remove now uneeded reminders to restart the server
[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/"
444d6b27 94 Change to application directory and Run "perl Makefile.PL" to make sure your install is complete
3533daff 95 $ cd MyApp
4b4d3884 97This creates a similar skeletal structure to what we saw in Chapter 2 of
1390ef0e 98the tutorial, except with C<MyApp> and C<myapp> substituted for
444d6b27 99C<Hello> and C<hello>. (As noted in Chapter 2, omit the ".pl" from
100the command if you are using Strawberry Perl.)
3533daff 101
105One of the greatest benefits of Catalyst is that it has such a large
1390ef0e 106library of plugins and base classes available. Plugins are used to
107seamlessly integrate existing Perl modules into the overall Catalyst
108framework. In general, they do this by adding additional methods to the
109C<context> object (generally written as C<$c>) that Catalyst passes to
110every component throughout the framework.
3533daff 111
112By default, Catalyst enables three plugins/flags:
114=over 4
1390ef0e 116=item *
3533daff 117
118C<-Debug> Flag
120Enables the Catalyst debug output you saw when we started the
121C<script/> development server earlier. You can remove
79a529cc 122this item when you place your application into production.
3533daff 123
444d6b27 124To be technically correct, it turns out that C<-Debug> is not a plugin, but a I<flag>.
1390ef0e 125Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
126line of your application class will be plugins, Catalyst supports a
127limited number of flag options (of these, C<-Debug> is the most
128common). See the documentation for C<> to get details on
129other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
3533daff 130
444d6b27 131If you prefer, there are several other ways to enable debug output:
133=over 4
135=item *
137Use the C<$c-E<gt>debug> method
139=item *
141The C<-d> option to C<script/>
143=item *
145The C<CATALYST_DEBUG=1> environment variable (or set it to
146zero to templorarily disable debug output).
3533daff 149
150B<TIP>: Depending on your needs, it can be helpful to permanently
151remove C<-Debug> from C<lib/> and then use the C<-d> option
152to C<script/> to re-enable it just for the development
1390ef0e 153server. We will not be using that approach in the tutorial, but feel
3533daff 154free to make use of it in your own projects.
156=item *
160C<ConfigLoader> provides an automatic way to load configurable
c010ae0d 161parameters for your application from a central
162L<Config::General|Config::General> file (versus having the values
163hard-coded inside your Perl modules). Config::General uses syntax
164very similar to Apache configuration files. We will see how to use
165this feature of Catalyst during the authentication and authorization
4b4d3884 166sections (Chapter 5 and Chapter 6).
3533daff 167
1435672d 168B<IMPORTANT NOTE:> If you are using a version of
169L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, be aware
170that Catalyst changed the default format from YAML to the more
171straightforward C<Config::General> style. This tutorial uses the
172newer C<myapp.conf> file for C<Config::General>. However, Catalyst
173supports both formats and will automatically use either C<myapp.conf>
174or C<myapp.yml> (or any other format supported by
175L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
176L<Config::Any|Config::Any>). If you are using a version of
177Catalyst::Devel prior to 1.06, you can convert to the newer format by
178simply creating the C<myapp.conf> file manually and deleting
179C<myapp.yml>. The default contents of the C<myapp.conf> you create
180should only consist of one line:
182 name MyApp
15e1d0b2 183
1390ef0e 184B<TIP>: This script can be useful for converting between configuration
15e1d0b2 185formats:
1390ef0e 187 perl -Ilib -e 'use MyApp; use Config::General;
15e1d0b2 188 Config::General->new->save_file("myapp.conf", MyApp->config);'
3533daff 190=item *
4d63a0d5 194C<Static::Simple> provides an easy way to serve static content, such
195as images and CSS files, from the development server.
3533daff 196
94d8da41 199For our application, we want to add one new plugin into the mix. To
1390ef0e 200do this, edit C<lib/> (this file is generally referred to as
acbd7bdd 201your I<application class>) and delete the lines with:
3533daff 202
acbd7bdd 203 use Catalyst qw/-Debug
204 ConfigLoader
205 Static::Simple/;
3533daff 206
1390ef0e 207Then replace it with:
b411df01 208
acbd7bdd 209 # Load plugins
fce83e5f 210 use Catalyst qw/
211 -Debug
3b1fa91b 212 ConfigLoader
213 Static::Simple
acbd7bdd 214
3b1fa91b 215 StackTrace
216 /;
1390ef0e 217
94d8da41 218B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
acbd7bdd 219techniques to load these plugins/flags. For example, you might see
220the following:
94d8da41 221
acbd7bdd 222 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
94d8da41 223
224Don't let these variations confuse you -- they all accomplish the same
1390ef0e 227This tells Catalyst to start using one new plugin,
228L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
229stack trace to the standard Catalyst "debug screen" (the screen
230Catalyst sends to your browser when an error occurs). Be aware that
231L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
232browser, not in the console window from which you're running your
233application, which is where logging output usually goes.
3533daff 234
444d6b27 235Make sure when adding new plugins you also include them as a new
c12b0d35 236dependency within the Makefile.PL file. For example, after adding
3b1fa91b 237the StackTrace plugin the Makefile.PL should include the following
240 requires 'Catalyst::Plugin::StackTrace';
1390ef0e 243B<Notes:>
3533daff 244
245=over 4
1390ef0e 247=item *
249C<__PACKAGE__> is just a shorthand way of referencing the name of the
250package where it is used. Therefore, in C<>, C<__PACKAGE__>
251is equivalent to C<MyApp>.
3533daff 252
1390ef0e 253=item *
3533daff 254
1390ef0e 255You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
256before you put your application into production, but it can be helpful
257during development.
3533daff 258
1390ef0e 259=item *
3533daff 260
444d6b27 261When specifying plugins, you can omit C<Catalyst::Plugin::> from the
262name. Additionally, you can spread the plugin names across multiple
263lines as shown here or place them all on one line.
cca5cd98 264
3533daff 265=back
3533daff 267
1390ef0e 270As discussed earlier, controllers are where you write methods that
271interact with user input. Typically, controller methods respond to
4d63a0d5 272C<GET> and C<POST> requests from the user's web browser.
3533daff 273
274Use the Catalyst C<create> script to add a controller for book-related
277 $ script/ controller Books
278 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
279 exists "/home/me/MyApp/script/../t"
280 created "/home/me/MyApp/script/../lib/MyApp/Controller/"
281 created "/home/me/MyApp/script/../t/controller_Books.t"
4b4d3884 283Then edit C<lib/MyApp/Controller/> (as discussed in Chapter 2 of
1390ef0e 284the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
285each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
286and add the following method to the controller:
3533daff 287
288 =head2 list
290 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
292 =cut
1390ef0e 293
3533daff 294 sub list : Local {
295 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
296 # 'Context' that's used to 'glue together' the various components
297 # that make up the application
298 my ($self, $c) = @_;
300 # Retrieve all of the book records as book model objects and store in the
301 # stash where they can be accessed by the TT template
3b1fa91b 302 # $c->stash->{books} = [$c->model('DB::Book')->all];
1390ef0e 303 # But, for now, use this code until we create the model later
304 $c->stash->{books} = '';
3533daff 306 # Set the TT template to use. You will almost always want to do this
307 # in your action methods (action methods respond to user input in
308 # your controllers).
309 $c->stash->{template} = 'books/list.tt2';
310 }
1390ef0e 312B<TIP>: See Appendix 1 for tips on removing the leading spaces when
313cutting and pasting example code from POD-based documents.
3533daff 314
1390ef0e 315Programmers experienced with object-oriented Perl should recognize
316C<$self> as a reference to the object where this method was called.
317On the other hand, C<$c> will be new to many Perl programmers who have
318not used Catalyst before (it's sometimes written as C<$context>). The
319Context object is automatically passed to all Catalyst components. It
320is used to pass information between components and provide access to
321Catalyst and plugin functionality.
3533daff 322
245b41d1 323Catalyst actions are regular Perl methods, but they make use of
324attributes (the "C<: Local>" next to the "C<sub list>" in the code
0416017e 325above) to provide additional information to the Catalyst dispatcher
326logic (note that the space between the colon and the attribute name is
4d63a0d5 327optional; you will see attributes written both ways). Most Catalyst
245b41d1 328Controllers use one of five action types:
0416017e 329
330=over 4
332=item *
245b41d1 334B<:Private> -- Use C<:Private> for methods that you want to make into
444d6b27 335an action, but you do not want Catalyst to directly expose the method
245b41d1 336to your users. Catalyst will not map C<:Private> methods to a URI.
337Use them for various sorts of "special" methods (the C<begin>,
338C<auto>, etc. discussed below) or for methods you want to be able to
339C<forward> or C<detach> to. (If the method is a plain old "helper
340method" that you don't want to be an action at all, then just define
341the method without any attribute -- you can call it in your code, but
342the Catalyst dispatcher will ignore it.)
0416017e 343
245b41d1 344There are five types of "special" build-in C<:Private> actions:
345C<begin>, C<end>, C<default>, C<index>, and C<auto>.
0416017e 346
26c9cad5 347=over 4
0416017e 349=item *
351With C<begin>, C<end>, C<default>, C<index> private actions, only the
352most specific action of each type will be called. For example, if you
353define a C<begin> action in your controller it will I<override> a
354C<begin> action in your application/root controller -- I<only> the
355action in your controller will be called.
357=item *
359Unlike the other actions where only a single method is called for each
360request, I<every> auto action along the chain of namespaces will be
361called. Each C<auto> action will be called I<from the application/root
362controller down through the most specific class>.
366=item *
245b41d1 368B<:Path> -- C<:Path> actions let you map a method to an explicit URI
369path. For example, "C<:Path('list')>" in
0416017e 370C<lib/MyApp/Controller/> would match on the URL
444d6b27 371C<http://localhost:3000/books/list>, but "C<:Path('/list')>" would
372match on C<http://localhost:3000/list> (because of the leading slash).
373You can use C<:Args()> to specify how many arguments an action should
374accept. See L<Catalyst::Manual::Intro/Action_types> for more
375information and examples.
0416017e 376
377=item *
245b41d1 379B<:Local> -- C<:Local> is merely a shorthand for
380"C<:Path('_name_of_method_')>". For example, these are equivalent:
381"C<sub create_book :Local {...}>" and
382"C<sub create_book :Path('create_book') {...}>".
384=item *
386B<:Global> -- C<:Global> is merely a shorthand for
387"C<:Path('/_name_of_method_')>". For example, these are equivalent:
388"C<sub create_book :Global {...}>" and
389"C<sub create_book :Path('/create_book') {...}>".
391=item *
393B<:Chained> -- Newer Catalyst applications tend to use the Chained
0416017e 394dispatch form of action types because of its power and flexibility.
4d63a0d5 395It allows a series of controller methods to be automatically dispatched
0416017e 396to service a single user request. See
3ab6187c 397L<Catalyst::Manual::Tutorial::04_BasicCRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
0416017e 398and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
399for more information on chained actions.
403You should refer to L<Catalyst::Manual::Intro/Action_types> for
404additional information and for coverage of some lesser-used action
245b41d1 405types not discussed here (C<Regex> and C<LocalRegex>).
3533daff 406
4d63a0d5 410As mentioned in Chapter 2 of the tutorial, views are where you render
411output, typically for display in the user's web browser (but also
412possibly using into output-generation systems, such as PDF or JSON).
413The code in C<lib/MyApp/View> selects the I<type> of view to use, with
414the actual rendering template found in the C<root> directory. As with
415virtually every aspect of Catalyst, options abound when it comes to the
416specific view technology you adopt inside your application. However,
417most Catalyst applications use the Template Toolkit, known as TT (for
418more information on TT, see L<>). Other
419somewhat popular view technologies include Mason
420(L<> and L<>) and
1390ef0e 421L<HTML::Template> (L<>).
424=head2 Create a Catalyst View
3533daff 425
444d6b27 426When using TT for the Catalyst view, the main helper script
427is L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>.
428You may also come across references to
430but its use is now deprecated.
1390ef0e 431
432Enter the following command to enable the C<TT> style of view
3533daff 433rendering for this tutorial:
1390ef0e 435 $ script/ view TT TT
3533daff 436 exists "/home/me/MyApp/script/../lib/MyApp/View"
437 exists "/home/me/MyApp/script/../t"
1390ef0e 438 created "/home/me/MyApp/script/../lib/MyApp/View/"
439 created "/home/me/MyApp/script/../t/view_TT.t"
3533daff 440
1390ef0e 441This simply creates a view called C<TT> (the second 'TT' argument) in
442a file called C<> (the first 'TT' argument). It is now up to you
443to decide how you want to structure your view layout. For the
444tutorial, we will start with a very simple TT template to initially
445demonstrate the concepts, but quickly migrate to a more typical
446"wrapper page" type of configuration (where the "wrapper" controls the
447overall "look and feel" of your site from a single file or set of
3533daff 449
1390ef0e 450Edit C<lib/MyApp/View/> and you should see that the default
451contents contains something similar to the following:
3533daff 452
1390ef0e 453 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
3533daff 454
1390ef0e 455And update it to match:
457 __PACKAGE__->config(
458 # Change default TT extension
460 # Set the location for TT files
6abd3023 462 MyApp->path_to( 'root', 'src' ),
1390ef0e 463 ],
464 );
3533daff 465
1390ef0e 466B<NOTE:> Make sure to add a comma after '.tt2' outside the single
444d6b27 469This changes the default extension for Template Toolkit from '.tt' to
470'.tt2' and changes the base directory for your template files from
471C<root> to C<root/src>. Stick with these conventions for the
472tutorial, but feel free to use whatever options you desire in your
473applications (as with most things Perl, there's more than one way to
474do it...).
1390ef0e 475
acbd7bdd 476B<Note:> We will use C<root/src> as the base directory for our
444d6b27 477template files, with a full naming convention of
acbd7bdd 478C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
479use C<root/> as the base (with a full filename pattern of
1390ef0e 482
483=head2 Create a TT Template Page
3533daff 484
485First create a directory for book-related TT templates:
1390ef0e 487 $ mkdir -p root/src/books
3533daff 488
489Then create C<root/src/books/list.tt2> in your editor and enter:
491 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
492 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
493 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
494 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
1390ef0e 496 [% # Provide a title -%]
3533daff 497 [% META title = 'Book List' -%]
499 <table>
500 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
501 [% # Display each book in a table row %]
502 [% FOREACH book IN books -%]
503 <tr>
504 <td>[% book.title %]</td>
505 <td>[% book.rating %]</td>
a46b474e 506 <td></td>
3533daff 507 </tr>
508 [% END -%]
509 </table>
511As indicated by the inline comments above, the C<META title> line uses
1390ef0e 512TT's META feature to provide a title to the "wrapper" that we will
513create later. Meanwhile, the C<FOREACH> loop iterates through each
514C<book> model object and prints the C<title> and C<rating> fields.
3533daff 515
4d63a0d5 516The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
517supports a wide variety of directives for "calling" other files,
518looping, conditional logic, etc. In general, TT simplifies the usual
444d6b27 519range of Perl operators down to the single dot (".") operator. This
4d63a0d5 520applies to operations as diverse as method calls, hash lookups, and list
521index values (see
522L<> for
444d6b27 523details and examples). In addition to the usual L<Template> module Pod
4d63a0d5 524documentation, you can access the TT manual at
55beb65d 525L<>.
3533daff 526
444d6b27 527B<TIP:> While you can build all sorts of complex logic into your TT
528templates, you should in general keep the "code" part of your
529templates as simple as possible. If you need more complex logic,
530create helper methods in your model that abstract out a set of code
531into a single call from your TT template. (Note that the same is true
532of your controller logic as well -- complex sections of code in your
533controllers should often be pulled out and placed into your model
534objects.) In Chapter 4 of the tutorial we will explore some extremely
535helpful and powerful features of L<DBIx::Class> that allow you to pull
536code out of your views and controllers and place it where it
537rightfully belongs in a model class.
1390ef0e 538
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
fce83e5f 556the L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> chapter of the
1390ef0e 557tutorial.
3533daff 558
562In this step, we make a text file with the required SQL commands to
429e7843 563create a database table and load some sample data. We will use
9887a877 564SQLite (L<>), a popular database that is
429e7843 565lightweight and easy to use. Be sure to get at least version 3. Open
1390ef0e 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
6290bf87 652is because the default inflection code for L<DBIx::Class::Schema::Loader>
3b1fa91b 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
6290bf87 658option. See L<DBIx::Class::Schema::Loader> for more information.
3b1fa91b 659
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>
444d6b27 668can be used to access databases through the traditional Perl L<DBI>
27909ed4 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"'
a467a714 694 0.31
27909ed4 695
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
a467a714 700You should have version 0.31 or greater if you are following along
444d6b27 701with Debian 5. In other environments, you may need to run this
702command to install it directly from CPAN:
27909ed4 703
704 $ sudo cpan Catalyst::Model::DBIC::Schema
706And re-run the version print command to verify that you are now at
a467a714 7070.31 or higher.
27909ed4 708
a46b474e 710=head2 Create Static DBIx::Class Schema Files
27909ed4 711
98fd8420 712Before you continue, make sure your C<myapp.db> database file is in
713the application's topmost directory. Now use the model helper with
714the C<create=static> option to read the database with
27909ed4 715L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
716automatically build the required files for us:
3533daff 717
4ab6212d 718 $ script/ model DB DBIC::Schema MyApp::Schema \
fce83e5f 719 create=static dbi:SQLite:myapp.db
1390ef0e 720 exists "/home/me/MyApp/script/../lib/MyApp/Model"
721 exists "/home/me/MyApp/script/../t"
27909ed4 722 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
723 Schema dump completed.
1390ef0e 724 created "/home/me/MyApp/script/../lib/MyApp/Model/"
725 created "/home/me/MyApp/script/../t/model_DB.t"
3533daff 726
fce83e5f 727Please note the '\' above. Depending on your environment, you might
728be able to cut and paste the text as shown or need to remove the '\'
729character to that the command is all on a single line.
3b1fa91b 730
27909ed4 731The C<script/> command breaks down like this:
733=over 4
735=item *
737C<DB> is the name of the model class to be created by the helper in
740=item *
742C<DBIC::Schema> is the type of the model to create.
744=item *
746C<MyApp::Schema> is the name of the DBIC schema file written to
749=item *
751C<create=static> causes
752L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
753load the schema as it runs and then write that information out
754into files.
756=item *
27909ed4 758And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
759for use with SQLite.
763If you look in the C<lib/MyApp/> file, you will find that it
764only contains a call to the C<load_namespaces> method. You will also
765find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
766has a subdirectory called "Result". This "Result" subdirectory then
767has files named according to each of the tables in our simple database
3b1fa91b 768(C<>, C<>, and C<>). These three
a46b474e 769files are called "Result Classes" in DBIx::Class nomenclature. Although the
27909ed4 770Result Class files are named after tables in our database, the classes
771correspond to the I<row-level data> that is returned by DBIC (more on
772this later, especially in
3ab6187c 773L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
27909ed4 774
775The idea with the Result Source files created under
776C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
777edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
778warning. If you place all of your changes below that point in the
779file, you can regenerate the automatically created information at the
780top of each file should your database structure get updated.
782Also note the "flow" of the model information across the various files
783and directories. Catalyst will initially load the model from
784C<lib/MyApp/Model/>. This file contains a reference to
785C<lib/MyApp/>, so that file is loaded next. Finally, the
786call to C<load_namespaces> in C<> will load each of the
787"Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
788The final outcome is that Catalyst will dynamically create three
789table-specific Catalyst models every time the application starts (you
790can see these three model files listed in the debug output generated
791when you launch the application).
793B<NOTE:> Older versions of
794L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
a46b474e 795deprecated DBIx::Class C<load_classes> technique instead of the newer
27909ed4 796C<load_namspaces>. For new applications, please try to use
797C<load_namespaces> since it more easily supports a very useful DBIC
798technique called "ResultSet Classes." If you need to convert an
799existing application from "load_classes" to "load_namespaces," you can
800use this process to automate the migration (but first make sure you
801have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
803 $ # First delete the existing schema file to disable "compatibility" mode
804 $ rm lib/MyApp/
805 $
806 $ # Then re-run the helper to build the files for "load_namespaces"
807 $ script/ model DB DBIC::Schema MyApp::Schema \
fce83e5f 808 create=static dbi:SQLite:myapp.db
3b1fa91b 809 $
27909ed4 810 $ # Now convert the existing files over
811 $ cd lib/MyApp/Schema
812 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
813 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
814 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
815 $ cd ../../..
816 $
817 $ # And finally delete the old files
818 $ rm lib/MyApp/Schema/*.pm
820The "C<perl -MIO::ALL ...>" script will copy all the customized
821relationship (and other) information below "C<# DO NOT MODIFY>" line
822from the old files in C<lib/MyApp/Schema> to the new files in
823C<lib/MyApp/Schema/Result> (we will be starting to add some
824"customized relationship information in the section below).
3533daff 825
dc9a0503 826
acbd7bdd 829Open C<lib/MyApp/Controller/> and un-comment the model code we
830left disabled earlier so that your version matches the following (un-
3b1fa91b 831comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
acbd7bdd 832and delete the next 2 lines):
1390ef0e 833
834 =head2 list
836 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
838 =cut
840 sub list : Local {
841 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
842 # 'Context' that's used to 'glue together' the various components
843 # that make up the application
844 my ($self, $c) = @_;
846 # Retrieve all of the book records as book model objects and store in the
847 # stash where they can be accessed by the TT template
3b1fa91b 848 $c->stash->{books} = [$c->model('DB::Book')->all];
1390ef0e 849
850 # Set the TT template to use. You will almost always want to do this
851 # in your action methods (action methods respond to user input in
852 # your controllers).
853 $c->stash->{template} = 'books/list.tt2';
854 }
3b1fa91b 856B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
857above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
c93b5eaa 858two are equivalent. Either way, C<$c-E<gt>model> returns a
859L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
4d63a0d5 860against the database and iterating over the set of results that is
c93b5eaa 861returned.
863We are using the C<-E<gt>all> to fetch all of the books. DBIC
864supports a wide variety of more advanced operations to easily do
865things like filtering and sorting the results. For example, the
518f3851 866following could be used to sort the results by descending title:
c93b5eaa 867
3b1fa91b 868 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
c93b5eaa 869
870Some other examples are provided in
871L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
872additional information found at L<DBIx::Class::ResultSet/search>,
875and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
1390ef0e 876
878=head2 Test Run The Application
3533daff 879
1435672d 880First, let's enable an environment variable that causes DBIx::Class to
acbd7bdd 881dump the SQL statements used to access the database. This is a
1435672d 882helpful trick when you are trying to debug your database-oriented
3533daff 884
885 $ export DBIC_TRACE=1
4d63a0d5 887This assumes you are using bash as your shell -- adjust accordingly if
3533daff 888you are using a different shell (for example, under tcsh, use
889C<setenv DBIC_TRACE 1>).
d0496197 891B<NOTE:> You can also set this in your code using
3533daff 892C<$class-E<gt>storage-E<gt>debug(1);>. See
893L<DBIx::Class::Manual::Troubleshooting> for details (including options
4d63a0d5 894to log to a file instead of displaying to the Catalyst development server
3533daff 895log).
1390ef0e 897Then launch the Catalyst development server. The log output should
898display something like:
3533daff 899
acbd7bdd 900 $ script/
3533daff 901 [debug] Debug messages enabled
1390ef0e 902 [debug] Statistics enabled
3533daff 903 [debug] Loaded plugins:
904 .----------------------------------------------------------------------------.
a467a714 905 | Catalyst::Plugin::ConfigLoader 0.27 |
906 | Catalyst::Plugin::StackTrace 0.11 |
907 | Catalyst::Plugin::Static::Simple 0.25 |
3533daff 908 '----------------------------------------------------------------------------'
910 [debug] Loaded dispatcher "Catalyst::Dispatcher"
911 [debug] Loaded engine "Catalyst::Engine::HTTP"
912 [debug] Found home "/home/me/MyApp"
45d511e0 913 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
3533daff 914 [debug] Loaded components:
915 .-----------------------------------------------------------------+----------.
916 | Class | Type |
917 +-----------------------------------------------------------------+----------+
918 | MyApp::Controller::Books | instance |
919 | MyApp::Controller::Root | instance |
d0496197 920 | MyApp::Model::DB | instance |
3b1fa91b 921 | MyApp::Model::DB::Author | class |
922 | MyApp::Model::DB::Book | class |
923 | MyApp::Model::DB::BookAuthor | class |
3533daff 924 | MyApp::View::TT | instance |
925 '-----------------------------------------------------------------+----------'
927 [debug] Loaded Private actions:
928 .----------------------+--------------------------------------+--------------.
929 | Private | Class | Method |
930 +----------------------+--------------------------------------+--------------+
931 | /default | MyApp::Controller::Root | default |
932 | /end | MyApp::Controller::Root | end |
1390ef0e 933 | /index | MyApp::Controller::Root | index |
3533daff 934 | /books/index | MyApp::Controller::Books | index |
935 | /books/list | MyApp::Controller::Books | list |
936 '----------------------+--------------------------------------+--------------'
938 [debug] Loaded Path actions:
939 .-------------------------------------+--------------------------------------.
940 | Path | Private |
941 +-------------------------------------+--------------------------------------+
1390ef0e 942 | / | /default |
943 | / | /index |
944 | /books | /books/index |
3533daff 945 | /books/list | /books/list |
946 '-------------------------------------+--------------------------------------'
a467a714 948 [info] MyApp powered by Catalyst 5.80013
acbd7bdd 949 You can connect to your server at http://debian:3000
3533daff 950
1390ef0e 951B<NOTE:> Be sure you run the C<script/> command from
952the 'base' directory of your application, not inside the C<script>
953directory itself or it will not be able to locate the C<myapp.db>
954database file. You can use a fully qualified or a relative path to
955locate the database file, but we did not specify that when we ran the
3533daff 956model helper earlier.
958Some things you should note in the output above:
960=over 4
1390ef0e 962=item *
3533daff 963
1390ef0e 964Catalyst::Model::DBIC::Schema dynamically created three model classes,
965one to represent each of the three tables in our database
3b1fa91b 966(C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
967and C<MyApp::Model::DB::Book>).
3533daff 968
1390ef0e 969=item *
3533daff 970
971The "list" action in our Books controller showed up with a path of
976Point your browser to L<http://localhost:3000> and you should still get
977the Catalyst welcome page.
979Next, to view the book list, change the URL in your browser to
980L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 981books loaded by the C<myapp01.sql> script above without any formatting.
982The rating for each book should appear on each row, but the "Author(s)"
191dee29 983column will still be blank (we will fill that in later).
3533daff 984
a46b474e 985Also notice in the output of the C<script/> that
986DBIx::Class used the following SQL to retrieve the data:
3533daff 987
fce83e5f 988 SELECT, me.title, me.rating FROM book me
3533daff 989
990because we enabled DBIC_TRACE.
0c51850e 992You now have the beginnings of a simple but workable web application.
3533daff 993Continue on to future sections and we will develop the application
994more fully.
1390ef0e 997=head1 CREATE A WRAPPER FOR THE VIEW
acbd7bdd 999When using TT, you can (and should) create a wrapper that will
1390ef0e 1000literally wrap content around each of your templates. This is
1001certainly useful as you have one main source for changing things that
1002will appear across your entire site/application instead of having to
1003edit many individual files.
1006=head2 Configure For The Wrapper
1008In order to create a wrapper, you must first edit your TT view and
444d6b27 1009tell it where to find your wrapper file.
1390ef0e 1010
444d6b27 1011Edit you TT view in C<lib/MyApp/View/> and change it to match the
1390ef0e 1013
1014 __PACKAGE__->config(
1015 # Change default TT extension
1016 TEMPLATE_EXTENSION => '.tt2',
1017 # Set the location for TT files
1018 INCLUDE_PATH => [
c2dfb562 1019 MyApp->path_to( 'root', 'src' ),
1390ef0e 1020 ],
1021 # Set to 1 for detailed timer stats in your HTML as comments
1022 TIMER => 0,
1023 # This is your wrapper template located in the 'root/src'
1024 WRAPPER => 'wrapper.tt2',
1025 );
1028=head2 Create the Wrapper Template File and Stylesheet
1030Next you need to set up your wrapper template. Basically, you'll want
1031to take the overall layout of your site and put it into this file.
1032For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1034 <?xml version="1.0" encoding="UTF-8"?>
1035 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "">
1036 <html xmlns="" xml:lang="en" lang="en">
1037 <head>
1038 <title>[% template.title or "My Catalyst App!" %]</title>
1039 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1040 </head>
1042 <body>
1043 <div id="outer">
1044 <div id="header">
1045 [%# Your logo could go here -%]
1046 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1047 [%# Insert the page title -%]
1048 <h1>[% template.title or site.title %]</h1>
1049 </div>
1051 <div id="bodyblock">
1052 <div id="menu">
1053 Navigation:
1054 <ul>
1055 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1056 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1390ef0e 1057 </ul>
1058 </div><!-- end menu -->
1060 <div id="content">
1061 [%# Status and error messages %]
1062 <span class="message">[% status_msg %]</span>
1063 <span class="error">[% error_msg %]</span>
1064 [%# This is where TT will stick all of your template's contents. -%]
1065 [% content %]
1066 </div><!-- end content -->
1067 </div><!-- end bodyblock -->
1069 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 1070 </div><!-- end outer -->
1390ef0e 1071
1072 </body>
1073 </html>
1075Notice the status and error message sections in the code above:
1077 <span class="status">[% status_msg %]</span>
1078 <span class="error">[% error_msg %]</span>
1080If we set either message in the Catalyst stash (e.g.,
1081C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1082will be displayed whenever any view used by that request is rendered.
1083The C<message> and C<error> CSS styles can be customized to suit your
1084needs in the C<root/static/css/main.css> file we create below.
1088=over 4
1090=item *
1092The Catalyst stash only lasts for a single HTTP request. If
1093you need to retain information across requests you can use
1094L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
4b4d3884 1095Catalyst sessions in the Authentication chapter of the tutorial).
1390ef0e 1096
1097=item *
1099Although it is beyond the scope of this tutorial, you may wish to use
1100a JavaScript or AJAX tool such as jQuery (L<>) or
1101Dojo (L<>).
1106=head3 Create A Basic Stylesheet
1108First create a central location for stylesheets under the static
1111 $ mkdir root/static/css
1113Then open the file C<root/static/css/main.css> (the file referenced in
1114the stylesheet href link of our wrapper above) and add the following
1117 #header {
1118 text-align: center;
1119 }
1120 #header h1 {
1121 margin: 0;
1122 }
1123 #header img {
1124 float: right;
1125 }
1126 #footer {
1127 text-align: center;
1128 font-style: italic;
1129 padding-top: 20px;
1130 }
1131 #menu {
1132 font-weight: bold;
1133 background-color: #ddd;
1134 }
1135 #menu ul {
1136 list-style: none;
1137 float: left;
1138 margin: 0;
1139 padding: 0 0 50% 5px;
1140 font-weight: normal;
1141 background-color: #ddd;
1142 width: 100px;
1143 }
1144 #content {
1145 margin-left: 120px;
1146 }
1147 .message {
1148 color: #390;
1149 }
1150 .error {
1151 color: #f00;
1152 }
1154You may wish to check out a "CSS Framework" like Emastic
1155(L<>) as a way to quickly
1156provide lots of high-quality CSS functionality.
1159=head2 Test Run The Application
1161Restart the development server and hit "Reload" in your web browser
1162and you should now see a formatted version of our basic book list.
1163Although our wrapper and stylesheet are obviously very simple, you
1164should see how it allows us to control the overall look of an entire
1165website from two central files. To add new pages to the site, just
1166provide a template that fills in the C<content> section of our wrapper
1167template -- the wrapper will provide the overall feel of the page.
a46b474e 1170=head2 Updating the Generated DBIx::Class Result Class Files
3533daff 1171
acbd7bdd 1172Let's manually add some relationship information to the auto-generated
1173Result Class files. (Note: if you are using a database other than
1174SQLite, such as PostgreSQL, then the relationship could have been
1175automatically placed in the Result Class files. If so, you can skip
3b1fa91b 1176this step.) First edit C<lib/MyApp/Schema/Result/> and add the
acbd7bdd 1177following text below the C<# You can replace this text...> comment:
3533daff 1178
1179 #
1180 # Set relationships:
1390ef0e 1181 #
3533daff 1182
1183 # has_many():
1184 # args:
1185 # 1) Name of relationship, DBIC will create accessor with this name
1186 # 2) Name of the model class referenced by this relationship
1435672d 1187 # 3) Column name in *foreign* table (aka, foreign key in peer table)
fce83e5f 1188 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthor', 'book_id');
3533daff 1189
1190 # many_to_many():
1191 # args:
1192 # 1) Name of relationship, DBIC will create accessor with this name
1390ef0e 1193 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1194 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1195 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1196 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
3533daff 1197
1199B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1200file. As with any Perl package, we need to end the last line with
1201a statement that evaluates to C<true>. This is customarily done with
1202C<1;> on a line by itself.
a46b474e 1204This code defines both a C<has_many> and a C<many_to_many>
1205relationship. The C<many_to_many> relationship is optional, but it
1206makes it easier to map a book to its collection of authors. Without
3b1fa91b 1207it, we would have to "walk" though the C<book_author> table as in
1208C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
a46b474e 1209will see examples on how to use DBIx::Class objects in your code soon,
3b1fa91b 1210but note that because C<$book-E<gt>book_author> can return multiple
1390ef0e 1211authors, we have to use C<first> to display a single author).
5a82cb36 1212C<many_to_many> allows us to use the shorter
1213C<$book-E<gt>author-E<gt>first-E<gt>last_name>. Note that you cannot
1214define a C<many_to_many> relationship without also having the
1215C<has_many> relationship in place.
3533daff 1216
3b1fa91b 1217Then edit C<lib/MyApp/Schema/Result/> and add relationship
3533daff 1218information as follows (again, be careful to put in above the C<1;> but
1219below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1221 #
1222 # Set relationships:
1223 #
1225 # has_many():
1226 # args:
4d63a0d5 1227 # 1) Name of relationship, DBIC will create an accessor with this name
3533daff 1228 # 2) Name of the model class referenced by this relationship
1435672d 1229 # 3) Column name in *foreign* table (aka, foreign key in peer table)
fce83e5f 1230 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthor', 'author_id');
3533daff 1231
1232 # many_to_many():
1233 # args:
1234 # 1) Name of relationship, DBIC will create accessor with this name
1235 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1236 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1237 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1238 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
3533daff 1239
1390ef0e 1240Finally, do the same for the "join table,"
3b1fa91b 1241C<lib/MyApp/Schema/Result/>:
3533daff 1242
1243 #
1244 # Set relationships:
1245 #
1247 # belongs_to():
1248 # args:
1249 # 1) Name of relationship, DBIC will create accessor with this name
1250 # 2) Name of the model class referenced by this relationship
1251 # 3) Column name in *this* table
3b1fa91b 1252 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Book', 'book_id');
3533daff 1253
1254 # belongs_to():
1255 # args:
1256 # 1) Name of relationship, DBIC will create accessor with this name
1257 # 2) Name of the model class referenced by this relationship
1258 # 3) Column name in *this* table
3b1fa91b 1259 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Author', 'author_id');
3533daff 1260
1390ef0e 1262=head2 Run The Application
3533daff 1263
4d63a0d5 1264Run the Catalyst development server script with the C<DBIC_TRACE> option
1265(it might still be enabled from earlier in the tutorial, but here is an
1266alternate way to specify the option just in case):
3533daff 1267
1268 $ DBIC_TRACE=1 script/
1390ef0e 1270Make sure that the application loads correctly and that you see the
1271three dynamically created model class (one for each of the
4ab6212d 1272Result Classes we created).
3533daff 1273
acbd7bdd 1274Then hit the URL L<http://localhost:3000/books/list> with your browser
444d6b27 1275and be sure that the book list still displays correctly. You can leave
1276the development server running for the next step if you wish.
3533daff 1277
c2dfb562 1278B<Note:> You will not see the authors yet because the view does not yet
1279use the new relations. Read on to the next section where we update the
1280template to do that.
3533daff 1281
acbd7bdd 1285Let's add a new column to our book list page that takes advantage of
1286the relationship information we manually added to our schema files in
a46b474e 1287the previous section. Edit C<root/src/books/list.tt2> and replace
3b1fa91b 1288the "empty" table cell "<td></td>" with the following:
3533daff 1289
acbd7bdd 1290 ...
3533daff 1291 <td>
fce83e5f 1292 [% # NOTE: See Chapter 4 for a better way to do this! -%]
3533daff 1293 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1294 [% # loop in 'side effect notation' to load just the last names of the -%]
6d97b973 1295 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
3533daff 1296 [% # a value, so nothing will be printed here. But, if you have something -%]
6d97b973 1297 [% # in TT that does return a value and you don't want it printed, you -%]
1298 [% # 1) assign it to a bogus value, or -%]
1299 [% # 2) use the CALL keyword to call it and discard the return value. -%]
3533daff 1300 [% tt_authors = [ ];
1301 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1302 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1303 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1304 ([% tt_authors.size | html %])
1305 [% # Use another TT vmethod to join & print the names & comma separators -%]
1306 [% tt_authors.join(', ') | html %]
1307 </td>
acbd7bdd 1308 ...
3533daff 1309
444d6b27 1310B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1311possible out of your views. This kind of logic belongs in your model
fce83e5f 1312(the same goes for controllers -- keep them as "thin" as possible and
1313push all of the "complicated code" out to your model objects). Avoid
1314code like you see in the previous example -- we are only using it here
1315to show some extra features in TT until we get to the more advanced
444d6b27 1316model features we will see in Chapter 4 (see
fce83e5f 1317L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1390ef0e 1319Then hit "Reload" in your browser (note that you don't need to reload
3533daff 1320the development server or use the C<-r> option when updating TT
1390ef0e 1321templates) and you should now see the number of authors each book has
1322along with a comma-separated list of the authors' last names. (If you
1323didn't leave the development server running from the previous step,
1324you will obviously need to start it before you can refresh your
1325browser window.)
1327If you are still running the development server with C<DBIC_TRACE>
1328enabled, you should also now see five more C<SELECT> statements in the
1329debug output (one for each book as the authors are being retrieved by
a46b474e 1330DBIx::Class):
3533daff 1331
fce83e5f 1332 SELECT, me.title, me.rating FROM book me:
3b1fa91b 1333 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1334 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '1'
3b1fa91b 1335 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1336 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '2'
3b1fa91b 1337 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1338 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '3'
3b1fa91b 1339 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1340 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '4'
3b1fa91b 1341 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1342 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '5'
c2dfb562 1343
1344Also note in C<root/src/books/list.tt2> that we are using "| html", a
1345type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1346and &gt; and avoid various types of dangerous hacks against your
1347application. In a real application, you would probably want to put
1348"| html" at the end of every field where a user has control over the
1349information that can appear in that field (and can therefore inject
1350markup or code if you don't "neutralize" those fields). In addition to
1351"| html", Template Toolkit has a variety of other useful filters that
1352can found in the documentation for
3533daff 1354
1358In some situations, it can be useful to run your application and
1359display a page without using a browser. Catalyst lets you do this
1360using the C<scripts/> script. Just supply the URL you
1361wish to display and it will run that request through the normal
1362controller dispatch logic and use the appropriate view to render the
1363output (obviously, complex pages may dump a lot of text to your
1364terminal window). For example, if you type:
1366 $ script/ "/books/list"
1368You should get the same text as if you visited
1369L<http://localhost:3000/books/list> with the normal development server
1370and asked your browser to view the page source.
3533daff 1371
1390ef0e 1372
4b4d3884 1375B<NOTE: The rest of this chapter of the tutorial is optional. You can
3ab6187c 1376skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
3533daff 1377if you wish.>
acbd7bdd 1379
8a472b34 1380=head2 Using 'RenderView' for the Default View
1390ef0e 1381
1382Once your controller logic has processed the request from a user, it
1383forwards processing to your view in order to generate the appropriate
3533daff 1384response output. Catalyst uses
1390ef0e 1385L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
4d63a0d5 1386default to automatically perform this operation. If you look in
1390ef0e 1387C<lib/MyApp/Controller/>, you should see the empty
3533daff 1388definition for the C<sub end> method:
1390 sub end : ActionClass('RenderView') {}
1390ef0e 1392The following bullet points provide a quick overview of the
3533daff 1393C<RenderView> process:
1395=over 4
1397=item *
1399C<> is designed to hold application-wide logic.
1401=item *
1390ef0e 1403At the end of a given user request, Catalyst will call the most specific
1404C<end> method that's appropriate. For example, if the controller for a
1405request has an C<end> method defined, it will be called. However, if
1406the controller does not define a controller-specific C<end> method, the
3533daff 1407"global" C<end> method in C<> will be called.
1409=item *
1411Because the definition includes an C<ActionClass> attribute, the
1412L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1413will be executed B<after> any code inside the definition of C<sub end>
1414is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1415for more information on C<ActionClass>.
1417=item *
1390ef0e 1419Because C<sub end> is empty, this effectively just runs the default
1420logic in C<RenderView>. However, you can easily extend the
1421C<RenderView> logic by adding your own code inside the empty method body
1422(C<{}>) created by the Catalyst Helpers when we first ran the
1423C<> to initialize our application. See
1424L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
4d63a0d5 1425detailed information on how to extend C<RenderView> in C<sub end>.
3533daff 1426
fce83e5f 1430=head2 RenderView's "dump_info" Feature
1432One of the nice features of C<RenderView> is that it automatically
1433allows you to add C<dump_info=1> to the end of any URL for your
1434application and it will force the display of the "exception dump"
1435screen to the client browser. You can try this out by starting the
1436development server as before and then point your browser to this URL:
1438 http://localhost:3000/books/list?dump_info=1
1440You should get a page with the following message at the top:
1442 Caught exception in MyApp::Controller::Root->end "Forced debug -
1443 Scrubbed output at /usr/share/perl5/Catalyst/Action/ line 46."
1445Along with a summary of your application's state at the end of the
1446processing for that request. The "Stash" section should show a
1447summarized version of the DBIC book model objects. If desired, you
1448can adjust the summarization logic (called "scrubbing" logic) -- see
1449L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for
1452Note that you shouldn't need to worry about "normal clients" using
1453this technique to "reverse engineer" your application -- C<RenderView>
1454only supports the C<dump_info=1> feature when your application is
1455running in C<-Debug> mode (something you won't do once you have your
1456application deployed in production).
3533daff 1459=head2 Using The Default Template Name
1390ef0e 1461By default, C<Catalyst::View::TT> will look for a template that uses the
1462same name as your controller action, allowing you to save the step of
1463manually specifying the template name in each action. For example, this
1464would allow us to remove the
1465C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1466C<list> action in the Books controller. Open
3533daff 1467C<lib/MyApp/Controller/> in your editor and comment out this line
1468to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1469has changed):
1471 =head2 list
1473 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1475 =cut
1477 sub list : Local {
1478 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1479 # 'Context' that's used to 'glue together' the various components
1480 # that make up the application
1481 my ($self, $c) = @_;
1483 # Retrieve all of the book records as book model objects and store in the
1484 # stash where they can be accessed by the TT template
3b1fa91b 1485 $c->stash->{books} = [$c->model('DB::Book')->all];
3533daff 1486
1487 # Set the TT template to use. You will almost always want to do this
1488 # in your action methods (actions methods respond to user input in
1489 # your controllers).
1490 #$c->stash->{template} = 'books/list.tt2';
1491 }
3533daff 1493
1390ef0e 1494You should now be able to restart the development server as per the
3533daff 1495previous section and access the L<http://localhost:3000/books/list>
1496as before.
1498B<NOTE:> Please note that if you use the default template technique,
1499you will B<not> be able to use either the C<$c-E<gt>forward> or
4b4d3884 1500the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1501Chapter 9 of the Tutorial).
3533daff 1502
3b1fa91b 1503B<IMPORTANT:> Make sure that you do NOT skip the following section
1504before continuing to the next chapter 4 Basic CRUD.
3533daff 1505
fce83e5f 1506
4d63a0d5 1507=head2 Return To A Manually Specified Template
3533daff 1508
1509In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1510later in the tutorial, you should remove the comment from the
1511statement in C<sub list> in C<lib/MyApp/Controller/>:
1513 $c->stash->{template} = 'books/list.tt2';
1390ef0e 1515Then delete the C<TEMPLATE_EXTENSION> line in
3533daff 1516C<lib/MyApp/View/>.
1390ef0e 1518You should then be able to restart the development server and
3533daff 1519access L<http://localhost:3000/books/list> in the same manner as
1520with earlier sections.
1523=head1 AUTHOR
1525Kennedy Clark, C<>
1527Please report any errors, issues or suggestions to the author. The
1528most recent version of the Catalyst Tutorial can be found at
59884771 1529L<>.
3533daff 1530
45c7830f 1531Copyright 2006-2008, Kennedy Clark, under Creative Commons License
8482d557 1532(L<>).