3 Catalyst::Manual::Tutorial::MoreCatalystBasics - Catalyst Tutorial - Part 3: More Catalyst Application Development Basics
8 This is B<Part 3 of 10> for the Catalyst tutorial.
10 L<Tutorial Overview|Catalyst::Manual::Tutorial>
16 L<Introduction|Catalyst::Manual::Tutorial::Intro>
20 L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics>
24 B<More Catalyst Basics>
28 L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>
32 L<Authentication|Catalyst::Manual::Tutorial::Authentication>
36 L<Authorization|Catalyst::Manual::Tutorial::Authorization>
40 L<Debugging|Catalyst::Manual::Tutorial::Debugging>
44 L<Testing|Catalyst::Manual::Tutorial::Testing>
48 L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
52 L<Appendices|Catalyst::Manual::Tutorial::Appendices>
59 This part of the tutorial builds on the work done in Part 2 to explore
60 some features that are more typical of "real world" web applications.
61 From this part of the tutorial onward, we will be building a simple
62 book database application. Although the application will be too
63 limited to be of use to anyone, it should provide a basic environment
64 where we can explore a variety of features used in virtually all web
67 You can checkout the source code for this example from the catalyst
68 subversion repository as per the instructions in
69 L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>.
72 =head1 CREATE A NEW APPLICATION
74 The remainder of the tutorial will build an application called C<MyApp>.
75 First use the Catalyst C<catalyst.pl> script to initialize the framework
76 for the C<MyApp> application (make sure you aren't still inside the
77 directory of the C<Hello> application from the previous part of the
82 created "MyApp/script"
86 created "MyApp/script/myapp_create.pl"
89 This creates a similar skeletal structure to what we saw in Part 2 of
90 the tutorial, except with C<MyApp> and C<myapp> substituted for
91 C<Hello> and C<hello>.
94 =head1 EDIT THE LIST OF CATALYST PLUGINS
96 One of the greatest benefits of Catalyst is that it has such a large
97 library of plugins and base classes available. Plugins are used to
98 seamlessly integrate existing Perl modules into the overall Catalyst
99 framework. In general, they do this by adding additional methods to the
100 C<context> object (generally written as C<$c>) that Catalyst passes to
101 every component throughout the framework.
103 By default, Catalyst enables three plugins/flags:
111 Enables the Catalyst debug output you saw when we started the
112 C<script/myapp_server.pl> development server earlier. You can remove
113 this item when you place your application into production.
115 As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
116 Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
117 line of your application class will be plugins, Catalyst supports a
118 limited number of flag options (of these, C<-Debug> is the most
119 common). See the documentation for C<Catalyst.pm> to get details on
120 other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
122 If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
125 B<TIP>: Depending on your needs, it can be helpful to permanently
126 remove C<-Debug> from C<lib/MyApp.pm> and then use the C<-d> option
127 to C<script/myapp_server.pl> to re-enable it just for the development
128 server. We will not be using that approach in the tutorial, but feel
129 free to make use of it in your own projects.
133 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
135 C<ConfigLoader> provides an automatic way to load configurable
136 parameters for your application from a central
137 L<Config::General|Config::General> file (versus having the values
138 hard-coded inside your Perl modules). Config::General uses syntax
139 very similar to Apache configuration files. We will see how to use
140 this feature of Catalyst during the authentication and authorization
141 sections (Part 5 and Part 6).
143 B<IMPORTANT NOTE:> If you are using a version of
144 L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, you need to
145 be aware that Catalyst changed from a default format of YAML to the
146 more straightforward C<Config::General> format. This tutorial use the
147 newer C<myapp.conf> configuration file for C<Config::General> instead
148 of C<myapp.yml> for YAML. However, Catalyst has long supported both
149 formats and Catalyst will automatically use either C<myapp.conf> or
150 C<myapp.yml> (or any other format supported by
151 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
152 L<Config::Any|Config::Any>). If you are using a versions of
153 Catalyst::Devel prior to 1.06, you can convert to the newer format by
154 simply creating the C<myapp.yml> file manually and deleting
155 C<myapp.yml>. The default contents of C<myapp.conf> should only
156 consist of one line: C<name MyApp>.
158 B<TIP>: This script can be useful for converting between configuration
161 perl -Ilib -e 'use MyApp; use Config::General;
162 Config::General->new->save_file("myapp.conf", MyApp->config);'
164 B<NOTE:> The default C<myapp.conf> should look like:
170 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
172 C<Static::Simple> provides an easy method of serving static content such
173 as images and CSS files under the development server.
177 For our application, we want to add one new plugin into the mix. To
178 do this, edit C<lib/MyApp.pm> (this file is generally referred to as
179 your I<application class>) and delete the line with:
181 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
183 Then replace it with:
185 __PACKAGE__->setup(qw/
193 B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
194 techniques to load these plugins/flags. If you are following along in
195 Ubuntu 8.10, you should have C<Catalyst::Devel> v1.07 and see the
196 default code shown above. If you are using v1.08, you should see the
197 following by default:
199 use Catalyst qw/-Debug
203 __PACKAGE__->setup();
205 Don't let these variations confuse you -- they all accomplish the same
208 This tells Catalyst to start using one new plugin,
209 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
210 stack trace to the standard Catalyst "debug screen" (the screen
211 Catalyst sends to your browser when an error occurs). Be aware that
212 L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
213 browser, not in the console window from which you're running your
214 application, which is where logging output usually goes.
222 C<__PACKAGE__> is just a shorthand way of referencing the name of the
223 package where it is used. Therefore, in C<MyApp.pm>, C<__PACKAGE__>
224 is equivalent to C<MyApp>.
228 You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
229 before you put your application into production, but it can be helpful
234 When specifying plugins on the C<__PACKAGE__-E<gt>setup> line, you can
235 omit C<Catalyst::Plugin::> from the name. Additionally, you can
236 spread the plugin names across multiple lines as shown here, or place
237 them all on one (or more) lines as with the default configuration.
242 =head1 CREATE A CATALYST CONTROLLER
244 As discussed earlier, controllers are where you write methods that
245 interact with user input. Typically, controller methods respond to
246 C<GET> and C<POST> messages from the user's web browser.
248 Use the Catalyst C<create> script to add a controller for book-related
251 $ script/myapp_create.pl controller Books
252 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
253 exists "/home/me/MyApp/script/../t"
254 created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm"
255 created "/home/me/MyApp/script/../t/controller_Books.t"
257 Then edit C<lib/MyApp/Controller/Books.pm> (as discussed in Part 2 of
258 the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
259 each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
260 and add the following method to the controller:
264 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
269 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
270 # 'Context' that's used to 'glue together' the various components
271 # that make up the application
274 # Retrieve all of the book records as book model objects and store in the
275 # stash where they can be accessed by the TT template
276 # $c->stash->{books} = [$c->model('DB::Books')->all];
277 # But, for now, use this code until we create the model later
278 $c->stash->{books} = '';
280 # Set the TT template to use. You will almost always want to do this
281 # in your action methods (action methods respond to user input in
283 $c->stash->{template} = 'books/list.tt2';
286 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
287 cutting and pasting example code from POD-based documents.
289 Programmers experienced with object-oriented Perl should recognize
290 C<$self> as a reference to the object where this method was called.
291 On the other hand, C<$c> will be new to many Perl programmers who have
292 not used Catalyst before (it's sometimes written as C<$context>). The
293 Context object is automatically passed to all Catalyst components. It
294 is used to pass information between components and provide access to
295 Catalyst and plugin functionality.
297 B<Note:> Catalyst actions are regular Perl methods, but they make use
298 of Nicholas Clark's C<attributes> module (that's the "C<: Local>" next
299 to the C<sub list> in the code above) to provide additional
300 information to the Catalyst dispatcher logic. Many newer Catalyst
301 applications are switching to the use of "Literal" C<:Path> actions
302 and C<Args> attribute in lieu of C<: Local> and C<: Private>. For
303 example, C<sub any_method :Path :Args(0)> can be used instead of C<sub
304 index :Private> (because no path was supplied to C<Path> it matches
305 the "empty" URL in the namespace of that module... the same thing
306 C<sub index> would do) or C<sub list :Path('list') :Args(0)> could be
307 used instead of the C<sub list : Local> above (the C<list> argument to
308 C<Path> would make it match on the URL C<list> under C<books>, the
309 namespace of the current module). See "Action Types" in
310 L<Catalyst::Manual::Intro|Catalyst::Manual::Intro> as well as Part 5
311 of this tutorial (Authentication) for additional information. Another
312 popular but more advanced feature is C<Chained> actions that allow a
313 single URL to "chain together" multiple action method calls, each with
314 an appropriate number of arguments (see
315 L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained> for
319 =head1 CATALYST VIEWS
321 As mentioned in Part 2 of the tutorial, views are where you render
322 output, typically for display in the user's web browser (but also
323 possibly using other display output-generation systems). The code in
324 C<lib/MyApp/View> selects the I<type> of view to use, with the actual
325 rendering template found in the C<root> directory. As with virtually
326 every aspect of Catalyst, options abound when it comes to the specific
327 view technology you adopt inside your application. However, most
328 Catalyst applications use the Template Toolkit, known as TT (for more
329 information on TT, see L<http://www.template-toolkit.org>). Other
330 somewhat popular view technologies include Mason
331 (L<http://www.masonhq.com> and L<http://www.masonbook.com>) and
332 L<HTML::Template> (L<http://html-template.sourceforge.net>).
335 =head2 Create a Catalyst View
337 When using TT for the Catalyst view, there are two main helper scripts:
343 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
347 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
351 Both helpers are similar. C<TT> creates the C<lib/MyApp/View/TT.pm>
352 file and leaves the creation of any hierarchical template organization
353 entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
354 test cases will be discussed in Part 8.) C<TTSite>, on the other hand,
355 creates a modular and hierarchical view layout with
356 separate Template Toolkit (TT) files for common header and footer
357 information, configuration values, a CSS stylesheet, and more.
359 While C<TTSite> was useful to bootstrap a project, its use is now
360 deprecated and to be considered historical. For most Catalyst
361 applications it adds redundant functionality and structure; many in the
362 Catalyst community recommend that it's easier to learn both Catalyst and
363 Template Toolkit if you use the more basic C<TT> approach.
364 Consequently, this tutorial will use "plain old TT."
366 Enter the following command to enable the C<TT> style of view
367 rendering for this tutorial:
369 $ script/myapp_create.pl view TT TT
370 exists "/home/me/MyApp/script/../lib/MyApp/View"
371 exists "/home/me/MyApp/script/../t"
372 created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm"
373 created "/home/me/MyApp/script/../t/view_TT.t"
375 This simply creates a view called C<TT> (the second 'TT' argument) in
376 a file called C<TT.pm> (the first 'TT' argument). It is now up to you
377 to decide how you want to structure your view layout. For the
378 tutorial, we will start with a very simple TT template to initially
379 demonstrate the concepts, but quickly migrate to a more typical
380 "wrapper page" type of configuration (where the "wrapper" controls the
381 overall "look and feel" of your site from a single file or set of
384 Edit C<lib/MyApp/View/TT.pm> and you should see that the default
385 contents contains something similar to the following:
387 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
389 And update it to match:
392 # Change default TT extension
393 TEMPLATE_EXTENSION => '.tt2',
394 # Set the location for TT files
396 MyApp->path_to( 'root', 'src' ),
400 B<NOTE:> Make sure to add a comma after '.tt2' outside the single
403 This changes the default extension for Template Toolkit from '.tt' to
404 '.tt2' and changes the base directory for your template files from
405 C<root> to C<root/src>. These changes from the default are done mostly
406 to facilitate the application we're developing in this tutorial; as with
407 most things Perl, there's more than one way to do it...
410 =head2 Create a TT Template Page
412 First create a directory for book-related TT templates:
414 $ mkdir -p root/src/books
416 Then create C<root/src/books/list.tt2> in your editor and enter:
418 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
419 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
420 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
421 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
423 [% # Provide a title -%]
424 [% META title = 'Book List' -%]
427 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
428 [% # Display each book in a table row %]
429 [% FOREACH book IN books -%]
431 <td>[% book.title %]</td>
432 <td>[% book.rating %]</td>
437 As indicated by the inline comments above, the C<META title> line uses
438 TT's META feature to provide a title to the "wrapper" that we will
439 create later. Meanwhile, the C<FOREACH> loop iterates through each
440 C<book> model object and prints the C<title> and C<rating> fields.
442 If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT
443 code. TT supports a wide variety of directives for "calling" other
444 files, looping, conditional logic, etc. In general, TT simplifies the
445 usual range of Perl operators down to the single dot (C<.>) operator.
446 This applies to operations as diverse as method calls, hash lookups, and
447 list index values (see
448 L<http://search.cpan.org/perldoc?Template::Manual::Variables>
449 for details and examples). In addition to the usual C<Template> module
450 Pod documentation, you can access the TT manual at
451 L<http://search.cpan.org/perldoc?Template::Manual>.
453 B<TIP:> While you can build all sorts of complex logic into your TT
454 templates, you should in general keep the "code" part of your templates
455 as simple as possible. If you need more complex logic, create helper
456 methods in your model that abstract out a set of code into a single call
457 from your TT template. (Note that the same is true of your controller
458 logic as well -- complex sections of code in your controllers should
459 often be pulled out and placed into your model objects.)
462 =head2 Test Run The Application
464 To test your work so far, first start the development server:
466 $ script/myapp_server.pl
468 Then point your browser to L<http://localhost:3000> and you should
469 still get the Catalyst welcome page. Next, change the URL in your
470 browser to L<http://localhost:3000/books/list>. If you have
471 everything working so far, you should see a web page that displays
472 nothing other than our column headers for "Title", "Rating", and
473 "Author(s)" -- we will not see any books until we get the database and
476 If you run into problems getting your application to run correctly, it
477 might be helpful to refer to some of the debugging techniques covered in
478 the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the
482 =head1 CREATE A SQLITE DATABASE
484 In this step, we make a text file with the required SQL commands to
485 create a database table and load some sample data. We will use SQLite,
486 a popular database that is lightweight and easy to use. Open
487 C<myapp01.sql> in your editor and enter:
490 -- Create a very simple database to hold book and author information
493 id INTEGER PRIMARY KEY,
497 -- 'book_authors' is a many-to-many join table between books & authors
498 CREATE TABLE book_authors (
501 PRIMARY KEY (book_id, author_id)
503 CREATE TABLE authors (
504 id INTEGER PRIMARY KEY,
509 --- Load some sample data
511 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
512 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
513 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
514 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
515 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
516 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
517 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
518 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
519 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
520 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
521 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
522 INSERT INTO authors VALUES (7, 'Nathan', 'Torkington');
523 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
524 INSERT INTO book_authors VALUES (1, 1);
525 INSERT INTO book_authors VALUES (1, 2);
526 INSERT INTO book_authors VALUES (1, 3);
527 INSERT INTO book_authors VALUES (2, 4);
528 INSERT INTO book_authors VALUES (3, 5);
529 INSERT INTO book_authors VALUES (4, 6);
530 INSERT INTO book_authors VALUES (4, 7);
531 INSERT INTO book_authors VALUES (5, 8);
533 Then use the following command to build a C<myapp.db> SQLite database:
535 $ sqlite3 myapp.db < myapp01.sql
537 If you need to create the database more than once, you probably want to
538 issue the C<rm myapp.db> command to delete the database before you use
539 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
541 Once the C<myapp.db> database file has been created and initialized, you
542 can use the SQLite command line environment to do a quick dump of the
547 Enter ".help" for instructions
548 sqlite> select * from books;
549 1|CCSP SNRS Exam Certification Guide|5
550 2|TCP/IP Illustrated, Volume 1|5
551 3|Internetworking with TCP/IP Vol.1|4
553 5|Designing with Web Standards|5
559 $ sqlite3 myapp.db "select * from books"
560 1|CCSP SNRS Exam Certification Guide|5
561 2|TCP/IP Illustrated, Volume 1|5
562 3|Internetworking with TCP/IP Vol.1|4
564 5|Designing with Web Standards|5
566 As with most other SQL tools, if you are using the full "interactive"
567 environment you need to terminate your SQL commands with a ";" (it's not
568 required if you do a single SQL statement on the command line). Use
569 ".q" to exit from SQLite from the SQLite interactive mode and return to
570 your OS command prompt.
573 =head1 DATABASE ACCESS WITH C<DBIx::Class>
575 Catalyst can be used with virtually any form of persistent datastore
576 available via Perl. For example,
577 L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to easily
578 access databases through the traditional Perl C<DBI> interface. However,
579 most Catalyst applications use some form of ORM technology to
580 automatically create and save model objects as they are used. Although
581 L<Class::DBI|Class::DBI> has been a popular choice in the past, Matt
582 Trout's L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly
583 emerged as the Perl-based ORM technology of choice. Most new Catalyst
584 applications rely on DBIC, as will this tutorial.
587 =head2 Create a Dynamic DBIC Model
589 Use the C<create=dynamic> model helper option to build a model that
590 dynamically reads your database structure every time the application
593 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=dynamic dbi:SQLite:myapp.db
594 exists "/home/me/MyApp/script/../lib/MyApp/Model"
595 exists "/home/me/MyApp/script/../t"
596 exists "/home/me/MyApp/script/../lib/MyApp"
597 created "/home/me/MyApp/script/../lib/MyApp/Schema.pm"
598 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
599 created "/home/me/MyApp/script/../t/model_DB.t"
602 C<DB> is the name of the model class to be created by the helper in
603 C<lib/MyApp/Model>. C<DBIC::Schema> is the type of the model to
604 create. C<MyApp::Schema> is the name of the DBIC schema file written
605 to C<lib/MyApp/Schema.pm>. Because we specified C<create=dynamic> to
607 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
608 dynamically load the schema information from the database every time
609 the application starts. DBIC uses the schema to load other classes
610 that represent the tables in your database (DBIC refers to these
611 "table objects" as "result sources," see
612 L<DBIx::Class::ResultSource|DBIx::Class::ResultSource>). And finally,
613 C<dbi:SQLite:myapp.db> is the standard DBI connect string for use with
616 B<NOTE:> Although the C<create=dynamic> option to the DBIC helper
617 makes for a nifty demonstration, is only really suitable for very
618 small applications. After this demonstration, you should almost always
619 use the C<create=static> option that we switch to below.
622 =head1 ENABLE THE MODEL IN THE CONTROLLER
624 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
625 left disabled earlier (un-comment the line containing
626 C<[$c-E<gt>model('DB::Books')-E<gt>all]> and delete the next 2 lines):
630 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
635 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
636 # 'Context' that's used to 'glue together' the various components
637 # that make up the application
640 # Retrieve all of the book records as book model objects and store in the
641 # stash where they can be accessed by the TT template
642 $c->stash->{books} = [$c->model('DB::Books')->all];
644 # Set the TT template to use. You will almost always want to do this
645 # in your action methods (action methods respond to user input in
647 $c->stash->{template} = 'books/list.tt2';
650 B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
651 above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
652 two are equivalent. Either way, C<$c-E<gt>model> returns a
653 L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
654 against the database and iterating over the set of results that are
657 We are using the C<-E<gt>all> to fetch all of the books. DBIC
658 supports a wide variety of more advanced operations to easily do
659 things like filtering and sorting the results. For example, the
660 following could be used to sort the results by descending title:
662 $c->model('DB::Books')->search({}, {order_by => 'title DESC'});
664 Some other examples are provided in
665 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
666 additional information found at L<DBIx::Class::ResultSet/search>,
667 L<DBIx::Class::Manual::FAQ/Searching>,
668 L<DBIx::Class::Manual::Intro|DBIx::Class::Manual::Intro>
669 and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
672 =head2 Test Run The Application
674 First, let's enable an environment variable option that causes
675 DBIx::Class to dump the SQL statements it's using to access the database
676 (this option can provide extremely helpful troubleshooting information):
678 $ export DBIC_TRACE=1
680 This assumes you are using BASH as your shell -- adjust accordingly if
681 you are using a different shell (for example, under tcsh, use
682 C<setenv DBIC_TRACE 1>).
684 B<NOTE:> You can also set this in your code using
685 C<$class-E<gt>storage-E<gt>debug(1);>. See
686 L<DBIx::Class::Manual::Troubleshooting> for details (including options
687 to log to file instead of displaying to the Catalyst development server
690 Then launch the Catalyst development server. The log output should
691 display something like:
693 $script/myapp_server.pl
694 [debug] Debug messages enabled
695 [debug] Statistics enabled
696 [debug] Loaded plugins:
697 .----------------------------------------------------------------------------.
698 | Catalyst::Plugin::ConfigLoader 0.20 |
699 | Catalyst::Plugin::StackTrace 0.08 |
700 | Catalyst::Plugin::Static::Simple 0.20 |
701 '----------------------------------------------------------------------------'
703 [debug] Loaded dispatcher "Catalyst::Dispatcher"
704 [debug] Loaded engine "Catalyst::Engine::HTTP"
705 [debug] Found home "/home/me/MyApp"
706 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
707 [debug] Loaded components:
708 .-----------------------------------------------------------------+----------.
710 +-----------------------------------------------------------------+----------+
711 | MyApp::Controller::Books | instance |
712 | MyApp::Controller::Root | instance |
713 | MyApp::Model::DB | instance |
714 | MyApp::Model::DB::Authors | class |
715 | MyApp::Model::DB::BookAuthors | class |
716 | MyApp::Model::DB::Books | class |
717 | MyApp::View::TT | instance |
718 '-----------------------------------------------------------------+----------'
720 [debug] Loaded Private actions:
721 .----------------------+--------------------------------------+--------------.
722 | Private | Class | Method |
723 +----------------------+--------------------------------------+--------------+
724 | /default | MyApp::Controller::Root | default |
725 | /end | MyApp::Controller::Root | end |
726 | /index | MyApp::Controller::Root | index |
727 | /books/index | MyApp::Controller::Books | index |
728 | /books/list | MyApp::Controller::Books | list |
729 '----------------------+--------------------------------------+--------------'
731 [debug] Loaded Path actions:
732 .-------------------------------------+--------------------------------------.
734 +-------------------------------------+--------------------------------------+
737 | /books | /books/index |
738 | /books/list | /books/list |
739 '-------------------------------------+--------------------------------------'
741 [info] MyApp powered by Catalyst 5.7014
742 You can connect to your server at http://localhost:3000
744 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
745 the 'base' directory of your application, not inside the C<script>
746 directory itself or it will not be able to locate the C<myapp.db>
747 database file. You can use a fully qualified or a relative path to
748 locate the database file, but we did not specify that when we ran the
749 model helper earlier.
751 Some things you should note in the output above:
757 Catalyst::Model::DBIC::Schema dynamically created three model classes,
758 one to represent each of the three tables in our database
759 (C<MyApp::Model::DB::Authors>, C<MyApp::Model::DB::BookAuthors>,
760 and C<MyApp::Model::DB::Books>).
764 The "list" action in our Books controller showed up with a path of
769 Point your browser to L<http://localhost:3000> and you should still get
770 the Catalyst welcome page.
772 Next, to view the book list, change the URL in your browser to
773 L<http://localhost:3000/books/list>. You should get a list of the five
774 books loaded by the C<myapp01.sql> script above without any formatting.
775 The rating for each book should appear on each row, but the "Author(s)"
776 column will still be blank (we will fill that in later).
778 Also notice in the output of the C<script/myapp_server.pl> that DBIC
779 used the following SQL to retrieve the data:
781 SELECT me.id, me.title, me.rating FROM books me
783 because we enabled DBIC_TRACE.
785 You now have the beginnings of a simple but workable web application.
786 Continue on to future sections and we will develop the application
790 =head1 CREATE A WRAPPER FOR THE VIEW
792 When using TT, you can (and should!) create a wrapper that will
793 literally wrap content around each of your templates. This is
794 certainly useful as you have one main source for changing things that
795 will appear across your entire site/application instead of having to
796 edit many individual files.
799 =head2 Configure TT.pm For The Wrapper
801 In order to create a wrapper, you must first edit your TT view and
802 tell it where to find your wrapper file. Your TT view is located in
803 C<lib/MyApp/View/TT.pm>.
805 Edit C<lib/MyApp/View/TT.pm> and change it to match the following:
808 # Change default TT extension
809 TEMPLATE_EXTENSION => '.tt2',
810 # Set the location for TT files
812 MyApp->path_to( 'root', 'src' ),
814 # Set to 1 for detailed timer stats in your HTML as comments
816 # This is your wrapper template located in the 'root/src'
817 WRAPPER => 'wrapper.tt2',
821 =head2 Create the Wrapper Template File and Stylesheet
823 Next you need to set up your wrapper template. Basically, you'll want
824 to take the overall layout of your site and put it into this file.
825 For the tutorial, open C<root/src/wrapper.tt2> and input the following:
827 <?xml version="1.0" encoding="UTF-8"?>
828 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
829 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
831 <title>[% template.title or "My Catalyst App!" %]</title>
832 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
838 [%# Your logo could go here -%]
839 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
840 [%# Insert the page title -%]
841 <h1>[% template.title or site.title %]</h1>
848 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
849 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
850 <li><a href="mailto:nobody@nowhere.com" title="Contact Us">Contact Us</a></li>
852 </div><!-- end menu -->
855 [%# Status and error messages %]
856 <span class="message">[% status_msg %]</span>
857 <span class="error">[% error_msg %]</span>
858 [%# This is where TT will stick all of your template's contents. -%]
860 </div><!-- end content -->
861 </div><!-- end bodyblock -->
863 <div id="footer">Copyright (c) your name goes here</div>
864 </div><!-- end outer -->
869 Notice the status and error message sections in the code above:
871 <span class="status">[% status_msg %]</span>
872 <span class="error">[% error_msg %]</span>
874 If we set either message in the Catalyst stash (e.g.,
875 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
876 will be displayed whenever any view used by that request is rendered.
877 The C<message> and C<error> CSS styles can be customized to suit your
878 needs in the C<root/static/css/main.css> file we create below.
886 The Catalyst stash only lasts for a single HTTP request. If
887 you need to retain information across requests you can use
888 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
889 Catalyst sessions in the Authentication part of the tutorial).
893 Although it is beyond the scope of this tutorial, you may wish to use
894 a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
895 Dojo (L<http://www.dojotoolkit.org>).
900 =head3 Create A Basic Stylesheet
902 First create a central location for stylesheets under the static
905 $ mkdir root/static/css
907 Then open the file C<root/static/css/main.css> (the file referenced in
908 the stylesheet href link of our wrapper above) and add the following
927 background-color: #ddd;
933 padding: 0 0 50% 5px;
935 background-color: #ddd;
948 You may wish to check out a "CSS Framework" like Emastic
949 (L<http://code.google.com/p/emastic/>) as a way to quickly
950 provide lots of high-quality CSS functionality.
953 =head2 Test Run The Application
955 Restart the development server and hit "Reload" in your web browser
956 and you should now see a formatted version of our basic book list.
957 Although our wrapper and stylesheet are obviously very simple, you
958 should see how it allows us to control the overall look of an entire
959 website from two central files. To add new pages to the site, just
960 provide a template that fills in the C<content> section of our wrapper
961 template -- the wrapper will provide the overall feel of the page.
964 =head1 A STATIC DATABASE MODEL WITH C<DBIx::Class>
966 =head2 Create Static DBIC Schema Files
968 Unlike the previous DBIC section where we had C<create=dynamic>
969 automatically discover the structure of the database every time the
970 application started, here we will use static schema files for more
971 control. This is typical of most "real world" applications.
973 One option would be to manually create a separate schema file for each
974 table in the database, however, lets use the same
975 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> used
976 earlier with C<create=dynamic> to build the static files for us.
977 First, lets remove the schema file created earlier:
979 $ rm lib/MyApp/Schema.pm
981 Now regenerate the schema using the C<create=static> option:
983 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=static dbi:SQLite:myapp.db
984 exists "/home/kclark/dev/MyApp/script/../lib/MyApp/Model"
985 exists "/home/kclark/dev/MyApp/script/../t"
986 Dumping manual schema for MyApp::Schema to directory /home/kclark/dev/MyApp/script/../lib ...
987 Schema dump completed.
988 exists "/home/kclark/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
990 We could have also deleted C<lib/MyApp/Model/DB.pm>, but it would
991 have regenerated the same file (note the C<exists> in the output above).
992 If you take a look at C<lib/MyApp/Model/DB.pm>, it simply contains
993 a reference to the actual schema file in C<lib/MyApp/Schema.pm>
994 along with the database connect string.
996 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
998 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> as its base
999 class (L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> is
1000 only being used by the helper to load the schema once and then create
1001 the static files for us) and C<Schema.pm> only contains a call to the
1002 C<load_classes> method. You will also find that C<lib/MyApp>
1003 contains a C<Schema> subdirectory, with one file inside this directory
1004 for each of the tables in our simple database (C<Authors.pm>,
1005 C<BookAuthors.pm>, and C<Books.pm>). These three files were created
1006 based on the information found by
1007 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> as the
1010 The idea with all of the files created under C<lib/MyApp/Schema> by
1011 the C<create=static> option is to only edit the files below the C<# DO
1012 NOT MODIFY THIS OR ANYTHING ABOVE!> warning. If you place all of your
1013 changes below that point in the file, you can regenerate the
1014 automatically created information at the top of each file should your
1015 database structure get updated.
1017 Also note the "flow" of the model information across the various files
1018 and directories. Catalyst will initially load the model from
1019 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
1020 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally,
1021 the call to C<load_classes> in C<Schema.pm> will load each of the
1022 table-specific "results source" files from the C<lib/MyApp/Schema>
1023 subdirectory. These three table-specific DBIC schema files will then be
1024 used to create three table-specific Catalyst models every time the
1025 application starts (you can see these three model files listed in
1026 the debug output generated when you launch the application).
1029 =head2 Updating the Generated DBIC Schema Files
1031 Let's manually add some relationship information to the auto-generated
1032 schema files. First edit C<lib/MyApp/Schema/Books.pm> and
1033 add the following text below the C<# You can replace this text...>
1037 # Set relationships:
1042 # 1) Name of relationship, DBIC will create accessor with this name
1043 # 2) Name of the model class referenced by this relationship
1044 # 3) Column name in *foreign* table
1045 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::BookAuthors', 'book_id');
1049 # 1) Name of relationship, DBIC will create accessor with this name
1050 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1051 # 3) Name of belongs_to() relationship in model class of has_many() above
1052 # You must already have the has_many() defined to use a many_to_many().
1053 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1056 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1057 file. As with any Perl package, we need to end the last line with
1058 a statement that evaluates to C<true>. This is customarily done with
1059 C<1;> on a line by itself.
1061 This code defines both a C<has_many> and a C<many_to_many> relationship.
1062 The C<many_to_many> relationship is optional, but it makes it easier to
1063 map a book to its collection of authors. Without it, we would have to
1064 "walk" though the C<book_authors> table as in
1065 C<$book-E<gt>book_authors-E<gt>first-E<gt>author-E<gt>last_name>
1066 (we will see examples on how to use DBIC objects in your code soon,
1067 but note that because C<$book-E<gt>book_authors> can return multiple
1068 authors, we have to use C<first> to display a single author).
1069 C<many_to_many> allows us to use the shorter
1070 C<$book-E<gt>authors-E<gt>first-E<gt>last_name>.
1071 Note that you cannot define a C<many_to_many> relationship without
1072 also having the C<has_many> relationship in place.
1074 Then edit C<lib/MyApp/Schema/Authors.pm> and add relationship
1075 information as follows (again, be careful to put in above the C<1;> but
1076 below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1079 # Set relationships:
1084 # 1) Name of relationship, DBIC will create accessor with this name
1085 # 2) Name of the model class referenced by this relationship
1086 # 3) Column name in *foreign* table
1087 __PACKAGE__->has_many(book_author => 'MyApp::Schema::BookAuthors', 'author_id');
1091 # 1) Name of relationship, DBIC will create accessor with this name
1092 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1093 # 3) Name of belongs_to() relationship in model class of has_many() above
1094 # You must already have the has_many() defined to use a many_to_many().
1095 __PACKAGE__->many_to_many(books => 'book_author', 'book');
1097 Finally, do the same for the "join table,"
1098 C<lib/MyApp/Schema/BookAuthors.pm>:
1101 # Set relationships:
1106 # 1) Name of relationship, DBIC will create accessor with this name
1107 # 2) Name of the model class referenced by this relationship
1108 # 3) Column name in *this* table
1109 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Books', 'book_id');
1113 # 1) Name of relationship, DBIC will create accessor with this name
1114 # 2) Name of the model class referenced by this relationship
1115 # 3) Column name in *this* table
1116 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Authors', 'author_id');
1119 =head2 Run The Application
1121 Run the Catalyst "demo server" script with the C<DBIC_TRACE> option
1122 (it might still be enabled from earlier in the tutorial, but here
1123 is an alternate way to specify the option just in case):
1125 $ DBIC_TRACE=1 script/myapp_server.pl
1127 Make sure that the application loads correctly and that you see the
1128 three dynamically created model class (one for each of the
1129 table-specific schema classes we created).
1131 Then hit the URL L<http://localhost:3000/books/list> and be sure that
1132 the book list is displayed via the relationships established above. You
1133 can leave the development server running for the next step if you wish.
1135 B<Note:> You will not see the authors yet because the view does not yet
1136 use the new relations. Read on to the next section where we update the
1137 template to do that.
1140 =head1 UPDATING THE VIEW
1142 Let's add a new column to our book list page that takes advantage of
1143 the relationship information we manually added to our schema files
1144 in the previous section. Edit C<root/src/books/list.tt2> add add the
1145 following code below the existing table cell that contains
1146 C<book.rating> (IOW, add a new table cell below the existing two
1150 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1151 [% # loop in 'side effect notation' to load just the last names of the -%]
1152 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1153 [% # a value, so nothing will be printed here. But, if you have something -%]
1154 [% # in TT that does return a method and you don't want it printed, you -%]
1155 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1156 [% # call it and discard the return value. -%]
1157 [% tt_authors = [ ];
1158 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1159 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1160 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1161 ([% tt_authors.size | html %])
1162 [% # Use another TT vmethod to join & print the names & comma separators -%]
1163 [% tt_authors.join(', ') | html %]
1166 Then hit "Reload" in your browser (note that you don't need to reload
1167 the development server or use the C<-r> option when updating TT
1168 templates) and you should now see the number of authors each book has
1169 along with a comma-separated list of the authors' last names. (If you
1170 didn't leave the development server running from the previous step,
1171 you will obviously need to start it before you can refresh your
1174 If you are still running the development server with C<DBIC_TRACE>
1175 enabled, you should also now see five more C<SELECT> statements in the
1176 debug output (one for each book as the authors are being retrieved by
1179 SELECT me.id, me.title, me.rating FROM books me:
1180 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '1'
1181 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '2'
1182 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '3'
1183 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '4'
1184 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '5'
1186 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1187 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1188 and > and avoid various types of dangerous hacks against your
1189 application. In a real application, you would probably want to put
1190 "| html" at the end of every field where a user has control over the
1191 information that can appear in that field (and can therefore inject
1192 markup or code if you don't "neutralize" those fields). In addition to
1193 "| html", Template Toolkit has a variety of other useful filters that
1194 can found in the documentation for
1195 L<Template::Filters|Template::Filters>.
1198 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1200 In some situations, it can be useful to run your application and
1201 display a page without using a browser. Catalyst lets you do this
1202 using the C<scripts/myapp_test.pl> script. Just supply the URL you
1203 wish to display and it will run that request through the normal
1204 controller dispatch logic and use the appropriate view to render the
1205 output (obviously, complex pages may dump a lot of text to your
1206 terminal window). For example, if you type:
1208 $ script/myapp_test.pl "/books/list"
1210 You should get the same text as if you visited
1211 L<http://localhost:3000/books/list> with the normal development server
1212 and asked your browser to view the page source.
1215 =head1 OPTIONAL INFORMATION
1217 B<NOTE: The rest of this part of the tutorial is optional. You can
1218 skip to Part 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
1221 =head2 Using C<RenderView> for the Default View
1223 Once your controller logic has processed the request from a user, it
1224 forwards processing to your view in order to generate the appropriate
1225 response output. Catalyst uses
1226 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1227 default to automatically performs this operation. If you look in
1228 C<lib/MyApp/Controller/Root.pm>, you should see the empty
1229 definition for the C<sub end> method:
1231 sub end : ActionClass('RenderView') {}
1233 The following bullet points provide a quick overview of the
1234 C<RenderView> process:
1240 C<Root.pm> is designed to hold application-wide logic.
1244 At the end of a given user request, Catalyst will call the most specific
1245 C<end> method that's appropriate. For example, if the controller for a
1246 request has an C<end> method defined, it will be called. However, if
1247 the controller does not define a controller-specific C<end> method, the
1248 "global" C<end> method in C<Root.pm> will be called.
1252 Because the definition includes an C<ActionClass> attribute, the
1253 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1254 will be executed B<after> any code inside the definition of C<sub end>
1255 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1256 for more information on C<ActionClass>.
1260 Because C<sub end> is empty, this effectively just runs the default
1261 logic in C<RenderView>. However, you can easily extend the
1262 C<RenderView> logic by adding your own code inside the empty method body
1263 (C<{}>) created by the Catalyst Helpers when we first ran the
1264 C<catalyst.pl> to initialize our application. See
1265 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1266 detailed information on how to extended C<RenderView> in C<sub end>.
1271 =head2 Using The Default Template Name
1273 By default, C<Catalyst::View::TT> will look for a template that uses the
1274 same name as your controller action, allowing you to save the step of
1275 manually specifying the template name in each action. For example, this
1276 would allow us to remove the
1277 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1278 C<list> action in the Books controller. Open
1279 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1280 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1285 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1290 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1291 # 'Context' that's used to 'glue together' the various components
1292 # that make up the application
1293 my ($self, $c) = @_;
1295 # Retrieve all of the book records as book model objects and store in the
1296 # stash where they can be accessed by the TT template
1297 $c->stash->{books} = [$c->model('DB::Books')->all];
1299 # Set the TT template to use. You will almost always want to do this
1300 # in your action methods (actions methods respond to user input in
1301 # your controllers).
1302 #$c->stash->{template} = 'books/list.tt2';
1306 You should now be able to restart the development server as per the
1307 previous section and access the L<http://localhost:3000/books/list>
1310 B<NOTE:> Please note that if you use the default template technique,
1311 you will B<not> be able to use either the C<$c-E<gt>forward> or
1312 the C<$c-E<gt>detach> mechanisms (these are discussed in Part 2 and
1313 Part 9 of the Tutorial).
1316 =head2 Return To A Manually-Specified Template
1318 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1319 later in the tutorial, you should remove the comment from the
1320 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1322 $c->stash->{template} = 'books/list.tt2';
1324 Then delete the C<TEMPLATE_EXTENSION> line in
1325 C<lib/MyApp/View/TT.pm>.
1327 You should then be able to restart the development server and
1328 access L<http://localhost:3000/books/list> in the same manner as
1329 with earlier sections.
1334 Kennedy Clark, C<hkclark@gmail.com>
1336 Please report any errors, issues or suggestions to the author. The
1337 most recent version of the Catalyst Tutorial can be found at
1338 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
1340 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1341 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).