light edits, mostly typo-like
[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
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
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 *
176C<Static::Simple> provides an easy method of serving static content such
177as images and CSS files under the development server.
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
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/ 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
245b41d1 301optional... you will see attributes written both ways). Most Catalyst
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
309an action, but you do not want Catalyst to directly expose the action
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
347how many arguments an action should except. See
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.
369It allows a series of controller methods to automatically be dispatched
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
4b4d3884 384As mentioned in Chapter 2 of the tutorial, views are where you render
1390ef0e 385output, typically for display in the user's web browser (but also
386possibly using other display output-generation systems). The code in
387C<lib/MyApp/View> selects the I<type> of view to use, with the actual
388rendering template found in the C<root> directory. As with virtually
389every aspect of Catalyst, options abound when it comes to the specific
390view technology you adopt inside your application. However, most
391Catalyst applications use the Template Toolkit, known as TT (for more
392information on TT, see L<>). Other
393somewhat popular view technologies include Mason
394(L<> and L<>) and
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
423deprecated and to be considered historical. For most Catalyst
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>
502 </tr>
503 [% END -%]
504 </table>
506As indicated by the inline comments above, the C<META title> line uses
1390ef0e 507TT's META feature to provide a title to the "wrapper" that we will
508create later. Meanwhile, the C<FOREACH> loop iterates through each
509C<book> model object and prints the C<title> and C<rating> fields.
3533daff 510
511If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT
512code. TT supports a wide variety of directives for "calling" other
513files, looping, conditional logic, etc. In general, TT simplifies the
514usual range of Perl operators down to the single dot (C<.>) operator.
515This applies to operations as diverse as method calls, hash lookups, and
516list index values (see
55beb65d 517L<>
3533daff 518for details and examples). In addition to the usual C<Template> module
519Pod documentation, you can access the TT manual at
55beb65d 520L<>.
3533daff 521
1390ef0e 522B<TIP:> While you can build all sorts of complex logic into your TT
523templates, you should in general keep the "code" part of your templates
524as simple as possible. If you need more complex logic, create helper
525methods in your model that abstract out a set of code into a single call
526from your TT template. (Note that the same is true of your controller
527logic as well -- complex sections of code in your controllers should
528often be pulled out and placed into your model objects.)
531=head2 Test Run The Application
533To test your work so far, first start the development server:
535 $ script/
537Then point your browser to L<http://localhost:3000> and you should
538still get the Catalyst welcome page. Next, change the URL in your
539browser to L<http://localhost:3000/books/list>. If you have
540everything working so far, you should see a web page that displays
541nothing other than our column headers for "Title", "Rating", and
542"Author(s)" -- we will not see any books until we get the database and
543model working below.
545If you run into problems getting your application to run correctly, it
546might be helpful to refer to some of the debugging techniques covered in
547the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the
3533daff 549
553In this step, we make a text file with the required SQL commands to
1390ef0e 554create a database table and load some sample data. We will use SQLite,
555a popular database that is lightweight and easy to use. Open
556C<myapp01.sql> in your editor and enter:
3533daff 557
558 --
559 -- Create a very simple database to hold book and author information
560 --
561 CREATE TABLE books (
563 title TEXT ,
564 rating INTEGER
565 );
566 -- 'book_authors' is a many-to-many join table between books & authors
567 CREATE TABLE book_authors (
568 book_id INTEGER,
569 author_id INTEGER,
570 PRIMARY KEY (book_id, author_id)
571 );
572 CREATE TABLE authors (
574 first_name TEXT,
575 last_name TEXT
576 );
577 ---
578 --- Load some sample data
579 ---
580 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
581 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
582 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
583 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
584 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
585 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
586 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
587 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
588 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
589 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
590 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
591 INSERT INTO authors VALUES (7, 'Nathan', 'Torkington');
592 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
593 INSERT INTO book_authors VALUES (1, 1);
594 INSERT INTO book_authors VALUES (1, 2);
595 INSERT INTO book_authors VALUES (1, 3);
596 INSERT INTO book_authors VALUES (2, 4);
597 INSERT INTO book_authors VALUES (3, 5);
598 INSERT INTO book_authors VALUES (4, 6);
599 INSERT INTO book_authors VALUES (4, 7);
600 INSERT INTO book_authors VALUES (5, 8);
3533daff 602Then use the following command to build a C<myapp.db> SQLite database:
604 $ sqlite3 myapp.db < myapp01.sql
606If you need to create the database more than once, you probably want to
607issue the C<rm myapp.db> command to delete the database before you use
1390ef0e 608the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
3533daff 609
610Once the C<myapp.db> database file has been created and initialized, you
611can use the SQLite command line environment to do a quick dump of the
612database contents:
614 $ sqlite3 myapp.db
acbd7bdd 615 SQLite version 3.5.9
3533daff 616 Enter ".help" for instructions
617 sqlite> select * from books;
618 1|CCSP SNRS Exam Certification Guide|5
619 2|TCP/IP Illustrated, Volume 1|5
620 3|Internetworking with TCP/IP Vol.1|4
621 4|Perl Cookbook|5
622 5|Designing with Web Standards|5
623 sqlite> .q
624 $
628 $ sqlite3 myapp.db "select * from books"
629 1|CCSP SNRS Exam Certification Guide|5
630 2|TCP/IP Illustrated, Volume 1|5
631 3|Internetworking with TCP/IP Vol.1|4
632 4|Perl Cookbook|5
633 5|Designing with Web Standards|5
635As with most other SQL tools, if you are using the full "interactive"
636environment you need to terminate your SQL commands with a ";" (it's not
637required if you do a single SQL statement on the command line). Use
638".q" to exit from SQLite from the SQLite interactive mode and return to
639your OS command prompt.
a6d800ac 641For using other databases, such as PostgreSQL or MySQL, see
642L<Appendix 2|Catalyst::Manual::Tutorial::Appendices>.
3533daff 643
acbd7bdd 644
8a472b34 645=head1 DATABASE ACCESS WITH DBIx::Class
3533daff 646
191dee29 647Catalyst can be used with virtually any form of persistent datastore
648available via Perl. For example,
649L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to easily
650access databases through the traditional Perl C<DBI> interface. However,
651most Catalyst applications use some form of ORM technology to
652automatically create and save model objects as they are used. Although
653L<Class::DBI|Class::DBI> has been a popular choice in the past, Matt
654Trout's L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly
655emerged as the Perl-based ORM technology of choice. Most new Catalyst
656applications rely on DBIC, as will this tutorial.
3533daff 657
3533daff 658
1390ef0e 659=head2 Create a Dynamic DBIC Model
661Use the C<create=dynamic> model helper option to build a model that
3533daff 662dynamically reads your database structure every time the application
4ab6212d 665 $ script/ model DB DBIC::Schema MyApp::Schema \
666 create=dynamic dbi:SQLite:myapp.db
1390ef0e 667 exists "/home/me/MyApp/script/../lib/MyApp/Model"
668 exists "/home/me/MyApp/script/../t"
669 exists "/home/me/MyApp/script/../lib/MyApp"
670 created "/home/me/MyApp/script/../lib/MyApp/"
671 created "/home/me/MyApp/script/../lib/MyApp/Model/"
672 created "/home/me/MyApp/script/../t/model_DB.t"
3533daff 673
1435672d 675The C<script/> command breaks down like this:
677=over 4
679=item *
d0496197 681C<DB> is the name of the model class to be created by the helper in
1435672d 682C<lib/MyApp/Model>.
684=item *
686C<DBIC::Schema> is the type of the model to create.
688=item *
690C<MyApp::Schema> is the name of the DBIC schema file written to
693=item *
695Because we specified C<create=dynamic> to the helper, it use
1390ef0e 696L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
697dynamically load the schema information from the database every time
1435672d 698the application starts.
700=item *
702And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
703for use with SQLite.
3533daff 706
d0496197 707B<NOTE:> Although the C<create=dynamic> option to the DBIC helper
19c49089 708makes for a nifty demonstration, is only really suitable for very
709small applications. After this demonstration, you should almost always
710use the C<create=static> option that we switch to below.
dc9a0503 711
acbd7bdd 715Open C<lib/MyApp/Controller/> and un-comment the model code we
716left disabled earlier so that your version matches the following (un-
717comment the line containing C<[$c-E<gt>model('DB::Books')-E<gt>all]>
718and delete the next 2 lines):
1390ef0e 719
720 =head2 list
722 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
724 =cut
726 sub list : Local {
727 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
728 # 'Context' that's used to 'glue together' the various components
729 # that make up the application
730 my ($self, $c) = @_;
732 # Retrieve all of the book records as book model objects and store in the
733 # stash where they can be accessed by the TT template
734 $c->stash->{books} = [$c->model('DB::Books')->all];
736 # Set the TT template to use. You will almost always want to do this
737 # in your action methods (action methods respond to user input in
738 # your controllers).
739 $c->stash->{template} = 'books/list.tt2';
740 }
1435672d 742B<TIP>: You may see the C<$c-E<gt>model('DB::Books')> un-commented
743above written as C<$c-E<gt>model('DB')-E<gt>resultset('Books')>. The
c93b5eaa 744two are equivalent. Either way, C<$c-E<gt>model> returns a
745L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
746against the database and iterating over the set of results that are
749We are using the C<-E<gt>all> to fetch all of the books. DBIC
750supports a wide variety of more advanced operations to easily do
751things like filtering and sorting the results. For example, the
518f3851 752following could be used to sort the results by descending title:
c93b5eaa 753
754 $c->model('DB::Books')->search({}, {order_by => 'title DESC'});
756Some other examples are provided in
757L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
758additional information found at L<DBIx::Class::ResultSet/search>,
761and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
1390ef0e 762
764=head2 Test Run The Application
3533daff 765
1435672d 766First, let's enable an environment variable that causes DBIx::Class to
acbd7bdd 767dump the SQL statements used to access the database. This is a
1435672d 768helpful trick when you are trying to debug your database-oriented
3533daff 770
771 $ export DBIC_TRACE=1
773This assumes you are using BASH as your shell -- adjust accordingly if
774you are using a different shell (for example, under tcsh, use
775C<setenv DBIC_TRACE 1>).
d0496197 777B<NOTE:> You can also set this in your code using
3533daff 778C<$class-E<gt>storage-E<gt>debug(1);>. See
779L<DBIx::Class::Manual::Troubleshooting> for details (including options
780to log to file instead of displaying to the Catalyst development server
1390ef0e 783Then launch the Catalyst development server. The log output should
784display something like:
3533daff 785
acbd7bdd 786 $ script/
3533daff 787 [debug] Debug messages enabled
1390ef0e 788 [debug] Statistics enabled
3533daff 789 [debug] Loaded plugins:
790 .----------------------------------------------------------------------------.
1390ef0e 791 | Catalyst::Plugin::ConfigLoader 0.20 |
792 | Catalyst::Plugin::StackTrace 0.08 |
3533daff 793 | Catalyst::Plugin::Static::Simple 0.20 |
794 '----------------------------------------------------------------------------'
796 [debug] Loaded dispatcher "Catalyst::Dispatcher"
797 [debug] Loaded engine "Catalyst::Engine::HTTP"
798 [debug] Found home "/home/me/MyApp"
45d511e0 799 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
3533daff 800 [debug] Loaded components:
801 .-----------------------------------------------------------------+----------.
802 | Class | Type |
803 +-----------------------------------------------------------------+----------+
804 | MyApp::Controller::Books | instance |
805 | MyApp::Controller::Root | instance |
d0496197 806 | MyApp::Model::DB | instance |
807 | MyApp::Model::DB::Authors | class |
808 | MyApp::Model::DB::BookAuthors | class |
809 | MyApp::Model::DB::Books | class |
3533daff 810 | MyApp::View::TT | instance |
811 '-----------------------------------------------------------------+----------'
813 [debug] Loaded Private actions:
814 .----------------------+--------------------------------------+--------------.
815 | Private | Class | Method |
816 +----------------------+--------------------------------------+--------------+
817 | /default | MyApp::Controller::Root | default |
818 | /end | MyApp::Controller::Root | end |
1390ef0e 819 | /index | MyApp::Controller::Root | index |
3533daff 820 | /books/index | MyApp::Controller::Books | index |
821 | /books/list | MyApp::Controller::Books | list |
822 '----------------------+--------------------------------------+--------------'
824 [debug] Loaded Path actions:
825 .-------------------------------------+--------------------------------------.
826 | Path | Private |
827 +-------------------------------------+--------------------------------------+
1390ef0e 828 | / | /default |
829 | / | /index |
830 | /books | /books/index |
3533daff 831 | /books/list | /books/list |
832 '-------------------------------------+--------------------------------------'
acbd7bdd 834 [info] MyApp powered by Catalyst 5.71000
835 You can connect to your server at http://debian:3000
3533daff 836
1390ef0e 837B<NOTE:> Be sure you run the C<script/> command from
838the 'base' directory of your application, not inside the C<script>
839directory itself or it will not be able to locate the C<myapp.db>
840database file. You can use a fully qualified or a relative path to
841locate the database file, but we did not specify that when we ran the
3533daff 842model helper earlier.
844Some things you should note in the output above:
846=over 4
1390ef0e 848=item *
3533daff 849
1390ef0e 850Catalyst::Model::DBIC::Schema dynamically created three model classes,
851one to represent each of the three tables in our database
d0496197 852(C<MyApp::Model::DB::Authors>, C<MyApp::Model::DB::BookAuthors>,
853and C<MyApp::Model::DB::Books>).
3533daff 854
1390ef0e 855=item *
3533daff 856
857The "list" action in our Books controller showed up with a path of
862Point your browser to L<http://localhost:3000> and you should still get
863the Catalyst welcome page.
865Next, to view the book list, change the URL in your browser to
866L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 867books loaded by the C<myapp01.sql> script above without any formatting.
868The rating for each book should appear on each row, but the "Author(s)"
191dee29 869column will still be blank (we will fill that in later).
3533daff 870
871Also notice in the output of the C<script/> that DBIC
872used the following SQL to retrieve the data:
874 SELECT, me.title, me.rating FROM books me
876because we enabled DBIC_TRACE.
0c51850e 878You now have the beginnings of a simple but workable web application.
3533daff 879Continue on to future sections and we will develop the application
880more fully.
1390ef0e 883=head1 CREATE A WRAPPER FOR THE VIEW
acbd7bdd 885When using TT, you can (and should) create a wrapper that will
1390ef0e 886literally wrap content around each of your templates. This is
887certainly useful as you have one main source for changing things that
888will appear across your entire site/application instead of having to
889edit many individual files.
892=head2 Configure For The Wrapper
894In order to create a wrapper, you must first edit your TT view and
895tell it where to find your wrapper file. Your TT view is located in
898Edit C<lib/MyApp/View/> and change it to match the following:
900 __PACKAGE__->config(
901 # Change default TT extension
903 # Set the location for TT files
c2dfb562 905 MyApp->path_to( 'root', 'src' ),
1390ef0e 906 ],
907 # Set to 1 for detailed timer stats in your HTML as comments
908 TIMER => 0,
909 # This is your wrapper template located in the 'root/src'
910 WRAPPER => 'wrapper.tt2',
911 );
914=head2 Create the Wrapper Template File and Stylesheet
916Next you need to set up your wrapper template. Basically, you'll want
917to take the overall layout of your site and put it into this file.
918For the tutorial, open C<root/src/wrapper.tt2> and input the following:
920 <?xml version="1.0" encoding="UTF-8"?>
921 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "">
922 <html xmlns="" xml:lang="en" lang="en">
923 <head>
924 <title>[% template.title or "My Catalyst App!" %]</title>
925 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
926 </head>
928 <body>
929 <div id="outer">
930 <div id="header">
931 [%# Your logo could go here -%]
932 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
933 [%# Insert the page title -%]
934 <h1>[% template.title or site.title %]</h1>
935 </div>
937 <div id="bodyblock">
938 <div id="menu">
939 Navigation:
940 <ul>
941 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
942 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1390ef0e 943 </ul>
944 </div><!-- end menu -->
946 <div id="content">
947 [%# Status and error messages %]
948 <span class="message">[% status_msg %]</span>
949 <span class="error">[% error_msg %]</span>
950 [%# This is where TT will stick all of your template's contents. -%]
951 [% content %]
952 </div><!-- end content -->
953 </div><!-- end bodyblock -->
955 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 956 </div><!-- end outer -->
1390ef0e 957
958 </body>
959 </html>
961Notice the status and error message sections in the code above:
963 <span class="status">[% status_msg %]</span>
964 <span class="error">[% error_msg %]</span>
966If we set either message in the Catalyst stash (e.g.,
967C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
968will be displayed whenever any view used by that request is rendered.
969The C<message> and C<error> CSS styles can be customized to suit your
970needs in the C<root/static/css/main.css> file we create below.
974=over 4
976=item *
978The Catalyst stash only lasts for a single HTTP request. If
979you need to retain information across requests you can use
980L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
4b4d3884 981Catalyst sessions in the Authentication chapter of the tutorial).
1390ef0e 982
983=item *
985Although it is beyond the scope of this tutorial, you may wish to use
986a JavaScript or AJAX tool such as jQuery (L<>) or
987Dojo (L<>).
992=head3 Create A Basic Stylesheet
994First create a central location for stylesheets under the static
997 $ mkdir root/static/css
999Then open the file C<root/static/css/main.css> (the file referenced in
1000the stylesheet href link of our wrapper above) and add the following
1003 #header {
1004 text-align: center;
1005 }
1006 #header h1 {
1007 margin: 0;
1008 }
1009 #header img {
1010 float: right;
1011 }
1012 #footer {
1013 text-align: center;
1014 font-style: italic;
1015 padding-top: 20px;
1016 }
1017 #menu {
1018 font-weight: bold;
1019 background-color: #ddd;
1020 }
1021 #menu ul {
1022 list-style: none;
1023 float: left;
1024 margin: 0;
1025 padding: 0 0 50% 5px;
1026 font-weight: normal;
1027 background-color: #ddd;
1028 width: 100px;
1029 }
1030 #content {
1031 margin-left: 120px;
1032 }
1033 .message {
1034 color: #390;
1035 }
1036 .error {
1037 color: #f00;
1038 }
1040You may wish to check out a "CSS Framework" like Emastic
1041(L<>) as a way to quickly
1042provide lots of high-quality CSS functionality.
1045=head2 Test Run The Application
1047Restart the development server and hit "Reload" in your web browser
1048and you should now see a formatted version of our basic book list.
1049Although our wrapper and stylesheet are obviously very simple, you
1050should see how it allows us to control the overall look of an entire
1051website from two central files. To add new pages to the site, just
1052provide a template that fills in the C<content> section of our wrapper
1053template -- the wrapper will provide the overall feel of the page.
8a472b34 1056=head1 A STATIC DATABASE MODEL WITH DBIx::Class
3533daff 1057
4ab6212d 1058First, let's be sure we have a recent versino of the DBIC helper,
1059L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
1060running this command:
1062 $ perl -MCatalyst::Model::DBIC::Schema -e \
1063 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
1064 0.23
1066If you don't have version 0.23 or higher, please run this command
1067to install it directly from CPAN:
1069 $ sudo cpan Catalyst::Model::DBIC::Schema
1071And re-run the version print command to verify that you are now at
10720.23 or higher.
3533daff 1075=head2 Create Static DBIC Schema Files
1390ef0e 1077Unlike the previous DBIC section where we had C<create=dynamic>
1078automatically discover the structure of the database every time the
1079application started, here we will use static schema files for more
1080control. This is typical of most "real world" applications.
3533daff 1081
1390ef0e 1082One option would be to manually create a separate schema file for each
1083table in the database, however, lets use the same
1084L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> used
1085earlier with C<create=dynamic> to build the static files for us.
9ad715b3 1086First, lets remove the schema file created earlier:
3533daff 1087
1390ef0e 1088 $ rm lib/MyApp/
3533daff 1089
1090Now regenerate the schema using the C<create=static> option:
4ab6212d 1092 $ script/ model DB DBIC::Schema MyApp::Schema \
1093 create=static components=TimeStamp dbi:SQLite:myapp.db
acbd7bdd 1094 exists "/home/me/MyApp/script/../lib/MyApp/Model"
1095 exists "/home/me/MyApp/script/../t"
1096 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
3533daff 1097 Schema dump completed.
acbd7bdd 1098 exists "/home/me/MyApp/script/../lib/MyApp/Model/"
3533daff 1099
1390ef0e 1100We could have also deleted C<lib/MyApp/Model/>, but it would
3533daff 1101have regenerated the same file (note the C<exists> in the output above).
d0496197 1102If you take a look at C<lib/MyApp/Model/>, it simply contains
1103a reference to the actual schema file in C<lib/MyApp/>
3533daff 1104along with the database connect string.
1390ef0e 1106If you look in the C<lib/MyApp/> file, you will find that it
1107is no longer using
1108L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> as its base
1109class (L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> is
1110only being used by the helper to load the schema once and then create
1111the static files for us) and C<> only contains a call to the
4ab6212d 1112C<load_namespaces> method. You will also find that C<lib/MyApp>
1113contains a C<Schema> subdirectory, which then has a subdirectory
1114called "Result". This "Result" subdirectory then has files named
acbd7bdd 1115according to each of the tables in our simple database (C<>,
1116C<>, and C<>). These three files are called
1117"Result Classes" in DBIC nomenclature. Although the Result Class files
1118are named after tables in our database, the classes correspond to the
1119I<row-level data> that is returned by DBIC (more on this later,
1120especially in
1121L<Catalyst::Manual::Tutorial::BasicCRUD/EXPLORING THE POWER OF DBIC>.
1123The idea with the Result Source files created under
4ab6212d 1124C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
1125edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
1126warning. If you place all of your changes below that point in the
1127file, you can regenerate the automatically created information at the
1128top of each file should your database structure get updated.
3533daff 1129
feb4555a 1130Also note the "flow" of the model information across the various files
1131and directories. Catalyst will initially load the model from
1132C<lib/MyApp/Model/>. This file contains a reference to
1133C<lib/MyApp/>, so that file is loaded next. Finally, the
4ab6212d 1134call to C<load_namespaces> in C<> will load each of the
1135"Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
1136The final outcome is that Catalyst will dynamically create three
1137table-specific Catalyst models every time the application starts (you
1138can see these three model files listed in the debug output generated
1139when you launch the application).
1141B<NOTE:> Older versions of
1142L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
1143deprecated DBIC C<load_classes> technique instead of the newer
1144C<load_namspaces>. For new applications, please try to use
1145C<load_namespaces> since it more easily supports a very useful DBIC
1146technique called "ResultSet Classes." If you need to convert an
1147existing application from "load_classes" to "load_namespaces," you can
1148use this process to automate the migration (but first make sure you
1149have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
1151 $ # First delete the existing schema file to disable "compatibility" mode
1152 $ rm lib/MyApp/
1153 $
1154 $ # Then re-run the helper to build the files for "load_namespaces"
1155 $ script/ model DB DBIC::Schema MyApp::Schema \
1156 create=static components=TimeStamp dbi:SQLite:myapp.db
1157 $
1158 $ # Now convert the existing files over
1159 $ cd lib/MyApp/Schema
1160 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
1161 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
1162 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
1163 $ cd ../../..
1164 $
1165 $ # And finally delete the old files
1166 $ rm lib/MyApp/Schema/*.pm
feb4555a 1167
4ab6212d 1168The "C<perl -MIO::ALL ...>" script will copy all the customized
1169relationship (and other) information below "C<# DO NOT MODIFY>" line
1170from the old files in C<lib/MyApp/Schema> to the new files in
1171C<lib/MyApp/Schema/Result> (we will be starting to add some
1172"customized relationship information in the section below).
3533daff 1173
4ab6212d 1175=head2 Updating the Generated DBIC Result Class Files
3533daff 1176
acbd7bdd 1177Let's manually add some relationship information to the auto-generated
1178Result Class files. (Note: if you are using a database other than
1179SQLite, such as PostgreSQL, then the relationship could have been
1180automatically placed in the Result Class files. If so, you can skip
4ab6212d 1181this step.) First edit C<lib/MyApp/Schema/Result/> and add the
acbd7bdd 1182following text below the C<# You can replace this text...> comment:
3533daff 1183
1184 #
1185 # Set relationships:
1390ef0e 1186 #
3533daff 1187
1188 # has_many():
1189 # args:
1190 # 1) Name of relationship, DBIC will create accessor with this name
1191 # 2) Name of the model class referenced by this relationship
1435672d 1192 # 3) Column name in *foreign* table (aka, foreign key in peer table)
4ab6212d 1193 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthors', 'book_id');
3533daff 1194
1195 # many_to_many():
1196 # args:
1197 # 1) Name of relationship, DBIC will create accessor with this name
1390ef0e 1198 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1199 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1200 # You must already have the has_many() defined to use a many_to_many().
1201 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1204B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1205file. As with any Perl package, we need to end the last line with
1206a statement that evaluates to C<true>. This is customarily done with
1207C<1;> on a line by itself.
acbd7bdd 1209C<Important Note:> Although this tutorial uses plural names for both
1210the names of the SQL tables and therefore the Result Classes (after
1211all, C<Schema::Loader> automatically named the Result Classes from the
1212names of the SQL tables it found), DBIC users prefer singular names
1213for these items. B<Please try to use singular table and DBIC
1214model/Result Class names in your applications.> This tutorial will
1215migrate to singular names as soon as possible (patches welcomed).
1216B<Note that while singular is preferred for the DBIC model, plural is
1217perfectly acceptable for the names of the controller classes.> After
1218all, the C<> controller operates on multiple books.
1390ef0e 1220This code defines both a C<has_many> and a C<many_to_many> relationship.
1221The C<many_to_many> relationship is optional, but it makes it easier to
1222map a book to its collection of authors. Without it, we would have to
1223"walk" though the C<book_authors> table as in
1225(we will see examples on how to use DBIC objects in your code soon,
1226but note that because C<$book-E<gt>book_authors> can return multiple
1227authors, we have to use C<first> to display a single author).
1228C<many_to_many> allows us to use the shorter
1230Note that you cannot define a C<many_to_many> relationship without
1231also having the C<has_many> relationship in place.
3533daff 1232
4ab6212d 1233Then edit C<lib/MyApp/Schema/Result/> and add relationship
3533daff 1234information as follows (again, be careful to put in above the C<1;> but
1235below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1237 #
1238 # Set relationships:
1239 #
1241 # has_many():
1242 # args:
1243 # 1) Name of relationship, DBIC will create accessor with this name
1244 # 2) Name of the model class referenced by this relationship
1435672d 1245 # 3) Column name in *foreign* table (aka, foreign key in peer table)
4ab6212d 1246 __PACKAGE__->has_many(book_author => 'MyApp::Schema::Result::BookAuthors', 'author_id');
3533daff 1247
1248 # many_to_many():
1249 # args:
1250 # 1) Name of relationship, DBIC will create accessor with this name
1251 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1252 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1253 # You must already have the has_many() defined to use a many_to_many().
1254 __PACKAGE__->many_to_many(books => 'book_author', 'book');
1390ef0e 1256Finally, do the same for the "join table,"
4ab6212d 1257C<lib/MyApp/Schema/Result/>:
3533daff 1258
1259 #
1260 # Set relationships:
1261 #
1263 # belongs_to():
1264 # args:
1265 # 1) Name of relationship, DBIC will create accessor with this name
1266 # 2) Name of the model class referenced by this relationship
1267 # 3) Column name in *this* table
4ab6212d 1268 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Books', 'book_id');
3533daff 1269
1270 # belongs_to():
1271 # args:
1272 # 1) Name of relationship, DBIC will create accessor with this name
1273 # 2) Name of the model class referenced by this relationship
1274 # 3) Column name in *this* table
4ab6212d 1275 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Authors', 'author_id');
3533daff 1276
1390ef0e 1278=head2 Run The Application
3533daff 1279
1280Run the Catalyst "demo server" script with the C<DBIC_TRACE> option
1281(it might still be enabled from earlier in the tutorial, but here
1282is an alternate way to specify the option just in case):
1284 $ DBIC_TRACE=1 script/
1390ef0e 1286Make sure that the application loads correctly and that you see the
1287three dynamically created model class (one for each of the
4ab6212d 1288Result Classes we created).
3533daff 1289
acbd7bdd 1290Then hit the URL L<http://localhost:3000/books/list> with your browser
1291and be sure that the book list is displayed via the relationships
1292established above. You can leave the development server running for
1293the next step if you wish.
3533daff 1294
c2dfb562 1295B<Note:> You will not see the authors yet because the view does not yet
1296use the new relations. Read on to the next section where we update the
1297template to do that.
3533daff 1298
acbd7bdd 1302Let's add a new column to our book list page that takes advantage of
1303the relationship information we manually added to our schema files in
1304the previous section. Edit C<root/src/books/list.tt2> add add the
1305following code below the existing table cell that contains
1306C<book.rating> (IOW, add a new table cell below the existing two
1307C<E<lt>tdE<gt>> tags but above the closing C<E<lt>/trE<gt>> and
1308C<E<lt>/tableE<gt>> tags):
3533daff 1309
acbd7bdd 1310 ...
3533daff 1311 <td>
1312 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1313 [% # loop in 'side effect notation' to load just the last names of the -%]
a0c5188a 1314 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
3533daff 1315 [% # a value, so nothing will be printed here. But, if you have something -%]
1316 [% # in TT that does return a method and you don't want it printed, you -%]
1317 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1318 [% # call it and discard the return value. -%]
1319 [% tt_authors = [ ];
1320 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1321 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1322 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1323 ([% tt_authors.size | html %])
1324 [% # Use another TT vmethod to join & print the names & comma separators -%]
1325 [% tt_authors.join(', ') | html %]
1326 </td>
acbd7bdd 1327 ...
3533daff 1328
1390ef0e 1329Then hit "Reload" in your browser (note that you don't need to reload
3533daff 1330the development server or use the C<-r> option when updating TT
1390ef0e 1331templates) and you should now see the number of authors each book has
1332along with a comma-separated list of the authors' last names. (If you
1333didn't leave the development server running from the previous step,
1334you will obviously need to start it before you can refresh your
1335browser window.)
1337If you are still running the development server with C<DBIC_TRACE>
1338enabled, you should also now see five more C<SELECT> statements in the
1339debug output (one for each book as the authors are being retrieved by
acbd7bdd 1340DBIC):
3533daff 1341
c2dfb562 1342 SELECT, me.title, me.rating FROM books me:
acbd7bdd 1343 SELECT, author.first_name, author.last_name FROM book_authors me
1344 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '1'
1345 SELECT, author.first_name, author.last_name FROM book_authors me
1346 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '2'
1347 SELECT, author.first_name, author.last_name FROM book_authors me
1348 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '3'
1349 SELECT, author.first_name, author.last_name FROM book_authors me
1350 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '4'
1351 SELECT, author.first_name, author.last_name FROM book_authors me
1352 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '5'
c2dfb562 1353
1354Also note in C<root/src/books/list.tt2> that we are using "| html", a
1355type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1356and &gt; and avoid various types of dangerous hacks against your
1357application. In a real application, you would probably want to put
1358"| html" at the end of every field where a user has control over the
1359information that can appear in that field (and can therefore inject
1360markup or code if you don't "neutralize" those fields). In addition to
1361"| html", Template Toolkit has a variety of other useful filters that
1362can found in the documentation for
3533daff 1364
1368In some situations, it can be useful to run your application and
1369display a page without using a browser. Catalyst lets you do this
1370using the C<scripts/> script. Just supply the URL you
1371wish to display and it will run that request through the normal
1372controller dispatch logic and use the appropriate view to render the
1373output (obviously, complex pages may dump a lot of text to your
1374terminal window). For example, if you type:
1376 $ script/ "/books/list"
1378You should get the same text as if you visited
1379L<http://localhost:3000/books/list> with the normal development server
1380and asked your browser to view the page source.
3533daff 1381
1390ef0e 1382
4b4d3884 1385B<NOTE: The rest of this chapter of the tutorial is optional. You can
1386skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
3533daff 1387if you wish.>
acbd7bdd 1389
8a472b34 1390=head2 Using 'RenderView' for the Default View
1390ef0e 1391
1392Once your controller logic has processed the request from a user, it
1393forwards processing to your view in order to generate the appropriate
3533daff 1394response output. Catalyst uses
1390ef0e 1395L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1396default to automatically performs this operation. If you look in
1397C<lib/MyApp/Controller/>, you should see the empty
3533daff 1398definition for the C<sub end> method:
1400 sub end : ActionClass('RenderView') {}
1390ef0e 1402The following bullet points provide a quick overview of the
3533daff 1403C<RenderView> process:
1405=over 4
1407=item *
1409C<> is designed to hold application-wide logic.
1411=item *
1390ef0e 1413At the end of a given user request, Catalyst will call the most specific
1414C<end> method that's appropriate. For example, if the controller for a
1415request has an C<end> method defined, it will be called. However, if
1416the controller does not define a controller-specific C<end> method, the
3533daff 1417"global" C<end> method in C<> will be called.
1419=item *
1421Because the definition includes an C<ActionClass> attribute, the
1422L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1423will be executed B<after> any code inside the definition of C<sub end>
1424is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1425for more information on C<ActionClass>.
1427=item *
1390ef0e 1429Because C<sub end> is empty, this effectively just runs the default
1430logic in C<RenderView>. However, you can easily extend the
1431C<RenderView> logic by adding your own code inside the empty method body
1432(C<{}>) created by the Catalyst Helpers when we first ran the
1433C<> to initialize our application. See
1434L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
3533daff 1435detailed information on how to extended C<RenderView> in C<sub end>.
1440=head2 Using The Default Template Name
1390ef0e 1442By default, C<Catalyst::View::TT> will look for a template that uses the
1443same name as your controller action, allowing you to save the step of
1444manually specifying the template name in each action. For example, this
1445would allow us to remove the
1446C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1447C<list> action in the Books controller. Open
3533daff 1448C<lib/MyApp/Controller/> in your editor and comment out this line
1449to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1450has changed):
1452 =head2 list
1454 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1456 =cut
1458 sub list : Local {
1459 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1460 # 'Context' that's used to 'glue together' the various components
1461 # that make up the application
1462 my ($self, $c) = @_;
1464 # Retrieve all of the book records as book model objects and store in the
1465 # stash where they can be accessed by the TT template
d0496197 1466 $c->stash->{books} = [$c->model('DB::Books')->all];
3533daff 1467
1468 # Set the TT template to use. You will almost always want to do this
1469 # in your action methods (actions methods respond to user input in
1470 # your controllers).
1471 #$c->stash->{template} = 'books/list.tt2';
1472 }
3533daff 1474
1390ef0e 1475You should now be able to restart the development server as per the
3533daff 1476previous section and access the L<http://localhost:3000/books/list>
1477as before.
1479B<NOTE:> Please note that if you use the default template technique,
1480you will B<not> be able to use either the C<$c-E<gt>forward> or
4b4d3884 1481the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1482Chapter 9 of the Tutorial).
3533daff 1483
1485=head2 Return To A Manually-Specified Template
1487In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1488later in the tutorial, you should remove the comment from the
1489statement in C<sub list> in C<lib/MyApp/Controller/>:
1491 $c->stash->{template} = 'books/list.tt2';
1390ef0e 1493Then delete the C<TEMPLATE_EXTENSION> line in
3533daff 1494C<lib/MyApp/View/>.
1390ef0e 1496You should then be able to restart the development server and
3533daff 1497access L<http://localhost:3000/books/list> in the same manner as
1498with earlier sections.
1501=head1 AUTHOR
1503Kennedy Clark, C<>
1505Please report any errors, issues or suggestions to the author. The
1506most recent version of the Catalyst Tutorial can be found at
82ab4bbf 1507L<>.
3533daff 1508
45c7830f 1509Copyright 2006-2008, Kennedy Clark, under Creative Commons License
8482d557 1510(L<>).