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 temporarily 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" built-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
453 something similar to the following:
456 TEMPLATE_EXTENSION => '.tt',
460 And update it to match:
463 # Change default TT extension
464 TEMPLATE_EXTENSION => '.tt2',
468 This changes the default extension for Template Toolkit from '.tt' to
471 You can also configure components in your application class. For example,
472 Edit C<lib/MyApp.pm> and you should see that the default:
476 Above this, add config:
480 #Set the location for TT files
482 __PACKAGE__->path_to( 'root', 'src' ),
486 # This line was here already
489 This changes the base directory for your template files from
490 C<root> to C<root/src>.
492 The reason to do this outside the C<lib/MyApp/View/HTML.pm> file
493 is that the template path is found with the C<path_to> method,
494 to get a path relative to the application root (no matter where it
495 is installed), but this requires the application to be loaded...
497 Trying to set this setting in the view means that you have a chicken
498 and egg problem, in that the view requires the application to be loaded,
499 but loading the application loads the view.
501 Putting the configuration which depends on the application class into
502 that class is the neatest way to avoid this issue.
504 Please stick with the settings above for the duration of the
505 tutorial, but feel free to use whatever options you desire in your
506 applications (as with most things Perl, there's more than one way to
509 B<Note:> We will use C<root/src> as the base directory for our
510 template files, with a full naming convention of
511 C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
512 use C<root/> as the base (with a full filename pattern of
513 C<root/_controller_name_/_action_name_.tt2>).
515 =head2 Create a TT Template Page
517 First create a directory for book-related TT templates:
519 $ mkdir -p root/src/books
521 Then create C<root/src/books/list.tt2> in your editor and enter:
523 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
524 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
525 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
526 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
528 [% # Provide a title -%]
529 [% META title = 'Book List' -%]
532 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
533 [% # Display each book in a table row %]
534 [% FOREACH book IN books -%]
536 <td>[% book.title %]</td>
537 <td>[% book.rating %]</td>
543 As indicated by the inline comments above, the C<META title> line uses
544 TT's META feature to provide a title to the "wrapper" that we will
545 create later. Meanwhile, the C<FOREACH> loop iterates through each
546 C<book> model object and prints the C<title> and C<rating> fields.
548 The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
549 supports a wide variety of directives for "calling" other files,
550 looping, conditional logic, etc. In general, TT simplifies the usual
551 range of Perl operators down to the single dot (".") operator. This
552 applies to operations as diverse as method calls, hash lookups, and list
554 L<http://search.cpan.org/perldoc?Template::Manual::Variables> for
555 details and examples). In addition to the usual L<Template> module Pod
556 documentation, you can access the TT manual at
557 L<http://search.cpan.org/perldoc?Template::Manual>.
559 B<TIP:> While you can build all sorts of complex logic into your TT
560 templates, you should in general keep the "code" part of your
561 templates as simple as possible. If you need more complex logic,
562 create helper methods in your model that abstract out a set of code
563 into a single call from your TT template. (Note that the same is true
564 of your controller logic as well -- complex sections of code in your
565 controllers should often be pulled out and placed into your model
566 objects.) In Chapter 4 of the tutorial we will explore some extremely
567 helpful and powerful features of L<DBIx::Class> that allow you to pull
568 code out of your views and controllers and place it where it
569 rightfully belongs in a model class.
572 =head2 Test Run The Application
574 To test your work so far, first start the development server:
576 $ script/myapp_server.pl -r
578 Then point your browser to L<http://localhost:3000> and you should
579 still get the Catalyst welcome page. Next, change the URL in your
580 browser to L<http://localhost:3000/books/list>. If you have
581 everything working so far, you should see a web page that displays
582 nothing other than our column headers for "Title", "Rating", and
583 "Author(s)" -- we will not see any books until we get the database and
586 If you run into problems getting your application to run correctly, it
587 might be helpful to refer to some of the debugging techniques covered in
588 the L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> chapter of the
592 =head1 CREATE A SQLITE DATABASE
594 In this step, we make a text file with the required SQL commands to
595 create a database table and load some sample data. We will use
596 SQLite (L<http://www.sqlite.org>), a popular database that is
597 lightweight and easy to use. Be sure to get at least version 3. Open
598 C<myapp01.sql> in your editor and enter:
601 -- Create a very simple database to hold book and author information
603 PRAGMA foreign_keys = ON;
605 id INTEGER PRIMARY KEY,
609 -- 'book_author' is a many-to-many join table between books & authors
610 CREATE TABLE book_author (
611 book_id INTEGER REFERENCES book(id) ON DELETE CASCADE ON UPDATE CASCADE,
612 author_id INTEGER REFERENCES author(id) ON DELETE CASCADE ON UPDATE CASCADE,
613 PRIMARY KEY (book_id, author_id)
615 CREATE TABLE author (
616 id INTEGER PRIMARY KEY,
621 --- Load some sample data
623 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
624 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
625 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
626 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
627 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
628 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
629 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
630 INSERT INTO author VALUES (3, 'Christian', 'Degu');
631 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
632 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
633 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
634 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
635 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
636 INSERT INTO book_author VALUES (1, 1);
637 INSERT INTO book_author VALUES (1, 2);
638 INSERT INTO book_author VALUES (1, 3);
639 INSERT INTO book_author VALUES (2, 4);
640 INSERT INTO book_author VALUES (3, 5);
641 INSERT INTO book_author VALUES (4, 6);
642 INSERT INTO book_author VALUES (4, 7);
643 INSERT INTO book_author VALUES (5, 8);
645 Then use the following command to build a C<myapp.db> SQLite database:
647 $ sqlite3 myapp.db < myapp01.sql
649 If you need to create the database more than once, you probably want to
650 issue the C<rm myapp.db> command to delete the database before you use
651 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
653 Once the C<myapp.db> database file has been created and initialized, you
654 can use the SQLite command line environment to do a quick dump of the
658 SQLite version 3.6.22
659 Enter ".help" for instructions
660 Enter SQL statements terminated with a ";"
661 sqlite> select * from book;
662 1|CCSP SNRS Exam Certification Guide|5
663 2|TCP/IP Illustrated, Volume 1|5
664 3|Internetworking with TCP/IP Vol.1|4
666 5|Designing with Web Standards|5
672 $ sqlite3 myapp.db "select * from book"
673 1|CCSP SNRS Exam Certification Guide|5
674 2|TCP/IP Illustrated, Volume 1|5
675 3|Internetworking with TCP/IP Vol.1|4
677 5|Designing with Web Standards|5
679 As with most other SQL tools, if you are using the full "interactive"
680 environment you need to terminate your SQL commands with a ";" (it's not
681 required if you do a single SQL statement on the command line). Use
682 ".q" to exit from SQLite from the SQLite interactive mode and return to
683 your OS command prompt.
685 Please note that here we have chosen to use 'singular' table names. This is
686 because the default inflection code for older versions of
687 L<DBIx::Class::Schema::Loader> does NOT handle plurals. There has been much
688 philosophical discussion on whether table names should be plural or singular.
689 There is no one correct answer, as long as one makes a choice and remains
690 consistent with it. If you prefer plural table names (e.g. you think that they
691 are easier to read) then see the documentation in
692 L<DBIx::Class::Schema::Loader::Base/naming> (version 0.05 or greater).
694 For using other databases, such as PostgreSQL or MySQL, see
695 L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices>.
698 =head1 DATABASE ACCESS WITH DBIx::Class
700 Catalyst can be used with virtually any form of datastore available
701 via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
702 can be used to access databases through the traditional Perl L<DBI>
703 interface or you can use a model to access files of any type on the
704 filesystem. However, most Catalyst applications use some form of
705 object-relational mapping (ORM) technology to create objects
706 associated with tables in a relational database. Matt Trout's
707 L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
708 as the Perl-based ORM technology of choice. Most new Catalyst
709 applications rely on DBIx::Class, as will this tutorial.
711 Although DBIx::Class has included support for a C<create=dynamic> mode
712 to automatically read the database structure every time the
713 application starts, its use is no longer recommended. While it can
714 make for "flashy" demos, the use of the C<create=static> mode we use
715 below can be implemented just as quickly and provides many advantages
716 (such as the ability to add your own methods to the overall DBIC
717 framework, a technique that we see in Chapter 4).
720 =head2 Make Sure You Have a Recent Version of the DBIx::Class Model
722 First, let's be sure we have a recent version of the DBIC helper,
723 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, so
724 that we can take advantage of some recent enhancements in how
725 foreign keys are handled with SQLite. To check your version,
728 $ perl -MCatalyst::Model::DBIC::Schema -e \
729 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
732 Please note the '\' above. Depending on your environment, you might
733 be able to cut and paste the text as shown or need to remove the '\'
734 character to that the command is all on a single line.
736 If you are following along in Debian 5, you should have version 0.40 or
737 higher (shown above as "0.4" with the tailing zero removed). If you have
738 less than v0.39, you will need to run this command to install it
741 $ sudo cpan Catalyst::Model::DBIC::Schema
743 And re-run the version print command to verify that you are now at
746 In addition, since we are using SQLite's foreign key support here,
747 please be sure that you use version C<1.27> of L<DBD::SQLite> or later:
749 $ perl -MDBD::SQLite -e 'print "$DBD::SQLite::VERSION\n"'
752 Upgrade if you are not at version C<1.27> or higher.
755 =head2 Create Static DBIx::Class Schema Files
757 Before you continue, make sure your C<myapp.db> database file is in
758 the application's topmost directory. Now use the model helper with
759 the C<create=static> option to read the database with
760 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
761 automatically build the required files for us:
763 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
764 create=static dbi:SQLite:myapp.db \
765 on_connect_do="PRAGMA foreign_keys = ON"
766 exists "/home/me/MyApp/script/../lib/MyApp/Model"
767 exists "/home/me/MyApp/script/../t"
768 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
769 Schema dump completed.
770 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
771 created "/home/me/MyApp/script/../t/model_DB.t"
773 Please note the '\' above. Depending on your environment, you might
774 be able to cut and paste the text as shown or need to remove the '\'
775 character to that the command is all on a single line.
777 The C<script/myapp_create.pl> command breaks down like this:
783 C<DB> is the name of the model class to be created by the helper in
788 C<DBIC::Schema> is the type of the model to create.
792 C<MyApp::Schema> is the name of the DBIC schema file written to
793 C<lib/MyApp/Schema.pm>.
797 C<create=static> causes
798 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
799 load the schema as it runs and then write that information out
804 C<dbi:SQLite:myapp.db> is the standard DBI connect string
809 And finally, the C<on_connect_do> string requests that
810 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> create
811 foreign key relationships for us (this is not needed for databases such
812 as PostgreSQL and MySQL, but is required for SQLite). If you take a look
813 at C<lib/MyApp/Model/DB.pm>, you will see that the SQLite pragma is
814 propogated to the Model, so that SQLite's recent (and optional) foreign
815 key enforcement is enabled at the start of every database connection.
821 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
822 only contains a call to the C<load_namespaces> method. You will also
823 find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
824 has a subdirectory called "Result". This "Result" subdirectory then
825 has files named according to each of the tables in our simple database
826 (C<Author.pm>, C<BookAuthor.pm>, and C<Book.pm>). These three
827 files are called "Result Classes" in DBIx::Class nomenclature. Although the
828 Result Class files are named after tables in our database, the classes
829 correspond to the I<row-level data> that is returned by DBIC (more on
830 this later, especially in
831 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
833 The idea with the Result Source files created under
834 C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
835 edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
836 warning. If you place all of your changes below that point in the
837 file, you can regenerate the automatically created information at the
838 top of each file should your database structure get updated.
840 Also note the "flow" of the model information across the various files
841 and directories. Catalyst will initially load the model from
842 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
843 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the
844 call to C<load_namespaces> in C<Schema.pm> will load each of the
845 "Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
846 The final outcome is that Catalyst will dynamically create three
847 table-specific Catalyst models every time the application starts (you
848 can see these three model files listed in the debug output generated
849 when you launch the application).
851 B<NOTE:> Older versions of
852 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
853 deprecated DBIx::Class C<load_classes> technique instead of the newer
854 C<load_namespaces>. For new applications, please try to use
855 C<load_namespaces> since it more easily supports a very useful DBIC
856 technique called "ResultSet Classes." If you need to convert an
857 existing application from "load_classes" to "load_namespaces," you can
858 use this process to automate the migration, but first make sure you have
859 version C<0.39> of L<Catalyst::Model::DBIC::Schema> and
860 L<DBIx::Class::Schema::Loader> version C<0.05000> or later.
862 $ # Re-run the helper to upgrade for you
863 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
864 create=static naming=current use_namespaces=1 \
865 dbi:SQLite:myapp.db \
866 on_connect_do="PRAGMA foreign_keys = ON"
869 =head1 ENABLE THE MODEL IN THE CONTROLLER
871 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
872 left disabled earlier so that your version matches the following (un-
873 comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
874 and delete the next 2 lines):
878 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
883 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
884 # 'Context' that's used to 'glue together' the various components
885 # that make up the application
888 # Retrieve all of the book records as book model objects and store
889 # in the stash where they can be accessed by the TT template
890 $c->stash(books => [$c->model('DB::Book')->all]);
892 # Set the TT template to use. You will almost always want to do this
893 # in your action methods (action methods respond to user input in
895 $c->stash(template => 'books/list.tt2');
898 B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
899 above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
900 two are equivalent. Either way, C<$c-E<gt>model> returns a
901 L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
902 against the database and iterating over the set of results that is
905 We are using the C<-E<gt>all> to fetch all of the books. DBIC
906 supports a wide variety of more advanced operations to easily do
907 things like filtering and sorting the results. For example, the
908 following could be used to sort the results by descending title:
910 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
912 Some other examples are provided in
913 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
914 additional information found at L<DBIx::Class::ResultSet/search>,
915 L<DBIx::Class::Manual::FAQ/Searching>,
916 L<DBIx::Class::Manual::Intro|DBIx::Class::Manual::Intro>
917 and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
920 =head2 Test Run The Application
922 First, let's enable an environment variable that causes DBIx::Class to
923 dump the SQL statements used to access the database. This is a
924 helpful trick when you are trying to debug your database-oriented
925 code. Press C<Ctrl-C> to break out of the development server and
928 $ export DBIC_TRACE=1
929 $ script/myapp_server.pl -r
931 This assumes you are using bash as your shell -- adjust accordingly if
932 you are using a different shell (for example, under tcsh, use
933 C<setenv DBIC_TRACE 1>).
935 B<NOTE:> You can also set this in your code using
936 C<$class-E<gt>storage-E<gt>debug(1);>. See
937 L<DBIx::Class::Manual::Troubleshooting> for details (including options
938 to log to a file instead of displaying to the Catalyst development server
941 Then launch the Catalyst development server. The log output should
942 display something like:
944 $ script/myapp_server.pl -r
945 [debug] Debug messages enabled
946 [debug] Statistics enabled
947 [debug] Loaded plugins:
948 .----------------------------------------------------------------------------.
949 | Catalyst::Plugin::ConfigLoader 0.27 |
950 | Catalyst::Plugin::StackTrace 0.11 |
951 '----------------------------------------------------------------------------'
953 [debug] Loaded dispatcher "Catalyst::Dispatcher"
954 [debug] Loaded engine "Catalyst::Engine::HTTP"
955 [debug] Found home "/home/me/MyApp"
956 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
957 [debug] Loaded components:
958 .-----------------------------------------------------------------+----------.
960 +-----------------------------------------------------------------+----------+
961 | MyApp::Controller::Books | instance |
962 | MyApp::Controller::Root | instance |
963 | MyApp::Model::DB | instance |
964 | MyApp::Model::DB::Author | class |
965 | MyApp::Model::DB::Book | class |
966 | MyApp::Model::DB::BookAuthor | class |
967 | MyApp::View::HTML | instance |
968 '-----------------------------------------------------------------+----------'
970 [debug] Loaded Private actions:
971 .----------------------+--------------------------------------+--------------.
972 | Private | Class | Method |
973 +----------------------+--------------------------------------+--------------+
974 | /default | MyApp::Controller::Root | default |
975 | /end | MyApp::Controller::Root | end |
976 | /index | MyApp::Controller::Root | index |
977 | /books/index | MyApp::Controller::Books | index |
978 | /books/list | MyApp::Controller::Books | list |
979 '----------------------+--------------------------------------+--------------'
981 [debug] Loaded Path actions:
982 .-------------------------------------+--------------------------------------.
984 +-------------------------------------+--------------------------------------+
987 | /books | /books/index |
988 | /books/list | /books/list |
989 '-------------------------------------+--------------------------------------'
991 [info] MyApp powered by Catalyst 5.80020
992 You can connect to your server at http://debian:3000
994 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
995 the 'base' directory of your application, not inside the C<script>
996 directory itself or it will not be able to locate the C<myapp.db>
997 database file. You can use a fully qualified or a relative path to
998 locate the database file, but we did not specify that when we ran the
999 model helper earlier.
1001 Some things you should note in the output above:
1007 Catalyst::Model::DBIC::Schema dynamically created three model classes,
1008 one to represent each of the three tables in our database
1009 (C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
1010 and C<MyApp::Model::DB::Book>).
1014 The "list" action in our Books controller showed up with a path of
1019 Point your browser to L<http://localhost:3000> and you should still get
1020 the Catalyst welcome page.
1022 Next, to view the book list, change the URL in your browser to
1023 L<http://localhost:3000/books/list>. You should get a list of the five
1024 books loaded by the C<myapp01.sql> script above without any formatting.
1025 The rating for each book should appear on each row, but the "Author(s)"
1026 column will still be blank (we will fill that in later).
1028 Also notice in the output of the C<script/myapp_server.pl> that
1029 DBIx::Class used the following SQL to retrieve the data:
1031 SELECT me.id, me.title, me.rating FROM book me
1033 because we enabled DBIC_TRACE.
1035 You now have the beginnings of a simple but workable web application.
1036 Continue on to future sections and we will develop the application
1040 =head1 CREATE A WRAPPER FOR THE VIEW
1042 When using TT, you can (and should) create a wrapper that will
1043 literally wrap content around each of your templates. This is
1044 certainly useful as you have one main source for changing things that
1045 will appear across your entire site/application instead of having to
1046 edit many individual files.
1049 =head2 Configure HTML.pm For The Wrapper
1051 In order to create a wrapper, you must first edit your TT view and
1052 tell it where to find your wrapper file.
1054 Edit your TT view in C<lib/MyApp/View/HTML.pm> and change it to match the
1057 __PACKAGE__->config(
1058 # Change default TT extension
1059 TEMPLATE_EXTENSION => '.tt2',
1060 # Set the location for TT files
1062 MyApp->path_to( 'root', 'src' ),
1064 # Set to 1 for detailed timer stats in your HTML as comments
1066 # This is your wrapper template located in the 'root/src'
1067 WRAPPER => 'wrapper.tt2',
1071 =head2 Create the Wrapper Template File and Stylesheet
1073 Next you need to set up your wrapper template. Basically, you'll want
1074 to take the overall layout of your site and put it into this file.
1075 For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1077 <?xml version="1.0" encoding="UTF-8"?>
1078 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1079 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
1081 <title>[% template.title or "My Catalyst App!" %]</title>
1082 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1088 [%# Your logo could go here -%]
1089 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1090 [%# Insert the page title -%]
1091 <h1>[% template.title or site.title %]</h1>
1094 <div id="bodyblock">
1098 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1099 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1101 </div><!-- end menu -->
1104 [%# Status and error messages %]
1105 <span class="message">[% status_msg %]</span>
1106 <span class="error">[% error_msg %]</span>
1107 [%# This is where TT will stick all of your template's contents. -%]
1109 </div><!-- end content -->
1110 </div><!-- end bodyblock -->
1112 <div id="footer">Copyright (c) your name goes here</div>
1113 </div><!-- end outer -->
1118 Notice the status and error message sections in the code above:
1120 <span class="status">[% status_msg %]</span>
1121 <span class="error">[% error_msg %]</span>
1123 If we set either message in the Catalyst stash (e.g.,
1124 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1125 will be displayed whenever any view used by that request is rendered.
1126 The C<message> and C<error> CSS styles can be customized to suit your
1127 needs in the C<root/static/css/main.css> file we create below.
1135 The Catalyst stash only lasts for a single HTTP request. If
1136 you need to retain information across requests you can use
1137 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
1138 Catalyst sessions in the Authentication chapter of the tutorial).
1142 Although it is beyond the scope of this tutorial, you may wish to use
1143 a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
1144 Dojo (L<http://www.dojotoolkit.org>).
1149 =head3 Create A Basic Stylesheet
1151 First create a central location for stylesheets under the static
1154 $ mkdir root/static/css
1156 Then open the file C<root/static/css/main.css> (the file referenced in
1157 the stylesheet href link of our wrapper above) and add the following
1176 background-color: #ddd;
1182 padding: 0 0 50% 5px;
1183 font-weight: normal;
1184 background-color: #ddd;
1197 You may wish to check out a "CSS Framework" like Emastic
1198 (L<http://code.google.com/p/emastic/>) as a way to quickly
1199 provide lots of high-quality CSS functionality.
1202 =head2 Test Run The Application
1204 Hit "Reload" in your web browser and you should now see a formatted
1205 version of our basic book list. (Again, the development server should
1206 have automatically restarted when you made changes to
1207 C<lib/MyApp/View/HTML.pm>. If you are not using the "-r" option, you will
1208 need to hit C<Ctrl-C> and manually restart it. Also note that the
1209 development server does I<NOT> need to restart for changes to the TT and
1210 static files we created and edited in the C<root> directory -- those
1211 updates are handled on a per-request basis.)
1213 Although our wrapper and stylesheet are obviously very simple, you
1214 should see how it allows us to control the overall look of an entire
1215 website from two central files. To add new pages to the site, just
1216 provide a template that fills in the C<content> section of our wrapper
1217 template -- the wrapper will provide the overall feel of the page.
1220 =head2 Updating the Generated DBIx::Class Result Class Files
1222 If you take a look at the Schema files automatically generated by
1223 L<DBIx::Class::Schema::Loader>, you will see that it has already defined
1224 C<has_many> and C<belongs_to> relationships on each side of our foreign
1225 keys. For example, take a look at C<lib/MyApp/Schema/Result/Book.pm> and
1226 notice the following code:
1234 Related object: L<MyApp::Schema::Result::BookAuthor>
1238 __PACKAGE__->has_many(
1240 "MyApp::Schema::Result::BookAuthor",
1241 { "foreign.book_id" => "self.id" },
1244 Each C<Book> "has_many" C<book_authors>, where C<BookAuthor> is
1245 the many-to-many table that allows each Book to have multiple
1246 Authors, and each Author to have mulitple books. The arguments
1253 C<book_authors> - The name for this relationship. DBIC will create
1254 an accessor on the C<Books> DBIC Row object with this name.
1258 C<MyApp::Schema::Result::BookAuthor> - The name of the DBIC model
1259 class referenced by this C<has_many> relationship.
1263 C<foreign.book_id> - C<book_id> is the name of the foreign key
1264 column in the I<foreign> table that points back to this table.
1268 C<self.id> - C<id> is the name of the column in I<this> table
1269 that is referenced by the foreign key.
1273 See L<DBIx::Class::Relationship/has_many> for
1274 additional information. Note that you might see a "hand coded"
1275 version of the C<has_many> relationship above expressed as:
1277 __PACKAGE__->has_many(
1279 "MyApp::Schema::Result::BookAuthor",
1283 Where the third argument is simply the name of the column in
1284 the foreign table. However, the hashref syntax used by
1285 L<DBIx::Class::Schema::Loader> is more flexible (for example,
1286 it can handle "multi-column" foreign keys).
1288 B<Note:> If you are using older versions of SQLite and related DBIC
1289 tools, you will need to manually define your C<has_many> and
1290 C<belongs_to> relationships. We recommend upgrading to the versions
1291 specified above. :-)
1293 Have a look at C<lib/MyApp/Schema/Result/BookAuthor.pm> and notice
1294 that there is a C<belongs_to> relationship defined that acts as the
1295 "mirror image" to the C<has_many> relationship we just looked at
1304 Related object: L<MyApp::Schema::Result::Book>
1308 __PACKAGE__->belongs_to(
1310 "MyApp::Schema::Result::Book",
1311 { id => "book_id" },
1312 { join_type => "LEFT" },
1315 The arguments are similar, but see
1316 L<DBIx::Class::Relationship/belongs_to> for the details.
1318 Although recent versions of SQLite and L<DBIx::Class::Schema::Loader>
1319 automatically handle the C<has_many> and C<belongs_to> relationships,
1320 C<many_to_many> relationship bridges (not technically a relationship)
1321 currently need to be manually inserted.
1322 To add a C<many_to_many> relationship bridge, first edit
1323 C<lib/MyApp/Schema/Result/Book.pm> and add the following text below
1324 the C<# You can replace this text...> comment:
1328 # 1) Name of relationship bridge, DBIC will create accessor with this name
1329 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1330 # 3) Name of belongs_to() relationship in model class of has_many() above
1331 # You must already have the has_many() defined to use a many_to_many().
1332 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1334 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1335 file. As with any Perl package, we need to end the last line with
1336 a statement that evaluates to C<true>. This is customarily done with
1337 C<1;> on a line by itself.
1339 The C<many_to_many> relationship bridge is optional, but it makes it
1340 easier to map a book to its collection of authors. Without
1341 it, we would have to "walk" through the C<book_author> table as in
1342 C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
1343 will see examples on how to use DBIx::Class objects in your code soon,
1344 but note that because C<$book-E<gt>book_author> can return multiple
1345 authors, we have to use C<first> to display a single author).
1346 C<many_to_many> allows us to use the shorter
1347 C<$book-E<gt>author-E<gt>first-E<gt>last_name>. Note that you cannot
1348 define a C<many_to_many> relationship bridge without also having the
1349 C<has_many> relationship in place.
1351 Then edit C<lib/MyApp/Schema/Result/Author.pm> and add the reverse
1352 C<many_to_many> relationship bridge for C<Author> as follows (again, be careful
1353 to put in above the C<1;> but below the C<# DO NOT MODIFY THIS OR
1354 ANYTHING ABOVE!> comment):
1358 # 1) Name of relationship bridge, DBIC will create accessor with this name
1359 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1360 # 3) Name of belongs_to() relationship in model class of has_many() above
1361 # You must already have the has_many() defined to use a many_to_many().
1362 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
1365 =head2 Run The Application
1367 Run the Catalyst development server script with the C<DBIC_TRACE> option
1368 (it might still be enabled from earlier in the tutorial, but here is an
1369 alternate way to specify the trace option just in case):
1371 $ DBIC_TRACE=1 script/myapp_server.pl -r
1373 Make sure that the application loads correctly and that you see the
1374 three dynamically created model class (one for each of the
1375 Result Classes we created).
1377 Then hit the URL L<http://localhost:3000/books/list> with your browser
1378 and be sure that the book list still displays correctly.
1380 B<Note:> You will not see the authors yet because the view does not yet
1381 use the new relations. Read on to the next section where we update the
1382 template to do that.
1385 =head1 UPDATING THE VIEW
1387 Let's add a new column to our book list page that takes advantage of
1388 the relationship information we manually added to our schema files in
1389 the previous section. Edit C<root/src/books/list.tt2> and replace
1390 the "empty" table cell "<td></td>" with the following:
1394 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1395 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1396 [% # loop in 'side effect notation' to load just the last names of the -%]
1397 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
1398 [% # a value, so nothing will be printed here. But, if you have something -%]
1399 [% # in TT that does return a value and you don't want it printed, you -%]
1400 [% # 1) assign it to a bogus value, or -%]
1401 [% # 2) use the CALL keyword to call it and discard the return value. -%]
1402 [% tt_authors = [ ];
1403 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1404 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1405 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1406 ([% tt_authors.size | html %])
1407 [% # Use another TT vmethod to join & print the names & comma separators -%]
1408 [% tt_authors.join(', ') | html %]
1412 B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1413 possible out of your views. This kind of logic belongs in your model
1414 (the same goes for controllers -- keep them as "thin" as possible and
1415 push all of the "complicated code" out to your model objects). Avoid
1416 code like you see in the previous example -- we are only using it here
1417 to show some extra features in TT until we get to the more advanced
1418 model features we will see in Chapter 4 (see
1419 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1421 Then hit "Reload" in your browser (note that you don't need to reload
1422 the development server or use the C<-r> option when updating TT
1423 templates) and you should now see the number of authors each book has
1424 along with a comma-separated list of the authors' last names. (If you
1425 didn't leave the development server running from the previous step,
1426 you will obviously need to start it before you can refresh your
1429 If you are still running the development server with C<DBIC_TRACE>
1430 enabled, you should also now see five more C<SELECT> statements in the
1431 debug output (one for each book as the authors are being retrieved by
1434 SELECT me.id, me.title, me.rating FROM book me:
1435 SELECT author.id, author.first_name, author.last_name FROM book_author me
1436 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '1'
1437 SELECT author.id, author.first_name, author.last_name FROM book_author me
1438 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '2'
1439 SELECT author.id, author.first_name, author.last_name FROM book_author me
1440 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '3'
1441 SELECT author.id, author.first_name, author.last_name FROM book_author me
1442 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '4'
1443 SELECT author.id, author.first_name, author.last_name FROM book_author me
1444 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '5'
1446 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1447 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1448 and > and avoid various types of dangerous hacks against your
1449 application. In a real application, you would probably want to put
1450 "| html" at the end of every field where a user has control over the
1451 information that can appear in that field (and can therefore inject
1452 markup or code if you don't "neutralize" those fields). In addition to
1453 "| html", Template Toolkit has a variety of other useful filters that
1454 can found in the documentation for
1455 L<Template::Filters|Template::Filters>.
1458 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1460 In some situations, it can be useful to run your application and
1461 display a page without using a browser. Catalyst lets you do this
1462 using the C<scripts/myapp_test.pl> script. Just supply the URL you
1463 wish to display and it will run that request through the normal
1464 controller dispatch logic and use the appropriate view to render the
1465 output (obviously, complex pages may dump a lot of text to your
1466 terminal window). For example, if you type:
1468 $ script/myapp_test.pl "/books/list"
1470 You should get the same text as if you visited
1471 L<http://localhost:3000/books/list> with the normal development server
1472 and asked your browser to view the page source.
1475 =head1 OPTIONAL INFORMATION
1477 B<NOTE: The rest of this chapter of the tutorial is optional. You can
1478 skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
1482 =head2 Using 'RenderView' for the Default View
1484 Once your controller logic has processed the request from a user, it
1485 forwards processing to your view in order to generate the appropriate
1486 response output. Catalyst uses
1487 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1488 default to automatically perform this operation. If you look in
1489 C<lib/MyApp/Controller/Root.pm>, you should see the empty
1490 definition for the C<sub end> method:
1492 sub end : ActionClass('RenderView') {}
1494 The following bullet points provide a quick overview of the
1495 C<RenderView> process:
1501 C<Root.pm> is designed to hold application-wide logic.
1505 At the end of a given user request, Catalyst will call the most specific
1506 C<end> method that's appropriate. For example, if the controller for a
1507 request has an C<end> method defined, it will be called. However, if
1508 the controller does not define a controller-specific C<end> method, the
1509 "global" C<end> method in C<Root.pm> will be called.
1513 Because the definition includes an C<ActionClass> attribute, the
1514 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1515 will be executed B<after> any code inside the definition of C<sub end>
1516 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1517 for more information on C<ActionClass>.
1521 Because C<sub end> is empty, this effectively just runs the default
1522 logic in C<RenderView>. However, you can easily extend the
1523 C<RenderView> logic by adding your own code inside the empty method body
1524 (C<{}>) created by the Catalyst Helpers when we first ran the
1525 C<catalyst.pl> to initialize our application. See
1526 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1527 detailed information on how to extend C<RenderView> in C<sub end>.
1532 =head2 RenderView's "dump_info" Feature
1534 One of the nice features of C<RenderView> is that it automatically
1535 allows you to add C<dump_info=1> to the end of any URL for your
1536 application and it will force the display of the "exception dump"
1537 screen to the client browser. You can try this out by pointing
1538 your browser to this URL:
1540 http://localhost:3000/books/list?dump_info=1
1542 You should get a page with the following message at the top:
1544 Caught exception in MyApp::Controller::Root->end "Forced debug -
1545 Scrubbed output at /usr/share/perl5/Catalyst/Action/RenderView.pm line 46."
1547 Along with a summary of your application's state at the end of the
1548 processing for that request. The "Stash" section should show a
1549 summarized version of the DBIC book model objects. If desired, you
1550 can adjust the summarization logic (called "scrubbing" logic) -- see
1551 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for
1554 Note that you shouldn't need to worry about "normal clients" using
1555 this technique to "reverse engineer" your application -- C<RenderView>
1556 only supports the C<dump_info=1> feature when your application is
1557 running in C<-Debug> mode (something you won't do once you have your
1558 application deployed in production).
1561 =head2 Using The Default Template Name
1563 By default, C<Catalyst::View::TT> will look for a template that uses the
1564 same name as your controller action, allowing you to save the step of
1565 manually specifying the template name in each action. For example, this
1566 would allow us to remove the
1567 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1568 C<list> action in the Books controller. Open
1569 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1570 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1575 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1580 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1581 # 'Context' that's used to 'glue together' the various components
1582 # that make up the application
1583 my ($self, $c) = @_;
1585 # Retrieve all of the book records as book model objects and store in the
1586 # stash where they can be accessed by the TT template
1587 $c->stash(books => [$c->model('DB::Book')->all]);
1589 # Set the TT template to use. You will almost always want to do this
1590 # in your action methods (actions methods respond to user input in
1591 # your controllers).
1592 #$c->stash(template => 'books/list.tt2');
1596 You should now be able to access the L<http://localhost:3000/books/list>
1599 B<NOTE:> Please note that if you use the default template technique,
1600 you will B<not> be able to use either the C<$c-E<gt>forward> or
1601 the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1602 Chapter 9 of the Tutorial).
1604 B<IMPORTANT:> Make sure that you do NOT skip the following section
1605 before continuing to the next chapter 4 Basic CRUD.
1608 =head2 Return To A Manually Specified Template
1610 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1611 later in the tutorial, you should remove the comment from the
1612 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1614 $c->stash(template => 'books/list.tt2');
1616 Then delete the C<TEMPLATE_EXTENSION> line in
1617 C<lib/MyApp/View/HTML.pm>.
1619 Check the L<http://localhost:3000/books/list> URL in your browser.
1620 It should look the same manner as with earlier sections.
1625 Kennedy Clark, C<hkclark@gmail.com>
1627 Please report any errors, issues or suggestions to the author. The
1628 most recent version of the Catalyst Tutorial can be found at
1629 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
1631 Copyright 2006-2010, Kennedy Clark, under the
1632 Creative Commons Attribution Share-Alike License Version 3.0
1633 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).