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"
96 This creates a similar skeletal structure to what we saw in Chapter 2 of
97 the tutorial, except with C<MyApp> and C<myapp> substituted for
98 C<Hello> and C<hello>.
101 =head1 EDIT THE LIST OF CATALYST PLUGINS
103 One of the greatest benefits of Catalyst is that it has such a large
104 library of plugins and base classes available. Plugins are used to
105 seamlessly integrate existing Perl modules into the overall Catalyst
106 framework. In general, they do this by adding additional methods to the
107 C<context> object (generally written as C<$c>) that Catalyst passes to
108 every component throughout the framework.
110 By default, Catalyst enables three plugins/flags:
118 Enables the Catalyst debug output you saw when we started the
119 C<script/myapp_server.pl> development server earlier. You can remove
120 this item when you place your application into production.
122 As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
123 Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
124 line of your application class will be plugins, Catalyst supports a
125 limited number of flag options (of these, C<-Debug> is the most
126 common). See the documentation for C<Catalyst.pm> to get details on
127 other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
129 If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
132 B<TIP>: Depending on your needs, it can be helpful to permanently
133 remove C<-Debug> from C<lib/MyApp.pm> and then use the C<-d> option
134 to C<script/myapp_server.pl> to re-enable it just for the development
135 server. We will not be using that approach in the tutorial, but feel
136 free to make use of it in your own projects.
140 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader>
142 C<ConfigLoader> provides an automatic way to load configurable
143 parameters for your application from a central
144 L<Config::General|Config::General> file (versus having the values
145 hard-coded inside your Perl modules). Config::General uses syntax
146 very similar to Apache configuration files. We will see how to use
147 this feature of Catalyst during the authentication and authorization
148 sections (Chapter 5 and Chapter 6).
150 B<IMPORTANT NOTE:> If you are using a version of
151 L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, be aware
152 that Catalyst changed the default format from YAML to the more
153 straightforward C<Config::General> style. This tutorial uses the
154 newer C<myapp.conf> file for C<Config::General>. However, Catalyst
155 supports both formats and will automatically use either C<myapp.conf>
156 or C<myapp.yml> (or any other format supported by
157 L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
158 L<Config::Any|Config::Any>). If you are using a version of
159 Catalyst::Devel prior to 1.06, you can convert to the newer format by
160 simply creating the C<myapp.conf> file manually and deleting
161 C<myapp.yml>. The default contents of the C<myapp.conf> you create
162 should only consist of one line:
166 B<TIP>: This script can be useful for converting between configuration
169 perl -Ilib -e 'use MyApp; use Config::General;
170 Config::General->new->save_file("myapp.conf", MyApp->config);'
174 L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple>
176 C<Static::Simple> provides an easy way to serve static content, such
177 as images and CSS files, from the development server.
181 For our application, we want to add one new plugin into the mix. To
182 do this, edit C<lib/MyApp.pm> (this file is generally referred to as
183 your I<application class>) and delete the lines with:
185 use Catalyst qw/-Debug
189 Then replace it with:
200 B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
201 techniques to load these plugins/flags. For example, you might see
204 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
206 Don't let these variations confuse you -- they all accomplish the same
209 This tells Catalyst to start using one new plugin,
210 L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
211 stack trace to the standard Catalyst "debug screen" (the screen
212 Catalyst sends to your browser when an error occurs). Be aware that
213 L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
214 browser, not in the console window from which you're running your
215 application, which is where logging output usually goes.
217 Make sure that when adding new plugins that you include them as a new
218 dependancies within the Makefile.PL file. For example, after adding
219 the StackTrace plugin the Makefile.PL should include the following
222 requires 'Catalyst::Plugin::StackTrace';
231 C<__PACKAGE__> is just a shorthand way of referencing the name of the
232 package where it is used. Therefore, in C<MyApp.pm>, C<__PACKAGE__>
233 is equivalent to C<MyApp>.
237 You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
238 before you put your application into production, but it can be helpful
243 When specifying plugins on the C<__PACKAGE__-E<gt>setup> line, you can
244 omit C<Catalyst::Plugin::> from the name. Additionally, you can
245 spread the plugin names across multiple lines as shown here, or place
246 them all on one (or more) lines as with the default configuration.
251 =head1 CREATE A CATALYST CONTROLLER
253 As discussed earlier, controllers are where you write methods that
254 interact with user input. Typically, controller methods respond to
255 C<GET> and C<POST> requests from the user's web browser.
257 Use the Catalyst C<create> script to add a controller for book-related
260 $ script/myapp_create.pl controller Books
261 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
262 exists "/home/me/MyApp/script/../t"
263 created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm"
264 created "/home/me/MyApp/script/../t/controller_Books.t"
266 Then edit C<lib/MyApp/Controller/Books.pm> (as discussed in Chapter 2 of
267 the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
268 each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
269 and add the following method to the controller:
273 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
278 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
279 # 'Context' that's used to 'glue together' the various components
280 # that make up the application
283 # Retrieve all of the book records as book model objects and store in the
284 # stash where they can be accessed by the TT template
285 # $c->stash->{books} = [$c->model('DB::Book')->all];
286 # But, for now, use this code until we create the model later
287 $c->stash->{books} = '';
289 # Set the TT template to use. You will almost always want to do this
290 # in your action methods (action methods respond to user input in
292 $c->stash->{template} = 'books/list.tt2';
295 B<TIP>: See Appendix 1 for tips on removing the leading spaces when
296 cutting and pasting example code from POD-based documents.
298 Programmers experienced with object-oriented Perl should recognize
299 C<$self> as a reference to the object where this method was called.
300 On the other hand, C<$c> will be new to many Perl programmers who have
301 not used Catalyst before (it's sometimes written as C<$context>). The
302 Context object is automatically passed to all Catalyst components. It
303 is used to pass information between components and provide access to
304 Catalyst and plugin functionality.
306 Catalyst actions are regular Perl methods, but they make use of
307 attributes (the "C<: Local>" next to the "C<sub list>" in the code
308 above) to provide additional information to the Catalyst dispatcher
309 logic (note that the space between the colon and the attribute name is
310 optional; you will see attributes written both ways). Most Catalyst
311 Controllers use one of five action types:
317 B<:Private> -- Use C<:Private> for methods that you want to make into
318 an action, but you do not want Catalyst to directly expose
319 to your users. Catalyst will not map C<:Private> methods to a URI.
320 Use them for various sorts of "special" methods (the C<begin>,
321 C<auto>, etc. discussed below) or for methods you want to be able to
322 C<forward> or C<detach> to. (If the method is a plain old "helper
323 method" that you don't want to be an action at all, then just define
324 the method without any attribute -- you can call it in your code, but
325 the Catalyst dispatcher will ignore it.)
327 There are five types of "special" build-in C<:Private> actions:
328 C<begin>, C<end>, C<default>, C<index>, and C<auto>.
334 With C<begin>, C<end>, C<default>, C<index> private actions, only the
335 most specific action of each type will be called. For example, if you
336 define a C<begin> action in your controller it will I<override> a
337 C<begin> action in your application/root controller -- I<only> the
338 action in your controller will be called.
342 Unlike the other actions where only a single method is called for each
343 request, I<every> auto action along the chain of namespaces will be
344 called. Each C<auto> action will be called I<from the application/root
345 controller down through the most specific class>.
351 B<:Path> -- C<:Path> actions let you map a method to an explicit URI
352 path. For example, "C<:Path('list')>" in
353 C<lib/MyApp/Controller/Books.pm> would match on the URL
354 C<http://localhost:3000/books/list> but "C<:Path('/list')>" would match
355 on C<http://localhost:3000/list>. You can use C<:Args()> to specify
356 how many arguments an action should accept. See
357 L<Catalyst::Manual::Intro/Action_types> for more information and a few
362 B<:Local> -- C<:Local> is merely a shorthand for
363 "C<:Path('_name_of_method_')>". For example, these are equivalent:
364 "C<sub create_book :Local {...}>" and
365 "C<sub create_book :Path('create_book') {...}>".
369 B<:Global> -- C<:Global> is merely a shorthand for
370 "C<:Path('/_name_of_method_')>". For example, these are equivalent:
371 "C<sub create_book :Global {...}>" and
372 "C<sub create_book :Path('/create_book') {...}>".
376 B<:Chained> -- Newer Catalyst applications tend to use the Chained
377 dispatch form of action types because of its power and flexibility.
378 It allows a series of controller methods to be automatically dispatched
379 to service a single user request. See
380 L<Catalyst::Manual::Tutorial::04_BasicCRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
381 and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
382 for more information on chained actions.
386 You should refer to L<Catalyst::Manual::Intro/Action_types> for
387 additional information and for coverage of some lesser-used action
388 types not discussed here (C<Regex> and C<LocalRegex>).
391 =head1 CATALYST VIEWS
393 As mentioned in Chapter 2 of the tutorial, views are where you render
394 output, typically for display in the user's web browser (but also
395 possibly using into output-generation systems, such as PDF or JSON).
396 The code in C<lib/MyApp/View> selects the I<type> of view to use, with
397 the actual rendering template found in the C<root> directory. As with
398 virtually every aspect of Catalyst, options abound when it comes to the
399 specific view technology you adopt inside your application. However,
400 most Catalyst applications use the Template Toolkit, known as TT (for
401 more information on TT, see L<http://www.template-toolkit.org>). Other
402 somewhat popular view technologies include Mason
403 (L<http://www.masonhq.com> and L<http://www.masonbook.com>) and
404 L<HTML::Template> (L<http://html-template.sourceforge.net>).
407 =head2 Create a Catalyst View
409 When using TT for the Catalyst view, there are two main helper scripts:
415 L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>
419 L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite>
423 Both helpers are similar. C<TT> creates the C<lib/MyApp/View/TT.pm>
424 file and leaves the creation of any hierarchical template organization
425 entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
426 test cases will be discussed in Chapter 8.) C<TTSite>, on the other hand,
427 creates a modular and hierarchical view layout with
428 separate Template Toolkit (TT) files for common header and footer
429 information, configuration values, a CSS stylesheet, and more.
431 While C<TTSite> was useful to bootstrap a project, its use is now
432 deprecated and it should be considered historical. For most Catalyst
433 applications it adds redundant functionality and structure; many in the
434 Catalyst community recommend that it's easier to learn both Catalyst and
435 Template Toolkit if you use the more basic C<TT> approach.
436 Consequently, this tutorial will use "plain old TT."
438 Enter the following command to enable the C<TT> style of view
439 rendering for this tutorial:
441 $ script/myapp_create.pl view TT TT
442 exists "/home/me/MyApp/script/../lib/MyApp/View"
443 exists "/home/me/MyApp/script/../t"
444 created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm"
445 created "/home/me/MyApp/script/../t/view_TT.t"
447 This simply creates a view called C<TT> (the second 'TT' argument) in
448 a file called C<TT.pm> (the first 'TT' argument). It is now up to you
449 to decide how you want to structure your view layout. For the
450 tutorial, we will start with a very simple TT template to initially
451 demonstrate the concepts, but quickly migrate to a more typical
452 "wrapper page" type of configuration (where the "wrapper" controls the
453 overall "look and feel" of your site from a single file or set of
456 Edit C<lib/MyApp/View/TT.pm> and you should see that the default
457 contents contains something similar to the following:
459 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
461 And update it to match:
464 # Change default TT extension
465 TEMPLATE_EXTENSION => '.tt2',
466 # Set the location for TT files
468 MyApp->path_to( 'root', 'src' ),
472 B<NOTE:> Make sure to add a comma after '.tt2' outside the single
475 This changes the default extension for Template Toolkit from '.tt' to
476 '.tt2' and changes the base directory for your template files from
477 C<root> to C<root/src>. These changes from the default are done mostly
478 to facilitate the application we're developing in this tutorial; as with
479 most things Perl, there's more than one way to do it...
481 B<Note:> We will use C<root/src> as the base directory for our
482 template files, which a full naming convention of
483 C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
484 use C<root/> as the base (with a full filename pattern of
485 C<root/_controller_name_/_action_name_.tt2>).
488 =head2 Create a TT Template Page
490 First create a directory for book-related TT templates:
492 $ mkdir -p root/src/books
494 Then create C<root/src/books/list.tt2> in your editor and enter:
496 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
497 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
498 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
499 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
501 [% # Provide a title -%]
502 [% META title = 'Book List' -%]
505 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
506 [% # Display each book in a table row %]
507 [% FOREACH book IN books -%]
509 <td>[% book.title %]</td>
510 <td>[% book.rating %]</td>
516 As indicated by the inline comments above, the C<META title> line uses
517 TT's META feature to provide a title to the "wrapper" that we will
518 create later. Meanwhile, the C<FOREACH> loop iterates through each
519 C<book> model object and prints the C<title> and C<rating> fields.
521 The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
522 supports a wide variety of directives for "calling" other files,
523 looping, conditional logic, etc. In general, TT simplifies the usual
524 range of Perl operators down to the single dot (C<.>) operator. This
525 applies to operations as diverse as method calls, hash lookups, and list
527 L<http://search.cpan.org/perldoc?Template::Manual::Variables> for
528 details and examples). In addition to the usual C<Template> module Pod
529 documentation, you can access the TT manual at
530 L<http://search.cpan.org/perldoc?Template::Manual>.
532 B<TIP:> While you can build all sorts of complex logic into your TT
533 templates, you should in general keep the "code" part of your templates
534 as simple as possible. If you need more complex logic, create helper
535 methods in your model that abstract out a set of code into a single call
536 from your TT template. (Note that the same is true of your controller
537 logic as well -- complex sections of code in your controllers should
538 often be pulled out and placed into your model objects.)
541 =head2 Test Run The Application
543 To test your work so far, first start the development server:
545 $ script/myapp_server.pl
547 Then point your browser to L<http://localhost:3000> and you should
548 still get the Catalyst welcome page. Next, change the URL in your
549 browser to L<http://localhost:3000/books/list>. If you have
550 everything working so far, you should see a web page that displays
551 nothing other than our column headers for "Title", "Rating", and
552 "Author(s)" -- we will not see any books until we get the database and
555 If you run into problems getting your application to run correctly, it
556 might be helpful to refer to some of the debugging techniques covered in
557 the L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> chapter of the
561 =head1 CREATE A SQLITE DATABASE
563 In this step, we make a text file with the required SQL commands to
564 create a database table and load some sample data. We will use SQLite,
565 a popular database that is lightweight and easy to use. Open
566 C<myapp01.sql> in your editor and enter:
569 -- Create a very simple database to hold book and author information
572 id INTEGER PRIMARY KEY,
576 -- 'book_author' is a many-to-many join table between books & authors
577 CREATE TABLE book_author (
580 PRIMARY KEY (book_id, author_id)
582 CREATE TABLE author (
583 id INTEGER PRIMARY KEY,
588 --- Load some sample data
590 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
591 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
592 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
593 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
594 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
595 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
596 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
597 INSERT INTO author VALUES (3, 'Christian', 'Degu');
598 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
599 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
600 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
601 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
602 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
603 INSERT INTO book_author VALUES (1, 1);
604 INSERT INTO book_author VALUES (1, 2);
605 INSERT INTO book_author VALUES (1, 3);
606 INSERT INTO book_author VALUES (2, 4);
607 INSERT INTO book_author VALUES (3, 5);
608 INSERT INTO book_author VALUES (4, 6);
609 INSERT INTO book_author VALUES (4, 7);
610 INSERT INTO book_author VALUES (5, 8);
612 Then use the following command to build a C<myapp.db> SQLite database:
614 $ sqlite3 myapp.db < myapp01.sql
616 If you need to create the database more than once, you probably want to
617 issue the C<rm myapp.db> command to delete the database before you use
618 the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
620 Once the C<myapp.db> database file has been created and initialized, you
621 can use the SQLite command line environment to do a quick dump of the
626 Enter ".help" for instructions
627 sqlite> select * from book;
628 1|CCSP SNRS Exam Certification Guide|5
629 2|TCP/IP Illustrated, Volume 1|5
630 3|Internetworking with TCP/IP Vol.1|4
632 5|Designing with Web Standards|5
638 $ sqlite3 myapp.db "select * from book"
639 1|CCSP SNRS Exam Certification Guide|5
640 2|TCP/IP Illustrated, Volume 1|5
641 3|Internetworking with TCP/IP Vol.1|4
643 5|Designing with Web Standards|5
645 As with most other SQL tools, if you are using the full "interactive"
646 environment you need to terminate your SQL commands with a ";" (it's not
647 required if you do a single SQL statement on the command line). Use
648 ".q" to exit from SQLite from the SQLite interactive mode and return to
649 your OS command prompt.
651 Please note that here we have chosen to use 'singular' table names. This
652 is because the default inflection code for L<DBIx::Class:Schema::Loader>
653 does NOT handle plurals. There has been much philosophical discussion
654 on whether table names should be plural or singular. There is no one
655 correct answer, as long as one makes a choice and remains consistent
656 with it. If you prefer plural table names (e.g. they are easier and
657 more natural to read) then you will need to pass it an inflect_map
658 option. See L<DBIx::Class:Schema::Loader> for more information.
660 For using other databases, such as PostgreSQL or MySQL, see
661 L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices>.
664 =head1 DATABASE ACCESS WITH DBIx::Class
666 Catalyst can be used with virtually any form of datastore available
667 via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
668 can be used to access databases through the traditional Perl C<DBI>
669 interface or you can use a model to access files of any type on the
670 filesystem. However, most Catalyst applications use some form of
671 object-relational mapping (ORM) technology to create objects
672 associated with tables in a relational database. Matt Trout's
673 L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
674 as the Perl-based ORM technology of choice. Most new Catalyst
675 applications rely on DBIx::Class, as will this tutorial.
677 Although DBIx::Class has included support for a C<create=dynamic> mode
678 to automatically read the database structure every time the
679 application starts, it's use is no longer recommended. While it can
680 make for "flashy" demos, the use of the C<create=static> mode we use
681 below can be implemented just as quickly and provides many advantages
682 (such as the ability to add your own methods to the overall DBIC
683 framework, a technique that we see in Chapter 4).
686 =head2 Make Sure You Have a Recent Version of the DBIx::Class Model
688 First, let's be sure we have a recent version of the DBIC helper,
689 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
690 running this command:
692 $ perl -MCatalyst::Model::DBIC::Schema -e \
693 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
696 Please note the '\' above. Depending on your environment, you might
697 be able to cut and paste the text as shown or need to remove the '\'
698 character to that the command is all on a single line.
700 If you don't have version 0.23 or higher, please run this command
701 to install it directly from CPAN:
703 $ sudo cpan Catalyst::Model::DBIC::Schema
705 And re-run the version print command to verify that you are now at
709 =head2 Create Static DBIx::Class Schema Files
711 Before you continue, make sure your C<myapp.db> database file is in
712 the application's topmost directory. Now use the model helper with
713 the C<create=static> option to read the database with
714 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
715 automatically build the required files for us:
717 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
718 create=static dbi:SQLite:myapp.db
719 exists "/home/me/MyApp/script/../lib/MyApp/Model"
720 exists "/home/me/MyApp/script/../t"
721 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
722 Schema dump completed.
723 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
724 created "/home/me/MyApp/script/../t/model_DB.t"
726 Please note the '\' above. Depending on your environment, you might
727 be able to cut and paste the text as shown or need to remove the '\'
728 character to that the command is all on a single line.
730 The C<script/myapp_create.pl> command breaks down like this:
736 C<DB> is the name of the model class to be created by the helper in
741 C<DBIC::Schema> is the type of the model to create.
745 C<MyApp::Schema> is the name of the DBIC schema file written to
746 C<lib/MyApp/Schema.pm>.
750 C<create=static> causes
751 L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
752 load the schema as it runs and then write that information out
757 C<components=TimeStamp> causes the help to include the
758 L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp> DBIC component.
762 And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
767 If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
768 only contains a call to the C<load_namespaces> method. You will also
769 find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
770 has a subdirectory called "Result". This "Result" subdirectory then
771 has files named according to each of the tables in our simple database
772 (C<Author.pm>, C<BookAuthor.pm>, and C<Book.pm>). These three
773 files are called "Result Classes" in DBIx::Class nomenclature. Although the
774 Result Class files are named after tables in our database, the classes
775 correspond to the I<row-level data> that is returned by DBIC (more on
776 this later, especially in
777 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
779 The idea with the Result Source files created under
780 C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
781 edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
782 warning. If you place all of your changes below that point in the
783 file, you can regenerate the automatically created information at the
784 top of each file should your database structure get updated.
786 Also note the "flow" of the model information across the various files
787 and directories. Catalyst will initially load the model from
788 C<lib/MyApp/Model/DB.pm>. This file contains a reference to
789 C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, the
790 call to C<load_namespaces> in C<Schema.pm> will load each of the
791 "Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
792 The final outcome is that Catalyst will dynamically create three
793 table-specific Catalyst models every time the application starts (you
794 can see these three model files listed in the debug output generated
795 when you launch the application).
797 B<NOTE:> Older versions of
798 L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
799 deprecated DBIx::Class C<load_classes> technique instead of the newer
800 C<load_namspaces>. For new applications, please try to use
801 C<load_namespaces> since it more easily supports a very useful DBIC
802 technique called "ResultSet Classes." If you need to convert an
803 existing application from "load_classes" to "load_namespaces," you can
804 use this process to automate the migration (but first make sure you
805 have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
807 $ # First delete the existing schema file to disable "compatibility" mode
808 $ rm lib/MyApp/Schema.pm
810 $ # Then re-run the helper to build the files for "load_namespaces"
811 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
812 create=static dbi:SQLite:myapp.db
814 $ # Now convert the existing files over
815 $ cd lib/MyApp/Schema
816 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
817 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
818 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
821 $ # And finally delete the old files
822 $ rm lib/MyApp/Schema/*.pm
824 The "C<perl -MIO::ALL ...>" script will copy all the customized
825 relationship (and other) information below "C<# DO NOT MODIFY>" line
826 from the old files in C<lib/MyApp/Schema> to the new files in
827 C<lib/MyApp/Schema/Result> (we will be starting to add some
828 "customized relationship information in the section below).
831 =head1 ENABLE THE MODEL IN THE CONTROLLER
833 Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
834 left disabled earlier so that your version matches the following (un-
835 comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
836 and delete the next 2 lines):
840 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
845 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
846 # 'Context' that's used to 'glue together' the various components
847 # that make up the application
850 # Retrieve all of the book records as book model objects and store in the
851 # stash where they can be accessed by the TT template
852 $c->stash->{books} = [$c->model('DB::Book')->all];
854 # Set the TT template to use. You will almost always want to do this
855 # in your action methods (action methods respond to user input in
857 $c->stash->{template} = 'books/list.tt2';
860 B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
861 above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
862 two are equivalent. Either way, C<$c-E<gt>model> returns a
863 L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
864 against the database and iterating over the set of results that is
867 We are using the C<-E<gt>all> to fetch all of the books. DBIC
868 supports a wide variety of more advanced operations to easily do
869 things like filtering and sorting the results. For example, the
870 following could be used to sort the results by descending title:
872 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
874 Some other examples are provided in
875 L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
876 additional information found at L<DBIx::Class::ResultSet/search>,
877 L<DBIx::Class::Manual::FAQ/Searching>,
878 L<DBIx::Class::Manual::Intro|DBIx::Class::Manual::Intro>
879 and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
882 =head2 Test Run The Application
884 First, let's enable an environment variable that causes DBIx::Class to
885 dump the SQL statements used to access the database. This is a
886 helpful trick when you are trying to debug your database-oriented
889 $ export DBIC_TRACE=1
891 This assumes you are using bash as your shell -- adjust accordingly if
892 you are using a different shell (for example, under tcsh, use
893 C<setenv DBIC_TRACE 1>).
895 B<NOTE:> You can also set this in your code using
896 C<$class-E<gt>storage-E<gt>debug(1);>. See
897 L<DBIx::Class::Manual::Troubleshooting> for details (including options
898 to log to a file instead of displaying to the Catalyst development server
901 Then launch the Catalyst development server. The log output should
902 display something like:
904 $ script/myapp_server.pl
905 [debug] Debug messages enabled
906 [debug] Statistics enabled
907 [debug] Loaded plugins:
908 .----------------------------------------------------------------------------.
909 | Catalyst::Plugin::ConfigLoader 0.22 |
910 | Catalyst::Plugin::StackTrace 0.09 |
911 | Catalyst::Plugin::Static::Simple 0.21 |
912 '----------------------------------------------------------------------------'
914 [debug] Loaded dispatcher "Catalyst::Dispatcher"
915 [debug] Loaded engine "Catalyst::Engine::HTTP"
916 [debug] Found home "/home/me/MyApp"
917 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
918 [debug] Loaded components:
919 .-----------------------------------------------------------------+----------.
921 +-----------------------------------------------------------------+----------+
922 | MyApp::Controller::Books | instance |
923 | MyApp::Controller::Root | instance |
924 | MyApp::Model::DB | instance |
925 | MyApp::Model::DB::Author | class |
926 | MyApp::Model::DB::Book | class |
927 | MyApp::Model::DB::BookAuthor | class |
928 | MyApp::View::TT | instance |
929 '-----------------------------------------------------------------+----------'
931 [debug] Loaded Private actions:
932 .----------------------+--------------------------------------+--------------.
933 | Private | Class | Method |
934 +----------------------+--------------------------------------+--------------+
935 | /default | MyApp::Controller::Root | default |
936 | /end | MyApp::Controller::Root | end |
937 | /index | MyApp::Controller::Root | index |
938 | /books/index | MyApp::Controller::Books | index |
939 | /books/list | MyApp::Controller::Books | list |
940 '----------------------+--------------------------------------+--------------'
942 [debug] Loaded Path actions:
943 .-------------------------------------+--------------------------------------.
945 +-------------------------------------+--------------------------------------+
948 | /books | /books/index |
949 | /books/list | /books/list |
950 '-------------------------------------+--------------------------------------'
952 [info] MyApp powered by Catalyst 5.80003
953 You can connect to your server at http://debian:3000
955 B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
956 the 'base' directory of your application, not inside the C<script>
957 directory itself or it will not be able to locate the C<myapp.db>
958 database file. You can use a fully qualified or a relative path to
959 locate the database file, but we did not specify that when we ran the
960 model helper earlier.
962 Some things you should note in the output above:
968 Catalyst::Model::DBIC::Schema dynamically created three model classes,
969 one to represent each of the three tables in our database
970 (C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
971 and C<MyApp::Model::DB::Book>).
975 The "list" action in our Books controller showed up with a path of
980 Point your browser to L<http://localhost:3000> and you should still get
981 the Catalyst welcome page.
983 Next, to view the book list, change the URL in your browser to
984 L<http://localhost:3000/books/list>. You should get a list of the five
985 books loaded by the C<myapp01.sql> script above without any formatting.
986 The rating for each book should appear on each row, but the "Author(s)"
987 column will still be blank (we will fill that in later).
989 Also notice in the output of the C<script/myapp_server.pl> that
990 DBIx::Class used the following SQL to retrieve the data:
992 SELECT me.id, me.title, me.rating FROM book me
994 because we enabled DBIC_TRACE.
996 You now have the beginnings of a simple but workable web application.
997 Continue on to future sections and we will develop the application
1001 =head1 CREATE A WRAPPER FOR THE VIEW
1003 When using TT, you can (and should) create a wrapper that will
1004 literally wrap content around each of your templates. This is
1005 certainly useful as you have one main source for changing things that
1006 will appear across your entire site/application instead of having to
1007 edit many individual files.
1010 =head2 Configure TT.pm For The Wrapper
1012 In order to create a wrapper, you must first edit your TT view and
1013 tell it where to find your wrapper file. Your TT view is located in
1014 C<lib/MyApp/View/TT.pm>.
1016 Edit C<lib/MyApp/View/TT.pm> and change it to match the following:
1018 __PACKAGE__->config(
1019 # Change default TT extension
1020 TEMPLATE_EXTENSION => '.tt2',
1021 # Set the location for TT files
1023 MyApp->path_to( 'root', 'src' ),
1025 # Set to 1 for detailed timer stats in your HTML as comments
1027 # This is your wrapper template located in the 'root/src'
1028 WRAPPER => 'wrapper.tt2',
1032 =head2 Create the Wrapper Template File and Stylesheet
1034 Next you need to set up your wrapper template. Basically, you'll want
1035 to take the overall layout of your site and put it into this file.
1036 For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1038 <?xml version="1.0" encoding="UTF-8"?>
1039 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
1040 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
1042 <title>[% template.title or "My Catalyst App!" %]</title>
1043 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1049 [%# Your logo could go here -%]
1050 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1051 [%# Insert the page title -%]
1052 <h1>[% template.title or site.title %]</h1>
1055 <div id="bodyblock">
1059 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1060 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1062 </div><!-- end menu -->
1065 [%# Status and error messages %]
1066 <span class="message">[% status_msg %]</span>
1067 <span class="error">[% error_msg %]</span>
1068 [%# This is where TT will stick all of your template's contents. -%]
1070 </div><!-- end content -->
1071 </div><!-- end bodyblock -->
1073 <div id="footer">Copyright (c) your name goes here</div>
1074 </div><!-- end outer -->
1079 Notice the status and error message sections in the code above:
1081 <span class="status">[% status_msg %]</span>
1082 <span class="error">[% error_msg %]</span>
1084 If we set either message in the Catalyst stash (e.g.,
1085 C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1086 will be displayed whenever any view used by that request is rendered.
1087 The C<message> and C<error> CSS styles can be customized to suit your
1088 needs in the C<root/static/css/main.css> file we create below.
1096 The Catalyst stash only lasts for a single HTTP request. If
1097 you need to retain information across requests you can use
1098 L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
1099 Catalyst sessions in the Authentication chapter of the tutorial).
1103 Although it is beyond the scope of this tutorial, you may wish to use
1104 a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
1105 Dojo (L<http://www.dojotoolkit.org>).
1110 =head3 Create A Basic Stylesheet
1112 First create a central location for stylesheets under the static
1115 $ mkdir root/static/css
1117 Then open the file C<root/static/css/main.css> (the file referenced in
1118 the stylesheet href link of our wrapper above) and add the following
1137 background-color: #ddd;
1143 padding: 0 0 50% 5px;
1144 font-weight: normal;
1145 background-color: #ddd;
1158 You may wish to check out a "CSS Framework" like Emastic
1159 (L<http://code.google.com/p/emastic/>) as a way to quickly
1160 provide lots of high-quality CSS functionality.
1163 =head2 Test Run The Application
1165 Restart the development server and hit "Reload" in your web browser
1166 and you should now see a formatted version of our basic book list.
1167 Although our wrapper and stylesheet are obviously very simple, you
1168 should see how it allows us to control the overall look of an entire
1169 website from two central files. To add new pages to the site, just
1170 provide a template that fills in the C<content> section of our wrapper
1171 template -- the wrapper will provide the overall feel of the page.
1174 =head2 Updating the Generated DBIx::Class Result Class Files
1176 Let's manually add some relationship information to the auto-generated
1177 Result Class files. (Note: if you are using a database other than
1178 SQLite, such as PostgreSQL, then the relationship could have been
1179 automatically placed in the Result Class files. If so, you can skip
1180 this step.) First edit C<lib/MyApp/Schema/Result/Book.pm> and add the
1181 following text below the C<# You can replace this text...> comment:
1184 # Set relationships:
1189 # 1) Name of relationship, DBIC will create accessor with this name
1190 # 2) Name of the model class referenced by this relationship
1191 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1192 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthor', 'book_id');
1196 # 1) Name of relationship, DBIC will create accessor with this name
1197 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1198 # 3) Name of belongs_to() relationship in model class of has_many() above
1199 # You must already have the has_many() defined to use a many_to_many().
1200 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1203 B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1204 file. As with any Perl package, we need to end the last line with
1205 a statement that evaluates to C<true>. This is customarily done with
1206 C<1;> on a line by itself.
1208 This code defines both a C<has_many> and a C<many_to_many>
1209 relationship. The C<many_to_many> relationship is optional, but it
1210 makes it easier to map a book to its collection of authors. Without
1211 it, we would have to "walk" though the C<book_author> table as in
1212 C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
1213 will see examples on how to use DBIx::Class objects in your code soon,
1214 but note that because C<$book-E<gt>book_author> can return multiple
1215 authors, we have to use C<first> to display a single author).
1216 C<many_to_many> allows us to use the shorter C<$book-E<gt>author-
1217 E<gt>first-E<gt>last_name>. Note that you cannot define a
1218 C<many_to_many> relationship without also having the C<has_many>
1219 relationship in place.
1221 Then edit C<lib/MyApp/Schema/Result/Author.pm> and add relationship
1222 information as follows (again, be careful to put in above the C<1;> but
1223 below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1226 # Set relationships:
1231 # 1) Name of relationship, DBIC will create an accessor with this name
1232 # 2) Name of the model class referenced by this relationship
1233 # 3) Column name in *foreign* table (aka, foreign key in peer table)
1234 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthor', 'author_id');
1238 # 1) Name of relationship, DBIC will create accessor with this name
1239 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1240 # 3) Name of belongs_to() relationship in model class of has_many() above
1241 # You must already have the has_many() defined to use a many_to_many().
1242 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
1244 Finally, do the same for the "join table,"
1245 C<lib/MyApp/Schema/Result/BookAuthor.pm>:
1248 # Set relationships:
1253 # 1) Name of relationship, DBIC will create accessor with this name
1254 # 2) Name of the model class referenced by this relationship
1255 # 3) Column name in *this* table
1256 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Book', 'book_id');
1260 # 1) Name of relationship, DBIC will create accessor with this name
1261 # 2) Name of the model class referenced by this relationship
1262 # 3) Column name in *this* table
1263 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Author', 'author_id');
1266 =head2 Run The Application
1268 Run the Catalyst development server script with the C<DBIC_TRACE> option
1269 (it might still be enabled from earlier in the tutorial, but here is an
1270 alternate way to specify the option just in case):
1272 $ DBIC_TRACE=1 script/myapp_server.pl
1274 Make sure that the application loads correctly and that you see the
1275 three dynamically created model class (one for each of the
1276 Result Classes we created).
1278 Then hit the URL L<http://localhost:3000/books/list> with your browser
1279 and be sure that the book list is displayed via the relationships
1280 established above. You can leave the development server running for
1281 the next step if you wish.
1283 B<Note:> You will not see the authors yet because the view does not yet
1284 use the new relations. Read on to the next section where we update the
1285 template to do that.
1288 =head1 UPDATING THE VIEW
1290 Let's add a new column to our book list page that takes advantage of
1291 the relationship information we manually added to our schema files in
1292 the previous section. Edit C<root/src/books/list.tt2> and replace
1293 the "empty" table cell "<td></td>" with the following:
1297 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1298 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1299 [% # loop in 'side effect notation' to load just the last names of the -%]
1300 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
1301 [% # a value, so nothing will be printed here. But, if you have something -%]
1302 [% # in TT that does return a value and you don't want it printed, you -%]
1303 [% # 1) assign it to a bogus value, or -%]
1304 [% # 2) use the CALL keyword to call it and discard the return value. -%]
1305 [% tt_authors = [ ];
1306 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1307 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1308 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1309 ([% tt_authors.size | html %])
1310 [% # Use another TT vmethod to join & print the names & comma separators -%]
1311 [% tt_authors.join(', ') | html %]
1315 B<IMPORTANT NOTE:> You should keep as much "logic code" as possible
1316 out of your views. Instead, this kind of logic belongs in your model
1317 (the same goes for controllers -- keep them as "thin" as possible and
1318 push all of the "complicated code" out to your model objects). Avoid
1319 code like you see in the previous example -- we are only using it here
1320 to show some extra features in TT until we get to the more advanced
1321 model features we will see in Chapter 4 (see
1322 L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1324 Then hit "Reload" in your browser (note that you don't need to reload
1325 the development server or use the C<-r> option when updating TT
1326 templates) and you should now see the number of authors each book has
1327 along with a comma-separated list of the authors' last names. (If you
1328 didn't leave the development server running from the previous step,
1329 you will obviously need to start it before you can refresh your
1332 If you are still running the development server with C<DBIC_TRACE>
1333 enabled, you should also now see five more C<SELECT> statements in the
1334 debug output (one for each book as the authors are being retrieved by
1337 SELECT me.id, me.title, me.rating FROM book me:
1338 SELECT author.id, author.first_name, author.last_name FROM book_author me
1339 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '1'
1340 SELECT author.id, author.first_name, author.last_name FROM book_author me
1341 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '2'
1342 SELECT author.id, author.first_name, author.last_name FROM book_author me
1343 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '3'
1344 SELECT author.id, author.first_name, author.last_name FROM book_author me
1345 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '4'
1346 SELECT author.id, author.first_name, author.last_name FROM book_author me
1347 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '5'
1349 Also note in C<root/src/books/list.tt2> that we are using "| html", a
1350 type of TT filter, to escape characters such as E<lt> and E<gt> to <
1351 and > and avoid various types of dangerous hacks against your
1352 application. In a real application, you would probably want to put
1353 "| html" at the end of every field where a user has control over the
1354 information that can appear in that field (and can therefore inject
1355 markup or code if you don't "neutralize" those fields). In addition to
1356 "| html", Template Toolkit has a variety of other useful filters that
1357 can found in the documentation for
1358 L<Template::Filters|Template::Filters>.
1361 =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE
1363 In some situations, it can be useful to run your application and
1364 display a page without using a browser. Catalyst lets you do this
1365 using the C<scripts/myapp_test.pl> script. Just supply the URL you
1366 wish to display and it will run that request through the normal
1367 controller dispatch logic and use the appropriate view to render the
1368 output (obviously, complex pages may dump a lot of text to your
1369 terminal window). For example, if you type:
1371 $ script/myapp_test.pl "/books/list"
1373 You should get the same text as if you visited
1374 L<http://localhost:3000/books/list> with the normal development server
1375 and asked your browser to view the page source.
1378 =head1 OPTIONAL INFORMATION
1380 B<NOTE: The rest of this chapter of the tutorial is optional. You can
1381 skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
1385 =head2 Using 'RenderView' for the Default View
1387 Once your controller logic has processed the request from a user, it
1388 forwards processing to your view in order to generate the appropriate
1389 response output. Catalyst uses
1390 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1391 default to automatically perform this operation. If you look in
1392 C<lib/MyApp/Controller/Root.pm>, you should see the empty
1393 definition for the C<sub end> method:
1395 sub end : ActionClass('RenderView') {}
1397 The following bullet points provide a quick overview of the
1398 C<RenderView> process:
1404 C<Root.pm> is designed to hold application-wide logic.
1408 At the end of a given user request, Catalyst will call the most specific
1409 C<end> method that's appropriate. For example, if the controller for a
1410 request has an C<end> method defined, it will be called. However, if
1411 the controller does not define a controller-specific C<end> method, the
1412 "global" C<end> method in C<Root.pm> will be called.
1416 Because the definition includes an C<ActionClass> attribute, the
1417 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1418 will be executed B<after> any code inside the definition of C<sub end>
1419 is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1420 for more information on C<ActionClass>.
1424 Because C<sub end> is empty, this effectively just runs the default
1425 logic in C<RenderView>. However, you can easily extend the
1426 C<RenderView> logic by adding your own code inside the empty method body
1427 (C<{}>) created by the Catalyst Helpers when we first ran the
1428 C<catalyst.pl> to initialize our application. See
1429 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
1430 detailed information on how to extend C<RenderView> in C<sub end>.
1435 =head2 RenderView's "dump_info" Feature
1437 One of the nice features of C<RenderView> is that it automatically
1438 allows you to add C<dump_info=1> to the end of any URL for your
1439 application and it will force the display of the "exception dump"
1440 screen to the client browser. You can try this out by starting the
1441 development server as before and then point your browser to this URL:
1443 http://localhost:3000/books/list?dump_info=1
1445 You should get a page with the following message at the top:
1447 Caught exception in MyApp::Controller::Root->end "Forced debug -
1448 Scrubbed output at /usr/share/perl5/Catalyst/Action/RenderView.pm line 46."
1450 Along with a summary of your application's state at the end of the
1451 processing for that request. The "Stash" section should show a
1452 summarized version of the DBIC book model objects. If desired, you
1453 can adjust the summarization logic (called "scrubbing" logic) -- see
1454 L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for
1457 Note that you shouldn't need to worry about "normal clients" using
1458 this technique to "reverse engineer" your application -- C<RenderView>
1459 only supports the C<dump_info=1> feature when your application is
1460 running in C<-Debug> mode (something you won't do once you have your
1461 application deployed in production).
1464 =head2 Using The Default Template Name
1466 By default, C<Catalyst::View::TT> will look for a template that uses the
1467 same name as your controller action, allowing you to save the step of
1468 manually specifying the template name in each action. For example, this
1469 would allow us to remove the
1470 C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1471 C<list> action in the Books controller. Open
1472 C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1473 to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1478 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1483 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1484 # 'Context' that's used to 'glue together' the various components
1485 # that make up the application
1486 my ($self, $c) = @_;
1488 # Retrieve all of the book records as book model objects and store in the
1489 # stash where they can be accessed by the TT template
1490 $c->stash->{books} = [$c->model('DB::Book')->all];
1492 # Set the TT template to use. You will almost always want to do this
1493 # in your action methods (actions methods respond to user input in
1494 # your controllers).
1495 #$c->stash->{template} = 'books/list.tt2';
1499 You should now be able to restart the development server as per the
1500 previous section and access the L<http://localhost:3000/books/list>
1503 B<NOTE:> Please note that if you use the default template technique,
1504 you will B<not> be able to use either the C<$c-E<gt>forward> or
1505 the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1506 Chapter 9 of the Tutorial).
1508 B<IMPORTANT:> Make sure that you do NOT skip the following section
1509 before continuing to the next chapter 4 Basic CRUD.
1512 =head2 Return To A Manually Specified Template
1514 In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1515 later in the tutorial, you should remove the comment from the
1516 statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1518 $c->stash->{template} = 'books/list.tt2';
1520 Then delete the C<TEMPLATE_EXTENSION> line in
1521 C<lib/MyApp/View/TT.pm>.
1523 You should then be able to restart the development server and
1524 access L<http://localhost:3000/books/list> in the same manner as
1525 with earlier sections.
1530 Kennedy Clark, C<hkclark@gmail.com>
1532 Please report any errors, issues or suggestions to the author. The
1533 most recent version of the Catalyst Tutorial can be found at
1534 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
1536 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1537 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).