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 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>).
484 B<NOTE:> Since we've added a call to C<< MyApp->path_to() >> inside of
485 C<lib/MyApp/View/HTML.pm>, we need to update C<t/view_HTML.t> to include
486 C<MyApp> or the test will fail. Edit C<t/view_HTML.t> and add the C<use>
487 statement after the others, so this:
491 BEGIN { use_ok 'MyApp::View::HTML' }
498 BEGIN { use_ok 'MyApp::View::HTML' }
500 =head2 Create a TT Template Page
502 First create a directory for book-related TT templates:
504 $ mkdir -p root/src/books
506 Then create C<root/src/books/list.tt2> in your editor and enter:
508 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
509 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
510 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
511 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
513 [% # Provide a title -%]
514 [% META title = 'Book List' -%]
517 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
518 [% # Display each book in a table row %]
519 [% FOREACH book IN books -%]
521 <td>[% book.title %]</td>
522 <td>[% book.rating %]</td>
528 As indicated by the inline comments above, the C<META title> line uses
529 TT's META feature to provide a title to the "wrapper" that we will
530 create later. Meanwhile, the C<FOREACH> loop iterates through each
531 C<book> model object and prints the C<title> and C<rating> fields.
533 The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
534 supports a wide variety of directives for "calling" other files,
535 looping, conditional logic, etc. In general, TT simplifies the usual
536 range of Perl operators down to the single dot (".") operator. This
537 applies to operations as diverse as method calls, hash lookups, and list
539 L<http://search.cpan.org/perldoc?Template::Manual::Variables> for
540 details and examples). In addition to the usual L<Template> module Pod
541 documentation, you can access the TT manual at
542 L<http://search.cpan.org/perldoc?Template::Manual>.
544 B<TIP:> While you can build all sorts of complex logic into your TT
545 templates, you should in general keep the "code" part of your
546 templates as simple as possible. If you need more complex logic,
547 create helper methods in your model that abstract out a set of code
548 into a single call from your TT template. (Note that the same is true
549 of your controller logic as well -- complex sections of code in your
550 controllers should often be pulled out and placed into your model
551 objects.) In Chapter 4 of the tutorial we will explore some extremely
552 helpful and powerful features of L<DBIx::Class> that allow you to pull
553 code out of your views and controllers and place it where it
554 rightfully belongs in a model class.
557 =head2 Test Run The Application
559 To test your work so far, first start the development server:
561 $ script/myapp_server.pl -r
563 Then point your browser to L<http://localhost:3000> and you should
564 still get the Catalyst welcome page. Next, change the URL in your
565 browser to L<http://localhost:3000/books/list>. If you have
566 everything working so far, you should see a web page that displays
567 nothing other than our column headers for "Title", "Rating", and
568 "Author(s)" -- we will not see any books until we get the database and
571 If you run into problems getting your application to run correctly, it
572 might be helpful to refer to some of the debugging techniques covered in
573 the L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> chapter of the
577 =head1 CREATE A SQLITE DATABASE
579 In this step, we make a text file with the required SQL commands to
580 create a database table and load some sample data. We will use
581 SQLite (L<http://www.sqlite.org>), a popular database that is
582 lightweight and easy to use. Be sure to get at least version 3. Open
583 C<myapp01.sql> in your editor and enter:
586 -- Create a very simple database to hold book and author information
588 PRAGMA foreign_keys = ON;
590 id INTEGER PRIMARY KEY,
594 -- 'book_author' is a many-to-many join table between books & authors
595 CREATE TABLE book_author (
596 book_id INTEGER REFERENCES book(id) ON DELETE CASCADE ON UPDATE CASCADE,
597 author_id INTEGER REFERENCES author(id) ON DELETE CASCADE ON UPDATE CASCADE,
598 PRIMARY KEY (book_id, author_id)
600 CREATE TABLE author (
601 id INTEGER PRIMARY KEY,
606 --- Load some sample data
608 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
609 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
610 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
611 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
612 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
613 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
614 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
615 INSERT INTO author VALUES (3, 'Christian', 'Degu');
616 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
617 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
618 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
619 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
620 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
621 INSERT INTO book_author VALUES (1, 1);
622 INSERT INTO book_author VALUES (1, 2);
623 INSERT INTO book_author VALUES (1, 3);
624 INSERT INTO book_author VALUES (2, 4);
625 INSERT INTO book_author VALUES (3, 5);
626 INSERT INTO book_author VALUES (4, 6);
627 INSERT INTO book_author VALUES (4, 7);
628 INSERT INTO book_author VALUES (5, 8);
630 Then use the following command to build a C<myapp.db> SQLite database:
632 $ sqlite3 myapp.db < myapp01.sql
634 If you need to create the database more than once, you probably want to
635 issue the C<rm myapp.db> command to delete the database before you use
636 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
638 Once the C<myapp.db> database file has been created and initialized, you
639 can use the SQLite command line environment to do a quick dump of the
643 SQLite version 3.6.22
644 Enter ".help" for instructions
645 Enter SQL statements terminated with a ";"
646 sqlite> select * from book;
647 1|CCSP SNRS Exam Certification Guide|5
648 2|TCP/IP Illustrated, Volume 1|5
649 3|Internetworking with TCP/IP Vol.1|4
651 5|Designing with Web Standards|5
657 $ sqlite3 myapp.db "select * from book"
658 1|CCSP SNRS Exam Certification Guide|5
659 2|TCP/IP Illustrated, Volume 1|5
660 3|Internetworking with TCP/IP Vol.1|4
662 5|Designing with Web Standards|5
664 As with most other SQL tools, if you are using the full "interactive"
665 environment you need to terminate your SQL commands with a ";" (it's not
666 required if you do a single SQL statement on the command line). Use
667 ".q" to exit from SQLite from the SQLite interactive mode and return to
668 your OS command prompt.
670 Please note that here we have chosen to use 'singular' table names. This is
671 because the default inflection code for older versions of
672 L<DBIx::Class::Schema::Loader> does NOT handle plurals. There has been much
673 philosophical discussion on whether table names should be plural or singular.
674 There is no one correct answer, as long as one makes a choice and remains
675 consistent with it. If you prefer plural table names (e.g. you think that they
676 are easier to read) then see the documentation in
677 L<DBIx::Class::Schema::Loader::Base/naming> (version 0.05 or greater).
679 For using other databases, such as PostgreSQL or MySQL, see
680 L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices>.
683 =head1 DATABASE ACCESS WITH DBIx::Class
685 Catalyst can be used with virtually any form of datastore available
686 via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
687 can be used to access databases through the traditional Perl L<DBI>
688 interface or you can use a model to access files of any type on the
689 filesystem. However, most Catalyst applications use some form of
690 object-relational mapping (ORM) technology to create objects
691 associated with tables in a relational database. Matt Trout's
692 L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
693 as the Perl-based ORM technology of choice. Most new Catalyst
694 applications rely on DBIx::Class, as will this tutorial.
696 Although DBIx::Class has included support for a C<create=dynamic> mode
697 to automatically read the database structure every time the
698 application starts, its use is no longer recommended. While it can
699 make for "flashy" demos, the use of the C<create=static> mode we use
700 below can be implemented just as quickly and provides many advantages
701 (such as the ability to add your own methods to the overall DBIC
702 framework, a technique that we see in Chapter 4).
705 =head2 Make Sure You Have a Recent Version of the DBIx::Class Model
707 First, let's be sure we have a recent version of the DBIC helper,
708 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, so
709 that we can take advantage of some recent enhancements in how
710 foreign keys are handled with SQLite. To check your version,
713 $ perl -MCatalyst::Model::DBIC::Schema -e \
714 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
717 Please note the '\' above. Depending on your environment, you might
718 be able to cut and paste the text as shown or need to remove the '\'
719 character to that the command is all on a single line.
721 If you are following along in Debian 5, you should have version 0.40 or
722 higher (shown above as "0.4" with the tailing zero removed). If you have
723 less than v0.39, you will need to run this command to install it
726 $ sudo cpan Catalyst::Model::DBIC::Schema
728 And re-run the version print command to verify that you are now at
731 In addition, since we are using SQLite's foreign key support here,
732 please be sure that you use version C<1.27> of L<DBD::SQLite> or later:
734 $ perl -MDBD::SQLite -e 'print "$DBD::SQLite::VERSION\n"'
737 Upgrade if you are not at version C<1.27> or higher.
740 =head2 Create Static DBIx::Class Schema Files
742 Before you continue, make sure your C<myapp.db> database file is in
743 the application's topmost directory. Now use the model helper with
744 the C<create=static> option to read the database with
745 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
746 automatically build the required files for us:
748 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
749 create=static dbi:SQLite:myapp.db \
750 on_connect_do="PRAGMA foreign_keys = ON"
751 exists "/home/me/MyApp/script/../lib/MyApp/Model"
752 exists "/home/me/MyApp/script/../t"
753 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
754 Schema dump completed.
755 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
756 created "/home/me/MyApp/script/../t/model_DB.t"
758 Please note the '\' above. Depending on your environment, you might
759 be able to cut and paste the text as shown or need to remove the '\'
760 character to that the command is all on a single line.
762 The C<script/myapp_create.pl> command breaks down like this:
768 C<DB> is the name of the model class to be created by the helper in
773 C<DBIC::Schema> is the type of the model to create.
777 C<MyApp::Schema> is the name of the DBIC schema file written to
778 C<lib/MyApp/Schema.pm>.
782 C<create=static> causes
783 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
784 load the schema as it runs and then write that information out
789 C<dbi:SQLite:myapp.db> is the standard DBI connect string
794 And finally, the C<on_connect_do> string requests that
795 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> create
796 foreign key relationships for us (this is not needed for databases such
797 as PostgreSQL and MySQL, but is required for SQLite). If you take a look
798 at C<lib/MyApp/Model/DB.pm>, you will see that the SQLite pragma is
799 propogated to the Model, so that SQLite's recent (and optional) foreign
800 key enforcement is enabled at the start of every database connection.
806 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
807 only contains a call to the C<load_namespaces> method. You will also
808 find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
809 has a subdirectory called "Result". This "Result" subdirectory then
810 has files named according to each of the tables in our simple database
811 (C<Author.pm>, C<BookAuthor.pm>, and C<Book.pm>). These three
812 files are called "Result Classes" in DBIx::Class nomenclature. Although the
813 Result Class files are named after tables in our database, the classes
814 correspond to the I<row-level data> that is returned by DBIC (more on
815 this later, especially in
816 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
818 The idea with the Result Source files created under
819 C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
820 edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
821 warning. If you place all of your changes below that point in the
822 file, you can regenerate the automatically created information at the
823 top of each file should your database structure get updated.
825 Also note the "flow" of the model information across the various files
826 and directories. Catalyst will initially load the model from
827 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
828 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the
829 call to C<load_namespaces> in C<Schema.pm> will load each of the
830 "Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
831 The final outcome is that Catalyst will dynamically create three
832 table-specific Catalyst models every time the application starts (you
833 can see these three model files listed in the debug output generated
834 when you launch the application).
836 B<NOTE:> Older versions of
837 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
838 deprecated DBIx::Class C<load_classes> technique instead of the newer
839 C<load_namespaces>. For new applications, please try to use
840 C<load_namespaces> since it more easily supports a very useful DBIC
841 technique called "ResultSet Classes." If you need to convert an
842 existing application from "load_classes" to "load_namespaces," you can
843 use this process to automate the migration, but first make sure you have
844 version C<0.39> of L<Catalyst::Model::DBIC::Schema> and
845 L<DBIx::Class::Schema::Loader> version C<0.05000> or later.
847 $ # Re-run the helper to upgrade for you
848 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
849 create=static naming=current use_namespaces=1 \
850 dbi:SQLite:myapp.db \
851 on_connect_do="PRAGMA foreign_keys = ON"
854 =head1 ENABLE THE MODEL IN THE CONTROLLER
856 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
857 left disabled earlier so that your version matches the following (un-
858 comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
859 and delete the next 2 lines):
863 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
868 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
869 # 'Context' that's used to 'glue together' the various components
870 # that make up the application
873 # Retrieve all of the book records as book model objects and store
874 # in the stash where they can be accessed by the TT template
875 $c->stash(books => [$c->model('DB::Book')->all]);
877 # Set the TT template to use. You will almost always want to do this
878 # in your action methods (action methods respond to user input in
880 $c->stash(template => 'books/list.tt2');
883 B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
884 above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
885 two are equivalent. Either way, C<$c-E<gt>model> returns a
886 L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
887 against the database and iterating over the set of results that is
890 We are using the C<-E<gt>all> to fetch all of the books. DBIC
891 supports a wide variety of more advanced operations to easily do
892 things like filtering and sorting the results. For example, the
893 following could be used to sort the results by descending title:
895 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
897 Some other examples are provided in
898 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
899 additional information found at L<DBIx::Class::ResultSet/search>,
900 L<DBIx::Class::Manual::FAQ/Searching>,
901 L<DBIx::Class::Manual::Intro|DBIx::Class::Manual::Intro>
902 and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
905 =head2 Test Run The Application
907 First, let's enable an environment variable that causes DBIx::Class to
908 dump the SQL statements used to access the database. This is a
909 helpful trick when you are trying to debug your database-oriented
910 code. Press C<Ctrl-C> to break out of the development server and
913 $ export DBIC_TRACE=1
914 $ script/myapp_server.pl -r
916 This assumes you are using bash as your shell -- adjust accordingly if
917 you are using a different shell (for example, under tcsh, use
918 C<setenv DBIC_TRACE 1>).
920 B<NOTE:> You can also set this in your code using
921 C<$class-E<gt>storage-E<gt>debug(1);>. See
922 L<DBIx::Class::Manual::Troubleshooting> for details (including options
923 to log to a file instead of displaying to the Catalyst development server
926 Then launch the Catalyst development server. The log output should
927 display something like:
929 $ script/myapp_server.pl -r
930 [debug] Debug messages enabled
931 [debug] Statistics enabled
932 [debug] Loaded plugins:
933 .----------------------------------------------------------------------------.
934 | Catalyst::Plugin::ConfigLoader 0.27 |
935 | Catalyst::Plugin::StackTrace 0.11 |
936 '----------------------------------------------------------------------------'
938 [debug] Loaded dispatcher "Catalyst::Dispatcher"
939 [debug] Loaded engine "Catalyst::Engine::HTTP"
940 [debug] Found home "/home/me/MyApp"
941 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
942 [debug] Loaded components:
943 .-----------------------------------------------------------------+----------.
945 +-----------------------------------------------------------------+----------+
946 | MyApp::Controller::Books | instance |
947 | MyApp::Controller::Root | instance |
948 | MyApp::Model::DB | instance |
949 | MyApp::Model::DB::Author | class |
950 | MyApp::Model::DB::Book | class |
951 | MyApp::Model::DB::BookAuthor | class |
952 | MyApp::View::HTML | instance |
953 '-----------------------------------------------------------------+----------'
955 [debug] Loaded Private actions:
956 .----------------------+--------------------------------------+--------------.
957 | Private | Class | Method |
958 +----------------------+--------------------------------------+--------------+
959 | /default | MyApp::Controller::Root | default |
960 | /end | MyApp::Controller::Root | end |
961 | /index | MyApp::Controller::Root | index |
962 | /books/index | MyApp::Controller::Books | index |
963 | /books/list | MyApp::Controller::Books | list |
964 '----------------------+--------------------------------------+--------------'
966 [debug] Loaded Path actions:
967 .-------------------------------------+--------------------------------------.
969 +-------------------------------------+--------------------------------------+
972 | /books | /books/index |
973 | /books/list | /books/list |
974 '-------------------------------------+--------------------------------------'
976 [info] MyApp powered by Catalyst 5.80020
977 You can connect to your server at http://debian:3000
979 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
980 the 'base' directory of your application, not inside the C<script>
981 directory itself or it will not be able to locate the C<myapp.db>
982 database file. You can use a fully qualified or a relative path to
983 locate the database file, but we did not specify that when we ran the
984 model helper earlier.
986 Some things you should note in the output above:
992 Catalyst::Model::DBIC::Schema dynamically created three model classes,
993 one to represent each of the three tables in our database
994 (C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
995 and C<MyApp::Model::DB::Book>).
999 The "list" action in our Books controller showed up with a path of
1004 Point your browser to L<http://localhost:3000> and you should still get
1005 the Catalyst welcome page.
1007 Next, to view the book list, change the URL in your browser to
1008 L<http://localhost:3000/books/list>. You should get a list of the five
1009 books loaded by the C<myapp01.sql> script above without any formatting.
1010 The rating for each book should appear on each row, but the "Author(s)"
1011 column will still be blank (we will fill that in later).
1013 Also notice in the output of the C<script/myapp_server.pl> that
1014 DBIx::Class used the following SQL to retrieve the data:
1016 SELECT me.id, me.title, me.rating FROM book me
1018 because we enabled DBIC_TRACE.
1020 You now have the beginnings of a simple but workable web application.
1021 Continue on to future sections and we will develop the application
1025 =head1 CREATE A WRAPPER FOR THE VIEW
1027 When using TT, you can (and should) create a wrapper that will
1028 literally wrap content around each of your templates. This is
1029 certainly useful as you have one main source for changing things that
1030 will appear across your entire site/application instead of having to
1031 edit many individual files.
1034 =head2 Configure HTML.pm For The Wrapper
1036 In order to create a wrapper, you must first edit your TT view and
1037 tell it where to find your wrapper file.
1039 Edit your TT view in C<lib/MyApp/View/HTML.pm> and change it to match the
1042 __PACKAGE__->config(
1043 # Change default TT extension
1044 TEMPLATE_EXTENSION => '.tt2',
1045 # Set the location for TT files
1047 MyApp->path_to( 'root', 'src' ),
1049 # Set to 1 for detailed timer stats in your HTML as comments
1051 # This is your wrapper template located in the 'root/src'
1052 WRAPPER => 'wrapper.tt2',
1056 =head2 Create the Wrapper Template File and Stylesheet
1058 Next you need to set up your wrapper template. Basically, you'll want
1059 to take the overall layout of your site and put it into this file.
1060 For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1062 <?xml version="1.0" encoding="UTF-8"?>
1063 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1064 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
1066 <title>[% template.title or "My Catalyst App!" %]</title>
1067 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1073 [%# Your logo could go here -%]
1074 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1075 [%# Insert the page title -%]
1076 <h1>[% template.title or site.title %]</h1>
1079 <div id="bodyblock">
1083 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1084 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1086 </div><!-- end menu -->
1089 [%# Status and error messages %]
1090 <span class="message">[% status_msg %]</span>
1091 <span class="error">[% error_msg %]</span>
1092 [%# This is where TT will stick all of your template's contents. -%]
1094 </div><!-- end content -->
1095 </div><!-- end bodyblock -->
1097 <div id="footer">Copyright (c) your name goes here</div>
1098 </div><!-- end outer -->
1103 Notice the status and error message sections in the code above:
1105 <span class="status">[% status_msg %]</span>
1106 <span class="error">[% error_msg %]</span>
1108 If we set either message in the Catalyst stash (e.g.,
1109 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1110 will be displayed whenever any view used by that request is rendered.
1111 The C<message> and C<error> CSS styles can be customized to suit your
1112 needs in the C<root/static/css/main.css> file we create below.
1120 The Catalyst stash only lasts for a single HTTP request. If
1121 you need to retain information across requests you can use
1122 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
1123 Catalyst sessions in the Authentication chapter of the tutorial).
1127 Although it is beyond the scope of this tutorial, you may wish to use
1128 a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
1129 Dojo (L<http://www.dojotoolkit.org>).
1134 =head3 Create A Basic Stylesheet
1136 First create a central location for stylesheets under the static
1139 $ mkdir root/static/css
1141 Then open the file C<root/static/css/main.css> (the file referenced in
1142 the stylesheet href link of our wrapper above) and add the following
1161 background-color: #ddd;
1167 padding: 0 0 50% 5px;
1168 font-weight: normal;
1169 background-color: #ddd;
1182 You may wish to check out a "CSS Framework" like Emastic
1183 (L<http://code.google.com/p/emastic/>) as a way to quickly
1184 provide lots of high-quality CSS functionality.
1187 =head2 Test Run The Application
1189 Hit "Reload" in your web browser and you should now see a formatted
1190 version of our basic book list. (Again, the development server should
1191 have automatically restarted when you made changes to
1192 C<lib/MyApp/View/HTML.pm>. If you are not using the "-r" option, you will
1193 need to hit C<Ctrl-C> and manually restart it. Also note that the
1194 development server does I<NOT> need to restart for changes to the TT and
1195 static files we created and edited in the C<root> directory -- those
1196 updates are handled on a per-request basis.)
1198 Although our wrapper and stylesheet are obviously very simple, you
1199 should see how it allows us to control the overall look of an entire
1200 website from two central files. To add new pages to the site, just
1201 provide a template that fills in the C<content> section of our wrapper
1202 template -- the wrapper will provide the overall feel of the page.
1205 =head2 Updating the Generated DBIx::Class Result Class Files
1207 If you take a look at the Schema files automatically generated by
1208 L<DBIx::Class::Schema::Loader>, you will see that it has already defined
1209 C<has_many> and C<belongs_to> relationships on each side of our foreign
1210 keys. For example, take a look at C<lib/MyApp/Schema/Result/Book.pm> and
1211 notice the following code:
1219 Related object: L<MyApp::Schema::Result::BookAuthor>
1223 __PACKAGE__->has_many(
1225 "MyApp::Schema::Result::BookAuthor",
1226 { "foreign.book_id" => "self.id" },
1229 Each C<Book> "has_many" C<book_authors>, where C<BookAuthor> is
1230 the many-to-many table that allows each Book to have multiple
1231 Authors, and each Author to have mulitple books. The arguments
1238 C<book_authors> - The name for this relationship. DBIC will create
1239 an accessor on the C<Books> DBIC Row object with this name.
1243 C<MyApp::Schema::Result::BookAuthor> - The name of the DBIC model
1244 class referenced by this C<has_many> relationship.
1248 C<foreign.book_id> - C<book_id> is the name of the foreign key
1249 column in the I<foreign> table that points back to this table.
1253 C<self.id> - C<id> is the name of the column in I<this> table
1254 that is referenced by the foreign key.
1258 See L<DBIx::Class::Relationship/has_many> for
1259 additional information. Note that you might see a "hand coded"
1260 version of the C<has_many> relationship above expressed as:
1262 __PACKAGE__->has_many(
1264 "MyApp::Schema::Result::BookAuthor",
1268 Where the third argument is simply the name of the column in
1269 the foreign table. However, the hashref syntax used by
1270 L<DBIx::Class::Schema::Loader> is more flexible (for example,
1271 it can handle "multi-column" foreign keys).
1273 B<Note:> If you are using older versions of SQLite and related DBIC
1274 tools, you will need to manually define your C<has_many> and
1275 C<belongs_to> relationships. We recommend upgrading to the versions
1276 specified above. :-)
1278 Have a look at C<lib/MyApp/Schema/Result/BookAuthor.pm> and notice
1279 that there is a C<belongs_to> relationship defined that acts as the
1280 "mirror image" to the C<has_many> relationship we just looked at
1289 Related object: L<MyApp::Schema::Result::Book>
1293 __PACKAGE__->belongs_to(
1295 "MyApp::Schema::Result::Book",
1296 { id => "book_id" },
1297 { join_type => "LEFT" },
1300 The arguments are similar, but see
1301 L<DBIx::Class::Relationship/belongs_to> for the details.
1303 Although recent versions of SQLite and L<DBIx::Class::Schema::Loader>
1304 automatically handle the C<has_many> and C<belongs_to> relationships,
1305 C<many_to_many> relationship bridges (not technically a relationship)
1306 currently need to be manually inserted.
1307 To add a C<many_to_many> relationship bridge, first edit
1308 C<lib/MyApp/Schema/Result/Book.pm> and add the following text below
1309 the C<# You can replace this text...> comment:
1313 # 1) Name of relationship bridge, DBIC will create accessor with this name
1314 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1315 # 3) Name of belongs_to() relationship in model class of has_many() above
1316 # You must already have the has_many() defined to use a many_to_many().
1317 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1319 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1320 file. As with any Perl package, we need to end the last line with
1321 a statement that evaluates to C<true>. This is customarily done with
1322 C<1;> on a line by itself.
1324 The C<many_to_many> relationship bridge is optional, but it makes it
1325 easier to map a book to its collection of authors. Without
1326 it, we would have to "walk" through the C<book_author> table as in
1327 C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
1328 will see examples on how to use DBIx::Class objects in your code soon,
1329 but note that because C<$book-E<gt>book_author> can return multiple
1330 authors, we have to use C<first> to display a single author).
1331 C<many_to_many> allows us to use the shorter
1332 C<$book-E<gt>author-E<gt>first-E<gt>last_name>. Note that you cannot
1333 define a C<many_to_many> relationship bridge without also having the
1334 C<has_many> relationship in place.
1336 Then edit C<lib/MyApp/Schema/Result/Author.pm> and add the reverse
1337 C<many_to_many> relationship bridge for C<Author> as follows (again, be careful
1338 to put in above the C<1;> but below the C<# DO NOT MODIFY THIS OR
1339 ANYTHING ABOVE!> comment):
1343 # 1) Name of relationship bridge, DBIC will create accessor with this name
1344 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1345 # 3) Name of belongs_to() relationship in model class of has_many() above
1346 # You must already have the has_many() defined to use a many_to_many().
1347 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
1350 =head2 Run The Application
1352 Run the Catalyst development server script with the C<DBIC_TRACE> option
1353 (it might still be enabled from earlier in the tutorial, but here is an
1354 alternate way to specify the trace option just in case):
1356 $ DBIC_TRACE=1 script/myapp_server.pl -r
1358 Make sure that the application loads correctly and that you see the
1359 three dynamically created model class (one for each of the
1360 Result Classes we created).
1362 Then hit the URL L<http://localhost:3000/books/list> with your browser
1363 and be sure that the book list still displays correctly.
1365 B<Note:> You will not see the authors yet because the view does not yet
1366 use the new relations. Read on to the next section where we update the
1367 template to do that.
1370 =head1 UPDATING THE VIEW
1372 Let's add a new column to our book list page that takes advantage of
1373 the relationship information we manually added to our schema files in
1374 the previous section. Edit C<root/src/books/list.tt2> and replace
1375 the "empty" table cell "<td></td>" with the following:
1379 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1380 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1381 [% # loop in 'side effect notation' to load just the last names of the -%]
1382 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
1383 [% # a value, so nothing will be printed here. But, if you have something -%]
1384 [% # in TT that does return a value and you don't want it printed, you -%]
1385 [% # 1) assign it to a bogus value, or -%]
1386 [% # 2) use the CALL keyword to call it and discard the return value. -%]
1387 [% tt_authors = [ ];
1388 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1389 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1390 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1391 ([% tt_authors.size | html %])
1392 [% # Use another TT vmethod to join & print the names & comma separators -%]
1393 [% tt_authors.join(', ') | html %]
1397 B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1398 possible out of your views. This kind of logic belongs in your model
1399 (the same goes for controllers -- keep them as "thin" as possible and
1400 push all of the "complicated code" out to your model objects). Avoid
1401 code like you see in the previous example -- we are only using it here
1402 to show some extra features in TT until we get to the more advanced
1403 model features we will see in Chapter 4 (see
1404 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1406 Then hit "Reload" in your browser (note that you don't need to reload
1407 the development server or use the C<-r> option when updating TT
1408 templates) and you should now see the number of authors each book has
1409 along with a comma-separated list of the authors' last names. (If you
1410 didn't leave the development server running from the previous step,
1411 you will obviously need to start it before you can refresh your
1414 If you are still running the development server with C<DBIC_TRACE>
1415 enabled, you should also now see five more C<SELECT> statements in the
1416 debug output (one for each book as the authors are being retrieved by
1419 SELECT me.id, me.title, me.rating FROM book me:
1420 SELECT author.id, author.first_name, author.last_name FROM book_author me
1421 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '1'
1422 SELECT author.id, author.first_name, author.last_name FROM book_author me
1423 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '2'
1424 SELECT author.id, author.first_name, author.last_name FROM book_author me
1425 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '3'
1426 SELECT author.id, author.first_name, author.last_name FROM book_author me
1427 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '4'
1428 SELECT author.id, author.first_name, author.last_name FROM book_author me
1429 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '5'
1431 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1432 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1433 and > and avoid various types of dangerous hacks against your
1434 application. In a real application, you would probably want to put
1435 "| html" at the end of every field where a user has control over the
1436 information that can appear in that field (and can therefore inject
1437 markup or code if you don't "neutralize" those fields). In addition to
1438 "| html", Template Toolkit has a variety of other useful filters that
1439 can found in the documentation for
1440 L<Template::Filters|Template::Filters>.
1443 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1445 In some situations, it can be useful to run your application and
1446 display a page without using a browser. Catalyst lets you do this
1447 using the C<scripts/myapp_test.pl> script. Just supply the URL you
1448 wish to display and it will run that request through the normal
1449 controller dispatch logic and use the appropriate view to render the
1450 output (obviously, complex pages may dump a lot of text to your
1451 terminal window). For example, if you type:
1453 $ script/myapp_test.pl "/books/list"
1455 You should get the same text as if you visited
1456 L<http://localhost:3000/books/list> with the normal development server
1457 and asked your browser to view the page source.
1460 =head1 OPTIONAL INFORMATION
1462 B<NOTE: The rest of this chapter of the tutorial is optional. You can
1463 skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
1467 =head2 Using 'RenderView' for the Default View
1469 Once your controller logic has processed the request from a user, it
1470 forwards processing to your view in order to generate the appropriate
1471 response output. Catalyst uses
1472 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1473 default to automatically perform this operation. If you look in
1474 C<lib/MyApp/Controller/Root.pm>, you should see the empty
1475 definition for the C<sub end> method:
1477 sub end : ActionClass('RenderView') {}
1479 The following bullet points provide a quick overview of the
1480 C<RenderView> process:
1486 C<Root.pm> is designed to hold application-wide logic.
1490 At the end of a given user request, Catalyst will call the most specific
1491 C<end> method that's appropriate. For example, if the controller for a
1492 request has an C<end> method defined, it will be called. However, if
1493 the controller does not define a controller-specific C<end> method, the
1494 "global" C<end> method in C<Root.pm> will be called.
1498 Because the definition includes an C<ActionClass> attribute, the
1499 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1500 will be executed B<after> any code inside the definition of C<sub end>
1501 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1502 for more information on C<ActionClass>.
1506 Because C<sub end> is empty, this effectively just runs the default
1507 logic in C<RenderView>. However, you can easily extend the
1508 C<RenderView> logic by adding your own code inside the empty method body
1509 (C<{}>) created by the Catalyst Helpers when we first ran the
1510 C<catalyst.pl> to initialize our application. See
1511 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1512 detailed information on how to extend C<RenderView> in C<sub end>.
1517 =head2 RenderView's "dump_info" Feature
1519 One of the nice features of C<RenderView> is that it automatically
1520 allows you to add C<dump_info=1> to the end of any URL for your
1521 application and it will force the display of the "exception dump"
1522 screen to the client browser. You can try this out by pointing
1523 your browser to this URL:
1525 http://localhost:3000/books/list?dump_info=1
1527 You should get a page with the following message at the top:
1529 Caught exception in MyApp::Controller::Root->end "Forced debug -
1530 Scrubbed output at /usr/share/perl5/Catalyst/Action/RenderView.pm line 46."
1532 Along with a summary of your application's state at the end of the
1533 processing for that request. The "Stash" section should show a
1534 summarized version of the DBIC book model objects. If desired, you
1535 can adjust the summarization logic (called "scrubbing" logic) -- see
1536 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for
1539 Note that you shouldn't need to worry about "normal clients" using
1540 this technique to "reverse engineer" your application -- C<RenderView>
1541 only supports the C<dump_info=1> feature when your application is
1542 running in C<-Debug> mode (something you won't do once you have your
1543 application deployed in production).
1546 =head2 Using The Default Template Name
1548 By default, C<Catalyst::View::TT> will look for a template that uses the
1549 same name as your controller action, allowing you to save the step of
1550 manually specifying the template name in each action. For example, this
1551 would allow us to remove the
1552 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1553 C<list> action in the Books controller. Open
1554 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1555 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1560 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1565 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1566 # 'Context' that's used to 'glue together' the various components
1567 # that make up the application
1568 my ($self, $c) = @_;
1570 # Retrieve all of the book records as book model objects and store in the
1571 # stash where they can be accessed by the TT template
1572 $c->stash(books => [$c->model('DB::Book')->all]);
1574 # Set the TT template to use. You will almost always want to do this
1575 # in your action methods (actions methods respond to user input in
1576 # your controllers).
1577 #$c->stash(template => 'books/list.tt2');
1581 You should now be able to access the L<http://localhost:3000/books/list>
1584 B<NOTE:> Please note that if you use the default template technique,
1585 you will B<not> be able to use either the C<$c-E<gt>forward> or
1586 the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1587 Chapter 9 of the Tutorial).
1589 B<IMPORTANT:> Make sure that you do NOT skip the following section
1590 before continuing to the next chapter 4 Basic CRUD.
1593 =head2 Return To A Manually Specified Template
1595 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1596 later in the tutorial, you should remove the comment from the
1597 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1599 $c->stash(template => 'books/list.tt2');
1601 Then delete the C<TEMPLATE_EXTENSION> line in
1602 C<lib/MyApp/View/HTML.pm>.
1604 Check the L<http://localhost:3000/books/list> URL in your browser.
1605 It should look the same manner as with earlier sections.
1610 Kennedy Clark, C<hkclark@gmail.com>
1612 Please report any errors, issues or suggestions to the author. The
1613 most recent version of the Catalyst Tutorial can be found at
1614 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
1616 Copyright 2006-2010, Kennedy Clark, under the
1617 Creative Commons Attribution Share-Alike License Version 3.0
1618 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).