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[catagits/Catalyst-Manual.git] / lib / Catalyst / Manual / Tutorial / MoreCatalystBasics.pod
3533daff 1=head1 NAME
3Catalyst::Manual::Tutorial::MoreCatalystBasics - Catalyst Tutorial - Part 3: More Catalyst Application Development Basics
6=head1 OVERVIEW
8This is B<Part 3 of 10> for the Catalyst tutorial.
10L<Tutorial Overview|Catalyst::Manual::Tutorial>
12=over 4
14=item 1
18=item 2
20L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics>
22=item 3
24B<More Catalyst Basics>
26=item 4
28L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>
30=item 5
34=item 6
38=item 7
42=item 8
46=item 9
48L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
50=item 10
1390ef0e 59This part of the tutorial builds on the work done in Part 2 to explore
60some features that are more typical of "real world" web applications.
61From this part of the tutorial onward, we will be building a simple
62book database application. Although the application will be too
63limited to be of use to anyone, it should provide a basic environment
64where we can explore a variety of features used in virtually all web
3533daff 65applications.
67You can checkout the source code for this example from the catalyst
68subversion repository as per the instructions in
1390ef0e 69L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>.
3533daff 70
1390ef0e 74The remainder of the tutorial will build an application called C<MyApp>.
75First use the Catalyst C<catalyst.pl> script to initialize the framework
76for the C<MyApp> application (make sure you aren't still inside the
77directory of the C<Hello> application from the previous part of the
3533daff 78tutorial):
80 $ catalyst.pl MyApp
81 created "MyApp"
82 created "MyApp/script"
83 created "MyApp/lib"
84 created "MyApp/root"
85 ...
86 created "MyApp/script/myapp_create.pl"
87 $ cd MyApp
1390ef0e 89This creates a similar skeletal structure to what we saw in Part 2 of
90the tutorial, except with C<MyApp> and C<myapp> substituted for
3533daff 91C<Hello> and C<hello>.
96One of the greatest benefits of Catalyst is that it has such a large
1390ef0e 97library of plugins and base classes available. Plugins are used to
98seamlessly integrate existing Perl modules into the overall Catalyst
99framework. In general, they do this by adding additional methods to the
100C<context> object (generally written as C<$c>) that Catalyst passes to
101every component throughout the framework.
3533daff 102
103By default, Catalyst enables three plugins/flags:
105=over 4
1390ef0e 107=item *
3533daff 108
109C<-Debug> Flag
111Enables the Catalyst debug output you saw when we started the
112C<script/myapp_server.pl> development server earlier. You can remove
79a529cc 113this item when you place your application into production.
3533daff 114
1390ef0e 115As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
116Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
117line of your application class will be plugins, Catalyst supports a
118limited number of flag options (of these, C<-Debug> is the most
119common). See the documentation for C<Catalyst.pm> to get details on
120other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
3533daff 121
122If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
125B<TIP>: Depending on your needs, it can be helpful to permanently
126remove C<-Debug> from C<lib/MyApp.pm> and then use the C<-d> option
127to C<script/myapp_server.pl> to re-enable it just for the development
1390ef0e 128server. We will not be using that approach in the tutorial, but feel
3533daff 129free to make use of it in your own projects.
131=item *
135C<ConfigLoader> provides an automatic way to load configurable
c010ae0d 136parameters for your application from a central
137L<Config::General|Config::General> file (versus having the values
138hard-coded inside your Perl modules). Config::General uses syntax
139very similar to Apache configuration files. We will see how to use
140this feature of Catalyst during the authentication and authorization
141sections (Part 5 and Part 6).
3533daff 142
1390ef0e 143B<IMPORTANT NOTE:> If you are using a version of
144L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, you need to
145be aware that Catalyst changed from a default format of YAML to the
146more straightforward C<Config::General> format. This tutorial use the
147newer C<myapp.conf> configuration file for C<Config::General> instead
148of C<myapp.yml> for YAML. However, Catalyst has long supported both
149formats and Catalyst will automatically use either C<myapp.conf> or
150C<myapp.yml> (or any other format supported by
056394af 151L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
1390ef0e 152L<Config::Any|Config::Any>). If you are using a versions of
153Catalyst::Devel prior to 1.06, you can convert to the newer format by
8a0214b4 154simply creating the C<myapp.conf> file manually and deleting
1390ef0e 155C<myapp.yml>. The default contents of C<myapp.conf> should only
156consist of one line: C<name MyApp>.
15e1d0b2 157
1390ef0e 158B<TIP>: This script can be useful for converting between configuration
15e1d0b2 159formats:
1390ef0e 161 perl -Ilib -e 'use MyApp; use Config::General;
15e1d0b2 162 Config::General->new->save_file("myapp.conf", MyApp->config);'
d0496197 164B<NOTE:> The default C<myapp.conf> should look like:
166 name MyApp
15e1d0b2 167
3533daff 168=item *
172C<Static::Simple> provides an easy method of serving static content such
173as images and CSS files under the development server.
94d8da41 177For our application, we want to add one new plugin into the mix. To
1390ef0e 178do this, edit C<lib/MyApp.pm> (this file is generally referred to as
179your I<application class>) and delete the line with:
3533daff 180
1390ef0e 181 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
3533daff 182
1390ef0e 183Then replace it with:
b411df01 184
1390ef0e 185 __PACKAGE__->setup(qw/
186 -Debug
187 ConfigLoader
188 Static::Simple
190 StackTrace
191 /);
94d8da41 193B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
194techniques to load these plugins/flags. If you are following along in
195Ubuntu 8.10, you should have C<Catalyst::Devel> v1.07 and see the
196default code shown above. If you are using v1.08, you should see the
197following by default:
199 use Catalyst qw/-Debug
200 ConfigLoader
201 Static::Simple/;
202 ...
203 __PACKAGE__->setup();
205Don't let these variations confuse you -- they all accomplish the same
1390ef0e 208This tells Catalyst to start using one new plugin,
209L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
210stack trace to the standard Catalyst "debug screen" (the screen
211Catalyst sends to your browser when an error occurs). Be aware that
212L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
213browser, not in the console window from which you're running your
214application, which is where logging output usually goes.
3533daff 215
1390ef0e 216B<Notes:>
3533daff 217
218=over 4
1390ef0e 220=item *
222C<__PACKAGE__> is just a shorthand way of referencing the name of the
223package where it is used. Therefore, in C<MyApp.pm>, C<__PACKAGE__>
224is equivalent to C<MyApp>.
3533daff 225
1390ef0e 226=item *
3533daff 227
1390ef0e 228You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
229before you put your application into production, but it can be helpful
230during development.
3533daff 231
1390ef0e 232=item *
3533daff 233
1390ef0e 234When specifying plugins on the C<__PACKAGE__-E<gt>setup> line, you can
235omit C<Catalyst::Plugin::> from the name. Additionally, you can
236spread the plugin names across multiple lines as shown here, or place
237them all on one (or more) lines as with the default configuration.
cca5cd98 238
3533daff 239=back
3533daff 241
1390ef0e 244As discussed earlier, controllers are where you write methods that
245interact with user input. Typically, controller methods respond to
3533daff 246C<GET> and C<POST> messages from the user's web browser.
248Use 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"
1390ef0e 257Then edit C<lib/MyApp/Controller/Books.pm> (as discussed in Part 2 of
258the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
259each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
260and add the following method to the controller:
3533daff 261
262 =head2 list
264 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
266 =cut
1390ef0e 267
3533daff 268 sub list : Local {
269 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
270 # 'Context' that's used to 'glue together' the various components
271 # that make up the application
272 my ($self, $c) = @_;
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
1390ef0e 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} = '';
3533daff 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
282 # your controllers).
283 $c->stash->{template} = 'books/list.tt2';
284 }
1390ef0e 286B<TIP>: See Appendix 1 for tips on removing the leading spaces when
287cutting and pasting example code from POD-based documents.
3533daff 288
1390ef0e 289Programmers experienced with object-oriented Perl should recognize
290C<$self> as a reference to the object where this method was called.
291On the other hand, C<$c> will be new to many Perl programmers who have
292not used Catalyst before (it's sometimes written as C<$context>). The
293Context object is automatically passed to all Catalyst components. It
294is used to pass information between components and provide access to
295Catalyst and plugin functionality.
3533daff 296
297B<Note:> Catalyst actions are regular Perl methods, but they make use
1390ef0e 298of Nicholas Clark's C<attributes> module (that's the "C<: Local>" next
3533daff 299to the C<sub list> in the code above) to provide additional
300information to the Catalyst dispatcher logic. Many newer Catalyst
ae492862 301applications are switching to the use of "Literal" C<:Path> actions
3533daff 302and C<Args> attribute in lieu of C<: Local> and C<: Private>. For
1390ef0e 303example, C<sub any_method :Path :Args(0)> can be used instead of C<sub
304index :Private> (because no path was supplied to C<Path> it matches
305the "empty" URL in the namespace of that module... the same thing
306C<sub index> would do) or C<sub list :Path('list') :Args(0)> could be
307used instead of the C<sub list : Local> above (the C<list> argument to
308C<Path> would make it match on the URL C<list> under C<books>, the
309namespace of the current module). See "Action Types" in
3533daff 310L<Catalyst::Manual::Intro|Catalyst::Manual::Intro> as well as Part 5
311of this tutorial (Authentication) for additional information. Another
312popular but more advanced feature is C<Chained> actions that allow a
313single URL to "chain together" multiple action method calls, each with
1390ef0e 314an appropriate number of arguments (see
315L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained> for
3533daff 317
321As mentioned in Part 2 of the tutorial, views are where you render
1390ef0e 322output, typically for display in the user's web browser (but also
323possibly using other display output-generation systems). The code in
324C<lib/MyApp/View> selects the I<type> of view to use, with the actual
325rendering template found in the C<root> directory. As with virtually
326every aspect of Catalyst, options abound when it comes to the specific
327view technology you adopt inside your application. However, most
328Catalyst applications use the Template Toolkit, known as TT (for more
329information on TT, see L<http://www.template-toolkit.org>). Other
330somewhat popular view technologies include Mason
331(L<http://www.masonhq.com> and L<http://www.masonbook.com>) and
332L<HTML::Template> (L<http://html-template.sourceforge.net>).
335=head2 Create a Catalyst View
3533daff 336
337When using TT for the Catalyst view, there are two main helper scripts:
339=over 4
341=item *
345=item *
de966eb4 351Both helpers are similar. C<TT> creates the C<lib/MyApp/View/TT.pm>
3533daff 352file and leaves the creation of any hierarchical template organization
353entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
de966eb4 354test cases will be discussed in Part 8.) C<TTSite>, on the other hand,
355creates a modular and hierarchical view layout with
1390ef0e 356separate Template Toolkit (TT) files for common header and footer
357information, configuration values, a CSS stylesheet, and more.
de966eb4 359While C<TTSite> was useful to bootstrap a project, its use is now
360deprecated and to be considered historical. For most Catalyst
361applications it adds redundant functionality and structure; many in the
362Catalyst community recommend that it's easier to learn both Catalyst and
363Template Toolkit if you use the more basic C<TT> approach.
364Consequently, this tutorial will use "plain old TT."
1390ef0e 365
366Enter the following command to enable the C<TT> style of view
3533daff 367rendering for this tutorial:
1390ef0e 369 $ script/myapp_create.pl view TT TT
3533daff 370 exists "/home/me/MyApp/script/../lib/MyApp/View"
371 exists "/home/me/MyApp/script/../t"
1390ef0e 372 created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm"
373 created "/home/me/MyApp/script/../t/view_TT.t"
3533daff 374
1390ef0e 375This simply creates a view called C<TT> (the second 'TT' argument) in
376a file called C<TT.pm> (the first 'TT' argument). It is now up to you
377to decide how you want to structure your view layout. For the
378tutorial, we will start with a very simple TT template to initially
379demonstrate the concepts, but quickly migrate to a more typical
380"wrapper page" type of configuration (where the "wrapper" controls the
381overall "look and feel" of your site from a single file or set of
3533daff 383
1390ef0e 384Edit C<lib/MyApp/View/TT.pm> and you should see that the default
385contents contains something similar to the following:
3533daff 386
1390ef0e 387 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
3533daff 388
1390ef0e 389And update it to match:
391 __PACKAGE__->config(
392 # Change default TT extension
394 # Set the location for TT files
6abd3023 396 MyApp->path_to( 'root', 'src' ),
1390ef0e 397 ],
398 );
3533daff 399
1390ef0e 400B<NOTE:> Make sure to add a comma after '.tt2' outside the single
191dee29 403This changes the default extension for Template Toolkit from '.tt' to
1390ef0e 404'.tt2' and changes the base directory for your template files from
de966eb4 405C<root> to C<root/src>. These changes from the default are done mostly
406to facilitate the application we're developing in this tutorial; as with
407most things Perl, there's more than one way to do it...
1390ef0e 408
410=head2 Create a TT Template Page
3533daff 411
412First create a directory for book-related TT templates:
1390ef0e 414 $ mkdir -p root/src/books
3533daff 415
416Then 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. -%]
1390ef0e 423 [% # Provide a title -%]
3533daff 424 [% META title = 'Book List' -%]
426 <table>
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 -%]
430 <tr>
431 <td>[% book.title %]</td>
432 <td>[% book.rating %]</td>
433 </tr>
434 [% END -%]
435 </table>
437As indicated by the inline comments above, the C<META title> line uses
1390ef0e 438TT's META feature to provide a title to the "wrapper" that we will
439create later. Meanwhile, the C<FOREACH> loop iterates through each
440C<book> model object and prints the C<title> and C<rating> fields.
3533daff 441
442If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT
443code. TT supports a wide variety of directives for "calling" other
444files, looping, conditional logic, etc. In general, TT simplifies the
445usual range of Perl operators down to the single dot (C<.>) operator.
446This applies to operations as diverse as method calls, hash lookups, and
447list index values (see
55beb65d 448L<http://search.cpan.org/perldoc?Template::Manual::Variables>
3533daff 449for details and examples). In addition to the usual C<Template> module
450Pod documentation, you can access the TT manual at
55beb65d 451L<http://search.cpan.org/perldoc?Template::Manual>.
3533daff 452
1390ef0e 453B<TIP:> While you can build all sorts of complex logic into your TT
454templates, you should in general keep the "code" part of your templates
455as simple as possible. If you need more complex logic, create helper
456methods in your model that abstract out a set of code into a single call
457from your TT template. (Note that the same is true of your controller
458logic as well -- complex sections of code in your controllers should
459often be pulled out and placed into your model objects.)
462=head2 Test Run The Application
464To test your work so far, first start the development server:
466 $ script/myapp_server.pl
468Then point your browser to L<http://localhost:3000> and you should
469still get the Catalyst welcome page. Next, change the URL in your
470browser to L<http://localhost:3000/books/list>. If you have
471everything working so far, you should see a web page that displays
472nothing other than our column headers for "Title", "Rating", and
473"Author(s)" -- we will not see any books until we get the database and
474model working below.
476If you run into problems getting your application to run correctly, it
477might be helpful to refer to some of the debugging techniques covered in
478the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the
3533daff 480
484In this step, we make a text file with the required SQL commands to
1390ef0e 485create a database table and load some sample data. We will use SQLite,
486a popular database that is lightweight and easy to use. Open
487C<myapp01.sql> in your editor and enter:
3533daff 488
489 --
490 -- Create a very simple database to hold book and author information
491 --
492 CREATE TABLE books (
494 title TEXT ,
495 rating INTEGER
496 );
497 -- 'book_authors' is a many-to-many join table between books & authors
498 CREATE TABLE book_authors (
499 book_id INTEGER,
500 author_id INTEGER,
501 PRIMARY KEY (book_id, author_id)
502 );
503 CREATE TABLE authors (
505 first_name TEXT,
506 last_name TEXT
507 );
508 ---
509 --- Load some sample data
510 ---
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);
3533daff 533Then use the following command to build a C<myapp.db> SQLite database:
535 $ sqlite3 myapp.db < myapp01.sql
537If you need to create the database more than once, you probably want to
538issue the C<rm myapp.db> command to delete the database before you use
1390ef0e 539the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
3533daff 540
541Once the C<myapp.db> database file has been created and initialized, you
542can use the SQLite command line environment to do a quick dump of the
543database contents:
545 $ sqlite3 myapp.db
546 SQLite version 3.4.2
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
552 4|Perl Cookbook|5
553 5|Designing with Web Standards|5
554 sqlite> .q
555 $
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
563 4|Perl Cookbook|5
564 5|Designing with Web Standards|5
566As with most other SQL tools, if you are using the full "interactive"
567environment you need to terminate your SQL commands with a ";" (it's not
568required 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
570your OS command prompt.
a6d800ac 572For using other databases, such as PostgreSQL or MySQL, see
573L<Appendix 2|Catalyst::Manual::Tutorial::Appendices>.
3533daff 574
191dee29 577Catalyst can be used with virtually any form of persistent datastore
578available via Perl. For example,
579L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to easily
580access databases through the traditional Perl C<DBI> interface. However,
581most Catalyst applications use some form of ORM technology to
582automatically create and save model objects as they are used. Although
583L<Class::DBI|Class::DBI> has been a popular choice in the past, Matt
584Trout's L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly
585emerged as the Perl-based ORM technology of choice. Most new Catalyst
586applications rely on DBIC, as will this tutorial.
3533daff 587
3533daff 588
1390ef0e 589=head2 Create a Dynamic DBIC Model
591Use the C<create=dynamic> model helper option to build a model that
3533daff 592dynamically reads your database structure every time the application
d0496197 595 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=dynamic dbi:SQLite:myapp.db
1390ef0e 596 exists "/home/me/MyApp/script/../lib/MyApp/Model"
597 exists "/home/me/MyApp/script/../t"
598 exists "/home/me/MyApp/script/../lib/MyApp"
599 created "/home/me/MyApp/script/../lib/MyApp/Schema.pm"
600 created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm"
601 created "/home/me/MyApp/script/../t/model_DB.t"
3533daff 602
d0496197 604C<DB> is the name of the model class to be created by the helper in
1390ef0e 605C<lib/MyApp/Model>. C<DBIC::Schema> is the type of the model to
606create. C<MyApp::Schema> is the name of the DBIC schema file written
607to C<lib/MyApp/Schema.pm>. Because we specified C<create=dynamic> to
608the helper, it use
609L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
610dynamically load the schema information from the database every time
c93b5eaa 611the application starts. DBIC uses the schema to load other classes
612that represent the tables in your database (DBIC refers to these
613"table objects" as "result sources," see
614L<DBIx::Class::ResultSource|DBIx::Class::ResultSource>). And finally,
615C<dbi:SQLite:myapp.db> is the standard DBI connect string for use with
3533daff 617
d0496197 618B<NOTE:> Although the C<create=dynamic> option to the DBIC helper
19c49089 619makes for a nifty demonstration, is only really suitable for very
620small applications. After this demonstration, you should almost always
621use the C<create=static> option that we switch to below.
dc9a0503 622
191dee29 626Open C<lib/MyApp/Controller/Books.pm> and un-comment the model code we
627left disabled earlier (un-comment the line containing
1390ef0e 628C<[$c-E<gt>model('DB::Books')-E<gt>all]> and delete the next 2 lines):
630 =head2 list
632 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
634 =cut
636 sub list : Local {
637 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
638 # 'Context' that's used to 'glue together' the various components
639 # that make up the application
640 my ($self, $c) = @_;
642 # Retrieve all of the book records as book model objects and store in the
643 # stash where they can be accessed by the TT template
644 $c->stash->{books} = [$c->model('DB::Books')->all];
646 # Set the TT template to use. You will almost always want to do this
647 # in your action methods (action methods respond to user input in
648 # your controllers).
649 $c->stash->{template} = 'books/list.tt2';
650 }
c93b5eaa 652B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
653above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
654two are equivalent. Either way, C<$c-E<gt>model> returns a
655L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
656against the database and iterating over the set of results that are
659We are using the C<-E<gt>all> to fetch all of the books. DBIC
660supports a wide variety of more advanced operations to easily do
661things like filtering and sorting the results. For example, the
518f3851 662following could be used to sort the results by descending title:
c93b5eaa 663
664 $c->model('DB::Books')->search({}, {order_by => 'title DESC'});
666Some other examples are provided in
667L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
668additional information found at L<DBIx::Class::ResultSet/search>,
671and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
1390ef0e 672
674=head2 Test Run The Application
3533daff 675
676First, let's enable an environment variable option that causes
677DBIx::Class to dump the SQL statements it's using to access the database
678(this option can provide extremely helpful troubleshooting information):
680 $ export DBIC_TRACE=1
682This assumes you are using BASH as your shell -- adjust accordingly if
683you are using a different shell (for example, under tcsh, use
684C<setenv DBIC_TRACE 1>).
d0496197 686B<NOTE:> You can also set this in your code using
3533daff 687C<$class-E<gt>storage-E<gt>debug(1);>. See
688L<DBIx::Class::Manual::Troubleshooting> for details (including options
689to log to file instead of displaying to the Catalyst development server
1390ef0e 692Then launch the Catalyst development server. The log output should
693display something like:
3533daff 694
695 $script/myapp_server.pl
696 [debug] Debug messages enabled
1390ef0e 697 [debug] Statistics enabled
3533daff 698 [debug] Loaded plugins:
699 .----------------------------------------------------------------------------.
1390ef0e 700 | Catalyst::Plugin::ConfigLoader 0.20 |
701 | Catalyst::Plugin::StackTrace 0.08 |
3533daff 702 | Catalyst::Plugin::Static::Simple 0.20 |
703 '----------------------------------------------------------------------------'
705 [debug] Loaded dispatcher "Catalyst::Dispatcher"
706 [debug] Loaded engine "Catalyst::Engine::HTTP"
707 [debug] Found home "/home/me/MyApp"
45d511e0 708 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
3533daff 709 [debug] Loaded components:
710 .-----------------------------------------------------------------+----------.
711 | Class | Type |
712 +-----------------------------------------------------------------+----------+
713 | MyApp::Controller::Books | instance |
714 | MyApp::Controller::Root | instance |
d0496197 715 | MyApp::Model::DB | instance |
716 | MyApp::Model::DB::Authors | class |
717 | MyApp::Model::DB::BookAuthors | class |
718 | MyApp::Model::DB::Books | class |
3533daff 719 | MyApp::View::TT | instance |
720 '-----------------------------------------------------------------+----------'
722 [debug] Loaded Private actions:
723 .----------------------+--------------------------------------+--------------.
724 | Private | Class | Method |
725 +----------------------+--------------------------------------+--------------+
726 | /default | MyApp::Controller::Root | default |
727 | /end | MyApp::Controller::Root | end |
1390ef0e 728 | /index | MyApp::Controller::Root | index |
3533daff 729 | /books/index | MyApp::Controller::Books | index |
730 | /books/list | MyApp::Controller::Books | list |
731 '----------------------+--------------------------------------+--------------'
733 [debug] Loaded Path actions:
734 .-------------------------------------+--------------------------------------.
735 | Path | Private |
736 +-------------------------------------+--------------------------------------+
1390ef0e 737 | / | /default |
738 | / | /index |
739 | /books | /books/index |
3533daff 740 | /books/list | /books/list |
741 '-------------------------------------+--------------------------------------'
1390ef0e 743 [info] MyApp powered by Catalyst 5.7014
3533daff 744 You can connect to your server at http://localhost:3000
1390ef0e 746B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from
747the 'base' directory of your application, not inside the C<script>
748directory itself or it will not be able to locate the C<myapp.db>
749database file. You can use a fully qualified or a relative path to
750locate the database file, but we did not specify that when we ran the
3533daff 751model helper earlier.
753Some things you should note in the output above:
755=over 4
1390ef0e 757=item *
3533daff 758
1390ef0e 759Catalyst::Model::DBIC::Schema dynamically created three model classes,
760one to represent each of the three tables in our database
d0496197 761(C<MyApp::Model::DB::Authors>, C<MyApp::Model::DB::BookAuthors>,
762and C<MyApp::Model::DB::Books>).
3533daff 763
1390ef0e 764=item *
3533daff 765
766The "list" action in our Books controller showed up with a path of
771Point your browser to L<http://localhost:3000> and you should still get
772the Catalyst welcome page.
774Next, to view the book list, change the URL in your browser to
775L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 776books loaded by the C<myapp01.sql> script above without any formatting.
777The rating for each book should appear on each row, but the "Author(s)"
191dee29 778column will still be blank (we will fill that in later).
3533daff 779
780Also notice in the output of the C<script/myapp_server.pl> that DBIC
781used the following SQL to retrieve the data:
783 SELECT me.id, me.title, me.rating FROM books me
785because we enabled DBIC_TRACE.
0c51850e 787You now have the beginnings of a simple but workable web application.
3533daff 788Continue on to future sections and we will develop the application
789more fully.
1390ef0e 792=head1 CREATE A WRAPPER FOR THE VIEW
794When using TT, you can (and should!) create a wrapper that will
795literally wrap content around each of your templates. This is
796certainly useful as you have one main source for changing things that
797will appear across your entire site/application instead of having to
798edit many individual files.
801=head2 Configure TT.pm For The Wrapper
803In order to create a wrapper, you must first edit your TT view and
804tell it where to find your wrapper file. Your TT view is located in
807Edit C<lib/MyApp/View/TT.pm> and change it to match the following:
809 __PACKAGE__->config(
810 # Change default TT extension
812 # Set the location for TT files
c2dfb562 814 MyApp->path_to( 'root', 'src' ),
1390ef0e 815 ],
816 # Set to 1 for detailed timer stats in your HTML as comments
817 TIMER => 0,
818 # This is your wrapper template located in the 'root/src'
819 WRAPPER => 'wrapper.tt2',
820 );
823=head2 Create the Wrapper Template File and Stylesheet
825Next you need to set up your wrapper template. Basically, you'll want
826to take the overall layout of your site and put it into this file.
827For the tutorial, open C<root/src/wrapper.tt2> and input the following:
829 <?xml version="1.0" encoding="UTF-8"?>
830 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
831 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
832 <head>
833 <title>[% template.title or "My Catalyst App!" %]</title>
834 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
835 </head>
837 <body>
838 <div id="outer">
839 <div id="header">
840 [%# Your logo could go here -%]
841 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
842 [%# Insert the page title -%]
843 <h1>[% template.title or site.title %]</h1>
844 </div>
846 <div id="bodyblock">
847 <div id="menu">
848 Navigation:
849 <ul>
850 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
851 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
852 <li><a href="mailto:nobody@nowhere.com" title="Contact Us">Contact Us</a></li>
853 </ul>
854 </div><!-- end menu -->
856 <div id="content">
857 [%# Status and error messages %]
858 <span class="message">[% status_msg %]</span>
859 <span class="error">[% error_msg %]</span>
860 [%# This is where TT will stick all of your template's contents. -%]
861 [% content %]
862 </div><!-- end content -->
863 </div><!-- end bodyblock -->
865 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 866 </div><!-- end outer -->
1390ef0e 867
868 </body>
869 </html>
871Notice the status and error message sections in the code above:
873 <span class="status">[% status_msg %]</span>
874 <span class="error">[% error_msg %]</span>
876If we set either message in the Catalyst stash (e.g.,
877C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
878will be displayed whenever any view used by that request is rendered.
879The C<message> and C<error> CSS styles can be customized to suit your
880needs in the C<root/static/css/main.css> file we create below.
884=over 4
886=item *
888The Catalyst stash only lasts for a single HTTP request. If
889you need to retain information across requests you can use
890L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
891Catalyst sessions in the Authentication part of the tutorial).
893=item *
895Although it is beyond the scope of this tutorial, you may wish to use
896a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or
897Dojo (L<http://www.dojotoolkit.org>).
902=head3 Create A Basic Stylesheet
904First create a central location for stylesheets under the static
907 $ mkdir root/static/css
909Then open the file C<root/static/css/main.css> (the file referenced in
910the stylesheet href link of our wrapper above) and add the following
913 #header {
914 text-align: center;
915 }
916 #header h1 {
917 margin: 0;
918 }
919 #header img {
920 float: right;
921 }
922 #footer {
923 text-align: center;
924 font-style: italic;
925 padding-top: 20px;
926 }
927 #menu {
928 font-weight: bold;
929 background-color: #ddd;
930 }
931 #menu ul {
932 list-style: none;
933 float: left;
934 margin: 0;
935 padding: 0 0 50% 5px;
936 font-weight: normal;
937 background-color: #ddd;
938 width: 100px;
939 }
940 #content {
941 margin-left: 120px;
942 }
943 .message {
944 color: #390;
945 }
946 .error {
947 color: #f00;
948 }
950You may wish to check out a "CSS Framework" like Emastic
951(L<http://code.google.com/p/emastic/>) as a way to quickly
952provide lots of high-quality CSS functionality.
955=head2 Test Run The Application
957Restart the development server and hit "Reload" in your web browser
958and you should now see a formatted version of our basic book list.
959Although our wrapper and stylesheet are obviously very simple, you
960should see how it allows us to control the overall look of an entire
961website from two central files. To add new pages to the site, just
962provide a template that fills in the C<content> section of our wrapper
963template -- the wrapper will provide the overall feel of the page.
3533daff 966=head1 A STATIC DATABASE MODEL WITH C<DBIx::Class>
968=head2 Create Static DBIC Schema Files
1390ef0e 970Unlike the previous DBIC section where we had C<create=dynamic>
971automatically discover the structure of the database every time the
972application started, here we will use static schema files for more
973control. This is typical of most "real world" applications.
3533daff 974
1390ef0e 975One option would be to manually create a separate schema file for each
976table in the database, however, lets use the same
977L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> used
978earlier with C<create=dynamic> to build the static files for us.
9ad715b3 979First, lets remove the schema file created earlier:
3533daff 980
1390ef0e 981 $ rm lib/MyApp/Schema.pm
3533daff 982
983Now regenerate the schema using the C<create=static> option:
d0496197 985 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=static dbi:SQLite:myapp.db
986 exists "/home/kclark/dev/MyApp/script/../lib/MyApp/Model"
987 exists "/home/kclark/dev/MyApp/script/../t"
988 Dumping manual schema for MyApp::Schema to directory /home/kclark/dev/MyApp/script/../lib ...
3533daff 989 Schema dump completed.
d0496197 990 exists "/home/kclark/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
3533daff 991
1390ef0e 992We could have also deleted C<lib/MyApp/Model/DB.pm>, but it would
3533daff 993have regenerated the same file (note the C<exists> in the output above).
d0496197 994If you take a look at C<lib/MyApp/Model/DB.pm>, it simply contains
995a reference to the actual schema file in C<lib/MyApp/Schema.pm>
3533daff 996along with the database connect string.
1390ef0e 998If you look in the C<lib/MyApp/Schema.pm> file, you will find that it
999is no longer using
1000L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> as its base
1001class (L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> is
1002only being used by the helper to load the schema once and then create
1003the static files for us) and C<Schema.pm> only contains a call to the
c2dfb562 1004C<load_classes> method. You will also find that C<lib/MyApp>
1390ef0e 1005contains a C<Schema> subdirectory, with one file inside this directory
1006for each of the tables in our simple database (C<Authors.pm>,
1007C<BookAuthors.pm>, and C<Books.pm>). These three files were created
1008based on the information found by
1009L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> as the
1010helper ran.
1012The idea with all of the files created under C<lib/MyApp/Schema> by
1013the C<create=static> option is to only edit the files below the C<# DO
1014NOT MODIFY THIS OR ANYTHING ABOVE!> warning. If you place all of your
3533daff 1015changes below that point in the file, you can regenerate the
1390ef0e 1016automatically created information at the top of each file should your
1017database structure get updated.
3533daff 1018
1390ef0e 1019Also note the "flow" of the model information across the various files
1020and directories. Catalyst will initially load the model from
d0496197 1021C<lib/MyApp/Model/DB.pm>. This file contains a reference to
1022C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally,
1390ef0e 1023the call to C<load_classes> in C<Schema.pm> will load each of the
d0496197 1024table-specific "results source" files from the C<lib/MyApp/Schema>
1390ef0e 1025subdirectory. These three table-specific DBIC schema files will then be
1026used to create three table-specific Catalyst models every time the
3533daff 1027application starts (you can see these three model files listed in
1028the debug output generated when you launch the application).
1031=head2 Updating the Generated DBIC Schema Files
3533daff 1033Let's manually add some relationship information to the auto-generated
d0496197 1034schema files. First edit C<lib/MyApp/Schema/Books.pm> and
1390ef0e 1035add the following text below the C<# You can replace this text...>
3533daff 1036comment:
1038 #
1039 # Set relationships:
1390ef0e 1040 #
3533daff 1041
1042 # has_many():
1043 # args:
1044 # 1) Name of relationship, DBIC will create accessor with this name
1045 # 2) Name of the model class referenced by this relationship
1046 # 3) Column name in *foreign* table
d0496197 1047 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::BookAuthors', 'book_id');
3533daff 1048
1049 # many_to_many():
1050 # args:
1051 # 1) Name of relationship, DBIC will create accessor with this name
1390ef0e 1052 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1053 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1054 # You must already have the has_many() defined to use a many_to_many().
1055 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1058B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1059file. As with any Perl package, we need to end the last line with
1060a statement that evaluates to C<true>. This is customarily done with
1061C<1;> on a line by itself.
1390ef0e 1063This code defines both a C<has_many> and a C<many_to_many> relationship.
1064The C<many_to_many> relationship is optional, but it makes it easier to
1065map a book to its collection of authors. Without it, we would have to
1066"walk" though the C<book_authors> table as in
1068(we will see examples on how to use DBIC objects in your code soon,
1069but note that because C<$book-E<gt>book_authors> can return multiple
1070authors, we have to use C<first> to display a single author).
1071C<many_to_many> allows us to use the shorter
1073Note that you cannot define a C<many_to_many> relationship without
1074also having the C<has_many> relationship in place.
3533daff 1075
d0496197 1076Then edit C<lib/MyApp/Schema/Authors.pm> and add relationship
3533daff 1077information as follows (again, be careful to put in above the C<1;> but
1078below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1080 #
1081 # Set relationships:
1082 #
1084 # has_many():
1085 # args:
1086 # 1) Name of relationship, DBIC will create accessor with this name
1087 # 2) Name of the model class referenced by this relationship
1088 # 3) Column name in *foreign* table
d0496197 1089 __PACKAGE__->has_many(book_author => 'MyApp::Schema::BookAuthors', 'author_id');
3533daff 1090
1091 # many_to_many():
1092 # args:
1093 # 1) Name of relationship, DBIC will create accessor with this name
1094 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1095 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1096 # You must already have the has_many() defined to use a many_to_many().
1097 __PACKAGE__->many_to_many(books => 'book_author', 'book');
1390ef0e 1099Finally, do the same for the "join table,"
d0496197 1100C<lib/MyApp/Schema/BookAuthors.pm>:
3533daff 1101
1102 #
1103 # Set relationships:
1104 #
1106 # belongs_to():
1107 # args:
1108 # 1) Name of relationship, DBIC will create accessor with this name
1109 # 2) Name of the model class referenced by this relationship
1110 # 3) Column name in *this* table
d0496197 1111 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Books', 'book_id');
3533daff 1112
1113 # belongs_to():
1114 # args:
1115 # 1) Name of relationship, DBIC will create accessor with this name
1116 # 2) Name of the model class referenced by this relationship
1117 # 3) Column name in *this* table
d0496197 1118 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Authors', 'author_id');
3533daff 1119
1390ef0e 1121=head2 Run The Application
3533daff 1122
1123Run the Catalyst "demo server" script with the C<DBIC_TRACE> option
1124(it might still be enabled from earlier in the tutorial, but here
1125is an alternate way to specify the option just in case):
1127 $ DBIC_TRACE=1 script/myapp_server.pl
1390ef0e 1129Make sure that the application loads correctly and that you see the
1130three dynamically created model class (one for each of the
3533daff 1131table-specific schema classes we created).
c2dfb562 1133Then hit the URL L<http://localhost:3000/books/list> and be sure that
1134the book list is displayed via the relationships established above. You
1135can leave the development server running for the next step if you wish.
3533daff 1136
c2dfb562 1137B<Note:> You will not see the authors yet because the view does not yet
1138use the new relations. Read on to the next section where we update the
1139template to do that.
3533daff 1140
1144Let's add a new column to our book list page that takes advantage of
1145the relationship information we manually added to our schema files
1146in the previous section. Edit C<root/src/books/list.tt2> add add the
1147following code below the existing table cell that contains
1390ef0e 1148C<book.rating> (IOW, add a new table cell below the existing two
3533daff 1149C<td> cells):
1151 <td>
1152 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1153 [% # loop in 'side effect notation' to load just the last names of the -%]
a0c5188a 1154 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
3533daff 1155 [% # a value, so nothing will be printed here. But, if you have something -%]
1156 [% # in TT that does return a method and you don't want it printed, you -%]
1157 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1158 [% # call it and discard the return value. -%]
1159 [% tt_authors = [ ];
1160 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1161 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1162 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1163 ([% tt_authors.size | html %])
1164 [% # Use another TT vmethod to join & print the names & comma separators -%]
1165 [% tt_authors.join(', ') | html %]
1166 </td>
1390ef0e 1168Then hit "Reload" in your browser (note that you don't need to reload
3533daff 1169the development server or use the C<-r> option when updating TT
1390ef0e 1170templates) and you should now see the number of authors each book has
1171along with a comma-separated list of the authors' last names. (If you
1172didn't leave the development server running from the previous step,
1173you will obviously need to start it before you can refresh your
1174browser window.)
1176If you are still running the development server with C<DBIC_TRACE>
1177enabled, you should also now see five more C<SELECT> statements in the
1178debug output (one for each book as the authors are being retrieved by
3533daff 1179DBIC).
c2dfb562 1181 SELECT me.id, me.title, me.rating FROM books me:
1182 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '1'
1183 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '2'
1184 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '3'
1185 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '4'
1186 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '5'
1188Also note in C<root/src/books/list.tt2> that we are using "| html", a
1189type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1190and &gt; and avoid various types of dangerous hacks against your
1191application. In a real application, you would probably want to put
1192"| html" at the end of every field where a user has control over the
1193information that can appear in that field (and can therefore inject
1194markup or code if you don't "neutralize" those fields). In addition to
1195"| html", Template Toolkit has a variety of other useful filters that
1196can found in the documentation for
3533daff 1198
1202In some situations, it can be useful to run your application and
1203display a page without using a browser. Catalyst lets you do this
1204using the C<scripts/myapp_test.pl> script. Just supply the URL you
1205wish to display and it will run that request through the normal
1206controller dispatch logic and use the appropriate view to render the
1207output (obviously, complex pages may dump a lot of text to your
1208terminal window). For example, if you type:
1210 $ script/myapp_test.pl "/books/list"
1212You should get the same text as if you visited
1213L<http://localhost:3000/books/list> with the normal development server
1214and asked your browser to view the page source.
3533daff 1215
1390ef0e 1216
1219B<NOTE: The rest of this part of the tutorial is optional. You can
1220skip to Part 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
3533daff 1221if you wish.>
1390ef0e 1223=head2 Using C<RenderView> for the Default View
1225Once your controller logic has processed the request from a user, it
1226forwards processing to your view in order to generate the appropriate
3533daff 1227response output. Catalyst uses
1390ef0e 1228L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1229default to automatically performs this operation. If you look in
1230C<lib/MyApp/Controller/Root.pm>, you should see the empty
3533daff 1231definition for the C<sub end> method:
1233 sub end : ActionClass('RenderView') {}
1390ef0e 1235The following bullet points provide a quick overview of the
3533daff 1236C<RenderView> process:
1238=over 4
1240=item *
1242C<Root.pm> is designed to hold application-wide logic.
1244=item *
1390ef0e 1246At the end of a given user request, Catalyst will call the most specific
1247C<end> method that's appropriate. For example, if the controller for a
1248request has an C<end> method defined, it will be called. However, if
1249the controller does not define a controller-specific C<end> method, the
3533daff 1250"global" C<end> method in C<Root.pm> will be called.
1252=item *
1254Because the definition includes an C<ActionClass> attribute, the
1255L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1256will be executed B<after> any code inside the definition of C<sub end>
1257is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1258for more information on C<ActionClass>.
1260=item *
1390ef0e 1262Because C<sub end> is empty, this effectively just runs the default
1263logic in C<RenderView>. However, you can easily extend the
1264C<RenderView> logic by adding your own code inside the empty method body
1265(C<{}>) created by the Catalyst Helpers when we first ran the
1266C<catalyst.pl> to initialize our application. See
1267L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
3533daff 1268detailed information on how to extended C<RenderView> in C<sub end>.
1273=head2 Using The Default Template Name
1390ef0e 1275By default, C<Catalyst::View::TT> will look for a template that uses the
1276same name as your controller action, allowing you to save the step of
1277manually specifying the template name in each action. For example, this
1278would allow us to remove the
1279C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1280C<list> action in the Books controller. Open
3533daff 1281C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line
1282to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1283has changed):
1285 =head2 list
1287 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1289 =cut
1291 sub list : Local {
1292 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1293 # 'Context' that's used to 'glue together' the various components
1294 # that make up the application
1295 my ($self, $c) = @_;
1297 # Retrieve all of the book records as book model objects and store in the
1298 # stash where they can be accessed by the TT template
d0496197 1299 $c->stash->{books} = [$c->model('DB::Books')->all];
3533daff 1300
1301 # Set the TT template to use. You will almost always want to do this
1302 # in your action methods (actions methods respond to user input in
1303 # your controllers).
1304 #$c->stash->{template} = 'books/list.tt2';
1305 }
3533daff 1307
1390ef0e 1308You should now be able to restart the development server as per the
3533daff 1309previous section and access the L<http://localhost:3000/books/list>
1310as before.
1312B<NOTE:> Please note that if you use the default template technique,
1313you will B<not> be able to use either the C<$c-E<gt>forward> or
1390ef0e 1314the C<$c-E<gt>detach> mechanisms (these are discussed in Part 2 and
3533daff 1315Part 9 of the Tutorial).
1318=head2 Return To A Manually-Specified Template
1320In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1321later in the tutorial, you should remove the comment from the
1322statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>:
1324 $c->stash->{template} = 'books/list.tt2';
1390ef0e 1326Then delete the C<TEMPLATE_EXTENSION> line in
3533daff 1327C<lib/MyApp/View/TT.pm>.
1390ef0e 1329You should then be able to restart the development server and
3533daff 1330access L<http://localhost:3000/books/list> in the same manner as
1331with earlier sections.
1334=head1 AUTHOR
1336Kennedy Clark, C<hkclark@gmail.com>
1338Please report any errors, issues or suggestions to the author. The
1339most recent version of the Catalyst Tutorial can be found at
82ab4bbf 1340L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
3533daff 1341
45c7830f 1342Copyright 2006-2008, Kennedy Clark, under Creative Commons License
8482d557 1343(L<http://creativecommons.org/licenses/by-sa/3.0/us/>).