Fix minor typo
[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
1390ef0e 74The remainder of the tutorial will build an application called C<MyApp>.
75First use the Catalyst C<> script to initialize the framework
76for the C<MyApp> application (make sure you aren't still inside the
4b4d3884 77directory of the C<Hello> application from the previous chapter of the
acbd7bdd 78tutorial or in a directory that already has a "MyApp" subdirectory):
3533daff 79
80 $ MyApp
81 created "MyApp"
82 created "MyApp/script"
83 created "MyApp/lib"
84 created "MyApp/root"
85 ...
86 created "MyApp/script/"
87 $ cd MyApp
4b4d3884 89This creates a similar skeletal structure to what we saw in Chapter 2 of
1390ef0e 90the tutorial, except with C<MyApp> and C<myapp> substituted for
3533daff 91C<Hello> and C<hello>.
96One of the greatest benefits of Catalyst is that it has such a large
1390ef0e 97library of plugins and base classes available. Plugins are used to
98seamlessly integrate existing Perl modules into the overall Catalyst
99framework. In general, they do this by adding additional methods to the
100C<context> object (generally written as C<$c>) that Catalyst passes to
101every component throughout the framework.
3533daff 102
103By default, Catalyst enables three plugins/flags:
105=over 4
1390ef0e 107=item *
3533daff 108
109C<-Debug> Flag
111Enables the Catalyst debug output you saw when we started the
112C<script/> development server earlier. You can remove
79a529cc 113this item when you place your application into production.
3533daff 114
1390ef0e 115As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
116Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
117line of your application class will be plugins, Catalyst supports a
118limited number of flag options (of these, C<-Debug> is the most
119common). See the documentation for C<> to get details on
120other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
3533daff 121
122If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
125B<TIP>: Depending on your needs, it can be helpful to permanently
126remove C<-Debug> from C<lib/> and then use the C<-d> option
127to C<script/> to re-enable it just for the development
1390ef0e 128server. We will not be using that approach in the tutorial, but feel
3533daff 129free to make use of it in your own projects.
131=item *
135C<ConfigLoader> provides an automatic way to load configurable
c010ae0d 136parameters for your application from a central
137L<Config::General|Config::General> file (versus having the values
138hard-coded inside your Perl modules). Config::General uses syntax
139very similar to Apache configuration files. We will see how to use
140this feature of Catalyst during the authentication and authorization
4b4d3884 141sections (Chapter 5 and Chapter 6).
3533daff 142
1435672d 143B<IMPORTANT NOTE:> If you are using a version of
144L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, be aware
145that Catalyst changed the default format from YAML to the more
146straightforward C<Config::General> style. This tutorial uses the
147newer C<myapp.conf> file for C<Config::General>. However, Catalyst
148supports both formats and will automatically use either C<myapp.conf>
149or C<myapp.yml> (or any other format supported by
150L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
151L<Config::Any|Config::Any>). If you are using a version of
152Catalyst::Devel prior to 1.06, you can convert to the newer format by
153simply creating the C<myapp.conf> file manually and deleting
154C<myapp.yml>. The default contents of the C<myapp.conf> you create
155should only consist of one line:
157 name MyApp
15e1d0b2 158
1390ef0e 159B<TIP>: This script can be useful for converting between configuration
15e1d0b2 160formats:
1390ef0e 162 perl -Ilib -e 'use MyApp; use Config::General;
15e1d0b2 163 Config::General->new->save_file("myapp.conf", MyApp->config);'
3533daff 165=item *
169C<Static::Simple> provides an easy method of serving static content such
170as images and CSS files under the development server.
94d8da41 174For our application, we want to add one new plugin into the mix. To
1390ef0e 175do this, edit C<lib/> (this file is generally referred to as
acbd7bdd 176your I<application class>) and delete the lines with:
3533daff 177
acbd7bdd 178 use Catalyst qw/-Debug
179 ConfigLoader
180 Static::Simple/;
3533daff 181
1390ef0e 182Then replace it with:
b411df01 183
acbd7bdd 184 # Load plugins
185 use Catalyst qw/-Debug
186 ConfigLoader
187 Static::Simple
189 StackTrace
190 /;
1390ef0e 191
94d8da41 192B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
acbd7bdd 193techniques to load these plugins/flags. For example, you might see
194the following:
94d8da41 195
acbd7bdd 196 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
94d8da41 197
198Don't let these variations confuse you -- they all accomplish the same
1390ef0e 201This tells Catalyst to start using one new plugin,
202L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
203stack trace to the standard Catalyst "debug screen" (the screen
204Catalyst sends to your browser when an error occurs). Be aware that
205L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
206browser, not in the console window from which you're running your
207application, which is where logging output usually goes.
3533daff 208
1390ef0e 209B<Notes:>
3533daff 210
211=over 4
1390ef0e 213=item *
215C<__PACKAGE__> is just a shorthand way of referencing the name of the
216package where it is used. Therefore, in C<>, C<__PACKAGE__>
217is equivalent to C<MyApp>.
3533daff 218
1390ef0e 219=item *
3533daff 220
1390ef0e 221You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
222before you put your application into production, but it can be helpful
223during development.
3533daff 224
1390ef0e 225=item *
3533daff 226
1390ef0e 227When specifying plugins on the C<__PACKAGE__-E<gt>setup> line, you can
228omit C<Catalyst::Plugin::> from the name. Additionally, you can
229spread the plugin names across multiple lines as shown here, or place
230them all on one (or more) lines as with the default configuration.
cca5cd98 231
3533daff 232=back
3533daff 234
1390ef0e 237As discussed earlier, controllers are where you write methods that
238interact with user input. Typically, controller methods respond to
3533daff 239C<GET> and C<POST> messages from the user's web browser.
241Use the Catalyst C<create> script to add a controller for book-related
244 $ script/ controller Books
245 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
246 exists "/home/me/MyApp/script/../t"
247 created "/home/me/MyApp/script/../lib/MyApp/Controller/"
248 created "/home/me/MyApp/script/../t/controller_Books.t"
4b4d3884 250Then edit C<lib/MyApp/Controller/> (as discussed in Chapter 2 of
1390ef0e 251the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
252each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
253and add the following method to the controller:
3533daff 254
255 =head2 list
257 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
259 =cut
1390ef0e 260
3533daff 261 sub list : Local {
262 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
263 # 'Context' that's used to 'glue together' the various components
264 # that make up the application
265 my ($self, $c) = @_;
267 # Retrieve all of the book records as book model objects and store in the
268 # stash where they can be accessed by the TT template
1390ef0e 269 # $c->stash->{books} = [$c->model('DB::Books')->all];
270 # But, for now, use this code until we create the model later
271 $c->stash->{books} = '';
3533daff 273 # Set the TT template to use. You will almost always want to do this
274 # in your action methods (action methods respond to user input in
275 # your controllers).
276 $c->stash->{template} = 'books/list.tt2';
277 }
1390ef0e 279B<TIP>: See Appendix 1 for tips on removing the leading spaces when
280cutting and pasting example code from POD-based documents.
3533daff 281
1390ef0e 282Programmers experienced with object-oriented Perl should recognize
283C<$self> as a reference to the object where this method was called.
284On the other hand, C<$c> will be new to many Perl programmers who have
285not used Catalyst before (it's sometimes written as C<$context>). The
286Context object is automatically passed to all Catalyst components. It
287is used to pass information between components and provide access to
288Catalyst and plugin functionality.
3533daff 289
245b41d1 290Catalyst actions are regular Perl methods, but they make use of
291attributes (the "C<: Local>" next to the "C<sub list>" in the code
0416017e 292above) to provide additional information to the Catalyst dispatcher
293logic (note that the space between the colon and the attribute name is
245b41d1 294optional... you will see attributes written both ways). Most Catalyst
295Controllers use one of five action types:
0416017e 296
297=over 4
299=item *
245b41d1 301B<:Private> -- Use C<:Private> for methods that you want to make into
302an action, but you do not want Catalyst to directly expose the action
303to your users. Catalyst will not map C<:Private> methods to a URI.
304Use them for various sorts of "special" methods (the C<begin>,
305C<auto>, etc. discussed below) or for methods you want to be able to
306C<forward> or C<detach> to. (If the method is a plain old "helper
307method" that you don't want to be an action at all, then just define
308the method without any attribute -- you can call it in your code, but
309the Catalyst dispatcher will ignore it.)
0416017e 310
245b41d1 311There are five types of "special" build-in C<:Private> actions:
312C<begin>, C<end>, C<default>, C<index>, and C<auto>.
0416017e 313
26c9cad5 314=over 4
0416017e 316=item *
318With C<begin>, C<end>, C<default>, C<index> private actions, only the
319most specific action of each type will be called. For example, if you
320define a C<begin> action in your controller it will I<override> a
321C<begin> action in your application/root controller -- I<only> the
322action in your controller will be called.
324=item *
326Unlike the other actions where only a single method is called for each
327request, I<every> auto action along the chain of namespaces will be
328called. Each C<auto> action will be called I<from the application/root
329controller down through the most specific class>.
333=item *
245b41d1 335B<:Path> -- C<:Path> actions let you map a method to an explicit URI
336path. For example, "C<:Path('list')>" in
0416017e 337C<lib/MyApp/Controller/> would match on the URL
245b41d1 338C<http://localhost:3000/books/list> but "C<:Path('/list')>" would match
339on C<http://localhost:3000/list>. You can use C<:Args()> to specify
340how many arguments an action should except. See
341L<Catalyst::Manual::Intro/Action_types> for more information and a few
0416017e 342examples.
344=item *
245b41d1 346B<:Local> -- C<:Local> is merely a shorthand for
347"C<:Path('_name_of_method_')>". For example, these are equivalent:
348"C<sub create_book :Local {...}>" and
349"C<sub create_book :Path('create_book') {...}>".
351=item *
353B<:Global> -- C<:Global> is merely a shorthand for
354"C<:Path('/_name_of_method_')>". For example, these are equivalent:
355"C<sub create_book :Global {...}>" and
356"C<sub create_book :Path('/create_book') {...}>".
358=item *
360B<:Chained> -- Newer Catalyst applications tend to use the Chained
0416017e 361dispatch form of action types because of its power and flexibility.
362It allows a series of controller methods to automatically be dispatched
363to service a single user request. See
365and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
366for more information on chained actions.
370You should refer to L<Catalyst::Manual::Intro/Action_types> for
371additional information and for coverage of some lesser-used action
245b41d1 372types not discussed here (C<Regex> and C<LocalRegex>).
3533daff 373
4b4d3884 377As mentioned in Chapter 2 of the tutorial, views are where you render
1390ef0e 378output, typically for display in the user's web browser (but also
379possibly using other display output-generation systems). The code in
380C<lib/MyApp/View> selects the I<type> of view to use, with the actual
381rendering template found in the C<root> directory. As with virtually
382every aspect of Catalyst, options abound when it comes to the specific
383view technology you adopt inside your application. However, most
384Catalyst applications use the Template Toolkit, known as TT (for more
385information on TT, see L<>). Other
386somewhat popular view technologies include Mason
387(L<> and L<>) and
388L<HTML::Template> (L<>).
391=head2 Create a Catalyst View
3533daff 392
393When using TT for the Catalyst view, there are two main helper scripts:
395=over 4
397=item *
401=item *
de966eb4 407Both helpers are similar. C<TT> creates the C<lib/MyApp/View/>
3533daff 408file and leaves the creation of any hierarchical template organization
409entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
4b4d3884 410test cases will be discussed in Chapter 8.) C<TTSite>, on the other hand,
de966eb4 411creates a modular and hierarchical view layout with
1390ef0e 412separate Template Toolkit (TT) files for common header and footer
413information, configuration values, a CSS stylesheet, and more.
de966eb4 415While C<TTSite> was useful to bootstrap a project, its use is now
416deprecated and to be considered historical. For most Catalyst
417applications it adds redundant functionality and structure; many in the
418Catalyst community recommend that it's easier to learn both Catalyst and
419Template Toolkit if you use the more basic C<TT> approach.
420Consequently, this tutorial will use "plain old TT."
1390ef0e 421
422Enter the following command to enable the C<TT> style of view
3533daff 423rendering for this tutorial:
1390ef0e 425 $ script/ view TT TT
3533daff 426 exists "/home/me/MyApp/script/../lib/MyApp/View"
427 exists "/home/me/MyApp/script/../t"
1390ef0e 428 created "/home/me/MyApp/script/../lib/MyApp/View/"
429 created "/home/me/MyApp/script/../t/view_TT.t"
3533daff 430
1390ef0e 431This simply creates a view called C<TT> (the second 'TT' argument) in
432a file called C<> (the first 'TT' argument). It is now up to you
433to decide how you want to structure your view layout. For the
434tutorial, we will start with a very simple TT template to initially
435demonstrate the concepts, but quickly migrate to a more typical
436"wrapper page" type of configuration (where the "wrapper" controls the
437overall "look and feel" of your site from a single file or set of
3533daff 439
1390ef0e 440Edit C<lib/MyApp/View/> and you should see that the default
441contents contains something similar to the following:
3533daff 442
1390ef0e 443 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
3533daff 444
1390ef0e 445And update it to match:
447 __PACKAGE__->config(
448 # Change default TT extension
450 # Set the location for TT files
6abd3023 452 MyApp->path_to( 'root', 'src' ),
1390ef0e 453 ],
454 );
3533daff 455
1390ef0e 456B<NOTE:> Make sure to add a comma after '.tt2' outside the single
191dee29 459This changes the default extension for Template Toolkit from '.tt' to
1390ef0e 460'.tt2' and changes the base directory for your template files from
de966eb4 461C<root> to C<root/src>. These changes from the default are done mostly
462to facilitate the application we're developing in this tutorial; as with
463most things Perl, there's more than one way to do it...
1390ef0e 464
acbd7bdd 465B<Note:> We will use C<root/src> as the base directory for our
466template files, which a full naming convention of
467C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
468use C<root/> as the base (with a full filename pattern of
1390ef0e 471
472=head2 Create a TT Template Page
3533daff 473
474First create a directory for book-related TT templates:
1390ef0e 476 $ mkdir -p root/src/books
3533daff 477
478Then create C<root/src/books/list.tt2> in your editor and enter:
480 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
481 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
482 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
483 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
1390ef0e 485 [% # Provide a title -%]
3533daff 486 [% META title = 'Book List' -%]
488 <table>
489 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
490 [% # Display each book in a table row %]
491 [% FOREACH book IN books -%]
492 <tr>
493 <td>[% book.title %]</td>
494 <td>[% book.rating %]</td>
495 </tr>
496 [% END -%]
497 </table>
499As indicated by the inline comments above, the C<META title> line uses
1390ef0e 500TT's META feature to provide a title to the "wrapper" that we will
501create later. Meanwhile, the C<FOREACH> loop iterates through each
502C<book> model object and prints the C<title> and C<rating> fields.
3533daff 503
504If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT
505code. TT supports a wide variety of directives for "calling" other
506files, looping, conditional logic, etc. In general, TT simplifies the
507usual range of Perl operators down to the single dot (C<.>) operator.
508This applies to operations as diverse as method calls, hash lookups, and
509list index values (see
55beb65d 510L<>
3533daff 511for details and examples). In addition to the usual C<Template> module
512Pod documentation, you can access the TT manual at
55beb65d 513L<>.
3533daff 514
1390ef0e 515B<TIP:> While you can build all sorts of complex logic into your TT
516templates, you should in general keep the "code" part of your templates
517as simple as possible. If you need more complex logic, create helper
518methods in your model that abstract out a set of code into a single call
519from your TT template. (Note that the same is true of your controller
520logic as well -- complex sections of code in your controllers should
521often be pulled out and placed into your model objects.)
524=head2 Test Run The Application
526To test your work so far, first start the development server:
528 $ script/
530Then point your browser to L<http://localhost:3000> and you should
531still get the Catalyst welcome page. Next, change the URL in your
532browser to L<http://localhost:3000/books/list>. If you have
533everything working so far, you should see a web page that displays
534nothing other than our column headers for "Title", "Rating", and
535"Author(s)" -- we will not see any books until we get the database and
536model working below.
538If you run into problems getting your application to run correctly, it
539might be helpful to refer to some of the debugging techniques covered in
540the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the
3533daff 542
546In this step, we make a text file with the required SQL commands to
1390ef0e 547create a database table and load some sample data. We will use SQLite,
548a popular database that is lightweight and easy to use. Open
549C<myapp01.sql> in your editor and enter:
3533daff 550
551 --
552 -- Create a very simple database to hold book and author information
553 --
554 CREATE TABLE books (
556 title TEXT ,
557 rating INTEGER
558 );
559 -- 'book_authors' is a many-to-many join table between books & authors
560 CREATE TABLE book_authors (
561 book_id INTEGER,
562 author_id INTEGER,
563 PRIMARY KEY (book_id, author_id)
564 );
565 CREATE TABLE authors (
567 first_name TEXT,
568 last_name TEXT
569 );
570 ---
571 --- Load some sample data
572 ---
573 INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
574 INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
575 INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
576 INSERT INTO books VALUES (4, 'Perl Cookbook', 5);
577 INSERT INTO books VALUES (5, 'Designing with Web Standards', 5);
578 INSERT INTO authors VALUES (1, 'Greg', 'Bastien');
579 INSERT INTO authors VALUES (2, 'Sara', 'Nasseh');
580 INSERT INTO authors VALUES (3, 'Christian', 'Degu');
581 INSERT INTO authors VALUES (4, 'Richard', 'Stevens');
582 INSERT INTO authors VALUES (5, 'Douglas', 'Comer');
583 INSERT INTO authors VALUES (6, 'Tom', 'Christiansen');
584 INSERT INTO authors VALUES (7, 'Nathan', 'Torkington');
585 INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman');
586 INSERT INTO book_authors VALUES (1, 1);
587 INSERT INTO book_authors VALUES (1, 2);
588 INSERT INTO book_authors VALUES (1, 3);
589 INSERT INTO book_authors VALUES (2, 4);
590 INSERT INTO book_authors VALUES (3, 5);
591 INSERT INTO book_authors VALUES (4, 6);
592 INSERT INTO book_authors VALUES (4, 7);
593 INSERT INTO book_authors VALUES (5, 8);
3533daff 595Then use the following command to build a C<myapp.db> SQLite database:
597 $ sqlite3 myapp.db < myapp01.sql
599If you need to create the database more than once, you probably want to
600issue the C<rm myapp.db> command to delete the database before you use
1390ef0e 601the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
3533daff 602
603Once the C<myapp.db> database file has been created and initialized, you
604can use the SQLite command line environment to do a quick dump of the
605database contents:
607 $ sqlite3 myapp.db
acbd7bdd 608 SQLite version 3.5.9
3533daff 609 Enter ".help" for instructions
610 sqlite> select * from books;
611 1|CCSP SNRS Exam Certification Guide|5
612 2|TCP/IP Illustrated, Volume 1|5
613 3|Internetworking with TCP/IP Vol.1|4
614 4|Perl Cookbook|5
615 5|Designing with Web Standards|5
616 sqlite> .q
617 $
621 $ sqlite3 myapp.db "select * from books"
622 1|CCSP SNRS Exam Certification Guide|5
623 2|TCP/IP Illustrated, Volume 1|5
624 3|Internetworking with TCP/IP Vol.1|4
625 4|Perl Cookbook|5
626 5|Designing with Web Standards|5
628As with most other SQL tools, if you are using the full "interactive"
629environment you need to terminate your SQL commands with a ";" (it's not
630required if you do a single SQL statement on the command line). Use
631".q" to exit from SQLite from the SQLite interactive mode and return to
632your OS command prompt.
a6d800ac 634For using other databases, such as PostgreSQL or MySQL, see
635L<Appendix 2|Catalyst::Manual::Tutorial::Appendices>.
3533daff 636
acbd7bdd 637
3533daff 638=head1 DATABASE ACCESS WITH C<DBIx::Class>
191dee29 640Catalyst can be used with virtually any form of persistent datastore
641available via Perl. For example,
642L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to easily
643access databases through the traditional Perl C<DBI> interface. However,
644most Catalyst applications use some form of ORM technology to
645automatically create and save model objects as they are used. Although
646L<Class::DBI|Class::DBI> has been a popular choice in the past, Matt
647Trout's L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly
648emerged as the Perl-based ORM technology of choice. Most new Catalyst
649applications rely on DBIC, as will this tutorial.
3533daff 650
3533daff 651
1390ef0e 652=head2 Create a Dynamic DBIC Model
654Use the C<create=dynamic> model helper option to build a model that
3533daff 655dynamically reads your database structure every time the application
4ab6212d 658 $ script/ model DB DBIC::Schema MyApp::Schema \
659 create=dynamic dbi:SQLite:myapp.db
1390ef0e 660 exists "/home/me/MyApp/script/../lib/MyApp/Model"
661 exists "/home/me/MyApp/script/../t"
662 exists "/home/me/MyApp/script/../lib/MyApp"
663 created "/home/me/MyApp/script/../lib/MyApp/"
664 created "/home/me/MyApp/script/../lib/MyApp/Model/"
665 created "/home/me/MyApp/script/../t/model_DB.t"
3533daff 666
1435672d 668The C<script/> command breaks down like this:
670=over 4
672=item *
d0496197 674C<DB> is the name of the model class to be created by the helper in
1435672d 675C<lib/MyApp/Model>.
677=item *
679C<DBIC::Schema> is the type of the model to create.
681=item *
683C<MyApp::Schema> is the name of the DBIC schema file written to
686=item *
688Because we specified C<create=dynamic> to the helper, it use
1390ef0e 689L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
690dynamically load the schema information from the database every time
1435672d 691the application starts.
693=item *
695And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
696for use with SQLite.
3533daff 699
d0496197 700B<NOTE:> Although the C<create=dynamic> option to the DBIC helper
19c49089 701makes for a nifty demonstration, is only really suitable for very
702small applications. After this demonstration, you should almost always
703use the C<create=static> option that we switch to below.
dc9a0503 704
acbd7bdd 708Open C<lib/MyApp/Controller/> and un-comment the model code we
709left disabled earlier so that your version matches the following (un-
710comment the line containing C<[$c-E<gt>model('DB::Books')-E<gt>all]>
711and delete the next 2 lines):
1390ef0e 712
713 =head2 list
715 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
717 =cut
719 sub list : Local {
720 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
721 # 'Context' that's used to 'glue together' the various components
722 # that make up the application
723 my ($self, $c) = @_;
725 # Retrieve all of the book records as book model objects and store in the
726 # stash where they can be accessed by the TT template
727 $c->stash->{books} = [$c->model('DB::Books')->all];
729 # Set the TT template to use. You will almost always want to do this
730 # in your action methods (action methods respond to user input in
731 # your controllers).
732 $c->stash->{template} = 'books/list.tt2';
733 }
1435672d 735B<TIP>: You may see the C<$c-E<gt>model('DB::Books')> un-commented
736above written as C<$c-E<gt>model('DB')-E<gt>resultset('Books')>. The
c93b5eaa 737two are equivalent. Either way, C<$c-E<gt>model> returns a
738L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
739against the database and iterating over the set of results that are
742We are using the C<-E<gt>all> to fetch all of the books. DBIC
743supports a wide variety of more advanced operations to easily do
744things like filtering and sorting the results. For example, the
518f3851 745following could be used to sort the results by descending title:
c93b5eaa 746
747 $c->model('DB::Books')->search({}, {order_by => 'title DESC'});
749Some other examples are provided in
750L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
751additional information found at L<DBIx::Class::ResultSet/search>,
754and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
1390ef0e 755
757=head2 Test Run The Application
3533daff 758
1435672d 759First, let's enable an environment variable that causes DBIx::Class to
acbd7bdd 760dump the SQL statements used to access the database. This is a
1435672d 761helpful trick when you are trying to debug your database-oriented
3533daff 763
764 $ export DBIC_TRACE=1
766This assumes you are using BASH as your shell -- adjust accordingly if
767you are using a different shell (for example, under tcsh, use
768C<setenv DBIC_TRACE 1>).
d0496197 770B<NOTE:> You can also set this in your code using
3533daff 771C<$class-E<gt>storage-E<gt>debug(1);>. See
772L<DBIx::Class::Manual::Troubleshooting> for details (including options
773to log to file instead of displaying to the Catalyst development server
1390ef0e 776Then launch the Catalyst development server. The log output should
777display something like:
3533daff 778
acbd7bdd 779 $ script/
3533daff 780 [debug] Debug messages enabled
1390ef0e 781 [debug] Statistics enabled
3533daff 782 [debug] Loaded plugins:
783 .----------------------------------------------------------------------------.
1390ef0e 784 | Catalyst::Plugin::ConfigLoader 0.20 |
785 | Catalyst::Plugin::StackTrace 0.08 |
3533daff 786 | Catalyst::Plugin::Static::Simple 0.20 |
787 '----------------------------------------------------------------------------'
789 [debug] Loaded dispatcher "Catalyst::Dispatcher"
790 [debug] Loaded engine "Catalyst::Engine::HTTP"
791 [debug] Found home "/home/me/MyApp"
45d511e0 792 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
3533daff 793 [debug] Loaded components:
794 .-----------------------------------------------------------------+----------.
795 | Class | Type |
796 +-----------------------------------------------------------------+----------+
797 | MyApp::Controller::Books | instance |
798 | MyApp::Controller::Root | instance |
d0496197 799 | MyApp::Model::DB | instance |
800 | MyApp::Model::DB::Authors | class |
801 | MyApp::Model::DB::BookAuthors | class |
802 | MyApp::Model::DB::Books | class |
3533daff 803 | MyApp::View::TT | instance |
804 '-----------------------------------------------------------------+----------'
806 [debug] Loaded Private actions:
807 .----------------------+--------------------------------------+--------------.
808 | Private | Class | Method |
809 +----------------------+--------------------------------------+--------------+
810 | /default | MyApp::Controller::Root | default |
811 | /end | MyApp::Controller::Root | end |
1390ef0e 812 | /index | MyApp::Controller::Root | index |
3533daff 813 | /books/index | MyApp::Controller::Books | index |
814 | /books/list | MyApp::Controller::Books | list |
815 '----------------------+--------------------------------------+--------------'
817 [debug] Loaded Path actions:
818 .-------------------------------------+--------------------------------------.
819 | Path | Private |
820 +-------------------------------------+--------------------------------------+
1390ef0e 821 | / | /default |
822 | / | /index |
823 | /books | /books/index |
3533daff 824 | /books/list | /books/list |
825 '-------------------------------------+--------------------------------------'
acbd7bdd 827 [info] MyApp powered by Catalyst 5.71000
828 You can connect to your server at http://debian:3000
3533daff 829
1390ef0e 830B<NOTE:> Be sure you run the C<script/> command from
831the 'base' directory of your application, not inside the C<script>
832directory itself or it will not be able to locate the C<myapp.db>
833database file. You can use a fully qualified or a relative path to
834locate the database file, but we did not specify that when we ran the
3533daff 835model helper earlier.
837Some things you should note in the output above:
839=over 4
1390ef0e 841=item *
3533daff 842
1390ef0e 843Catalyst::Model::DBIC::Schema dynamically created three model classes,
844one to represent each of the three tables in our database
d0496197 845(C<MyApp::Model::DB::Authors>, C<MyApp::Model::DB::BookAuthors>,
846and C<MyApp::Model::DB::Books>).
3533daff 847
1390ef0e 848=item *
3533daff 849
850The "list" action in our Books controller showed up with a path of
855Point your browser to L<http://localhost:3000> and you should still get
856the Catalyst welcome page.
858Next, to view the book list, change the URL in your browser to
859L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 860books loaded by the C<myapp01.sql> script above without any formatting.
861The rating for each book should appear on each row, but the "Author(s)"
191dee29 862column will still be blank (we will fill that in later).
3533daff 863
864Also notice in the output of the C<script/> that DBIC
865used the following SQL to retrieve the data:
867 SELECT, me.title, me.rating FROM books me
869because we enabled DBIC_TRACE.
0c51850e 871You now have the beginnings of a simple but workable web application.
3533daff 872Continue on to future sections and we will develop the application
873more fully.
1390ef0e 876=head1 CREATE A WRAPPER FOR THE VIEW
acbd7bdd 878When using TT, you can (and should) create a wrapper that will
1390ef0e 879literally wrap content around each of your templates. This is
880certainly useful as you have one main source for changing things that
881will appear across your entire site/application instead of having to
882edit many individual files.
885=head2 Configure For The Wrapper
887In order to create a wrapper, you must first edit your TT view and
888tell it where to find your wrapper file. Your TT view is located in
891Edit C<lib/MyApp/View/> and change it to match the following:
893 __PACKAGE__->config(
894 # Change default TT extension
896 # Set the location for TT files
c2dfb562 898 MyApp->path_to( 'root', 'src' ),
1390ef0e 899 ],
900 # Set to 1 for detailed timer stats in your HTML as comments
901 TIMER => 0,
902 # This is your wrapper template located in the 'root/src'
903 WRAPPER => 'wrapper.tt2',
904 );
907=head2 Create the Wrapper Template File and Stylesheet
909Next you need to set up your wrapper template. Basically, you'll want
910to take the overall layout of your site and put it into this file.
911For the tutorial, open C<root/src/wrapper.tt2> and input the following:
913 <?xml version="1.0" encoding="UTF-8"?>
914 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "">
915 <html xmlns="" xml:lang="en" lang="en">
916 <head>
917 <title>[% template.title or "My Catalyst App!" %]</title>
918 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
919 </head>
921 <body>
922 <div id="outer">
923 <div id="header">
924 [%# Your logo could go here -%]
925 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
926 [%# Insert the page title -%]
927 <h1>[% template.title or site.title %]</h1>
928 </div>
930 <div id="bodyblock">
931 <div id="menu">
932 Navigation:
933 <ul>
934 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
935 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1390ef0e 936 </ul>
937 </div><!-- end menu -->
939 <div id="content">
940 [%# Status and error messages %]
941 <span class="message">[% status_msg %]</span>
942 <span class="error">[% error_msg %]</span>
943 [%# This is where TT will stick all of your template's contents. -%]
944 [% content %]
945 </div><!-- end content -->
946 </div><!-- end bodyblock -->
948 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 949 </div><!-- end outer -->
1390ef0e 950
951 </body>
952 </html>
954Notice the status and error message sections in the code above:
956 <span class="status">[% status_msg %]</span>
957 <span class="error">[% error_msg %]</span>
959If we set either message in the Catalyst stash (e.g.,
960C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
961will be displayed whenever any view used by that request is rendered.
962The C<message> and C<error> CSS styles can be customized to suit your
963needs in the C<root/static/css/main.css> file we create below.
967=over 4
969=item *
971The Catalyst stash only lasts for a single HTTP request. If
972you need to retain information across requests you can use
973L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
4b4d3884 974Catalyst sessions in the Authentication chapter of the tutorial).
1390ef0e 975
976=item *
978Although it is beyond the scope of this tutorial, you may wish to use
979a JavaScript or AJAX tool such as jQuery (L<>) or
980Dojo (L<>).
985=head3 Create A Basic Stylesheet
987First create a central location for stylesheets under the static
990 $ mkdir root/static/css
992Then open the file C<root/static/css/main.css> (the file referenced in
993the stylesheet href link of our wrapper above) and add the following
996 #header {
997 text-align: center;
998 }
999 #header h1 {
1000 margin: 0;
1001 }
1002 #header img {
1003 float: right;
1004 }
1005 #footer {
1006 text-align: center;
1007 font-style: italic;
1008 padding-top: 20px;
1009 }
1010 #menu {
1011 font-weight: bold;
1012 background-color: #ddd;
1013 }
1014 #menu ul {
1015 list-style: none;
1016 float: left;
1017 margin: 0;
1018 padding: 0 0 50% 5px;
1019 font-weight: normal;
1020 background-color: #ddd;
1021 width: 100px;
1022 }
1023 #content {
1024 margin-left: 120px;
1025 }
1026 .message {
1027 color: #390;
1028 }
1029 .error {
1030 color: #f00;
1031 }
1033You may wish to check out a "CSS Framework" like Emastic
1034(L<>) as a way to quickly
1035provide lots of high-quality CSS functionality.
1038=head2 Test Run The Application
1040Restart the development server and hit "Reload" in your web browser
1041and you should now see a formatted version of our basic book list.
1042Although our wrapper and stylesheet are obviously very simple, you
1043should see how it allows us to control the overall look of an entire
1044website from two central files. To add new pages to the site, just
1045provide a template that fills in the C<content> section of our wrapper
1046template -- the wrapper will provide the overall feel of the page.
3533daff 1049=head1 A STATIC DATABASE MODEL WITH C<DBIx::Class>
4ab6212d 1051First, let's be sure we have a recent versino of the DBIC helper,
1052L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
1053running this command:
1055 $ perl -MCatalyst::Model::DBIC::Schema -e \
1056 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
1057 0.23
1059If you don't have version 0.23 or higher, please run this command
1060to install it directly from CPAN:
1062 $ sudo cpan Catalyst::Model::DBIC::Schema
1064And re-run the version print command to verify that you are now at
10650.23 or higher.
3533daff 1068=head2 Create Static DBIC Schema Files
1390ef0e 1070Unlike the previous DBIC section where we had C<create=dynamic>
1071automatically discover the structure of the database every time the
1072application started, here we will use static schema files for more
1073control. This is typical of most "real world" applications.
3533daff 1074
1390ef0e 1075One option would be to manually create a separate schema file for each
1076table in the database, however, lets use the same
1077L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> used
1078earlier with C<create=dynamic> to build the static files for us.
9ad715b3 1079First, lets remove the schema file created earlier:
3533daff 1080
1390ef0e 1081 $ rm lib/MyApp/
3533daff 1082
1083Now regenerate the schema using the C<create=static> option:
4ab6212d 1085 $ script/ model DB DBIC::Schema MyApp::Schema \
1086 create=static components=TimeStamp dbi:SQLite:myapp.db
acbd7bdd 1087 exists "/home/me/MyApp/script/../lib/MyApp/Model"
1088 exists "/home/me/MyApp/script/../t"
1089 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
3533daff 1090 Schema dump completed.
acbd7bdd 1091 exists "/home/me/MyApp/script/../lib/MyApp/Model/"
3533daff 1092
1390ef0e 1093We could have also deleted C<lib/MyApp/Model/>, but it would
3533daff 1094have regenerated the same file (note the C<exists> in the output above).
d0496197 1095If you take a look at C<lib/MyApp/Model/>, it simply contains
1096a reference to the actual schema file in C<lib/MyApp/>
3533daff 1097along with the database connect string.
1390ef0e 1099If you look in the C<lib/MyApp/> file, you will find that it
1100is no longer using
1101L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> as its base
1102class (L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> is
1103only being used by the helper to load the schema once and then create
1104the static files for us) and C<> only contains a call to the
4ab6212d 1105C<load_namespaces> method. You will also find that C<lib/MyApp>
1106contains a C<Schema> subdirectory, which then has a subdirectory
1107called "Result". This "Result" subdirectory then has files named
acbd7bdd 1108according to each of the tables in our simple database (C<>,
1109C<>, and C<>). These three files are called
1110"Result Classes" in DBIC nomenclature. Although the Result Class files
1111are named after tables in our database, the classes correspond to the
1112I<row-level data> that is returned by DBIC (more on this later,
1113especially in
1114L<Catalyst::Manual::Tutorial::BasicCRUD/EXPLORING THE POWER OF DBIC>.
1116The idea with the Result Source files created under
4ab6212d 1117C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
1118edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
1119warning. If you place all of your changes below that point in the
1120file, you can regenerate the automatically created information at the
1121top of each file should your database structure get updated.
3533daff 1122
feb4555a 1123Also note the "flow" of the model information across the various files
1124and directories. Catalyst will initially load the model from
1125C<lib/MyApp/Model/>. This file contains a reference to
1126C<lib/MyApp/>, so that file is loaded next. Finally, the
4ab6212d 1127call to C<load_namespaces> in C<> will load each of the
1128"Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
1129The final outcome is that Catalyst will dynamically create three
1130table-specific Catalyst models every time the application starts (you
1131can see these three model files listed in the debug output generated
1132when you launch the application).
1134B<NOTE:> Older versions of
1135L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
1136deprecated DBIC C<load_classes> technique instead of the newer
1137C<load_namspaces>. For new applications, please try to use
1138C<load_namespaces> since it more easily supports a very useful DBIC
1139technique called "ResultSet Classes." If you need to convert an
1140existing application from "load_classes" to "load_namespaces," you can
1141use this process to automate the migration (but first make sure you
1142have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
1144 $ # First delete the existing schema file to disable "compatibility" mode
1145 $ rm lib/MyApp/
1146 $
1147 $ # Then re-run the helper to build the files for "load_namespaces"
1148 $ script/ model DB DBIC::Schema MyApp::Schema \
1149 create=static components=TimeStamp dbi:SQLite:myapp.db
1150 $
1151 $ # Now convert the existing files over
1152 $ cd lib/MyApp/Schema
1153 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
1154 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
1155 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
1156 $ cd ../../..
1157 $
1158 $ # And finally delete the old files
1159 $ rm lib/MyApp/Schema/*.pm
feb4555a 1160
4ab6212d 1161The "C<perl -MIO::ALL ...>" script will copy all the customized
1162relationship (and other) information below "C<# DO NOT MODIFY>" line
1163from the old files in C<lib/MyApp/Schema> to the new files in
1164C<lib/MyApp/Schema/Result> (we will be starting to add some
1165"customized relationship information in the section below).
3533daff 1166
4ab6212d 1168=head2 Updating the Generated DBIC Result Class Files
3533daff 1169
acbd7bdd 1170Let's manually add some relationship information to the auto-generated
1171Result Class files. (Note: if you are using a database other than
1172SQLite, such as PostgreSQL, then the relationship could have been
1173automatically placed in the Result Class files. If so, you can skip
4ab6212d 1174this step.) First edit C<lib/MyApp/Schema/Result/> and add the
acbd7bdd 1175following text below the C<# You can replace this text...> comment:
3533daff 1176
1177 #
1178 # Set relationships:
1390ef0e 1179 #
3533daff 1180
1181 # has_many():
1182 # args:
1183 # 1) Name of relationship, DBIC will create accessor with this name
1184 # 2) Name of the model class referenced by this relationship
1435672d 1185 # 3) Column name in *foreign* table (aka, foreign key in peer table)
4ab6212d 1186 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthors', 'book_id');
3533daff 1187
1188 # many_to_many():
1189 # args:
1190 # 1) Name of relationship, DBIC will create accessor with this name
1390ef0e 1191 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1192 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1193 # You must already have the has_many() defined to use a many_to_many().
1194 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1197B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1198file. As with any Perl package, we need to end the last line with
1199a statement that evaluates to C<true>. This is customarily done with
1200C<1;> on a line by itself.
acbd7bdd 1202C<Important Note:> Although this tutorial uses plural names for both
1203the names of the SQL tables and therefore the Result Classes (after
1204all, C<Schema::Loader> automatically named the Result Classes from the
1205names of the SQL tables it found), DBIC users prefer singular names
1206for these items. B<Please try to use singular table and DBIC
1207model/Result Class names in your applications.> This tutorial will
1208migrate to singular names as soon as possible (patches welcomed).
1209B<Note that while singular is preferred for the DBIC model, plural is
1210perfectly acceptable for the names of the controller classes.> After
1211all, the C<> controller operates on multiple books.
1390ef0e 1213This code defines both a C<has_many> and a C<many_to_many> relationship.
1214The C<many_to_many> relationship is optional, but it makes it easier to
1215map a book to its collection of authors. Without it, we would have to
1216"walk" though the C<book_authors> table as in
1218(we will see examples on how to use DBIC objects in your code soon,
1219but note that because C<$book-E<gt>book_authors> can return multiple
1220authors, we have to use C<first> to display a single author).
1221C<many_to_many> allows us to use the shorter
1223Note that you cannot define a C<many_to_many> relationship without
1224also having the C<has_many> relationship in place.
3533daff 1225
4ab6212d 1226Then edit C<lib/MyApp/Schema/Result/> and add relationship
3533daff 1227information as follows (again, be careful to put in above the C<1;> but
1228below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1230 #
1231 # Set relationships:
1232 #
1234 # has_many():
1235 # args:
1236 # 1) Name of relationship, DBIC will create accessor with this name
1237 # 2) Name of the model class referenced by this relationship
1435672d 1238 # 3) Column name in *foreign* table (aka, foreign key in peer table)
4ab6212d 1239 __PACKAGE__->has_many(book_author => 'MyApp::Schema::Result::BookAuthors', 'author_id');
3533daff 1240
1241 # many_to_many():
1242 # args:
1243 # 1) Name of relationship, DBIC will create accessor with this name
1244 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1245 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1246 # You must already have the has_many() defined to use a many_to_many().
1247 __PACKAGE__->many_to_many(books => 'book_author', 'book');
1390ef0e 1249Finally, do the same for the "join table,"
4ab6212d 1250C<lib/MyApp/Schema/Result/>:
3533daff 1251
1252 #
1253 # Set relationships:
1254 #
1256 # belongs_to():
1257 # args:
1258 # 1) Name of relationship, DBIC will create accessor with this name
1259 # 2) Name of the model class referenced by this relationship
1260 # 3) Column name in *this* table
4ab6212d 1261 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Books', 'book_id');
3533daff 1262
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(author => 'MyApp::Schema::Result::Authors', 'author_id');
3533daff 1269
1390ef0e 1271=head2 Run The Application
3533daff 1272
1273Run the Catalyst "demo server" script with the C<DBIC_TRACE> option
1274(it might still be enabled from earlier in the tutorial, but here
1275is an alternate way to specify the option just in case):
1277 $ DBIC_TRACE=1 script/
1390ef0e 1279Make sure that the application loads correctly and that you see the
1280three dynamically created model class (one for each of the
4ab6212d 1281Result Classes we created).
3533daff 1282
acbd7bdd 1283Then hit the URL L<http://localhost:3000/books/list> with your browser
1284and be sure that the book list is displayed via the relationships
1285established above. You can leave the development server running for
1286the next step if you wish.
3533daff 1287
c2dfb562 1288B<Note:> You will not see the authors yet because the view does not yet
1289use the new relations. Read on to the next section where we update the
1290template to do that.
3533daff 1291
acbd7bdd 1295Let's add a new column to our book list page that takes advantage of
1296the relationship information we manually added to our schema files in
1297the previous section. Edit C<root/src/books/list.tt2> add add the
1298following code below the existing table cell that contains
1299C<book.rating> (IOW, add a new table cell below the existing two
1300C<E<lt>tdE<gt>> tags but above the closing C<E<lt>/trE<gt>> and
1301C<E<lt>/tableE<gt>> tags):
3533daff 1302
acbd7bdd 1303 ...
3533daff 1304 <td>
1305 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1306 [% # loop in 'side effect notation' to load just the last names of the -%]
a0c5188a 1307 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
3533daff 1308 [% # a value, so nothing will be printed here. But, if you have something -%]
1309 [% # in TT that does return a method and you don't want it printed, you -%]
1310 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1311 [% # call it and discard the return value. -%]
1312 [% tt_authors = [ ];
1313 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1314 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1315 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1316 ([% tt_authors.size | html %])
1317 [% # Use another TT vmethod to join & print the names & comma separators -%]
1318 [% tt_authors.join(', ') | html %]
1319 </td>
acbd7bdd 1320 ...
3533daff 1321
1390ef0e 1322Then hit "Reload" in your browser (note that you don't need to reload
3533daff 1323the development server or use the C<-r> option when updating TT
1390ef0e 1324templates) and you should now see the number of authors each book has
1325along with a comma-separated list of the authors' last names. (If you
1326didn't leave the development server running from the previous step,
1327you will obviously need to start it before you can refresh your
1328browser window.)
1330If you are still running the development server with C<DBIC_TRACE>
1331enabled, you should also now see five more C<SELECT> statements in the
1332debug output (one for each book as the authors are being retrieved by
acbd7bdd 1333DBIC):
3533daff 1334
c2dfb562 1335 SELECT, me.title, me.rating FROM books me:
acbd7bdd 1336 SELECT, author.first_name, author.last_name FROM book_authors me
1337 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '1'
1338 SELECT, author.first_name, author.last_name FROM book_authors me
1339 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '2'
1340 SELECT, author.first_name, author.last_name FROM book_authors me
1341 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '3'
1342 SELECT, author.first_name, author.last_name FROM book_authors me
1343 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '4'
1344 SELECT, author.first_name, author.last_name FROM book_authors me
1345 JOIN authors author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '5'
c2dfb562 1346
1347Also note in C<root/src/books/list.tt2> that we are using "| html", a
1348type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1349and &gt; and avoid various types of dangerous hacks against your
1350application. In a real application, you would probably want to put
1351"| html" at the end of every field where a user has control over the
1352information that can appear in that field (and can therefore inject
1353markup or code if you don't "neutralize" those fields). In addition to
1354"| html", Template Toolkit has a variety of other useful filters that
1355can found in the documentation for
3533daff 1357
1361In some situations, it can be useful to run your application and
1362display a page without using a browser. Catalyst lets you do this
1363using the C<scripts/> script. Just supply the URL you
1364wish to display and it will run that request through the normal
1365controller dispatch logic and use the appropriate view to render the
1366output (obviously, complex pages may dump a lot of text to your
1367terminal window). For example, if you type:
1369 $ script/ "/books/list"
1371You should get the same text as if you visited
1372L<http://localhost:3000/books/list> with the normal development server
1373and asked your browser to view the page source.
3533daff 1374
1390ef0e 1375
4b4d3884 1378B<NOTE: The rest of this chapter of the tutorial is optional. You can
1379skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
3533daff 1380if you wish.>
acbd7bdd 1382
1390ef0e 1383=head2 Using C<RenderView> for the Default View
1385Once your controller logic has processed the request from a user, it
1386forwards processing to your view in order to generate the appropriate
3533daff 1387response output. Catalyst uses
1390ef0e 1388L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
1389default to automatically performs this operation. If you look in
1390C<lib/MyApp/Controller/>, you should see the empty
3533daff 1391definition for the C<sub end> method:
1393 sub end : ActionClass('RenderView') {}
1390ef0e 1395The following bullet points provide a quick overview of the
3533daff 1396C<RenderView> process:
1398=over 4
1400=item *
1402C<> is designed to hold application-wide logic.
1404=item *
1390ef0e 1406At the end of a given user request, Catalyst will call the most specific
1407C<end> method that's appropriate. For example, if the controller for a
1408request has an C<end> method defined, it will be called. However, if
1409the controller does not define a controller-specific C<end> method, the
3533daff 1410"global" C<end> method in C<> will be called.
1412=item *
1414Because the definition includes an C<ActionClass> attribute, the
1415L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1416will be executed B<after> any code inside the definition of C<sub end>
1417is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1418for more information on C<ActionClass>.
1420=item *
1390ef0e 1422Because C<sub end> is empty, this effectively just runs the default
1423logic in C<RenderView>. However, you can easily extend the
1424C<RenderView> logic by adding your own code inside the empty method body
1425(C<{}>) created by the Catalyst Helpers when we first ran the
1426C<> to initialize our application. See
1427L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
3533daff 1428detailed information on how to extended C<RenderView> in C<sub end>.
1433=head2 Using The Default Template Name
1390ef0e 1435By default, C<Catalyst::View::TT> will look for a template that uses the
1436same name as your controller action, allowing you to save the step of
1437manually specifying the template name in each action. For example, this
1438would allow us to remove the
1439C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1440C<list> action in the Books controller. Open
3533daff 1441C<lib/MyApp/Controller/> in your editor and comment out this line
1442to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1443has changed):
1445 =head2 list
1447 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1449 =cut
1451 sub list : Local {
1452 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1453 # 'Context' that's used to 'glue together' the various components
1454 # that make up the application
1455 my ($self, $c) = @_;
1457 # Retrieve all of the book records as book model objects and store in the
1458 # stash where they can be accessed by the TT template
d0496197 1459 $c->stash->{books} = [$c->model('DB::Books')->all];
3533daff 1460
1461 # Set the TT template to use. You will almost always want to do this
1462 # in your action methods (actions methods respond to user input in
1463 # your controllers).
1464 #$c->stash->{template} = 'books/list.tt2';
1465 }
3533daff 1467
1390ef0e 1468You should now be able to restart the development server as per the
3533daff 1469previous section and access the L<http://localhost:3000/books/list>
1470as before.
1472B<NOTE:> Please note that if you use the default template technique,
1473you will B<not> be able to use either the C<$c-E<gt>forward> or
4b4d3884 1474the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1475Chapter 9 of the Tutorial).
3533daff 1476
1478=head2 Return To A Manually-Specified Template
1480In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1481later in the tutorial, you should remove the comment from the
1482statement in C<sub list> in C<lib/MyApp/Controller/>:
1484 $c->stash->{template} = 'books/list.tt2';
1390ef0e 1486Then delete the C<TEMPLATE_EXTENSION> line in
3533daff 1487C<lib/MyApp/View/>.
1390ef0e 1489You should then be able to restart the development server and
3533daff 1490access L<http://localhost:3000/books/list> in the same manner as
1491with earlier sections.
1494=head1 AUTHOR
1496Kennedy Clark, C<>
1498Please report any errors, issues or suggestions to the author. The
1499most recent version of the Catalyst Tutorial can be found at
82ab4bbf 1500L<>.
3533daff 1501
45c7830f 1502Copyright 2006-2008, Kennedy Clark, under Creative Commons License
8482d557 1503(L<>).