clarified docs on pural table naming
[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 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.
b66dd084 653Please note that here we have chosen to use 'singular' table names. This is
658b8c29 654because the default inflection code for older versions
b66dd084 655L<DBIx::Class::Schema::Loader> does NOT handle plurals. There has been much
656philosophical discussion on whether table names should be plural or singular.
657There is no one correct answer, as long as one makes a choice and remains
658b8c29 658consistent with it. If you prefer plural table names (e.g. you think that they
659are easier to read) then see the documentation in
660L<DBIx::Class::Schema::Loader::Base/naming> (version 0.05 or greater).
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
b66dd084 711Please use version C<1.27> of L<DBD::SQLite> or later for proper foreign key
27909ed4 713
a46b474e 714=head2 Create Static DBIx::Class Schema Files
27909ed4 715
98fd8420 716Before you continue, make sure your C<myapp.db> database file is in
717the application's topmost directory. Now use the model helper with
718the C<create=static> option to read the database with
27909ed4 719L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> and
720automatically build the required files for us:
3533daff 721
4ab6212d 722 $ script/ model DB DBIC::Schema MyApp::Schema \
b66dd084 723 create=static dbi:SQLite:myapp.db \
724 on_connect_do="PRAGMA foreign_keys = ON"
1390ef0e 725 exists "/home/me/MyApp/script/../lib/MyApp/Model"
726 exists "/home/me/MyApp/script/../t"
27909ed4 727 Dumping manual schema for MyApp::Schema to directory /home/me/MyApp/script/../lib ...
728 Schema dump completed.
1390ef0e 729 created "/home/me/MyApp/script/../lib/MyApp/Model/"
730 created "/home/me/MyApp/script/../t/model_DB.t"
3533daff 731
fce83e5f 732Please note the '\' above. Depending on your environment, you might
733be able to cut and paste the text as shown or need to remove the '\'
734character to that the command is all on a single line.
3b1fa91b 735
27909ed4 736The C<script/> command breaks down like this:
738=over 4
740=item *
742C<DB> is the name of the model class to be created by the helper in
745=item *
747C<DBIC::Schema> is the type of the model to create.
749=item *
751C<MyApp::Schema> is the name of the DBIC schema file written to
754=item *
756C<create=static> causes
757L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to
758load the schema as it runs and then write that information out
759into files.
761=item *
27909ed4 763And finally, C<dbi:SQLite:myapp.db> is the standard DBI connect string
764for use with SQLite.
768If you look in the C<lib/MyApp/> file, you will find that it
769only contains a call to the C<load_namespaces> method. You will also
770find that C<lib/MyApp> contains a C<Schema> subdirectory, which then
771has a subdirectory called "Result". This "Result" subdirectory then
772has files named according to each of the tables in our simple database
3b1fa91b 773(C<>, C<>, and C<>). These three
a46b474e 774files are called "Result Classes" in DBIx::Class nomenclature. Although the
27909ed4 775Result Class files are named after tables in our database, the classes
776correspond to the I<row-level data> that is returned by DBIC (more on
777this later, especially in
3ab6187c 778L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
27909ed4 779
780The idea with the Result Source files created under
781C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
782edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
783warning. If you place all of your changes below that point in the
784file, you can regenerate the automatically created information at the
785top of each file should your database structure get updated.
787Also note the "flow" of the model information across the various files
788and directories. Catalyst will initially load the model from
789C<lib/MyApp/Model/>. This file contains a reference to
790C<lib/MyApp/>, so that file is loaded next. Finally, the
791call to C<load_namespaces> in C<> will load each of the
792"Result Class" files from the C<lib/MyApp/Schema/Result> subdirectory.
793The final outcome is that Catalyst will dynamically create three
794table-specific Catalyst models every time the application starts (you
795can see these three model files listed in the debug output generated
796when you launch the application).
798B<NOTE:> Older versions of
799L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> use the
a46b474e 800deprecated DBIx::Class C<load_classes> technique instead of the newer
27909ed4 801C<load_namspaces>. For new applications, please try to use
802C<load_namespaces> since it more easily supports a very useful DBIC
803technique called "ResultSet Classes." If you need to convert an
804existing application from "load_classes" to "load_namespaces," you can
b66dd084 805use this process to automate the migration, but first make sure you have
806version C<0.39> of L<Catalyst::Model::DBIC::Schema> and
807L<DBIx::Class::Schema::Loader> version C<0.05000> or later.
27909ed4 808
b66dd084 809 $ # Re-run the helper to upgrade for you
27909ed4 810 $ script/ model DB DBIC::Schema MyApp::Schema \
b66dd084 811 create=static naming=current use_namespaces=1 \
812 dbi:SQLite:myapp.db \
813 on_connect_do="PRAGMA foreign_keys = ON"
dc9a0503 814
acbd7bdd 817Open C<lib/MyApp/Controller/> and un-comment the model code we
818left disabled earlier so that your version matches the following (un-
3b1fa91b 819comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
acbd7bdd 820and delete the next 2 lines):
1390ef0e 821
822 =head2 list
824 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
826 =cut
828 sub list : Local {
829 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
830 # 'Context' that's used to 'glue together' the various components
831 # that make up the application
832 my ($self, $c) = @_;
834 # Retrieve all of the book records as book model objects and store in the
835 # stash where they can be accessed by the TT template
3b1fa91b 836 $c->stash->{books} = [$c->model('DB::Book')->all];
1390ef0e 837
838 # Set the TT template to use. You will almost always want to do this
839 # in your action methods (action methods respond to user input in
840 # your controllers).
841 $c->stash->{template} = 'books/list.tt2';
842 }
3b1fa91b 844B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented
845above written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The
c93b5eaa 846two are equivalent. Either way, C<$c-E<gt>model> returns a
847L<DBIx::Class::ResultSet|DBIx::Class::ResultSet> which handles queries
4d63a0d5 848against the database and iterating over the set of results that is
c93b5eaa 849returned.
851We are using the C<-E<gt>all> to fetch all of the books. DBIC
852supports a wide variety of more advanced operations to easily do
853things like filtering and sorting the results. For example, the
518f3851 854following could be used to sort the results by descending title:
c93b5eaa 855
3b1fa91b 856 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
c93b5eaa 857
858Some other examples are provided in
859L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with
860additional information found at L<DBIx::Class::ResultSet/search>,
863and L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>.
1390ef0e 864
866=head2 Test Run The Application
3533daff 867
1435672d 868First, let's enable an environment variable that causes DBIx::Class to
acbd7bdd 869dump the SQL statements used to access the database. This is a
1435672d 870helpful trick when you are trying to debug your database-oriented
3533daff 872
873 $ export DBIC_TRACE=1
4d63a0d5 875This assumes you are using bash as your shell -- adjust accordingly if
3533daff 876you are using a different shell (for example, under tcsh, use
877C<setenv DBIC_TRACE 1>).
d0496197 879B<NOTE:> You can also set this in your code using
3533daff 880C<$class-E<gt>storage-E<gt>debug(1);>. See
881L<DBIx::Class::Manual::Troubleshooting> for details (including options
4d63a0d5 882to log to a file instead of displaying to the Catalyst development server
3533daff 883log).
1390ef0e 885Then launch the Catalyst development server. The log output should
886display something like:
3533daff 887
acbd7bdd 888 $ script/
3533daff 889 [debug] Debug messages enabled
1390ef0e 890 [debug] Statistics enabled
3533daff 891 [debug] Loaded plugins:
892 .----------------------------------------------------------------------------.
a467a714 893 | Catalyst::Plugin::ConfigLoader 0.27 |
894 | Catalyst::Plugin::StackTrace 0.11 |
895 | Catalyst::Plugin::Static::Simple 0.25 |
3533daff 896 '----------------------------------------------------------------------------'
898 [debug] Loaded dispatcher "Catalyst::Dispatcher"
899 [debug] Loaded engine "Catalyst::Engine::HTTP"
900 [debug] Found home "/home/me/MyApp"
45d511e0 901 [debug] Loaded Config "/home/me/MyApp/myapp.conf"
3533daff 902 [debug] Loaded components:
903 .-----------------------------------------------------------------+----------.
904 | Class | Type |
905 +-----------------------------------------------------------------+----------+
906 | MyApp::Controller::Books | instance |
907 | MyApp::Controller::Root | instance |
d0496197 908 | MyApp::Model::DB | instance |
3b1fa91b 909 | MyApp::Model::DB::Author | class |
910 | MyApp::Model::DB::Book | class |
911 | MyApp::Model::DB::BookAuthor | class |
3533daff 912 | MyApp::View::TT | instance |
913 '-----------------------------------------------------------------+----------'
915 [debug] Loaded Private actions:
916 .----------------------+--------------------------------------+--------------.
917 | Private | Class | Method |
918 +----------------------+--------------------------------------+--------------+
919 | /default | MyApp::Controller::Root | default |
920 | /end | MyApp::Controller::Root | end |
1390ef0e 921 | /index | MyApp::Controller::Root | index |
3533daff 922 | /books/index | MyApp::Controller::Books | index |
923 | /books/list | MyApp::Controller::Books | list |
924 '----------------------+--------------------------------------+--------------'
926 [debug] Loaded Path actions:
927 .-------------------------------------+--------------------------------------.
928 | Path | Private |
929 +-------------------------------------+--------------------------------------+
1390ef0e 930 | / | /default |
931 | / | /index |
932 | /books | /books/index |
3533daff 933 | /books/list | /books/list |
934 '-------------------------------------+--------------------------------------'
a467a714 936 [info] MyApp powered by Catalyst 5.80013
acbd7bdd 937 You can connect to your server at http://debian:3000
3533daff 938
1390ef0e 939B<NOTE:> Be sure you run the C<script/> command from
940the 'base' directory of your application, not inside the C<script>
941directory itself or it will not be able to locate the C<myapp.db>
942database file. You can use a fully qualified or a relative path to
943locate the database file, but we did not specify that when we ran the
3533daff 944model helper earlier.
946Some things you should note in the output above:
948=over 4
1390ef0e 950=item *
3533daff 951
1390ef0e 952Catalyst::Model::DBIC::Schema dynamically created three model classes,
953one to represent each of the three tables in our database
3b1fa91b 954(C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>,
955and C<MyApp::Model::DB::Book>).
3533daff 956
1390ef0e 957=item *
3533daff 958
959The "list" action in our Books controller showed up with a path of
964Point your browser to L<http://localhost:3000> and you should still get
965the Catalyst welcome page.
967Next, to view the book list, change the URL in your browser to
968L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 969books loaded by the C<myapp01.sql> script above without any formatting.
970The rating for each book should appear on each row, but the "Author(s)"
191dee29 971column will still be blank (we will fill that in later).
3533daff 972
a46b474e 973Also notice in the output of the C<script/> that
974DBIx::Class used the following SQL to retrieve the data:
3533daff 975
fce83e5f 976 SELECT, me.title, me.rating FROM book me
3533daff 977
978because we enabled DBIC_TRACE.
0c51850e 980You now have the beginnings of a simple but workable web application.
3533daff 981Continue on to future sections and we will develop the application
982more fully.
1390ef0e 985=head1 CREATE A WRAPPER FOR THE VIEW
acbd7bdd 987When using TT, you can (and should) create a wrapper that will
1390ef0e 988literally wrap content around each of your templates. This is
989certainly useful as you have one main source for changing things that
990will appear across your entire site/application instead of having to
991edit many individual files.
994=head2 Configure For The Wrapper
996In order to create a wrapper, you must first edit your TT view and
444d6b27 997tell it where to find your wrapper file.
1390ef0e 998
444d6b27 999Edit you TT view in C<lib/MyApp/View/> and change it to match the
1390ef0e 1001
1002 __PACKAGE__->config(
1003 # Change default TT extension
1004 TEMPLATE_EXTENSION => '.tt2',
1005 # Set the location for TT files
1006 INCLUDE_PATH => [
c2dfb562 1007 MyApp->path_to( 'root', 'src' ),
1390ef0e 1008 ],
1009 # Set to 1 for detailed timer stats in your HTML as comments
1010 TIMER => 0,
1011 # This is your wrapper template located in the 'root/src'
1012 WRAPPER => 'wrapper.tt2',
1013 );
1016=head2 Create the Wrapper Template File and Stylesheet
1018Next you need to set up your wrapper template. Basically, you'll want
1019to take the overall layout of your site and put it into this file.
1020For the tutorial, open C<root/src/wrapper.tt2> and input the following:
1022 <?xml version="1.0" encoding="UTF-8"?>
1023 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "">
1024 <html xmlns="" xml:lang="en" lang="en">
1025 <head>
1026 <title>[% template.title or "My Catalyst App!" %]</title>
1027 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1028 </head>
1030 <body>
1031 <div id="outer">
1032 <div id="header">
1033 [%# Your logo could go here -%]
1034 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1035 [%# Insert the page title -%]
1036 <h1>[% template.title or site.title %]</h1>
1037 </div>
1039 <div id="bodyblock">
1040 <div id="menu">
1041 Navigation:
1042 <ul>
1043 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
1044 <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li>
1390ef0e 1045 </ul>
1046 </div><!-- end menu -->
1048 <div id="content">
1049 [%# Status and error messages %]
1050 <span class="message">[% status_msg %]</span>
1051 <span class="error">[% error_msg %]</span>
1052 [%# This is where TT will stick all of your template's contents. -%]
1053 [% content %]
1054 </div><!-- end content -->
1055 </div><!-- end bodyblock -->
1057 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 1058 </div><!-- end outer -->
1390ef0e 1059
1060 </body>
1061 </html>
1063Notice the status and error message sections in the code above:
1065 <span class="status">[% status_msg %]</span>
1066 <span class="error">[% error_msg %]</span>
1068If we set either message in the Catalyst stash (e.g.,
1069C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it
1070will be displayed whenever any view used by that request is rendered.
1071The C<message> and C<error> CSS styles can be customized to suit your
1072needs in the C<root/static/css/main.css> file we create below.
1076=over 4
1078=item *
1080The Catalyst stash only lasts for a single HTTP request. If
1081you need to retain information across requests you can use
1082L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use
4b4d3884 1083Catalyst sessions in the Authentication chapter of the tutorial).
1390ef0e 1084
1085=item *
1087Although it is beyond the scope of this tutorial, you may wish to use
1088a JavaScript or AJAX tool such as jQuery (L<>) or
1089Dojo (L<>).
1094=head3 Create A Basic Stylesheet
1096First create a central location for stylesheets under the static
1099 $ mkdir root/static/css
1101Then open the file C<root/static/css/main.css> (the file referenced in
1102the stylesheet href link of our wrapper above) and add the following
1105 #header {
1106 text-align: center;
1107 }
1108 #header h1 {
1109 margin: 0;
1110 }
1111 #header img {
1112 float: right;
1113 }
1114 #footer {
1115 text-align: center;
1116 font-style: italic;
1117 padding-top: 20px;
1118 }
1119 #menu {
1120 font-weight: bold;
1121 background-color: #ddd;
1122 }
1123 #menu ul {
1124 list-style: none;
1125 float: left;
1126 margin: 0;
1127 padding: 0 0 50% 5px;
1128 font-weight: normal;
1129 background-color: #ddd;
1130 width: 100px;
1131 }
1132 #content {
1133 margin-left: 120px;
1134 }
1135 .message {
1136 color: #390;
1137 }
1138 .error {
1139 color: #f00;
1140 }
1142You may wish to check out a "CSS Framework" like Emastic
1143(L<>) as a way to quickly
1144provide lots of high-quality CSS functionality.
1147=head2 Test Run The Application
1149Restart the development server and hit "Reload" in your web browser
1150and you should now see a formatted version of our basic book list.
1151Although our wrapper and stylesheet are obviously very simple, you
1152should see how it allows us to control the overall look of an entire
1153website from two central files. To add new pages to the site, just
1154provide a template that fills in the C<content> section of our wrapper
1155template -- the wrapper will provide the overall feel of the page.
a46b474e 1158=head2 Updating the Generated DBIx::Class Result Class Files
3533daff 1159
acbd7bdd 1160Let's manually add some relationship information to the auto-generated
b66dd084 1161Result Class files. C<many_to_many> relationships are not currently
1162automatically generated by L<DBIx::Class::Schema::Loader>.
1163First edit C<lib/MyApp/Schema/Result/> and add the
acbd7bdd 1164following text below the C<# You can replace this text...> comment:
3533daff 1165
3533daff 1166 # many_to_many():
1167 # args:
1168 # 1) Name of relationship, DBIC will create accessor with this name
1390ef0e 1169 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1170 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1171 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1172 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
3533daff 1173
3533daff 1174B<Note:> Be careful to put this code I<above> the C<1;> at the end of the
1175file. As with any Perl package, we need to end the last line with
1176a statement that evaluates to C<true>. This is customarily done with
1177C<1;> on a line by itself.
b66dd084 1179You'll notice there is already a C<has_many> relationship called
1180C<book_authors>. The C<many_to_many> relationship is optional, but it makes it
1181easier to map a book to its collection of authors. Without
3b1fa91b 1182it, we would have to "walk" though the C<book_author> table as in
1183C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we
a46b474e 1184will see examples on how to use DBIx::Class objects in your code soon,
3b1fa91b 1185but note that because C<$book-E<gt>book_author> can return multiple
1390ef0e 1186authors, we have to use C<first> to display a single author).
5a82cb36 1187C<many_to_many> allows us to use the shorter
1188C<$book-E<gt>author-E<gt>first-E<gt>last_name>. Note that you cannot
1189define a C<many_to_many> relationship without also having the
1190C<has_many> relationship in place.
3533daff 1191
3b1fa91b 1192Then edit C<lib/MyApp/Schema/Result/> and add relationship
3533daff 1193information as follows (again, be careful to put in above the C<1;> but
1194below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment):
3533daff 1196 # many_to_many():
1197 # args:
1198 # 1) Name of relationship, DBIC will create accessor with this name
1199 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1200 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1201 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1202 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
3533daff 1203
1390ef0e 1204=head2 Run The Application
3533daff 1205
4d63a0d5 1206Run the Catalyst development server script with the C<DBIC_TRACE> option
1207(it might still be enabled from earlier in the tutorial, but here is an
1208alternate way to specify the option just in case):
3533daff 1209
1210 $ DBIC_TRACE=1 script/
1390ef0e 1212Make sure that the application loads correctly and that you see the
1213three dynamically created model class (one for each of the
4ab6212d 1214Result Classes we created).
3533daff 1215
acbd7bdd 1216Then hit the URL L<http://localhost:3000/books/list> with your browser
444d6b27 1217and be sure that the book list still displays correctly. You can leave
1218the development server running for the next step if you wish.
3533daff 1219
c2dfb562 1220B<Note:> You will not see the authors yet because the view does not yet
1221use the new relations. Read on to the next section where we update the
1222template to do that.
3533daff 1223
acbd7bdd 1227Let's add a new column to our book list page that takes advantage of
1228the relationship information we manually added to our schema files in
a46b474e 1229the previous section. Edit C<root/src/books/list.tt2> and replace
3b1fa91b 1230the "empty" table cell "<td></td>" with the following:
3533daff 1231
acbd7bdd 1232 ...
3533daff 1233 <td>
fce83e5f 1234 [% # NOTE: See Chapter 4 for a better way to do this! -%]
3533daff 1235 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1236 [% # loop in 'side effect notation' to load just the last names of the -%]
6d97b973 1237 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
3533daff 1238 [% # a value, so nothing will be printed here. But, if you have something -%]
6d97b973 1239 [% # in TT that does return a value and you don't want it printed, you -%]
1240 [% # 1) assign it to a bogus value, or -%]
1241 [% # 2) use the CALL keyword to call it and discard the return value. -%]
3533daff 1242 [% tt_authors = [ ];
1243 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1244 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1245 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1246 ([% tt_authors.size | html %])
1247 [% # Use another TT vmethod to join & print the names & comma separators -%]
1248 [% tt_authors.join(', ') | html %]
1249 </td>
acbd7bdd 1250 ...
3533daff 1251
444d6b27 1252B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1253possible out of your views. This kind of logic belongs in your model
fce83e5f 1254(the same goes for controllers -- keep them as "thin" as possible and
1255push all of the "complicated code" out to your model objects). Avoid
1256code like you see in the previous example -- we are only using it here
1257to show some extra features in TT until we get to the more advanced
444d6b27 1258model features we will see in Chapter 4 (see
fce83e5f 1259L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
1390ef0e 1261Then hit "Reload" in your browser (note that you don't need to reload
3533daff 1262the development server or use the C<-r> option when updating TT
1390ef0e 1263templates) and you should now see the number of authors each book has
1264along with a comma-separated list of the authors' last names. (If you
1265didn't leave the development server running from the previous step,
1266you will obviously need to start it before you can refresh your
1267browser window.)
1269If you are still running the development server with C<DBIC_TRACE>
1270enabled, you should also now see five more C<SELECT> statements in the
1271debug output (one for each book as the authors are being retrieved by
a46b474e 1272DBIx::Class):
3533daff 1273
fce83e5f 1274 SELECT, me.title, me.rating FROM book me:
3b1fa91b 1275 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1276 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '1'
3b1fa91b 1277 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1278 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '2'
3b1fa91b 1279 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1280 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '3'
3b1fa91b 1281 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1282 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '4'
3b1fa91b 1283 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1284 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '5'
c2dfb562 1285
1286Also note in C<root/src/books/list.tt2> that we are using "| html", a
1287type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1288and &gt; and avoid various types of dangerous hacks against your
1289application. In a real application, you would probably want to put
1290"| html" at the end of every field where a user has control over the
1291information that can appear in that field (and can therefore inject
1292markup or code if you don't "neutralize" those fields). In addition to
1293"| html", Template Toolkit has a variety of other useful filters that
1294can found in the documentation for
3533daff 1296
1300In some situations, it can be useful to run your application and
1301display a page without using a browser. Catalyst lets you do this
1302using the C<scripts/> script. Just supply the URL you
1303wish to display and it will run that request through the normal
1304controller dispatch logic and use the appropriate view to render the
1305output (obviously, complex pages may dump a lot of text to your
1306terminal window). For example, if you type:
1308 $ script/ "/books/list"
1310You should get the same text as if you visited
1311L<http://localhost:3000/books/list> with the normal development server
1312and asked your browser to view the page source.
3533daff 1313
1390ef0e 1314
4b4d3884 1317B<NOTE: The rest of this chapter of the tutorial is optional. You can
3ab6187c 1318skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
3533daff 1319if you wish.>
acbd7bdd 1321
8a472b34 1322=head2 Using 'RenderView' for the Default View
1390ef0e 1323
1324Once your controller logic has processed the request from a user, it
1325forwards processing to your view in order to generate the appropriate
3533daff 1326response output. Catalyst uses
1390ef0e 1327L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by
4d63a0d5 1328default to automatically perform this operation. If you look in
1390ef0e 1329C<lib/MyApp/Controller/>, you should see the empty
3533daff 1330definition for the C<sub end> method:
1332 sub end : ActionClass('RenderView') {}
1390ef0e 1334The following bullet points provide a quick overview of the
3533daff 1335C<RenderView> process:
1337=over 4
1339=item *
1341C<> is designed to hold application-wide logic.
1343=item *
1390ef0e 1345At the end of a given user request, Catalyst will call the most specific
1346C<end> method that's appropriate. For example, if the controller for a
1347request has an C<end> method defined, it will be called. However, if
1348the controller does not define a controller-specific C<end> method, the
3533daff 1349"global" C<end> method in C<> will be called.
1351=item *
1353Because the definition includes an C<ActionClass> attribute, the
1354L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic
1355will be executed B<after> any code inside the definition of C<sub end>
1356is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions>
1357for more information on C<ActionClass>.
1359=item *
1390ef0e 1361Because C<sub end> is empty, this effectively just runs the default
1362logic in C<RenderView>. However, you can easily extend the
1363C<RenderView> logic by adding your own code inside the empty method body
1364(C<{}>) created by the Catalyst Helpers when we first ran the
1365C<> to initialize our application. See
1366L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more
4d63a0d5 1367detailed information on how to extend C<RenderView> in C<sub end>.
3533daff 1368
fce83e5f 1372=head2 RenderView's "dump_info" Feature
1374One of the nice features of C<RenderView> is that it automatically
1375allows you to add C<dump_info=1> to the end of any URL for your
1376application and it will force the display of the "exception dump"
1377screen to the client browser. You can try this out by starting the
1378development server as before and then point your browser to this URL:
1380 http://localhost:3000/books/list?dump_info=1
1382You should get a page with the following message at the top:
1384 Caught exception in MyApp::Controller::Root->end "Forced debug -
1385 Scrubbed output at /usr/share/perl5/Catalyst/Action/ line 46."
1387Along with a summary of your application's state at the end of the
1388processing for that request. The "Stash" section should show a
1389summarized version of the DBIC book model objects. If desired, you
1390can adjust the summarization logic (called "scrubbing" logic) -- see
1391L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for
1394Note that you shouldn't need to worry about "normal clients" using
1395this technique to "reverse engineer" your application -- C<RenderView>
1396only supports the C<dump_info=1> feature when your application is
1397running in C<-Debug> mode (something you won't do once you have your
1398application deployed in production).
3533daff 1401=head2 Using The Default Template Name
1390ef0e 1403By default, C<Catalyst::View::TT> will look for a template that uses the
1404same name as your controller action, allowing you to save the step of
1405manually specifying the template name in each action. For example, this
1406would allow us to remove the
1407C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our
1408C<list> action in the Books controller. Open
3533daff 1409C<lib/MyApp/Controller/> in your editor and comment out this line
1410to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line
1411has changed):
1413 =head2 list
1415 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1417 =cut
1419 sub list : Local {
1420 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1421 # 'Context' that's used to 'glue together' the various components
1422 # that make up the application
1423 my ($self, $c) = @_;
1425 # Retrieve all of the book records as book model objects and store in the
1426 # stash where they can be accessed by the TT template
3b1fa91b 1427 $c->stash->{books} = [$c->model('DB::Book')->all];
3533daff 1428
1429 # Set the TT template to use. You will almost always want to do this
1430 # in your action methods (actions methods respond to user input in
1431 # your controllers).
1432 #$c->stash->{template} = 'books/list.tt2';
1433 }
3533daff 1435
1390ef0e 1436You should now be able to restart the development server as per the
3533daff 1437previous section and access the L<http://localhost:3000/books/list>
1438as before.
1440B<NOTE:> Please note that if you use the default template technique,
1441you will B<not> be able to use either the C<$c-E<gt>forward> or
4b4d3884 1442the C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
1443Chapter 9 of the Tutorial).
3533daff 1444
3b1fa91b 1445B<IMPORTANT:> Make sure that you do NOT skip the following section
1446before continuing to the next chapter 4 Basic CRUD.
3533daff 1447
fce83e5f 1448
4d63a0d5 1449=head2 Return To A Manually Specified Template
3533daff 1450
1451In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
1452later in the tutorial, you should remove the comment from the
1453statement in C<sub list> in C<lib/MyApp/Controller/>:
1455 $c->stash->{template} = 'books/list.tt2';
1390ef0e 1457Then delete the C<TEMPLATE_EXTENSION> line in
3533daff 1458C<lib/MyApp/View/>.
1390ef0e 1460You should then be able to restart the development server and
3533daff 1461access L<http://localhost:3000/books/list> in the same manner as
1462with earlier sections.
1465=head1 AUTHOR
1467Kennedy Clark, C<>
1469Please report any errors, issues or suggestions to the author. The
1470most recent version of the Catalyst Tutorial can be found at
59884771 1471L<>.
3533daff 1472
45c7830f 1473Copyright 2006-2008, Kennedy Clark, under Creative Commons License
8482d557 1474(L<>).