal structure to what we saw in Chapter 2 of
104 the tutorial, except with C<MyApp> and C<myapp> substituted for C<Hello>
105 and C<hello>. (As noted in Chapter 2, omit the ".pl" from the command
106 if you are using Strawberry Perl.)
109 =head1 EDIT THE LIST OF CATALYST PLUGINS
111 One of the greatest benefits of Catalyst is that it has such a large
112 library of base classes and plugins available that you can use to easily
113 add functionality to your application. Plugins are used to seamlessly
114 integrate existing Perl modules into the overall Catalyst framework. In
115 general, they do this by adding additional methods to the C<context>
116 object (generally written as C<$c>) that Catalyst passes to every
117 component throughout the framework.
119 Take a look at the file C<lib/MyApp.pm> that the helper created above.
120 By default, Catalyst enables three plugins/flags:
128 Enables the Catalyst debug output you saw when we started the
129 C<script/myapp_server.pl> development server earlier. You can remove
130 this item when you place your application into production.
132 To be technically correct, it turns out that C<-Debug> is not a plugin,
133 but a I<flag>. Although most of the items specified on the C<use
134 Catalyst> line of your application class will be plugins, Catalyst
135 supports a limited number of flag options (of these, C<-Debug> is the
136 most common). See the documentation for
137 L<https://metacpan.org/module/Catalyst|Catalyst.pm> to get details on
138 other flags (currently C<-Engine>, C<-Home>, C<-Log>, and C<-Stats>).
140 If you prefer, there are several other ways to enable debug output:
146 the C<$c-E<gt>debug> method on the C<$c> Catalyst context object
150 the C<-d> option on the C<script/myapp_server.pl> script
154 the C<CATALYST_DEBUG=1> environment variable (or C<CATALYST_DEBUG=0>
155 to temporarily disable debug output)
159 B<TIP>: Depending on your needs, it can be helpful to permanently remove
160 C<-Debug> from C<lib/MyApp.pm> and then use the C<-d> option to
161 C<script/myapp_server.pl> to re-enable it when needed. We will not be
162 using that approach in the tutorial, but feel free to make use of it in
167 L<Catalyst::Plugin::ConfigLoader>
169 C<ConfigLoader> provides an automatic way to load configurable
170 parameters for your application from a central
171 L<Config::General> file (versus having the values
172 hard-coded inside your Perl modules). Config::General uses syntax very
173 similar to Apache configuration files. We will see how to use this
174 feature of Catalyst during the authentication and authorization sections
175 (L<Chapter 5|Catalyst::Manual::Tutorial::05_Authentication> and
176 L<Chapter 6|Catalyst::Manual::Tutorial::06_Authorization>).
178 B<IMPORTANT NOTE:> If you are using a version of
179 L<Catalyst::Devel> prior to version 1.06, be aware that
180 Catalyst changed the default format from YAML to the more
181 straightforward C<Config::General> style. This tutorial uses the newer
182 C<myapp.conf> file for C<Config::General>. However, Catalyst supports
183 both formats and will automatically use either C<myapp.conf> or
184 C<myapp.yml> (or any other format supported by
185 L<Catalyst::Plugin::ConfigLoader> and
186 L<Config::Any>). If you are using a version of
187 Catalyst::Devel prior to 1.06, you can convert to the newer format by
188 simply creating the C<myapp.conf> file manually and deleting
189 C<myapp.yml>. The default contents of the C<myapp.conf> you create
190 should only consist of one line:
194 B<TIP>: This script can be useful for converting between configuration
197 perl -Ilib -e 'use MyApp; use Config::General;
198 Config::General->new->save_file("myapp.conf", MyApp->config);'
202 L<Catalyst::Plugin::Static::Simple>
204 C<Static::Simple> provides an easy way to serve static content, such as
205 images and CSS files, from the development server.
209 For our application, we want to add one new plugin to the mix. To do
210 this, edit C<lib/MyApp.pm> (this file is generally referred to as your
211 I<application class>) and delete the lines with:
219 Then replace it with:
230 B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
231 techniques to load these plugins/flags. For example, you might see the
234 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
236 Don't let these variations confuse you -- they all accomplish the same
239 This tells Catalyst to start using one additional plugin,
240 L<Catalyst::Plugin::StackTrace>, to add a stack trace near the top of
241 the standard Catalyst "debug screen" (the screen Catalyst sends to your
242 browser when an error occurs). Be aware that
243 L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
244 browser, not in the console window from which you're running your
245 application, which is where logging output usually goes.
247 Make sure when adding new plugins you also include them as a new
248 dependency within the Makefile.PL file. For example, after adding the
249 StackTrace plugin the Makefile.PL should include the following line:
251 requires 'Catalyst::Plugin::StackTrace';
260 C<__PACKAGE__> is just a shorthand way of referencing the name of the
261 package where it is used. Therefore, in C<MyApp.pm>, C<__PACKAGE__> is
262 equivalent to C<MyApp>.
266 You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
267 before you put your application into production, but it can be helpful
272 When specifying plugins, you can omit C<Catalyst::Plugin::> from the
273 name. Additionally, you can spread the plugin names across multiple
274 lines as shown here or place them all on one line.
278 If you want to see what the StackTrace error screen looks like, edit
279 C<lib/MyApp/Controller/Root.pm> and put a C<die "Oops";> command in the
280 C<sub index :Path :Args(0)> method. Then start the development server
281 and open C<http://localhost:3000/> in your browser. You should get a
282 screen that starts with "Caught exception in
283 MyApp::Controller::Root->index" with sections showing a stacktrace,
284 information about the Request and Response objects, the stash (something
285 we will learn about soon), and the applications configuration.
286 B<Just don't forget to remove the die before you continue the tutorial!>
292 =head1 CREATE A CATALYST CONTROLLER
294 As discussed earlier, controllers are where you write methods that
295 interact with user input. Typically, controller methods respond to
296 C<GET> and C<POST> requests from the user's web browser.
298 Use the Catalyst C<create> script to add a controller for book-related
301 $ script/myapp_create.pl controller Books
302 exists "/home/catalyst/MyApp/script/../lib/MyApp/Controller"
303 exists "/home/catalyst/MyApp/script/../t"
304 created "/home/catalyst/MyApp/script/../lib/MyApp/Controller/Books.pm"
305 created "/home/catalyst/MyApp/script/../t/controller_Books.t"
307 Then edit C<lib/MyApp/Controller/Books.pm> (as discussed in
308 L<Chapter 2|Catalyst::Manual::Tutorial::02_CatalystBasics> of
309 the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
310 each of the three parts of MVC: C<Model>, C<View> and C<Controller>)
311 and add the following method to the controller:
315 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
320 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
321 # 'Context' that's used to 'glue together' the various components
322 # that make up the application
325 # Retrieve all of the book records as book model objects and store in the
326 # stash where they can be accessed by the TT template
327 # $c->stash(books => [$c->model('DB::Book')->all]);
328 # But, for now, use this code until we create the model later
329 $c->stash(books => '');
331 # Set the TT template to use. You will almost always want to do this
332 # in your action methods (action methods respond to user input in
334 $c->stash(template => 'books/list.tt2');
337 B<TIP>: See L<Appendix 1|Catalyst::Manual::Tutorial::10_Appendices> for
338 tips on removing the leading spaces when cutting and pasting example
339 code from POD-based documents.
341 Programmers experienced with object-oriented Perl should recognize
342 C<$self> as a reference to the object where this method was called. On
343 the other hand, C<$c> will be new to many Perl programmers who have not
344 used Catalyst before. This is the "Catalyst Context object", and it is
345 automatically passed as the second argument to all Catalyst action
346 methods. It is used to pass information between components and provide
347 access to Catalyst and plugin functionality.
349 Catalyst Controller actions are regular Perl methods, but they make use
350 of attributes (the "C<:Local>" next to the "C<sub list>" in the code
351 above) to provide additional information to the Catalyst dispatcher
352 logic (note that there can be an optional space between the colon and
353 the attribute name; you will see attributes written both ways). Most
354 Catalyst Controllers use one of five action types:
360 B<:Private> -- Use C<:Private> for methods that you want to make into an
361 action, but you do not want Catalyst to directly expose the method to
362 your users. Catalyst will not map C<:Private> methods to a URI. Use
363 them for various sorts of "special" methods (the C<begin>, C<auto>, etc.
364 discussed below) or for methods you want to be able to C<forward> or
365 C<detach> to. (If the method is a "plain old method" that you
366 don't want to be an action at all, then just define the method without
367 any attribute -- you can call it in your code, but the Catalyst
368 dispatcher will ignore it. You will also have to manually include
369 C<$c> if you want access to the context object in the method vs. having
370 Catalyst automatically include C<$c> in the argument list for you
371 if it's a full-fledged action.)
373 There are five types of "special" built-in C<:Private> actions:
374 C<begin>, C<end>, C<default>, C<index>, and C<auto>.
380 With C<begin>, C<end>, C<default>, C<index> private actions, only the
381 most specific action of each type will be called. For example, if you
382 define a C<begin> action in your controller it will I<override> a
383 C<begin> action in your application/root controller -- I<only> the
384 action in your controller will be called.
388 Unlike the other actions where only a single method is called for each
389 request, I<every> auto action along the chain of namespaces will be
390 called. Each C<auto> action will be called I<from the application/root
391 controller down through the most specific class>.
397 B<:Path> -- C<:Path> actions let you map a method to an explicit URI
398 path. For example, "C<:Path('list')>" in
399 C<lib/MyApp/Controller/Books.pm> would match on the URL
400 C<http://localhost:3000/books/list>, but "C<:Path('/list')>" would match
401 on C<http://localhost:3000/list> (because of the leading slash). You
402 can use C<:Args()> to specify how many arguments an action should
403 accept. See L<Catalyst::Manual::Intro/Action-types> for more
404 information and examples.
408 B<:Local> -- C<:Local> is merely a shorthand for
409 "C<:Path('_name_of_method_')>". For example, these are equivalent:
410 "C<sub create_book :Local {...}>" and
411 "C<sub create_book :Path('create_book') {...}>".
415 B<:Global> -- C<:Global> is merely a shorthand for
416 "C<:Path('/_name_of_method_')>". For example, these are equivalent:
417 "C<sub create_book :Global {...}>" and "C<sub create_book
418 :Path('/create_book') {...}>".
422 B<:Chained> -- Newer Catalyst applications tend to use the Chained
423 dispatch form of action types because of its power and flexibility. It
424 allows a series of controller methods to be automatically dispatched
425 when servicing a single user request. See
426 L<Catalyst::Manual::Tutorial::04_BasicCRUD> and
427 L<Catalyst::DispatchType::Chained> for more information on chained
432 You should refer to L<Catalyst::Manual::Intro/Action-types> for
433 additional information and for coverage of some lesser-used action types
434 not discussed here (C<Regex> and C<LocalRegex>).
437 =head1 CATALYST VIEWS
439 As mentioned in L<Chapter 2|Catalyst::Manual::Tutorial::02_CatalystBasics>
440 of the tutorial, views are where you render output, typically for
441 display in the user's web browser (but can generate other types of
442 output such as PDF or JSON). The code in C<lib/MyApp/View> selects the
443 I<type> of view to use, with the actual rendering template found in the
444 C<root> directory. As with virtually every aspect of Catalyst, options
445 abound when it comes to the specific view technology you adopt inside
446 your application. However, most Catalyst applications use the Template
447 Toolkit, known as TT (for more information on TT, see
448 L<http://www.template-toolkit.org>). Other somewhat popular view
449 technologies include Mason (L<http://www.masonhq.com> and
450 L<http://www.masonbook.com>) and L<HTML::Template>
451 (L<http://html-template.sourceforge.net>).
454 =head2 Create a Catalyst View
456 When using TT for the Catalyst view, the main helper script is
457 L<Catalyst::Helper::View::TT>. You may also come across references to
458 L<Catalyst::Helper::View::TTSite>, but its use is now deprecated.
460 For our book application, enter the following command to enable the
461 C<TT> style of view rendering:
463 $ script/myapp_create.pl view HTML TT
464 exists "/home/catalyst/MyApp/script/../lib/MyApp/View"
465 exists "/home/catalyst/MyApp/script/../t"
466 created "/home/catalyst/MyApp/script/../lib/MyApp/View/HTML.pm"
467 created "/home/catalyst/MyApp/script/../t/view_HTML.t"
469 This creates a view called C<HTML> (the first argument) in a file called
470 C<HTML.pm> that uses L<Catalyst::View::TT> (the second argument) as the
473 It is now up to you to decide how you want to structure your view
474 layout. For the tutorial, we will start with a very simple TT template
475 to initially demonstrate the concepts, but quickly migrate to a more
476 typical "wrapper page" type of configuration (where the "wrapper"
477 controls the overall "look and feel" of your site from a single file or
480 Edit C<lib/MyApp/View/HTML.pm> and you should see something similar to
484 TEMPLATE_EXTENSION => '.tt',
488 And update it to match:
491 # Change default TT extension
492 TEMPLATE_EXTENSION => '.tt2',
496 This changes the default extension for Template Toolkit from '.tt' to
499 You can also configure components in your application class. For
500 example, Edit C<lib/MyApp.pm> and you should see the default
501 configuration above the call to C<_PACKAGE__-E<gt>setup> (your defaults
502 could be different depending on the version of Catalyst you are using):
506 # Disable deprecated behavior needed by old applications
507 disable_component_resolution_regex_fallback => 1,
511 Change this to match the following (insert a new
512 C<__PACKAGE__-E<gt>config> below the existing statement):
516 # Disable deprecated behavior needed by old applications
517 disable_component_resolution_regex_fallback => 1,
522 #Set the location for TT files
524 __PACKAGE__->path_to( 'root', 'src' ),
529 This changes the base directory for your template files from C<root> to
532 Please stick with the settings above for the duration of the tutorial,
533 but feel free to use whatever options you desire in your applications
534 (as with most things in Perl, there's more than one way to do it...).
536 B<Note:> We will use C<root/src> as the base directory for our template
537 files, with a full naming convention of
538 C<root/src/_controller_name_/_action_name_.tt2>. Another popular option
539 is to use C<root/> as the base (with a full filename pattern of
540 C<root/_controller_name_/_action_name_.tt2>).
543 =head2 Create a TT Template Page
545 First create a directory for book-related TT templates:
547 $ mkdir -p root/src/books
549 Then create C<root/src/books/list.tt2> in your editor and enter:
551 [% # This is a TT comment. -%]
553 [%- # Provide a title -%]
554 [% META title = 'Book List' -%]
556 [% # Note That the '-' at the beginning or end of TT code -%]
557 [% # "chomps" the whitespace/newline at that end of the -%]
558 [% # output (use View Source in browser to see the effect) -%]
560 [% # Some basic HTML with a loop to display books -%]
562 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
563 [% # Display each book in a table row %]
564 [% FOREACH book IN books -%]
566 <td>[% book.title %]</td>
567 <td>[% book.rating %]</td>
573 As indicated by the inline comments above, the C<META title> line uses
574 TT's META feature to provide a title to the "wrapper" that we will
575 create later (and essentially does nothing at the moment). Meanwhile,
576 the C<FOREACH> loop iterates through each C<book> model object and
577 prints the C<title> and C<rating> fields.
579 The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
580 supports a wide variety of directives for "calling" other files,
581 looping, conditional logic, etc. In general, TT simplifies the usual
582 range of Perl operators down to the single dot (".") operator. This
583 applies to operations as diverse as method calls, hash lookups, and list
584 index values (see L<Template::Manual::Variables> for details and
585 examples). In addition to the usual L<Template::Toolkit> module Pod
586 documentation, you can access the TT manual at
587 L<https://metacpan.org/module/Template::Manual>.
589 B<TIP:> While you can build all sorts of complex logic into your TT
590 templates, you should in general keep the "code" part of your templates
591 as simple as possible. If you need more complex logic, create helper
592 methods in your model that abstract out a set of code into a single call
593 from your TT template. (Note that the same is true of your controller
594 logic as well -- complex sections of code in your controllers should
595 often be pulled out and placed into your model objects.) In
596 L<Chapter 4|Catalyst::Manual::Tutorial::04_BasicCRUD> of the tutorial we
597 will explore some extremely helpful and powerful features of
598 L<DBIx::Class> that allow you to pull code out of your views and
599 controllers and place it where it rightfully belongs in a model class.
602 =head2 Test Run The Application
604 To test your work so far, first start the development server:
606 $ script/myapp_server.pl -r
608 Then point your browser to L<http://localhost:3000> and you should still
609 get the Catalyst welcome page. Next, change the URL in your browser to
610 L<http://localhost:3000/books/list>. If you have everything working so
611 far, you should see a web page that displays nothing other than our
612 column headers for "Title", "Rating", and "Author(s)" -- we will not see
613 any books until we get the database and model working below.
615 If you run into problems getting your application to run correctly, it
616 might be helpful to refer to some of the debugging techniques covered in
617 the L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> chapter of the
621 =head1 CREATE A SQLITE DATABASE
623 In this step, we make a text file with the required SQL commands to
624 create a database table and load some sample data. We will use SQLite
625 (L<http://www.sqlite.org>), a popular database that is lightweight and
626 easy to use. Be sure to get at least version 3. Open C<myapp01.sql> in
627 your editor and enter:
630 -- Create a very simple database to hold book and author information
632 PRAGMA foreign_keys = ON;
634 id INTEGER PRIMARY KEY,
638 -- 'book_author' is a many-to-many join table between books & authors
639 CREATE TABLE book_author (
640 book_id INTEGER REFERENCES book(id) ON DELETE CASCADE ON UPDATE CASCADE,
641 author_id INTEGER REFERENCES author(id) ON DELETE CASCADE ON UPDATE CASCADE,
642 PRIMARY KEY (book_id, author_id)
644 CREATE TABLE author (
645 id INTEGER PRIMARY KEY,
650 --- Load some sample data
652 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
653 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
654 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
655 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
656 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
657 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
658 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
659 INSERT INTO author VALUES (3, 'Christian', 'Degu');
660 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
661 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
662 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
663 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
664 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
665 INSERT INTO book_author VALUES (1, 1);
666 INSERT INTO book_author VALUES (1, 2);
667 INSERT INTO book_author VALUES (1, 3);
668 INSERT INTO book_author VALUES (2, 4);
669 INSERT INTO book_author VALUES (3, 5);
670 INSERT INTO book_author VALUES (4, 6);
671 INSERT INTO book_author VALUES (4, 7);
672 INSERT INTO book_author VALUES (5, 8);
674 Then use the following command to build a C<myapp.db> SQLite database:
676 $ sqlite3 myapp.db < myapp01.sql
678 If you need to create the database more than once, you probably want to
679 issue the C<rm myapp.db> command to delete the database before you use
680 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
682 Once the C<myapp.db> database file has been created and initialized, you
683 can use the SQLite command line environment to do a quick dump of the
688 Enter ".help" for instructions
689 Enter SQL statements terminated with a ";"
690 sqlite> select * from book;
691 1|CCSP SNRS Exam Certification Guide|5
692 2|TCP/IP Illustrated, Volume 1|5
693 3|Internetworking with TCP/IP Vol.1|4
695 5|Designing with Web Standards|5
701 $ sqlite3 myapp.db "select * from book"
702 1|CCSP SNRS Exam Certification Guide|5
703 2|TCP/IP Illustrated, Volume 1|5
704 3|Internetworking with TCP/IP Vol.1|4
706 5|Designing with Web Standards|5
708 As with most other SQL tools, if you are using the full "interactive"
709 environment you need to terminate your SQL commands with a ";" (it's not
710 required if you do a single SQL statement on the command line). Use
711 ".q" to exit from SQLite from the SQLite interactive mode and return to
712 your OS command prompt.
714 Please note that here we have chosen to use 'singular' table names. This
715 is because the default inflection code for older versions of
716 L<DBIx::Class::Schema::Loader> does NOT handle plurals. There has been
717 much philosophical discussion on whether table names should be plural or
718 singular. There is no one correct answer, as long as one makes a choice
719 and remains consistent with it. If you prefer plural table names (e.g.
720 you think that they are easier to read) then see the documentation in
721 L<DBIx::Class::Schema::Loader::Base/naming> (version 0.05 or greater).
723 For using other databases, such as PostgreSQL or MySQL, see
724 L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices>.
727 =head1 DATABASE ACCESS WITH DBIx::Class
729 Catalyst can be used with virtually any form of datastore available via
730 Perl. For example, L<Catalyst::Model::DBI> can be used to access
731 databases through the traditional Perl L<DBI> interface or you can use a
732 model to access files of any type on the filesystem. However, most
733 Catalyst applications use some form of object-relational mapping (ORM)
734 technology to create objects associated with tables in a relational
735 database, and Matt Trout's L<DBIx::Class> (abbreviated as "DBIC") is the
736 usual choice (this tutorial will use L<DBIx::Class>).
738 Although DBIx::Class has included support for a C<create=dynamic> mode
739 to automatically read the database structure every time the application
740 starts, its use is no longer recommended. While it can make for
741 "flashy" demos, the use of the C<create=static> mode we use below can be
742 implemented just as quickly and provides many advantages (such as the
743 ability to add your own methods to the overall DBIC framework, a
744 technique that we see in
745 L<Chapter 4|Catalyst::Manual::Tutorial::04_BasicCRUD>).
748 =head2 Create Static DBIx::Class Schema Files
750 B<Note:> If you are not following along in the Tutorial Virtual Machine,
751 please be sure that you have version 1.27 or higher of DBD::SQLite and
752 version 0.39 or higher of Catalyst::Model::DBIC::Schema. (The Tutorial
753 VM already has versions that are known to work.) You can get your
754 currently installed version numbers with the following commands.
756 $ perl -MCatalyst::Model::DBIC::Schema\ 999
757 $ perl -MDBD::SQLite\ 999
759 Before you continue, make sure your C<myapp.db> database file is in the
760 application's topmost directory. Now use the model helper with the
761 C<create=static> option to read the database with
762 L<DBIx::Class::Schema::Loader> and
763 automatically build the required files for us:
765 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
766 create=static dbi:SQLite:myapp.db \
767 on_connect_do="PRAGMA foreign_keys = ON"
768 exists "/home/catalyst/MyApp/script/../lib/MyApp/Model"
769 exists "/home/catalyst/MyApp/script/../t"
770 Dumping manual schema for MyApp::Schema to directory /home/catalyst/MyApp/script/../lib ...
771 Schema dump completed.
772 created "/home/catalyst/MyApp/script/../lib/MyApp/Model/DB.pm"
773 created "/home/catalyst/MyApp/script/../t/model_DB.t"
775 Please note the '\' above. Depending on your environment, you might be
776 able to cut and paste the text as shown or need to remove the '\'
777 character to that the command is all on a single line.
779 The C<script/myapp_create.pl> command breaks down like this:
785 C<DB> is the name of the model class to be created by the helper in
786 the C<lib/MyApp/Model> directory.
790 C<DBIC::Schema> is the type of the model to create. This equates to
791 L<Catalyst::Model::DBIC::Schema>, the standard way to use a DBIC-based
792 model inside of Catalyst.
796 C<MyApp::Schema> is the name of the DBIC schema file written to
797 C<lib/MyApp/Schema.pm>.
801 C<create=static> causes L<DBIx::Class::Schema::Loader> to load the
802 schema as it runs and then write that information out into
803 C<lib/MyApp/Schema.pm> and files under the C<lib/MyApp/Schema>
808 C<dbi:SQLite:myapp.db> is the standard DBI connect string for use with
813 And finally, the C<on_connect_do> string requests that
814 L<DBIx::Class::Schema::Loader> create
815 foreign key relationships for us (this is not needed for databases such
816 as PostgreSQL and MySQL, but is required for SQLite). If you take a look
817 at C<lib/MyApp/Model/DB.pm>, you will see that the SQLite pragma is
818 propagated to the Model, so that SQLite's recent (and optional) foreign
819 key enforcement is enabled at the start of every database connection.
824 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
825 only contains a call to the C<load_namespaces> method. You will also
826 find that C<lib/MyApp> contains a C<Schema> subdirectory, which then has
827 a subdirectory called "Result". This "Result" subdirectory then has
828 files named according to each of the tables in our simple database
829 (C<Author.pm>, C<BookAuthor.pm>, and C<Book.pm>). These three files are
830 called "Result Classes" (or
831 "L<ResultSource Classes|DBIx::Class::ResultSource>") in DBIx::Class
832 nomenclature. Although the Result Class files are named after tables in
833 our database, the classes correspond to the I<row-level data> that is
834 returned by DBIC (more on this later, especially in
835 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
837 The idea with the Result Source files created under
838 C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
839 edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
840 warning. If you place all of your changes below that point in the file,
841 you can regenerate the automatically created information at the top of
842 each file should your database structure get updated.
844 Also note the "flow" of the model information across the various files
845 and directories. Catalyst will initially load the model from
846 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
847 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the call
848 to C<load_namespaces> in C<Schema.pm> will load each of the "Result
849 Class" files from the C<lib/MyApp/Schema/Result> subdirectory. The
850 final outcome is that Catalyst will dynamically create three
851 table-specific Catalyst models every time the application starts (you
852 can see these three model files listed in the debug output generated
853 when you launch the application).
855 Additionally, the C<lib/MyApp/Schema.pm> model can easily be loaded
856 outside of Catalyst, for example, in command-line utilities and/or cron
857 jobs. C<lib/MyApp/Model/DB.pm> provides a very thin "bridge" between
858 Catalyst and this external database model. Once you see how we can
859 add some powerful features to our DBIC model in
860 L<Chapter 4|Catalyst::Manual::Tutorial::04_BasicCRUD>, the elegance
861 of this approach will start to become more obvious.
863 B<NOTE:> Older versions of
864 L<Catalyst::Model::DBIC::Schema> use the
865 deprecated DBIx::Class C<load_classes> technique instead of the newer
866 C<load_namespaces>. For new applications, please try to use
867 C<load_namespaces> since it more easily supports a very useful DBIC
868 technique called "ResultSet Classes." If you need to convert an
869 existing application from "load_classes" to "load_namespaces," you can
870 use this process to automate the migration, but first make sure you have
871 version C<0.39> of L<Catalyst::Model::DBIC::Schema> and
872 L<DBIx::Class::Schema::Loader> version C<0.05000> or later.
874 $ # Re-run the helper to upgrade for you
875 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
876 create=static naming=current use_namespaces=1 \
877 dbi:SQLite:myapp.db \
878 on_connect_do="PRAGMA foreign_keys = ON"
881 =head1 ENABLE THE MODEL IN THE CONTROLLER
883 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
884 left disabled earlier so that your version matches the following
885 (un-comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
886 and delete the next 2 lines):
890 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
895 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
896 # 'Context' that's used to 'glue together' the various components
897 # that make up the application
900 # Retrieve all of the book records as book model objects and store
901 # in the stash where they can be accessed by the TT template
902 $c->stash(books => [$c->model('DB::Book')->all]);
904 # Set the TT template to use. You will almost always want to do this
905 # in your action methods (action methods respond to user input in
907 $c->stash(template => 'books/list.tt2');
910 B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented above
911 written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The two are
912 equivalent. Either way, C<$c-E<gt>model> returns a
913 L<DBIx::Class::ResultSet> which handles queries
914 against the database and iterating over the set of results that is
917 We are using the C<-E<gt>all> to fetch all of the books. DBIC supports
918 a wide variety of more advanced operations to easily do things like
919 filtering and sorting the results. For example, the following could be
920 used to sort the results by descending title:
922 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
924 Some other examples are provided in
925 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with additional
926 information found at L<DBIx::Class::ResultSet/search>,
927 L<DBIx::Class::Manual::FAQ/Searching>, L<DBIx::Class::Manual::Intro> and
928 L<Catalyst::Model::DBIC::Schema>.
931 =head2 Test Run The Application
933 First, let's enable an environment variable that causes L<DBIx::Class>
934 to dump the SQL statements used to access the database. This is a
935 helpful trick when you are trying to debug your database-oriented code.
936 Press C<Ctrl-C> to break out of the development server and enter:
938 $ export DBIC_TRACE=1
939 $ script/myapp_server.pl -r
941 This assumes you are using bash as your shell -- adjust accordingly if
942 you are using a different shell (for example, under tcsh, use
943 C<setenv DBIC_TRACE 1>).
945 B<NOTE:> You can also set this in your code using
946 C<$class-E<gt>storage-E<gt>debug(1);>. See
947 L<DBIx::Class::Manual::Troubleshooting> for details (including options
948 to log to a file instead of displaying to the Catalyst development
951 Then launch the Catalyst development server. The log output should
952 display something like:
954 $ script/myapp_server.pl -r
955 [debug] Debug messages enabled
956 [debug] Statistics enabled
957 [debug] Loaded plugins:
958 .----------------------------------------------------------------------------.
959 | Catalyst::Plugin::ConfigLoader 0.30 |
960 | Catalyst::Plugin::StackTrace 0.11 |
961 '----------------------------------------------------------------------------'
963 [debug] Loaded dispatcher "Catalyst::Dispatcher"
964 [debug] Loaded engine "Catalyst::Engine"
965 [debug] Found home "/home/catalyst/MyApp"
966 [debug] Loaded Config "/home/catalyst/MyApp/myapp.conf"
967 [debug] Loaded components:
968 .-----------------------------------------------------------------+----------.
970 +-----------------------------------------------------------------+----------+
971 | MyApp::Controller::Books | instance |
972 | MyApp::Controller::Root | instance |
973 | MyApp::Model::DB | instance |
974 | MyApp::Model::DB::Author | class |
975 | MyApp::Model::DB::Book | class |
976 | MyApp::Model::DB::BookAuthor | class |
977 | MyApp::View::HTML | instance |
978 '-----------------------------------------------------------------+----------'
980 [debug] Loaded Private actions:
981 .----------------------+--------------------------------------+--------------.
982 | Private | Class | Method |
983 +----------------------+--------------------------------------+--------------+
984 | /default | MyApp::Controller::Root | default |
985 | /end | MyApp::Controller::Root | end |
986 | /index | MyApp::Controller::Root | index |
987 | /books/index | MyApp::Controller::Books | index |
988 | /books/list | MyApp::Controller::Books | list |
989 '----------------------+--------------------------------------+--------------'
991 [debug] Loaded Path actions:
992 .-------------------------------------+--------------------------------------.
994 +-------------------------------------+--------------------------------------+
997 | /books | /books/index |
998 | /books/list | /books/list |
999 '-------------------------------------+--------------------------------------'
1001 [info] MyApp powered by Catalyst 5.80020
1002 HTTP::Server::PSGI: Accepting connections at http://0:3000
1004 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from the
1005 'base' directory of your application, not inside the C<script> directory
1006 itself or it will not be able to locate the C<myapp.db> database file.
1007 You can use a fully qualified or a relative path to locate the database
1008 file, but we did not specify that when we ran the model helper earlier.
1010 Some things you should note in the output above:
1016 L<Catalyst::Model::DBIC::Schema> dynamically created three model
1017 classes, one to represent each of the three tables in our database
1018 (C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>, and
1019 C<MyApp::Model::DB::Book>).
1023 The "list" action in our Books controller showed up with a path of
1028 Point your browser to L<http://localhost:3000> and you should still get
1029 the Catalyst welcome page.
1031 Next, to view the book list, change the URL in your browser to
1032 L<http://localhost:3000/books/list>. You should get a list of the five
1033 books loaded by the C<myapp01.sql> script above without any formatting.
1034 The rating for each book should appear on each row, but the "Author(s)"
1035 column will still be blank (we will fill that in later).
1037 Also notice in the output of the C<script/myapp_server.pl> that
1038 L<DBIx::Class> used the following SQL to retrieve the data:
1040 SELECT me.id, me.title, me.rating FROM book me
1042 because we enabled DBIC_TRACE.
1044 You now have the beginnings of a simple but workable web application.
1045 Continue on to future sections and we will develop the application more
1049 =head1 CREATE A WRAPPER FOR THE VIEW
1051 When using TT, you can (and should) create a wrapper that will literally
1052 wrap content around each of your templates. This is certainly useful as
1053 you have one main source for changing things that will appear across
1054 your entire site/application instead of having to edit many individual
1058 =head2 Configure HTML.pm For The Wrapper
1060 In order to create a wrapper, you must first edit your TT view and tell
1061 it where to find your wrapper file.
1063 Edit your TT view in C<lib/MyApp/View/HTML.pm> and change it to match
1066 __PACKAGE__->config(
1067 # Change default TT extension
1068 TEMPLATE_EXTENSION => '.tt2',
1069 # Set the location for TT files
1071 MyApp->path_to( 'root', 'src' ),
1073 # Set to 1 for detailed timer stats in your HTML as comments
1075 # This is your wrapper template located in the 'root/src'
1076 WRAPPER => 'wrapper.tt2',
1080 =head2 Create the Wrapper Template File and Stylesheet
1082 Next you need to set up your wrapper template. Basically, you'll want
1083 to take the overall layout of your site and put it into this file. For
1084 the tutorial, open C<root/src/wrapper.tt2> and input the following:
1086 <?xml version="1.0" encoding="UTF-8"?>
1087 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" [%#
1088 %]"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1089 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
1091 <title>[% template.title or "My Catalyst App!" %]</title>
1092 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1098 [%# Your logo could go here -%]
1099 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1100 [%# Insert the page title -%]
1101 <h1>[% template.title or site.title %]</h1>
1104 <div id="bodyblock">
1108 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1109 <li><a href="[% c.uri_for('/')
1110 %]" title="Catalyst Welcome Page">Welcome</a></li>
1112 </div><!-- end menu -->
1115 [%# Status and error messages %]
1116 <span class="message">[% status_msg %]</span>
1117 <span class="error">[% error_msg %]</span>
1118 [%# This is where TT will stick all of your template's contents. -%]
1120 </div><!-- end content -->
1121 </div><!-- end bodyblock -->
1123 <div id="footer">Copyright (c) your name goes here</div>
1124 </div><!-- end outer -->
1129 Notice the status and error message sections in the code above:
1131 <span class="status">[% status_msg %]</span>
1132 <span class="error">[% error_msg %]</span>
1134 If we set either message in the Catalyst stash (e.g.,
1135 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it will
1136 be displayed whenever any view used by that request is rendered. The
1137 C<message> and C<error> CSS styles can be customized to suit your needs
1138 in the C<root/static/css/main.css> file we create below.
1146 The Catalyst stash only lasts for a single HTTP request. If you need to
1147 retain information across requests you can use
1148 L<Catalyst::Plugin::Session> (we will use Catalyst sessions in the
1149 Authentication chapter of the tutorial).
1153 Although it is beyond the scope of this tutorial, you may wish to use a
1154 JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
1155 Dojo (L<http://www.dojotoolkit.org>).
1160 =head3 Create A Basic Stylesheet
1162 First create a central location for stylesheets under the static
1165 $ mkdir root/static/css
1167 Then open the file C<root/static/css/main.css> (the file referenced in
1168 the stylesheet href link of our wrapper above) and add the following
1187 background-color: #ddd;
1193 padding: 0 0 50% 5px;
1194 font-weight: normal;
1195 background-color: #ddd;
1208 You may wish to check out a "CSS Framework" like Emastic
1209 (L<http://code.google.com/p/emastic/>) as a way to quickly provide lots
1210 of high-quality CSS functionality.
1213 =head2 Test Run The Application
1215 Hit "Reload" in your web browser and you should now see a formatted
1216 version of our basic book list. (Again, the development server should
1217 have automatically restarted when you made changes to
1218 C<lib/MyApp/View/HTML.pm>. If you are not using the "-r" option, you
1219 will need to hit C<Ctrl-C> and manually restart it. Also note that the
1220 development server does I<NOT> need to restart for changes to the TT and
1221 static files we created and edited in the C<root> directory -- those
1222 updates are handled on a per-request basis.)
1224 Although our wrapper and stylesheet are obviously very simple, you
1225 should see how it allows us to control the overall look of an entire
1226 website from two central files. To add new pages to the site, just
1227 provide a template that fills in the C<content> section of our wrapper
1228 template -- the wrapper will provide the overall feel of the page.
1231 =head2 Updating the Generated DBIx::Class Result Class Files
1233 If you take a look at the Schema files automatically generated by
1234 L<DBIx::Class::Schema::Loader>, you will see that it has already defined
1235 C<has_many> and C<belongs_to> relationships on each side of our foreign
1236 keys. For example, take a look at C<lib/MyApp/Schema/Result/Book.pm> and
1237 notice the following code:
1245 Related object: L<MyApp::Schema::Result::BookAuthor>
1249 __PACKAGE__->has_many(
1251 "MyApp::Schema::Result::BookAuthor",
1252 { "foreign.book_id" => "self.id" },
1253 { cascade_copy => 0, cascade_delete => 0 },
1256 Each C<Book> "has_many" C<book_authors>, where C<BookAuthor> is the
1257 many-to-many table that allows each Book to have multiple Authors, and
1258 each Author to have multiple books. The arguments to C<has_many> are:
1264 C<book_authors> - The name for this relationship. DBIC will create an
1265 accessor on the C<Books> DBIC Row object with this name.
1269 C<MyApp::Schema::Result::BookAuthor> - The name of the DBIC model class
1270 referenced by this C<has_many> relationship.
1274 C<foreign.book_id> - C<book_id> is the name of the foreign key column in
1275 the I<foreign> table that points back to this table.
1279 C<self.id> - C<id> is the name of the column in I<this> table that is
1280 referenced by the foreign key.
1284 See L<DBIx::Class::Relationship/has_many> for additional information.
1285 Note that you might see a "hand coded" version of the C<has_many>
1286 relationship above expressed as:
1288 __PACKAGE__->has_many(
1290 "MyApp::Schema::Result::BookAuthor",
1294 Where the third argument is simply the name of the column in the foreign
1295 table. However, the hashref syntax used by
1296 L<DBIx::Class::Schema::Loader> is more flexible (for example, it can
1297 handle "multi-column foreign keys").
1299 B<Note:> If you are using older versions of SQLite and related DBIC
1300 tools, you will need to manually define your C<has_many> and
1301 C<belongs_to> relationships. We recommend upgrading to the versions
1302 specified above. :-)
1304 Have a look at C<lib/MyApp/Schema/Result/BookAuthor.pm> and notice that
1305 there is a C<belongs_to> relationship defined that acts as the "mirror
1306 image" to the C<has_many> relationship we just looked at above:
1314 Related object: L<MyApp::Schema::Result::Book>
1318 __PACKAGE__->belongs_to(
1320 "MyApp::Schema::Result::Book",
1321 { id => "book_id" },
1322 { join_type => "LEFT", on_delete => "CASCADE", on_update => "CASCADE" },
1325 The arguments are similar, but see
1326 L<DBIx::Class::Relationship/belongs_to> for the details.
1328 Although recent versions of SQLite and L<DBIx::Class::Schema::Loader>
1329 automatically handle the C<has_many> and C<belongs_to> relationships,
1330 C<many_to_many> relationship bridges (not technically a relationship)
1331 currently need to be manually inserted. To add a C<many_to_many>
1332 relationship bridge, first edit C<lib/MyApp/Schema/Result/Book.pm> and
1333 add the following text below the C<# You can replace this text...>
1338 # 1) Name of relationship bridge, DBIC will create accessor with this name
1339 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1340 # 3) Name of belongs_to() relationship in model class of has_many() above
1341 # You must already have the has_many() defined to use a many_to_many().
1342 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1344 B<Note:> Be careful to put this code I<above> the C<1;> at the end of
1345 the file. As with any Perl package, we need to end the last line with a
1346 statement that evaluates to C<true>. This is customarily done with
1347 C<1;> on a line by itself.
1349 The C<many_to_many> relationship bridge is optional, but it makes it
1350 easier to map a book to its collection of authors. Without it, we would
1351 have to "walk" through the C<book_author> table as in
1352 C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we will
1353 see examples on how to use DBIx::Class objects in your code soon, but
1354 note that because C<$book-E<gt>book_author> can return multiple authors,
1355 we have to use C<first> to display a single author). C<many_to_many>
1356 allows us to use the shorter
1357 C<$book-E<gt>author-E<gt>first-E<gt>last_name>. Note that you cannot
1358 define a C<many_to_many> relationship bridge without also having the
1359 C<has_many> relationship in place.
1361 Then edit C<lib/MyApp/Schema/Result/Author.pm> and add the reverse
1362 C<many_to_many> relationship bridge for C<Author> as follows (again, be
1363 careful to put in above the C<1;> but below the C<# DO NOT MODIFY THIS
1364 OR ANYTHING ABOVE!> comment):
1368 # 1) Name of relationship bridge, DBIC will create accessor with this name
1369 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1370 # 3) Name of belongs_to() relationship in model class of has_many() above
1371 # You must already have the has_many() defined to use a many_to_many().
1372 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
1375 =head2 Run The Application
1377 Run the Catalyst development server script with the C<DBIC_TRACE> option
1378 (it might still be enabled from earlier in the tutorial, but here is an
1379 alternate way to specify the trace option just in case):
1381 $ DBIC_TRACE=1 script/myapp_server.pl -r
1383 Make sure that the application loads correctly and that you see the
1384 three dynamically created model classes (one for each of the Result
1385 Classes we created).
1387 Then hit the URL L<http://localhost:3000/books/list> with your browser
1388 and be sure that the book list still displays correctly.
1390 B<Note:> You will not see the authors yet because the view isn't taking
1391 advantage of these relationships. Read on to the next section where we
1392 update the template to do that.
1395 =head1 UPDATING THE VIEW
1397 Let's add a new column to our book list page that takes advantage of the
1398 relationship information we manually added to our schema files in the
1399 previous section. Edit C<root/src/books/list.tt2> and replace the
1400 "empty" table cell "<td></td>" with the following:
1404 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1405 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1406 [% # loop in 'side effect notation' to load just the last names of the -%]
1407 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
1408 [% # a value, so nothing will be printed here. But, if you have something -%]
1409 [% # in TT that does return a value and you don't want it printed, you -%]
1410 [% # 1) assign it to a bogus value, or -%]
1411 [% # 2) use the CALL keyword to call it and discard the return value. -%]
1412 [% tt_authors = [ ];
1413 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1414 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1415 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1416 ([% tt_authors.size | html %])
1417 [% # Use another TT vmethod to join & print the names & comma separators -%]
1418 [% tt_authors.join(', ') | html %]
1422 B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1423 possible out of your views. This kind of logic belongs in your model
1424 (the same goes for controllers -- keep them as "thin" as possible and
1425 push all of the "complicated code" out to your model objects). Avoid
1426 code like you see in the previous example -- we are only using it here
1427 to show some extra features in TT until we get to the more advanced
1428 model features we will see in Chapter 4 (see
1429 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1431 Then hit "Reload" in your browser (note that you don't need to reload
1432 the development server or use the C<-r> option when updating TT
1433 templates) and you should now see the number of authors each book has
1434 along with a comma-separated list of the authors' last names. (If you
1435 didn't leave the development server running from the previous step, you
1436 will obviously need to start it before you can refresh your browser
1439 If you are still running the development server with C<DBIC_TRACE>
1440 enabled, you should also now see five more C<SELECT> statements in the
1441 debug output (one for each book as the authors are being retrieved by
1444 SELECT me.id, me.title, me.rating FROM book me:
1445 SELECT author.id, author.first_name, author.last_name FROM book_author me
1446 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '1'
1447 SELECT author.id, author.first_name, author.last_name FROM book_author me
1448 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '2'
1449 SELECT author.id, author.first_name, author.last_name FROM book_author me
1450 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '3'
1451 SELECT author.id, author.first_name, author.last_name FROM book_author me
1452 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '4'
1453 SELECT author.id, author.first_name, author.last_name FROM book_author me
1454 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '5'
1456 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1457 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1458 and > and avoid various types of dangerous hacks against your
1459 application. In a real application, you would probably want to put "|
1460 html" at the end of every field where a user has control over the
1461 information that can appear in that field (and can therefore inject
1462 markup or code if you don't "neutralize" those fields). In addition to
1463 "| html", Template Toolkit has a variety of other useful filters that
1464 can be found in the documentation for L<Template::Filters>. (While we
1465 are on the topic of security and escaping of dangerous values, one of
1466 the advantages of using tools like DBIC for database access or
1467 L<HTML::FormFu> for form management [see
1468 L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD::09_FormFu>]
1469 is that they automatically handle most escaping for you and therefore
1470 dramatically increase the security of your app.)
1473 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1475 In some situations, it can be useful to run your application and display
1476 a page without using a browser. Catalyst lets you do this using the
1477 C<script/myapp_test.pl> script. Just supply the URL you wish to
1478 display and it will run that request through the normal controller
1479 dispatch logic and use the appropriate view to render the output
1480 (obviously, complex pages may dump a lot of text to your terminal
1481 window). For example, if C<Ctrl+C> out of the development server
1484 $ script/myapp_test.pl "/books/list"
1486 You should get the same text as if you visited
1487 L<http://localhost:3000/books/list> with the normal development server
1488 and asked your browser to view the page source. You can even pipe this
1489 HTML text output to a text-based browser using a command like:
1491 $ script/myapp_test.pl "/books/list" | lynx -stdin
1493 And you should see a fully rendered text-based view of your page. (If
1494 you are following along in Debian 6, type
1495 C<sudo aptitude -y install lynx> to install lynx.) If you do start
1496 lynx, you can use the "Q" key to quit.
1499 =head1 OPTIONAL INFORMATION
1501 B<NOTE: The rest of this chapter of the tutorial is optional. You can
1502 skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
1506 =head2 Using 'RenderView' for the Default View
1508 Once your controller logic has processed the request from a user, it
1509 forwards processing to your view in order to generate the appropriate
1510 response output. Catalyst uses
1511 L<Catalyst::Action::RenderView> by default
1512 to automatically perform this operation. If you look in
1513 C<lib/MyApp/Controller/Root.pm>, you should see the empty definition for
1514 the C<sub end> method:
1516 sub end : ActionClass('RenderView') {}
1518 The following bullet points provide a quick overview of the
1519 C<RenderView> process:
1525 C<Root.pm> is designed to hold application-wide logic.
1529 At the end of a given user request, Catalyst will call the most specific
1530 C<end> method that's appropriate. For example, if the controller for a
1531 request has an C<end> method defined, it will be called. However, if
1532 the controller does not define a controller-specific C<end> method, the
1533 "global" C<end> method in C<Root.pm> will be called.
1537 Because the definition includes an C<ActionClass> attribute, the
1538 L<Catalyst::Action::RenderView> logic will be executed B<after> any code
1539 inside the definition of C<sub end> is run. See
1540 L<Catalyst::Manual::Actions> for more information on C<ActionClass>.
1544 Because C<sub end> is empty, this effectively just runs the default
1545 logic in C<RenderView>. However, you can easily extend the
1546 C<RenderView> logic by adding your own code inside the empty method body
1547 (C<{}>) created by the Catalyst Helpers when we first ran the
1548 C<catalyst.pl> to initialize our application. See
1549 L<Catalyst::Action::RenderView> for more
1550 detailed information on how to extend C<RenderView> in C<sub end>.
1555 =head2 RenderView's "dump_info" Feature
1557 One of the nice features of C<RenderView> is that it automatically
1558 allows you to add C<dump_info=1> to the end of any URL for your
1559 application and it will force the display of the "exception dump" screen
1560 to the client browser. You can try this out by pointing your browser to
1563 http://localhost:3000/books/list?dump_info=1
1565 You should get a page with the following message at the top:
1567 Caught exception in MyApp::Controller::Root->end "Forced debug -
1568 Scrubbed output at /usr/share/perl5/Catalyst/Action/RenderView.pm line 46."
1570 Along with a summary of your application's state at the end of the
1571 processing for that request. The "Stash" section should show a
1572 summarized version of the DBIC book model objects. If desired, you can
1573 adjust the summarization logic (called "scrubbing" logic) -- see
1574 L<Catalyst::Action::RenderView> for
1577 Note that you shouldn't need to worry about "normal clients" using this
1578 technique to "reverse engineer" your application -- C<RenderView> only
1579 supports the C<dump_info=1> feature when your application is running in
1580 C<-Debug> mode (something you won't do once you have your application
1581 deployed in production).
1584 =head2 Using The Default Template Name
1586 By default, C<Catalyst::View::TT> will look for a template that uses the
1587 same name as your controller action, allowing you to save the step of
1588 manually specifying the template name in each action. For example, this
1589 would allow us to remove the
1590 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';>
1591 line of our C<list> action in the Books controller.
1592 Open C<lib/MyApp/Controller/Books.pm> in your editor and comment out
1593 this line to match the following (only the
1594 C<$c-E<gt>stash-E<gt>{template}> line has changed):
1598 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1603 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1604 # 'Context' that's used to 'glue together' the various components
1605 # that make up the application
1606 my ($self, $c) = @_;
1608 # Retrieve all of the book records as book model objects and store in the
1609 # stash where they can be accessed by the TT template
1610 $c->stash(books => [$c->model('DB::Book')->all]);
1612 # Set the TT template to use. You will almost always want to do this
1613 # in your action methods (actions methods respond to user input in
1614 # your controllers).
1615 #$c->stash(template => 'books/list.tt2');
1619 You should now be able to access the L<http://localhost:3000/books/list>
1622 B<NOTE:> If you use the default template technique, you
1623 will B<not> be able to use either the C<$c-E<gt>forward> or the
1624 C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1625 Chapter 9 of the Tutorial).
1627 B<IMPORTANT:> Make sure that you do B<not> skip the following section
1628 before continuing to the next chapter 4 Basic CRUD.
1631 =head2 Return To A Manually Specified Template
1633 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1634 later in the tutorial, you should remove the comment from the statement
1635 in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1637 $c->stash(template => 'books/list.tt2');
1639 Then delete the C<TEMPLATE_EXTENSION> line in C<lib/MyApp/View/HTML.pm>.
1641 Check the L<http://localhost:3000/books/list> URL in your browser. It
1642 should look the same manner as with earlier sections.
1645 You can jump to the next chapter of the tutorial here:
1646 L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
1651 Kennedy Clark, C<hkclark@gmail.com>
1653 Feel free to contact the author for any errors or suggestions, but the
1654 best way to report issues is via the CPAN RT Bug system at
1655 L<https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
1657 Copyright 2006-2011, Kennedy Clark, under the
1658 Creative Commons Attribution Share-Alike License Version 3.0
1659 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).