rename View::TT to View::HTML
[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
f058768a 105One of the greatest benefits of Catalyst is that it has such a large
106library of bases classes and plugins available that you can use easily
107add functionality to your application. Plugins are used to seamlessly
108integrate existing Perl modules into the overall Catalyst framework. In
109general, they do this by adding additional methods to the C<context>
110object (generally written as C<$c>) that Catalyst passes to every
111component throughout the framework.
3533daff 113
114By default, Catalyst enables three plugins/flags:
116=over 4
1390ef0e 118=item *
3533daff 119
120C<-Debug> Flag
122Enables the Catalyst debug output you saw when we started the
123C<script/> development server earlier. You can remove
79a529cc 124this item when you place your application into production.
3533daff 125
444d6b27 126To be technically correct, it turns out that C<-Debug> is not a plugin, but a I<flag>.
1390ef0e 127Although most of the items specified on the C<__PACKAGE__-E<gt>setup>
128line of your application class will be plugins, Catalyst supports a
129limited number of flag options (of these, C<-Debug> is the most
130common). See the documentation for C<> to get details on
131other flags (currently C<-Engine>, C<-Home>, and C<-Log>).
3533daff 132
444d6b27 133If you prefer, there are several other ways to enable debug output:
135=over 4
137=item *
139Use the C<$c-E<gt>debug> method
141=item *
143The C<-d> option to C<script/>
145=item *
147The C<CATALYST_DEBUG=1> environment variable (or set it to
148zero to templorarily disable debug output).
3533daff 151
152B<TIP>: Depending on your needs, it can be helpful to permanently
153remove C<-Debug> from C<lib/> and then use the C<-d> option
154to C<script/> to re-enable it just for the development
1390ef0e 155server. We will not be using that approach in the tutorial, but feel
3533daff 156free to make use of it in your own projects.
158=item *
162C<ConfigLoader> provides an automatic way to load configurable
c010ae0d 163parameters for your application from a central
164L<Config::General|Config::General> file (versus having the values
165hard-coded inside your Perl modules). Config::General uses syntax
166very similar to Apache configuration files. We will see how to use
167this feature of Catalyst during the authentication and authorization
4b4d3884 168sections (Chapter 5 and Chapter 6).
3533daff 169
1435672d 170B<IMPORTANT NOTE:> If you are using a version of
171L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, be aware
172that Catalyst changed the default format from YAML to the more
173straightforward C<Config::General> style. This tutorial uses the
174newer C<myapp.conf> file for C<Config::General>. However, Catalyst
175supports both formats and will automatically use either C<myapp.conf>
176or C<myapp.yml> (or any other format supported by
177L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and
178L<Config::Any|Config::Any>). If you are using a version of
179Catalyst::Devel prior to 1.06, you can convert to the newer format by
180simply creating the C<myapp.conf> file manually and deleting
181C<myapp.yml>. The default contents of the C<myapp.conf> you create
182should only consist of one line:
184 name MyApp
15e1d0b2 185
1390ef0e 186B<TIP>: This script can be useful for converting between configuration
15e1d0b2 187formats:
1390ef0e 189 perl -Ilib -e 'use MyApp; use Config::General;
15e1d0b2 190 Config::General->new->save_file("myapp.conf", MyApp->config);'
3533daff 192=item *
4d63a0d5 196C<Static::Simple> provides an easy way to serve static content, such
197as images and CSS files, from the development server.
3533daff 198
94d8da41 201For our application, we want to add one new plugin into the mix. To
1390ef0e 202do this, edit C<lib/> (this file is generally referred to as
acbd7bdd 203your I<application class>) and delete the lines with:
3533daff 204
1dc333c7 205 use Catalyst qw/
206 -Debug
207 ConfigLoader
208 Static::Simple
209 /;
3533daff 210
1390ef0e 211Then replace it with:
b411df01 212
acbd7bdd 213 # Load plugins
fce83e5f 214 use Catalyst qw/
1dc333c7 215 -Debug
216 ConfigLoader
217 Static::Simple
219 StackTrace
220 /;
1390ef0e 221
94d8da41 222B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
acbd7bdd 223techniques to load these plugins/flags. For example, you might see
224the following:
94d8da41 225
acbd7bdd 226 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
94d8da41 227
228Don't let these variations confuse you -- they all accomplish the same
f058768a 231This tells Catalyst to start using one additional plugin,
1390ef0e 232L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a
233stack trace to the standard Catalyst "debug screen" (the screen
234Catalyst sends to your browser when an error occurs). Be aware that
235L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
236browser, not in the console window from which you're running your
237application, which is where logging output usually goes.
3533daff 238
444d6b27 239Make sure when adding new plugins you also include them as a new
c12b0d35 240dependency within the Makefile.PL file. For example, after adding
3b1fa91b 241the StackTrace plugin the Makefile.PL should include the following
244 requires 'Catalyst::Plugin::StackTrace';
1390ef0e 247B<Notes:>
3533daff 248
249=over 4
1390ef0e 251=item *
253C<__PACKAGE__> is just a shorthand way of referencing the name of the
254package where it is used. Therefore, in C<>, C<__PACKAGE__>
255is equivalent to C<MyApp>.
3533daff 256
1390ef0e 257=item *
3533daff 258
1390ef0e 259You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
260before you put your application into production, but it can be helpful
261during development.
3533daff 262
1390ef0e 263=item *
3533daff 264
444d6b27 265When specifying plugins, you can omit C<Catalyst::Plugin::> from the
266name. Additionally, you can spread the plugin names across multiple
267lines as shown here or place them all on one line.
cca5cd98 268
3533daff 269=back
3533daff 271
1390ef0e 274As discussed earlier, controllers are where you write methods that
275interact with user input. Typically, controller methods respond to
4d63a0d5 276C<GET> and C<POST> requests from the user's web browser.
3533daff 277
278Use the Catalyst C<create> script to add a controller for book-related
281 $ script/ controller Books
282 exists "/home/me/MyApp/script/../lib/MyApp/Controller"
283 exists "/home/me/MyApp/script/../t"
284 created "/home/me/MyApp/script/../lib/MyApp/Controller/"
285 created "/home/me/MyApp/script/../t/controller_Books.t"
4b4d3884 287Then edit C<lib/MyApp/Controller/> (as discussed in Chapter 2 of
1390ef0e 288the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
289each of the three parts of MVC: C<Model>, C<View>, and C<Controller>)
290and add the following method to the controller:
3533daff 291
292 =head2 list
294 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
296 =cut
1390ef0e 297
f058768a 298 sub list :Local {
3533daff 299 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
300 # 'Context' that's used to 'glue together' the various components
301 # that make up the application
302 my ($self, $c) = @_;
304 # Retrieve all of the book records as book model objects and store in the
305 # stash where they can be accessed by the TT template
0ed3df53 306 # $c->stash(books => [$c->model('DB::Book')->all]);
1390ef0e 307 # But, for now, use this code until we create the model later
0ed3df53 308 $c->stash(books => '');
1390ef0e 309
3533daff 310 # Set the TT template to use. You will almost always want to do this
311 # in your action methods (action methods respond to user input in
312 # your controllers).
61cb69fd 313 $c->stash(template => 'books/list.tt2');
3533daff 314 }
1390ef0e 316B<TIP>: See Appendix 1 for tips on removing the leading spaces when
317cutting and pasting example code from POD-based documents.
3533daff 318
1390ef0e 319Programmers experienced with object-oriented Perl should recognize
320C<$self> as a reference to the object where this method was called.
321On the other hand, C<$c> will be new to many Perl programmers who have
322not used Catalyst before (it's sometimes written as C<$context>). The
323Context object is automatically passed to all Catalyst components. It
324is used to pass information between components and provide access to
325Catalyst and plugin functionality.
3533daff 326
245b41d1 327Catalyst actions are regular Perl methods, but they make use of
f058768a 328attributes (the "C<:Local>" next to the "C<sub list>" in the code
0416017e 329above) to provide additional information to the Catalyst dispatcher
330logic (note that the space between the colon and the attribute name is
4d63a0d5 331optional; you will see attributes written both ways). Most Catalyst
245b41d1 332Controllers use one of five action types:
0416017e 333
334=over 4
336=item *
245b41d1 338B<:Private> -- Use C<:Private> for methods that you want to make into
444d6b27 339an action, but you do not want Catalyst to directly expose the method
245b41d1 340to your users. Catalyst will not map C<:Private> methods to a URI.
341Use them for various sorts of "special" methods (the C<begin>,
342C<auto>, etc. discussed below) or for methods you want to be able to
343C<forward> or C<detach> to. (If the method is a plain old "helper
344method" that you don't want to be an action at all, then just define
345the method without any attribute -- you can call it in your code, but
346the Catalyst dispatcher will ignore it.)
0416017e 347
245b41d1 348There are five types of "special" build-in C<:Private> actions:
349C<begin>, C<end>, C<default>, C<index>, and C<auto>.
0416017e 350
26c9cad5 351=over 4
0416017e 353=item *
355With C<begin>, C<end>, C<default>, C<index> private actions, only the
356most specific action of each type will be called. For example, if you
357define a C<begin> action in your controller it will I<override> a
358C<begin> action in your application/root controller -- I<only> the
359action in your controller will be called.
361=item *
363Unlike the other actions where only a single method is called for each
364request, I<every> auto action along the chain of namespaces will be
365called. Each C<auto> action will be called I<from the application/root
366controller down through the most specific class>.
370=item *
245b41d1 372B<:Path> -- C<:Path> actions let you map a method to an explicit URI
373path. For example, "C<:Path('list')>" in
0416017e 374C<lib/MyApp/Controller/> would match on the URL
444d6b27 375C<http://localhost:3000/books/list>, but "C<:Path('/list')>" would
376match on C<http://localhost:3000/list> (because of the leading slash).
377You can use C<:Args()> to specify how many arguments an action should
378accept. See L<Catalyst::Manual::Intro/Action_types> for more
379information and examples.
0416017e 380
381=item *
245b41d1 383B<:Local> -- C<:Local> is merely a shorthand for
384"C<:Path('_name_of_method_')>". For example, these are equivalent:
385"C<sub create_book :Local {...}>" and
386"C<sub create_book :Path('create_book') {...}>".
388=item *
390B<:Global> -- C<:Global> is merely a shorthand for
391"C<:Path('/_name_of_method_')>". For example, these are equivalent:
392"C<sub create_book :Global {...}>" and
393"C<sub create_book :Path('/create_book') {...}>".
395=item *
397B<:Chained> -- Newer Catalyst applications tend to use the Chained
0416017e 398dispatch form of action types because of its power and flexibility.
4d63a0d5 399It allows a series of controller methods to be automatically dispatched
0416017e 400to service a single user request. See
3ab6187c 401L<Catalyst::Manual::Tutorial::04_BasicCRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
0416017e 402and L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>
403for more information on chained actions.
407You should refer to L<Catalyst::Manual::Intro/Action_types> for
408additional information and for coverage of some lesser-used action
245b41d1 409types not discussed here (C<Regex> and C<LocalRegex>).
3533daff 410
4d63a0d5 414As mentioned in Chapter 2 of the tutorial, views are where you render
415output, typically for display in the user's web browser (but also
416possibly using into output-generation systems, such as PDF or JSON).
417The code in C<lib/MyApp/View> selects the I<type> of view to use, with
418the actual rendering template found in the C<root> directory. As with
419virtually every aspect of Catalyst, options abound when it comes to the
420specific view technology you adopt inside your application. However,
421most Catalyst applications use the Template Toolkit, known as TT (for
422more information on TT, see L<>). Other
423somewhat popular view technologies include Mason
424(L<> and L<>) and
1390ef0e 425L<HTML::Template> (L<>).
428=head2 Create a Catalyst View
3533daff 429
444d6b27 430When using TT for the Catalyst view, the main helper script
431is L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT>.
432You may also come across references to
434but its use is now deprecated.
1390ef0e 435
436Enter the following command to enable the C<TT> style of view
3533daff 437rendering for this tutorial:
1edbdee6 439 $ script/ view HTML TT
3533daff 440 exists "/home/me/MyApp/script/../lib/MyApp/View"
441 exists "/home/me/MyApp/script/../t"
1edbdee6 442 created "/home/me/MyApp/script/../lib/MyApp/View/"
443 created "/home/me/MyApp/script/../t/view_HTML.t"
445This simply creates a view called C<HTML> in a file called C<> (the first
446argument). It is now up to you to decide how you want to structure your view
447layout. For the tutorial, we will start with a very simple TT template to
448initially demonstrate the concepts, but quickly migrate to a more typical
449"wrapper page" type of configuration (where the "wrapper" controls the overall
450"look and feel" of your site from a single file or set of files).
452Edit C<lib/MyApp/View/> and you should see that the default
1390ef0e 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:
f058768a 546 $ script/ -r
1390ef0e 547
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 --
f058768a 573 PRAGMA foreign_keys = ON;
3b1fa91b 574 CREATE TABLE book (
3533daff 575 id INTEGER PRIMARY KEY,
576 title TEXT ,
577 rating INTEGER
578 );
3b1fa91b 579 -- 'book_author' is a many-to-many join table between books & authors
580 CREATE TABLE book_author (
3533daff 583 PRIMARY KEY (book_id, author_id)
584 );
3b1fa91b 585 CREATE TABLE author (
3533daff 586 id INTEGER PRIMARY KEY,
587 first_name TEXT,
588 last_name TEXT
589 );
590 ---
591 --- Load some sample data
592 ---
3b1fa91b 593 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
594 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
595 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
596 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
597 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
598 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
599 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
600 INSERT INTO author VALUES (3, 'Christian', 'Degu');
601 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
602 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
603 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
604 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
605 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
606 INSERT INTO book_author VALUES (1, 1);
607 INSERT INTO book_author VALUES (1, 2);
608 INSERT INTO book_author VALUES (1, 3);
609 INSERT INTO book_author VALUES (2, 4);
610 INSERT INTO book_author VALUES (3, 5);
611 INSERT INTO book_author VALUES (4, 6);
612 INSERT INTO book_author VALUES (4, 7);
613 INSERT INTO book_author VALUES (5, 8);
3533daff 614
3533daff 615Then use the following command to build a C<myapp.db> SQLite database:
617 $ sqlite3 myapp.db < myapp01.sql
619If you need to create the database more than once, you probably want to
620issue the C<rm myapp.db> command to delete the database before you use
1390ef0e 621the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
3533daff 622
623Once the C<myapp.db> database file has been created and initialized, you
624can use the SQLite command line environment to do a quick dump of the
625database contents:
627 $ sqlite3 myapp.db
f058768a 628 SQLite version 3.6.22
3533daff 629 Enter ".help" for instructions
f058768a 630 Enter SQL statements terminated with a ";"
3b1fa91b 631 sqlite> select * from book;
3533daff 632 1|CCSP SNRS Exam Certification Guide|5
633 2|TCP/IP Illustrated, Volume 1|5
634 3|Internetworking with TCP/IP Vol.1|4
635 4|Perl Cookbook|5
636 5|Designing with Web Standards|5
637 sqlite> .q
638 $
3b1fa91b 642 $ sqlite3 myapp.db "select * from book"
3533daff 643 1|CCSP SNRS Exam Certification Guide|5
644 2|TCP/IP Illustrated, Volume 1|5
645 3|Internetworking with TCP/IP Vol.1|4
646 4|Perl Cookbook|5
647 5|Designing with Web Standards|5
649As with most other SQL tools, if you are using the full "interactive"
650environment you need to terminate your SQL commands with a ";" (it's not
651required if you do a single SQL statement on the command line). Use
652".q" to exit from SQLite from the SQLite interactive mode and return to
653your OS command prompt.
b66dd084 655Please note that here we have chosen to use 'singular' table names. This is
e586b5f4 656because the default inflection code for older versions of
b66dd084 657L<DBIx::Class::Schema::Loader> does NOT handle plurals. There has been much
658philosophical discussion on whether table names should be plural or singular.
659There is no one correct answer, as long as one makes a choice and remains
658b8c29 660consistent with it. If you prefer plural table names (e.g. you think that they
661are easier to read) then see the documentation in
662L<DBIx::Class::Schema::Loader::Base/naming> (version 0.05 or greater).
3b1fa91b 663
a6d800ac 664For using other databases, such as PostgreSQL or MySQL, see
3ab6187c 665L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices>.
3533daff 666
acbd7bdd 667
8a472b34 668=head1 DATABASE ACCESS WITH DBIx::Class
3533daff 669
27909ed4 670Catalyst can be used with virtually any form of datastore available
671via Perl. For example, L<Catalyst::Model::DBI|Catalyst::Model::DBI>
444d6b27 672can be used to access databases through the traditional Perl L<DBI>
27909ed4 673interface or you can use a model to access files of any type on the
674filesystem. However, most Catalyst applications use some form of
675object-relational mapping (ORM) technology to create objects
676associated with tables in a relational database. Matt Trout's
677L<DBIx::Class|DBIx::Class> (abbreviated as "DBIC") has rapidly emerged
678as the Perl-based ORM technology of choice. Most new Catalyst
a46b474e 679applications rely on DBIx::Class, as will this tutorial.
3533daff 680
a46b474e 681Although DBIx::Class has included support for a C<create=dynamic> mode
682to automatically read the database structure every time the
683application starts, it's use is no longer recommended. While it can
684make for "flashy" demos, the use of the C<create=static> mode we use
685below can be implemented just as quickly and provides many advantages
686(such as the ability to add your own methods to the overall DBIC
687framework, a technique that we see in Chapter 4).
3533daff 688
1390ef0e 689
a46b474e 690=head2 Make Sure You Have a Recent Version of the DBIx::Class Model
27909ed4 691
692First, let's be sure we have a recent version of the DBIC helper,
f058768a 693L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>, so
694that we can take advantage of some recent enhancements in how
695foreign keys are handled with SQLite. To check your version,
696run this command:
27909ed4 697
698 $ perl -MCatalyst::Model::DBIC::Schema -e \
699 'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
f33d1dd7 700 0.4
27909ed4 701
fce83e5f 702Please note the '\' above. Depending on your environment, you might
703be able to cut and paste the text as shown or need to remove the '\'
704character to that the command is all on a single line.
3b1fa91b 705
f33d1dd7 706If you are following along in Debian 5, you should have version 0.40 or
707higher (shown above as "0.4" with the tailing zero removed). If you have
708less than v0.39, you will need to run this command to install it
709directly from CPAN:
27909ed4 710
711 $ sudo cpan Catalyst::Model::DBIC::Schema
713And re-run the version print command to verify that you are now at
f058768a 7140.39 or higher.
716In addition, since we are using SQLite's foreign key support here,
717please be sure that you use version C<1.27> of L<DBD::SQLite> or later:
719 $ perl -MDBD::SQLite -e 'print "$DBD::SQLite::VERSION\n"'
720 1.29
722Upgrade if you are not at version C<1.27> or higher.
27909ed4 723
a46b474e 725=head2 Create Static DBIx::Class Schema Files
27909ed4 726
98fd8420 727Before you continue, make sure your C<myapp.db> database file is in
728the application's topmost directory. Now use the model helper with
729the C<create=static> option to read the database with
27909ed4 730L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
731automatically build the required files for us:
3533daff 732
4ab6212d 733 $ script/ model DB DBIC::Schema MyApp::Schema \
b66dd084 734 create=static dbi:SQLite:myapp.db \
735 on_connect_do="PRAGMA foreign_keys = ON"
1390ef0e 736 exists "/home/me/MyApp/script/../lib/MyApp/Model"
737 exists "/home/me/MyApp/script/../t"
27909ed4 738 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
739 Schema dump completed.
1390ef0e 740 created "/home/me/MyApp/script/../lib/MyApp/Model/"
741 created "/home/me/MyApp/script/../t/model_DB.t"
3533daff 742
fce83e5f 743Please note the '\' above. Depending on your environment, you might
744be able to cut and paste the text as shown or need to remove the '\'
745character to that the command is all on a single line.
3b1fa91b 746
27909ed4 747The C<script/> command breaks down like this:
749=over 4
751=item *
753C<DB> is the name of the model class to be created by the helper in
756=item *
758C<DBIC::Schema> is the type of the model to create.
760=item *
762C<MyApp::Schema> is the name of the DBIC schema file written to
765=item *
767C<create=static> causes
768L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
769load the schema as it runs and then write that information out
770into files.
772=item *
f058768a 774C<dbi:SQLite:myapp.db> is the standard DBI connect string
27909ed4 775for use with SQLite.
f058768a 777=item *
779And finally, the C<on_connect_do> string requests that
780L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> create
781foreign key relationships for us (this is not needed for databases such
782as PostgreSQL and MySQL, but is required for SQLite). If you take a look
783at C<lib/MyApp/Model/>, you will see that the SQLite pragma is
784propogated to the Model, so that SQLite's recent (and optional) foreign
785key enforcement is enabled at the start of every database connection.
27909ed4 789=back
791If you look in the C<lib/MyApp/> file, you will find that it
792only contains a call to the C<load_namespaces> method. You will also
793find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
794has a subdirectory called "Result". This "Result" subdirectory then
795has files named according to each of the tables in our simple database
3b1fa91b 796(C<>, C<>, and C<>). These three
a46b474e 797files are called "Result Classes" in DBIx::Class nomenclature. Although the
27909ed4 798Result Class files are named after tables in our database, the classes
799correspond to the I<row-level data> that is returned by DBIC (more on
800this later, especially in
3ab6187c 801L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
27909ed4 802
803The idea with the Result Source files created under
804C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
805edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
806warning. If you place all of your changes below that point in the
807file, you can regenerate the automatically created information at the
808top of each file should your database structure get updated.
810Also note the "flow" of the model information across the various files
811and directories. Catalyst will initially load the model from
812C<lib/MyApp/Model/>. This file contains a reference to
813C<lib/MyApp/>, so that file is loaded next. Finally, the
814call to C<load_namespaces> in C<> will load each of the
815"Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
816The final outcome is that Catalyst will dynamically create three
817table-specific Catalyst models every time the application starts (you
818can see these three model files listed in the debug output generated
819when you launch the application).
821B<NOTE:> Older versions of
822L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
a46b474e 823deprecated DBIx::Class C<load_classes> technique instead of the newer
27909ed4 824C<load_namspaces>. For new applications, please try to use
825C<load_namespaces> since it more easily supports a very useful DBIC
826technique called "ResultSet Classes." If you need to convert an
827existing application from "load_classes" to "load_namespaces," you can
b66dd084 828use this process to automate the migration, but first make sure you have
829version C<0.39> of L<Catalyst::Model::DBIC::Schema> and
830L<DBIx::Class::Schema::Loader> version C<0.05000> or later.
27909ed4 831
b66dd084 832 $ # Re-run the helper to upgrade for you
27909ed4 833 $ script/ model DB DBIC::Schema MyApp::Schema \
b66dd084 834 create=static naming=current use_namespaces=1 \
835 dbi:SQLite:myapp.db \
836 on_connect_do="PRAGMA foreign_keys = ON"
dc9a0503 837
f058768a 838
acbd7bdd 841Open C<lib/MyApp/Controller/> and un-comment the model code we
842left disabled earlier so that your version matches the following (un-
3b1fa91b 843comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
acbd7bdd 844and delete the next 2 lines):
1390ef0e 845
846 =head2 list
848 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
850 =cut
f058768a 852 sub list :Local {
1390ef0e 853 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
854 # 'Context' that's used to 'glue together' the various components
855 # that make up the application
856 my ($self, $c) = @_;
f058768a 858 # Retrieve all of the book records as book model objects and store
859 # in the stash where they can be accessed by the TT template
0ed3df53 860 $c->stash(books => [$c->model('DB::Book')->all]);
1390ef0e 861
862 # Set the TT template to use. You will almost always want to do this
863 # in your action methods (action methods respond to user input in
864 # your controllers).
61cb69fd 865 $c->stash(template => 'books/list.tt2');
1390ef0e 866 }
3b1fa91b 868B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
869above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
c93b5eaa 870two are equivalent. Either way, C<$c-E<gt>model> returns a
871L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
4d63a0d5 872against the database and iterating over the set of results that is
c93b5eaa 873returned.
875We are using the C<-E<gt>all> to fetch all of the books. DBIC
876supports a wide variety of more advanced operations to easily do
877things like filtering and sorting the results. For example, the
518f3851 878following could be used to sort the results by descending title:
c93b5eaa 879
3b1fa91b 880 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
c93b5eaa 881
882Some other examples are provided in
883L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
884additional information found at L<DBIx::Class::ResultSet/search>,
887and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
1390ef0e 888
890=head2 Test Run The Application
3533daff 891
1435672d 892First, let's enable an environment variable that causes DBIx::Class to
acbd7bdd 893dump the SQL statements used to access the database. This is a
1435672d 894helpful trick when you are trying to debug your database-oriented
f058768a 895code. Press C<Ctrl-C> to break out of the development server and
3533daff 897
898 $ export DBIC_TRACE=1
f058768a 899 $ script/ -r
f33d1dd7 900
4d63a0d5 901This assumes you are using bash as your shell -- adjust accordingly if
3533daff 902you are using a different shell (for example, under tcsh, use
903C<setenv DBIC_TRACE 1>).
d0496197 905B<NOTE:> You can also set this in your code using
3533daff 906C<$class-E<gt>storage-E<gt>debug(1);>. See
907L<DBIx::Class::Manual::Troubleshooting> for details (including options
4d63a0d5 908to log to a file instead of displaying to the Catalyst development server
3533daff 909log).
1390ef0e 911Then launch the Catalyst development server. The log output should
912display something like:
3533daff 913
f058768a 914 $ script/ -r
3533daff 915 [debug] Debug messages enabled
1390ef0e 916 [debug] Statistics enabled
3533daff 917 [debug] Loaded plugins:
918 .----------------------------------------------------------------------------.
a467a714 919 | Catalyst::Plugin::ConfigLoader 0.27 |
920 | Catalyst::Plugin::StackTrace 0.11 |
3533daff 921 '----------------------------------------------------------------------------'
923 [debug] Loaded dispatcher "Catalyst::Dispatcher"
924 [debug] Loaded engine "Catalyst::Engine::HTTP"
925 [debug] Found home "/home/me/MyApp"
45d511e0 926 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
3533daff 927 [debug] Loaded components:
928 .-----------------------------------------------------------------+----------.
929 | Class | Type |
930 +-----------------------------------------------------------------+----------+
931 | MyApp::Controller::Books | instance |
932 | MyApp::Controller::Root | instance |
d0496197 933 | MyApp::Model::DB | instance |
3b1fa91b 934 | MyApp::Model::DB::Author | class |
935 | MyApp::Model::DB::Book | class |
936 | MyApp::Model::DB::BookAuthor | class |
1edbdee6 937 | MyApp::View::HTML | instance |
3533daff 938 '-----------------------------------------------------------------+----------'
940 [debug] Loaded Private actions:
941 .----------------------+--------------------------------------+--------------.
942 | Private | Class | Method |
943 +----------------------+--------------------------------------+--------------+
944 | /default | MyApp::Controller::Root | default |
945 | /end | MyApp::Controller::Root | end |
1390ef0e 946 | /index | MyApp::Controller::Root | index |
3533daff 947 | /books/index | MyApp::Controller::Books | index |
948 | /books/list | MyApp::Controller::Books | list |
949 '----------------------+--------------------------------------+--------------'
951 [debug] Loaded Path actions:
952 .-------------------------------------+--------------------------------------.
953 | Path | Private |
954 +-------------------------------------+--------------------------------------+
1390ef0e 955 | / | /default |
956 | / | /index |
957 | /books | /books/index |
3533daff 958 | /books/list | /books/list |
959 '-------------------------------------+--------------------------------------'
f058768a 961 [info] MyApp powered by Catalyst 5.80020
acbd7bdd 962 You can connect to your server at http://debian:3000
3533daff 963
1390ef0e 964B<NOTE:> Be sure you run the C<script/> command from
965the 'base' directory of your application, not inside the C<script>
966directory itself or it will not be able to locate the C<myapp.db>
967database file. You can use a fully qualified or a relative path to
968locate the database file, but we did not specify that when we ran the
3533daff 969model helper earlier.
971Some things you should note in the output above:
973=over 4
1390ef0e 975=item *
3533daff 976
1390ef0e 977Catalyst::Model::DBIC::Schema dynamically created three model classes,
978one to represent each of the three tables in our database
3b1fa91b 979(C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
980and C<MyApp::Model::DB::Book>).
3533daff 981
1390ef0e 982=item *
3533daff 983
984The "list" action in our Books controller showed up with a path of
989Point your browser to L<http://localhost:3000> and you should still get
990the Catalyst welcome page.
992Next, to view the book list, change the URL in your browser to
993L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 994books loaded by the C<myapp01.sql> script above without any formatting.
995The rating for each book should appear on each row, but the "Author(s)"
191dee29 996column will still be blank (we will fill that in later).
3533daff 997
a46b474e 998Also notice in the output of the C<script/> that
999DBIx::Class used the following SQL to retrieve the data:
3533daff 1000
fce83e5f 1001 SELECT, me.title, me.rating FROM book me
3533daff 1002
1003because we enabled DBIC_TRACE.
0c51850e 1005You now have the beginnings of a simple but workable web application.
3533daff 1006Continue on to future sections and we will develop the application
1007more fully.
1390ef0e 1010=head1 CREATE A WRAPPER FOR THE VIEW
acbd7bdd 1012When using TT, you can (and should) create a wrapper that will
1390ef0e 1013literally wrap content around each of your templates. This is
1014certainly useful as you have one main source for changing things that
1015will appear across your entire site/application instead of having to
1016edit many individual files.
1edbdee6 1019=head2 Configure For The Wrapper
1390ef0e 1020
1021In order to create a wrapper, you must first edit your TT view and
444d6b27 1022tell it where to find your wrapper file.
1390ef0e 1023
1edbdee6 1024Edit you TT view in C<lib/MyApp/View/> and change it to match the
444d6b27 1025following:
1390ef0e 1026
1027 __PACKAGE__->config(
1028 # Change default TT extension
1029 TEMPLATE_EXTENSION => '.tt2',
1030 # Set the location for TT files
1031 INCLUDE_PATH => [
c2dfb562 1032 MyApp->path_to( 'root', 'src' ),
1390ef0e 1033 ],
1034 # Set to 1 for detailed timer stats in your HTML as comments
1035 TIMER => 0,
1036 # This is your wrapper template located in the 'root/src'
1037 WRAPPER => 'wrapper.tt2',
1038 );
1041=head2 Create the Wrapper Template File and Stylesheet
1043Next you need to set up your wrapper template. Basically, you'll want
1044to take the overall layout of your site and put it into this file.
1045For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1047 <?xml version="1.0" encoding="UTF-8"?>
1048 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "">
1049 <html xmlns="" xml:lang="en" lang="en">
1050 <head>
1051 <title>[% template.title or "My Catalyst App!" %]</title>
1052 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1053 </head>
1055 <body>
1056 <div id="outer">
1057 <div id="header">
1058 [%# Your logo could go here -%]
1059 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1060 [%# Insert the page title -%]
1061 <h1>[% template.title or site.title %]</h1>
1062 </div>
1064 <div id="bodyblock">
1065 <div id="menu">
1066 Navigation:
1067 <ul>
1068 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1069 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1390ef0e 1070 </ul>
1071 </div><!-- end menu -->
1073 <div id="content">
1074 [%# Status and error messages %]
1075 <span class="message">[% status_msg %]</span>
1076 <span class="error">[% error_msg %]</span>
1077 [%# This is where TT will stick all of your template's contents. -%]
1078 [% content %]
1079 </div><!-- end content -->
1080 </div><!-- end bodyblock -->
1082 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 1083 </div><!-- end outer -->
1390ef0e 1084
1085 </body>
1086 </html>
1088Notice the status and error message sections in the code above:
1090 <span class="status">[% status_msg %]</span>
1091 <span class="error">[% error_msg %]</span>
1093If we set either message in the Catalyst stash (e.g.,
1094C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1095will be displayed whenever any view used by that request is rendered.
1096The C<message> and C<error> CSS styles can be customized to suit your
1097needs in the C<root/static/css/main.css> file we create below.
1101=over 4
1103=item *
1105The Catalyst stash only lasts for a single HTTP request. If
1106you need to retain information across requests you can use
1107L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
4b4d3884 1108Catalyst sessions in the Authentication chapter of the tutorial).
1390ef0e 1109
1110=item *
1112Although it is beyond the scope of this tutorial, you may wish to use
1113a JavaScript or AJAX tool such as jQuery (L<>) or
1114Dojo (L<>).
1119=head3 Create A Basic Stylesheet
1121First create a central location for stylesheets under the static
1124 $ mkdir root/static/css
1126Then open the file C<root/static/css/main.css> (the file referenced in
1127the stylesheet href link of our wrapper above) and add the following
1130 #header {
1131 text-align: center;
1132 }
1133 #header h1 {
1134 margin: 0;
1135 }
1136 #header img {
1137 float: right;
1138 }
1139 #footer {
1140 text-align: center;
1141 font-style: italic;
1142 padding-top: 20px;
1143 }
1144 #menu {
1145 font-weight: bold;
1146 background-color: #ddd;
1147 }
1148 #menu ul {
1149 list-style: none;
1150 float: left;
1151 margin: 0;
1152 padding: 0 0 50% 5px;
1153 font-weight: normal;
1154 background-color: #ddd;
1155 width: 100px;
1156 }
1157 #content {
1158 margin-left: 120px;
1159 }
1160 .message {
1161 color: #390;
1162 }
1163 .error {
1164 color: #f00;
1165 }
1167You may wish to check out a "CSS Framework" like Emastic
1168(L<>) as a way to quickly
1169provide lots of high-quality CSS functionality.
1172=head2 Test Run The Application
f058768a 1174Hit "Reload" in your web browser and you should now see a formatted
1175version of our basic book list. (Again, the development server should
1176have automatically restarted when you made changes to
1edbdee6 1177C<lib/MyApp/View/>. If you are not using the "-r" option, you will
f058768a 1178need to hit C<Ctrl-C> and manually restart it. Also note that the
1179development server does I<NOT> need to restart for changes to the TT and
1180static files we created and edited in the C<root> directory -- those
1181updates are handled on a per-request basis.)
1183Although our wrapper and stylesheet are obviously very simple, you
1184should see how it allows us to control the overall look of an entire
1185website from two central files. To add new pages to the site, just
1186provide a template that fills in the C<content> section of our wrapper
1187template -- the wrapper will provide the overall feel of the page.
1390ef0e 1188
a46b474e 1190=head2 Updating the Generated DBIx::Class Result Class Files
3533daff 1191
f058768a 1192If you take a look at the Schema files automatically generated by
1193L<DBIx::Class::Schema::Loader>, you will see that it has already defined
1194C<has_many> and C<belongs_to> relationships on each side of our foreign
1195keys. For example, take a look at C<lib/MyApp/Schema/Result/> and
1196notice the following code:
1198 =head1 RELATIONS
1200 =head2 book_authors
1202 Type: has_many
1204 Related object: L<MyApp::Schema::Result::BookAuthor>
1206 =cut
1208 __PACKAGE__->has_many(
1209 "book_authors",
1210 "MyApp::Schema::Result::BookAuthor",
1211 { "foreign.book_id" => "" },
1212 );
1214Each C<Book> "has_many" C<book_authors>, where C<BookAuthor> is
1215the many-to-many table that allows each Book to have multiple
1216Authors, and each Author to have mulitple books. The arguments
1217to C<has_many> are:
1219=over 4
1221=item *
1223C<book_authors> - The name for this relationship. DBIC will create
1224an accessor on the C<Books> DBIC Row object with this name.
1226=item *
1228C<MyApp::Schema::Result::BookAuthor> - The name of the DBIC model
1229class referenced by this C<has_many> relationship.
1231=item *
1233C<foreign.book_id> - C<book_id> is the name of the foreign key
1234column in the I<foreign> table that points back to this table.
1236=item *
1238C<> - C<id> is the name of the column in I<this> table
1239that is referenced by the foreign key.
1243See L<DBIx::Class::Relationship/has_many> for
1244additional information. Note that you might see a "hand coded"
1245version of the C<has_many> relationship above expressed as:
1247 __PACKAGE__->has_many(
1248 "book_authors",
1249 "MyApp::Schema::Result::BookAuthor",
1250 "book_id",
1251 );
1253Where the third argument is simply the name of the column in
1254the foreign table. However, the hashref syntax used by
1255L<DBIx::Class::Schema::Loader> is more flexible (for example,
1256it can handle "multi-column" foreign keys).
1258B<Note:> If you are using older versions of SQLite and related DBIC
1259tools, you will need to manually define your C<has_many> and
1260C<belongs_to> relationships. We recommend upgrading to the versions
1261specified above. :-)
1263Have a look at C<lib/MyApp/Schema/Result/> and notice
1264that there is a C<belongs_to> relationship defined that acts as the
1265"mirror image" to the C<has_many> relationship we just looked at
1268 =head1 RELATIONS
1270 =head2 book
1272 Type: belongs_to
1274 Related object: L<MyApp::Schema::Result::Book>
1276 =cut
1278 __PACKAGE__->belongs_to(
1279 "book",
1280 "MyApp::Schema::Result::Book",
1281 { id => "book_id" },
1282 { join_type => "LEFT" },
1283 );
f058768a 1285The arguments are similar, but see
1286L<DBIx::Class::Relationship/belongs_to> for the details.
f33d1dd7 1287
f058768a 1288Although recent versions of SQLite and L<DBIx::Class::Schema::Loader>
1289automatically handle the C<has_many> and C<belongs_to> relationships,
1290C<many_to_many> relationships currently need to be manually inserted.
1291To add a C<many_to_many> relationship, first edit
1292C<lib/MyApp/Schema/Result/> and add the following text below
1293the C<# You can replace this text...> comment:
3533daff 1294
3533daff 1295 # many_to_many():
1296 # args:
1297 # 1) Name of relationship, DBIC will create accessor with this name
1390ef0e 1298 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1299 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1300 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1301 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
3533daff 1302
3533daff 1303B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1304file. As with any Perl package, we need to end the last line with
1305a statement that evaluates to C<true>. This is customarily done with
1306C<1;> on a line by itself.
f058768a 1308The C<many_to_many> relationship is optional, but it makes it
b66dd084 1309easier to map a book to its collection of authors. Without
3b1fa91b 1310it, we would have to "walk" though the C<book_author> table as in
1311C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
a46b474e 1312will see examples on how to use DBIx::Class objects in your code soon,
3b1fa91b 1313but note that because C<$book-E<gt>book_author> can return multiple
1390ef0e 1314authors, we have to use C<first> to display a single author).
5a82cb36 1315C<many_to_many> allows us to use the shorter
1316C<$book-E<gt>author-E<gt>first-E<gt>last_name>. Note that you cannot
1317define a C<many_to_many> relationship without also having the
1318C<has_many> relationship in place.
3533daff 1319
f058768a 1320Then edit C<lib/MyApp/Schema/Result/> and add the reverse
1321C<many_to_many> relationship for C<Author> as follows (again, be careful
1322to put in above the C<1;> but below the C<# DO NOT MODIFY THIS OR
1323ANYTHING ABOVE!> comment):
3533daff 1324
3533daff 1325 # many_to_many():
1326 # args:
1327 # 1) Name of relationship, DBIC will create accessor with this name
1328 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1329 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1330 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1331 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
3533daff 1332
f058768a 1333
1390ef0e 1334=head2 Run The Application
3533daff 1335
4d63a0d5 1336Run the Catalyst development server script with the C<DBIC_TRACE> option
1337(it might still be enabled from earlier in the tutorial, but here is an
f33d1dd7 1338alternate way to specify the trace option just in case):
3533daff 1339
f058768a 1340 $ DBIC_TRACE=1 script/ -r
3533daff 1341
1390ef0e 1342Make sure that the application loads correctly and that you see the
1343three dynamically created model class (one for each of the
4ab6212d 1344Result Classes we created).
3533daff 1345
acbd7bdd 1346Then hit the URL L<http://localhost:3000/books/list> with your browser
f33d1dd7 1347and be sure that the book list still displays correctly.
3533daff 1348
c2dfb562 1349B<Note:> You will not see the authors yet because the view does not yet
1350use the new relations. Read on to the next section where we update the
1351template to do that.
3533daff 1352
acbd7bdd 1356Let's add a new column to our book list page that takes advantage of
1357the relationship information we manually added to our schema files in
a46b474e 1358the previous section. Edit C<root/src/books/list.tt2> and replace
3b1fa91b 1359the "empty" table cell "<td></td>" with the following:
3533daff 1360
acbd7bdd 1361 ...
3533daff 1362 <td>
fce83e5f 1363 [% # NOTE: See Chapter 4 for a better way to do this! -%]
3533daff 1364 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1365 [% # loop in 'side effect notation' to load just the last names of the -%]
6d97b973 1366 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
3533daff 1367 [% # a value, so nothing will be printed here. But, if you have something -%]
6d97b973 1368 [% # in TT that does return a value and you don't want it printed, you -%]
1369 [% # 1) assign it to a bogus value, or -%]
1370 [% # 2) use the CALL keyword to call it and discard the return value. -%]
3533daff 1371 [% tt_authors = [ ];
1372 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1373 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1374 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1375 ([% tt_authors.size | html %])
1376 [% # Use another TT vmethod to join & print the names & comma separators -%]
1377 [% tt_authors.join(', ') | html %]
1378 </td>
acbd7bdd 1379 ...
3533daff 1380
444d6b27 1381B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1382possible out of your views. This kind of logic belongs in your model
fce83e5f 1383(the same goes for controllers -- keep them as "thin" as possible and
1384push all of the "complicated code" out to your model objects). Avoid
1385code like you see in the previous example -- we are only using it here
1386to show some extra features in TT until we get to the more advanced
444d6b27 1387model features we will see in Chapter 4 (see
fce83e5f 1388L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1390ef0e 1390Then hit "Reload" in your browser (note that you don't need to reload
3533daff 1391the development server or use the C<-r> option when updating TT
1390ef0e 1392templates) and you should now see the number of authors each book has
1393along with a comma-separated list of the authors' last names. (If you
1394didn't leave the development server running from the previous step,
1395you will obviously need to start it before you can refresh your
1396browser window.)
1398If you are still running the development server with C<DBIC_TRACE>
1399enabled, you should also now see five more C<SELECT> statements in the
1400debug output (one for each book as the authors are being retrieved by
a46b474e 1401DBIx::Class):
3533daff 1402
fce83e5f 1403 SELECT, me.title, me.rating FROM book me:
3b1fa91b 1404 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1405 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '1'
3b1fa91b 1406 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1407 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '2'
3b1fa91b 1408 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1409 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '3'
3b1fa91b 1410 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1411 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '4'
3b1fa91b 1412 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1413 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '5'
c2dfb562 1414
1415Also note in C<root/src/books/list.tt2> that we are using "| html", a
1416type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1417and &gt; and avoid various types of dangerous hacks against your
1418application. In a real application, you would probably want to put
1419"| html" at the end of every field where a user has control over the
1420information that can appear in that field (and can therefore inject
1421markup or code if you don't "neutralize" those fields). In addition to
1422"| html", Template Toolkit has a variety of other useful filters that
1423can found in the documentation for
3533daff 1425
1429In some situations, it can be useful to run your application and
1430display a page without using a browser. Catalyst lets you do this
1431using the C<scripts/> script. Just supply the URL you
1432wish to display and it will run that request through the normal
1433controller dispatch logic and use the appropriate view to render the
1434output (obviously, complex pages may dump a lot of text to your
1435terminal window). For example, if you type:
1437 $ script/ "/books/list"
1439You should get the same text as if you visited
1440L<http://localhost:3000/books/list> with the normal development server
1441and asked your browser to view the page source.
3533daff 1442
1390ef0e 1443
4b4d3884 1446B<NOTE: The rest of this chapter of the tutorial is optional. You can
3ab6187c 1447skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
3533daff 1448if you wish.>
acbd7bdd 1450
8a472b34 1451=head2 Using 'RenderView' for the Default View
1390ef0e 1452
1453Once your controller logic has processed the request from a user, it
1454forwards processing to your view in order to generate the appropriate
3533daff 1455response output. Catalyst uses
1390ef0e 1456L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
4d63a0d5 1457default to automatically perform this operation. If you look in
1390ef0e 1458C<lib/MyApp/Controller/>, you should see the empty
3533daff 1459definition for the C<sub end> method:
1461 sub end : ActionClass('RenderView') {}
1390ef0e 1463The following bullet points provide a quick overview of the
3533daff 1464C<RenderView> process:
1466=over 4
1468=item *
1470C<> is designed to hold application-wide logic.
1472=item *
1390ef0e 1474At the end of a given user request, Catalyst will call the most specific
1475C<end> method that's appropriate. For example, if the controller for a
1476request has an C<end> method defined, it will be called. However, if
1477the controller does not define a controller-specific C<end> method, the
3533daff 1478"global" C<end> method in C<> will be called.
1480=item *
1482Because the definition includes an C<ActionClass> attribute, the
1483L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1484will be executed B<after> any code inside the definition of C<sub end>
1485is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1486for more information on C<ActionClass>.
1488=item *
1390ef0e 1490Because C<sub end> is empty, this effectively just runs the default
1491logic in C<RenderView>. However, you can easily extend the
1492C<RenderView> logic by adding your own code inside the empty method body
1493(C<{}>) created by the Catalyst Helpers when we first ran the
1494C<> to initialize our application. See
1495L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
4d63a0d5 1496detailed information on how to extend C<RenderView> in C<sub end>.
3533daff 1497
fce83e5f 1501=head2 RenderView's "dump_info" Feature
1503One of the nice features of C<RenderView> is that it automatically
1504allows you to add C<dump_info=1> to the end of any URL for your
1505application and it will force the display of the "exception dump"
6961c906 1506screen to the client browser. You can try this out by pointing
1507your browser to this URL:
fce83e5f 1508
1509 http://localhost:3000/books/list?dump_info=1
1511You should get a page with the following message at the top:
1513 Caught exception in MyApp::Controller::Root->end "Forced debug -
1514 Scrubbed output at /usr/share/perl5/Catalyst/Action/ line 46."
1516Along with a summary of your application's state at the end of the
1517processing for that request. The "Stash" section should show a
1518summarized version of the DBIC book model objects. If desired, you
1519can adjust the summarization logic (called "scrubbing" logic) -- see
1520L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for
1523Note that you shouldn't need to worry about "normal clients" using
1524this technique to "reverse engineer" your application -- C<RenderView>
1525only supports the C<dump_info=1> feature when your application is
1526running in C<-Debug> mode (something you won't do once you have your
1527application deployed in production).
3533daff 1530=head2 Using The Default Template Name
1390ef0e 1532By default, C<Catalyst::View::TT> will look for a template that uses the
1533same name as your controller action, allowing you to save the step of
1534manually specifying the template name in each action. For example, this
1535would allow us to remove the
1536C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1537C<list> action in the Books controller. Open
3533daff 1538C<lib/MyApp/Controller/> in your editor and comment out this line
1539to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1540has changed):
1542 =head2 list
1544 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1546 =cut
ddfbd850 1548 sub list :Local {
3533daff 1549 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1550 # 'Context' that's used to 'glue together' the various components
1551 # that make up the application
1552 my ($self, $c) = @_;
1554 # Retrieve all of the book records as book model objects and store in the
1555 # stash where they can be accessed by the TT template
0ed3df53 1556 $c->stash(books => [$c->model('DB::Book')->all]);
3533daff 1557
1558 # Set the TT template to use. You will almost always want to do this
1559 # in your action methods (actions methods respond to user input in
1560 # your controllers).
61cb69fd 1561 #$c->stash(template => 'books/list.tt2');
3533daff 1562 }
3533daff 1564
6961c906 1565You should now be able to access the L<http://localhost:3000/books/list>
1566URL as before.
3533daff 1567
1568B<NOTE:> Please note that if you use the default template technique,
1569you will B<not> be able to use either the C<$c-E<gt>forward> or
4b4d3884 1570the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1571Chapter 9 of the Tutorial).
3533daff 1572
3b1fa91b 1573B<IMPORTANT:> Make sure that you do NOT skip the following section
1574before continuing to the next chapter 4 Basic CRUD.
3533daff 1575
fce83e5f 1576
4d63a0d5 1577=head2 Return To A Manually Specified Template
3533daff 1578
1579In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1580later in the tutorial, you should remove the comment from the
1581statement in C<sub list> in C<lib/MyApp/Controller/>:
0ed3df53 1583 $c->stash(template => 'books/list.tt2');
3533daff 1584
1390ef0e 1585Then delete the C<TEMPLATE_EXTENSION> line in
1edbdee6 1586C<lib/MyApp/View/>.
3533daff 1587
6961c906 1588Check the L<http://localhost:3000/books/list> URL in your browser.
1589It should look the same manner as with earlier sections.
3533daff 1590
1592=head1 AUTHOR
1594Kennedy Clark, C<>
1596Please report any errors, issues or suggestions to the author. The
1597most recent version of the Catalyst Tutorial can be found at
59884771 1598L<>.
3533daff 1599
45c7830f 1600Copyright 2006-2008, Kennedy Clark, under Creative Commons License
8482d557 1601(L<>).