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[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
1dc333c7 203 use Catalyst qw/
204 -Debug
205 ConfigLoader
206 Static::Simple
207 /;
3533daff 208
1390ef0e 209Then replace it with:
b411df01 210
acbd7bdd 211 # Load plugins
fce83e5f 212 use Catalyst qw/
1dc333c7 213 -Debug
214 ConfigLoader
215 Static::Simple
217 StackTrace
218 /;
1390ef0e 219
94d8da41 220B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
acbd7bdd 221techniques to load these plugins/flags. For example, you might see
222the following:
94d8da41 223
acbd7bdd 224 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
94d8da41 225
226Don't let these variations confuse you -- they all accomplish the same
1390ef0e 229This tells Catalyst to start using one new plugin,
230L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
231stack trace to the standard Catalyst "debug screen" (the screen
232Catalyst sends to your browser when an error occurs). Be aware that
233L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
234browser, not in the console window from which you're running your
235application, which is where logging output usually goes.
3533daff 236
444d6b27 237Make sure when adding new plugins you also include them as a new
c12b0d35 238dependency within the Makefile.PL file. For example, after adding
3b1fa91b 239the StackTrace plugin the Makefile.PL should include the following
242 requires 'Catalyst::Plugin::StackTrace';
1390ef0e 245B<Notes:>
3533daff 246
247=over 4
1390ef0e 249=item *
251C<__PACKAGE__> is just a shorthand way of referencing the name of the
252package where it is used. Therefore, in C<>, C<__PACKAGE__>
253is equivalent to C<MyApp>.
3533daff 254
1390ef0e 255=item *
3533daff 256
1390ef0e 257You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
258before you put your application into production, but it can be helpful
259during development.
3533daff 260
1390ef0e 261=item *
3533daff 262
444d6b27 263When specifying plugins, you can omit C<Catalyst::Plugin::> from the
264name. Additionally, you can spread the plugin names across multiple
265lines as shown here or place them all on one line.
cca5cd98 266
3533daff 267=back
3533daff 269
1390ef0e 272As discussed earlier, controllers are where you write methods that
273interact with user input. Typically, controller methods respond to
4d63a0d5 274C<GET> and C<POST> requests from the user's web browser.
3533daff 275
276Use the Catalyst C<create> script to add a controller for book-related
279 $ script/ controller Books
280 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
281 exists "/home/me/MyApp/script/../t"
282 created "/home/me/MyApp/script/../lib/MyApp/Controller/"
283 created "/home/me/MyApp/script/../t/controller_Books.t"
4b4d3884 285Then edit C<lib/MyApp/Controller/> (as discussed in Chapter 2 of
1390ef0e 286the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
287each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
288and add the following method to the controller:
3533daff 289
290 =head2 list
292 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
294 =cut
1390ef0e 295
3533daff 296 sub list : Local {
297 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
298 # 'Context' that's used to 'glue together' the various components
299 # that make up the application
300 my ($self, $c) = @_;
302 # Retrieve all of the book records as book model objects and store in the
303 # stash where they can be accessed by the TT template
3b1fa91b 304 # $c->stash->{books} = [$c->model('DB::Book')->all];
1390ef0e 305 # But, for now, use this code until we create the model later
306 $c->stash->{books} = '';
3533daff 308 # Set the TT template to use. You will almost always want to do this
309 # in your action methods (action methods respond to user input in
310 # your controllers).
311 $c->stash->{template} = 'books/list.tt2';
312 }
1390ef0e 314B<TIP>: See Appendix 1 for tips on removing the leading spaces when
315cutting and pasting example code from POD-based documents.
3533daff 316
1390ef0e 317Programmers experienced with object-oriented Perl should recognize
318C<$self> as a reference to the object where this method was called.
319On the other hand, C<$c> will be new to many Perl programmers who have
320not used Catalyst before (it's sometimes written as C<$context>). The
321Context object is automatically passed to all Catalyst components. It
322is used to pass information between components and provide access to
323Catalyst and plugin functionality.
3533daff 324
245b41d1 325Catalyst actions are regular Perl methods, but they make use of
326attributes (the "C<: Local>" next to the "C<sub list>" in the code
0416017e 327above) to provide additional information to the Catalyst dispatcher
328logic (note that the space between the colon and the attribute name is
4d63a0d5 329optional; you will see attributes written both ways). Most Catalyst
245b41d1 330Controllers use one of five action types:
0416017e 331
332=over 4
334=item *
245b41d1 336B<:Private> -- Use C<:Private> for methods that you want to make into
444d6b27 337an action, but you do not want Catalyst to directly expose the method
245b41d1 338to your users. Catalyst will not map C<:Private> methods to a URI.
339Use them for various sorts of "special" methods (the C<begin>,
340C<auto>, etc. discussed below) or for methods you want to be able to
341C<forward> or C<detach> to. (If the method is a plain old "helper
342method" that you don't want to be an action at all, then just define
343the method without any attribute -- you can call it in your code, but
344the Catalyst dispatcher will ignore it.)
0416017e 345
245b41d1 346There are five types of "special" build-in C<:Private> actions:
347C<begin>, C<end>, C<default>, C<index>, and C<auto>.
0416017e 348
26c9cad5 349=over 4
0416017e 351=item *
353With C<begin>, C<end>, C<default>, C<index> private actions, only the
354most specific action of each type will be called. For example, if you
355define a C<begin> action in your controller it will I<override> a
356C<begin> action in your application/root controller -- I<only> the
357action in your controller will be called.
359=item *
361Unlike the other actions where only a single method is called for each
362request, I<every> auto action along the chain of namespaces will be
363called. Each C<auto> action will be called I<from the application/root
364controller down through the most specific class>.
368=item *
245b41d1 370B<:Path> -- C<:Path> actions let you map a method to an explicit URI
371path. For example, "C<:Path('list')>" in
0416017e 372C<lib/MyApp/Controller/> would match on the URL
444d6b27 373C<http://localhost:3000/books/list>, but "C<:Path('/list')>" would
374match on C<http://localhost:3000/list> (because of the leading slash).
375You can use C<:Args()> to specify how many arguments an action should
376accept. See L<Catalyst::Manual::Intro/Action_types> for more
377information and examples.
0416017e 378
379=item *
245b41d1 381B<:Local> -- C<:Local> is merely a shorthand for
382"C<:Path('_name_of_method_')>". For example, these are equivalent:
383"C<sub create_book :Local {...}>" and
384"C<sub create_book :Path('create_book') {...}>".
386=item *
388B<:Global> -- C<:Global> is merely a shorthand for
389"C<:Path('/_name_of_method_')>". For example, these are equivalent:
390"C<sub create_book :Global {...}>" and
391"C<sub create_book :Path('/create_book') {...}>".
393=item *
395B<:Chained> -- Newer Catalyst applications tend to use the Chained
0416017e 396dispatch form of action types because of its power and flexibility.
4d63a0d5 397It allows a series of controller methods to be automatically dispatched
0416017e 398to service a single user request. See
3ab6187c 399L<Catalyst::Manual::Tutorial::04_BasicCRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
0416017e 400and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
401for more information on chained actions.
405You should refer to L<Catalyst::Manual::Intro/Action_types> for
406additional information and for coverage of some lesser-used action
245b41d1 407types not discussed here (C<Regex> and C<LocalRegex>).
3533daff 408
4d63a0d5 412As mentioned in Chapter 2 of the tutorial, views are where you render
413output, typically for display in the user's web browser (but also
414possibly using into output-generation systems, such as PDF or JSON).
415The code in C<lib/MyApp/View> selects the I<type> of view to use, with
416the actual rendering template found in the C<root> directory. As with
417virtually every aspect of Catalyst, options abound when it comes to the
418specific view technology you adopt inside your application. However,
419most Catalyst applications use the Template Toolkit, known as TT (for
420more information on TT, see L<>). Other
421somewhat popular view technologies include Mason
422(L<> and L<>) and
1390ef0e 423L<HTML::Template> (L<>).
426=head2 Create a Catalyst View
3533daff 427
444d6b27 428When using TT for the Catalyst view, the main helper script
429is L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>.
430You may also come across references to
432but its use is now deprecated.
1390ef0e 433
434Enter the following command to enable the C<TT> style of view
3533daff 435rendering for this tutorial:
1390ef0e 437 $ script/ view TT TT
3533daff 438 exists "/home/me/MyApp/script/../lib/MyApp/View"
439 exists "/home/me/MyApp/script/../t"
1390ef0e 440 created "/home/me/MyApp/script/../lib/MyApp/View/"
441 created "/home/me/MyApp/script/../t/view_TT.t"
3533daff 442
1390ef0e 443This simply creates a view called C<TT> (the second 'TT' argument) in
444a file called C<> (the first 'TT' argument). It is now up to you
445to decide how you want to structure your view layout. For the
446tutorial, we will start with a very simple TT template to initially
447demonstrate the concepts, but quickly migrate to a more typical
448"wrapper page" type of configuration (where the "wrapper" controls the
449overall "look and feel" of your site from a single file or set of
3533daff 451
1390ef0e 452Edit C<lib/MyApp/View/> and you should see that the default
453contents contains something similar to the following:
3533daff 454
1390ef0e 455 __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt');
3533daff 456
1390ef0e 457And update it to match:
459 __PACKAGE__->config(
460 # Change default TT extension
462 # Set the location for TT files
6abd3023 464 MyApp->path_to( 'root', 'src' ),
1390ef0e 465 ],
466 );
3533daff 467
1390ef0e 468B<NOTE:> Make sure to add a comma after '.tt2' outside the single
444d6b27 471This changes the default extension for Template Toolkit from '.tt' to
472'.tt2' and changes the base directory for your template files from
473C<root> to C<root/src>. Stick with these conventions for the
474tutorial, but feel free to use whatever options you desire in your
475applications (as with most things Perl, there's more than one way to
476do it...).
1390ef0e 477
acbd7bdd 478B<Note:> We will use C<root/src> as the base directory for our
444d6b27 479template files, with a full naming convention of
acbd7bdd 480C<root/src/_controller_name_/_action_name_.tt2>. Another popular option is to
481use C<root/> as the base (with a full filename pattern of
1390ef0e 484
485=head2 Create a TT Template Page
3533daff 486
487First create a directory for book-related TT templates:
1390ef0e 489 $ mkdir -p root/src/books
3533daff 490
491Then create C<root/src/books/list.tt2> in your editor and enter:
493 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
494 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
495 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
496 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
1390ef0e 498 [% # Provide a title -%]
3533daff 499 [% META title = 'Book List' -%]
501 <table>
502 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
503 [% # Display each book in a table row %]
504 [% FOREACH book IN books -%]
505 <tr>
506 <td>[% book.title %]</td>
507 <td>[% book.rating %]</td>
a46b474e 508 <td></td>
3533daff 509 </tr>
510 [% END -%]
511 </table>
513As indicated by the inline comments above, the C<META title> line uses
1390ef0e 514TT's META feature to provide a title to the "wrapper" that we will
515create later. Meanwhile, the C<FOREACH> loop iterates through each
516C<book> model object and prints the C<title> and C<rating> fields.
3533daff 517
4d63a0d5 518The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
519supports a wide variety of directives for "calling" other files,
520looping, conditional logic, etc. In general, TT simplifies the usual
444d6b27 521range of Perl operators down to the single dot (".") operator. This
4d63a0d5 522applies to operations as diverse as method calls, hash lookups, and list
523index values (see
524L<> for
444d6b27 525details and examples). In addition to the usual L<Template> module Pod
4d63a0d5 526documentation, you can access the TT manual at
55beb65d 527L<>.
3533daff 528
444d6b27 529B<TIP:> While you can build all sorts of complex logic into your TT
530templates, you should in general keep the "code" part of your
531templates as simple as possible. If you need more complex logic,
532create helper methods in your model that abstract out a set of code
533into a single call from your TT template. (Note that the same is true
534of your controller logic as well -- complex sections of code in your
535controllers should often be pulled out and placed into your model
536objects.) In Chapter 4 of the tutorial we will explore some extremely
537helpful and powerful features of L<DBIx::Class> that allow you to pull
538code out of your views and controllers and place it where it
539rightfully belongs in a model class.
1390ef0e 540
542=head2 Test Run The Application
544To test your work so far, first start the development server:
546 $ script/
548Then point your browser to L<http://localhost:3000> and you should
549still get the Catalyst welcome page. Next, change the URL in your
550browser to L<http://localhost:3000/books/list>. If you have
551everything working so far, you should see a web page that displays
552nothing other than our column headers for "Title", "Rating", and
553"Author(s)" -- we will not see any books until we get the database and
554model working below.
556If you run into problems getting your application to run correctly, it
557might be helpful to refer to some of the debugging techniques covered in
fce83e5f 558the L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> chapter of the
1390ef0e 559tutorial.
3533daff 560
564In this step, we make a text file with the required SQL commands to
429e7843 565create a database table and load some sample data. We will use
9887a877 566SQLite (L<>), a popular database that is
429e7843 567lightweight and easy to use. Be sure to get at least version 3. Open
1390ef0e 568C<myapp01.sql> in your editor and enter:
3533daff 569
570 --
571 -- Create a very simple database to hold book and author information
572 --
3b1fa91b 573 CREATE TABLE book (
3533daff 574 id INTEGER PRIMARY KEY,
575 title TEXT ,
576 rating INTEGER
577 );
3b1fa91b 578 -- 'book_author' is a many-to-many join table between books & authors
579 CREATE TABLE book_author (
3533daff 580 book_id INTEGER,
581 author_id INTEGER,
582 PRIMARY KEY (book_id, author_id)
583 );
3b1fa91b 584 CREATE TABLE author (
3533daff 585 id INTEGER PRIMARY KEY,
586 first_name TEXT,
587 last_name TEXT
588 );
589 ---
590 --- Load some sample data
591 ---
3b1fa91b 592 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
593 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
594 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
595 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
596 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
597 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
598 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
599 INSERT INTO author VALUES (3, 'Christian', 'Degu');
600 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
601 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
602 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
603 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
604 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
605 INSERT INTO book_author VALUES (1, 1);
606 INSERT INTO book_author VALUES (1, 2);
607 INSERT INTO book_author VALUES (1, 3);
608 INSERT INTO book_author VALUES (2, 4);
609 INSERT INTO book_author VALUES (3, 5);
610 INSERT INTO book_author VALUES (4, 6);
611 INSERT INTO book_author VALUES (4, 7);
612 INSERT INTO book_author VALUES (5, 8);
3533daff 613
3533daff 614Then use the following command to build a C<myapp.db> SQLite database:
616 $ sqlite3 myapp.db < myapp01.sql
618If you need to create the database more than once, you probably want to
619issue the C<rm myapp.db> command to delete the database before you use
1390ef0e 620the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
3533daff 621
622Once the C<myapp.db> database file has been created and initialized, you
623can use the SQLite command line environment to do a quick dump of the
624database contents:
626 $ sqlite3 myapp.db
acbd7bdd 627 SQLite version 3.5.9
3533daff 628 Enter ".help" for instructions
3b1fa91b 629 sqlite> select * from book;
3533daff 630 1|CCSP SNRS Exam Certification Guide|5
631 2|TCP/IP Illustrated, Volume 1|5
632 3|Internetworking with TCP/IP Vol.1|4
633 4|Perl Cookbook|5
634 5|Designing with Web Standards|5
635 sqlite> .q
636 $
3b1fa91b 640 $ sqlite3 myapp.db "select * from book"
3533daff 641 1|CCSP SNRS Exam Certification Guide|5
642 2|TCP/IP Illustrated, Volume 1|5
643 3|Internetworking with TCP/IP Vol.1|4
644 4|Perl Cookbook|5
645 5|Designing with Web Standards|5
647As with most other SQL tools, if you are using the full "interactive"
648environment you need to terminate your SQL commands with a ";" (it's not
649required if you do a single SQL statement on the command line). Use
650".q" to exit from SQLite from the SQLite interactive mode and return to
651your OS command prompt.
3b1fa91b 653Please note that here we have chosen to use 'singular' table names. This
6290bf87 654is because the default inflection code for L<DBIx::Class::Schema::Loader>
3b1fa91b 655does NOT handle plurals. There has been much philosophical discussion
656on whether table names should be plural or singular. There is no one
657correct answer, as long as one makes a choice and remains consistent
658with it. If you prefer plural table names (e.g. they are easier and
659more natural to read) then you will need to pass it an inflect_map
6290bf87 660option. See L<DBIx::Class::Schema::Loader> for more information.
3b1fa91b 661
a6d800ac 662For using other databases, such as PostgreSQL or MySQL, see
3ab6187c 663L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices>.
3533daff 664
acbd7bdd 665
8a472b34 666=head1 DATABASE ACCESS WITH DBIx::Class
3533daff 667
27909ed4 668Catalyst can be used with virtually any form of datastore available
669via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
444d6b27 670can be used to access databases through the traditional Perl L<DBI>
27909ed4 671interface or you can use a model to access files of any type on the
672filesystem. However, most Catalyst applications use some form of
673object-relational mapping (ORM) technology to create objects
674associated with tables in a relational database. Matt Trout's
675L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
676as the Perl-based ORM technology of choice. Most new Catalyst
a46b474e 677applications rely on DBIx::Class, as will this tutorial.
3533daff 678
a46b474e 679Although DBIx::Class has included support for a C<create=dynamic> mode
680to automatically read the database structure every time the
681application starts, it's use is no longer recommended. While it can
682make for "flashy" demos, the use of the C<create=static> mode we use
683below can be implemented just as quickly and provides many advantages
684(such as the ability to add your own methods to the overall DBIC
685framework, a technique that we see in Chapter 4).
3533daff 686
1390ef0e 687
a46b474e 688=head2 Make Sure You Have a Recent Version of the DBIx::Class Model
27909ed4 689
690First, let's be sure we have a recent version of the DBIC helper,
691L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, by
692running this command:
694 $ perl -MCatalyst::Model::DBIC::Schema -e \
695 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
a467a714 696 0.31
27909ed4 697
fce83e5f 698Please note the '\' above. Depending on your environment, you might
699be able to cut and paste the text as shown or need to remove the '\'
700character to that the command is all on a single line.
3b1fa91b 701
a467a714 702You should have version 0.31 or greater if you are following along
444d6b27 703with Debian 5. In other environments, you may need to run this
704command to install it directly from CPAN:
27909ed4 705
706 $ sudo cpan Catalyst::Model::DBIC::Schema
708And re-run the version print command to verify that you are now at
a467a714 7090.31 or higher.
27909ed4 710
a46b474e 712=head2 Create Static DBIx::Class Schema Files
27909ed4 713
98fd8420 714Before you continue, make sure your C<myapp.db> database file is in
715the application's topmost directory. Now use the model helper with
716the C<create=static> option to read the database with
27909ed4 717L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
718automatically build the required files for us:
3533daff 719
4ab6212d 720 $ script/ model DB DBIC::Schema MyApp::Schema \
fce83e5f 721 create=static dbi:SQLite:myapp.db
1390ef0e 722 exists "/home/me/MyApp/script/../lib/MyApp/Model"
723 exists "/home/me/MyApp/script/../t"
27909ed4 724 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
725 Schema dump completed.
1390ef0e 726 created "/home/me/MyApp/script/../lib/MyApp/Model/"
727 created "/home/me/MyApp/script/../t/model_DB.t"
3533daff 728
fce83e5f 729Please note the '\' above. Depending on your environment, you might
730be able to cut and paste the text as shown or need to remove the '\'
731character to that the command is all on a single line.
3b1fa91b 732
27909ed4 733The C<script/> command breaks down like this:
735=over 4
737=item *
739C<DB> is the name of the model class to be created by the helper in
742=item *
744C<DBIC::Schema> is the type of the model to create.
746=item *
748C<MyApp::Schema> is the name of the DBIC schema file written to
751=item *
753C<create=static> causes
754L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
755load the schema as it runs and then write that information out
756into files.
758=item *
27909ed4 760And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
761for use with SQLite.
765If you look in the C<lib/MyApp/> file, you will find that it
766only contains a call to the C<load_namespaces> method. You will also
767find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
768has a subdirectory called "Result". This "Result" subdirectory then
769has files named according to each of the tables in our simple database
3b1fa91b 770(C<>, C<>, and C<>). These three
a46b474e 771files are called "Result Classes" in DBIx::Class nomenclature. Although the
27909ed4 772Result Class files are named after tables in our database, the classes
773correspond to the I<row-level data> that is returned by DBIC (more on
774this later, especially in
3ab6187c 775L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
27909ed4 776
777The idea with the Result Source files created under
778C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
779edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
780warning. If you place all of your changes below that point in the
781file, you can regenerate the automatically created information at the
782top of each file should your database structure get updated.
784Also note the "flow" of the model information across the various files
785and directories. Catalyst will initially load the model from
786C<lib/MyApp/Model/>. This file contains a reference to
787C<lib/MyApp/>, so that file is loaded next. Finally, the
788call to C<load_namespaces> in C<> will load each of the
789"Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
790The final outcome is that Catalyst will dynamically create three
791table-specific Catalyst models every time the application starts (you
792can see these three model files listed in the debug output generated
793when you launch the application).
795B<NOTE:> Older versions of
796L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
a46b474e 797deprecated DBIx::Class C<load_classes> technique instead of the newer
27909ed4 798C<load_namspaces>. For new applications, please try to use
799C<load_namespaces> since it more easily supports a very useful DBIC
800technique called "ResultSet Classes." If you need to convert an
801existing application from "load_classes" to "load_namespaces," you can
802use this process to automate the migration (but first make sure you
803have v0.23 C<Catalyst::Model::DBIC::Schema> as discussed above):
805 $ # First delete the existing schema file to disable "compatibility" mode
806 $ rm lib/MyApp/
807 $
808 $ # Then re-run the helper to build the files for "load_namespaces"
809 $ script/ model DB DBIC::Schema MyApp::Schema \
fce83e5f 810 create=static dbi:SQLite:myapp.db
3b1fa91b 811 $
27909ed4 812 $ # Now convert the existing files over
813 $ cd lib/MyApp/Schema
814 $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s;
815 $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_");
816 $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
817 $ cd ../../..
818 $
819 $ # And finally delete the old files
820 $ rm lib/MyApp/Schema/*.pm
822The "C<perl -MIO::ALL ...>" script will copy all the customized
823relationship (and other) information below "C<# DO NOT MODIFY>" line
824from the old files in C<lib/MyApp/Schema> to the new files in
825C<lib/MyApp/Schema/Result> (we will be starting to add some
826"customized relationship information in the section below).
3533daff 827
dc9a0503 828
acbd7bdd 831Open C<lib/MyApp/Controller/> and un-comment the model code we
832left disabled earlier so that your version matches the following (un-
3b1fa91b 833comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
acbd7bdd 834and delete the next 2 lines):
1390ef0e 835
836 =head2 list
838 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
840 =cut
842 sub list : Local {
843 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
844 # 'Context' that's used to 'glue together' the various components
845 # that make up the application
846 my ($self, $c) = @_;
848 # Retrieve all of the book records as book model objects and store in the
849 # stash where they can be accessed by the TT template
3b1fa91b 850 $c->stash->{books} = [$c->model('DB::Book')->all];
1390ef0e 851
852 # Set the TT template to use. You will almost always want to do this
853 # in your action methods (action methods respond to user input in
854 # your controllers).
855 $c->stash->{template} = 'books/list.tt2';
856 }
3b1fa91b 858B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
859above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
c93b5eaa 860two are equivalent. Either way, C<$c-E<gt>model> returns a
861L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
4d63a0d5 862against the database and iterating over the set of results that is
c93b5eaa 863returned.
865We are using the C<-E<gt>all> to fetch all of the books. DBIC
866supports a wide variety of more advanced operations to easily do
867things like filtering and sorting the results. For example, the
518f3851 868following could be used to sort the results by descending title:
c93b5eaa 869
3b1fa91b 870 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
c93b5eaa 871
872Some other examples are provided in
873L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
874additional information found at L<DBIx::Class::ResultSet/search>,
877and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
1390ef0e 878
880=head2 Test Run The Application
3533daff 881
1435672d 882First, let's enable an environment variable that causes DBIx::Class to
acbd7bdd 883dump the SQL statements used to access the database. This is a
1435672d 884helpful trick when you are trying to debug your database-oriented
3533daff 886
887 $ export DBIC_TRACE=1
4d63a0d5 889This assumes you are using bash as your shell -- adjust accordingly if
3533daff 890you are using a different shell (for example, under tcsh, use
891C<setenv DBIC_TRACE 1>).
d0496197 893B<NOTE:> You can also set this in your code using
3533daff 894C<$class-E<gt>storage-E<gt>debug(1);>. See
895L<DBIx::Class::Manual::Troubleshooting> for details (including options
4d63a0d5 896to log to a file instead of displaying to the Catalyst development server
3533daff 897log).
1390ef0e 899Then launch the Catalyst development server. The log output should
900display something like:
3533daff 901
acbd7bdd 902 $ script/
3533daff 903 [debug] Debug messages enabled
1390ef0e 904 [debug] Statistics enabled
3533daff 905 [debug] Loaded plugins:
906 .----------------------------------------------------------------------------.
a467a714 907 | Catalyst::Plugin::ConfigLoader 0.27 |
908 | Catalyst::Plugin::StackTrace 0.11 |
909 | Catalyst::Plugin::Static::Simple 0.25 |
3533daff 910 '----------------------------------------------------------------------------'
912 [debug] Loaded dispatcher "Catalyst::Dispatcher"
913 [debug] Loaded engine "Catalyst::Engine::HTTP"
914 [debug] Found home "/home/me/MyApp"
45d511e0 915 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
3533daff 916 [debug] Loaded components:
917 .-----------------------------------------------------------------+----------.
918 | Class | Type |
919 +-----------------------------------------------------------------+----------+
920 | MyApp::Controller::Books | instance |
921 | MyApp::Controller::Root | instance |
d0496197 922 | MyApp::Model::DB | instance |
3b1fa91b 923 | MyApp::Model::DB::Author | class |
924 | MyApp::Model::DB::Book | class |
925 | MyApp::Model::DB::BookAuthor | class |
3533daff 926 | MyApp::View::TT | instance |
927 '-----------------------------------------------------------------+----------'
929 [debug] Loaded Private actions:
930 .----------------------+--------------------------------------+--------------.
931 | Private | Class | Method |
932 +----------------------+--------------------------------------+--------------+
933 | /default | MyApp::Controller::Root | default |
934 | /end | MyApp::Controller::Root | end |
1390ef0e 935 | /index | MyApp::Controller::Root | index |
3533daff 936 | /books/index | MyApp::Controller::Books | index |
937 | /books/list | MyApp::Controller::Books | list |
938 '----------------------+--------------------------------------+--------------'
940 [debug] Loaded Path actions:
941 .-------------------------------------+--------------------------------------.
942 | Path | Private |
943 +-------------------------------------+--------------------------------------+
1390ef0e 944 | / | /default |
945 | / | /index |
946 | /books | /books/index |
3533daff 947 | /books/list | /books/list |
948 '-------------------------------------+--------------------------------------'
a467a714 950 [info] MyApp powered by Catalyst 5.80013
acbd7bdd 951 You can connect to your server at http://debian:3000
3533daff 952
1390ef0e 953B<NOTE:> Be sure you run the C<script/> command from
954the 'base' directory of your application, not inside the C<script>
955directory itself or it will not be able to locate the C<myapp.db>
956database file. You can use a fully qualified or a relative path to
957locate the database file, but we did not specify that when we ran the
3533daff 958model helper earlier.
960Some things you should note in the output above:
962=over 4
1390ef0e 964=item *
3533daff 965
1390ef0e 966Catalyst::Model::DBIC::Schema dynamically created three model classes,
967one to represent each of the three tables in our database
3b1fa91b 968(C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
969and C<MyApp::Model::DB::Book>).
3533daff 970
1390ef0e 971=item *
3533daff 972
973The "list" action in our Books controller showed up with a path of
978Point your browser to L<http://localhost:3000> and you should still get
979the Catalyst welcome page.
981Next, to view the book list, change the URL in your browser to
982L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 983books loaded by the C<myapp01.sql> script above without any formatting.
984The rating for each book should appear on each row, but the "Author(s)"
191dee29 985column will still be blank (we will fill that in later).
3533daff 986
a46b474e 987Also notice in the output of the C<script/> that
988DBIx::Class used the following SQL to retrieve the data:
3533daff 989
fce83e5f 990 SELECT, me.title, me.rating FROM book me
3533daff 991
992because we enabled DBIC_TRACE.
0c51850e 994You now have the beginnings of a simple but workable web application.
3533daff 995Continue on to future sections and we will develop the application
996more fully.
1390ef0e 999=head1 CREATE A WRAPPER FOR THE VIEW
acbd7bdd 1001When using TT, you can (and should) create a wrapper that will
1390ef0e 1002literally wrap content around each of your templates. This is
1003certainly useful as you have one main source for changing things that
1004will appear across your entire site/application instead of having to
1005edit many individual files.
1008=head2 Configure For The Wrapper
1010In order to create a wrapper, you must first edit your TT view and
444d6b27 1011tell it where to find your wrapper file.
1390ef0e 1012
444d6b27 1013Edit you TT view in C<lib/MyApp/View/> and change it to match the
1390ef0e 1015
1016 __PACKAGE__->config(
1017 # Change default TT extension
1018 TEMPLATE_EXTENSION => '.tt2',
1019 # Set the location for TT files
1020 INCLUDE_PATH => [
c2dfb562 1021 MyApp->path_to( 'root', 'src' ),
1390ef0e 1022 ],
1023 # Set to 1 for detailed timer stats in your HTML as comments
1024 TIMER => 0,
1025 # This is your wrapper template located in the 'root/src'
1026 WRAPPER => 'wrapper.tt2',
1027 );
1030=head2 Create the Wrapper Template File and Stylesheet
1032Next you need to set up your wrapper template. Basically, you'll want
1033to take the overall layout of your site and put it into this file.
1034For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1036 <?xml version="1.0" encoding="UTF-8"?>
1037 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "">
1038 <html xmlns="" xml:lang="en" lang="en">
1039 <head>
1040 <title>[% template.title or "My Catalyst App!" %]</title>
1041 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1042 </head>
1044 <body>
1045 <div id="outer">
1046 <div id="header">
1047 [%# Your logo could go here -%]
1048 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1049 [%# Insert the page title -%]
1050 <h1>[% template.title or site.title %]</h1>
1051 </div>
1053 <div id="bodyblock">
1054 <div id="menu">
1055 Navigation:
1056 <ul>
1057 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1058 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1390ef0e 1059 </ul>
1060 </div><!-- end menu -->
1062 <div id="content">
1063 [%# Status and error messages %]
1064 <span class="message">[% status_msg %]</span>
1065 <span class="error">[% error_msg %]</span>
1066 [%# This is where TT will stick all of your template's contents. -%]
1067 [% content %]
1068 </div><!-- end content -->
1069 </div><!-- end bodyblock -->
1071 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 1072 </div><!-- end outer -->
1390ef0e 1073
1074 </body>
1075 </html>
1077Notice the status and error message sections in the code above:
1079 <span class="status">[% status_msg %]</span>
1080 <span class="error">[% error_msg %]</span>
1082If we set either message in the Catalyst stash (e.g.,
1083C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1084will be displayed whenever any view used by that request is rendered.
1085The C<message> and C<error> CSS styles can be customized to suit your
1086needs in the C<root/static/css/main.css> file we create below.
1090=over 4
1092=item *
1094The Catalyst stash only lasts for a single HTTP request. If
1095you need to retain information across requests you can use
1096L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
4b4d3884 1097Catalyst sessions in the Authentication chapter of the tutorial).
1390ef0e 1098
1099=item *
1101Although it is beyond the scope of this tutorial, you may wish to use
1102a JavaScript or AJAX tool such as jQuery (L<>) or
1103Dojo (L<>).
1108=head3 Create A Basic Stylesheet
1110First create a central location for stylesheets under the static
1113 $ mkdir root/static/css
1115Then open the file C<root/static/css/main.css> (the file referenced in
1116the stylesheet href link of our wrapper above) and add the following
1119 #header {
1120 text-align: center;
1121 }
1122 #header h1 {
1123 margin: 0;
1124 }
1125 #header img {
1126 float: right;
1127 }
1128 #footer {
1129 text-align: center;
1130 font-style: italic;
1131 padding-top: 20px;
1132 }
1133 #menu {
1134 font-weight: bold;
1135 background-color: #ddd;
1136 }
1137 #menu ul {
1138 list-style: none;
1139 float: left;
1140 margin: 0;
1141 padding: 0 0 50% 5px;
1142 font-weight: normal;
1143 background-color: #ddd;
1144 width: 100px;
1145 }
1146 #content {
1147 margin-left: 120px;
1148 }
1149 .message {
1150 color: #390;
1151 }
1152 .error {
1153 color: #f00;
1154 }
1156You may wish to check out a "CSS Framework" like Emastic
1157(L<>) as a way to quickly
1158provide lots of high-quality CSS functionality.
1161=head2 Test Run The Application
1163Restart the development server and hit "Reload" in your web browser
1164and you should now see a formatted version of our basic book list.
1165Although our wrapper and stylesheet are obviously very simple, you
1166should see how it allows us to control the overall look of an entire
1167website from two central files. To add new pages to the site, just
1168provide a template that fills in the C<content> section of our wrapper
1169template -- the wrapper will provide the overall feel of the page.
a46b474e 1172=head2 Updating the Generated DBIx::Class Result Class Files
3533daff 1173
acbd7bdd 1174Let's manually add some relationship information to the auto-generated
1175Result Class files. (Note: if you are using a database other than
1176SQLite, such as PostgreSQL, then the relationship could have been
1177automatically placed in the Result Class files. If so, you can skip
3b1fa91b 1178this step.) First edit C<lib/MyApp/Schema/Result/> and add the
acbd7bdd 1179following text below the C<# You can replace this text...> comment:
3533daff 1180
1181 #
1182 # Set relationships:
1390ef0e 1183 #
3533daff 1184
1185 # has_many():
1186 # args:
1187 # 1) Name of relationship, DBIC will create accessor with this name
1188 # 2) Name of the model class referenced by this relationship
1435672d 1189 # 3) Column name in *foreign* table (aka, foreign key in peer table)
fce83e5f 1190 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthor', 'book_id');
3533daff 1191
1192 # many_to_many():
1193 # args:
1194 # 1) Name of relationship, DBIC will create accessor with this name
1390ef0e 1195 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1196 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1197 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1198 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
3533daff 1199
1201B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1202file. As with any Perl package, we need to end the last line with
1203a statement that evaluates to C<true>. This is customarily done with
1204C<1;> on a line by itself.
a46b474e 1206This code defines both a C<has_many> and a C<many_to_many>
1207relationship. The C<many_to_many> relationship is optional, but it
1208makes it easier to map a book to its collection of authors. Without
3b1fa91b 1209it, we would have to "walk" though the C<book_author> table as in
1210C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
a46b474e 1211will see examples on how to use DBIx::Class objects in your code soon,
3b1fa91b 1212but note that because C<$book-E<gt>book_author> can return multiple
1390ef0e 1213authors, we have to use C<first> to display a single author).
5a82cb36 1214C<many_to_many> allows us to use the shorter
1215C<$book-E<gt>author-E<gt>first-E<gt>last_name>. Note that you cannot
1216define a C<many_to_many> relationship without also having the
1217C<has_many> relationship in place.
3533daff 1218
3b1fa91b 1219Then edit C<lib/MyApp/Schema/Result/> and add relationship
3533daff 1220information as follows (again, be careful to put in above the C<1;> but
1221below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
1223 #
1224 # Set relationships:
1225 #
1227 # has_many():
1228 # args:
4d63a0d5 1229 # 1) Name of relationship, DBIC will create an accessor with this name
3533daff 1230 # 2) Name of the model class referenced by this relationship
1435672d 1231 # 3) Column name in *foreign* table (aka, foreign key in peer table)
fce83e5f 1232 __PACKAGE__->has_many(book_authors => 'MyApp::Schema::Result::BookAuthor', 'author_id');
3533daff 1233
1234 # many_to_many():
1235 # args:
1236 # 1) Name of relationship, DBIC will create accessor with this name
1237 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1238 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1239 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1240 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
3533daff 1241
1390ef0e 1242Finally, do the same for the "join table,"
3b1fa91b 1243C<lib/MyApp/Schema/Result/>:
3533daff 1244
1245 #
1246 # Set relationships:
1247 #
1249 # belongs_to():
1250 # args:
1251 # 1) Name of relationship, DBIC will create accessor with this name
1252 # 2) Name of the model class referenced by this relationship
1253 # 3) Column name in *this* table
3b1fa91b 1254 __PACKAGE__->belongs_to(book => 'MyApp::Schema::Result::Book', 'book_id');
3533daff 1255
1256 # belongs_to():
1257 # args:
1258 # 1) Name of relationship, DBIC will create accessor with this name
1259 # 2) Name of the model class referenced by this relationship
1260 # 3) Column name in *this* table
3b1fa91b 1261 __PACKAGE__->belongs_to(author => 'MyApp::Schema::Result::Author', 'author_id');
3533daff 1262
1390ef0e 1264=head2 Run The Application
3533daff 1265
4d63a0d5 1266Run the Catalyst development server script with the C<DBIC_TRACE> option
1267(it might still be enabled from earlier in the tutorial, but here is an
1268alternate way to specify the option just in case):
3533daff 1269
1270 $ DBIC_TRACE=1 script/
1390ef0e 1272Make sure that the application loads correctly and that you see the
1273three dynamically created model class (one for each of the
4ab6212d 1274Result Classes we created).
3533daff 1275
acbd7bdd 1276Then hit the URL L<http://localhost:3000/books/list> with your browser
444d6b27 1277and be sure that the book list still displays correctly. You can leave
1278the development server running for the next step if you wish.
3533daff 1279
c2dfb562 1280B<Note:> You will not see the authors yet because the view does not yet
1281use the new relations. Read on to the next section where we update the
1282template to do that.
3533daff 1283
acbd7bdd 1287Let's add a new column to our book list page that takes advantage of
1288the relationship information we manually added to our schema files in
a46b474e 1289the previous section. Edit C<root/src/books/list.tt2> and replace
3b1fa91b 1290the "empty" table cell "<td></td>" with the following:
3533daff 1291
acbd7bdd 1292 ...
3533daff 1293 <td>
fce83e5f 1294 [% # NOTE: See Chapter 4 for a better way to do this! -%]
3533daff 1295 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1296 [% # loop in 'side effect notation' to load just the last names of the -%]
6d97b973 1297 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
3533daff 1298 [% # a value, so nothing will be printed here. But, if you have something -%]
6d97b973 1299 [% # in TT that does return a value and you don't want it printed, you -%]
1300 [% # 1) assign it to a bogus value, or -%]
1301 [% # 2) use the CALL keyword to call it and discard the return value. -%]
3533daff 1302 [% tt_authors = [ ];
1303 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1304 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1305 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1306 ([% tt_authors.size | html %])
1307 [% # Use another TT vmethod to join & print the names & comma separators -%]
1308 [% tt_authors.join(', ') | html %]
1309 </td>
acbd7bdd 1310 ...
3533daff 1311
444d6b27 1312B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1313possible out of your views. This kind of logic belongs in your model
fce83e5f 1314(the same goes for controllers -- keep them as "thin" as possible and
1315push all of the "complicated code" out to your model objects). Avoid
1316code like you see in the previous example -- we are only using it here
1317to show some extra features in TT until we get to the more advanced
444d6b27 1318model features we will see in Chapter 4 (see
fce83e5f 1319L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1390ef0e 1321Then hit "Reload" in your browser (note that you don't need to reload
3533daff 1322the development server or use the C<-r> option when updating TT
1390ef0e 1323templates) and you should now see the number of authors each book has
1324along with a comma-separated list of the authors' last names. (If you
1325didn't leave the development server running from the previous step,
1326you will obviously need to start it before you can refresh your
1327browser window.)
1329If you are still running the development server with C<DBIC_TRACE>
1330enabled, you should also now see five more C<SELECT> statements in the
1331debug output (one for each book as the authors are being retrieved by
a46b474e 1332DBIx::Class):
3533daff 1333
fce83e5f 1334 SELECT, me.title, me.rating FROM book me:
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 = ? ): '1'
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 = ? ): '2'
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 = ? ): '3'
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 = ? ): '4'
3b1fa91b 1343 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1344 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '5'
c2dfb562 1345
1346Also note in C<root/src/books/list.tt2> that we are using "| html", a
1347type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1348and &gt; and avoid various types of dangerous hacks against your
1349application. In a real application, you would probably want to put
1350"| html" at the end of every field where a user has control over the
1351information that can appear in that field (and can therefore inject
1352markup or code if you don't "neutralize" those fields). In addition to
1353"| html", Template Toolkit has a variety of other useful filters that
1354can found in the documentation for
3533daff 1356
1360In some situations, it can be useful to run your application and
1361display a page without using a browser. Catalyst lets you do this
1362using the C<scripts/> script. Just supply the URL you
1363wish to display and it will run that request through the normal
1364controller dispatch logic and use the appropriate view to render the
1365output (obviously, complex pages may dump a lot of text to your
1366terminal window). For example, if you type:
1368 $ script/ "/books/list"
1370You should get the same text as if you visited
1371L<http://localhost:3000/books/list> with the normal development server
1372and asked your browser to view the page source.
3533daff 1373
1390ef0e 1374
4b4d3884 1377B<NOTE: The rest of this chapter of the tutorial is optional. You can
3ab6187c 1378skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
3533daff 1379if you wish.>
acbd7bdd 1381
8a472b34 1382=head2 Using 'RenderView' for the Default View
1390ef0e 1383
1384Once your controller logic has processed the request from a user, it
1385forwards processing to your view in order to generate the appropriate
3533daff 1386response output. Catalyst uses
1390ef0e 1387L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
4d63a0d5 1388default to automatically perform this operation. If you look in
1390ef0e 1389C<lib/MyApp/Controller/>, you should see the empty
3533daff 1390definition for the C<sub end> method:
1392 sub end : ActionClass('RenderView') {}
1390ef0e 1394The following bullet points provide a quick overview of the
3533daff 1395C<RenderView> process:
1397=over 4
1399=item *
1401C<> is designed to hold application-wide logic.
1403=item *
1390ef0e 1405At the end of a given user request, Catalyst will call the most specific
1406C<end> method that's appropriate. For example, if the controller for a
1407request has an C<end> method defined, it will be called. However, if
1408the controller does not define a controller-specific C<end> method, the
3533daff 1409"global" C<end> method in C<> will be called.
1411=item *
1413Because the definition includes an C<ActionClass> attribute, the
1414L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1415will be executed B<after> any code inside the definition of C<sub end>
1416is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1417for more information on C<ActionClass>.
1419=item *
1390ef0e 1421Because C<sub end> is empty, this effectively just runs the default
1422logic in C<RenderView>. However, you can easily extend the
1423C<RenderView> logic by adding your own code inside the empty method body
1424(C<{}>) created by the Catalyst Helpers when we first ran the
1425C<> to initialize our application. See
1426L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
4d63a0d5 1427detailed information on how to extend C<RenderView> in C<sub end>.
3533daff 1428
fce83e5f 1432=head2 RenderView's "dump_info" Feature
1434One of the nice features of C<RenderView> is that it automatically
1435allows you to add C<dump_info=1> to the end of any URL for your
1436application and it will force the display of the "exception dump"
1437screen to the client browser. You can try this out by starting the
1438development server as before and then point your browser to this URL:
1440 http://localhost:3000/books/list?dump_info=1
1442You should get a page with the following message at the top:
1444 Caught exception in MyApp::Controller::Root->end "Forced debug -
1445 Scrubbed output at /usr/share/perl5/Catalyst/Action/ line 46."
1447Along with a summary of your application's state at the end of the
1448processing for that request. The "Stash" section should show a
1449summarized version of the DBIC book model objects. If desired, you
1450can adjust the summarization logic (called "scrubbing" logic) -- see
1451L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for
1454Note that you shouldn't need to worry about "normal clients" using
1455this technique to "reverse engineer" your application -- C<RenderView>
1456only supports the C<dump_info=1> feature when your application is
1457running in C<-Debug> mode (something you won't do once you have your
1458application deployed in production).
3533daff 1461=head2 Using The Default Template Name
1390ef0e 1463By default, C<Catalyst::View::TT> will look for a template that uses the
1464same name as your controller action, allowing you to save the step of
1465manually specifying the template name in each action. For example, this
1466would allow us to remove the
1467C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1468C<list> action in the Books controller. Open
3533daff 1469C<lib/MyApp/Controller/> in your editor and comment out this line
1470to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1471has changed):
1473 =head2 list
1475 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1477 =cut
1479 sub list : Local {
1480 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1481 # 'Context' that's used to 'glue together' the various components
1482 # that make up the application
1483 my ($self, $c) = @_;
1485 # Retrieve all of the book records as book model objects and store in the
1486 # stash where they can be accessed by the TT template
3b1fa91b 1487 $c->stash->{books} = [$c->model('DB::Book')->all];
3533daff 1488
1489 # Set the TT template to use. You will almost always want to do this
1490 # in your action methods (actions methods respond to user input in
1491 # your controllers).
1492 #$c->stash->{template} = 'books/list.tt2';
1493 }
3533daff 1495
1390ef0e 1496You should now be able to restart the development server as per the
3533daff 1497previous section and access the L<http://localhost:3000/books/list>
1498as before.
1500B<NOTE:> Please note that if you use the default template technique,
1501you will B<not> be able to use either the C<$c-E<gt>forward> or
4b4d3884 1502the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1503Chapter 9 of the Tutorial).
3533daff 1504
3b1fa91b 1505B<IMPORTANT:> Make sure that you do NOT skip the following section
1506before continuing to the next chapter 4 Basic CRUD.
3533daff 1507
fce83e5f 1508
4d63a0d5 1509=head2 Return To A Manually Specified Template
3533daff 1510
1511In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1512later in the tutorial, you should remove the comment from the
1513statement in C<sub list> in C<lib/MyApp/Controller/>:
1515 $c->stash->{template} = 'books/list.tt2';
1390ef0e 1517Then delete the C<TEMPLATE_EXTENSION> line in
3533daff 1518C<lib/MyApp/View/>.
1390ef0e 1520You should then be able to restart the development server and
3533daff 1521access L<http://localhost:3000/books/list> in the same manner as
1522with earlier sections.
1525=head1 AUTHOR
1527Kennedy Clark, C<>
1529Please report any errors, issues or suggestions to the author. The
1530most recent version of the Catalyst Tutorial can be found at
59884771 1531L<>.
3533daff 1532
45c7830f 1533Copyright 2006-2008, Kennedy Clark, under Creative Commons License
8482d557 1534(L<>).