Suggestion from Stefan Kangas about "un-indenting" code in Emacs (thanks, Stefan)
[catagits/Catalyst-Manual.git] / lib / Catalyst / Manual / Tutorial / MoreCatalystBasics.pod
3533daff 1=head1 NAME
4b4d3884 3Catalyst::Manual::Tutorial::MoreCatalystBasics - Catalyst Tutorial - Chapter 3: More Catalyst Application Development Basics
3533daff 4
6=head1 OVERVIEW
4b4d3884 8This is B<Chapter 3 of 10> for the Catalyst tutorial.
3533daff 9
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
4b4d3884 59This chapter of the tutorial builds on the work done in Chapter 2 to
60explore some features that are more typical of "real world" web
61applications. From this chapter of the tutorial onward, we will be
62building a simple book database application. Although the application
63will be too limited to be of use to anyone, it should provide a basic
64environment where we can explore a variety of features used in
65virtually all web applications.
3533daff 66
4d63a0d5 67You can check out 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
a586a09f 71Please take a look at
72L<Catalyst::Manual::Tutorial::Intro/CATALYST INSTALLATION> before
73doing the rest of this tutorial. Although the tutorial should work
74correctly under most any recent version of Perl running on any
75operating system, the tutorial has been written using Debian 5 and
76tested to be sure it runs correctly in this environment.
3533daff 78
1390ef0e 81The remainder of the tutorial will build an application called C<MyApp>.
82First use the Catalyst C<> script to initialize the framework
83for the C<MyApp> application (make sure you aren't still inside the
4b4d3884 84directory of the C<Hello> application from the previous chapter of the
acbd7bdd 85tutorial or in a directory that already has a "MyApp" subdirectory):
3533daff 86
87 $ MyApp
88 created "MyApp"
89 created "MyApp/script"
90 created "MyApp/lib"
91 created "MyApp/root"
92 ...
93 created "MyApp/script/"
94 $ cd MyApp
4b4d3884 96This creates a similar skeletal structure to what we saw in Chapter 2 of
1390ef0e 97the tutorial, except with C<MyApp> and C<myapp> substituted for
3533daff 98C<Hello> and C<hello>.
103One of the greatest benefits of Catalyst is that it has such a large
1390ef0e 104library of plugins and base classes available. Plugins are used to
105seamlessly integrate existing Perl modules into the overall Catalyst
106framework. In general, they do this by adding additional methods to the
107C<context> object (generally written as C<$c>) that Catalyst passes to
108every component throughout the framework.
3533daff 109
110By default, Catalyst enables three plugins/flags:
112=over 4
1390ef0e 114=item *
3533daff 115
116C<-Debug> Flag
118Enables the Catalyst debug output you saw when we started the
119C<script/> development server earlier. You can remove
79a529cc 120this item when you place your application into production.
3533daff 121
1390ef0e 122As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
123Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
124line of your application class will be plugins, Catalyst supports a
125limited number of flag options (of these, C<-Debug> is the most
126common). See the documentation for C<> to get details on
127other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
3533daff 128
129If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
132B<TIP>: Depending on your needs, it can be helpful to permanently
133remove C<-Debug> from C<lib/> and then use the C<-d> option
134to C<script/> to re-enable it just for the development
1390ef0e 135server. We will not be using that approach in the tutorial, but feel
3533daff 136free to make use of it in your own projects.
138=item *
142C<ConfigLoader> provides an automatic way to load configurable
c010ae0d 143parameters for your application from a central
144L<Config::General|Config::General> file (versus having the values
145hard-coded inside your Perl modules). Config::General uses syntax
146very similar to Apache configuration files. We will see how to use
147this feature of Catalyst during the authentication and authorization
4b4d3884 148sections (Chapter 5 and Chapter 6).
3533daff 149
1435672d 150B<IMPORTANT NOTE:> If you are using a version of
151L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, be aware
152that Catalyst changed the default format from YAML to the more
153straightforward C<Config::General> style. This tutorial uses the
154newer C<myapp.conf> file for C<Config::General>. However, Catalyst
155supports both formats and will automatically use either C<myapp.conf>
156or C<myapp.yml> (or any other format supported by
157L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
158L<Config::Any|Config::Any>). If you are using a version of
159Catalyst::Devel prior to 1.06, you can convert to the newer format by
160simply creating the C<myapp.conf> file manually and deleting
161C<myapp.yml>. The default contents of the C<myapp.conf> you create
162should only consist of one line:
164 name MyApp
15e1d0b2 165
1390ef0e 166B<TIP>: This script can be useful for converting between configuration
15e1d0b2 167formats:
1390ef0e 169 perl -Ilib -e 'use MyApp; use Config::General;
15e1d0b2 170 Config::General->new->save_file("myapp.conf", MyApp->config);'
3533daff 172=item *
4d63a0d5 176C<Static::Simple> provides an easy way to serve static content, such
177as images and CSS files, from the development server.
3533daff 178
94d8da41 181For our application, we want to add one new plugin into the mix. To
1390ef0e 182do this, edit C<lib/> (this file is generally referred to as
acbd7bdd 183your I<application class>) and delete the lines with:
3533daff 184
acbd7bdd 185 use Catalyst qw/-Debug
186 ConfigLoader
187 Static::Simple/;
3533daff 188
1390ef0e 189Then replace it with:
b411df01 190
acbd7bdd 191 # Load plugins
192 use Catalyst qw/-Debug
193 ConfigLoader
194 Static::Simple
196 StackTrace
197 /;
1390ef0e 198
94d8da41 199B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
acbd7bdd 200techniques to load these plugins/flags. For example, you might see
201the following:
94d8da41 202
acbd7bdd 203 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
94d8da41 204
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<>, 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
4d63a0d5 246C<GET> and C<POST> requests from the user's web browser.
3533daff 247
248Use the Catalyst C<create> script to add a controller for book-related
251 $ script/ 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/"
255 created "/home/me/MyApp/script/../t/controller_Books.t"
4b4d3884 257Then edit C<lib/MyApp/Controller/> (as discussed in Chapter 2 of
1390ef0e 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
245b41d1 297Catalyst actions are regular Perl methods, but they make use of
298attributes (the "C<: Local>" next to the "C<sub list>" in the code
0416017e 299above) to provide additional information to the Catalyst dispatcher
300logic (note that the space between the colon and the attribute name is
4d63a0d5 301optional; you will see attributes written both ways). Most Catalyst
245b41d1 302Controllers use one of five action types:
0416017e 303
304=over 4
306=item *
245b41d1 308B<:Private> -- Use C<:Private> for methods that you want to make into
4d63a0d5 309an action, but you do not want Catalyst to directly expose
245b41d1 310to your users. Catalyst will not map C<:Private> methods to a URI.
311Use them for various sorts of "special" methods (the C<begin>,
312C<auto>, etc. discussed below) or for methods you want to be able to
313C<forward> or C<detach> to. (If the method is a plain old "helper
314method" that you don't want to be an action at all, then just define
315the method without any attribute -- you can call it in your code, but
316the Catalyst dispatcher will ignore it.)
0416017e 317
245b41d1 318There are five types of "special" build-in C<:Private> actions:
319C<begin>, C<end>, C<default>, C<index>, and C<auto>.
0416017e 320
26c9cad5 321=over 4
0416017e 323=item *
325With C<begin>, C<end>, C<default>, C<index> private actions, only the
326most specific action of each type will be called. For example, if you
327define a C<begin> action in your controller it will I<override> a
328C<begin> action in your application/root controller -- I<only> the
329action in your controller will be called.
331=item *
333Unlike the other actions where only a single method is called for each
334request, I<every> auto action along the chain of namespaces will be
335called. Each C<auto> action will be called I<from the application/root
336controller down through the most specific class>.
340=item *
245b41d1 342B<:Path> -- C<:Path> actions let you map a method to an explicit URI
343path. For example, "C<:Path('list')>" in
0416017e 344C<lib/MyApp/Controller/> would match on the URL
245b41d1 345C<http://localhost:3000/books/list> but "C<:Path('/list')>" would match
346on C<http://localhost:3000/list>. You can use C<:Args()> to specify
7e8cd009 347how many arguments an action should accept. See
245b41d1 348L<Catalyst::Manual::Intro/Action_types> for more information and a few
0416017e 349examples.
351=item *
245b41d1 353B<:Local> -- C<:Local> is merely a shorthand for
354"C<:Path('_name_of_method_')>". For example, these are equivalent:
355"C<sub create_book :Local {...}>" and
356"C<sub create_book :Path('create_book') {...}>".
358=item *
360B<:Global> -- C<:Global> is merely a shorthand for
361"C<:Path('/_name_of_method_')>". For example, these are equivalent:
362"C<sub create_book :Global {...}>" and
363"C<sub create_book :Path('/create_book') {...}>".
365=item *
367B<:Chained> -- Newer Catalyst applications tend to use the Chained
0416017e 368dispatch form of action types because of its power and flexibility.
4d63a0d5 369It allows a series of controller methods to be automatically dispatched
0416017e 370to service a single user request. See
372and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
373for more information on chained actions.
377You should refer to L<Catalyst::Manual::Intro/Action_types> for
378additional information and for coverage of some lesser-used action
245b41d1 379types not discussed here (C<Regex> and C<LocalRegex>).
3533daff 380
4d63a0d5 384As mentioned in Chapter 2 of the tutorial, views are where you render
385output, typically for display in the user's web browser (but also
386possibly using into output-generation systems, such as PDF or JSON).
387The code in C<lib/MyApp/View> selects the I<type> of view to use, with
388the actual rendering template found in the C<root> directory. As with
389virtually every aspect of Catalyst, options abound when it comes to the
390specific view technology you adopt inside your application. However,
391most Catalyst applications use the Template Toolkit, known as TT (for
392more information on TT, see L<>). Other
393somewhat popular view technologies include Mason
394(L<> and L<>) and
1390ef0e 395L<HTML::Template> (L<>).
398=head2 Create a Catalyst View
3533daff 399
400When using TT for the Catalyst view, there are two main helper scripts:
402=over 4
404=item *
408=item *
de966eb4 414Both helpers are similar. C<TT> creates the C<lib/MyApp/View/>
3533daff 415file and leaves the creation of any hierarchical template organization
416entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
4b4d3884 417test cases will be discussed in Chapter 8.) C<TTSite>, on the other hand,
de966eb4 418creates a modular and hierarchical view layout with
1390ef0e 419separate Template Toolkit (TT) files for common header and footer
420information, configuration values, a CSS stylesheet, and more.
de966eb4 422While C<TTSite> was useful to bootstrap a project, its use is now
4d63a0d5 423deprecated and it should be considered historical. For most Catalyst
de966eb4 424applications it adds redundant functionality and structure; many in the
425Catalyst community recommend that it's easier to learn both Catalyst and
426Template Toolkit if you use the more basic C<TT> approach.
427Consequently, this tutorial will use "plain old TT."
1390ef0e 428
429Enter the following command to enable the C<TT> style of view
3533daff 430rendering for this tutorial:
1390ef0e 432 $ script/ view TT TT
3533daff 433 exists "/home/me/MyApp/script/../lib/MyApp/View"
434 exists "/home/me/MyApp/script/../t"
1390ef0e 435 created "/home/me/MyApp/script/../lib/MyApp/View/"
436 created "/home/me/MyApp/script/../t/view_TT.t"
3533daff 437
1390ef0e 438This simply creates a view called C<TT> (the second 'TT' argument) in
439a file called C<> (the first 'TT' argument). It is now up to you
440to decide how you want to structure your view layout. For the
441tutorial, we will start with a very simple TT template to initially
442demonstrate the concepts, but quickly migrate to a more typical
443"wrapper page" type of configuration (where the "wrapper" controls the
444overall "look and feel" of your site from a single file or set of
3533daff 446
1390ef0e 447Edit C<lib/MyApp/View/> and you should see that the default
448contents contains something similar to the following:
3533daff 449
1390ef0e 450 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
3533daff 451
1390ef0e 452And update it to match:
454 __PACKAGE__->config(
455 # Change default TT extension
457 # Set the location for TT files
6abd3023 459 MyApp->path_to( 'root', 'src' ),
1390ef0e 460 ],
461 );
3533daff 462
1390ef0e 463B<NOTE:> Make sure to add a comma after '.tt2' outside the single
191dee29 466This changes the default extension for Template Toolkit from '.tt' to
1390ef0e 467'.tt2' and changes the base directory for your template files from
de966eb4 468C<root> to C<root/src>. These changes from the default are done mostly
469to facilitate the application we're developing in this tutorial; as with
470most things Perl, there's more than one way to do it...
1390ef0e 471
acbd7bdd 472B<Note:> We will use C<root/src> as the base directory for our
473template files, which a full naming convention of
474C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
475use C<root/> as the base (with a full filename pattern of
1390ef0e 478
479=head2 Create a TT Template Page
3533daff 480
481First create a directory for book-related TT templates:
1390ef0e 483 $ mkdir -p root/src/books
3533daff 484
485Then create C<root/src/books/list.tt2> in your editor and enter:
487 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
488 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
489 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
490 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
1390ef0e 492 [% # Provide a title -%]
3533daff 493 [% META title = 'Book List' -%]
495 <table>
496 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
497 [% # Display each book in a table row %]
498 [% FOREACH book IN books -%]
499 <tr>
500 <td>[% book.title %]</td>
501 <td>[% book.rating %]</td>
a46b474e 502 <td></td>
3533daff 503 </tr>
504 [% END -%]
505 </table>
507As indicated by the inline comments above, the C<META title> line uses
1390ef0e 508TT's META feature to provide a title to the "wrapper" that we will
509create later. Meanwhile, the C<FOREACH> loop iterates through each
510C<book> model object and prints the C<title> and C<rating> fields.
3533daff 511
4d63a0d5 512The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
513supports a wide variety of directives for "calling" other files,
514looping, conditional logic, etc. In general, TT simplifies the usual
515range of Perl operators down to the single dot (C<.>) operator. This
516applies to operations as diverse as method calls, hash lookups, and list
517index values (see
518L<> for
519details and examples). In addition to the usual C<Template> module Pod
520documentation, you can access the TT manual at
55beb65d 521L<>.
3533daff 522
1390ef0e 523B<TIP:> While you can build all sorts of complex logic into your TT
524templates, you should in general keep the "code" part of your templates
525as simple as possible. If you need more complex logic, create helper
526methods in your model that abstract out a set of code into a single call
527from your TT template. (Note that the same is true of your controller
528logic as well -- complex sections of code in your controllers should
529often be pulled out and placed into your model objects.)
532=head2 Test Run The Application
534To test your work so far, first start the development server:
536 $ script/
538Then point your browser to L<http://localhost:3000> and you should
539still get the Catalyst welcome page. Next, change the URL in your
540browser to L<http://localhost:3000/books/list>. If you have
541everything working so far, you should see a web page that displays
542nothing other than our column headers for "Title", "Rating", and
543"Author(s)" -- we will not see any books until we get the database and
544model working below.
546If you run into problems getting your application to run correctly, it
547might be helpful to refer to some of the debugging techniques covered in
548the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the
3533daff 550
554In this step, we make a text file with the required SQL commands to
1390ef0e 555create a database table and load some sample data. We will use SQLite,
556a popular database that is lightweight and easy to use. Open
557C<myapp01.sql> in your editor and enter:
3533daff 558
559 --
560 -- Create a very simple database to hold book and author information
561 --
562 CREATE TABLE books (
564 title TEXT ,
565 rating INTEGER
566 );
567 -- 'book_authors' is a many-to-many join table between books & authors
568 CREATE TABLE book_authors (
569 book_id INTEGER,
570 author_id INTEGER,
571 PRIMARY KEY (book_id, author_id)
572 );
573 CREATE TABLE authors (
575 first_name TEXT,
576 last_name TEXT
577 );
578 ---
579 --- Load some sample data
580 ---
581 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
582 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
583 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
584 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
585 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
586 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
587 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
588 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
589 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
590 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
591 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
592 INSERT INTO authors VALUES (7, 'Nathan', 'Torkington');
593 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
594 INSERT INTO book_authors VALUES (1, 1);
595 INSERT INTO book_authors VALUES (1, 2);
596 INSERT INTO book_authors VALUES (1, 3);
597 INSERT INTO book_authors VALUES (2, 4);
598 INSERT INTO book_authors VALUES (3, 5);
599 INSERT INTO book_authors VALUES (4, 6);
600 INSERT INTO book_authors VALUES (4, 7);
601 INSERT INTO book_authors VALUES (5, 8);
3533daff 603Then use the following command to build a C<myapp.db> SQLite database:
605 $ sqlite3 myapp.db < myapp01.sql
607If you need to create the database more than once, you probably want to
608issue the C<rm myapp.db> command to delete the database before you use
1390ef0e 609the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
3533daff 610
611Once the C<myapp.db> database file has been created and initialized, you
612can use the SQLite command line environment to do a quick dump of the
613database contents:
615 $ sqlite3 myapp.db
acbd7bdd 616 SQLite version 3.5.9
3533daff 617 Enter ".help" for instructions
618 sqlite> select * from books;
619 1|CCSP SNRS Exam Certification Guide|5
620 2|TCP/IP Illustrated, Volume 1|5
621 3|Internetworking with TCP/IP Vol.1|4
622 4|Perl Cookbook|5
623 5|Designing with Web Standards|5
624 sqlite> .q
625 $
629 $ sqlite3 myapp.db "select * from books"
630 1|CCSP SNRS Exam Certification Guide|5
631 2|TCP/IP Illustrated, Volume 1|5
632 3|Internetworking with TCP/IP Vol.1|4
633 4|Perl Cookbook|5
634 5|Designing with Web Standards|5
636As with most other SQL tools, if you are using the full "interactive"
637environment you need to terminate your SQL commands with a ";" (it's not
638required if you do a single SQL statement on the command line). Use
639".q" to exit from SQLite from the SQLite interactive mode and return to
640your OS command prompt.
a6d800ac 642For using other databases, such as PostgreSQL or MySQL, see
643L<Appendix 2|Catalyst::Manual::Tutorial::Appendices>.
3533daff 644
acbd7bdd 645
8a472b34 646=head1 DATABASE ACCESS WITH DBIx::Class
3533daff 647
27909ed4 648Catalyst can be used with virtually any form of datastore available
649via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
650can be used to access databases through the traditional Perl C<DBI>
651interface or you can use a model to access files of any type on the
652filesystem. However, most Catalyst applications use some form of
653object-relational mapping (ORM) technology to create objects
654associated with tables in a relational database. Matt Trout's
655L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
656as the Perl-based ORM technology of choice. Most new Catalyst
a46b474e 657applications rely on DBIx::Class, as will this tutorial.
3533daff 658
a46b474e 659Although DBIx::Class has included support for a C<create=dynamic> mode
660to automatically read the database structure every time the
661application starts, it's use is no longer recommended. While it can
662make for "flashy" demos, the use of the C<create=static> mode we use
663below can be implemented just as quickly and provides many advantages
664(such as the ability to add your own methods to the overall DBIC
665framework, a technique that we see in Chapter 4).
3533daff 666
1390ef0e 667
a46b474e 668=head2 Make Sure You Have a Recent Version of the DBIx::Class Model
27909ed4 669
670First, let's be sure we have a recent version of the DBIC helper,
671L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
672running this command:
674 $ perl -MCatalyst::Model::DBIC::Schema -e \
675 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
676 0.23
678If you don't have version 0.23 or higher, please run this command
679to install it directly from CPAN:
681 $ sudo cpan Catalyst::Model::DBIC::Schema
683And re-run the version print command to verify that you are now at
6840.23 or higher.
a46b474e 687=head2 Create Static DBIx::Class Schema Files
27909ed4 688
98fd8420 689Before you continue, make sure your C<myapp.db> database file is in
690the application's topmost directory. Now use the model helper with
691the C<create=static> option to read the database with
27909ed4 692L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
693automatically build the required files for us:
3533daff 694
4ab6212d 695 $ script/ model DB DBIC::Schema MyApp::Schema \
27909ed4 696 create=static components=TimeStamp dbi:SQLite:myapp.db
1390ef0e 697 exists "/home/me/MyApp/script/../lib/MyApp/Model"
698 exists "/home/me/MyApp/script/../t"
27909ed4 699 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
700 Schema dump completed.
1390ef0e 701 created "/home/me/MyApp/script/../lib/MyApp/Model/"
702 created "/home/me/MyApp/script/../t/model_DB.t"
3533daff 703
27909ed4 704The C<script/> command breaks down like this:
706=over 4
708=item *
710C<DB> is the name of the model class to be created by the helper in
713=item *
715C<DBIC::Schema> is the type of the model to create.
717=item *
719C<MyApp::Schema> is the name of the DBIC schema file written to
722=item *
724C<create=static> causes
725L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
726load the schema as it runs and then write that information out
727into files.
729=item *
731C<components=TimeStamp> causes the help to include the
732L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp> DBIC component.
734=item *
736And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
737for use with SQLite.
741If you look in the C<lib/MyApp/> file, you will find that it
742only contains a call to the C<load_namespaces> method. You will also
743find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
744has a subdirectory called "Result". This "Result" subdirectory then
745has files named according to each of the tables in our simple database
746(C<>, C<>, and C<>). These three
a46b474e 747files are called "Result Classes" in DBIx::Class nomenclature. Although the
27909ed4 748Result Class files are named after tables in our database, the classes
749correspond to the I<row-level data> that is returned by DBIC (more on
750this later, especially in
751L<Catalyst::Manual::Tutorial::BasicCRUD/EXPLORING THE POWER OF DBIC>).
753The idea with the Result Source files created under
754C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
755edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
756warning. If you place all of your changes below that point in the
757file, you can regenerate the automatically created information at the
758top of each file should your database structure get updated.
760Also note the "flow" of the model information across the various files
761and directories. Catalyst will initially load the model from
762C<lib/MyApp/Model/>. This file contains a reference to
763C<lib/MyApp/>, so that file is loaded next. Finally, the
764call to C<load_namespaces> in C<> will load each of the
765"Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
766The final outcome is that Catalyst will dynamically create three
767table-specific Catalyst models every time the application starts (you
768can see these three model files listed in the debug output generated
769when you launch the application).
771B<NOTE:> Older versions of
772L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
a46b474e 773deprecated DBIx::Class C<load_classes> technique instead of the newer
27909ed4 774C<load_namspaces>. For new applications, please try to use
775C<load_namespaces> since it more easily supports a very useful DBIC
776technique called "ResultSet Classes." If you need to convert an
777existing application from "load_classes" to "load_namespaces," you can
778use this process to automate the migration (but first make sure you
779have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
781 $ # First delete the existing schema file to disable "compatibility" mode
782 $ rm lib/MyApp/
783 $
784 $ # Then re-run the helper to build the files for "load_namespaces"
785 $ script/ model DB DBIC::Schema MyApp::Schema \
786 create=static components=TimeStamp dbi:SQLite:myapp.db
787 $
788 $ # Now convert the existing files over
789 $ cd lib/MyApp/Schema
790 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
791 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
792 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
793 $ cd ../../..
794 $
795 $ # And finally delete the old files
796 $ rm lib/MyApp/Schema/*.pm
798The "C<perl -MIO::ALL ...>" script will copy all the customized
799relationship (and other) information below "C<# DO NOT MODIFY>" line
800from the old files in C<lib/MyApp/Schema> to the new files in
801C<lib/MyApp/Schema/Result> (we will be starting to add some
802"customized relationship information in the section below).
3533daff 803
dc9a0503 804
acbd7bdd 807Open C<lib/MyApp/Controller/> and un-comment the model code we
808left disabled earlier so that your version matches the following (un-
809comment the line containing C<[$c-E<gt>model('DB::Books')-E<gt>all]>
810and delete the next 2 lines):
1390ef0e 811
812 =head2 list
814 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
816 =cut
818 sub list : Local {
819 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
820 # 'Context' that's used to 'glue together' the various components
821 # that make up the application
822 my ($self, $c) = @_;
824 # Retrieve all of the book records as book model objects and store in the
825 # stash where they can be accessed by the TT template
826 $c->stash->{books} = [$c->model('DB::Books')->all];
828 # Set the TT template to use. You will almost always want to do this
829 # in your action methods (action methods respond to user input in
830 # your controllers).
831 $c->stash->{template} = 'books/list.tt2';
832 }
1435672d 834B<TIP>: You may see the C<$c-E<gt>model('DB::Books')> un-commented
835above written as C<$c-E<gt>model('DB')-E<gt>resultset('Books')>. The
c93b5eaa 836two are equivalent. Either way, C<$c-E<gt>model> returns a
837L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
4d63a0d5 838against the database and iterating over the set of results that is
c93b5eaa 839returned.
841We are using the C<-E<gt>all> to fetch all of the books. DBIC
842supports a wide variety of more advanced operations to easily do
843things like filtering and sorting the results. For example, the
518f3851 844following could be used to sort the results by descending title:
c93b5eaa 845
846 $c->model('DB::Books')->search({}, {order_by => 'title DESC'});
848Some other examples are provided in
849L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
850additional information found at L<DBIx::Class::ResultSet/search>,
853and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
1390ef0e 854
856=head2 Test Run The Application
3533daff 857
1435672d 858First, let's enable an environment variable that causes DBIx::Class to
acbd7bdd 859dump the SQL statements used to access the database. This is a
1435672d 860helpful trick when you are trying to debug your database-oriented
3533daff 862
863 $ export DBIC_TRACE=1
4d63a0d5 865This assumes you are using bash as your shell -- adjust accordingly if
3533daff 866you are using a different shell (for example, under tcsh, use
867C<setenv DBIC_TRACE 1>).
d0496197 869B<NOTE:> You can also set this in your code using
3533daff 870C<$class-E<gt>storage-E<gt>debug(1);>. See
871L<DBIx::Class::Manual::Troubleshooting> for details (including options
4d63a0d5 872to log to a file instead of displaying to the Catalyst development server
3533daff 873log).
1390ef0e 875Then launch the Catalyst development server. The log output should
876display something like:
3533daff 877
acbd7bdd 878 $ script/
3533daff 879 [debug] Debug messages enabled
1390ef0e 880 [debug] Statistics enabled
3533daff 881 [debug] Loaded plugins:
882 .----------------------------------------------------------------------------.
1390ef0e 883 | Catalyst::Plugin::ConfigLoader 0.20 |
884 | Catalyst::Plugin::StackTrace 0.08 |
3533daff 885 | Catalyst::Plugin::Static::Simple 0.20 |
886 '----------------------------------------------------------------------------'
888 [debug] Loaded dispatcher "Catalyst::Dispatcher"
889 [debug] Loaded engine "Catalyst::Engine::HTTP"
890 [debug] Found home "/home/me/MyApp"
45d511e0 891 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
3533daff 892 [debug] Loaded components:
893 .-----------------------------------------------------------------+----------.
894 | Class | Type |
895 +-----------------------------------------------------------------+----------+
896 | MyApp::Controller::Books | instance |
897 | MyApp::Controller::Root | instance |
d0496197 898 | MyApp::Model::DB | instance |
899 | MyApp::Model::DB::Authors | class |
900 | MyApp::Model::DB::BookAuthors | class |
901 | MyApp::Model::DB::Books | class |
3533daff 902 | MyApp::View::TT | instance |
903 '-----------------------------------------------------------------+----------'
905 [debug] Loaded Private actions:
906 .----------------------+--------------------------------------+--------------.
907 | Private | Class | Method |
908 +----------------------+--------------------------------------+--------------+
909 | /default | MyApp::Controller::Root | default |
910 | /end | MyApp::Controller::Root | end |
1390ef0e 911 | /index | MyApp::Controller::Root | index |
3533daff 912 | /books/index | MyApp::Controller::Books | index |
913 | /books/list | MyApp::Controller::Books | list |
914 '----------------------+--------------------------------------+--------------'
916 [debug] Loaded Path actions:
917 .-------------------------------------+--------------------------------------.
918 | Path | Private |
919 +-------------------------------------+--------------------------------------+
1390ef0e 920 | / | /default |
921 | / | /index |
922 | /books | /books/index |
3533daff 923 | /books/list | /books/list |
924 '-------------------------------------+--------------------------------------'
acbd7bdd 926 [info] MyApp powered by Catalyst 5.71000
927 You can connect to your server at http://debian:3000
3533daff 928
1390ef0e 929B<NOTE:> Be sure you run the C<script/> command from
930the 'base' directory of your application, not inside the C<script>
931directory itself or it will not be able to locate the C<myapp.db>
932database file. You can use a fully qualified or a relative path to
933locate the database file, but we did not specify that when we ran the
3533daff 934model helper earlier.
936Some things you should note in the output above:
938=over 4
1390ef0e 940=item *
3533daff 941
1390ef0e 942Catalyst::Model::DBIC::Schema dynamically created three model classes,
943one to represent each of the three tables in our database
d0496197 944(C<MyApp::Model::DB::Authors>, C<MyApp::Model::DB::BookAuthors>,
945and C<MyApp::Model::DB::Books>).
3533daff 946
1390ef0e 947=item *
3533daff 948
949The "list" action in our Books controller showed up with a path of
954Point your browser to L<http://localhost:3000> and you should still get
955the Catalyst welcome page.
957Next, to view the book list, change the URL in your browser to
958L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 959books loaded by the C<myapp01.sql> script above without any formatting.
960The rating for each book should appear on each row, but the "Author(s)"
191dee29 961column will still be blank (we will fill that in later).
3533daff 962
a46b474e 963Also notice in the output of the C<script/> that
964DBIx::Class used the following SQL to retrieve the data:
3533daff 965
966 SELECT, me.title, me.rating FROM books me
968because we enabled DBIC_TRACE.
0c51850e 970You now have the beginnings of a simple but workable web application.
3533daff 971Continue on to future sections and we will develop the application
972more fully.
1390ef0e 975=head1 CREATE A WRAPPER FOR THE VIEW
acbd7bdd 977When using TT, you can (and should) create a wrapper that will
1390ef0e 978literally wrap content around each of your templates. This is
979certainly useful as you have one main source for changing things that
980will appear across your entire site/application instead of having to
981edit many individual files.
984=head2 Configure For The Wrapper
986In order to create a wrapper, you must first edit your TT view and
987tell it where to find your wrapper file. Your TT view is located in
990Edit C<lib/MyApp/View/> and change it to match the following:
992 __PACKAGE__->config(
993 # Change default TT extension
995 # Set the location for TT files
c2dfb562 997 MyApp->path_to( 'root', 'src' ),
1390ef0e 998 ],
999 # Set to 1 for detailed timer stats in your HTML as comments
1000 TIMER => 0,
1001 # This is your wrapper template located in the 'root/src'
1002 WRAPPER => 'wrapper.tt2',
1003 );
1006=head2 Create the Wrapper Template File and Stylesheet
1008Next you need to set up your wrapper template. Basically, you'll want
1009to take the overall layout of your site and put it into this file.
1010For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1012 <?xml version="1.0" encoding="UTF-8"?>
1013 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "">
1014 <html xmlns="" xml:lang="en" lang="en">
1015 <head>
1016 <title>[% template.title or "My Catalyst App!" %]</title>
1017 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1018 </head>
1020 <body>
1021 <div id="outer">
1022 <div id="header">
1023 [%# Your logo could go here -%]
1024 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1025 [%# Insert the page title -%]
1026 <h1>[% template.title or site.title %]</h1>
1027 </div>
1029 <div id="bodyblock">
1030 <div id="menu">
1031 Navigation:
1032 <ul>
1033 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1034 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1390ef0e 1035 </ul>
1036 </div><!-- end menu -->
1038 <div id="content">
1039 [%# Status and error messages %]
1040 <span class="message">[% status_msg %]</span>
1041 <span class="error">[% error_msg %]</span>
1042 [%# This is where TT will stick all of your template's contents. -%]
1043 [% content %]
1044 </div><!-- end content -->
1045 </div><!-- end bodyblock -->
1047 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 1048 </div><!-- end outer -->
1390ef0e 1049
1050 </body>
1051 </html>
1053Notice the status and error message sections in the code above:
1055 <span class="status">[% status_msg %]</span>
1056 <span class="error">[% error_msg %]</span>
1058If we set either message in the Catalyst stash (e.g.,
1059C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1060will be displayed whenever any view used by that request is rendered.
1061The C<message> and C<error> CSS styles can be customized to suit your
1062needs in the C<root/static/css/main.css> file we create below.
1066=over 4
1068=item *
1070The Catalyst stash only lasts for a single HTTP request. If
1071you need to retain information across requests you can use
1072L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
4b4d3884 1073Catalyst sessions in the Authentication chapter of the tutorial).
1390ef0e 1074
1075=item *
1077Although it is beyond the scope of this tutorial, you may wish to use
1078a JavaScript or AJAX tool such as jQuery (L<>) or
1079Dojo (L<>).
1084=head3 Create A Basic Stylesheet
1086First create a central location for stylesheets under the static
1089 $ mkdir root/static/css
1091Then open the file C<root/static/css/main.css> (the file referenced in
1092the stylesheet href link of our wrapper above) and add the following
1095 #header {
1096 text-align: center;
1097 }
1098 #header h1 {
1099 margin: 0;
1100 }
1101 #header img {
1102 float: right;
1103 }
1104 #footer {
1105 text-align: center;
1106 font-style: italic;
1107 padding-top: 20px;
1108 }
1109 #menu {
1110 font-weight: bold;
1111 background-color: #ddd;
1112 }
1113 #menu ul {
1114 list-style: none;
1115 float: left;
1116 margin: 0;
1117 padding: 0 0 50% 5px;
1118 font-weight: normal;
1119 background-color: #ddd;
1120 width: 100px;
1121 }
1122 #content {
1123 margin-left: 120px;
1124 }
1125 .message {
1126 color: #390;
1127 }
1128 .error {
1129 color: #f00;
1130 }
1132You may wish to check out a "CSS Framework" like Emastic
1133(L<>) as a way to quickly
1134provide lots of high-quality CSS functionality.
1137=head2 Test Run The Application
1139Restart the development server and hit "Reload" in your web browser
1140and you should now see a formatted version of our basic book list.
1141Although our wrapper and stylesheet are obviously very simple, you
1142should see how it allows us to control the overall look of an entire
1143website from two central files. To add new pages to the site, just
1144provide a template that fills in the C<content> section of our wrapper
1145template -- the wrapper will provide the overall feel of the page.
a46b474e 1148=head2 Updating the Generated DBIx::Class Result Class Files
3533daff 1149
acbd7bdd 1150Let's manually add some relationship information to the auto-generated
1151Result Class files. (Note: if you are using a database other than
1152SQLite, such as PostgreSQL, then the relationship could have been
1153automatically placed in the Result Class files. If so, you can skip
4ab6212d 1154this step.) First edit C<lib/MyApp/Schema/Result/> and add the
acbd7bdd 1155following text below the C<# You can replace this text...> comment:
3533daff 1156
1157 #
1158 # Set relationships:
1390ef0e 1159 #
3533daff 1160
1161 # has_many():
1162 # args:
1163 # 1) Name of relationship, DBIC will create accessor with this name
1164 # 2) Name of the model class referenced by this relationship
1435672d 1165 # 3) Column name in *foreign* table (aka, foreign key in peer table)
4ab6212d 1166 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthors', 'book_id');
3533daff 1167
1168 # many_to_many():
1169 # args:
1170 # 1) Name of relationship, DBIC will create accessor with this name
1390ef0e 1171 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1172 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1173 # You must already have the has_many() defined to use a many_to_many().
1174 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1177B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1178file. As with any Perl package, we need to end the last line with
1179a statement that evaluates to C<true>. This is customarily done with
1180C<1;> on a line by itself.
acbd7bdd 1182C<Important Note:> Although this tutorial uses plural names for both
1183the names of the SQL tables and therefore the Result Classes (after
1184all, C<Schema::Loader> automatically named the Result Classes from the
a46b474e 1185names of the SQL tables it found), DBIx::Class users prefer singular
1186names for these items. B<Please try to use singular table and DBIC
acbd7bdd 1187model/Result Class names in your applications.> This tutorial will
1188migrate to singular names as soon as possible (patches welcomed).
1189B<Note that while singular is preferred for the DBIC model, plural is
1190perfectly acceptable for the names of the controller classes.> After
1191all, the C<> controller operates on multiple books.
a46b474e 1193This code defines both a C<has_many> and a C<many_to_many>
1194relationship. The C<many_to_many> relationship is optional, but it
1195makes it easier to map a book to its collection of authors. Without
1196it, we would have to "walk" though the C<book_authors> table as in
1197C<$book-E<gt>book_authors-E<gt>first-E<gt>author-E<gt>last_name> (we
1198will see examples on how to use DBIx::Class objects in your code soon,
1390ef0e 1199but note that because C<$book-E<gt>book_authors> can return multiple
1200authors, we have to use C<first> to display a single author).
a46b474e 1201C<many_to_many> allows us to use the shorter C<$book-E<gt>authors-
1202E<gt>first-E<gt>last_name>. Note that you cannot define a
1203C<many_to_many> relationship without also having the C<has_many>
1204relationship in place.
3533daff 1205
4ab6212d 1206Then edit C<lib/MyApp/Schema/Result/> and add relationship
3533daff 1207information as follows (again, be careful to put in above the C<1;> but
1208below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1210 #
1211 # Set relationships:
1212 #
1214 # has_many():
1215 # args:
4d63a0d5 1216 # 1) Name of relationship, DBIC will create an accessor with this name
3533daff 1217 # 2) Name of the model class referenced by this relationship
1435672d 1218 # 3) Column name in *foreign* table (aka, foreign key in peer table)
4ab6212d 1219 __PACKAGE__->has_many(book_author => 'MyApp::Schema::Result::BookAuthors', 'author_id');
3533daff 1220
1221 # many_to_many():
1222 # args:
1223 # 1) Name of relationship, DBIC will create accessor with this name
1224 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1225 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1226 # You must already have the has_many() defined to use a many_to_many().
1227 __PACKAGE__->many_to_many(books => 'book_author', 'book');
1390ef0e 1229Finally, do the same for the "join table,"
4ab6212d 1230C<lib/MyApp/Schema/Result/>:
3533daff 1231
1232 #
1233 # Set relationships:
1234 #
1236 # belongs_to():
1237 # args:
1238 # 1) Name of relationship, DBIC will create accessor with this name
1239 # 2) Name of the model class referenced by this relationship
1240 # 3) Column name in *this* table
4ab6212d 1241 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Books', 'book_id');
3533daff 1242
1243 # belongs_to():
1244 # args:
1245 # 1) Name of relationship, DBIC will create accessor with this name
1246 # 2) Name of the model class referenced by this relationship
1247 # 3) Column name in *this* table
4ab6212d 1248 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Authors', 'author_id');
3533daff 1249
1390ef0e 1251=head2 Run The Application
3533daff 1252
4d63a0d5 1253Run the Catalyst development server script with the C<DBIC_TRACE> option
1254(it might still be enabled from earlier in the tutorial, but here is an
1255alternate way to specify the option just in case):
3533daff 1256
1257 $ DBIC_TRACE=1 script/
1390ef0e 1259Make sure that the application loads correctly and that you see the
1260three dynamically created model class (one for each of the
4ab6212d 1261Result Classes we created).
3533daff 1262
acbd7bdd 1263Then hit the URL L<http://localhost:3000/books/list> with your browser
1264and be sure that the book list is displayed via the relationships
1265established above. You can leave the development server running for
1266the next step if you wish.
3533daff 1267
c2dfb562 1268B<Note:> You will not see the authors yet because the view does not yet
1269use the new relations. Read on to the next section where we update the
1270template to do that.
3533daff 1271
acbd7bdd 1275Let's add a new column to our book list page that takes advantage of
1276the relationship information we manually added to our schema files in
a46b474e 1277the previous section. Edit C<root/src/books/list.tt2> and replace
1278the "empty" tabase cell with the following:
3533daff 1279
acbd7bdd 1280 ...
3533daff 1281 <td>
1282 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1283 [% # loop in 'side effect notation' to load just the last names of the -%]
a0c5188a 1284 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
3533daff 1285 [% # a value, so nothing will be printed here. But, if you have something -%]
1286 [% # in TT that does return a method and you don't want it printed, you -%]
1287 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1288 [% # call it and discard the return value. -%]
1289 [% tt_authors = [ ];
1290 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1291 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1292 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1293 ([% tt_authors.size | html %])
1294 [% # Use another TT vmethod to join & print the names & comma separators -%]
1295 [% tt_authors.join(', ') | html %]
1296 </td>
acbd7bdd 1297 ...
3533daff 1298
1390ef0e 1299Then hit "Reload" in your browser (note that you don't need to reload
3533daff 1300the development server or use the C<-r> option when updating TT
1390ef0e 1301templates) and you should now see the number of authors each book has
1302along with a comma-separated list of the authors' last names. (If you
1303didn't leave the development server running from the previous step,
1304you will obviously need to start it before you can refresh your
1305browser window.)
1307If you are still running the development server with C<DBIC_TRACE>
1308enabled, you should also now see five more C<SELECT> statements in the
1309debug output (one for each book as the authors are being retrieved by
a46b474e 1310DBIx::Class):
3533daff 1311
c2dfb562 1312 SELECT, me.title, me.rating FROM books me:
acbd7bdd 1313 SELECT, author.first_name, author.last_name FROM book_authors me
1314 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '1'
1315 SELECT, author.first_name, author.last_name FROM book_authors me
1316 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '2'
1317 SELECT, author.first_name, author.last_name FROM book_authors me
1318 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '3'
1319 SELECT, author.first_name, author.last_name FROM book_authors me
1320 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '4'
1321 SELECT, author.first_name, author.last_name FROM book_authors me
1322 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '5'
c2dfb562 1323
1324Also note in C<root/src/books/list.tt2> that we are using "| html", a
1325type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1326and &gt; and avoid various types of dangerous hacks against your
1327application. In a real application, you would probably want to put
1328"| html" at the end of every field where a user has control over the
1329information that can appear in that field (and can therefore inject
1330markup or code if you don't "neutralize" those fields). In addition to
1331"| html", Template Toolkit has a variety of other useful filters that
1332can found in the documentation for
3533daff 1334
1338In some situations, it can be useful to run your application and
1339display a page without using a browser. Catalyst lets you do this
1340using the C<scripts/> script. Just supply the URL you
1341wish to display and it will run that request through the normal
1342controller dispatch logic and use the appropriate view to render the
1343output (obviously, complex pages may dump a lot of text to your
1344terminal window). For example, if you type:
1346 $ script/ "/books/list"
1348You should get the same text as if you visited
1349L<http://localhost:3000/books/list> with the normal development server
1350and asked your browser to view the page source.
3533daff 1351
1390ef0e 1352
4b4d3884 1355B<NOTE: The rest of this chapter of the tutorial is optional. You can
1356skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
3533daff 1357if you wish.>
acbd7bdd 1359
8a472b34 1360=head2 Using 'RenderView' for the Default View
1390ef0e 1361
1362Once your controller logic has processed the request from a user, it
1363forwards processing to your view in order to generate the appropriate
3533daff 1364response output. Catalyst uses
1390ef0e 1365L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
4d63a0d5 1366default to automatically perform this operation. If you look in
1390ef0e 1367C<lib/MyApp/Controller/>, you should see the empty
3533daff 1368definition for the C<sub end> method:
1370 sub end : ActionClass('RenderView') {}
1390ef0e 1372The following bullet points provide a quick overview of the
3533daff 1373C<RenderView> process:
1375=over 4
1377=item *
1379C<> is designed to hold application-wide logic.
1381=item *
1390ef0e 1383At the end of a given user request, Catalyst will call the most specific
1384C<end> method that's appropriate. For example, if the controller for a
1385request has an C<end> method defined, it will be called. However, if
1386the controller does not define a controller-specific C<end> method, the
3533daff 1387"global" C<end> method in C<> will be called.
1389=item *
1391Because the definition includes an C<ActionClass> attribute, the
1392L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1393will be executed B<after> any code inside the definition of C<sub end>
1394is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1395for more information on C<ActionClass>.
1397=item *
1390ef0e 1399Because C<sub end> is empty, this effectively just runs the default
1400logic in C<RenderView>. However, you can easily extend the
1401C<RenderView> logic by adding your own code inside the empty method body
1402(C<{}>) created by the Catalyst Helpers when we first ran the
1403C<> to initialize our application. See
1404L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
4d63a0d5 1405detailed information on how to extend C<RenderView> in C<sub end>.
3533daff 1406
1410=head2 Using The Default Template Name
1390ef0e 1412By default, C<Catalyst::View::TT> will look for a template that uses the
1413same name as your controller action, allowing you to save the step of
1414manually specifying the template name in each action. For example, this
1415would allow us to remove the
1416C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1417C<list> action in the Books controller. Open
3533daff 1418C<lib/MyApp/Controller/> in your editor and comment out this line
1419to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1420has changed):
1422 =head2 list
1424 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1426 =cut
1428 sub list : Local {
1429 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1430 # 'Context' that's used to 'glue together' the various components
1431 # that make up the application
1432 my ($self, $c) = @_;
1434 # Retrieve all of the book records as book model objects and store in the
1435 # stash where they can be accessed by the TT template
d0496197 1436 $c->stash->{books} = [$c->model('DB::Books')->all];
3533daff 1437
1438 # Set the TT template to use. You will almost always want to do this
1439 # in your action methods (actions methods respond to user input in
1440 # your controllers).
1441 #$c->stash->{template} = 'books/list.tt2';
1442 }
3533daff 1444
1390ef0e 1445You should now be able to restart the development server as per the
3533daff 1446previous section and access the L<http://localhost:3000/books/list>
1447as before.
1449B<NOTE:> Please note that if you use the default template technique,
1450you will B<not> be able to use either the C<$c-E<gt>forward> or
4b4d3884 1451the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1452Chapter 9 of the Tutorial).
3533daff 1453
4d63a0d5 1455=head2 Return To A Manually Specified Template
3533daff 1456
1457In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1458later in the tutorial, you should remove the comment from the
1459statement in C<sub list> in C<lib/MyApp/Controller/>:
1461 $c->stash->{template} = 'books/list.tt2';
1390ef0e 1463Then delete the C<TEMPLATE_EXTENSION> line in
3533daff 1464C<lib/MyApp/View/>.
1390ef0e 1466You should then be able to restart the development server and
3533daff 1467access L<http://localhost:3000/books/list> in the same manner as
1468with earlier sections.
1471=head1 AUTHOR
1473Kennedy Clark, C<>
1475Please report any errors, issues or suggestions to the author. The
1476most recent version of the Catalyst Tutorial can be found at
82ab4bbf 1477L<>.
3533daff 1478
45c7830f 1479Copyright 2006-2008, Kennedy Clark, under Creative Commons License
8482d557 1480(L<>).