Merge from depluralization branch
[catagits/Catalyst-Manual.git] / lib / Catalyst / Manual / Tutorial / MoreCatalystBasics.pod
3533daff 1=head1 NAME
4b4d3884 3Catalyst::Manual::Tutorial::MoreCatalystBasics - Catalyst Tutorial - Chapter 3: More Catalyst Application Development Basics
3533daff 4
6=head1 OVERVIEW
4b4d3884 8This is B<Chapter 3 of 10> for the Catalyst tutorial.
3533daff 9
10L<Tutorial Overview|Catalyst::Manual::Tutorial>
12=over 4
14=item 1
18=item 2
20L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics>
22=item 3
24B<More Catalyst Basics>
26=item 4
28L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>
30=item 5
34=item 6
38=item 7
42=item 8
46=item 9
48L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
50=item 10
4b4d3884 59This chapter of the tutorial builds on the work done in Chapter 2 to
60explore some features that are more typical of "real world" web
61applications. From this chapter of the tutorial onward, we will be
62building a simple book database application. Although the application
63will be too limited to be of use to anyone, it should provide a basic
64environment where we can explore a variety of features used in
65virtually all web applications.
3533daff 66
4d63a0d5 67You can check out the source code for this example from the Catalyst
68Subversion repository as per the instructions in
1390ef0e 69L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>.
3533daff 70
a586a09f 71Please take a look at
72L<Catalyst::Manual::Tutorial::Intro/CATALYST INSTALLATION> before
73doing the rest of this tutorial. Although the tutorial should work
74correctly under most any recent version of Perl running on any
75operating system, the tutorial has been written using Debian 5 and
76tested to be sure it runs correctly in this environment.
3533daff 78
1390ef0e 81The remainder of the tutorial will build an application called C<MyApp>.
82First use the Catalyst C<> script to initialize the framework
83for the C<MyApp> application (make sure you aren't still inside the
4b4d3884 84directory of the C<Hello> application from the previous chapter of the
acbd7bdd 85tutorial or in a directory that already has a "MyApp" subdirectory):
3533daff 86
87 $ MyApp
88 created "MyApp"
89 created "MyApp/script"
90 created "MyApp/lib"
91 created "MyApp/root"
92 ...
93 created "MyApp/script/"
94 $ cd MyApp
4b4d3884 96This creates a similar skeletal structure to what we saw in Chapter 2 of
1390ef0e 97the tutorial, except with C<MyApp> and C<myapp> substituted for
3533daff 98C<Hello> and C<hello>.
103One of the greatest benefits of Catalyst is that it has such a large
1390ef0e 104library of plugins and base classes available. Plugins are used to
105seamlessly integrate existing Perl modules into the overall Catalyst
106framework. In general, they do this by adding additional methods to the
107C<context> object (generally written as C<$c>) that Catalyst passes to
108every component throughout the framework.
3533daff 109
110By default, Catalyst enables three plugins/flags:
112=over 4
1390ef0e 114=item *
3533daff 115
116C<-Debug> Flag
118Enables the Catalyst debug output you saw when we started the
119C<script/> development server earlier. You can remove
79a529cc 120this item when you place your application into production.
3533daff 121
1390ef0e 122As you may have noticed, C<-Debug> is not a plugin, but a I<flag>.
123Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
124line of your application class will be plugins, Catalyst supports a
125limited number of flag options (of these, C<-Debug> is the most
126common). See the documentation for C<> to get details on
127other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
3533daff 128
129If you prefer, you can use the C<$c-E<gt>debug> method to enable debug
132B<TIP>: Depending on your needs, it can be helpful to permanently
133remove C<-Debug> from C<lib/> and then use the C<-d> option
134to C<script/> to re-enable it just for the development
1390ef0e 135server. We will not be using that approach in the tutorial, but feel
3533daff 136free to make use of it in your own projects.
138=item *
142C<ConfigLoader> provides an automatic way to load configurable
c010ae0d 143parameters for your application from a central
144L<Config::General|Config::General> file (versus having the values
145hard-coded inside your Perl modules). Config::General uses syntax
146very similar to Apache configuration files. We will see how to use
147this feature of Catalyst during the authentication and authorization
4b4d3884 148sections (Chapter 5 and Chapter 6).
3533daff 149
1435672d 150B<IMPORTANT NOTE:> If you are using a version of
151L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, be aware
152that Catalyst changed the default format from YAML to the more
153straightforward C<Config::General> style. This tutorial uses the
154newer C<myapp.conf> file for C<Config::General>. However, Catalyst
155supports both formats and will automatically use either C<myapp.conf>
156or C<myapp.yml> (or any other format supported by
157L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
158L<Config::Any|Config::Any>). If you are using a version of
159Catalyst::Devel prior to 1.06, you can convert to the newer format by
160simply creating the C<myapp.conf> file manually and deleting
161C<myapp.yml>. The default contents of the C<myapp.conf> you create
162should only consist of one line:
164 name MyApp
15e1d0b2 165
1390ef0e 166B<TIP>: This script can be useful for converting between configuration
15e1d0b2 167formats:
1390ef0e 169 perl -Ilib -e 'use MyApp; use Config::General;
15e1d0b2 170 Config::General->new->save_file("myapp.conf", MyApp->config);'
3533daff 172=item *
4d63a0d5 176C<Static::Simple> provides an easy way to serve static content, such
177as images and CSS files, from the development server.
3533daff 178
94d8da41 181For our application, we want to add one new plugin into the mix. To
1390ef0e 182do this, edit C<lib/> (this file is generally referred to as
acbd7bdd 183your I<application class>) and delete the lines with:
3533daff 184
acbd7bdd 185 use Catalyst qw/-Debug
186 ConfigLoader
187 Static::Simple/;
3533daff 188
1390ef0e 189Then replace it with:
b411df01 190
acbd7bdd 191 # Load plugins
192 use Catalyst qw/-Debug
3b1fa91b 193 ConfigLoader
194 Static::Simple
acbd7bdd 195
3b1fa91b 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
3b1fa91b 216Make sure that when adding new plugins that you include them as a new
217dependancies within the Makefile.PL file. For example, after adding
218the StackTrace plugin the Makefile.PL should include the following
221 requires 'Catalyst::Plugin::StackTrace';
1390ef0e 224B<Notes:>
3533daff 225
226=over 4
1390ef0e 228=item *
230C<__PACKAGE__> is just a shorthand way of referencing the name of the
231package where it is used. Therefore, in C<>, C<__PACKAGE__>
232is equivalent to C<MyApp>.
3533daff 233
1390ef0e 234=item *
3533daff 235
1390ef0e 236You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
237before you put your application into production, but it can be helpful
238during development.
3533daff 239
1390ef0e 240=item *
3533daff 241
1390ef0e 242When specifying plugins on the C<__PACKAGE__-E<gt>setup> line, you can
243omit C<Catalyst::Plugin::> from the name. Additionally, you can
244spread the plugin names across multiple lines as shown here, or place
245them all on one (or more) lines as with the default configuration.
cca5cd98 246
3533daff 247=back
3533daff 249
1390ef0e 252As discussed earlier, controllers are where you write methods that
253interact with user input. Typically, controller methods respond to
4d63a0d5 254C<GET> and C<POST> requests from the user's web browser.
3533daff 255
256Use the Catalyst C<create> script to add a controller for book-related
259 $ script/ controller Books
260 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
261 exists "/home/me/MyApp/script/../t"
262 created "/home/me/MyApp/script/../lib/MyApp/Controller/"
263 created "/home/me/MyApp/script/../t/controller_Books.t"
4b4d3884 265Then edit C<lib/MyApp/Controller/> (as discussed in Chapter 2 of
1390ef0e 266the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
267each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
268and add the following method to the controller:
3533daff 269
270 =head2 list
272 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
274 =cut
1390ef0e 275
3533daff 276 sub list : Local {
277 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
278 # 'Context' that's used to 'glue together' the various components
279 # that make up the application
280 my ($self, $c) = @_;
282 # Retrieve all of the book records as book model objects and store in the
283 # stash where they can be accessed by the TT template
3b1fa91b 284 # $c->stash->{books} = [$c->model('DB::Book')->all];
1390ef0e 285 # But, for now, use this code until we create the model later
286 $c->stash->{books} = '';
3533daff 288 # Set the TT template to use. You will almost always want to do this
289 # in your action methods (action methods respond to user input in
290 # your controllers).
291 $c->stash->{template} = 'books/list.tt2';
292 }
1390ef0e 294B<TIP>: See Appendix 1 for tips on removing the leading spaces when
295cutting and pasting example code from POD-based documents.
3533daff 296
1390ef0e 297Programmers experienced with object-oriented Perl should recognize
298C<$self> as a reference to the object where this method was called.
299On the other hand, C<$c> will be new to many Perl programmers who have
300not used Catalyst before (it's sometimes written as C<$context>). The
301Context object is automatically passed to all Catalyst components. It
302is used to pass information between components and provide access to
303Catalyst and plugin functionality.
3533daff 304
245b41d1 305Catalyst actions are regular Perl methods, but they make use of
306attributes (the "C<: Local>" next to the "C<sub list>" in the code
0416017e 307above) to provide additional information to the Catalyst dispatcher
308logic (note that the space between the colon and the attribute name is
4d63a0d5 309optional; you will see attributes written both ways). Most Catalyst
245b41d1 310Controllers use one of five action types:
0416017e 311
312=over 4
314=item *
245b41d1 316B<:Private> -- Use C<:Private> for methods that you want to make into
4d63a0d5 317an action, but you do not want Catalyst to directly expose
245b41d1 318to your users. Catalyst will not map C<:Private> methods to a URI.
319Use them for various sorts of "special" methods (the C<begin>,
320C<auto>, etc. discussed below) or for methods you want to be able to
321C<forward> or C<detach> to. (If the method is a plain old "helper
322method" that you don't want to be an action at all, then just define
323the method without any attribute -- you can call it in your code, but
324the Catalyst dispatcher will ignore it.)
0416017e 325
245b41d1 326There are five types of "special" build-in C<:Private> actions:
327C<begin>, C<end>, C<default>, C<index>, and C<auto>.
0416017e 328
26c9cad5 329=over 4
0416017e 331=item *
333With C<begin>, C<end>, C<default>, C<index> private actions, only the
334most specific action of each type will be called. For example, if you
335define a C<begin> action in your controller it will I<override> a
336C<begin> action in your application/root controller -- I<only> the
337action in your controller will be called.
339=item *
341Unlike the other actions where only a single method is called for each
342request, I<every> auto action along the chain of namespaces will be
343called. Each C<auto> action will be called I<from the application/root
344controller down through the most specific class>.
348=item *
245b41d1 350B<:Path> -- C<:Path> actions let you map a method to an explicit URI
351path. For example, "C<:Path('list')>" in
0416017e 352C<lib/MyApp/Controller/> would match on the URL
245b41d1 353C<http://localhost:3000/books/list> but "C<:Path('/list')>" would match
354on C<http://localhost:3000/list>. You can use C<:Args()> to specify
7e8cd009 355how many arguments an action should accept. See
245b41d1 356L<Catalyst::Manual::Intro/Action_types> for more information and a few
0416017e 357examples.
359=item *
245b41d1 361B<:Local> -- C<:Local> is merely a shorthand for
362"C<:Path('_name_of_method_')>". For example, these are equivalent:
363"C<sub create_book :Local {...}>" and
364"C<sub create_book :Path('create_book') {...}>".
366=item *
368B<:Global> -- C<:Global> is merely a shorthand for
369"C<:Path('/_name_of_method_')>". For example, these are equivalent:
370"C<sub create_book :Global {...}>" and
371"C<sub create_book :Path('/create_book') {...}>".
373=item *
375B<:Chained> -- Newer Catalyst applications tend to use the Chained
0416017e 376dispatch form of action types because of its power and flexibility.
4d63a0d5 377It allows a series of controller methods to be automatically dispatched
0416017e 378to service a single user request. See
380and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
381for more information on chained actions.
385You should refer to L<Catalyst::Manual::Intro/Action_types> for
386additional information and for coverage of some lesser-used action
245b41d1 387types not discussed here (C<Regex> and C<LocalRegex>).
3533daff 388
4d63a0d5 392As mentioned in Chapter 2 of the tutorial, views are where you render
393output, typically for display in the user's web browser (but also
394possibly using into output-generation systems, such as PDF or JSON).
395The code in C<lib/MyApp/View> selects the I<type> of view to use, with
396the actual rendering template found in the C<root> directory. As with
397virtually every aspect of Catalyst, options abound when it comes to the
398specific view technology you adopt inside your application. However,
399most Catalyst applications use the Template Toolkit, known as TT (for
400more information on TT, see L<>). Other
401somewhat popular view technologies include Mason
402(L<> and L<>) and
1390ef0e 403L<HTML::Template> (L<>).
406=head2 Create a Catalyst View
3533daff 407
408When using TT for the Catalyst view, there are two main helper scripts:
410=over 4
412=item *
416=item *
de966eb4 422Both helpers are similar. C<TT> creates the C<lib/MyApp/View/>
3533daff 423file and leaves the creation of any hierarchical template organization
424entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
4b4d3884 425test cases will be discussed in Chapter 8.) C<TTSite>, on the other hand,
de966eb4 426creates a modular and hierarchical view layout with
1390ef0e 427separate Template Toolkit (TT) files for common header and footer
428information, configuration values, a CSS stylesheet, and more.
de966eb4 430While C<TTSite> was useful to bootstrap a project, its use is now
4d63a0d5 431deprecated and it should be considered historical. For most Catalyst
de966eb4 432applications it adds redundant functionality and structure; many in the
433Catalyst community recommend that it's easier to learn both Catalyst and
434Template Toolkit if you use the more basic C<TT> approach.
435Consequently, this tutorial will use "plain old TT."
1390ef0e 436
437Enter the following command to enable the C<TT> style of view
3533daff 438rendering for this tutorial:
1390ef0e 440 $ script/ view TT TT
3533daff 441 exists "/home/me/MyApp/script/../lib/MyApp/View"
442 exists "/home/me/MyApp/script/../t"
1390ef0e 443 created "/home/me/MyApp/script/../lib/MyApp/View/"
444 created "/home/me/MyApp/script/../t/view_TT.t"
3533daff 445
1390ef0e 446This simply creates a view called C<TT> (the second 'TT' argument) in
447a file called C<> (the first 'TT' argument). It is now up to you
448to decide how you want to structure your view layout. For the
449tutorial, we will start with a very simple TT template to initially
450demonstrate the concepts, but quickly migrate to a more typical
451"wrapper page" type of configuration (where the "wrapper" controls the
452overall "look and feel" of your site from a single file or set of
3533daff 454
1390ef0e 455Edit C<lib/MyApp/View/> and you should see that the default
456contents contains something similar to the following:
3533daff 457
1390ef0e 458 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
3533daff 459
1390ef0e 460And update it to match:
462 __PACKAGE__->config(
463 # Change default TT extension
465 # Set the location for TT files
6abd3023 467 MyApp->path_to( 'root', 'src' ),
1390ef0e 468 ],
469 );
3533daff 470
1390ef0e 471B<NOTE:> Make sure to add a comma after '.tt2' outside the single
191dee29 474This changes the default extension for Template Toolkit from '.tt' to
1390ef0e 475'.tt2' and changes the base directory for your template files from
de966eb4 476C<root> to C<root/src>. These changes from the default are done mostly
477to facilitate the application we're developing in this tutorial; as with
478most things Perl, there's more than one way to do it...
1390ef0e 479
acbd7bdd 480B<Note:> We will use C<root/src> as the base directory for our
481template files, which a full naming convention of
482C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
483use C<root/> as the base (with a full filename pattern of
1390ef0e 486
487=head2 Create a TT Template Page
3533daff 488
489First create a directory for book-related TT templates:
1390ef0e 491 $ mkdir -p root/src/books
3533daff 492
493Then create C<root/src/books/list.tt2> in your editor and enter:
495 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
496 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
497 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
498 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
1390ef0e 500 [% # Provide a title -%]
3533daff 501 [% META title = 'Book List' -%]
503 <table>
504 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
505 [% # Display each book in a table row %]
506 [% FOREACH book IN books -%]
507 <tr>
508 <td>[% book.title %]</td>
509 <td>[% book.rating %]</td>
a46b474e 510 <td></td>
3533daff 511 </tr>
512 [% END -%]
513 </table>
515As indicated by the inline comments above, the C<META title> line uses
1390ef0e 516TT's META feature to provide a title to the "wrapper" that we will
517create later. Meanwhile, the C<FOREACH> loop iterates through each
518C<book> model object and prints the C<title> and C<rating> fields.
3533daff 519
4d63a0d5 520The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
521supports a wide variety of directives for "calling" other files,
522looping, conditional logic, etc. In general, TT simplifies the usual
523range of Perl operators down to the single dot (C<.>) operator. This
524applies to operations as diverse as method calls, hash lookups, and list
525index values (see
526L<> for
527details and examples). In addition to the usual C<Template> module Pod
528documentation, you can access the TT manual at
55beb65d 529L<>.
3533daff 530
1390ef0e 531B<TIP:> While you can build all sorts of complex logic into your TT
532templates, you should in general keep the "code" part of your templates
533as simple as possible. If you need more complex logic, create helper
534methods in your model that abstract out a set of code into a single call
535from your TT template. (Note that the same is true of your controller
536logic as well -- complex sections of code in your controllers should
537often be pulled out and placed into your model objects.)
540=head2 Test Run The Application
542To test your work so far, first start the development server:
544 $ script/
546Then point your browser to L<http://localhost:3000> and you should
547still get the Catalyst welcome page. Next, change the URL in your
548browser to L<http://localhost:3000/books/list>. If you have
549everything working so far, you should see a web page that displays
550nothing other than our column headers for "Title", "Rating", and
551"Author(s)" -- we will not see any books until we get the database and
552model working below.
554If you run into problems getting your application to run correctly, it
555might be helpful to refer to some of the debugging techniques covered in
556the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the
3533daff 558
562In this step, we make a text file with the required SQL commands to
1390ef0e 563create a database table and load some sample data. We will use SQLite,
564a popular database that is lightweight and easy to use. Open
565C<myapp01.sql> in your editor and enter:
3533daff 566
567 --
568 -- Create a very simple database to hold book and author information
569 --
3b1fa91b 570 CREATE TABLE book (
3533daff 571 id INTEGER PRIMARY KEY,
572 title TEXT ,
573 rating INTEGER
574 );
3b1fa91b 575 -- 'book_author' is a many-to-many join table between books & authors
576 CREATE TABLE book_author (
3533daff 577 book_id INTEGER,
578 author_id INTEGER,
579 PRIMARY KEY (book_id, author_id)
580 );
3b1fa91b 581 CREATE TABLE author (
3533daff 582 id INTEGER PRIMARY KEY,
583 first_name TEXT,
584 last_name TEXT
585 );
586 ---
587 --- Load some sample data
588 ---
3b1fa91b 589 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
590 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
591 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
592 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
593 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
594 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
595 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
596 INSERT INTO author VALUES (3, 'Christian', 'Degu');
597 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
598 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
599 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
600 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
601 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
602 INSERT INTO book_author VALUES (1, 1);
603 INSERT INTO book_author VALUES (1, 2);
604 INSERT INTO book_author VALUES (1, 3);
605 INSERT INTO book_author VALUES (2, 4);
606 INSERT INTO book_author VALUES (3, 5);
607 INSERT INTO book_author VALUES (4, 6);
608 INSERT INTO book_author VALUES (4, 7);
609 INSERT INTO book_author VALUES (5, 8);
3533daff 610
3533daff 611Then use the following command to build a C<myapp.db> SQLite database:
613 $ sqlite3 myapp.db < myapp01.sql
615If you need to create the database more than once, you probably want to
616issue the C<rm myapp.db> command to delete the database before you use
1390ef0e 617the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
3533daff 618
619Once the C<myapp.db> database file has been created and initialized, you
620can use the SQLite command line environment to do a quick dump of the
621database contents:
623 $ sqlite3 myapp.db
acbd7bdd 624 SQLite version 3.5.9
3533daff 625 Enter ".help" for instructions
3b1fa91b 626 sqlite> select * from book;
3533daff 627 1|CCSP SNRS Exam Certification Guide|5
628 2|TCP/IP Illustrated, Volume 1|5
629 3|Internetworking with TCP/IP Vol.1|4
630 4|Perl Cookbook|5
631 5|Designing with Web Standards|5
632 sqlite> .q
633 $
3b1fa91b 637 $ sqlite3 myapp.db "select * from book"
3533daff 638 1|CCSP SNRS Exam Certification Guide|5
639 2|TCP/IP Illustrated, Volume 1|5
640 3|Internetworking with TCP/IP Vol.1|4
641 4|Perl Cookbook|5
642 5|Designing with Web Standards|5
644As with most other SQL tools, if you are using the full "interactive"
645environment you need to terminate your SQL commands with a ";" (it's not
646required if you do a single SQL statement on the command line). Use
647".q" to exit from SQLite from the SQLite interactive mode and return to
648your OS command prompt.
3b1fa91b 650Please note that here we have chosen to use 'singular' table names. This
651is because the default inflection code for L<DBIx::Class:Schema::Loader>
652does NOT handle plurals. There has been much philosophical discussion
653on whether table names should be plural or singular. There is no one
654correct answer, as long as one makes a choice and remains consistent
655with it. If you prefer plural table names (e.g. they are easier and
656more natural to read) then you will need to pass it an inflect_map
657option. See L<DBIx::Class:Schema::Loader> for more information.
a6d800ac 659For using other databases, such as PostgreSQL or MySQL, see
660L<Appendix 2|Catalyst::Manual::Tutorial::Appendices>.
3533daff 661
acbd7bdd 662
8a472b34 663=head1 DATABASE ACCESS WITH DBIx::Class
3533daff 664
27909ed4 665Catalyst can be used with virtually any form of datastore available
666via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
667can be used to access databases through the traditional Perl C<DBI>
668interface or you can use a model to access files of any type on the
669filesystem. However, most Catalyst applications use some form of
670object-relational mapping (ORM) technology to create objects
671associated with tables in a relational database. Matt Trout's
672L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
673as the Perl-based ORM technology of choice. Most new Catalyst
a46b474e 674applications rely on DBIx::Class, as will this tutorial.
3533daff 675
a46b474e 676Although DBIx::Class has included support for a C<create=dynamic> mode
677to automatically read the database structure every time the
678application starts, it's use is no longer recommended. While it can
679make for "flashy" demos, the use of the C<create=static> mode we use
680below can be implemented just as quickly and provides many advantages
681(such as the ability to add your own methods to the overall DBIC
682framework, a technique that we see in Chapter 4).
3533daff 683
1390ef0e 684
a46b474e 685=head2 Make Sure You Have a Recent Version of the DBIx::Class Model
27909ed4 686
687First, let's be sure we have a recent version of the DBIC helper,
688L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
689running this command:
691 $ perl -MCatalyst::Model::DBIC::Schema -e \
692 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
693 0.23
3b1fa91b 695(please note that the '\' above is a line continuation marker and
696should NOT be included as part of the command)
27909ed4 698If you don't have version 0.23 or higher, please run this command
699to install it directly from CPAN:
701 $ sudo cpan Catalyst::Model::DBIC::Schema
703And re-run the version print command to verify that you are now at
7040.23 or higher.
a46b474e 707=head2 Create Static DBIx::Class Schema Files
27909ed4 708
98fd8420 709Before you continue, make sure your C<myapp.db> database file is in
710the application's topmost directory. Now use the model helper with
711the C<create=static> option to read the database with
27909ed4 712L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
713automatically build the required files for us:
3533daff 714
4ab6212d 715 $ script/ model DB DBIC::Schema MyApp::Schema \
27909ed4 716 create=static components=TimeStamp dbi:SQLite:myapp.db
1390ef0e 717 exists "/home/me/MyApp/script/../lib/MyApp/Model"
718 exists "/home/me/MyApp/script/../t"
27909ed4 719 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
720 Schema dump completed.
1390ef0e 721 created "/home/me/MyApp/script/../lib/MyApp/Model/"
722 created "/home/me/MyApp/script/../t/model_DB.t"
3533daff 723
3b1fa91b 724(please note that the '\' above is a line continuation marker and
725should NOT be included as part of the command)
27909ed4 727The C<script/> command breaks down like this:
729=over 4
731=item *
733C<DB> is the name of the model class to be created by the helper in
736=item *
738C<DBIC::Schema> is the type of the model to create.
740=item *
742C<MyApp::Schema> is the name of the DBIC schema file written to
745=item *
747C<create=static> causes
748L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
749load the schema as it runs and then write that information out
750into files.
752=item *
754C<components=TimeStamp> causes the help to include the
755L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp> DBIC component.
757=item *
759And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
760for use with SQLite.
764If you look in the C<lib/MyApp/> file, you will find that it
765only contains a call to the C<load_namespaces> method. You will also
766find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
767has a subdirectory called "Result". This "Result" subdirectory then
768has files named according to each of the tables in our simple database
3b1fa91b 769(C<>, C<>, and C<>). These three
a46b474e 770files are called "Result Classes" in DBIx::Class nomenclature. Although the
27909ed4 771Result Class files are named after tables in our database, the classes
772correspond to the I<row-level data> that is returned by DBIC (more on
773this later, especially in
774L<Catalyst::Manual::Tutorial::BasicCRUD/EXPLORING THE POWER OF DBIC>).
776The idea with the Result Source files created under
777C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
778edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
779warning. If you place all of your changes below that point in the
780file, you can regenerate the automatically created information at the
781top of each file should your database structure get updated.
783Also note the "flow" of the model information across the various files
784and directories. Catalyst will initially load the model from
785C<lib/MyApp/Model/>. This file contains a reference to
786C<lib/MyApp/>, so that file is loaded next. Finally, the
787call to C<load_namespaces> in C<> will load each of the
788"Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
789The final outcome is that Catalyst will dynamically create three
790table-specific Catalyst models every time the application starts (you
791can see these three model files listed in the debug output generated
792when you launch the application).
794B<NOTE:> Older versions of
795L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
a46b474e 796deprecated DBIx::Class C<load_classes> technique instead of the newer
27909ed4 797C<load_namspaces>. For new applications, please try to use
798C<load_namespaces> since it more easily supports a very useful DBIC
799technique called "ResultSet Classes." If you need to convert an
800existing application from "load_classes" to "load_namespaces," you can
801use this process to automate the migration (but first make sure you
802have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
804 $ # First delete the existing schema file to disable "compatibility" mode
805 $ rm lib/MyApp/
806 $
807 $ # Then re-run the helper to build the files for "load_namespaces"
808 $ script/ model DB DBIC::Schema MyApp::Schema \
809 create=static components=TimeStamp dbi:SQLite:myapp.db
810 $
3b1fa91b 811 $ # Note that the '\' above is a line continuation marker and
812 $ # should NOT be included as part of the command
814 $
27909ed4 815 $ # Now convert the existing files over
816 $ cd lib/MyApp/Schema
817 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
818 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
819 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
820 $ cd ../../..
821 $
822 $ # And finally delete the old files
823 $ rm lib/MyApp/Schema/*.pm
825The "C<perl -MIO::ALL ...>" script will copy all the customized
826relationship (and other) information below "C<# DO NOT MODIFY>" line
827from the old files in C<lib/MyApp/Schema> to the new files in
828C<lib/MyApp/Schema/Result> (we will be starting to add some
829"customized relationship information in the section below).
3533daff 830
dc9a0503 831
acbd7bdd 834Open C<lib/MyApp/Controller/> and un-comment the model code we
835left disabled earlier so that your version matches the following (un-
3b1fa91b 836comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
acbd7bdd 837and delete the next 2 lines):
1390ef0e 838
839 =head2 list
841 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
843 =cut
845 sub list : Local {
846 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
847 # 'Context' that's used to 'glue together' the various components
848 # that make up the application
849 my ($self, $c) = @_;
851 # Retrieve all of the book records as book model objects and store in the
852 # stash where they can be accessed by the TT template
3b1fa91b 853 $c->stash->{books} = [$c->model('DB::Book')->all];
1390ef0e 854
855 # Set the TT template to use. You will almost always want to do this
856 # in your action methods (action methods respond to user input in
857 # your controllers).
858 $c->stash->{template} = 'books/list.tt2';
859 }
3b1fa91b 861B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
862above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
c93b5eaa 863two are equivalent. Either way, C<$c-E<gt>model> returns a
864L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
4d63a0d5 865against the database and iterating over the set of results that is
c93b5eaa 866returned.
868We are using the C<-E<gt>all> to fetch all of the books. DBIC
869supports a wide variety of more advanced operations to easily do
870things like filtering and sorting the results. For example, the
518f3851 871following could be used to sort the results by descending title:
c93b5eaa 872
3b1fa91b 873 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
c93b5eaa 874
875Some other examples are provided in
876L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
877additional information found at L<DBIx::Class::ResultSet/search>,
880and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
1390ef0e 881
883=head2 Test Run The Application
3533daff 884
1435672d 885First, let's enable an environment variable that causes DBIx::Class to
acbd7bdd 886dump the SQL statements used to access the database. This is a
1435672d 887helpful trick when you are trying to debug your database-oriented
3533daff 889
890 $ export DBIC_TRACE=1
4d63a0d5 892This assumes you are using bash as your shell -- adjust accordingly if
3533daff 893you are using a different shell (for example, under tcsh, use
894C<setenv DBIC_TRACE 1>).
d0496197 896B<NOTE:> You can also set this in your code using
3533daff 897C<$class-E<gt>storage-E<gt>debug(1);>. See
898L<DBIx::Class::Manual::Troubleshooting> for details (including options
4d63a0d5 899to log to a file instead of displaying to the Catalyst development server
3533daff 900log).
1390ef0e 902Then launch the Catalyst development server. The log output should
903display something like:
3533daff 904
acbd7bdd 905 $ script/
3533daff 906 [debug] Debug messages enabled
1390ef0e 907 [debug] Statistics enabled
3533daff 908 [debug] Loaded plugins:
909 .----------------------------------------------------------------------------.
3b1fa91b 910 | Catalyst::Plugin::ConfigLoader 0.23 |
911 | Catalyst::Plugin::StackTrace 0.10 |
912 | Catalyst::Plugin::Static::Simple 0.21 |
3533daff 913 '----------------------------------------------------------------------------'
915 [debug] Loaded dispatcher "Catalyst::Dispatcher"
916 [debug] Loaded engine "Catalyst::Engine::HTTP"
917 [debug] Found home "/home/me/MyApp"
45d511e0 918 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
3533daff 919 [debug] Loaded components:
920 .-----------------------------------------------------------------+----------.
921 | Class | Type |
922 +-----------------------------------------------------------------+----------+
923 | MyApp::Controller::Books | instance |
924 | MyApp::Controller::Root | instance |
d0496197 925 | MyApp::Model::DB | instance |
3b1fa91b 926 | MyApp::Model::DB::Author | class |
927 | MyApp::Model::DB::Book | class |
928 | MyApp::Model::DB::BookAuthor | class |
3533daff 929 | MyApp::View::TT | instance |
930 '-----------------------------------------------------------------+----------'
932 [debug] Loaded Private actions:
933 .----------------------+--------------------------------------+--------------.
934 | Private | Class | Method |
935 +----------------------+--------------------------------------+--------------+
936 | /default | MyApp::Controller::Root | default |
937 | /end | MyApp::Controller::Root | end |
1390ef0e 938 | /index | MyApp::Controller::Root | index |
3533daff 939 | /books/index | MyApp::Controller::Books | index |
940 | /books/list | MyApp::Controller::Books | list |
941 '----------------------+--------------------------------------+--------------'
943 [debug] Loaded Path actions:
944 .-------------------------------------+--------------------------------------.
945 | Path | Private |
946 +-------------------------------------+--------------------------------------+
1390ef0e 947 | / | /default |
948 | / | /index |
949 | /books | /books/index |
3533daff 950 | /books/list | /books/list |
951 '-------------------------------------+--------------------------------------'
3b1fa91b 953 [info] MyApp powered by Catalyst 5.80003
acbd7bdd 954 You can connect to your server at http://debian:3000
3533daff 955
1390ef0e 956B<NOTE:> Be sure you run the C<script/> command from
957the 'base' directory of your application, not inside the C<script>
958directory itself or it will not be able to locate the C<myapp.db>
959database file. You can use a fully qualified or a relative path to
960locate the database file, but we did not specify that when we ran the
3533daff 961model helper earlier.
963Some things you should note in the output above:
965=over 4
1390ef0e 967=item *
3533daff 968
1390ef0e 969Catalyst::Model::DBIC::Schema dynamically created three model classes,
970one to represent each of the three tables in our database
3b1fa91b 971(C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
972and C<MyApp::Model::DB::Book>).
3533daff 973
1390ef0e 974=item *
3533daff 975
976The "list" action in our Books controller showed up with a path of
981Point your browser to L<http://localhost:3000> and you should still get
982the Catalyst welcome page.
984Next, to view the book list, change the URL in your browser to
985L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 986books loaded by the C<myapp01.sql> script above without any formatting.
987The rating for each book should appear on each row, but the "Author(s)"
191dee29 988column will still be blank (we will fill that in later).
3533daff 989
a46b474e 990Also notice in the output of the C<script/> that
991DBIx::Class used the following SQL to retrieve the data:
3533daff 992
993 SELECT, me.title, me.rating FROM books me
995because we enabled DBIC_TRACE.
0c51850e 997You now have the beginnings of a simple but workable web application.
3533daff 998Continue on to future sections and we will develop the application
999more fully.
1390ef0e 1002=head1 CREATE A WRAPPER FOR THE VIEW
acbd7bdd 1004When using TT, you can (and should) create a wrapper that will
1390ef0e 1005literally wrap content around each of your templates. This is
1006certainly useful as you have one main source for changing things that
1007will appear across your entire site/application instead of having to
1008edit many individual files.
1011=head2 Configure For The Wrapper
1013In order to create a wrapper, you must first edit your TT view and
1014tell it where to find your wrapper file. Your TT view is located in
1017Edit C<lib/MyApp/View/> and change it to match the following:
1019 __PACKAGE__->config(
1020 # Change default TT extension
1021 TEMPLATE_EXTENSION => '.tt2',
1022 # Set the location for TT files
1023 INCLUDE_PATH => [
c2dfb562 1024 MyApp->path_to( 'root', 'src' ),
1390ef0e 1025 ],
1026 # Set to 1 for detailed timer stats in your HTML as comments
1027 TIMER => 0,
1028 # This is your wrapper template located in the 'root/src'
1029 WRAPPER => 'wrapper.tt2',
1030 );
1033=head2 Create the Wrapper Template File and Stylesheet
1035Next you need to set up your wrapper template. Basically, you'll want
1036to take the overall layout of your site and put it into this file.
1037For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1039 <?xml version="1.0" encoding="UTF-8"?>
1040 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "">
1041 <html xmlns="" xml:lang="en" lang="en">
1042 <head>
1043 <title>[% template.title or "My Catalyst App!" %]</title>
1044 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1045 </head>
1047 <body>
1048 <div id="outer">
1049 <div id="header">
1050 [%# Your logo could go here -%]
1051 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1052 [%# Insert the page title -%]
1053 <h1>[% template.title or site.title %]</h1>
1054 </div>
1056 <div id="bodyblock">
1057 <div id="menu">
1058 Navigation:
1059 <ul>
1060 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1061 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1390ef0e 1062 </ul>
1063 </div><!-- end menu -->
1065 <div id="content">
1066 [%# Status and error messages %]
1067 <span class="message">[% status_msg %]</span>
1068 <span class="error">[% error_msg %]</span>
1069 [%# This is where TT will stick all of your template's contents. -%]
1070 [% content %]
1071 </div><!-- end content -->
1072 </div><!-- end bodyblock -->
1074 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 1075 </div><!-- end outer -->
1390ef0e 1076
1077 </body>
1078 </html>
1080Notice the status and error message sections in the code above:
1082 <span class="status">[% status_msg %]</span>
1083 <span class="error">[% error_msg %]</span>
1085If we set either message in the Catalyst stash (e.g.,
1086C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1087will be displayed whenever any view used by that request is rendered.
1088The C<message> and C<error> CSS styles can be customized to suit your
1089needs in the C<root/static/css/main.css> file we create below.
1093=over 4
1095=item *
1097The Catalyst stash only lasts for a single HTTP request. If
1098you need to retain information across requests you can use
1099L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
4b4d3884 1100Catalyst sessions in the Authentication chapter of the tutorial).
1390ef0e 1101
1102=item *
1104Although it is beyond the scope of this tutorial, you may wish to use
1105a JavaScript or AJAX tool such as jQuery (L<>) or
1106Dojo (L<>).
1111=head3 Create A Basic Stylesheet
1113First create a central location for stylesheets under the static
1116 $ mkdir root/static/css
1118Then open the file C<root/static/css/main.css> (the file referenced in
1119the stylesheet href link of our wrapper above) and add the following
1122 #header {
1123 text-align: center;
1124 }
1125 #header h1 {
1126 margin: 0;
1127 }
1128 #header img {
1129 float: right;
1130 }
1131 #footer {
1132 text-align: center;
1133 font-style: italic;
1134 padding-top: 20px;
1135 }
1136 #menu {
1137 font-weight: bold;
1138 background-color: #ddd;
1139 }
1140 #menu ul {
1141 list-style: none;
1142 float: left;
1143 margin: 0;
1144 padding: 0 0 50% 5px;
1145 font-weight: normal;
1146 background-color: #ddd;
1147 width: 100px;
1148 }
1149 #content {
1150 margin-left: 120px;
1151 }
1152 .message {
1153 color: #390;
1154 }
1155 .error {
1156 color: #f00;
1157 }
1159You may wish to check out a "CSS Framework" like Emastic
1160(L<>) as a way to quickly
1161provide lots of high-quality CSS functionality.
1164=head2 Test Run The Application
1166Restart the development server and hit "Reload" in your web browser
1167and you should now see a formatted version of our basic book list.
1168Although our wrapper and stylesheet are obviously very simple, you
1169should see how it allows us to control the overall look of an entire
1170website from two central files. To add new pages to the site, just
1171provide a template that fills in the C<content> section of our wrapper
1172template -- the wrapper will provide the overall feel of the page.
a46b474e 1175=head2 Updating the Generated DBIx::Class 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
3b1fa91b 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)
3b1fa91b 1193 __PACKAGE__->has_many(book_author => 'MyApp::Schema::Result::BookAuthor', '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().
3b1fa91b 1201 __PACKAGE__->many_to_many(author => 'book_author', 'author');
3533daff 1202
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.
a46b474e 1209This code defines both a C<has_many> and a C<many_to_many>
1210relationship. The C<many_to_many> relationship is optional, but it
1211makes it easier to map a book to its collection of authors. Without
3b1fa91b 1212it, we would have to "walk" though the C<book_author> table as in
1213C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
a46b474e 1214will see examples on how to use DBIx::Class objects in your code soon,
3b1fa91b 1215but note that because C<$book-E<gt>book_author> can return multiple
1390ef0e 1216authors, we have to use C<first> to display a single author).
3b1fa91b 1217C<many_to_many> allows us to use the shorter C<$book-E<gt>author-
a46b474e 1218E<gt>first-E<gt>last_name>. Note that you cannot define a
1219C<many_to_many> relationship without also having the C<has_many>
1220relationship in place.
3533daff 1221
3b1fa91b 1222Then edit C<lib/MyApp/Schema/Result/> and add relationship
3533daff 1223information as follows (again, be careful to put in above the C<1;> but
1224below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1226 #
1227 # Set relationships:
1228 #
1230 # has_many():
1231 # args:
4d63a0d5 1232 # 1) Name of relationship, DBIC will create an accessor with this name
3533daff 1233 # 2) Name of the model class referenced by this relationship
1435672d 1234 # 3) Column name in *foreign* table (aka, foreign key in peer table)
3b1fa91b 1235 __PACKAGE__->has_many(book_author => 'MyApp::Schema::Result::BookAuthor', 'author_id');
3533daff 1236
1237 # many_to_many():
1238 # args:
1239 # 1) Name of relationship, DBIC will create accessor with this name
1240 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1241 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1242 # You must already have the has_many() defined to use a many_to_many().
3b1fa91b 1243 __PACKAGE__->many_to_many(book => 'book_author', 'book');
3533daff 1244
1390ef0e 1245Finally, do the same for the "join table,"
3b1fa91b 1246C<lib/MyApp/Schema/Result/>:
3533daff 1247
1248 #
1249 # Set relationships:
1250 #
1252 # belongs_to():
1253 # args:
1254 # 1) Name of relationship, DBIC will create accessor with this name
1255 # 2) Name of the model class referenced by this relationship
1256 # 3) Column name in *this* table
3b1fa91b 1257 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Book', 'book_id');
3533daff 1258
1259 # belongs_to():
1260 # args:
1261 # 1) Name of relationship, DBIC will create accessor with this name
1262 # 2) Name of the model class referenced by this relationship
1263 # 3) Column name in *this* table
3b1fa91b 1264 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Author', 'author_id');
3533daff 1265
1390ef0e 1267=head2 Run The Application
3533daff 1268
4d63a0d5 1269Run the Catalyst development server script with the C<DBIC_TRACE> option
1270(it might still be enabled from earlier in the tutorial, but here is an
1271alternate way to specify the option just in case):
3533daff 1272
1273 $ DBIC_TRACE=1 script/
1390ef0e 1275Make sure that the application loads correctly and that you see the
1276three dynamically created model class (one for each of the
4ab6212d 1277Result Classes we created).
3533daff 1278
acbd7bdd 1279Then hit the URL L<http://localhost:3000/books/list> with your browser
1280and be sure that the book list is displayed via the relationships
1281established above. You can leave the development server running for
1282the next step if you wish.
3533daff 1283
c2dfb562 1284B<Note:> You will not see the authors yet because the view does not yet
1285use the new relations. Read on to the next section where we update the
1286template to do that.
3533daff 1287
acbd7bdd 1291Let's add a new column to our book list page that takes advantage of
1292the relationship information we manually added to our schema files in
a46b474e 1293the previous section. Edit C<root/src/books/list.tt2> and replace
3b1fa91b 1294the "empty" table cell "<td></td>" with the following:
3533daff 1295
acbd7bdd 1296 ...
3533daff 1297 <td>
1298 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1299 [% # loop in 'side effect notation' to load just the last names of the -%]
a0c5188a 1300 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
3533daff 1301 [% # a value, so nothing will be printed here. But, if you have something -%]
1302 [% # in TT that does return a method and you don't want it printed, you -%]
1303 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1304 [% # call it and discard the return value. -%]
1305 [% tt_authors = [ ];
1306 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1307 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1308 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1309 ([% tt_authors.size | html %])
1310 [% # Use another TT vmethod to join & print the names & comma separators -%]
1311 [% tt_authors.join(', ') | html %]
1312 </td>
acbd7bdd 1313 ...
3533daff 1314
1390ef0e 1315Then hit "Reload" in your browser (note that you don't need to reload
3533daff 1316the development server or use the C<-r> option when updating TT
1390ef0e 1317templates) and you should now see the number of authors each book has
1318along with a comma-separated list of the authors' last names. (If you
1319didn't leave the development server running from the previous step,
1320you will obviously need to start it before you can refresh your
1321browser window.)
1323If you are still running the development server with C<DBIC_TRACE>
1324enabled, you should also now see five more C<SELECT> statements in the
1325debug output (one for each book as the authors are being retrieved by
a46b474e 1326DBIx::Class):
3533daff 1327
c2dfb562 1328 SELECT, me.title, me.rating FROM books me:
3b1fa91b 1329 SELECT, author.first_name, author.last_name FROM book_author me
1330 JOIN author author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '1'
1331 SELECT, author.first_name, author.last_name FROM book_author me
1332 JOIN author author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '2'
1333 SELECT, author.first_name, author.last_name FROM book_author me
1334 JOIN author author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '3'
1335 SELECT, author.first_name, author.last_name FROM book_author me
1336 JOIN author author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '4'
1337 SELECT, author.first_name, author.last_name FROM book_author me
1338 JOIN author author ON ( = me.author_id ) WHERE ( me.book_id = ? ): '5'
c2dfb562 1339
1340Also note in C<root/src/books/list.tt2> that we are using "| html", a
1341type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1342and &gt; and avoid various types of dangerous hacks against your
1343application. In a real application, you would probably want to put
1344"| html" at the end of every field where a user has control over the
1345information that can appear in that field (and can therefore inject
1346markup or code if you don't "neutralize" those fields). In addition to
1347"| html", Template Toolkit has a variety of other useful filters that
1348can found in the documentation for
3533daff 1350
1354In some situations, it can be useful to run your application and
1355display a page without using a browser. Catalyst lets you do this
1356using the C<scripts/> script. Just supply the URL you
1357wish to display and it will run that request through the normal
1358controller dispatch logic and use the appropriate view to render the
1359output (obviously, complex pages may dump a lot of text to your
1360terminal window). For example, if you type:
1362 $ script/ "/books/list"
1364You should get the same text as if you visited
1365L<http://localhost:3000/books/list> with the normal development server
1366and asked your browser to view the page source.
3533daff 1367
1390ef0e 1368
4b4d3884 1371B<NOTE: The rest of this chapter of the tutorial is optional. You can
1372skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>,
3533daff 1373if you wish.>
acbd7bdd 1375
8a472b34 1376=head2 Using 'RenderView' for the Default View
1390ef0e 1377
1378Once your controller logic has processed the request from a user, it
1379forwards processing to your view in order to generate the appropriate
3533daff 1380response output. Catalyst uses
1390ef0e 1381L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
4d63a0d5 1382default to automatically perform this operation. If you look in
1390ef0e 1383C<lib/MyApp/Controller/>, you should see the empty
3533daff 1384definition for the C<sub end> method:
1386 sub end : ActionClass('RenderView') {}
1390ef0e 1388The following bullet points provide a quick overview of the
3533daff 1389C<RenderView> process:
1391=over 4
1393=item *
1395C<> is designed to hold application-wide logic.
1397=item *
1390ef0e 1399At the end of a given user request, Catalyst will call the most specific
1400C<end> method that's appropriate. For example, if the controller for a
1401request has an C<end> method defined, it will be called. However, if
1402the controller does not define a controller-specific C<end> method, the
3533daff 1403"global" C<end> method in C<> will be called.
1405=item *
1407Because the definition includes an C<ActionClass> attribute, the
1408L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1409will be executed B<after> any code inside the definition of C<sub end>
1410is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1411for more information on C<ActionClass>.
1413=item *
1390ef0e 1415Because C<sub end> is empty, this effectively just runs the default
1416logic in C<RenderView>. However, you can easily extend the
1417C<RenderView> logic by adding your own code inside the empty method body
1418(C<{}>) created by the Catalyst Helpers when we first ran the
1419C<> to initialize our application. See
1420L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
4d63a0d5 1421detailed information on how to extend C<RenderView> in C<sub end>.
3533daff 1422
1426=head2 Using The Default Template Name
1390ef0e 1428By default, C<Catalyst::View::TT> will look for a template that uses the
1429same name as your controller action, allowing you to save the step of
1430manually specifying the template name in each action. For example, this
1431would allow us to remove the
1432C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1433C<list> action in the Books controller. Open
3533daff 1434C<lib/MyApp/Controller/> in your editor and comment out this line
1435to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1436has changed):
1438 =head2 list
1440 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1442 =cut
1444 sub list : Local {
1445 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1446 # 'Context' that's used to 'glue together' the various components
1447 # that make up the application
1448 my ($self, $c) = @_;
1450 # Retrieve all of the book records as book model objects and store in the
1451 # stash where they can be accessed by the TT template
3b1fa91b 1452 $c->stash->{books} = [$c->model('DB::Book')->all];
3533daff 1453
1454 # Set the TT template to use. You will almost always want to do this
1455 # in your action methods (actions methods respond to user input in
1456 # your controllers).
1457 #$c->stash->{template} = 'books/list.tt2';
1458 }
3533daff 1460
1390ef0e 1461You should now be able to restart the development server as per the
3533daff 1462previous section and access the L<http://localhost:3000/books/list>
1463as before.
1465B<NOTE:> Please note that if you use the default template technique,
1466you will B<not> be able to use either the C<$c-E<gt>forward> or
4b4d3884 1467the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1468Chapter 9 of the Tutorial).
3533daff 1469
3b1fa91b 1470B<IMPORTANT:> Make sure that you do NOT skip the following section
1471before continuing to the next chapter 4 Basic CRUD.
3533daff 1472
4d63a0d5 1473=head2 Return To A Manually Specified Template
3533daff 1474
1475In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1476later in the tutorial, you should remove the comment from the
1477statement in C<sub list> in C<lib/MyApp/Controller/>:
1479 $c->stash->{template} = 'books/list.tt2';
1390ef0e 1481Then delete the C<TEMPLATE_EXTENSION> line in
3533daff 1482C<lib/MyApp/View/>.
1390ef0e 1484You should then be able to restart the development server and
3533daff 1485access L<http://localhost:3000/books/list> in the same manner as
1486with earlier sections.
1489=head1 AUTHOR
1491Kennedy Clark, C<>
1493Please report any errors, issues or suggestions to the author. The
1494most recent version of the Catalyst Tutorial can be found at
82ab4bbf 1495L<>.
3533daff 1496
45c7830f 1497Copyright 2006-2008, Kennedy Clark, under Creative Commons License
8482d557 1498(L<>).