3 Catalyst::Manual::Tutorial::03_MoreCatalystBasics - Catalyst Tutorial - Chapter 3: More Catalyst Application Development Basics
8 This is B<Chapter 3 of 10> for the Catalyst tutorial.
10 L<Tutorial Overview|Catalyst::Manual::Tutorial>
16 L<Introduction|Catalyst::Manual::Tutorial::01_Intro>
20 L<Catalyst Basics|Catalyst::Manual::Tutorial::02_CatalystBasics>
24 B<03_More Catalyst Basics>
28 L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
32 L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>
36 L<Authorization|Catalyst::Manual::Tutorial::06_Authorization>
40 L<Debugging|Catalyst::Manual::Tutorial::07_Debugging>
44 L<Testing|Catalyst::Manual::Tutorial::08_Testing>
48 L<Advanced CRUD|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
52 L<Appendices|Catalyst::Manual::Tutorial::10_Appendices>
59 This chapter of the tutorial builds on the work done in Chapter 2 to
60 explore some features that are more typical of "real world" web
61 applications. From this chapter of the tutorial onward, we will be
62 building a simple book database application. Although the application
63 will be too limited to be of use to anyone, it should provide a basic
64 environment where we can explore a variety of features used in
65 virtually all web applications.
67 You can check out the source code for this example from the Catalyst
68 Subversion repository as per the instructions in
69 L<Catalyst::Manual::Tutorial::01_Intro|Catalyst::Manual::Tutorial::01_Intro>.
72 L<Catalyst::Manual::Tutorial::01_Intro/CATALYST INSTALLATION> before
73 doing the rest of this tutorial. Although the tutorial should work
74 correctly under most any recent version of Perl running on any
75 operating system, the tutorial has been written using Debian 5 and
76 tested to be sure it runs correctly in this environment.
79 =head1 CREATE A NEW APPLICATION
81 The remainder of the tutorial will build an application called C<MyApp>.
82 First use the Catalyst C<catalyst.pl> script to initialize the framework
83 for the C<MyApp> application (make sure you aren't still inside the
84 directory of the C<Hello> application from the previous chapter of the
85 tutorial or in a directory that already has a "MyApp" subdirectory):
89 created "MyApp/script"
93 created "MyApp/script/myapp_create.pl"
94 Change to application directory and Run "perl Makefile.PL" to make sure your install is complete
97 This creates a similar skeletal structure to what we saw in Chapter 2 of
98 the tutorial, except with C<MyApp> and C<myapp> substituted for
99 C<Hello> and C<hello>. (As noted in Chapter 2, omit the ".pl" from
100 the command if you are using Strawberry Perl.)
103 =head1 EDIT THE LIST OF CATALYST PLUGINS
105 One of the greatest benefits of Catalyst is that it has such a large
106 library of bases classes and plugins available that you can use easily
107 add functionality to your application. Plugins are used to seamlessly
108 integrate existing Perl modules into the overall Catalyst framework. In
109 general, they do this by adding additional methods to the C<context>
110 object (generally written as C<$c>) that Catalyst passes to every
111 component throughout the framework.
114 By default, Catalyst enables three plugins/flags:
122 Enables the Catalyst debug output you saw when we started the
123 C<script/myapp_server.pl> development server earlier. You can remove
124 this item when you place your application into production.
126 To be technically correct, it turns out that C<-Debug> is not a plugin, but a I<flag>.
127 Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
128 line of your application class will be plugins, Catalyst supports a
129 limited number of flag options (of these, C<-Debug> is the most
130 common). See the documentation for C<Catalyst.pm> to get details on
131 other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
133 If you prefer, there are several other ways to enable debug output:
139 Use the C<$c-E<gt>debug> method
143 The C<-d> option to C<script/myapp_server.pl>
147 The C<CATALYST_DEBUG=1> environment variable (or set it to
148 zero to templorarily disable debug output).
152 B<TIP>: Depending on your needs, it can be helpful to permanently
153 remove C<-Debug> from C<lib/MyApp.pm> and then use the C<-d> option
154 to C<script/myapp_server.pl> to re-enable it just for the development
155 server. We will not be using that approach in the tutorial, but feel
156 free to make use of it in your own projects.
160 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
162 C<ConfigLoader> provides an automatic way to load configurable
163 parameters for your application from a central
164 L<Config::General|Config::General> file (versus having the values
165 hard-coded inside your Perl modules). Config::General uses syntax
166 very similar to Apache configuration files. We will see how to use
167 this feature of Catalyst during the authentication and authorization
168 sections (Chapter 5 and Chapter 6).
170 B<IMPORTANT NOTE:> If you are using a version of
171 L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, be aware
172 that Catalyst changed the default format from YAML to the more
173 straightforward C<Config::General> style. This tutorial uses the
174 newer C<myapp.conf> file for C<Config::General>. However, Catalyst
175 supports both formats and will automatically use either C<myapp.conf>
176 or C<myapp.yml> (or any other format supported by
177 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
178 L<Config::Any|Config::Any>). If you are using a version of
179 Catalyst::Devel prior to 1.06, you can convert to the newer format by
180 simply creating the C<myapp.conf> file manually and deleting
181 C<myapp.yml>. The default contents of the C<myapp.conf> you create
182 should only consist of one line:
186 B<TIP>: This script can be useful for converting between configuration
189 perl -Ilib -e 'use MyApp; use Config::General;
190 Config::General->new->save_file("myapp.conf", MyApp->config);'
194 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
196 C<Static::Simple> provides an easy way to serve static content, such
197 as images and CSS files, from the development server.
201 For our application, we want to add one new plugin into the mix. To
202 do this, edit C<lib/MyApp.pm> (this file is generally referred to as
203 your I<application class>) and delete the lines with:
211 Then replace it with:
222 B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
223 techniques to load these plugins/flags. For example, you might see
226 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
228 Don't let these variations confuse you -- they all accomplish the same
231 This tells Catalyst to start using one additional plugin,
232 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
233 stack trace to the standard Catalyst "debug screen" (the screen
234 Catalyst sends to your browser when an error occurs). Be aware that
235 L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
236 browser, not in the console window from which you're running your
237 application, which is where logging output usually goes.
239 Make sure when adding new plugins you also include them as a new
240 dependency within the Makefile.PL file. For example, after adding
241 the StackTrace plugin the Makefile.PL should include the following
244 requires 'Catalyst::Plugin::StackTrace';
253 C<__PACKAGE__> is just a shorthand way of referencing the name of the
254 package where it is used. Therefore, in C<MyApp.pm>, C<__PACKAGE__>
255 is equivalent to C<MyApp>.
259 You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
260 before you put your application into production, but it can be helpful
265 When specifying plugins, you can omit C<Catalyst::Plugin::> from the
266 name. Additionally, you can spread the plugin names across multiple
267 lines as shown here or place them all on one line.
272 =head1 CREATE A CATALYST CONTROLLER
274 As discussed earlier, controllers are where you write methods that
275 interact with user input. Typically, controller methods respond to
276 C<GET> and C<POST> requests from the user's web browser.
278 Use the Catalyst C<create> script to add a controller for book-related
281 $ script/myapp_create.pl controller Books
282 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
283 exists "/home/me/MyApp/script/../t"
284 created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm"
285 created "/home/me/MyApp/script/../t/controller_Books.t"
287 Then edit C<lib/MyApp/Controller/Books.pm> (as discussed in Chapter 2 of
288 the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
289 each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
290 and add the following method to the controller:
294 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
299 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
300 # 'Context' that's used to 'glue together' the various components
301 # that make up the application
304 # Retrieve all of the book records as book model objects and store in the
305 # stash where they can be accessed by the TT template
306 # $c->stash(books => [$c->model('DB::Book')->all]);
307 # But, for now, use this code until we create the model later
308 $c->stash(books => '');
310 # Set the TT template to use. You will almost always want to do this
311 # in your action methods (action methods respond to user input in
313 $c->stash(template => 'books/list.tt2');
316 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
317 cutting and pasting example code from POD-based documents.
319 Programmers experienced with object-oriented Perl should recognize
320 C<$self> as a reference to the object where this method was called.
321 On the other hand, C<$c> will be new to many Perl programmers who have
322 not used Catalyst before (it's sometimes written as C<$context>). The
323 Context object is automatically passed to all Catalyst components. It
324 is used to pass information between components and provide access to
325 Catalyst and plugin functionality.
327 Catalyst actions are regular Perl methods, but they make use of
328 attributes (the "C<:Local>" next to the "C<sub list>" in the code
329 above) to provide additional information to the Catalyst dispatcher
330 logic (note that the space between the colon and the attribute name is
331 optional; you will see attributes written both ways). Most Catalyst
332 Controllers use one of five action types:
338 B<:Private> -- Use C<:Private> for methods that you want to make into
339 an action, but you do not want Catalyst to directly expose the method
340 to your users. Catalyst will not map C<:Private> methods to a URI.
341 Use them for various sorts of "special" methods (the C<begin>,
342 C<auto>, etc. discussed below) or for methods you want to be able to
343 C<forward> or C<detach> to. (If the method is a plain old "helper
344 method" that you don't want to be an action at all, then just define
345 the method without any attribute -- you can call it in your code, but
346 the Catalyst dispatcher will ignore it.)
348 There are five types of "special" build-in C<:Private> actions:
349 C<begin>, C<end>, C<default>, C<index>, and C<auto>.
355 With C<begin>, C<end>, C<default>, C<index> private actions, only the
356 most specific action of each type will be called. For example, if you
357 define a C<begin> action in your controller it will I<override> a
358 C<begin> action in your application/root controller -- I<only> the
359 action in your controller will be called.
363 Unlike the other actions where only a single method is called for each
364 request, I<every> auto action along the chain of namespaces will be
365 called. Each C<auto> action will be called I<from the application/root
366 controller down through the most specific class>.
372 B<:Path> -- C<:Path> actions let you map a method to an explicit URI
373 path. For example, "C<:Path('list')>" in
374 C<lib/MyApp/Controller/Books.pm> would match on the URL
375 C<http://localhost:3000/books/list>, but "C<:Path('/list')>" would
376 match on C<http://localhost:3000/list> (because of the leading slash).
377 You can use C<:Args()> to specify how many arguments an action should
378 accept. See L<Catalyst::Manual::Intro/Action_types> for more
379 information and examples.
383 B<:Local> -- C<:Local> is merely a shorthand for
384 "C<:Path('_name_of_method_')>". For example, these are equivalent:
385 "C<sub create_book :Local {...}>" and
386 "C<sub create_book :Path('create_book') {...}>".
390 B<:Global> -- C<:Global> is merely a shorthand for
391 "C<:Path('/_name_of_method_')>". For example, these are equivalent:
392 "C<sub create_book :Global {...}>" and
393 "C<sub create_book :Path('/create_book') {...}>".
397 B<:Chained> -- Newer Catalyst applications tend to use the Chained
398 dispatch form of action types because of its power and flexibility.
399 It allows a series of controller methods to be automatically dispatched
400 to service a single user request. See
401 L<Catalyst::Manual::Tutorial::04_BasicCRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
402 and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
403 for more information on chained actions.
407 You should refer to L<Catalyst::Manual::Intro/Action_types> for
408 additional information and for coverage of some lesser-used action
409 types not discussed here (C<Regex> and C<LocalRegex>).
412 =head1 CATALYST VIEWS
414 As mentioned in Chapter 2 of the tutorial, views are where you render
415 output, typically for display in the user's web browser (but also
416 possibly using into output-generation systems, such as PDF or JSON).
417 The code in C<lib/MyApp/View> selects the I<type> of view to use, with
418 the actual rendering template found in the C<root> directory. As with
419 virtually every aspect of Catalyst, options abound when it comes to the
420 specific view technology you adopt inside your application. However,
421 most Catalyst applications use the Template Toolkit, known as TT (for
422 more information on TT, see L<http://www.template-toolkit.org>). Other
423 somewhat popular view technologies include Mason
424 (L<http://www.masonhq.com> and L<http://www.masonbook.com>) and
425 L<HTML::Template> (L<http://html-template.sourceforge.net>).
428 =head2 Create a Catalyst View
430 When using TT for the Catalyst view, the main helper script
431 is L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>.
432 You may also come across references to
433 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>,
434 but its use is now deprecated.
436 Enter the following command to enable the C<TT> style of view
437 rendering for this tutorial:
439 $ script/myapp_create.pl view HTML TT
440 exists "/home/me/MyApp/script/../lib/MyApp/View"
441 exists "/home/me/MyApp/script/../t"
442 created "/home/me/MyApp/script/../lib/MyApp/View/HTML.pm"
443 created "/home/me/MyApp/script/../t/view_HTML.t"
445 This simply creates a view called C<HTML> in a file called C<HTML.pm> (the first
446 argument). It is now up to you to decide how you want to structure your view
447 layout. For the tutorial, we will start with a very simple TT template to
448 initially demonstrate the concepts, but quickly migrate to a more typical
449 "wrapper page" type of configuration (where the "wrapper" controls the overall
450 "look and feel" of your site from a single file or set of files).
452 Edit C<lib/MyApp/View/HTML.pm> and you should see that the default
453 contents contains something similar to the following:
455 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
457 And update it to match:
460 # Change default TT extension
461 TEMPLATE_EXTENSION => '.tt2',
462 # Set the location for TT files
464 MyApp->path_to( 'root', 'src' ),
468 B<NOTE:> Make sure to add a comma after '.tt2' outside the single
471 This changes the default extension for Template Toolkit from '.tt' to
472 '.tt2' and changes the base directory for your template files from
473 C<root> to C<root/src>. Stick with these conventions for the
474 tutorial, but feel free to use whatever options you desire in your
475 applications (as with most things Perl, there's more than one way to
478 B<Note:> We will use C<root/src> as the base directory for our
479 template files, with a full naming convention of
480 C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
481 use C<root/> as the base (with a full filename pattern of
482 C<root/_controller_name_/_action_name_.tt2>).
485 =head2 Create a TT Template Page
487 First create a directory for book-related TT templates:
489 $ mkdir -p root/src/books
491 Then create C<root/src/books/list.tt2> in your editor and enter:
493 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
494 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
495 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
496 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
498 [% # Provide a title -%]
499 [% META title = 'Book List' -%]
502 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
503 [% # Display each book in a table row %]
504 [% FOREACH book IN books -%]
506 <td>[% book.title %]</td>
507 <td>[% book.rating %]</td>
513 As indicated by the inline comments above, the C<META title> line uses
514 TT's META feature to provide a title to the "wrapper" that we will
515 create later. Meanwhile, the C<FOREACH> loop iterates through each
516 C<book> model object and prints the C<title> and C<rating> fields.
518 The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
519 supports a wide variety of directives for "calling" other files,
520 looping, conditional logic, etc. In general, TT simplifies the usual
521 range of Perl operators down to the single dot (".") operator. This
522 applies to operations as diverse as method calls, hash lookups, and list
524 L<http://search.cpan.org/perldoc?Template::Manual::Variables> for
525 details and examples). In addition to the usual L<Template> module Pod
526 documentation, you can access the TT manual at
527 L<http://search.cpan.org/perldoc?Template::Manual>.
529 B<TIP:> While you can build all sorts of complex logic into your TT
530 templates, you should in general keep the "code" part of your
531 templates as simple as possible. If you need more complex logic,
532 create helper methods in your model that abstract out a set of code
533 into a single call from your TT template. (Note that the same is true
534 of your controller logic as well -- complex sections of code in your
535 controllers should often be pulled out and placed into your model
536 objects.) In Chapter 4 of the tutorial we will explore some extremely
537 helpful and powerful features of L<DBIx::Class> that allow you to pull
538 code out of your views and controllers and place it where it
539 rightfully belongs in a model class.
542 =head2 Test Run The Application
544 To test your work so far, first start the development server:
546 $ script/myapp_server.pl -r
548 Then point your browser to L<http://localhost:3000> and you should
549 still get the Catalyst welcome page. Next, change the URL in your
550 browser to L<http://localhost:3000/books/list>. If you have
551 everything working so far, you should see a web page that displays
552 nothing other than our column headers for "Title", "Rating", and
553 "Author(s)" -- we will not see any books until we get the database and
556 If you run into problems getting your application to run correctly, it
557 might be helpful to refer to some of the debugging techniques covered in
558 the L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> chapter of the
562 =head1 CREATE A SQLITE DATABASE
564 In this step, we make a text file with the required SQL commands to
565 create a database table and load some sample data. We will use
566 SQLite (L<http://www.sqlite.org>), a popular database that is
567 lightweight and easy to use. Be sure to get at least version 3. Open
568 C<myapp01.sql> in your editor and enter:
571 -- Create a very simple database to hold book and author information
573 PRAGMA foreign_keys = ON;
575 id INTEGER PRIMARY KEY,
579 -- 'book_author' is a many-to-many join table between books & authors
580 CREATE TABLE book_author (
581 book_id INTEGER REFERENCES book(id) ON DELETE CASCADE ON UPDATE CASCADE,
582 author_id INTEGER REFERENCES author(id) ON DELETE CASCADE ON UPDATE CASCADE,
583 PRIMARY KEY (book_id, author_id)
585 CREATE TABLE author (
586 id INTEGER PRIMARY KEY,
591 --- Load some sample data
593 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
594 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
595 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
596 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
597 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
598 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
599 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
600 INSERT INTO author VALUES (3, 'Christian', 'Degu');
601 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
602 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
603 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
604 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
605 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
606 INSERT INTO book_author VALUES (1, 1);
607 INSERT INTO book_author VALUES (1, 2);
608 INSERT INTO book_author VALUES (1, 3);
609 INSERT INTO book_author VALUES (2, 4);
610 INSERT INTO book_author VALUES (3, 5);
611 INSERT INTO book_author VALUES (4, 6);
612 INSERT INTO book_author VALUES (4, 7);
613 INSERT INTO book_author VALUES (5, 8);
615 Then use the following command to build a C<myapp.db> SQLite database:
617 $ sqlite3 myapp.db < myapp01.sql
619 If you need to create the database more than once, you probably want to
620 issue the C<rm myapp.db> command to delete the database before you use
621 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
623 Once the C<myapp.db> database file has been created and initialized, you
624 can use the SQLite command line environment to do a quick dump of the
628 SQLite version 3.6.22
629 Enter ".help" for instructions
630 Enter SQL statements terminated with a ";"
631 sqlite> select * from book;
632 1|CCSP SNRS Exam Certification Guide|5
633 2|TCP/IP Illustrated, Volume 1|5
634 3|Internetworking with TCP/IP Vol.1|4
636 5|Designing with Web Standards|5
642 $ sqlite3 myapp.db "select * from book"
643 1|CCSP SNRS Exam Certification Guide|5
644 2|TCP/IP Illustrated, Volume 1|5
645 3|Internetworking with TCP/IP Vol.1|4
647 5|Designing with Web Standards|5
649 As with most other SQL tools, if you are using the full "interactive"
650 environment you need to terminate your SQL commands with a ";" (it's not
651 required if you do a single SQL statement on the command line). Use
652 ".q" to exit from SQLite from the SQLite interactive mode and return to
653 your OS command prompt.
655 Please note that here we have chosen to use 'singular' table names. This is
656 because the default inflection code for older versions of
657 L<DBIx::Class::Schema::Loader> does NOT handle plurals. There has been much
658 philosophical discussion on whether table names should be plural or singular.
659 There is no one correct answer, as long as one makes a choice and remains
660 consistent with it. If you prefer plural table names (e.g. you think that they
661 are easier to read) then see the documentation in
662 L<DBIx::Class::Schema::Loader::Base/naming> (version 0.05 or greater).
664 For using other databases, such as PostgreSQL or MySQL, see
665 L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices>.
668 =head1 DATABASE ACCESS WITH DBIx::Class
670 Catalyst can be used with virtually any form of datastore available
671 via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
672 can be used to access databases through the traditional Perl L<DBI>
673 interface or you can use a model to access files of any type on the
674 filesystem. However, most Catalyst applications use some form of
675 object-relational mapping (ORM) technology to create objects
676 associated with tables in a relational database. Matt Trout's
677 L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
678 as the Perl-based ORM technology of choice. Most new Catalyst
679 applications rely on DBIx::Class, as will this tutorial.
681 Although DBIx::Class has included support for a C<create=dynamic> mode
682 to automatically read the database structure every time the
683 application starts, it's use is no longer recommended. While it can
684 make for "flashy" demos, the use of the C<create=static> mode we use
685 below can be implemented just as quickly and provides many advantages
686 (such as the ability to add your own methods to the overall DBIC
687 framework, a technique that we see in Chapter 4).
690 =head2 Make Sure You Have a Recent Version of the DBIx::Class Model
692 First, let's be sure we have a recent version of the DBIC helper,
693 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, so
694 that we can take advantage of some recent enhancements in how
695 foreign keys are handled with SQLite. To check your version,
698 $ perl -MCatalyst::Model::DBIC::Schema -e \
699 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
702 Please note the '\' above. Depending on your environment, you might
703 be able to cut and paste the text as shown or need to remove the '\'
704 character to that the command is all on a single line.
706 If you are following along in Debian 5, you should have version 0.40 or
707 higher (shown above as "0.4" with the tailing zero removed). If you have
708 less than v0.39, you will need to run this command to install it
711 $ sudo cpan Catalyst::Model::DBIC::Schema
713 And re-run the version print command to verify that you are now at
716 In addition, since we are using SQLite's foreign key support here,
717 please be sure that you use version C<1.27> of L<DBD::SQLite> or later:
719 $ perl -MDBD::SQLite -e 'print "$DBD::SQLite::VERSION\n"'
722 Upgrade if you are not at version C<1.27> or higher.
725 =head2 Create Static DBIx::Class Schema Files
727 Before you continue, make sure your C<myapp.db> database file is in
728 the application's topmost directory. Now use the model helper with
729 the C<create=static> option to read the database with
730 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
731 automatically build the required files for us:
733 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
734 create=static dbi:SQLite:myapp.db \
735 on_connect_do="PRAGMA foreign_keys = ON"
736 exists "/home/me/MyApp/script/../lib/MyApp/Model"
737 exists "/home/me/MyApp/script/../t"
738 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
739 Schema dump completed.
740 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
741 created "/home/me/MyApp/script/../t/model_DB.t"
743 Please note the '\' above. Depending on your environment, you might
744 be able to cut and paste the text as shown or need to remove the '\'
745 character to that the command is all on a single line.
747 The C<script/myapp_create.pl> command breaks down like this:
753 C<DB> is the name of the model class to be created by the helper in
758 C<DBIC::Schema> is the type of the model to create.
762 C<MyApp::Schema> is the name of the DBIC schema file written to
763 C<lib/MyApp/Schema.pm>.
767 C<create=static> causes
768 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
769 load the schema as it runs and then write that information out
774 C<dbi:SQLite:myapp.db> is the standard DBI connect string
779 And finally, the C<on_connect_do> string requests that
780 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> create
781 foreign key relationships for us (this is not needed for databases such
782 as PostgreSQL and MySQL, but is required for SQLite). If you take a look
783 at C<lib/MyApp/Model/DB.pm>, you will see that the SQLite pragma is
784 propogated to the Model, so that SQLite's recent (and optional) foreign
785 key enforcement is enabled at the start of every database connection.
791 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
792 only contains a call to the C<load_namespaces> method. You will also
793 find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
794 has a subdirectory called "Result". This "Result" subdirectory then
795 has files named according to each of the tables in our simple database
796 (C<Author.pm>, C<BookAuthor.pm>, and C<Book.pm>). These three
797 files are called "Result Classes" in DBIx::Class nomenclature. Although the
798 Result Class files are named after tables in our database, the classes
799 correspond to the I<row-level data> that is returned by DBIC (more on
800 this later, especially in
801 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
803 The idea with the Result Source files created under
804 C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
805 edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
806 warning. If you place all of your changes below that point in the
807 file, you can regenerate the automatically created information at the
808 top of each file should your database structure get updated.
810 Also note the "flow" of the model information across the various files
811 and directories. Catalyst will initially load the model from
812 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
813 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the
814 call to C<load_namespaces> in C<Schema.pm> will load each of the
815 "Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
816 The final outcome is that Catalyst will dynamically create three
817 table-specific Catalyst models every time the application starts (you
818 can see these three model files listed in the debug output generated
819 when you launch the application).
821 B<NOTE:> Older versions of
822 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
823 deprecated DBIx::Class C<load_classes> technique instead of the newer
824 C<load_namespaces>. For new applications, please try to use
825 C<load_namespaces> since it more easily supports a very useful DBIC
826 technique called "ResultSet Classes." If you need to convert an
827 existing application from "load_classes" to "load_namespaces," you can
828 use this process to automate the migration, but first make sure you have
829 version C<0.39> of L<Catalyst::Model::DBIC::Schema> and
830 L<DBIx::Class::Schema::Loader> version C<0.05000> or later.
832 $ # Re-run the helper to upgrade for you
833 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
834 create=static naming=current use_namespaces=1 \
835 dbi:SQLite:myapp.db \
836 on_connect_do="PRAGMA foreign_keys = ON"
839 =head1 ENABLE THE MODEL IN THE CONTROLLER
841 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
842 left disabled earlier so that your version matches the following (un-
843 comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
844 and delete the next 2 lines):
848 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
853 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
854 # 'Context' that's used to 'glue together' the various components
855 # that make up the application
858 # Retrieve all of the book records as book model objects and store
859 # in the stash where they can be accessed by the TT template
860 $c->stash(books => [$c->model('DB::Book')->all]);
862 # Set the TT template to use. You will almost always want to do this
863 # in your action methods (action methods respond to user input in
865 $c->stash(template => 'books/list.tt2');
868 B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
869 above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
870 two are equivalent. Either way, C<$c-E<gt>model> returns a
871 L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
872 against the database and iterating over the set of results that is
875 We are using the C<-E<gt>all> to fetch all of the books. DBIC
876 supports a wide variety of more advanced operations to easily do
877 things like filtering and sorting the results. For example, the
878 following could be used to sort the results by descending title:
880 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
882 Some other examples are provided in
883 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
884 additional information found at L<DBIx::Class::ResultSet/search>,
885 L<DBIx::Class::Manual::FAQ/Searching>,
886 L<DBIx::Class::Manual::Intro|DBIx::Class::Manual::Intro>
887 and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
890 =head2 Test Run The Application
892 First, let's enable an environment variable that causes DBIx::Class to
893 dump the SQL statements used to access the database. This is a
894 helpful trick when you are trying to debug your database-oriented
895 code. Press C<Ctrl-C> to break out of the development server and
898 $ export DBIC_TRACE=1
899 $ script/myapp_server.pl -r
901 This assumes you are using bash as your shell -- adjust accordingly if
902 you are using a different shell (for example, under tcsh, use
903 C<setenv DBIC_TRACE 1>).
905 B<NOTE:> You can also set this in your code using
906 C<$class-E<gt>storage-E<gt>debug(1);>. See
907 L<DBIx::Class::Manual::Troubleshooting> for details (including options
908 to log to a file instead of displaying to the Catalyst development server
911 Then launch the Catalyst development server. The log output should
912 display something like:
914 $ script/myapp_server.pl -r
915 [debug] Debug messages enabled
916 [debug] Statistics enabled
917 [debug] Loaded plugins:
918 .----------------------------------------------------------------------------.
919 | Catalyst::Plugin::ConfigLoader 0.27 |
920 | Catalyst::Plugin::StackTrace 0.11 |
921 '----------------------------------------------------------------------------'
923 [debug] Loaded dispatcher "Catalyst::Dispatcher"
924 [debug] Loaded engine "Catalyst::Engine::HTTP"
925 [debug] Found home "/home/me/MyApp"
926 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
927 [debug] Loaded components:
928 .-----------------------------------------------------------------+----------.
930 +-----------------------------------------------------------------+----------+
931 | MyApp::Controller::Books | instance |
932 | MyApp::Controller::Root | instance |
933 | MyApp::Model::DB | instance |
934 | MyApp::Model::DB::Author | class |
935 | MyApp::Model::DB::Book | class |
936 | MyApp::Model::DB::BookAuthor | class |
937 | MyApp::View::HTML | instance |
938 '-----------------------------------------------------------------+----------'
940 [debug] Loaded Private actions:
941 .----------------------+--------------------------------------+--------------.
942 | Private | Class | Method |
943 +----------------------+--------------------------------------+--------------+
944 | /default | MyApp::Controller::Root | default |
945 | /end | MyApp::Controller::Root | end |
946 | /index | MyApp::Controller::Root | index |
947 | /books/index | MyApp::Controller::Books | index |
948 | /books/list | MyApp::Controller::Books | list |
949 '----------------------+--------------------------------------+--------------'
951 [debug] Loaded Path actions:
952 .-------------------------------------+--------------------------------------.
954 +-------------------------------------+--------------------------------------+
957 | /books | /books/index |
958 | /books/list | /books/list |
959 '-------------------------------------+--------------------------------------'
961 [info] MyApp powered by Catalyst 5.80020
962 You can connect to your server at http://debian:3000
964 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
965 the 'base' directory of your application, not inside the C<script>
966 directory itself or it will not be able to locate the C<myapp.db>
967 database file. You can use a fully qualified or a relative path to
968 locate the database file, but we did not specify that when we ran the
969 model helper earlier.
971 Some things you should note in the output above:
977 Catalyst::Model::DBIC::Schema dynamically created three model classes,
978 one to represent each of the three tables in our database
979 (C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
980 and C<MyApp::Model::DB::Book>).
984 The "list" action in our Books controller showed up with a path of
989 Point your browser to L<http://localhost:3000> and you should still get
990 the Catalyst welcome page.
992 Next, to view the book list, change the URL in your browser to
993 L<http://localhost:3000/books/list>. You should get a list of the five
994 books loaded by the C<myapp01.sql> script above without any formatting.
995 The rating for each book should appear on each row, but the "Author(s)"
996 column will still be blank (we will fill that in later).
998 Also notice in the output of the C<script/myapp_server.pl> that
999 DBIx::Class used the following SQL to retrieve the data:
1001 SELECT me.id, me.title, me.rating FROM book me
1003 because we enabled DBIC_TRACE.
1005 You now have the beginnings of a simple but workable web application.
1006 Continue on to future sections and we will develop the application
1010 =head1 CREATE A WRAPPER FOR THE VIEW
1012 When using TT, you can (and should) create a wrapper that will
1013 literally wrap content around each of your templates. This is
1014 certainly useful as you have one main source for changing things that
1015 will appear across your entire site/application instead of having to
1016 edit many individual files.
1019 =head2 Configure HTML.pm For The Wrapper
1021 In order to create a wrapper, you must first edit your TT view and
1022 tell it where to find your wrapper file.
1024 Edit you TT view in C<lib/MyApp/View/HTML.pm> and change it to match the
1027 __PACKAGE__->config(
1028 # Change default TT extension
1029 TEMPLATE_EXTENSION => '.tt2',
1030 # Set the location for TT files
1032 MyApp->path_to( 'root', 'src' ),
1034 # Set to 1 for detailed timer stats in your HTML as comments
1036 # This is your wrapper template located in the 'root/src'
1037 WRAPPER => 'wrapper.tt2',
1041 =head2 Create the Wrapper Template File and Stylesheet
1043 Next you need to set up your wrapper template. Basically, you'll want
1044 to take the overall layout of your site and put it into this file.
1045 For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1047 <?xml version="1.0" encoding="UTF-8"?>
1048 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1049 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
1051 <title>[% template.title or "My Catalyst App!" %]</title>
1052 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1058 [%# Your logo could go here -%]
1059 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1060 [%# Insert the page title -%]
1061 <h1>[% template.title or site.title %]</h1>
1064 <div id="bodyblock">
1068 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1069 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1071 </div><!-- end menu -->
1074 [%# Status and error messages %]
1075 <span class="message">[% status_msg %]</span>
1076 <span class="error">[% error_msg %]</span>
1077 [%# This is where TT will stick all of your template's contents. -%]
1079 </div><!-- end content -->
1080 </div><!-- end bodyblock -->
1082 <div id="footer">Copyright (c) your name goes here</div>
1083 </div><!-- end outer -->
1088 Notice the status and error message sections in the code above:
1090 <span class="status">[% status_msg %]</span>
1091 <span class="error">[% error_msg %]</span>
1093 If we set either message in the Catalyst stash (e.g.,
1094 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1095 will be displayed whenever any view used by that request is rendered.
1096 The C<message> and C<error> CSS styles can be customized to suit your
1097 needs in the C<root/static/css/main.css> file we create below.
1105 The Catalyst stash only lasts for a single HTTP request. If
1106 you need to retain information across requests you can use
1107 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
1108 Catalyst sessions in the Authentication chapter of the tutorial).
1112 Although it is beyond the scope of this tutorial, you may wish to use
1113 a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
1114 Dojo (L<http://www.dojotoolkit.org>).
1119 =head3 Create A Basic Stylesheet
1121 First create a central location for stylesheets under the static
1124 $ mkdir root/static/css
1126 Then open the file C<root/static/css/main.css> (the file referenced in
1127 the stylesheet href link of our wrapper above) and add the following
1146 background-color: #ddd;
1152 padding: 0 0 50% 5px;
1153 font-weight: normal;
1154 background-color: #ddd;
1167 You may wish to check out a "CSS Framework" like Emastic
1168 (L<http://code.google.com/p/emastic/>) as a way to quickly
1169 provide lots of high-quality CSS functionality.
1172 =head2 Test Run The Application
1174 Hit "Reload" in your web browser and you should now see a formatted
1175 version of our basic book list. (Again, the development server should
1176 have automatically restarted when you made changes to
1177 C<lib/MyApp/View/HTML.pm>. If you are not using the "-r" option, you will
1178 need to hit C<Ctrl-C> and manually restart it. Also note that the
1179 development server does I<NOT> need to restart for changes to the TT and
1180 static files we created and edited in the C<root> directory -- those
1181 updates are handled on a per-request basis.)
1183 Although our wrapper and stylesheet are obviously very simple, you
1184 should see how it allows us to control the overall look of an entire
1185 website from two central files. To add new pages to the site, just
1186 provide a template that fills in the C<content> section of our wrapper
1187 template -- the wrapper will provide the overall feel of the page.
1190 =head2 Updating the Generated DBIx::Class Result Class Files
1192 If you take a look at the Schema files automatically generated by
1193 L<DBIx::Class::Schema::Loader>, you will see that it has already defined
1194 C<has_many> and C<belongs_to> relationships on each side of our foreign
1195 keys. For example, take a look at C<lib/MyApp/Schema/Result/Book.pm> and
1196 notice the following code:
1204 Related object: L<MyApp::Schema::Result::BookAuthor>
1208 __PACKAGE__->has_many(
1210 "MyApp::Schema::Result::BookAuthor",
1211 { "foreign.book_id" => "self.id" },
1214 Each C<Book> "has_many" C<book_authors>, where C<BookAuthor> is
1215 the many-to-many table that allows each Book to have multiple
1216 Authors, and each Author to have mulitple books. The arguments
1223 C<book_authors> - The name for this relationship. DBIC will create
1224 an accessor on the C<Books> DBIC Row object with this name.
1228 C<MyApp::Schema::Result::BookAuthor> - The name of the DBIC model
1229 class referenced by this C<has_many> relationship.
1233 C<foreign.book_id> - C<book_id> is the name of the foreign key
1234 column in the I<foreign> table that points back to this table.
1238 C<self.id> - C<id> is the name of the column in I<this> table
1239 that is referenced by the foreign key.
1243 See L<DBIx::Class::Relationship/has_many> for
1244 additional information. Note that you might see a "hand coded"
1245 version of the C<has_many> relationship above expressed as:
1247 __PACKAGE__->has_many(
1249 "MyApp::Schema::Result::BookAuthor",
1253 Where the third argument is simply the name of the column in
1254 the foreign table. However, the hashref syntax used by
1255 L<DBIx::Class::Schema::Loader> is more flexible (for example,
1256 it can handle "multi-column" foreign keys).
1258 B<Note:> If you are using older versions of SQLite and related DBIC
1259 tools, you will need to manually define your C<has_many> and
1260 C<belongs_to> relationships. We recommend upgrading to the versions
1261 specified above. :-)
1263 Have a look at C<lib/MyApp/Schema/Result/BookAuthor.pm> and notice
1264 that there is a C<belongs_to> relationship defined that acts as the
1265 "mirror image" to the C<has_many> relationship we just looked at
1274 Related object: L<MyApp::Schema::Result::Book>
1278 __PACKAGE__->belongs_to(
1280 "MyApp::Schema::Result::Book",
1281 { id => "book_id" },
1282 { join_type => "LEFT" },
1285 The arguments are similar, but see
1286 L<DBIx::Class::Relationship/belongs_to> for the details.
1288 Although recent versions of SQLite and L<DBIx::Class::Schema::Loader>
1289 automatically handle the C<has_many> and C<belongs_to> relationships,
1290 C<many_to_many> relationships currently need to be manually inserted.
1291 To add a C<many_to_many> relationship, first edit
1292 C<lib/MyApp/Schema/Result/Book.pm> and add the following text below
1293 the C<# You can replace this text...> comment:
1297 # 1) Name of relationship, DBIC will create accessor with this name
1298 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1299 # 3) Name of belongs_to() relationship in model class of has_many() above
1300 # You must already have the has_many() defined to use a many_to_many().
1301 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1303 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1304 file. As with any Perl package, we need to end the last line with
1305 a statement that evaluates to C<true>. This is customarily done with
1306 C<1;> on a line by itself.
1308 The C<many_to_many> relationship is optional, but it makes it
1309 easier to map a book to its collection of authors. Without
1310 it, we would have to "walk" though the C<book_author> table as in
1311 C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
1312 will see examples on how to use DBIx::Class objects in your code soon,
1313 but note that because C<$book-E<gt>book_author> can return multiple
1314 authors, we have to use C<first> to display a single author).
1315 C<many_to_many> allows us to use the shorter
1316 C<$book-E<gt>author-E<gt>first-E<gt>last_name>. Note that you cannot
1317 define a C<many_to_many> relationship without also having the
1318 C<has_many> relationship in place.
1320 Then edit C<lib/MyApp/Schema/Result/Author.pm> and add the reverse
1321 C<many_to_many> relationship for C<Author> as follows (again, be careful
1322 to put in above the C<1;> but below the C<# DO NOT MODIFY THIS OR
1323 ANYTHING ABOVE!> comment):
1327 # 1) Name of relationship, DBIC will create accessor with this name
1328 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1329 # 3) Name of belongs_to() relationship in model class of has_many() above
1330 # You must already have the has_many() defined to use a many_to_many().
1331 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
1334 =head2 Run The Application
1336 Run the Catalyst development server script with the C<DBIC_TRACE> option
1337 (it might still be enabled from earlier in the tutorial, but here is an
1338 alternate way to specify the trace option just in case):
1340 $ DBIC_TRACE=1 script/myapp_server.pl -r
1342 Make sure that the application loads correctly and that you see the
1343 three dynamically created model class (one for each of the
1344 Result Classes we created).
1346 Then hit the URL L<http://localhost:3000/books/list> with your browser
1347 and be sure that the book list still displays correctly.
1349 B<Note:> You will not see the authors yet because the view does not yet
1350 use the new relations. Read on to the next section where we update the
1351 template to do that.
1354 =head1 UPDATING THE VIEW
1356 Let's add a new column to our book list page that takes advantage of
1357 the relationship information we manually added to our schema files in
1358 the previous section. Edit C<root/src/books/list.tt2> and replace
1359 the "empty" table cell "<td></td>" with the following:
1363 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1364 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1365 [% # loop in 'side effect notation' to load just the last names of the -%]
1366 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
1367 [% # a value, so nothing will be printed here. But, if you have something -%]
1368 [% # in TT that does return a value and you don't want it printed, you -%]
1369 [% # 1) assign it to a bogus value, or -%]
1370 [% # 2) use the CALL keyword to call it and discard the return value. -%]
1371 [% tt_authors = [ ];
1372 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1373 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1374 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1375 ([% tt_authors.size | html %])
1376 [% # Use another TT vmethod to join & print the names & comma separators -%]
1377 [% tt_authors.join(', ') | html %]
1381 B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1382 possible out of your views. This kind of logic belongs in your model
1383 (the same goes for controllers -- keep them as "thin" as possible and
1384 push all of the "complicated code" out to your model objects). Avoid
1385 code like you see in the previous example -- we are only using it here
1386 to show some extra features in TT until we get to the more advanced
1387 model features we will see in Chapter 4 (see
1388 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1390 Then hit "Reload" in your browser (note that you don't need to reload
1391 the development server or use the C<-r> option when updating TT
1392 templates) and you should now see the number of authors each book has
1393 along with a comma-separated list of the authors' last names. (If you
1394 didn't leave the development server running from the previous step,
1395 you will obviously need to start it before you can refresh your
1398 If you are still running the development server with C<DBIC_TRACE>
1399 enabled, you should also now see five more C<SELECT> statements in the
1400 debug output (one for each book as the authors are being retrieved by
1403 SELECT me.id, me.title, me.rating FROM book me:
1404 SELECT author.id, author.first_name, author.last_name FROM book_author me
1405 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '1'
1406 SELECT author.id, author.first_name, author.last_name FROM book_author me
1407 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '2'
1408 SELECT author.id, author.first_name, author.last_name FROM book_author me
1409 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '3'
1410 SELECT author.id, author.first_name, author.last_name FROM book_author me
1411 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '4'
1412 SELECT author.id, author.first_name, author.last_name FROM book_author me
1413 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '5'
1415 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1416 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1417 and > and avoid various types of dangerous hacks against your
1418 application. In a real application, you would probably want to put
1419 "| html" at the end of every field where a user has control over the
1420 information that can appear in that field (and can therefore inject
1421 markup or code if you don't "neutralize" those fields). In addition to
1422 "| html", Template Toolkit has a variety of other useful filters that
1423 can found in the documentation for
1424 L<Template::Filters|Template::Filters>.
1427 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1429 In some situations, it can be useful to run your application and
1430 display a page without using a browser. Catalyst lets you do this
1431 using the C<scripts/myapp_test.pl> script. Just supply the URL you
1432 wish to display and it will run that request through the normal
1433 controller dispatch logic and use the appropriate view to render the
1434 output (obviously, complex pages may dump a lot of text to your
1435 terminal window). For example, if you type:
1437 $ script/myapp_test.pl "/books/list"
1439 You should get the same text as if you visited
1440 L<http://localhost:3000/books/list> with the normal development server
1441 and asked your browser to view the page source.
1444 =head1 OPTIONAL INFORMATION
1446 B<NOTE: The rest of this chapter of the tutorial is optional. You can
1447 skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
1451 =head2 Using 'RenderView' for the Default View
1453 Once your controller logic has processed the request from a user, it
1454 forwards processing to your view in order to generate the appropriate
1455 response output. Catalyst uses
1456 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1457 default to automatically perform this operation. If you look in
1458 C<lib/MyApp/Controller/Root.pm>, you should see the empty
1459 definition for the C<sub end> method:
1461 sub end : ActionClass('RenderView') {}
1463 The following bullet points provide a quick overview of the
1464 C<RenderView> process:
1470 C<Root.pm> is designed to hold application-wide logic.
1474 At the end of a given user request, Catalyst will call the most specific
1475 C<end> method that's appropriate. For example, if the controller for a
1476 request has an C<end> method defined, it will be called. However, if
1477 the controller does not define a controller-specific C<end> method, the
1478 "global" C<end> method in C<Root.pm> will be called.
1482 Because the definition includes an C<ActionClass> attribute, the
1483 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1484 will be executed B<after> any code inside the definition of C<sub end>
1485 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1486 for more information on C<ActionClass>.
1490 Because C<sub end> is empty, this effectively just runs the default
1491 logic in C<RenderView>. However, you can easily extend the
1492 C<RenderView> logic by adding your own code inside the empty method body
1493 (C<{}>) created by the Catalyst Helpers when we first ran the
1494 C<catalyst.pl> to initialize our application. See
1495 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1496 detailed information on how to extend C<RenderView> in C<sub end>.
1501 =head2 RenderView's "dump_info" Feature
1503 One of the nice features of C<RenderView> is that it automatically
1504 allows you to add C<dump_info=1> to the end of any URL for your
1505 application and it will force the display of the "exception dump"
1506 screen to the client browser. You can try this out by pointing
1507 your browser to this URL:
1509 http://localhost:3000/books/list?dump_info=1
1511 You should get a page with the following message at the top:
1513 Caught exception in MyApp::Controller::Root->end "Forced debug -
1514 Scrubbed output at /usr/share/perl5/Catalyst/Action/RenderView.pm line 46."
1516 Along with a summary of your application's state at the end of the
1517 processing for that request. The "Stash" section should show a
1518 summarized version of the DBIC book model objects. If desired, you
1519 can adjust the summarization logic (called "scrubbing" logic) -- see
1520 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for
1523 Note that you shouldn't need to worry about "normal clients" using
1524 this technique to "reverse engineer" your application -- C<RenderView>
1525 only supports the C<dump_info=1> feature when your application is
1526 running in C<-Debug> mode (something you won't do once you have your
1527 application deployed in production).
1530 =head2 Using The Default Template Name
1532 By default, C<Catalyst::View::TT> will look for a template that uses the
1533 same name as your controller action, allowing you to save the step of
1534 manually specifying the template name in each action. For example, this
1535 would allow us to remove the
1536 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1537 C<list> action in the Books controller. Open
1538 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1539 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1544 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1549 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1550 # 'Context' that's used to 'glue together' the various components
1551 # that make up the application
1552 my ($self, $c) = @_;
1554 # Retrieve all of the book records as book model objects and store in the
1555 # stash where they can be accessed by the TT template
1556 $c->stash(books => [$c->model('DB::Book')->all]);
1558 # Set the TT template to use. You will almost always want to do this
1559 # in your action methods (actions methods respond to user input in
1560 # your controllers).
1561 #$c->stash(template => 'books/list.tt2');
1565 You should now be able to access the L<http://localhost:3000/books/list>
1568 B<NOTE:> Please note that if you use the default template technique,
1569 you will B<not> be able to use either the C<$c-E<gt>forward> or
1570 the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1571 Chapter 9 of the Tutorial).
1573 B<IMPORTANT:> Make sure that you do NOT skip the following section
1574 before continuing to the next chapter 4 Basic CRUD.
1577 =head2 Return To A Manually Specified Template
1579 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1580 later in the tutorial, you should remove the comment from the
1581 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1583 $c->stash(template => 'books/list.tt2');
1585 Then delete the C<TEMPLATE_EXTENSION> line in
1586 C<lib/MyApp/View/HTML.pm>.
1588 Check the L<http://localhost:3000/books/list> URL in your browser.
1589 It should look the same manner as with earlier sections.
1594 Kennedy Clark, C<hkclark@gmail.com>
1596 Please report any errors, issues or suggestions to the author. The
1597 most recent version of the Catalyst Tutorial can be found at
1598 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
1600 Copyright 2006-2010, Kennedy Clark, under Creative Commons License
1601 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).