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 F<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 F<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 F<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<Catalyst.pm|Catalyst> 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<< $c->debug >> method on the C<$c> Catalyst context object
150 the C<-d> option on the F<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 F<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). L<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 L<Config::General> style. This tutorial uses the newer
182 C<myapp.conf> file for L<Config::General>. However, Catalyst supports
183 both formats and will automatically use either F<myapp.conf> or
184 F<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 L<Catalyst::Devel> prior to 1.06, you can convert to the newer format by
188 simply creating the F<myapp.conf> file manually and deleting
189 F<myapp.yml>. The default contents of the F<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 F<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 L<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 F<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 F<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 F<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 F<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 $c->stash(template => 'books/list.tt2');
337 B<TIP>: See L<Appendix 1|Catalyst::Manual::Tutorial::10_Appendices/APPENDIX 1: CUT AND PASTE FOR POD-BASED EXAMPLES>
338 for tips on removing the leading spaces when cutting and pasting example
339 code from POD-based documents.
341 Programmers experienced with object-oriented Perl should recognize
342 C<$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 F<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 F<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<https://masonbook.houseabsolute.com/book/>) and L<HTML::Template>.
453 =head2 Create a Catalyst View
455 When using TT for the Catalyst view, the main helper script is
456 L<Catalyst::Helper::View::TT>. You may also come across references to
457 L<Catalyst::Helper::View::TTSite>, but its use is now deprecated.
459 For our book application, enter the following command to enable the
460 C<TT> style of view rendering:
462 $ script/myapp_create.pl view HTML TT
463 exists "/home/catalyst/MyApp/script/../lib/MyApp/View"
464 exists "/home/catalyst/MyApp/script/../t"
465 created "/home/catalyst/MyApp/script/../lib/MyApp/View/HTML.pm"
466 created "/home/catalyst/MyApp/script/../t/view_HTML.t"
468 This creates a view called C<HTML> (the first argument) in a file called
469 C<HTML.pm> that uses L<Catalyst::View::TT> (the second argument) as the
472 It is now up to you to decide how you want to structure your view
473 layout. For the tutorial, we will start with a very simple TT template
474 to initially demonstrate the concepts, but quickly migrate to a more
475 typical "wrapper page" type of configuration (where the "wrapper"
476 controls the overall "look and feel" of your site from a single file or
479 Edit F<lib/MyApp/View/HTML.pm> and you should see something similar to
483 TEMPLATE_EXTENSION => '.tt',
487 And update it to match:
490 # Change default TT extension
491 TEMPLATE_EXTENSION => '.tt2',
495 This changes the default extension for Template Toolkit from '.tt' to
498 You can also configure components in your application class. For
499 example, Edit F<lib/MyApp.pm> and you should see the default
500 configuration above the call to C<< _PACKAGE__->setup >> (your defaults
501 could be different depending on the version of Catalyst you are using):
505 # Disable deprecated behavior needed by old applications
506 disable_component_resolution_regex_fallback => 1,
510 Change this to match the following (insert a new
511 C<< __PACKAGE__->config >> below the existing statement):
515 # Disable deprecated behavior needed by old applications
516 disable_component_resolution_regex_fallback => 1,
521 #Set the location for TT files
523 __PACKAGE__->path_to( 'root', 'src' ),
528 This changes the base directory for your template files from C<root> to
531 Please stick with the settings above for the duration of the tutorial,
532 but feel free to use whatever options you desire in your applications
533 (as with most things in Perl, there's more than one way to do it...).
535 B<Note:> We will use F<root/src> as the base directory for our template
536 files, with a full naming convention of
537 F<root/src/_controller_name_/_action_name_.tt2>. Another popular option
538 is to use F<root/> as the base (with a full filename pattern of
539 F<root/_controller_name_/_action_name_.tt2>).
542 =head2 Create a TT Template Page
544 First create a directory for book-related TT templates:
546 $ mkdir -p root/src/books
548 Then create F<root/src/books/list.tt2> in your editor and enter:
550 [% # This is a TT comment. -%]
552 [%- # Provide a title -%]
553 [% META title = 'Book List' -%]
555 [% # Note That the '-' at the beginning or end of TT code -%]
556 [% # "chomps" the whitespace/newline at that end of the -%]
557 [% # output (use View Source in browser to see the effect) -%]
559 [% # Some basic HTML with a loop to display books -%]
561 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
562 [% # Display each book in a table row %]
563 [% FOREACH book IN books -%]
565 <td>[% book.title %]</td>
566 <td>[% book.rating %]</td>
572 As indicated by the inline comments above, the C<META title> line uses
573 TT's META feature to provide a title to the "wrapper" that we will
574 create later (and essentially does nothing at the moment). Meanwhile,
575 the C<FOREACH> loop iterates through each C<book> model object and
576 prints the C<title> and C<rating> fields.
578 The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
579 supports a wide variety of directives for "calling" other files,
580 looping, conditional logic, etc. In general, TT simplifies the usual
581 range of Perl operators down to the single dot (".") operator. This
582 applies to operations as diverse as method calls, hash lookups, and list
583 index values (see L<Template::Manual::Variables> for details and
584 examples). In addition to the usual L<Template::Toolkit> module Pod
585 documentation, you can access the TT manual at
588 B<TIP:> While you can build all sorts of complex logic into your TT
589 templates, you should in general keep the "code" part of your templates
590 as simple as possible. If you need more complex logic, create helper
591 methods in your model that abstract out a set of code into a single call
592 from your TT template. (Note that the same is true of your controller
593 logic as well -- complex sections of code in your controllers should
594 often be pulled out and placed into your model objects.) In
595 L<Chapter 4|Catalyst::Manual::Tutorial::04_BasicCRUD> of the tutorial we
596 will explore some extremely helpful and powerful features of
597 L<DBIx::Class> that allow you to pull code out of your views and
598 controllers and place it where it rightfully belongs in a model class.
601 =head2 Test Run The Application
603 To test your work so far, first start the development server:
605 $ script/myapp_server.pl -r
607 Then point your browser to L<http://localhost:3000> and you should still
608 get the Catalyst welcome page. Next, change the URL in your browser to
609 L<http://localhost:3000/books/list>. If you have everything working so
610 far, you should see a web page that displays nothing other than our
611 column headers for "Title", "Rating", and "Author(s)" -- we will not see
612 any books until we get the database and model working below.
614 If you run into problems getting your application to run correctly, it
615 might be helpful to refer to some of the debugging techniques covered in
616 the L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> chapter of the
620 =head1 CREATE A SQLITE DATABASE
622 In this step, we make a text file with the required SQL commands to
623 create a database table and load some sample data. We will use SQLite
624 (L<https://www.sqlite.org>), a popular database that is lightweight and
625 easy to use. Be sure to get at least version 3. Open F<myapp01.sql> in
626 your editor and enter:
629 -- Create a very simple database to hold book and author information
631 PRAGMA foreign_keys = ON;
633 id INTEGER PRIMARY KEY,
637 -- 'book_author' is a many-to-many join table between books & authors
638 CREATE TABLE book_author (
639 book_id INTEGER REFERENCES book(id) ON DELETE CASCADE ON UPDATE CASCADE,
640 author_id INTEGER REFERENCES author(id) ON DELETE CASCADE ON UPDATE CASCADE,
641 PRIMARY KEY (book_id, author_id)
643 CREATE TABLE author (
644 id INTEGER PRIMARY KEY,
649 --- Load some sample data
651 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
652 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
653 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
654 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
655 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
656 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
657 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
658 INSERT INTO author VALUES (3, 'Christian', 'Degu');
659 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
660 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
661 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
662 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
663 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
664 INSERT INTO book_author VALUES (1, 1);
665 INSERT INTO book_author VALUES (1, 2);
666 INSERT INTO book_author VALUES (1, 3);
667 INSERT INTO book_author VALUES (2, 4);
668 INSERT INTO book_author VALUES (3, 5);
669 INSERT INTO book_author VALUES (4, 6);
670 INSERT INTO book_author VALUES (4, 7);
671 INSERT INTO book_author VALUES (5, 8);
673 Then use the following command to build a F<myapp.db> SQLite database:
675 $ sqlite3 myapp.db < myapp01.sql
677 If you need to create the database more than once, you probably want to
678 issue the C<rm myapp.db> command to delete the database before you use
679 the C<< sqlite3 myapp.db < myapp01.sql >> command.
681 Once the F<myapp.db> database file has been created and initialized, you
682 can use the SQLite command line environment to do a quick dump of the
687 Enter ".help" for instructions
688 Enter SQL statements terminated with a ";"
689 sqlite> select * from book;
690 1|CCSP SNRS Exam Certification Guide|5
691 2|TCP/IP Illustrated, Volume 1|5
692 3|Internetworking with TCP/IP Vol.1|4
694 5|Designing with Web Standards|5
700 $ sqlite3 myapp.db "select * from book"
701 1|CCSP SNRS Exam Certification Guide|5
702 2|TCP/IP Illustrated, Volume 1|5
703 3|Internetworking with TCP/IP Vol.1|4
705 5|Designing with Web Standards|5
707 As with most other SQL tools, if you are using the full "interactive"
708 environment you need to terminate your SQL commands with a ";" (it's not
709 required if you do a single SQL statement on the command line). Use
710 ".q" to exit from SQLite from the SQLite interactive mode and return to
711 your OS command prompt.
713 Please note that here we have chosen to use 'singular' table names. This
714 is because the default inflection code for older versions of
715 L<DBIx::Class::Schema::Loader> does NOT handle plurals. There has been
716 much philosophical discussion on whether table names should be plural or
717 singular. There is no one correct answer, as long as one makes a choice
718 and remains consistent with it. If you prefer plural table names (e.g.
719 you think that they are easier to read) then see the documentation in
720 L<DBIx::Class::Schema::Loader::Base/naming> (version 0.05 or greater).
722 For using other databases, such as PostgreSQL or MySQL, see
723 L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices/APPENDIX 2: USING POSTGRESQL AND MYSQL>.
726 =head1 DATABASE ACCESS WITH DBIx::Class
728 Catalyst can be used with virtually any form of datastore available via
729 Perl. For example, L<Catalyst::Model::DBI> can be used to access
730 databases through the traditional Perl L<DBI> interface or you can use a
731 model to access files of any type on the filesystem. However, most
732 Catalyst applications use some form of object-relational mapping (ORM)
733 technology to create objects associated with tables in a relational
734 database, and Matt Trout's L<DBIx::Class> (abbreviated as "DBIC") is the
735 usual choice (this tutorial will use L<DBIx::Class>).
737 Although DBIx::Class has included support for a C<create=dynamic> mode
738 to automatically read the database structure every time the application
739 starts, its use is no longer recommended. While it can make for
740 "flashy" demos, the use of the C<create=static> mode we use below can be
741 implemented just as quickly and provides many advantages (such as the
742 ability to add your own methods to the overall DBIC framework, a
743 technique that we see in
744 L<Chapter 4|Catalyst::Manual::Tutorial::04_BasicCRUD>).
747 =head2 Create Static DBIx::Class Schema Files
749 B<Note:> If you are not following along in the Tutorial Virtual Machine,
750 please be sure that you have version 1.27 or higher of L<DBD::SQLite> and
751 version 0.39 or higher of L<Catalyst::Model::DBIC::Schema>. (The Tutorial
752 VM already has versions that are known to work.) You can get your
753 currently installed version numbers with the following commands.
755 $ perl -MCatalyst::Model::DBIC::Schema\ 999
756 $ perl -MDBD::SQLite\ 999
758 Before you continue, make sure your F<myapp.db> database file is in the
759 application's topmost directory. Now use the model helper with the
760 C<create=static> option to read the database with
761 L<DBIx::Class::Schema::Loader> and
762 automatically build the required files for us:
764 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
765 create=static dbi:SQLite:myapp.db \
766 on_connect_do="PRAGMA foreign_keys = ON"
767 exists "/home/catalyst/MyApp/script/../lib/MyApp/Model"
768 exists "/home/catalyst/MyApp/script/../t"
769 Dumping manual schema for MyApp::Schema to directory /home/catalyst/MyApp/script/../lib ...
770 Schema dump completed.
771 created "/home/catalyst/MyApp/script/../lib/MyApp/Model/DB.pm"
772 created "/home/catalyst/MyApp/script/../t/model_DB.t"
774 Please note the '\' above. Depending on your environment, you might be
775 able to cut and paste the text as shown or need to remove the '\'
776 character to that the command is all on a single line.
778 The F<script/myapp_create.pl> command breaks down like this:
784 C<DB> is the name of the model class to be created by the helper in
785 the F<lib/MyApp/Model> directory.
789 C<DBIC::Schema> is the type of the model to create. This equates to
790 L<Catalyst::Model::DBIC::Schema>, the standard way to use a DBIC-based
791 model inside of Catalyst.
795 C<MyApp::Schema> is the name of the DBIC schema file written to
796 F<lib/MyApp/Schema.pm>.
800 C<create=static> causes L<DBIx::Class::Schema::Loader> to load the
801 schema as it runs and then write that information out into
802 F<lib/MyApp/Schema.pm> and files under the F<lib/MyApp/Schema>
807 C<dbi:SQLite:myapp.db> is the standard DBI connect string for use with
812 And finally, the C<on_connect_do> string requests that
813 L<DBIx::Class::Schema::Loader> create
814 foreign key relationships for us (this is not needed for databases such
815 as PostgreSQL and MySQL, but is required for SQLite). If you take a look
816 at F<lib/MyApp/Model/DB.pm>, you will see that the SQLite pragma is
817 propagated to the Model, so that SQLite's recent (and optional) foreign
818 key enforcement is enabled at the start of every database connection.
823 If you look in the F<lib/MyApp/Schema.pm> file, you will find that it
824 only contains a call to the C<load_namespaces> method. You will also
825 find that F<lib/MyApp> contains a C<Schema> subdirectory, which then has
826 a subdirectory called "Result". This "Result" subdirectory then has
827 files named according to each of the tables in our simple database
828 (F<Author.pm>, F<BookAuthor.pm>, and F<Book.pm>). These three files are
829 called "Result Classes" (or
830 "L<ResultSource Classes|DBIx::Class::ResultSource>") in DBIx::Class
831 nomenclature. Although the Result Class files are named after tables in
832 our database, the classes correspond to the I<row-level data> that is
833 returned by DBIC (more on this later, especially in
834 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
836 The idea with the Result Source files created under
837 F<lib/MyApp/Schema/Result> by the C<create=static> option is to only
838 edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
839 warning. If you place all of your changes below that point in the file,
840 you can regenerate the automatically created information at the top of
841 each file should your database structure get updated.
843 Also note the "flow" of the model information across the various files
844 and directories. Catalyst will initially load the model from
845 F<lib/MyApp/Model/DB.pm>. This file contains a reference to
846 F<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the call
847 to C<load_namespaces> in C<Schema.pm> will load each of the "Result
848 Class" files from the F<lib/MyApp/Schema/Result> subdirectory. The
849 final outcome is that Catalyst will dynamically create three
850 table-specific Catalyst models every time the application starts (you
851 can see these three model files listed in the debug output generated
852 when you launch the application).
854 Additionally, the F<lib/MyApp/Schema.pm> model can easily be loaded
855 outside of Catalyst, for example, in command-line utilities and/or cron
856 jobs. F<lib/MyApp/Model/DB.pm> provides a very thin "bridge" between
857 Catalyst and this external database model. Once you see how we can
858 add some powerful features to our DBIC model in
859 L<Chapter 4|Catalyst::Manual::Tutorial::04_BasicCRUD>, the elegance
860 of this approach will start to become more obvious.
862 B<NOTE:> Older versions of
863 L<Catalyst::Model::DBIC::Schema> use the
864 deprecated DBIx::Class C<load_classes> technique instead of the newer
865 C<load_namespaces>. For new applications, please try to use
866 C<load_namespaces> since it more easily supports a very useful DBIC
867 technique called "ResultSet Classes." If you need to convert an
868 existing application from "load_classes" to "load_namespaces," you can
869 use this process to automate the migration, but first make sure you have
870 version C<0.39> of L<Catalyst::Model::DBIC::Schema> and
871 L<DBIx::Class::Schema::Loader> version C<0.05000> or later.
873 $ # Re-run the helper to upgrade for you
874 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
875 create=static naming=current use_namespaces=1 \
876 dbi:SQLite:myapp.db \
877 on_connect_do="PRAGMA foreign_keys = ON"
880 =head1 ENABLE THE MODEL IN THE CONTROLLER
882 Open F<lib/MyApp/Controller/Books.pm> and un-comment the model code we
883 left disabled earlier so that your version matches the following
884 (un-comment the line containing C<< [$c->model('DB::Book')->all] >>
885 and delete the next 2 lines):
889 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
894 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
895 # 'Context' that's used to 'glue together' the various components
896 # that make up the application
899 # Retrieve all of the book records as book model objects and store
900 # in the stash where they can be accessed by the TT template
901 $c->stash(books => [$c->model('DB::Book')->all]);
903 # Set the TT template to use. You will almost always want to do this
904 # in your action methods (action methods respond to user input in
906 $c->stash(template => 'books/list.tt2');
909 B<TIP>: You may see the C<< $c->model('DB::Book') >> un-commented above
910 written as C<< $c->model('DB')->resultset('Book') >>. The two are
911 equivalent. Either way, C<< $c->model >> returns a
912 L<DBIx::Class::ResultSet> which handles queries
913 against the database and iterating over the set of results that is
916 We are using the C<< ->all >> to fetch all of the books. DBIC supports
917 a wide variety of more advanced operations to easily do things like
918 filtering and sorting the results. For example, the following could be
919 used to sort the results by descending title:
921 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
923 Some other examples are provided in
924 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with additional
925 information found at L<DBIx::Class::ResultSet/search>,
926 L<DBIx::Class::Manual::FAQ/Searching>, L<DBIx::Class::Manual::Intro> and
927 L<Catalyst::Model::DBIC::Schema>.
930 =head2 Test Run The Application
932 First, let's enable an environment variable that causes L<DBIx::Class>
933 to dump the SQL statements used to access the database. This is a
934 helpful trick when you are trying to debug your database-oriented code.
935 Press C<Ctrl-C> to break out of the development server and enter:
937 $ export DBIC_TRACE=1
938 $ script/myapp_server.pl -r
940 This assumes you are using bash as your shell -- adjust accordingly if
941 you are using a different shell (for example, under tcsh, use
942 C<setenv DBIC_TRACE 1>).
944 B<NOTE:> You can also set this in your code using
945 C<< $class->storage->debug(1); >>. See
946 L<DBIx::Class::Manual::Troubleshooting> for details (including options
947 to log to a file instead of displaying to the Catalyst development
950 Then launch the Catalyst development server. The log output should
951 display something like:
953 $ script/myapp_server.pl -r
954 [debug] Debug messages enabled
955 [debug] Statistics enabled
956 [debug] Loaded plugins:
957 .----------------------------------------------------------------------------.
958 | Catalyst::Plugin::ConfigLoader 0.30 |
959 | Catalyst::Plugin::StackTrace 0.11 |
960 '----------------------------------------------------------------------------'
962 [debug] Loaded dispatcher "Catalyst::Dispatcher"
963 [debug] Loaded engine "Catalyst::Engine"
964 [debug] Found home "/home/catalyst/MyApp"
965 [debug] Loaded Config "/home/catalyst/MyApp/myapp.conf"
966 [debug] Loaded components:
967 .-----------------------------------------------------------------+----------.
969 +-----------------------------------------------------------------+----------+
970 | MyApp::Controller::Books | instance |
971 | MyApp::Controller::Root | instance |
972 | MyApp::Model::DB | instance |
973 | MyApp::Model::DB::Author | class |
974 | MyApp::Model::DB::Book | class |
975 | MyApp::Model::DB::BookAuthor | class |
976 | MyApp::View::HTML | instance |
977 '-----------------------------------------------------------------+----------'
979 [debug] Loaded Private actions:
980 .----------------------+--------------------------------------+--------------.
981 | Private | Class | Method |
982 +----------------------+--------------------------------------+--------------+
983 | /default | MyApp::Controller::Root | default |
984 | /end | MyApp::Controller::Root | end |
985 | /index | MyApp::Controller::Root | index |
986 | /books/index | MyApp::Controller::Books | index |
987 | /books/list | MyApp::Controller::Books | list |
988 '----------------------+--------------------------------------+--------------'
990 [debug] Loaded Path actions:
991 .-------------------------------------+--------------------------------------.
993 +-------------------------------------+--------------------------------------+
996 | /books | /books/index |
997 | /books/list | /books/list |
998 '-------------------------------------+--------------------------------------'
1000 [info] MyApp powered by Catalyst 5.80020
1001 HTTP::Server::PSGI: Accepting connections at http://0:3000
1003 B<NOTE:> Be sure you run the F<script/myapp_server.pl> command from the
1004 'base' directory of your application, not inside the F<script> directory
1005 itself or it will not be able to locate the F<myapp.db> database file.
1006 You can use a fully qualified or a relative path to locate the database
1007 file, but we did not specify that when we ran the model helper earlier.
1009 Some things you should note in the output above:
1015 L<Catalyst::Model::DBIC::Schema> dynamically created three model
1016 classes, one to represent each of the three tables in our database
1017 (C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>, and
1018 C<MyApp::Model::DB::Book>).
1022 The "list" action in our Books controller showed up with a path of
1027 Point your browser to L<http://localhost:3000> and you should still get
1028 the Catalyst welcome page.
1030 Next, to view the book list, change the URL in your browser to
1031 L<http://localhost:3000/books/list>. You should get a list of the five
1032 books loaded by the F<myapp01.sql> script above without any formatting.
1033 The rating for each book should appear on each row, but the "Author(s)"
1034 column will still be blank (we will fill that in later).
1036 Also notice in the output of the F<script/myapp_server.pl> that
1037 L<DBIx::Class> used the following SQL to retrieve the data:
1039 SELECT me.id, me.title, me.rating FROM book me
1041 because we enabled DBIC_TRACE.
1043 You now have the beginnings of a simple but workable web application.
1044 Continue on to future sections and we will develop the application more
1048 =head1 CREATE A WRAPPER FOR THE VIEW
1050 When using TT, you can (and should) create a wrapper that will literally
1051 wrap content around each of your templates. This is certainly useful as
1052 you have one main source for changing things that will appear across
1053 your entire site/application instead of having to edit many individual
1057 =head2 Configure HTML.pm For The Wrapper
1059 In order to create a wrapper, you must first edit your TT view and tell
1060 it where to find your wrapper file.
1062 Edit your TT view in F<lib/MyApp/View/HTML.pm> and change it to match
1065 __PACKAGE__->config(
1066 # Change default TT extension
1067 TEMPLATE_EXTENSION => '.tt2',
1068 # Set the location for TT files
1070 MyApp->path_to( 'root', 'src' ),
1072 # Set to 1 for detailed timer stats in your HTML as comments
1074 # This is your wrapper template located in the 'root/src'
1075 WRAPPER => 'wrapper.tt2',
1079 =head2 Create the Wrapper Template File and Stylesheet
1081 Next you need to set up your wrapper template. Basically, you'll want
1082 to take the overall layout of your site and put it into this file. For
1083 the tutorial, open F<root/src/wrapper.tt2> and input the following:
1085 <?xml version="1.0" encoding="UTF-8"?>
1086 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" [%#
1087 %]"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1088 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
1090 <title>[% template.title or "My Catalyst App!" %]</title>
1091 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1097 [%# Your logo could go here -%]
1098 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1099 [%# Insert the page title -%]
1100 <h1>[% template.title or site.title %]</h1>
1103 <div id="bodyblock">
1107 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1108 <li><a href="[% c.uri_for('/')
1109 %]" title="Catalyst Welcome Page">Welcome</a></li>
1111 </div><!-- end menu -->
1114 [%# Status and error messages %]
1115 <span class="message">[% status_msg %]</span>
1116 <span class="error">[% error_msg %]</span>
1117 [%# This is where TT will stick all of your template's contents. -%]
1119 </div><!-- end content -->
1120 </div><!-- end bodyblock -->
1122 <div id="footer">Copyright (c) your name goes here</div>
1123 </div><!-- end outer -->
1128 Notice the status and error message sections in the code above:
1130 <span class="status">[% status_msg %]</span>
1131 <span class="error">[% error_msg %]</span>
1133 If we set either message in the Catalyst stash (e.g.,
1134 C<< $c->stash->{status_msg} = 'Request was successful!' >>) it will
1135 be displayed whenever any view used by that request is rendered. The
1136 C<message> and C<error> CSS styles can be customized to suit your needs
1137 in the F<root/static/css/main.css> file we create below.
1145 The Catalyst stash only lasts for a single HTTP request. If you need to
1146 retain information across requests you can use
1147 L<Catalyst::Plugin::Session> (we will use Catalyst sessions in the
1148 Authentication chapter of the tutorial).
1152 Although it is beyond the scope of this tutorial, you may wish to use a
1153 JavaScript or AJAX tool such as jQuery (L<https://www.jquery.com>) or
1154 Dojo (L<https://dojotoolkit.org/>).
1159 =head3 Create A Basic Stylesheet
1161 First create a central location for stylesheets under the static
1164 $ mkdir root/static/css
1166 Then open the file F<root/static/css/main.css> (the file referenced in
1167 the stylesheet href link of our wrapper above) and add the following
1186 background-color: #ddd;
1192 padding: 0 0 50% 5px;
1193 font-weight: normal;
1194 background-color: #ddd;
1207 You may wish to check out a "CSS Framework" like Emastic
1208 (L<http://code.google.com/p/emastic/>) as a way to quickly provide lots
1209 of high-quality CSS functionality.
1212 =head2 Test Run The Application
1214 Hit "Reload" in your web browser and you should now see a formatted
1215 version of our basic book list. (Again, the development server should
1216 have automatically restarted when you made changes to
1217 F<lib/MyApp/View/HTML.pm>. If you are not using the "-r" option, you
1218 will need to hit C<Ctrl-C> and manually restart it. Also note that the
1219 development server does I<NOT> need to restart for changes to the TT and
1220 static files we created and edited in the C<root> directory -- those
1221 updates are handled on a per-request basis.)
1223 Although our wrapper and stylesheet are obviously very simple, you
1224 should see how it allows us to control the overall look of an entire
1225 website from two central files. To add new pages to the site, just
1226 provide a template that fills in the C<content> section of our wrapper
1227 template -- the wrapper will provide the overall feel of the page.
1230 =head2 Updating the Generated DBIx::Class Result Class Files
1232 If you take a look at the Schema files automatically generated by
1233 L<DBIx::Class::Schema::Loader>, you will see that it has already defined
1234 C<has_many> and C<belongs_to> relationships on each side of our foreign
1235 keys. For example, take a look at F<lib/MyApp/Schema/Result/Book.pm> and
1236 notice the following code:
1244 Related object: L<MyApp::Schema::Result::BookAuthor>
1248 __PACKAGE__->has_many(
1250 "MyApp::Schema::Result::BookAuthor",
1251 { "foreign.book_id" => "self.id" },
1252 { cascade_copy => 0, cascade_delete => 0 },
1255 Each C<Book> "has_many" C<book_authors>, where C<BookAuthor> is the
1256 many-to-many table that allows each Book to have multiple Authors, and
1257 each Author to have multiple books. The arguments to C<has_many> are:
1263 C<book_authors> - The name for this relationship. DBIC will create an
1264 accessor on the C<Books> DBIC Row object with this name.
1268 C<MyApp::Schema::Result::BookAuthor> - The name of the DBIC model class
1269 referenced by this C<has_many> relationship.
1273 C<foreign.book_id> - C<book_id> is the name of the foreign key column in
1274 the I<foreign> table that points back to this table.
1278 C<self.id> - C<id> is the name of the column in I<this> table that is
1279 referenced by the foreign key.
1283 See L<DBIx::Class::Relationship/has_many> for additional information.
1284 Note that you might see a "hand coded" version of the C<has_many>
1285 relationship above expressed as:
1287 __PACKAGE__->has_many(
1289 "MyApp::Schema::Result::BookAuthor",
1293 Where the third argument is simply the name of the column in the foreign
1294 table. However, the hashref syntax used by
1295 L<DBIx::Class::Schema::Loader> is more flexible (for example, it can
1296 handle "multi-column foreign keys").
1298 B<Note:> If you are using older versions of SQLite and related DBIC
1299 tools, you will need to manually define your C<has_many> and
1300 C<belongs_to> relationships. We recommend upgrading to the versions
1301 specified above. :-)
1303 Have a look at F<lib/MyApp/Schema/Result/BookAuthor.pm> and notice that
1304 there is a C<belongs_to> relationship defined that acts as the "mirror
1305 image" to the C<has_many> relationship we just looked at above:
1313 Related object: L<MyApp::Schema::Result::Book>
1317 __PACKAGE__->belongs_to(
1319 "MyApp::Schema::Result::Book",
1320 { id => "book_id" },
1321 { join_type => "LEFT", on_delete => "CASCADE", on_update => "CASCADE" },
1324 The arguments are similar, but see
1325 L<DBIx::Class::Relationship/belongs_to> for the details.
1327 Although recent versions of SQLite and L<DBIx::Class::Schema::Loader>
1328 automatically handle the C<has_many> and C<belongs_to> relationships,
1329 C<many_to_many> relationship bridges (not technically a relationship)
1330 currently need to be manually inserted. To add a C<many_to_many>
1331 relationship bridge, first edit F<lib/MyApp/Schema/Result/Book.pm> and
1332 add the following text below the C<# You can replace this text...>
1337 # 1) Name of relationship bridge, DBIC will create accessor with this name
1338 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1339 # 3) Name of belongs_to() relationship in model class of has_many() above
1340 # You must already have the has_many() defined to use a many_to_many().
1341 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1343 B<Note:> Be careful to put this code I<above> the C<1;> at the end of
1344 the file. As with any Perl package, we need to end the last line with a
1345 statement that evaluates to C<true>. This is customarily done with
1346 C<1;> on a line by itself.
1348 The C<many_to_many> relationship bridge is optional, but it makes it
1349 easier to map a book to its collection of authors. Without it, we would
1350 have to "walk" through the C<book_author> table as in
1351 C<< $book->book_author->first->author->last_name >> (we will
1352 see examples on how to use DBIx::Class objects in your code soon, but
1353 note that because C<< $book->book_author >> can return multiple authors,
1354 we have to use C<first> to display a single author). C<many_to_many>
1355 allows us to use the shorter
1356 C<< $book->author->first->last_name >>. Note that you cannot
1357 define a C<many_to_many> relationship bridge without also having the
1358 C<has_many> relationship in place.
1360 Then edit F<lib/MyApp/Schema/Result/Author.pm> and add the reverse
1361 C<many_to_many> relationship bridge for C<Author> as follows (again, be
1362 careful to put in above the C<1;> but below the C<# DO NOT MODIFY THIS
1363 OR ANYTHING ABOVE!> comment):
1367 # 1) Name of relationship bridge, DBIC will create accessor with this name
1368 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1369 # 3) Name of belongs_to() relationship in model class of has_many() above
1370 # You must already have the has_many() defined to use a many_to_many().
1371 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
1374 =head2 Run The Application
1376 Run the Catalyst development server script with the C<DBIC_TRACE> option
1377 (it might still be enabled from earlier in the tutorial, but here is an
1378 alternate way to specify the trace option just in case):
1380 $ DBIC_TRACE=1 script/myapp_server.pl -r
1382 Make sure that the application loads correctly and that you see the
1383 three dynamically created model classes (one for each of the Result
1384 Classes we created).
1386 Then hit the URL L<http://localhost:3000/books/list> with your browser
1387 and be sure that the book list still displays correctly.
1389 B<Note:> You will not see the authors yet because the view isn't taking
1390 advantage of these relationships. Read on to the next section where we
1391 update the template to do that.
1394 =head1 UPDATING THE VIEW
1396 Let's add a new column to our book list page that takes advantage of the
1397 relationship information we manually added to our schema files in the
1398 previous section. Edit F<root/src/books/list.tt2> and replace the
1399 "empty" table cell "C<< <td></td> >>" with the following:
1403 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1404 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1405 [% # loop in 'side effect notation' to load just the last names of the -%]
1406 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
1407 [% # a value, so nothing will be printed here. But, if you have something -%]
1408 [% # in TT that does return a value and you don't want it printed, you -%]
1409 [% # 1) assign it to a bogus value, or -%]
1410 [% # 2) use the CALL keyword to call it and discard the return value. -%]
1411 [% tt_authors = [ ];
1412 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1413 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1414 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1415 ([% tt_authors.size | html %])
1416 [% # Use another TT vmethod to join & print the names & comma separators -%]
1417 [% tt_authors.join(', ') | html %]
1421 B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1422 possible out of your views. This kind of logic belongs in your model
1423 (the same goes for controllers -- keep them as "thin" as possible and
1424 push all of the "complicated code" out to your model objects). Avoid
1425 code like you see in the previous example -- we are only using it here
1426 to show some extra features in TT until we get to the more advanced
1427 model features we will see in Chapter 4 (see
1428 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1430 Then hit "Reload" in your browser (note that you don't need to reload
1431 the development server or use the C<-r> option when updating TT
1432 templates) and you should now see the number of authors each book has
1433 along with a comma-separated list of the authors' last names. (If you
1434 didn't leave the development server running from the previous step, you
1435 will obviously need to start it before you can refresh your browser
1438 If you are still running the development server with C<DBIC_TRACE>
1439 enabled, you should also now see five more C<SELECT> statements in the
1440 debug output (one for each book as the authors are being retrieved by
1443 SELECT me.id, me.title, me.rating FROM book me:
1444 SELECT author.id, author.first_name, author.last_name FROM book_author me
1445 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '1'
1446 SELECT author.id, author.first_name, author.last_name FROM book_author me
1447 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '2'
1448 SELECT author.id, author.first_name, author.last_name FROM book_author me
1449 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '3'
1450 SELECT author.id, author.first_name, author.last_name FROM book_author me
1451 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '4'
1452 SELECT author.id, author.first_name, author.last_name FROM book_author me
1453 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '5'
1455 Also note in F<root/src/books/list.tt2> that we are using "| html", a
1456 type of TT filter, to escape characters such as < and > to <
1457 and > and avoid various types of dangerous hacks against your
1458 application. In a real application, you would probably want to put "|
1459 html" at the end of every field where a user has control over the
1460 information that can appear in that field (and can therefore inject
1461 markup or code if you don't "neutralize" those fields). In addition to
1462 "| html", Template Toolkit has a variety of other useful filters that
1463 can be found in the documentation for L<Template::Filters>. (While we
1464 are on the topic of security and escaping of dangerous values, one of
1465 the advantages of using tools like DBIC for database access or
1466 L<HTML::FormFu> for form management [see
1467 L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD::09_FormFu>]
1468 is that they automatically handle most escaping for you and therefore
1469 dramatically increase the security of your app.)
1472 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1474 In some situations, it can be useful to run your application and display
1475 a page without using a browser. Catalyst lets you do this using the
1476 F<script/myapp_test.pl> script. Just supply the URL you wish to
1477 display and it will run that request through the normal controller
1478 dispatch logic and use the appropriate view to render the output
1479 (obviously, complex pages may dump a lot of text to your terminal
1480 window). For example, if C<Ctrl+C> out of the development server
1483 $ script/myapp_test.pl "/books/list"
1485 You should get the same text as if you visited
1486 L<http://localhost:3000/books/list> with the normal development server
1487 and asked your browser to view the page source. You can even pipe this
1488 HTML text output to a text-based browser using a command like:
1490 $ script/myapp_test.pl "/books/list" | lynx -stdin
1492 And you should see a fully rendered text-based view of your page. (If
1493 you are following along in Debian 6, type
1494 C<sudo aptitude -y install lynx> to install lynx.) If you do start
1495 lynx, you can use the "Q" key to quit.
1498 =head1 OPTIONAL INFORMATION
1500 B<NOTE: The rest of this chapter of the tutorial is optional. You can
1501 skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
1505 =head2 Using 'RenderView' for the Default View
1507 Once your controller logic has processed the request from a user, it
1508 forwards processing to your view in order to generate the appropriate
1509 response output. Catalyst uses
1510 L<Catalyst::Action::RenderView> by default
1511 to automatically perform this operation. If you look in
1512 F<lib/MyApp/Controller/Root.pm>, you should see the empty definition for
1513 the C<sub end> method:
1515 sub end : ActionClass('RenderView') {}
1517 The following bullet points provide a quick overview of the
1518 C<RenderView> process:
1524 F<Root.pm> is designed to hold application-wide logic.
1528 At the end of a given user request, Catalyst will call the most specific
1529 C<end> method that's appropriate. For example, if the controller for a
1530 request has an C<end> method defined, it will be called. However, if
1531 the controller does not define a controller-specific C<end> method, the
1532 "global" C<end> method in F<Root.pm> will be called.
1536 Because the definition includes an C<ActionClass> attribute, the
1537 L<Catalyst::Action::RenderView> logic will be executed B<after> any code
1538 inside the definition of C<sub end> is run. See
1539 L<Catalyst::Manual::Actions> for more information on C<ActionClass>.
1543 Because C<sub end> is empty, this effectively just runs the default
1544 logic in C<RenderView>. However, you can easily extend the
1545 C<RenderView> logic by adding your own code inside the empty method body
1546 (C<{}>) created by the Catalyst Helpers when we first ran the
1547 F<catalyst.pl> to initialize our application. See
1548 L<Catalyst::Action::RenderView> for more
1549 detailed information on how to extend C<RenderView> in C<sub end>.
1554 =head2 RenderView's "dump_info" Feature
1556 One of the nice features of C<RenderView> is that it automatically
1557 allows you to add C<dump_info=1> to the end of any URL for your
1558 application and it will force the display of the "exception dump" screen
1559 to the client browser. You can try this out by pointing your browser to
1562 http://localhost:3000/books/list?dump_info=1
1564 You should get a page with the following message at the top:
1566 Caught exception in MyApp::Controller::Root->end "Forced debug -
1567 Scrubbed output at /usr/share/perl5/Catalyst/Action/RenderView.pm line 46."
1569 Along with a summary of your application's state at the end of the
1570 processing for that request. The "Stash" section should show a
1571 summarized version of the DBIC book model objects. If desired, you can
1572 adjust the summarization logic (called "scrubbing" logic) -- see
1573 L<Catalyst::Action::RenderView> for
1576 Note that you shouldn't need to worry about "normal clients" using this
1577 technique to "reverse engineer" your application -- C<RenderView> only
1578 supports the C<dump_info=1> feature when your application is running in
1579 C<-Debug> mode (something you won't do once you have your application
1580 deployed in production).
1583 =head2 Using The Default Template Name
1585 By default, C<Catalyst::View::TT> will look for a template that uses the
1586 same name as your controller action, allowing you to save the step of
1587 manually specifying the template name in each action. For example, this
1588 would allow us to remove the
1589 C<< $c->stash->{template} = 'books/list.tt2'; >>
1590 line of our C<list> action in the Books controller.
1591 Open C<lib/MyApp/Controller/Books.pm> in your editor and comment out
1592 this line to match the following (only the
1593 C<< $c->stash->{template} >> line has changed):
1597 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1602 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1603 # 'Context' that's used to 'glue together' the various components
1604 # that make up the application
1605 my ($self, $c) = @_;
1607 # Retrieve all of the book records as book model objects and store in the
1608 # stash where they can be accessed by the TT template
1609 $c->stash(books => [$c->model('DB::Book')->all]);
1611 # Set the TT template to use. You will almost always want to do this
1612 # in your action methods (actions methods respond to user input in
1613 # your controllers).
1614 #$c->stash(template => 'books/list.tt2');
1618 You should now be able to access the L<http://localhost:3000/books/list>
1621 B<NOTE:> If you use the default template technique, you
1622 will B<not> be able to use either the C<< $c->forward >> or the
1623 C<< $c->detach >> mechanisms (these are discussed in Chapter 2 and
1624 Chapter 9 of the Tutorial).
1626 B<IMPORTANT:> Make sure that you do B<not> skip the following section
1627 before continuing to the next chapter 4 Basic CRUD.
1630 =head2 Return To A Manually Specified Template
1632 In order to be able to use C<< $c->forward >> and C<< $c->detach >>
1633 later in the tutorial, you should remove the comment from the statement
1634 in C<sub list> in F<lib/MyApp/Controller/Books.pm>:
1636 $c->stash(template => 'books/list.tt2');
1638 Then delete the C<TEMPLATE_EXTENSION> line in F<lib/MyApp/View/HTML.pm>.
1640 Check the L<http://localhost:3000/books/list> URL in your browser. It
1641 should look the same manner as with earlier sections.
1644 You can jump to the next chapter of the tutorial here:
1645 L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
1650 Kennedy Clark, C<hkclark@gmail.com>
1652 Feel free to contact the author for any errors or suggestions, but the
1653 best way to report issues is via the CPAN RT Bug system at
1654 L<https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
1656 Copyright 2006-2011, Kennedy Clark, under the
1657 Creative Commons Attribution Share-Alike License Version 3.0
1658 (L<https://creativecommons.org/licenses/by-sa/3.0/us/>).