replace reference to deprecated CatalystX::ListFramework::Builder with Catalyst:...
[catagits/Catalyst-Manual.git] / lib / Catalyst / Manual / Tutorial / 03_MoreCatalystBasics.pod
3533daff 1=head1 NAME
3ab6187c 3Catalyst::Manual::Tutorial::03_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
3ab6187c 16L<Introduction|Catalyst::Manual::Tutorial::01_Intro>
3533daff 17
18=item 2
3ab6187c 20L<Catalyst Basics|Catalyst::Manual::Tutorial::02_CatalystBasics>
3533daff 21
22=item 3
3ab6187c 24B<03_More Catalyst Basics>
3533daff 25
26=item 4
3ab6187c 28L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
3533daff 29
30=item 5
3ab6187c 32L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>
3533daff 33
34=item 6
3ab6187c 36L<Authorization|Catalyst::Manual::Tutorial::06_Authorization>
3533daff 37
38=item 7
3ab6187c 40L<Debugging|Catalyst::Manual::Tutorial::07_Debugging>
3533daff 41
42=item 8
3ab6187c 44L<Testing|Catalyst::Manual::Tutorial::08_Testing>
3533daff 45
46=item 9
3ab6187c 48L<Advanced CRUD|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
3533daff 49
50=item 10
3ab6187c 52L<Appendices|Catalyst::Manual::Tutorial::10_Appendices>
3533daff 53
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
3ab6187c 69L<Catalyst::Manual::Tutorial::01_Intro|Catalyst::Manual::Tutorial::01_Intro>.
3533daff 70
a586a09f 71Please take a look at
3ab6187c 72L<Catalyst::Manual::Tutorial::01_Intro/CATALYST INSTALLATION> before
a586a09f 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
fce83e5f 192 use Catalyst qw/
193 -Debug
3b1fa91b 194 ConfigLoader
195 Static::Simple
acbd7bdd 196
3b1fa91b 197 StackTrace
198 /;
1390ef0e 199
94d8da41 200B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
acbd7bdd 201techniques to load these plugins/flags. For example, you might see
202the following:
94d8da41 203
acbd7bdd 204 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
94d8da41 205
206Don't let these variations confuse you -- they all accomplish the same
1390ef0e 209This tells Catalyst to start using one new plugin,
210L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
211stack trace to the standard Catalyst "debug screen" (the screen
212Catalyst sends to your browser when an error occurs). Be aware that
213L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
214browser, not in the console window from which you're running your
215application, which is where logging output usually goes.
3533daff 216
3b1fa91b 217Make sure that when adding new plugins that you include them as a new
218dependancies within the Makefile.PL file. For example, after adding
219the StackTrace plugin the Makefile.PL should include the following
222 requires 'Catalyst::Plugin::StackTrace';
1390ef0e 225B<Notes:>
3533daff 226
227=over 4
1390ef0e 229=item *
231C<__PACKAGE__> is just a shorthand way of referencing the name of the
232package where it is used. Therefore, in C<>, C<__PACKAGE__>
233is equivalent to C<MyApp>.
3533daff 234
1390ef0e 235=item *
3533daff 236
1390ef0e 237You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
238before you put your application into production, but it can be helpful
239during development.
3533daff 240
1390ef0e 241=item *
3533daff 242
1390ef0e 243When specifying plugins on the C<__PACKAGE__-E<gt>setup> line, you can
244omit C<Catalyst::Plugin::> from the name. Additionally, you can
245spread the plugin names across multiple lines as shown here, or place
246them all on one (or more) lines as with the default configuration.
cca5cd98 247
3533daff 248=back
3533daff 250
1390ef0e 253As discussed earlier, controllers are where you write methods that
254interact with user input. Typically, controller methods respond to
4d63a0d5 255C<GET> and C<POST> requests from the user's web browser.
3533daff 256
257Use the Catalyst C<create> script to add a controller for book-related
260 $ script/ controller Books
261 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
262 exists "/home/me/MyApp/script/../t"
263 created "/home/me/MyApp/script/../lib/MyApp/Controller/"
264 created "/home/me/MyApp/script/../t/controller_Books.t"
4b4d3884 266Then edit C<lib/MyApp/Controller/> (as discussed in Chapter 2 of
1390ef0e 267the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
268each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
269and add the following method to the controller:
3533daff 270
271 =head2 list
273 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
275 =cut
1390ef0e 276
3533daff 277 sub list : Local {
278 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
279 # 'Context' that's used to 'glue together' the various components
280 # that make up the application
281 my ($self, $c) = @_;
283 # Retrieve all of the book records as book model objects and store in the
284 # stash where they can be accessed by the TT template
3b1fa91b 285 # $c->stash->{books} = [$c->model('DB::Book')->all];
1390ef0e 286 # But, for now, use this code until we create the model later
287 $c->stash->{books} = '';
3533daff 289 # Set the TT template to use. You will almost always want to do this
290 # in your action methods (action methods respond to user input in
291 # your controllers).
292 $c->stash->{template} = 'books/list.tt2';
293 }
1390ef0e 295B<TIP>: See Appendix 1 for tips on removing the leading spaces when
296cutting and pasting example code from POD-based documents.
3533daff 297
1390ef0e 298Programmers experienced with object-oriented Perl should recognize
299C<$self> as a reference to the object where this method was called.
300On the other hand, C<$c> will be new to many Perl programmers who have
301not used Catalyst before (it's sometimes written as C<$context>). The
302Context object is automatically passed to all Catalyst components. It
303is used to pass information between components and provide access to
304Catalyst and plugin functionality.
3533daff 305
245b41d1 306Catalyst actions are regular Perl methods, but they make use of
307attributes (the "C<: Local>" next to the "C<sub list>" in the code
0416017e 308above) to provide additional information to the Catalyst dispatcher
309logic (note that the space between the colon and the attribute name is
4d63a0d5 310optional; you will see attributes written both ways). Most Catalyst
245b41d1 311Controllers use one of five action types:
0416017e 312
313=over 4
315=item *
245b41d1 317B<:Private> -- Use C<:Private> for methods that you want to make into
4d63a0d5 318an action, but you do not want Catalyst to directly expose
245b41d1 319to your users. Catalyst will not map C<:Private> methods to a URI.
320Use them for various sorts of "special" methods (the C<begin>,
321C<auto>, etc. discussed below) or for methods you want to be able to
322C<forward> or C<detach> to. (If the method is a plain old "helper
323method" that you don't want to be an action at all, then just define
324the method without any attribute -- you can call it in your code, but
325the Catalyst dispatcher will ignore it.)
0416017e 326
245b41d1 327There are five types of "special" build-in C<:Private> actions:
328C<begin>, C<end>, C<default>, C<index>, and C<auto>.
0416017e 329
26c9cad5 330=over 4
0416017e 332=item *
334With C<begin>, C<end>, C<default>, C<index> private actions, only the
335most specific action of each type will be called. For example, if you
336define a C<begin> action in your controller it will I<override> a
337C<begin> action in your application/root controller -- I<only> the
338action in your controller will be called.
340=item *
342Unlike the other actions where only a single method is called for each
343request, I<every> auto action along the chain of namespaces will be
344called. Each C<auto> action will be called I<from the application/root
345controller down through the most specific class>.
349=item *
245b41d1 351B<:Path> -- C<:Path> actions let you map a method to an explicit URI
352path. For example, "C<:Path('list')>" in
0416017e 353C<lib/MyApp/Controller/> would match on the URL
245b41d1 354C<http://localhost:3000/books/list> but "C<:Path('/list')>" would match
355on C<http://localhost:3000/list>. You can use C<:Args()> to specify
7e8cd009 356how many arguments an action should accept. See
245b41d1 357L<Catalyst::Manual::Intro/Action_types> for more information and a few
0416017e 358examples.
360=item *
245b41d1 362B<:Local> -- C<:Local> is merely a shorthand for
363"C<:Path('_name_of_method_')>". For example, these are equivalent:
364"C<sub create_book :Local {...}>" and
365"C<sub create_book :Path('create_book') {...}>".
367=item *
369B<:Global> -- C<:Global> is merely a shorthand for
370"C<:Path('/_name_of_method_')>". For example, these are equivalent:
371"C<sub create_book :Global {...}>" and
372"C<sub create_book :Path('/create_book') {...}>".
374=item *
376B<:Chained> -- Newer Catalyst applications tend to use the Chained
0416017e 377dispatch form of action types because of its power and flexibility.
4d63a0d5 378It allows a series of controller methods to be automatically dispatched
0416017e 379to service a single user request. See
3ab6187c 380L<Catalyst::Manual::Tutorial::04_BasicCRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
0416017e 381and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
382for more information on chained actions.
386You should refer to L<Catalyst::Manual::Intro/Action_types> for
387additional information and for coverage of some lesser-used action
245b41d1 388types not discussed here (C<Regex> and C<LocalRegex>).
3533daff 389
4d63a0d5 393As mentioned in Chapter 2 of the tutorial, views are where you render
394output, typically for display in the user's web browser (but also
395possibly using into output-generation systems, such as PDF or JSON).
396The code in C<lib/MyApp/View> selects the I<type> of view to use, with
397the actual rendering template found in the C<root> directory. As with
398virtually every aspect of Catalyst, options abound when it comes to the
399specific view technology you adopt inside your application. However,
400most Catalyst applications use the Template Toolkit, known as TT (for
401more information on TT, see L<>). Other
402somewhat popular view technologies include Mason
403(L<> and L<>) and
1390ef0e 404L<HTML::Template> (L<>).
407=head2 Create a Catalyst View
3533daff 408
409When using TT for the Catalyst view, there are two main helper scripts:
411=over 4
413=item *
417=item *
de966eb4 423Both helpers are similar. C<TT> creates the C<lib/MyApp/View/>
3533daff 424file and leaves the creation of any hierarchical template organization
425entirely up to you. (It also creates a C<t/view_TT.t> file for testing;
4b4d3884 426test cases will be discussed in Chapter 8.) C<TTSite>, on the other hand,
de966eb4 427creates a modular and hierarchical view layout with
1390ef0e 428separate Template Toolkit (TT) files for common header and footer
429information, configuration values, a CSS stylesheet, and more.
de966eb4 431While C<TTSite> was useful to bootstrap a project, its use is now
4d63a0d5 432deprecated and it should be considered historical. For most Catalyst
de966eb4 433applications it adds redundant functionality and structure; many in the
434Catalyst community recommend that it's easier to learn both Catalyst and
435Template Toolkit if you use the more basic C<TT> approach.
436Consequently, this tutorial will use "plain old TT."
1390ef0e 437
438Enter the following command to enable the C<TT> style of view
3533daff 439rendering for this tutorial:
1390ef0e 441 $ script/ view TT TT
3533daff 442 exists "/home/me/MyApp/script/../lib/MyApp/View"
443 exists "/home/me/MyApp/script/../t"
1390ef0e 444 created "/home/me/MyApp/script/../lib/MyApp/View/"
445 created "/home/me/MyApp/script/../t/view_TT.t"
3533daff 446
1390ef0e 447This simply creates a view called C<TT> (the second 'TT' argument) in
448a file called C<> (the first 'TT' argument). It is now up to you
449to decide how you want to structure your view layout. For the
450tutorial, we will start with a very simple TT template to initially
451demonstrate the concepts, but quickly migrate to a more typical
452"wrapper page" type of configuration (where the "wrapper" controls the
453overall "look and feel" of your site from a single file or set of
3533daff 455
1390ef0e 456Edit C<lib/MyApp/View/> and you should see that the default
457contents contains something similar to the following:
3533daff 458
1390ef0e 459 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
3533daff 460
1390ef0e 461And update it to match:
463 __PACKAGE__->config(
464 # Change default TT extension
466 # Set the location for TT files
6abd3023 468 MyApp->path_to( 'root', 'src' ),
1390ef0e 469 ],
470 );
3533daff 471
1390ef0e 472B<NOTE:> Make sure to add a comma after '.tt2' outside the single
191dee29 475This changes the default extension for Template Toolkit from '.tt' to
1390ef0e 476'.tt2' and changes the base directory for your template files from
de966eb4 477C<root> to C<root/src>. These changes from the default are done mostly
478to facilitate the application we're developing in this tutorial; as with
479most things Perl, there's more than one way to do it...
1390ef0e 480
acbd7bdd 481B<Note:> We will use C<root/src> as the base directory for our
482template files, which a full naming convention of
483C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
484use C<root/> as the base (with a full filename pattern of
1390ef0e 487
488=head2 Create a TT Template Page
3533daff 489
490First create a directory for book-related TT templates:
1390ef0e 492 $ mkdir -p root/src/books
3533daff 493
494Then create C<root/src/books/list.tt2> in your editor and enter:
496 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
497 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
498 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
499 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
1390ef0e 501 [% # Provide a title -%]
3533daff 502 [% META title = 'Book List' -%]
504 <table>
505 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
506 [% # Display each book in a table row %]
507 [% FOREACH book IN books -%]
508 <tr>
509 <td>[% book.title %]</td>
510 <td>[% book.rating %]</td>
a46b474e 511 <td></td>
3533daff 512 </tr>
513 [% END -%]
514 </table>
516As indicated by the inline comments above, the C<META title> line uses
1390ef0e 517TT's META feature to provide a title to the "wrapper" that we will
518create later. Meanwhile, the C<FOREACH> loop iterates through each
519C<book> model object and prints the C<title> and C<rating> fields.
3533daff 520
4d63a0d5 521The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
522supports a wide variety of directives for "calling" other files,
523looping, conditional logic, etc. In general, TT simplifies the usual
524range of Perl operators down to the single dot (C<.>) operator. This
525applies to operations as diverse as method calls, hash lookups, and list
526index values (see
527L<> for
528details and examples). In addition to the usual C<Template> module Pod
529documentation, you can access the TT manual at
55beb65d 530L<>.
3533daff 531
1390ef0e 532B<TIP:> While you can build all sorts of complex logic into your TT
533templates, you should in general keep the "code" part of your templates
534as simple as possible. If you need more complex logic, create helper
535methods in your model that abstract out a set of code into a single call
536from your TT template. (Note that the same is true of your controller
537logic as well -- complex sections of code in your controllers should
538often be pulled out and placed into your model objects.)
541=head2 Test Run The Application
543To test your work so far, first start the development server:
545 $ script/
547Then point your browser to L<http://localhost:3000> and you should
548still get the Catalyst welcome page. Next, change the URL in your
549browser to L<http://localhost:3000/books/list>. If you have
550everything working so far, you should see a web page that displays
551nothing other than our column headers for "Title", "Rating", and
552"Author(s)" -- we will not see any books until we get the database and
553model working below.
555If you run into problems getting your application to run correctly, it
556might be helpful to refer to some of the debugging techniques covered in
fce83e5f 557the L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> chapter of the
1390ef0e 558tutorial.
3533daff 559
563In this step, we make a text file with the required SQL commands to
1390ef0e 564create a database table and load some sample data. We will use SQLite,
565a popular database that is lightweight and easy to use. Open
566C<myapp01.sql> in your editor and enter:
3533daff 567
568 --
569 -- Create a very simple database to hold book and author information
570 --
3b1fa91b 571 CREATE TABLE book (
3533daff 572 id INTEGER PRIMARY KEY,
573 title TEXT ,
574 rating INTEGER
575 );
3b1fa91b 576 -- 'book_author' is a many-to-many join table between books & authors
577 CREATE TABLE book_author (
3533daff 578 book_id INTEGER,
579 author_id INTEGER,
580 PRIMARY KEY (book_id, author_id)
581 );
3b1fa91b 582 CREATE TABLE author (
3533daff 583 id INTEGER PRIMARY KEY,
584 first_name TEXT,
585 last_name TEXT
586 );
587 ---
588 --- Load some sample data
589 ---
3b1fa91b 590 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
591 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
592 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
593 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
594 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
595 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
596 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
597 INSERT INTO author VALUES (3, 'Christian', 'Degu');
598 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
599 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
600 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
601 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
602 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
603 INSERT INTO book_author VALUES (1, 1);
604 INSERT INTO book_author VALUES (1, 2);
605 INSERT INTO book_author VALUES (1, 3);
606 INSERT INTO book_author VALUES (2, 4);
607 INSERT INTO book_author VALUES (3, 5);
608 INSERT INTO book_author VALUES (4, 6);
609 INSERT INTO book_author VALUES (4, 7);
610 INSERT INTO book_author VALUES (5, 8);
3533daff 611
3533daff 612Then use the following command to build a C<myapp.db> SQLite database:
614 $ sqlite3 myapp.db < myapp01.sql
616If you need to create the database more than once, you probably want to
617issue the C<rm myapp.db> command to delete the database before you use
1390ef0e 618the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
3533daff 619
620Once the C<myapp.db> database file has been created and initialized, you
621can use the SQLite command line environment to do a quick dump of the
622database contents:
624 $ sqlite3 myapp.db
acbd7bdd 625 SQLite version 3.5.9
3533daff 626 Enter ".help" for instructions
3b1fa91b 627 sqlite> select * from book;
3533daff 628 1|CCSP SNRS Exam Certification Guide|5
629 2|TCP/IP Illustrated, Volume 1|5
630 3|Internetworking with TCP/IP Vol.1|4
631 4|Perl Cookbook|5
632 5|Designing with Web Standards|5
633 sqlite> .q
634 $
3b1fa91b 638 $ sqlite3 myapp.db "select * from book"
3533daff 639 1|CCSP SNRS Exam Certification Guide|5
640 2|TCP/IP Illustrated, Volume 1|5
641 3|Internetworking with TCP/IP Vol.1|4
642 4|Perl Cookbook|5
643 5|Designing with Web Standards|5
645As with most other SQL tools, if you are using the full "interactive"
646environment you need to terminate your SQL commands with a ";" (it's not
647required if you do a single SQL statement on the command line). Use
648".q" to exit from SQLite from the SQLite interactive mode and return to
649your OS command prompt.
3b1fa91b 651Please note that here we have chosen to use 'singular' table names. This
652is because the default inflection code for L<DBIx::Class:Schema::Loader>
653does NOT handle plurals. There has been much philosophical discussion
654on whether table names should be plural or singular. There is no one
655correct answer, as long as one makes a choice and remains consistent
656with it. If you prefer plural table names (e.g. they are easier and
657more natural to read) then you will need to pass it an inflect_map
658option. See L<DBIx::Class:Schema::Loader> for more information.
a6d800ac 660For using other databases, such as PostgreSQL or MySQL, see
3ab6187c 661L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices>.
3533daff 662
acbd7bdd 663
8a472b34 664=head1 DATABASE ACCESS WITH DBIx::Class
3533daff 665
27909ed4 666Catalyst can be used with virtually any form of datastore available
667via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
668can be used to access databases through the traditional Perl C<DBI>
669interface or you can use a model to access files of any type on the
670filesystem. However, most Catalyst applications use some form of
671object-relational mapping (ORM) technology to create objects
672associated with tables in a relational database. Matt Trout's
673L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
674as the Perl-based ORM technology of choice. Most new Catalyst
a46b474e 675applications rely on DBIx::Class, as will this tutorial.
3533daff 676
a46b474e 677Although DBIx::Class has included support for a C<create=dynamic> mode
678to automatically read the database structure every time the
679application starts, it's use is no longer recommended. While it can
680make for "flashy" demos, the use of the C<create=static> mode we use
681below can be implemented just as quickly and provides many advantages
682(such as the ability to add your own methods to the overall DBIC
683framework, a technique that we see in Chapter 4).
3533daff 684
1390ef0e 685
a46b474e 686=head2 Make Sure You Have a Recent Version of the DBIx::Class Model
27909ed4 687
688First, let's be sure we have a recent version of the DBIC helper,
689L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
690running this command:
692 $ perl -MCatalyst::Model::DBIC::Schema -e \
693 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
694 0.23
fce83e5f 696Please note the '\' above. Depending on your environment, you might
697be able to cut and paste the text as shown or need to remove the '\'
698character to that the command is all on a single line.
3b1fa91b 699
27909ed4 700If you don't have version 0.23 or higher, please run this command
701to install it directly from CPAN:
703 $ sudo cpan Catalyst::Model::DBIC::Schema
705And re-run the version print command to verify that you are now at
7060.23 or higher.
a46b474e 709=head2 Create Static DBIx::Class Schema Files
27909ed4 710
98fd8420 711Before you continue, make sure your C<myapp.db> database file is in
712the application's topmost directory. Now use the model helper with
713the C<create=static> option to read the database with
27909ed4 714L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
715automatically build the required files for us:
3533daff 716
4ab6212d 717 $ script/ model DB DBIC::Schema MyApp::Schema \
fce83e5f 718 create=static dbi:SQLite:myapp.db
1390ef0e 719 exists "/home/me/MyApp/script/../lib/MyApp/Model"
720 exists "/home/me/MyApp/script/../t"
27909ed4 721 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
722 Schema dump completed.
1390ef0e 723 created "/home/me/MyApp/script/../lib/MyApp/Model/"
724 created "/home/me/MyApp/script/../t/model_DB.t"
3533daff 725
fce83e5f 726Please note the '\' above. Depending on your environment, you might
727be able to cut and paste the text as shown or need to remove the '\'
728character to that the command is all on a single line.
3b1fa91b 729
27909ed4 730The C<script/> command breaks down like this:
732=over 4
734=item *
736C<DB> is the name of the model class to be created by the helper in
739=item *
741C<DBIC::Schema> is the type of the model to create.
743=item *
745C<MyApp::Schema> is the name of the DBIC schema file written to
748=item *
750C<create=static> causes
751L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
752load the schema as it runs and then write that information out
753into files.
755=item *
757C<components=TimeStamp> causes the help to include the
758L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp> DBIC component.
760=item *
762And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
763for use with SQLite.
767If you look in the C<lib/MyApp/> file, you will find that it
768only contains a call to the C<load_namespaces> method. You will also
769find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
770has a subdirectory called "Result". This "Result" subdirectory then
771has files named according to each of the tables in our simple database
3b1fa91b 772(C<>, C<>, and C<>). These three
a46b474e 773files are called "Result Classes" in DBIx::Class nomenclature. Although the
27909ed4 774Result Class files are named after tables in our database, the classes
775correspond to the I<row-level data> that is returned by DBIC (more on
776this later, especially in
3ab6187c 777L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
27909ed4 778
779The idea with the Result Source files created under
780C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
781edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
782warning. If you place all of your changes below that point in the
783file, you can regenerate the automatically created information at the
784top of each file should your database structure get updated.
786Also note the "flow" of the model information across the various files
787and directories. Catalyst will initially load the model from
788C<lib/MyApp/Model/>. This file contains a reference to
789C<lib/MyApp/>, so that file is loaded next. Finally, the
790call to C<load_namespaces> in C<> will load each of the
791"Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
792The final outcome is that Catalyst will dynamically create three
793table-specific Catalyst models every time the application starts (you
794can see these three model files listed in the debug output generated
795when you launch the application).
797B<NOTE:> Older versions of
798L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
a46b474e 799deprecated DBIx::Class C<load_classes> technique instead of the newer
27909ed4 800C<load_namspaces>. For new applications, please try to use
801C<load_namespaces> since it more easily supports a very useful DBIC
802technique called "ResultSet Classes." If you need to convert an
803existing application from "load_classes" to "load_namespaces," you can
804use this process to automate the migration (but first make sure you
805have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
807 $ # First delete the existing schema file to disable "compatibility" mode
808 $ rm lib/MyApp/
809 $
810 $ # Then re-run the helper to build the files for "load_namespaces"
811 $ script/ model DB DBIC::Schema MyApp::Schema \
fce83e5f 812 create=static dbi:SQLite:myapp.db
3b1fa91b 813 $
27909ed4 814 $ # Now convert the existing files over
815 $ cd lib/MyApp/Schema
816 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
817 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
818 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
819 $ cd ../../..
820 $
821 $ # And finally delete the old files
822 $ rm lib/MyApp/Schema/*.pm
824The "C<perl -MIO::ALL ...>" script will copy all the customized
825relationship (and other) information below "C<# DO NOT MODIFY>" line
826from the old files in C<lib/MyApp/Schema> to the new files in
827C<lib/MyApp/Schema/Result> (we will be starting to add some
828"customized relationship information in the section below).
3533daff 829
dc9a0503 830
acbd7bdd 833Open C<lib/MyApp/Controller/> and un-comment the model code we
834left disabled earlier so that your version matches the following (un-
3b1fa91b 835comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
acbd7bdd 836and delete the next 2 lines):
1390ef0e 837
838 =head2 list
840 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
842 =cut
844 sub list : Local {
845 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
846 # 'Context' that's used to 'glue together' the various components
847 # that make up the application
848 my ($self, $c) = @_;
850 # Retrieve all of the book records as book model objects and store in the
851 # stash where they can be accessed by the TT template
3b1fa91b 852 $c->stash->{books} = [$c->model('DB::Book')->all];
1390ef0e 853
854 # Set the TT template to use. You will almost always want to do this
855 # in your action methods (action methods respond to user input in
856 # your controllers).
857 $c->stash->{template} = 'books/list.tt2';
858 }
3b1fa91b 860B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
861above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
c93b5eaa 862two are equivalent. Either way, C<$c-E<gt>model> returns a
863L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
4d63a0d5 864against the database and iterating over the set of results that is
c93b5eaa 865returned.
867We are using the C<-E<gt>all> to fetch all of the books. DBIC
868supports a wide variety of more advanced operations to easily do
869things like filtering and sorting the results. For example, the
518f3851 870following could be used to sort the results by descending title:
c93b5eaa 871
3b1fa91b 872 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
c93b5eaa 873
874Some other examples are provided in
875L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
876additional information found at L<DBIx::Class::ResultSet/search>,
879and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
1390ef0e 880
882=head2 Test Run The Application
3533daff 883
1435672d 884First, let's enable an environment variable that causes DBIx::Class to
acbd7bdd 885dump the SQL statements used to access the database. This is a
1435672d 886helpful trick when you are trying to debug your database-oriented
3533daff 888
889 $ export DBIC_TRACE=1
4d63a0d5 891This assumes you are using bash as your shell -- adjust accordingly if
3533daff 892you are using a different shell (for example, under tcsh, use
893C<setenv DBIC_TRACE 1>).
d0496197 895B<NOTE:> You can also set this in your code using
3533daff 896C<$class-E<gt>storage-E<gt>debug(1);>. See
897L<DBIx::Class::Manual::Troubleshooting> for details (including options
4d63a0d5 898to log to a file instead of displaying to the Catalyst development server
3533daff 899log).
1390ef0e 901Then launch the Catalyst development server. The log output should
902display something like:
3533daff 903
acbd7bdd 904 $ script/
3533daff 905 [debug] Debug messages enabled
1390ef0e 906 [debug] Statistics enabled
3533daff 907 [debug] Loaded plugins:
908 .----------------------------------------------------------------------------.
fce83e5f 909 | Catalyst::Plugin::ConfigLoader 0.22 |
910 | Catalyst::Plugin::StackTrace 0.09 |
3b1fa91b 911 | Catalyst::Plugin::Static::Simple 0.21 |
3533daff 912 '----------------------------------------------------------------------------'
914 [debug] Loaded dispatcher "Catalyst::Dispatcher"
915 [debug] Loaded engine "Catalyst::Engine::HTTP"
916 [debug] Found home "/home/me/MyApp"
45d511e0 917 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
3533daff 918 [debug] Loaded components:
919 .-----------------------------------------------------------------+----------.
920 | Class | Type |
921 +-----------------------------------------------------------------+----------+
922 | MyApp::Controller::Books | instance |
923 | MyApp::Controller::Root | instance |
d0496197 924 | MyApp::Model::DB | instance |
3b1fa91b 925 | MyApp::Model::DB::Author | class |
926 | MyApp::Model::DB::Book | class |
927 | MyApp::Model::DB::BookAuthor | class |
3533daff 928 | MyApp::View::TT | instance |
929 '-----------------------------------------------------------------+----------'
931 [debug] Loaded Private actions:
932 .----------------------+--------------------------------------+--------------.
933 | Private | Class | Method |
934 +----------------------+--------------------------------------+--------------+
935 | /default | MyApp::Controller::Root | default |
936 | /end | MyApp::Controller::Root | end |
1390ef0e 937 | /index | MyApp::Controller::Root | index |
3533daff 938 | /books/index | MyApp::Controller::Books | index |
939 | /books/list | MyApp::Controller::Books | list |
940 '----------------------+--------------------------------------+--------------'
942 [debug] Loaded Path actions:
943 .-------------------------------------+--------------------------------------.
944 | Path | Private |
945 +-------------------------------------+--------------------------------------+
1390ef0e 946 | / | /default |
947 | / | /index |
948 | /books | /books/index |
3533daff 949 | /books/list | /books/list |
950 '-------------------------------------+--------------------------------------'
3b1fa91b 952 [info] MyApp powered by Catalyst 5.80003
acbd7bdd 953 You can connect to your server at http://debian:3000
3533daff 954
1390ef0e 955B<NOTE:> Be sure you run the C<script/> command from
956the 'base' directory of your application, not inside the C<script>
957directory itself or it will not be able to locate the C<myapp.db>
958database file. You can use a fully qualified or a relative path to
959locate the database file, but we did not specify that when we ran the
3533daff 960model helper earlier.
962Some things you should note in the output above:
964=over 4
1390ef0e 966=item *
3533daff 967
1390ef0e 968Catalyst::Model::DBIC::Schema dynamically created three model classes,
969one to represent each of the three tables in our database
3b1fa91b 970(C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
971and C<MyApp::Model::DB::Book>).
3533daff 972
1390ef0e 973=item *
3533daff 974
975The "list" action in our Books controller showed up with a path of
980Point your browser to L<http://localhost:3000> and you should still get
981the Catalyst welcome page.
983Next, to view the book list, change the URL in your browser to
984L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 985books loaded by the C<myapp01.sql> script above without any formatting.
986The rating for each book should appear on each row, but the "Author(s)"
191dee29 987column will still be blank (we will fill that in later).
3533daff 988
a46b474e 989Also notice in the output of the C<script/> that
990DBIx::Class used the following SQL to retrieve the data:
3533daff 991
fce83e5f 992 SELECT, me.title, me.rating FROM book me
3533daff 993
994because we enabled DBIC_TRACE.
0c51850e 996You now have the beginnings of a simple but workable web application.
3533daff 997Continue on to future sections and we will develop the application
998more fully.
1390ef0e 1001=head1 CREATE A WRAPPER FOR THE VIEW
acbd7bdd 1003When using TT, you can (and should) create a wrapper that will
1390ef0e 1004literally wrap content around each of your templates. This is
1005certainly useful as you have one main source for changing things that
1006will appear across your entire site/application instead of having to
1007edit many individual files.
1010=head2 Configure For The Wrapper
1012In order to create a wrapper, you must first edit your TT view and
1013tell it where to find your wrapper file. Your TT view is located in
1016Edit C<lib/MyApp/View/> and change it to match the following:
1018 __PACKAGE__->config(
1019 # Change default TT extension
1020 TEMPLATE_EXTENSION => '.tt2',
1021 # Set the location for TT files
1022 INCLUDE_PATH => [
c2dfb562 1023 MyApp->path_to( 'root', 'src' ),
1390ef0e 1024 ],
1025 # Set to 1 for detailed timer stats in your HTML as comments
1026 TIMER => 0,
1027 # This is your wrapper template located in the 'root/src'
1028 WRAPPER => 'wrapper.tt2',
1029 );
1032=head2 Create the Wrapper Template File and Stylesheet
1034Next you need to set up your wrapper template. Basically, you'll want
1035to take the overall layout of your site and put it into this file.
1036For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1038 <?xml version="1.0" encoding="UTF-8"?>
1039 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "">
1040 <html xmlns="" xml:lang="en" lang="en">
1041 <head>
1042 <title>[% template.title or "My Catalyst App!" %]</title>
1043 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1044 </head>
1046 <body>
1047 <div id="outer">
1048 <div id="header">
1049 [%# Your logo could go here -%]
1050 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1051 [%# Insert the page title -%]
1052 <h1>[% template.title or site.title %]</h1>
1053 </div>
1055 <div id="bodyblock">
1056 <div id="menu">
1057 Navigation:
1058 <ul>
1059 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1060 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1390ef0e 1061 </ul>
1062 </div><!-- end menu -->
1064 <div id="content">
1065 [%# Status and error messages %]
1066 <span class="message">[% status_msg %]</span>
1067 <span class="error">[% error_msg %]</span>
1068 [%# This is where TT will stick all of your template's contents. -%]
1069 [% content %]
1070 </div><!-- end content -->
1071 </div><!-- end bodyblock -->
1073 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 1074 </div><!-- end outer -->
1390ef0e 1075
1076 </body>
1077 </html>
1079Notice the status and error message sections in the code above:
1081 <span class="status">[% status_msg %]</span>
1082 <span class="error">[% error_msg %]</span>
1084If we set either message in the Catalyst stash (e.g.,
1085C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1086will be displayed whenever any view used by that request is rendered.
1087The C<message> and C<error> CSS styles can be customized to suit your
1088needs in the C<root/static/css/main.css> file we create below.
1092=over 4
1094=item *
1096The Catalyst stash only lasts for a single HTTP request. If
1097you need to retain information across requests you can use
1098L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
4b4d3884 1099Catalyst sessions in the Authentication chapter of the tutorial).
1390ef0e 1100
1101=item *
1103Although it is beyond the scope of this tutorial, you may wish to use
1104a JavaScript or AJAX tool such as jQuery (L<>) or
1105Dojo (L<>).
1110=head3 Create A Basic Stylesheet
1112First create a central location for stylesheets under the static
1115 $ mkdir root/static/css
1117Then open the file C<root/static/css/main.css> (the file referenced in
1118the stylesheet href link of our wrapper above) and add the following
1121 #header {
1122 text-align: center;
1123 }
1124 #header h1 {
1125 margin: 0;
1126 }
1127 #header img {
1128 float: right;
1129 }
1130 #footer {
1131 text-align: center;
1132 font-style: italic;
1133 padding-top: 20px;
1134 }
1135 #menu {
1136 font-weight: bold;
1137 background-color: #ddd;
1138 }
1139 #menu ul {
1140 list-style: none;
1141 float: left;
1142 margin: 0;
1143 padding: 0 0 50% 5px;
1144 font-weight: normal;
1145 background-color: #ddd;
1146 width: 100px;
1147 }
1148 #content {
1149 margin-left: 120px;
1150 }
1151 .message {
1152 color: #390;
1153 }
1154 .error {
1155 color: #f00;
1156 }
1158You may wish to check out a "CSS Framework" like Emastic
1159(L<>) as a way to quickly
1160provide lots of high-quality CSS functionality.
1163=head2 Test Run The Application
1165Restart the development server and hit "Reload" in your web browser
1166and you should now see a formatted version of our basic book list.
1167Although our wrapper and stylesheet are obviously very simple, you
1168should see how it allows us to control the overall look of an entire
1169website from two central files. To add new pages to the site, just
1170provide a template that fills in the C<content> section of our wrapper
1171template -- the wrapper will provide the overall feel of the page.
a46b474e 1174=head2 Updating the Generated DBIx::Class Result Class Files
3533daff 1175
acbd7bdd 1176Let's manually add some relationship information to the auto-generated
1177Result Class files. (Note: if you are using a database other than
1178SQLite, such as PostgreSQL, then the relationship could have been
1179automatically placed in the Result Class files. If so, you can skip
3b1fa91b 1180this step.) First edit C<lib/MyApp/Schema/Result/> and add the
acbd7bdd 1181following text below the C<# You can replace this text...> comment:
3533daff 1182
1183 #
1184 # Set relationships:
1390ef0e 1185 #
3533daff 1186
1187 # has_many():
1188 # args:
1189 # 1) Name of relationship, DBIC will create accessor with this name
1190 # 2) Name of the model class referenced by this relationship
1435672d 1191 # 3) Column name in *foreign* table (aka, foreign key in peer table)
fce83e5f 1192 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthor', 'book_id');
3533daff 1193
1194 # many_to_many():
1195 # args:
1196 # 1) Name of relationship, DBIC will create accessor with this name
1390ef0e 1197 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1198 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1199 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1200 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
3533daff 1201
1203B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1204file. As with any Perl package, we need to end the last line with
1205a statement that evaluates to C<true>. This is customarily done with
1206C<1;> on a line by itself.
a46b474e 1208This code defines both a C<has_many> and a C<many_to_many>
1209relationship. The C<many_to_many> relationship is optional, but it
1210makes it easier to map a book to its collection of authors. Without
3b1fa91b 1211it, we would have to "walk" though the C<book_author> table as in
1212C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
a46b474e 1213will see examples on how to use DBIx::Class objects in your code soon,
3b1fa91b 1214but note that because C<$book-E<gt>book_author> can return multiple
1390ef0e 1215authors, we have to use C<first> to display a single author).
3b1fa91b 1216C<many_to_many> allows us to use the shorter C<$book-E<gt>author-
a46b474e 1217E<gt>first-E<gt>last_name>. Note that you cannot define a
1218C<many_to_many> relationship without also having the C<has_many>
1219relationship in place.
3533daff 1220
3b1fa91b 1221Then edit C<lib/MyApp/Schema/Result/> and add relationship
3533daff 1222information as follows (again, be careful to put in above the C<1;> but
1223below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1225 #
1226 # Set relationships:
1227 #
1229 # has_many():
1230 # args:
4d63a0d5 1231 # 1) Name of relationship, DBIC will create an accessor with this name
3533daff 1232 # 2) Name of the model class referenced by this relationship
1435672d 1233 # 3) Column name in *foreign* table (aka, foreign key in peer table)
fce83e5f 1234 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthor', 'author_id');
3533daff 1235
1236 # many_to_many():
1237 # args:
1238 # 1) Name of relationship, DBIC will create accessor with this name
1239 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1240 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1241 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1242 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
3533daff 1243
1390ef0e 1244Finally, do the same for the "join table,"
3b1fa91b 1245C<lib/MyApp/Schema/Result/>:
3533daff 1246
1247 #
1248 # Set relationships:
1249 #
1251 # belongs_to():
1252 # args:
1253 # 1) Name of relationship, DBIC will create accessor with this name
1254 # 2) Name of the model class referenced by this relationship
1255 # 3) Column name in *this* table
3b1fa91b 1256 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Book', 'book_id');
3533daff 1257
1258 # belongs_to():
1259 # args:
1260 # 1) Name of relationship, DBIC will create accessor with this name
1261 # 2) Name of the model class referenced by this relationship
1262 # 3) Column name in *this* table
3b1fa91b 1263 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Author', 'author_id');
3533daff 1264
1390ef0e 1266=head2 Run The Application
3533daff 1267
4d63a0d5 1268Run the Catalyst development server script with the C<DBIC_TRACE> option
1269(it might still be enabled from earlier in the tutorial, but here is an
1270alternate way to specify the option just in case):
3533daff 1271
1272 $ DBIC_TRACE=1 script/
1390ef0e 1274Make sure that the application loads correctly and that you see the
1275three dynamically created model class (one for each of the
4ab6212d 1276Result Classes we created).
3533daff 1277
acbd7bdd 1278Then hit the URL L<http://localhost:3000/books/list> with your browser
1279and be sure that the book list is displayed via the relationships
1280established above. You can leave the development server running for
1281the next step if you wish.
3533daff 1282
c2dfb562 1283B<Note:> You will not see the authors yet because the view does not yet
1284use the new relations. Read on to the next section where we update the
1285template to do that.
3533daff 1286
acbd7bdd 1290Let's add a new column to our book list page that takes advantage of
1291the relationship information we manually added to our schema files in
a46b474e 1292the previous section. Edit C<root/src/books/list.tt2> and replace
3b1fa91b 1293the "empty" table cell "<td></td>" with the following:
3533daff 1294
acbd7bdd 1295 ...
3533daff 1296 <td>
fce83e5f 1297 [% # NOTE: See Chapter 4 for a better way to do this! -%]
3533daff 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 -%]
6d97b973 1300 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
3533daff 1301 [% # a value, so nothing will be printed here. But, if you have something -%]
6d97b973 1302 [% # in TT that does return a value and you don't want it printed, you -%]
1303 [% # 1) assign it to a bogus value, or -%]
1304 [% # 2) use the CALL keyword to call it and discard the return value. -%]
3533daff 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
fce83e5f 1315B<IMPORTANT NOTE:> You should keep as much "logic code" as possible
1316out of your views. Instead, this kind of logic belongs in your model
1317(the same goes for controllers -- keep them as "thin" as possible and
1318push all of the "complicated code" out to your model objects). Avoid
1319code like you see in the previous example -- we are only using it here
1320to show some extra features in TT until we get to the more advanced
1321model features we will see in Chapter 4 (see
1322L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1390ef0e 1324Then hit "Reload" in your browser (note that you don't need to reload
3533daff 1325the development server or use the C<-r> option when updating TT
1390ef0e 1326templates) and you should now see the number of authors each book has
1327along with a comma-separated list of the authors' last names. (If you
1328didn't leave the development server running from the previous step,
1329you will obviously need to start it before you can refresh your
1330browser window.)
1332If you are still running the development server with C<DBIC_TRACE>
1333enabled, you should also now see five more C<SELECT> statements in the
1334debug output (one for each book as the authors are being retrieved by
a46b474e 1335DBIx::Class):
3533daff 1336
fce83e5f 1337 SELECT, me.title, me.rating FROM book me:
3b1fa91b 1338 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1339 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '1'
3b1fa91b 1340 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1341 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '2'
3b1fa91b 1342 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1343 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '3'
3b1fa91b 1344 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1345 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '4'
3b1fa91b 1346 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1347 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '5'
c2dfb562 1348
1349Also note in C<root/src/books/list.tt2> that we are using "| html", a
1350type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1351and &gt; and avoid various types of dangerous hacks against your
1352application. In a real application, you would probably want to put
1353"| html" at the end of every field where a user has control over the
1354information that can appear in that field (and can therefore inject
1355markup or code if you don't "neutralize" those fields). In addition to
1356"| html", Template Toolkit has a variety of other useful filters that
1357can found in the documentation for
3533daff 1359
1363In some situations, it can be useful to run your application and
1364display a page without using a browser. Catalyst lets you do this
1365using the C<scripts/> script. Just supply the URL you
1366wish to display and it will run that request through the normal
1367controller dispatch logic and use the appropriate view to render the
1368output (obviously, complex pages may dump a lot of text to your
1369terminal window). For example, if you type:
1371 $ script/ "/books/list"
1373You should get the same text as if you visited
1374L<http://localhost:3000/books/list> with the normal development server
1375and asked your browser to view the page source.
3533daff 1376
1390ef0e 1377
4b4d3884 1380B<NOTE: The rest of this chapter of the tutorial is optional. You can
3ab6187c 1381skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
3533daff 1382if you wish.>
acbd7bdd 1384
8a472b34 1385=head2 Using 'RenderView' for the Default View
1390ef0e 1386
1387Once your controller logic has processed the request from a user, it
1388forwards processing to your view in order to generate the appropriate
3533daff 1389response output. Catalyst uses
1390ef0e 1390L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
4d63a0d5 1391default to automatically perform this operation. If you look in
1390ef0e 1392C<lib/MyApp/Controller/>, you should see the empty
3533daff 1393definition for the C<sub end> method:
1395 sub end : ActionClass('RenderView') {}
1390ef0e 1397The following bullet points provide a quick overview of the
3533daff 1398C<RenderView> process:
1400=over 4
1402=item *
1404C<> is designed to hold application-wide logic.
1406=item *
1390ef0e 1408At the end of a given user request, Catalyst will call the most specific
1409C<end> method that's appropriate. For example, if the controller for a
1410request has an C<end> method defined, it will be called. However, if
1411the controller does not define a controller-specific C<end> method, the
3533daff 1412"global" C<end> method in C<> will be called.
1414=item *
1416Because the definition includes an C<ActionClass> attribute, the
1417L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1418will be executed B<after> any code inside the definition of C<sub end>
1419is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1420for more information on C<ActionClass>.
1422=item *
1390ef0e 1424Because C<sub end> is empty, this effectively just runs the default
1425logic in C<RenderView>. However, you can easily extend the
1426C<RenderView> logic by adding your own code inside the empty method body
1427(C<{}>) created by the Catalyst Helpers when we first ran the
1428C<> to initialize our application. See
1429L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
4d63a0d5 1430detailed information on how to extend C<RenderView> in C<sub end>.
3533daff 1431
fce83e5f 1435=head2 RenderView's "dump_info" Feature
1437One of the nice features of C<RenderView> is that it automatically
1438allows you to add C<dump_info=1> to the end of any URL for your
1439application and it will force the display of the "exception dump"
1440screen to the client browser. You can try this out by starting the
1441development server as before and then point your browser to this URL:
1443 http://localhost:3000/books/list?dump_info=1
1445You should get a page with the following message at the top:
1447 Caught exception in MyApp::Controller::Root->end "Forced debug -
1448 Scrubbed output at /usr/share/perl5/Catalyst/Action/ line 46."
1450Along with a summary of your application's state at the end of the
1451processing for that request. The "Stash" section should show a
1452summarized version of the DBIC book model objects. If desired, you
1453can adjust the summarization logic (called "scrubbing" logic) -- see
1454L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for
1457Note that you shouldn't need to worry about "normal clients" using
1458this technique to "reverse engineer" your application -- C<RenderView>
1459only supports the C<dump_info=1> feature when your application is
1460running in C<-Debug> mode (something you won't do once you have your
1461application deployed in production).
3533daff 1464=head2 Using The Default Template Name
1390ef0e 1466By default, C<Catalyst::View::TT> will look for a template that uses the
1467same name as your controller action, allowing you to save the step of
1468manually specifying the template name in each action. For example, this
1469would allow us to remove the
1470C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1471C<list> action in the Books controller. Open
3533daff 1472C<lib/MyApp/Controller/> in your editor and comment out this line
1473to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1474has changed):
1476 =head2 list
1478 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1480 =cut
1482 sub list : Local {
1483 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1484 # 'Context' that's used to 'glue together' the various components
1485 # that make up the application
1486 my ($self, $c) = @_;
1488 # Retrieve all of the book records as book model objects and store in the
1489 # stash where they can be accessed by the TT template
3b1fa91b 1490 $c->stash->{books} = [$c->model('DB::Book')->all];
3533daff 1491
1492 # Set the TT template to use. You will almost always want to do this
1493 # in your action methods (actions methods respond to user input in
1494 # your controllers).
1495 #$c->stash->{template} = 'books/list.tt2';
1496 }
3533daff 1498
1390ef0e 1499You should now be able to restart the development server as per the
3533daff 1500previous section and access the L<http://localhost:3000/books/list>
1501as before.
1503B<NOTE:> Please note that if you use the default template technique,
1504you will B<not> be able to use either the C<$c-E<gt>forward> or
4b4d3884 1505the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1506Chapter 9 of the Tutorial).
3533daff 1507
3b1fa91b 1508B<IMPORTANT:> Make sure that you do NOT skip the following section
1509before continuing to the next chapter 4 Basic CRUD.
3533daff 1510
fce83e5f 1511
4d63a0d5 1512=head2 Return To A Manually Specified Template
3533daff 1513
1514In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1515later in the tutorial, you should remove the comment from the
1516statement in C<sub list> in C<lib/MyApp/Controller/>:
1518 $c->stash->{template} = 'books/list.tt2';
1390ef0e 1520Then delete the C<TEMPLATE_EXTENSION> line in
3533daff 1521C<lib/MyApp/View/>.
1390ef0e 1523You should then be able to restart the development server and
3533daff 1524access L<http://localhost:3000/books/list> in the same manner as
1525with earlier sections.
1528=head1 AUTHOR
1530Kennedy Clark, C<>
1532Please report any errors, issues or suggestions to the author. The
1533most recent version of the Catalyst Tutorial can be found at
59884771 1534L<>.
3533daff 1535
45c7830f 1536Copyright 2006-2008, Kennedy Clark, under Creative Commons License
8482d557 1537(L<>).