Some typos and minor style fixes.
[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
a8f4e284 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 virtually
65all web applications.
3533daff 66
477a6d5b 67Source code for the tutorial in included in the F</home/catalyst/Final>
68directory of the Tutorial Virtual machine (one subdirectory per
69chapter). There are also instructions for downloading the code in
2217b252 70L<Catalyst::Manual::Tutorial::01_Intro>.
3533daff 71
a8f4e284 72Please take a look at
01df1cc9 73L<Catalyst::Manual::Tutorial::01_Intro/STARTING WITH THE TUTORIAL VIRTUAL MACHINE>
74before doing the rest of this tutorial. Although the tutorial should
75work correctly under most any recent version of Perl running on any
76operating system, the tutorial has been written using the virtual
77machine that is available for download. The entire tutorial has been
78tested to be sure it runs correctly in this environment, so it is
79the most trouble-free way to get started with Catalyst.
a586a09f 80
3533daff 81
1390ef0e 84The remainder of the tutorial will build an application called C<MyApp>.
85First use the Catalyst C<> script to initialize the framework
86for the C<MyApp> application (make sure you aren't still inside the
4b4d3884 87directory of the C<Hello> application from the previous chapter of the
acbd7bdd 88tutorial or in a directory that already has a "MyApp" subdirectory):
3533daff 89
90 $ MyApp
91 created "MyApp"
92 created "MyApp/script"
93 created "MyApp/lib"
94 created "MyApp/root"
95 ...
96 created "MyApp/script/"
444d6b27 97 Change to application directory and Run "perl Makefile.PL" to make sure your install is complete
c988c8b0 98
99And change the "MyApp" directory the helper created:
3533daff 101 $ cd MyApp
4b4d3884 103This creates a similar skeletal structure to what we saw in Chapter 2 of
a8f4e284 104the tutorial, except with C<MyApp> and C<myapp> substituted for C<Hello>
105and C<hello>. (As noted in Chapter 2, omit the ".pl" from the command
106if you are using Strawberry Perl.)
3533daff 107
a8f4e284 111One of the greatest benefits of Catalyst is that it has such a large
be093944 112library of base classes and plugins available that you can use to easily
a8f4e284 113add functionality to your application. Plugins are used to seamlessly
114integrate existing Perl modules into the overall Catalyst framework. In
115general, they do this by adding additional methods to the C<context>
116object (generally written as C<$c>) that Catalyst passes to every
117component throughout the framework.
f058768a 118
c988c8b0 119Take a look at the file C<lib/> that the helper created above.
3533daff 120By default, Catalyst enables three plugins/flags:
122=over 4
1390ef0e 124=item *
3533daff 125
126C<-Debug> Flag
128Enables the Catalyst debug output you saw when we started the
129C<script/> development server earlier. You can remove
79a529cc 130this item when you place your application into production.
3533daff 131
a8f4e284 132To be technically correct, it turns out that C<-Debug> is not a plugin,
c988c8b0 133but a I<flag>. Although most of the items specified on the C<use
134Catalyst> line of your application class will be plugins, Catalyst
135supports a limited number of flag options (of these, C<-Debug> is the
136most common). See the documentation for
137C<|> to get details on
138other flags (currently C<-Engine>, C<-Home>, C<-Log>, and C<-Stats>).
3533daff 139
444d6b27 140If you prefer, there are several other ways to enable debug output:
142=over 4
144=item *
be093944 146the C<$c-E<gt>debug> method on the C<$c> Catalyst context object
444d6b27 147
148=item *
be093944 150the C<-d> option on the C<script/> script
444d6b27 151
152=item *
be093944 154the C<CATALYST_DEBUG=1> environment variable (or C<CATALYST_DEBUG=0>
155to temporarily disable debug output)
444d6b27 156
3533daff 158
a8f4e284 159B<TIP>: Depending on your needs, it can be helpful to permanently remove
160C<-Debug> from C<lib/> and then use the C<-d> option to
c988c8b0 161C<script/> to re-enable it when needed. We will not be
162using that approach in the tutorial, but feel free to make use of it in
163your own projects.
3533daff 164
165=item *
2217b252 167L<Catalyst::Plugin::ConfigLoader>
3533daff 168
169C<ConfigLoader> provides an automatic way to load configurable
c010ae0d 170parameters for your application from a central
2217b252 171L<Config::General> file (versus having the values
a8f4e284 172hard-coded inside your Perl modules). Config::General uses syntax very
173similar to Apache configuration files. We will see how to use this
174feature of Catalyst during the authentication and authorization sections
c988c8b0 175(L<Chapter 5|Catalyst::Manual::Tutorial::05_Authentication> and
176L<Chapter 6|Catalyst::Manual::Tutorial::06_Authorization>).
a8f4e284 177
178B<IMPORTANT NOTE:> If you are using a version of
2217b252 179L<Catalyst::Devel> prior to version 1.06, be aware that
a8f4e284 180Catalyst changed the default format from YAML to the more
181straightforward C<Config::General> style. This tutorial uses the newer
182C<myapp.conf> file for C<Config::General>. However, Catalyst supports
183both formats and will automatically use either C<myapp.conf> or
184C<myapp.yml> (or any other format supported by
2217b252 185L<Catalyst::Plugin::ConfigLoader> and
186L<Config::Any>). If you are using a version of
a8f4e284 187Catalyst::Devel prior to 1.06, you can convert to the newer format by
188simply creating the C<myapp.conf> file manually and deleting
189C<myapp.yml>. The default contents of the C<myapp.conf> you create
190should only consist of one line:
1435672d 191
192 name MyApp
15e1d0b2 193
1390ef0e 194B<TIP>: This script can be useful for converting between configuration
15e1d0b2 195formats:
1390ef0e 197 perl -Ilib -e 'use MyApp; use Config::General;
15e1d0b2 198 Config::General->new->save_file("myapp.conf", MyApp->config);'
3533daff 200=item *
2217b252 202L<Catalyst::Plugin::Static::Simple>
3533daff 203
a8f4e284 204C<Static::Simple> provides an easy way to serve static content, such as
205images and CSS files, from the development server.
3533daff 206
be093944 209For our application, we want to add one new plugin to the mix. To do
a8f4e284 210this, edit C<lib/> (this file is generally referred to as your
211I<application class>) and delete the lines with:
3533daff 212
1dc333c7 213 use Catalyst qw/
214 -Debug
215 ConfigLoader
216 Static::Simple
217 /;
3533daff 218
1390ef0e 219Then replace it with:
b411df01 220
acbd7bdd 221 # Load plugins
fce83e5f 222 use Catalyst qw/
1dc333c7 223 -Debug
224 ConfigLoader
225 Static::Simple
227 StackTrace
228 /;
1390ef0e 229
a8f4e284 230B<Note:> Recent versions of C<Catalyst::Devel> have used a variety of
231techniques to load these plugins/flags. For example, you might see the
94d8da41 233
acbd7bdd 234 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
94d8da41 235
a8f4e284 236Don't let these variations confuse you -- they all accomplish the same
94d8da41 237result.
a8f4e284 239This tells Catalyst to start using one additional plugin,
462f687d 240L<Catalyst::Plugin::StackTrace>, to add a stack trace near the top of
241the standard Catalyst "debug screen" (the screen Catalyst sends to your
242browser when an error occurs). Be aware that
a8f4e284 243L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your
244browser, not in the console window from which you're running your
1390ef0e 245application, which is where logging output usually goes.
3533daff 246
444d6b27 247Make sure when adding new plugins you also include them as a new
a8f4e284 248dependency within the Makefile.PL file. For example, after adding the
249StackTrace plugin the Makefile.PL should include the following line:
3b1fa91b 250
251 requires 'Catalyst::Plugin::StackTrace';
a8f4e284 254B<Notes:>
3533daff 255
256=over 4
1390ef0e 258=item *
a8f4e284 260C<__PACKAGE__> is just a shorthand way of referencing the name of the
261package where it is used. Therefore, in C<>, C<__PACKAGE__> is
262equivalent to C<MyApp>.
3533daff 263
1390ef0e 264=item *
3533daff 265
a8f4e284 266You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace>
267before you put your application into production, but it can be helpful
1390ef0e 268during development.
3533daff 269
1390ef0e 270=item *
3533daff 271
a8f4e284 272When specifying plugins, you can omit C<Catalyst::Plugin::> from the
273name. Additionally, you can spread the plugin names across multiple
444d6b27 274lines as shown here or place them all on one line.
cca5cd98 275
c988c8b0 276=item *
278If you want to see what the StackTrace error screen looks like, edit
279C<lib/MyApp/Controller/> and put a C<die "Oops";> command in the
280C<sub index :Path :Args(0)> method. Then start the development server
281and open C<http://localhost:3000/> in your browser. You should get a
282screen that starts with "Caught exception in
283MyApp::Controller::Root->index" with sections showing a stacktrace,
284information about the Request and Response objects, the stash (something
285we will learn about soon), the applications configuration configuration.
286B<Just don't forget to remove the die before you continue the tutorial!>
3533daff 289=back
3533daff 291
1390ef0e 294As discussed earlier, controllers are where you write methods that
295interact with user input. Typically, controller methods respond to
4d63a0d5 296C<GET> and C<POST> requests from the user's web browser.
3533daff 297
298Use the Catalyst C<create> script to add a controller for book-related
301 $ script/ controller Books
477a6d5b 302 exists "/home/catalyst/MyApp/script/../lib/MyApp/Controller"
303 exists "/home/catalyst/MyApp/script/../t"
304 created "/home/catalyst/MyApp/script/../lib/MyApp/Controller/"
305 created "/home/catalyst/MyApp/script/../t/controller_Books.t"
3533daff 306
c988c8b0 307Then edit C<lib/MyApp/Controller/> (as discussed in
308L<Chapter 2|Catalyst::Manual::Tutorial::02_CatalystBasics> of
1390ef0e 309the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for
be093944 310each of the three parts of MVC: C<Model>, C<View> and C<Controller>)
1390ef0e 311and add the following method to the controller:
3533daff 312
313 =head2 list
315 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
317 =cut
1390ef0e 318
f058768a 319 sub list :Local {
3533daff 320 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
321 # 'Context' that's used to 'glue together' the various components
322 # that make up the application
323 my ($self, $c) = @_;
325 # Retrieve all of the book records as book model objects and store in the
326 # stash where they can be accessed by the TT template
0ed3df53 327 # $c->stash(books => [$c->model('DB::Book')->all]);
1390ef0e 328 # But, for now, use this code until we create the model later
0ed3df53 329 $c->stash(books => '');
1390ef0e 330
3533daff 331 # Set the TT template to use. You will almost always want to do this
332 # in your action methods (action methods respond to user input in
333 # your controllers).
61cb69fd 334 $c->stash(template => 'books/list.tt2');
3533daff 335 }
c988c8b0 337B<TIP>: See L<Appendix 1|Catalyst::Manual::Tutorial::10_Appendices> for
338tips on removing the leading spaces when cutting and pasting example
339code from POD-based documents.
3533daff 340
a8f4e284 341Programmers experienced with object-oriented Perl should recognize
342C<$self> as a reference to the object where this method was called. On
343the other hand, C<$c> will be new to many Perl programmers who have not
c988c8b0 344used Catalyst before. This is the "Catalyst Context object", and it is
345automatically passed as the second argument to all Catalyst action
346methods. It is used to pass information between components and provide
347access to Catalyst and plugin functionality.
349Catalyst Controller actions are regular Perl methods, but they make use
350of attributes (the "C<:Local>" next to the "C<sub list>" in the code
351above) to provide additional information to the Catalyst dispatcher
352logic (note that there can be an optional space between the colon and
353the attribute name; you will see attributes written both ways). Most
354Catalyst Controllers use one of five action types:
0416017e 355
356=over 4
358=item *
a8f4e284 360B<:Private> -- Use C<:Private> for methods that you want to make into an
c988c8b0 361action, but you do not want Catalyst to directly expose the method to
a8f4e284 362your users. Catalyst will not map C<:Private> methods to a URI. Use
363them for various sorts of "special" methods (the C<begin>, C<auto>, etc.
364discussed below) or for methods you want to be able to C<forward> or
c988c8b0 365C<detach> to. (If the method is a "plain old method" that you
a8f4e284 366don't want to be an action at all, then just define the method without
367any attribute -- you can call it in your code, but the Catalyst
c988c8b0 368dispatcher will ignore it. You will also have to manually include
369C<$c> if you want access to the context object in the method vs. having
370Catalyst automatically include C<$c> in the argument list for you
371if it's a full-fledged action.)
0416017e 372
8fd01b0e 373There are five types of "special" built-in C<:Private> actions:
245b41d1 374C<begin>, C<end>, C<default>, C<index>, and C<auto>.
0416017e 375
26c9cad5 376=over 4
0416017e 378=item *
380With C<begin>, C<end>, C<default>, C<index> private actions, only the
381most specific action of each type will be called. For example, if you
382define a C<begin> action in your controller it will I<override> a
383C<begin> action in your application/root controller -- I<only> the
384action in your controller will be called.
386=item *
388Unlike the other actions where only a single method is called for each
389request, I<every> auto action along the chain of namespaces will be
390called. Each C<auto> action will be called I<from the application/root
391controller down through the most specific class>.
395=item *
a8f4e284 397B<:Path> -- C<:Path> actions let you map a method to an explicit URI
398path. For example, "C<:Path('list')>" in
399C<lib/MyApp/Controller/> would match on the URL
400C<http://localhost:3000/books/list>, but "C<:Path('/list')>" would match
401on C<http://localhost:3000/list> (because of the leading slash). You
402can use C<:Args()> to specify how many arguments an action should
403accept. See L<Catalyst::Manual::Intro/Action_types> for more
444d6b27 404information and examples.
0416017e 405
406=item *
a8f4e284 408B<:Local> -- C<:Local> is merely a shorthand for
245b41d1 409"C<:Path('_name_of_method_')>". For example, these are equivalent:
c988c8b0 410"C<sub create_book :Local {...}>" and
411"C<sub create_book :Path('create_book') {...}>".
245b41d1 412
413=item *
a8f4e284 415B<:Global> -- C<:Global> is merely a shorthand for
245b41d1 416"C<:Path('/_name_of_method_')>". For example, these are equivalent:
a8f4e284 417"C<sub create_book :Global {...}>" and "C<sub create_book
418:Path('/create_book') {...}>".
245b41d1 419
420=item *
a8f4e284 422B<:Chained> -- Newer Catalyst applications tend to use the Chained
423dispatch form of action types because of its power and flexibility. It
c988c8b0 424allows a series of controller methods to be automatically dispatched
425when servicing a single user request. See
426L<Catalyst::Manual::Tutorial::04_BasicCRUD> and
427L<Catalyst::DispatchType::Chained> for more information on chained
0416017e 429
c988c8b0 432You should refer to L<Catalyst::Manual::Intro/Action-types> for
a8f4e284 433additional information and for coverage of some lesser-used action types
434not discussed here (C<Regex> and C<LocalRegex>).
3533daff 435
c988c8b0 439As mentioned in L<Chapter 2|Catalyst::Manual::Tutorial::02_CatalystBasics>
440of the tutorial, views are where you render output, typically for
441display in the user's web browser (but can generate other types of
442output such as PDF or JSON). The code in C<lib/MyApp/View> selects the
443I<type> of view to use, with the actual rendering template found in the
444C<root> directory. As with virtually every aspect of Catalyst, options
445abound when it comes to the specific view technology you adopt inside
446your application. However, most Catalyst applications use the Template
447Toolkit, known as TT (for more information on TT, see
448L<>). Other somewhat popular view
449technologies include Mason (L<> and
450L<>) and L<HTML::Template>
1390ef0e 452
454=head2 Create a Catalyst View
3533daff 455
a8f4e284 456When using TT for the Catalyst view, the main helper script is
c988c8b0 457L<Catalyst::Helper::View::TT>. You may also come across references to
458L<Catalyst::Helper::View::TTSite>, but its use is now deprecated.
1390ef0e 459
c988c8b0 460For our book application, enter the following command to enable the
461C<TT> style of view rendering:
3533daff 462
1edbdee6 463 $ script/ view HTML TT
477a6d5b 464 exists "/home/catalyst/MyApp/script/../lib/MyApp/View"
465 exists "/home/catalyst/MyApp/script/../t"
466 created "/home/catalyst/MyApp/script/../lib/MyApp/View/"
467 created "/home/catalyst/MyApp/script/../t/view_HTML.t"
1edbdee6 468
c988c8b0 469This creates a view called C<HTML> (the first argument) in a file called
470C<> that uses L<Catalyst::View::TT> (the second argument) as the
471"rendering engine".
473It is now up to you to decide how you want to structure your view
474layout. For the tutorial, we will start with a very simple TT template
475to initially demonstrate the concepts, but quickly migrate to a more
476typical "wrapper page" type of configuration (where the "wrapper"
477controls the overall "look and feel" of your site from a single file or
478set of files).
1edbdee6 479
a8f4e284 480Edit C<lib/MyApp/View/> and you should see something similar to
481the following:
3533daff 482
c062293d 483 __PACKAGE__->config(
485 render_die => 1,
486 );
3533daff 487
1390ef0e 488And update it to match:
490 __PACKAGE__->config(
491 # Change default TT extension
c062293d 493 render_die => 1,
494 );
496This changes the default extension for Template Toolkit from '.tt' to
a8f4e284 499You can also configure components in your application class. For
c988c8b0 500example, Edit C<lib/> and you should see the default
501configuration above the call to C<_PACKAGE__-E<gt>setup> (your defaults
502could be different depending on the version of Catalyst you are using):
504 __PACKAGE__->config(
505 name => 'MyApp',
506 # Disable deprecated behavior needed by old applications
507 disable_component_resolution_regex_fallback => 1,
508 );
c062293d 509
c062293d 510
01df1cc9 511Change this to match the following (insert a new
512C<__PACKAGE__-E<gt>config> below the existing statement):
c062293d 513
514 __PACKAGE__->config(
c988c8b0 515 name => 'MyApp',
516 # Disable deprecated behavior needed by old applications
517 disable_component_resolution_regex_fallback => 1,
01df1cc9 518 );
519 __PACKAGE__->config(
c988c8b0 520 # Configure the view
c062293d 521 'View::HTML' => {
522 #Set the location for TT files
524 __PACKAGE__->path_to( 'root', 'src' ),
1390ef0e 525 ],
c062293d 526 },
1390ef0e 527 );
3533daff 528
a8f4e284 529This changes the base directory for your template files from C<root> to
1390ef0e 531
a8f4e284 532Please stick with the settings above for the duration of the tutorial,
533but feel free to use whatever options you desire in your applications
69d57cda 534(as with most things in Perl, there's more than one way to do it...).
1390ef0e 535
a8f4e284 536B<Note:> We will use C<root/src> as the base directory for our template
537files, with a full naming convention of
538C<root/src/_controller_name_/_action_name_.tt2>. Another popular option
539is to use C<root/> as the base (with a full filename pattern of
acbd7bdd 540C<root/_controller_name_/_action_name_.tt2>).
a8f4e284 542
1390ef0e 543=head2 Create a TT Template Page
3533daff 544
545First create a directory for book-related TT templates:
1390ef0e 547 $ mkdir -p root/src/books
3533daff 548
549Then create C<root/src/books/list.tt2> in your editor and enter:
c988c8b0 551 [% # This is a TT comment. -%]
3533daff 552
c988c8b0 553 [%- # Provide a title -%]
3533daff 554 [% META title = 'Book List' -%]
c988c8b0 556 [% # Note That the '-' at the beginning or end of TT code -%]
557 [% # "chomps" the whitespace/newline at that end of the -%]
558 [% # output (use View Source in browser to see the effect) -%]
560 [% # Some basic HTML with a loop to display books -%]
3533daff 561 <table>
562 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
563 [% # Display each book in a table row %]
564 [% FOREACH book IN books -%]
565 <tr>
566 <td>[% book.title %]</td>
567 <td>[% book.rating %]</td>
a46b474e 568 <td></td>
3533daff 569 </tr>
570 [% END -%]
571 </table>
573As indicated by the inline comments above, the C<META title> line uses
1390ef0e 574TT's META feature to provide a title to the "wrapper" that we will
c988c8b0 575create later (and essentially does nothing at the moment). Meanwhile,
576the C<FOREACH> loop iterates through each C<book> model object and
577prints the C<title> and C<rating> fields.
3533daff 578
4d63a0d5 579The C<[%> and C<%]> tags are used to delimit Template Toolkit code. TT
580supports a wide variety of directives for "calling" other files,
581looping, conditional logic, etc. In general, TT simplifies the usual
444d6b27 582range of Perl operators down to the single dot (".") operator. This
4d63a0d5 583applies to operations as diverse as method calls, hash lookups, and list
c988c8b0 584index values (see L<Template::Manual::Variables> for details and
89a65964 585examples). In addition to the usual L<Template::Toolkit> module Pod
4d63a0d5 586documentation, you can access the TT manual at
8c848468 587L<>.
3533daff 588
a8f4e284 589B<TIP:> While you can build all sorts of complex logic into your TT
590templates, you should in general keep the "code" part of your templates
591as simple as possible. If you need more complex logic, create helper
592methods in your model that abstract out a set of code into a single call
593from your TT template. (Note that the same is true of your controller
594logic as well -- complex sections of code in your controllers should
c988c8b0 595often be pulled out and placed into your model objects.) In
596L<Chapter 4|Catalyst::Manual::Tutorial::04_BasicCRUD> of the tutorial we
597will explore some extremely helpful and powerful features of
598L<DBIx::Class> that allow you to pull code out of your views and
599controllers and place it where it rightfully belongs in a model class.
1390ef0e 600
602=head2 Test Run The Application
604To test your work so far, first start the development server:
f058768a 606 $ script/ -r
1390ef0e 607
a8f4e284 608Then point your browser to L<http://localhost:3000> and you should still
609get the Catalyst welcome page. Next, change the URL in your browser to
610L<http://localhost:3000/books/list>. If you have everything working so
611far, you should see a web page that displays nothing other than our
612column headers for "Title", "Rating", and "Author(s)" -- we will not see
613any books until we get the database and model working below.
1390ef0e 614
615If you run into problems getting your application to run correctly, it
616might be helpful to refer to some of the debugging techniques covered in
fce83e5f 617the L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> chapter of the
1390ef0e 618tutorial.
3533daff 619
623In this step, we make a text file with the required SQL commands to
a8f4e284 624create a database table and load some sample data. We will use SQLite
625(L<>), a popular database that is lightweight and
626easy to use. Be sure to get at least version 3. Open C<myapp01.sql> in
627your editor and enter:
3533daff 628
629 --
630 -- Create a very simple database to hold book and author information
631 --
f058768a 632 PRAGMA foreign_keys = ON;
3b1fa91b 633 CREATE TABLE book (
3533daff 634 id INTEGER PRIMARY KEY,
635 title TEXT ,
636 rating INTEGER
637 );
3b1fa91b 638 -- 'book_author' is a many-to-many join table between books & authors
639 CREATE TABLE book_author (
3533daff 642 PRIMARY KEY (book_id, author_id)
643 );
3b1fa91b 644 CREATE TABLE author (
3533daff 645 id INTEGER PRIMARY KEY,
646 first_name TEXT,
647 last_name TEXT
648 );
649 ---
650 --- Load some sample data
651 ---
3b1fa91b 652 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
653 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
654 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
655 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
656 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
657 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
658 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
659 INSERT INTO author VALUES (3, 'Christian', 'Degu');
660 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
661 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
662 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
663 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
664 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
665 INSERT INTO book_author VALUES (1, 1);
666 INSERT INTO book_author VALUES (1, 2);
667 INSERT INTO book_author VALUES (1, 3);
668 INSERT INTO book_author VALUES (2, 4);
669 INSERT INTO book_author VALUES (3, 5);
670 INSERT INTO book_author VALUES (4, 6);
671 INSERT INTO book_author VALUES (4, 7);
672 INSERT INTO book_author VALUES (5, 8);
3533daff 673
3533daff 674Then use the following command to build a C<myapp.db> SQLite database:
676 $ sqlite3 myapp.db < myapp01.sql
678If you need to create the database more than once, you probably want to
679issue the C<rm myapp.db> command to delete the database before you use
1390ef0e 680the C<sqlite3 myapp.db E<lt> myapp01.sql> command.
3533daff 681
682Once the C<myapp.db> database file has been created and initialized, you
683can use the SQLite command line environment to do a quick dump of the
684database contents:
686 $ sqlite3 myapp.db
c988c8b0 687 SQLite version 3.7.3
3533daff 688 Enter ".help" for instructions
f058768a 689 Enter SQL statements terminated with a ";"
3b1fa91b 690 sqlite> select * from book;
3533daff 691 1|CCSP SNRS Exam Certification Guide|5
692 2|TCP/IP Illustrated, Volume 1|5
693 3|Internetworking with TCP/IP Vol.1|4
694 4|Perl Cookbook|5
695 5|Designing with Web Standards|5
696 sqlite> .q
697 $
3b1fa91b 701 $ sqlite3 myapp.db "select * from book"
3533daff 702 1|CCSP SNRS Exam Certification Guide|5
703 2|TCP/IP Illustrated, Volume 1|5
704 3|Internetworking with TCP/IP Vol.1|4
705 4|Perl Cookbook|5
706 5|Designing with Web Standards|5
708As with most other SQL tools, if you are using the full "interactive"
709environment you need to terminate your SQL commands with a ";" (it's not
710required if you do a single SQL statement on the command line). Use
711".q" to exit from SQLite from the SQLite interactive mode and return to
712your OS command prompt.
a8f4e284 714Please note that here we have chosen to use 'singular' table names. This
715is because the default inflection code for older versions of
716L<DBIx::Class::Schema::Loader> does NOT handle plurals. There has been
717much philosophical discussion on whether table names should be plural or
718singular. There is no one correct answer, as long as one makes a choice
719and remains consistent with it. If you prefer plural table names (e.g.
720you think that they are easier to read) then see the documentation in
658b8c29 721L<DBIx::Class::Schema::Loader::Base/naming> (version 0.05 or greater).
3b1fa91b 722
a8f4e284 723For using other databases, such as PostgreSQL or MySQL, see
3ab6187c 724L<Appendix 2|Catalyst::Manual::Tutorial::10_Appendices>.
3533daff 725
acbd7bdd 726
8a472b34 727=head1 DATABASE ACCESS WITH DBIx::Class
3533daff 728
a8f4e284 729Catalyst can be used with virtually any form of datastore available via
c988c8b0 730Perl. For example, L<Catalyst::Model::DBI> can be used to access
731databases through the traditional Perl L<DBI> interface or you can use a
732model to access files of any type on the filesystem. However, most
733Catalyst applications use some form of object-relational mapping (ORM)
734technology to create objects associated with tables in a relational
735database, and Matt Trout's L<DBIx::Class> (abbreviated as "DBIC") is the
736usual choice (this tutorial will use L<DBIx::Class>).
a8f4e284 737
738Although DBIx::Class has included support for a C<create=dynamic> mode
739to automatically read the database structure every time the application
740starts, its use is no longer recommended. While it can make for
741"flashy" demos, the use of the C<create=static> mode we use below can be
742implemented just as quickly and provides many advantages (such as the
743ability to add your own methods to the overall DBIC framework, a
c988c8b0 744technique that we see in
745L<Chapter 4|Catalyst::Manual::Tutorial::04_BasicCRUD>).
3533daff 746
1390ef0e 747
01df1cc9 748=head2 Create Static DBIx::Class Schema Files
27909ed4 749
01df1cc9 750B<Note:> If you are not following along in the Tutorial Virtual Machine,
751please be sure that you have version 1.27 or higher of DBD::SQLite and
752version 0.39 or higher of Catalyst::Model::DBIC::Schema. (The Tutorial
753VM already has versions that are known to work.) You can get your
754currently installed version numbers with the following commands.
27909ed4 755
c988c8b0 756 $ perl -MCatalyst::Model::DBIC::Schema\ 999
c988c8b0 757 $ perl -MDBD::SQLite\ 999
27909ed4 758
a8f4e284 759Before you continue, make sure your C<myapp.db> database file is in the
760application's topmost directory. Now use the model helper with the
761C<create=static> option to read the database with
2217b252 762L<DBIx::Class::Schema::Loader> and
27909ed4 763automatically build the required files for us:
3533daff 764
4ab6212d 765 $ script/ model DB DBIC::Schema MyApp::Schema \
b66dd084 766 create=static dbi:SQLite:myapp.db \
767 on_connect_do="PRAGMA foreign_keys = ON"
477a6d5b 768 exists "/home/catalyst/MyApp/script/../lib/MyApp/Model"
769 exists "/home/catalyst/MyApp/script/../t"
770 Dumping manual schema for MyApp::Schema to directory /home/catalyst/MyApp/script/../lib ...
27909ed4 771 Schema dump completed.
477a6d5b 772 created "/home/catalyst/MyApp/script/../lib/MyApp/Model/"
773 created "/home/catalyst/MyApp/script/../t/model_DB.t"
3533daff 774
a8f4e284 775Please note the '\' above. Depending on your environment, you might be
776able to cut and paste the text as shown or need to remove the '\'
fce83e5f 777character to that the command is all on a single line.
3b1fa91b 778
27909ed4 779The C<script/> command breaks down like this:
781=over 4
783=item *
a8f4e284 785C<DB> is the name of the model class to be created by the helper in
c988c8b0 786the C<lib/MyApp/Model> directory.
27909ed4 787
788=item *
c988c8b0 790C<DBIC::Schema> is the type of the model to create. This equates to
791L<Catalyst::Model::DBIC::Schema>, the standard way to use a DBIC-based
792model inside of Catalyst.
27909ed4 793
794=item *
796C<MyApp::Schema> is the name of the DBIC schema file written to
799=item *
c988c8b0 801C<create=static> causes L<DBIx::Class::Schema::Loader> to load the
802schema as it runs and then write that information out into
803C<lib/MyApp/> and files under the C<lib/MyApp/Schema>
27909ed4 805
806=item *
a8f4e284 808C<dbi:SQLite:myapp.db> is the standard DBI connect string for use with
27909ed4 810
f058768a 811=item *
a8f4e284 813And finally, the C<on_connect_do> string requests that
2217b252 814L<DBIx::Class::Schema::Loader> create
a8f4e284 815foreign key relationships for us (this is not needed for databases such
816as PostgreSQL and MySQL, but is required for SQLite). If you take a look
817at C<lib/MyApp/Model/>, you will see that the SQLite pragma is
c988c8b0 818propagated to the Model, so that SQLite's recent (and optional) foreign
a8f4e284 819key enforcement is enabled at the start of every database connection.
f058768a 820
27909ed4 821=back
01df1cc9 823
a8f4e284 824If you look in the C<lib/MyApp/> file, you will find that it
825only contains a call to the C<load_namespaces> method. You will also
826find that C<lib/MyApp> contains a C<Schema> subdirectory, which then has
827a subdirectory called "Result". This "Result" subdirectory then has
828files named according to each of the tables in our simple database
829(C<>, C<>, and C<>). These three files are
c988c8b0 830called "Result Classes" (or
831"L<ResultSource Classes|DBIx::Class::ResultSource>") in DBIx::Class
832nomenclature. Although the Result Class files are named after tables in
833our database, the classes correspond to the I<row-level data> that is
834returned by DBIC (more on this later, especially in
3ab6187c 835L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
27909ed4 836
a8f4e284 837The idea with the Result Source files created under
838C<lib/MyApp/Schema/Result> by the C<create=static> option is to only
839edit the files below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!>
840warning. If you place all of your changes below that point in the file,
841you can regenerate the automatically created information at the top of
842each file should your database structure get updated.
844Also note the "flow" of the model information across the various files
845and directories. Catalyst will initially load the model from
846C<lib/MyApp/Model/>. This file contains a reference to
847C<lib/MyApp/>, so that file is loaded next. Finally, the call
848to C<load_namespaces> in C<> will load each of the "Result
849Class" files from the C<lib/MyApp/Schema/Result> subdirectory. The
850final outcome is that Catalyst will dynamically create three
851table-specific Catalyst models every time the application starts (you
852can see these three model files listed in the debug output generated
27909ed4 853when you launch the application).
c988c8b0 855Additionally, the C<lib/MyApp/> model can easily be loaded
856outside of Catalyst, for example, in command-line utilities and/or cron
857jobs. C<lib/MyApp/Model/> provides a very thin "bridge" between
69d57cda 858Catalyst and this external database model. Once you see how we can
859add some powerful features to our DBIC model in
c988c8b0 860L<Chapter 4|Catalyst::Manual::Tutorial::04_BasicCRUD>, the elegance
861of this approach will start to become more obvious.
a8f4e284 863B<NOTE:> Older versions of
2217b252 864L<Catalyst::Model::DBIC::Schema> use the
a8f4e284 865deprecated DBIx::Class C<load_classes> technique instead of the newer
866C<load_namespaces>. For new applications, please try to use
867C<load_namespaces> since it more easily supports a very useful DBIC
868technique called "ResultSet Classes." If you need to convert an
869existing application from "load_classes" to "load_namespaces," you can
b66dd084 870use this process to automate the migration, but first make sure you have
871version C<0.39> of L<Catalyst::Model::DBIC::Schema> and
872L<DBIx::Class::Schema::Loader> version C<0.05000> or later.
27909ed4 873
b66dd084 874 $ # Re-run the helper to upgrade for you
27909ed4 875 $ script/ model DB DBIC::Schema MyApp::Schema \
b66dd084 876 create=static naming=current use_namespaces=1 \
877 dbi:SQLite:myapp.db \
878 on_connect_do="PRAGMA foreign_keys = ON"
dc9a0503 879
f058768a 880
a8f4e284 883Open C<lib/MyApp/Controller/> and un-comment the model code we
a1de5b65 884left disabled earlier so that your version matches the following
885(un-comment the line containing C<[$c-E<gt>model('DB::Book')-E<gt>all]>
886and delete the next 2 lines):
1390ef0e 887
888 =head2 list
890 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
892 =cut
f058768a 894 sub list :Local {
1390ef0e 895 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
896 # 'Context' that's used to 'glue together' the various components
897 # that make up the application
898 my ($self, $c) = @_;
f058768a 900 # Retrieve all of the book records as book model objects and store
901 # in the stash where they can be accessed by the TT template
0ed3df53 902 $c->stash(books => [$c->model('DB::Book')->all]);
1390ef0e 903
904 # Set the TT template to use. You will almost always want to do this
905 # in your action methods (action methods respond to user input in
906 # your controllers).
61cb69fd 907 $c->stash(template => 'books/list.tt2');
1390ef0e 908 }
a8f4e284 910B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> un-commented above
911written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The two are
912equivalent. Either way, C<$c-E<gt>model> returns a
2217b252 913L<DBIx::Class::ResultSet> which handles queries
a8f4e284 914against the database and iterating over the set of results that is
c93b5eaa 915returned.
a8f4e284 917We are using the C<-E<gt>all> to fetch all of the books. DBIC supports
918a wide variety of more advanced operations to easily do things like
919filtering and sorting the results. For example, the following could be
920used to sort the results by descending title:
c93b5eaa 921
3b1fa91b 922 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
c93b5eaa 923
a8f4e284 924Some other examples are provided in
925L<DBIx::Class::Manual::Cookbook/Complex WHERE clauses>, with additional
926information found at L<DBIx::Class::ResultSet/search>,
c988c8b0 927L<DBIx::Class::Manual::FAQ/Searching>, L<DBIx::Class::Manual::Intro> and
2217b252 928L<Catalyst::Model::DBIC::Schema>.
1390ef0e 929
931=head2 Test Run The Application
3533daff 932
c988c8b0 933First, let's enable an environment variable that causes L<DBIx::Class>
934to dump the SQL statements used to access the database. This is a
935helpful trick when you are trying to debug your database-oriented code.
936Press C<Ctrl-C> to break out of the development server and enter:
3533daff 937
938 $ export DBIC_TRACE=1
c988c8b0 939 $ script/ -r
f33d1dd7 940
4d63a0d5 941This assumes you are using bash as your shell -- adjust accordingly if
3533daff 942you are using a different shell (for example, under tcsh, use
943C<setenv DBIC_TRACE 1>).
d0496197 945B<NOTE:> You can also set this in your code using
3533daff 946C<$class-E<gt>storage-E<gt>debug(1);>. See
947L<DBIx::Class::Manual::Troubleshooting> for details (including options
a8f4e284 948to log to a file instead of displaying to the Catalyst development
949server log).
3533daff 950
1390ef0e 951Then launch the Catalyst development server. The log output should
952display something like:
3533daff 953
f058768a 954 $ script/ -r
3533daff 955 [debug] Debug messages enabled
1390ef0e 956 [debug] Statistics enabled
3533daff 957 [debug] Loaded plugins:
958 .----------------------------------------------------------------------------.
01df1cc9 959 | Catalyst::Plugin::ConfigLoader 0.30 |
a467a714 960 | Catalyst::Plugin::StackTrace 0.11 |
3533daff 961 '----------------------------------------------------------------------------'
963 [debug] Loaded dispatcher "Catalyst::Dispatcher"
01df1cc9 964 [debug] Loaded engine "Catalyst::Engine"
477a6d5b 965 [debug] Found home "/home/catalyst/MyApp"
966 [debug] Loaded Config "/home/catalyst/MyApp/myapp.conf"
3533daff 967 [debug] Loaded components:
968 .-----------------------------------------------------------------+----------.
969 | Class | Type |
970 +-----------------------------------------------------------------+----------+
971 | MyApp::Controller::Books | instance |
972 | MyApp::Controller::Root | instance |
d0496197 973 | MyApp::Model::DB | instance |
3b1fa91b 974 | MyApp::Model::DB::Author | class |
975 | MyApp::Model::DB::Book | class |
976 | MyApp::Model::DB::BookAuthor | class |
1edbdee6 977 | MyApp::View::HTML | instance |
3533daff 978 '-----------------------------------------------------------------+----------'
980 [debug] Loaded Private actions:
981 .----------------------+--------------------------------------+--------------.
982 | Private | Class | Method |
983 +----------------------+--------------------------------------+--------------+
984 | /default | MyApp::Controller::Root | default |
985 | /end | MyApp::Controller::Root | end |
1390ef0e 986 | /index | MyApp::Controller::Root | index |
3533daff 987 | /books/index | MyApp::Controller::Books | index |
988 | /books/list | MyApp::Controller::Books | list |
989 '----------------------+--------------------------------------+--------------'
991 [debug] Loaded Path actions:
992 .-------------------------------------+--------------------------------------.
993 | Path | Private |
994 +-------------------------------------+--------------------------------------+
1390ef0e 995 | / | /default |
996 | / | /index |
997 | /books | /books/index |
3533daff 998 | /books/list | /books/list |
999 '-------------------------------------+--------------------------------------'
f058768a 1001 [info] MyApp powered by Catalyst 5.80020
01df1cc9 1002 HTTP::Server::PSGI: Accepting connections at http://0:3000
3533daff 1003
a8f4e284 1004B<NOTE:> Be sure you run the C<script/> command from the
1005'base' directory of your application, not inside the C<script> directory
1006itself or it will not be able to locate the C<myapp.db> database file.
1007You can use a fully qualified or a relative path to locate the database
1008file, but we did not specify that when we ran the model helper earlier.
3533daff 1009
1010Some things you should note in the output above:
1012=over 4
1390ef0e 1014=item *
3533daff 1015
c988c8b0 1016L<Catalyst::Model::DBIC::Schema> dynamically created three model
1017classes, one to represent each of the three tables in our database
a8f4e284 1018(C<MyApp::Model::DB::Author>, C<MyApp::Model::DB::BookAuthor>, and
3533daff 1020
1390ef0e 1021=item *
3533daff 1022
1023The "list" action in our Books controller showed up with a path of
1028Point your browser to L<http://localhost:3000> and you should still get
1029the Catalyst welcome page.
1031Next, to view the book list, change the URL in your browser to
1032L<http://localhost:3000/books/list>. You should get a list of the five
1390ef0e 1033books loaded by the C<myapp01.sql> script above without any formatting.
1034The rating for each book should appear on each row, but the "Author(s)"
191dee29 1035column will still be blank (we will fill that in later).
3533daff 1036
a8f4e284 1037Also notice in the output of the C<script/> that
c988c8b0 1038L<DBIx::Class> used the following SQL to retrieve the data:
3533daff 1039
fce83e5f 1040 SELECT, me.title, me.rating FROM book me
3533daff 1041
1042because we enabled DBIC_TRACE.
0c51850e 1044You now have the beginnings of a simple but workable web application.
a8f4e284 1045Continue on to future sections and we will develop the application more
3533daff 1047
1390ef0e 1049=head1 CREATE A WRAPPER FOR THE VIEW
a8f4e284 1051When using TT, you can (and should) create a wrapper that will literally
1052wrap content around each of your templates. This is certainly useful as
1053you have one main source for changing things that will appear across
1054your entire site/application instead of having to edit many individual
1390ef0e 1056
1edbdee6 1058=head2 Configure For The Wrapper
1390ef0e 1059
a8f4e284 1060In order to create a wrapper, you must first edit your TT view and tell
1061it where to find your wrapper file.
1390ef0e 1062
a8f4e284 1063Edit your TT view in C<lib/MyApp/View/> and change it to match
1064the following:
1390ef0e 1065
1066 __PACKAGE__->config(
1067 # Change default TT extension
1068 TEMPLATE_EXTENSION => '.tt2',
1069 # Set the location for TT files
1070 INCLUDE_PATH => [
c2dfb562 1071 MyApp->path_to( 'root', 'src' ),
1390ef0e 1072 ],
1073 # Set to 1 for detailed timer stats in your HTML as comments
1074 TIMER => 0,
1075 # This is your wrapper template located in the 'root/src'
1076 WRAPPER => 'wrapper.tt2',
1077 );
1080=head2 Create the Wrapper Template File and Stylesheet
1082Next you need to set up your wrapper template. Basically, you'll want
a8f4e284 1083to take the overall layout of your site and put it into this file. For
1084the tutorial, open C<root/src/wrapper.tt2> and input the following:
1390ef0e 1085
1086 <?xml version="1.0" encoding="UTF-8"?>
c988c8b0 1087 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" [%#
1088 %]"">
1390ef0e 1089 <html xmlns="" xml:lang="en" lang="en">
1090 <head>
1091 <title>[% template.title or "My Catalyst App!" %]</title>
1092 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
1093 </head>
1095 <body>
1096 <div id="outer">
1097 <div id="header">
1098 [%# Your logo could go here -%]
1099 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
1100 [%# Insert the page title -%]
1101 <h1>[% template.title or site.title %]</h1>
1102 </div>
1104 <div id="bodyblock">
1105 <div id="menu">
1106 Navigation:
1107 <ul>
1108 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
c988c8b0 1109 <li><a href="[% c.uri_for('/')
1110 %]" title="Catalyst Welcome Page">Welcome</a></li>
1390ef0e 1111 </ul>
1112 </div><!-- end menu -->
1114 <div id="content">
1115 [%# Status and error messages %]
1116 <span class="message">[% status_msg %]</span>
1117 <span class="error">[% error_msg %]</span>
1118 [%# This is where TT will stick all of your template's contents. -%]
1119 [% content %]
1120 </div><!-- end content -->
1121 </div><!-- end bodyblock -->
1123 <div id="footer">Copyright (c) your name goes here</div>
c2dfb562 1124 </div><!-- end outer -->
1390ef0e 1125
1126 </body>
1127 </html>
1129Notice the status and error message sections in the code above:
1131 <span class="status">[% status_msg %]</span>
1132 <span class="error">[% error_msg %]</span>
1134If we set either message in the Catalyst stash (e.g.,
a8f4e284 1135C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it will
1136be displayed whenever any view used by that request is rendered. The
1137C<message> and C<error> CSS styles can be customized to suit your needs
1138in the C<root/static/css/main.css> file we create below.
1390ef0e 1139
a8f4e284 1140B<Notes:>
1390ef0e 1141
1142=over 4
1144=item *
a8f4e284 1146The Catalyst stash only lasts for a single HTTP request. If you need to
1147retain information across requests you can use
c988c8b0 1148L<Catalyst::Plugin::Session> (we will use Catalyst sessions in the
1149Authentication chapter of the tutorial).
1390ef0e 1150
1151=item *
a8f4e284 1153Although it is beyond the scope of this tutorial, you may wish to use a
1154JavaScript or AJAX tool such as jQuery (L<>) or
1390ef0e 1155Dojo (L<>).
1160=head3 Create A Basic Stylesheet
1162First create a central location for stylesheets under the static
1165 $ mkdir root/static/css
1167Then open the file C<root/static/css/main.css> (the file referenced in
1168the stylesheet href link of our wrapper above) and add the following
1171 #header {
1172 text-align: center;
1173 }
1174 #header h1 {
1175 margin: 0;
1176 }
1177 #header img {
1178 float: right;
1179 }
1180 #footer {
1181 text-align: center;
1182 font-style: italic;
1183 padding-top: 20px;
1184 }
1185 #menu {
1186 font-weight: bold;
1187 background-color: #ddd;
1188 }
1189 #menu ul {
1190 list-style: none;
1191 float: left;
1192 margin: 0;
1193 padding: 0 0 50% 5px;
1194 font-weight: normal;
1195 background-color: #ddd;
1196 width: 100px;
1197 }
1198 #content {
1199 margin-left: 120px;
1200 }
1201 .message {
1202 color: #390;
1203 }
1204 .error {
1205 color: #f00;
1206 }
1208You may wish to check out a "CSS Framework" like Emastic
a8f4e284 1209(L<>) as a way to quickly provide lots
1210of high-quality CSS functionality.
1390ef0e 1211
1213=head2 Test Run The Application
a8f4e284 1215Hit "Reload" in your web browser and you should now see a formatted
1216version of our basic book list. (Again, the development server should
1217have automatically restarted when you made changes to
1218C<lib/MyApp/View/>. If you are not using the "-r" option, you
1219will need to hit C<Ctrl-C> and manually restart it. Also note that the
1220development server does I<NOT> need to restart for changes to the TT and
1221static files we created and edited in the C<root> directory -- those
1222updates are handled on a per-request basis.)
f058768a 1223
a8f4e284 1224Although our wrapper and stylesheet are obviously very simple, you
1225should see how it allows us to control the overall look of an entire
1226website from two central files. To add new pages to the site, just
1227provide a template that fills in the C<content> section of our wrapper
1228template -- the wrapper will provide the overall feel of the page.
1390ef0e 1229
a46b474e 1231=head2 Updating the Generated DBIx::Class Result Class Files
3533daff 1232
a8f4e284 1233If you take a look at the Schema files automatically generated by
1234L<DBIx::Class::Schema::Loader>, you will see that it has already defined
1235C<has_many> and C<belongs_to> relationships on each side of our foreign
1236keys. For example, take a look at C<lib/MyApp/Schema/Result/> and
1237notice the following code:
f058768a 1238
1239 =head1 RELATIONS
c6b49844 1240
f058768a 1241 =head2 book_authors
c6b49844 1242
f058768a 1243 Type: has_many
c6b49844 1244
f058768a 1245 Related object: L<MyApp::Schema::Result::BookAuthor>
c6b49844 1246
f058768a 1247 =cut
c6b49844 1248
f058768a 1249 __PACKAGE__->has_many(
1250 "book_authors",
1251 "MyApp::Schema::Result::BookAuthor",
1252 { "foreign.book_id" => "" },
c988c8b0 1253 { cascade_copy => 0, cascade_delete => 0 },
f058768a 1254 );
a8f4e284 1256Each C<Book> "has_many" C<book_authors>, where C<BookAuthor> is the
1257many-to-many table that allows each Book to have multiple Authors, and
c988c8b0 1258each Author to have multiple books. The arguments to C<has_many> are:
f058768a 1259
1260=over 4
1262=item *
a8f4e284 1264C<book_authors> - The name for this relationship. DBIC will create an
1265accessor on the C<Books> DBIC Row object with this name.
f058768a 1266
1267=item *
a8f4e284 1269C<MyApp::Schema::Result::BookAuthor> - The name of the DBIC model class
1270referenced by this C<has_many> relationship.
f058768a 1271
1272=item *
a8f4e284 1274C<foreign.book_id> - C<book_id> is the name of the foreign key column in
1275the I<foreign> table that points back to this table.
f058768a 1276
1277=item *
a8f4e284 1279C<> - C<id> is the name of the column in I<this> table that is
1280referenced by the foreign key.
f058768a 1281
a8f4e284 1284See L<DBIx::Class::Relationship/has_many> for additional information.
1285Note that you might see a "hand coded" version of the C<has_many>
1286relationship above expressed as:
f058768a 1287
1288 __PACKAGE__->has_many(
1289 "book_authors",
1290 "MyApp::Schema::Result::BookAuthor",
1291 "book_id",
1292 );
a8f4e284 1294Where the third argument is simply the name of the column in the foreign
1295table. However, the hashref syntax used by
1296L<DBIx::Class::Schema::Loader> is more flexible (for example, it can
c988c8b0 1297handle "multi-column foreign keys").
f058768a 1298
a8f4e284 1299B<Note:> If you are using older versions of SQLite and related DBIC
1300tools, you will need to manually define your C<has_many> and
1301C<belongs_to> relationships. We recommend upgrading to the versions
1302specified above. :-)
f058768a 1303
a8f4e284 1304Have a look at C<lib/MyApp/Schema/Result/> and notice that
1305there is a C<belongs_to> relationship defined that acts as the "mirror
1306image" to the C<has_many> relationship we just looked at above:
f058768a 1307
1308 =head1 RELATIONS
c6b49844 1309
f058768a 1310 =head2 book
c6b49844 1311
f058768a 1312 Type: belongs_to
c6b49844 1313
f058768a 1314 Related object: L<MyApp::Schema::Result::Book>
c6b49844 1315
f058768a 1316 =cut
c6b49844 1317
f058768a 1318 __PACKAGE__->belongs_to(
1319 "book",
1320 "MyApp::Schema::Result::Book",
1321 { id => "book_id" },
c988c8b0 1322 { join_type => "LEFT", on_delete => "CASCADE", on_update => "CASCADE" },
f058768a 1323 );
a8f4e284 1325The arguments are similar, but see
f058768a 1326L<DBIx::Class::Relationship/belongs_to> for the details.
f33d1dd7 1327
a8f4e284 1328Although recent versions of SQLite and L<DBIx::Class::Schema::Loader>
1329automatically handle the C<has_many> and C<belongs_to> relationships,
7040a6cd 1330C<many_to_many> relationship bridges (not technically a relationship)
a8f4e284 1331currently need to be manually inserted. To add a C<many_to_many>
1332relationship bridge, first edit C<lib/MyApp/Schema/Result/> and
1333add the following text below the C<# You can replace this text...>
3533daff 1335
3533daff 1336 # many_to_many():
1337 # args:
7040a6cd 1338 # 1) Name of relationship bridge, DBIC will create accessor with this name
1390ef0e 1339 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1340 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1341 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1342 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
3533daff 1343
a8f4e284 1344B<Note:> Be careful to put this code I<above> the C<1;> at the end of
1345the file. As with any Perl package, we need to end the last line with a
1346statement that evaluates to C<true>. This is customarily done with
3533daff 1347C<1;> on a line by itself.
7040a6cd 1349The C<many_to_many> relationship bridge is optional, but it makes it
a8f4e284 1350easier to map a book to its collection of authors. Without it, we would
1351have to "walk" through the C<book_author> table as in
1352C<$book-E<gt>book_author-E<gt>first-E<gt>author-E<gt>last_name> (we will
1353see examples on how to use DBIx::Class objects in your code soon, but
1354note that because C<$book-E<gt>book_author> can return multiple authors,
1355we have to use C<first> to display a single author). C<many_to_many>
1356allows us to use the shorter
1357C<$book-E<gt>author-E<gt>first-E<gt>last_name>. Note that you cannot
1358define a C<many_to_many> relationship bridge without also having the
5a82cb36 1359C<has_many> relationship in place.
3533daff 1360
a8f4e284 1361Then edit C<lib/MyApp/Schema/Result/> and add the reverse
1362C<many_to_many> relationship bridge for C<Author> as follows (again, be
1363careful to put in above the C<1;> but below the C<# DO NOT MODIFY THIS
1364OR ANYTHING ABOVE!> comment):
3533daff 1365
3533daff 1366 # many_to_many():
1367 # args:
7040a6cd 1368 # 1) Name of relationship bridge, DBIC will create accessor with this name
3533daff 1369 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1390ef0e 1370 # 3) Name of belongs_to() relationship in model class of has_many() above
3533daff 1371 # You must already have the has_many() defined to use a many_to_many().
fce83e5f 1372 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
3533daff 1373
f058768a 1374
1390ef0e 1375=head2 Run The Application
3533daff 1376
4d63a0d5 1377Run the Catalyst development server script with the C<DBIC_TRACE> option
1378(it might still be enabled from earlier in the tutorial, but here is an
f33d1dd7 1379alternate way to specify the trace option just in case):
3533daff 1380
f058768a 1381 $ DBIC_TRACE=1 script/ -r
3533daff 1382
1390ef0e 1383Make sure that the application loads correctly and that you see the
a1de5b65 1384three dynamically created model classes (one for each of the Result
a8f4e284 1385Classes we created).
3533daff 1386
a8f4e284 1387Then hit the URL L<http://localhost:3000/books/list> with your browser
f33d1dd7 1388and be sure that the book list still displays correctly.
3533daff 1389
c988c8b0 1390B<Note:> You will not see the authors yet because the view isn't taking
1391advantage of these relationships. Read on to the next section where we
1392update the template to do that.
3533daff 1393
a8f4e284 1397Let's add a new column to our book list page that takes advantage of the
1398relationship information we manually added to our schema files in the
1399previous section. Edit C<root/src/books/list.tt2> and replace the
1400"empty" table cell "<td></td>" with the following:
3533daff 1401
acbd7bdd 1402 ...
3533daff 1403 <td>
fce83e5f 1404 [% # NOTE: See Chapter 4 for a better way to do this! -%]
3533daff 1405 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1406 [% # loop in 'side effect notation' to load just the last names of the -%]
6d97b973 1407 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
3533daff 1408 [% # a value, so nothing will be printed here. But, if you have something -%]
6d97b973 1409 [% # in TT that does return a value and you don't want it printed, you -%]
1410 [% # 1) assign it to a bogus value, or -%]
1411 [% # 2) use the CALL keyword to call it and discard the return value. -%]
3533daff 1412 [% tt_authors = [ ];
1413 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1414 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1415 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1416 ([% tt_authors.size | html %])
1417 [% # Use another TT vmethod to join & print the names & comma separators -%]
1418 [% tt_authors.join(', ') | html %]
1419 </td>
acbd7bdd 1420 ...
3533daff 1421
a8f4e284 1422B<IMPORTANT NOTE:> Again, you should keep as much "logic code" as
1423possible out of your views. This kind of logic belongs in your model
1424(the same goes for controllers -- keep them as "thin" as possible and
1425push all of the "complicated code" out to your model objects). Avoid
1426code like you see in the previous example -- we are only using it here
1427to show some extra features in TT until we get to the more advanced
1428model features we will see in Chapter 4 (see
fce83e5f 1429L<Catalyst::Manual::Tutorial::04_BasicCRUD/EXPLORING THE POWER OF DBIC>).
a8f4e284 1431Then hit "Reload" in your browser (note that you don't need to reload
1432the development server or use the C<-r> option when updating TT
1433templates) and you should now see the number of authors each book has
1434along with a comma-separated list of the authors' last names. (If you
1435didn't leave the development server running from the previous step, you
1436will obviously need to start it before you can refresh your browser
1390ef0e 1438
1439If you are still running the development server with C<DBIC_TRACE>
1440enabled, you should also now see five more C<SELECT> statements in the
1441debug output (one for each book as the authors are being retrieved by
a46b474e 1442DBIx::Class):
3533daff 1443
fce83e5f 1444 SELECT, me.title, me.rating FROM book me:
3b1fa91b 1445 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1446 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '1'
3b1fa91b 1447 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1448 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '2'
3b1fa91b 1449 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1450 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '3'
3b1fa91b 1451 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1452 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '4'
3b1fa91b 1453 SELECT, author.first_name, author.last_name FROM book_author me
fce83e5f 1454 JOIN author author ON = me.author_id WHERE ( me.book_id = ? ): '5'
c2dfb562 1455
a8f4e284 1456Also note in C<root/src/books/list.tt2> that we are using "| html", a
1457type of TT filter, to escape characters such as E<lt> and E<gt> to &lt;
1458and &gt; and avoid various types of dangerous hacks against your
1459application. In a real application, you would probably want to put "|
1460html" at the end of every field where a user has control over the
1461information that can appear in that field (and can therefore inject
1462markup or code if you don't "neutralize" those fields). In addition to
1463"| html", Template Toolkit has a variety of other useful filters that
a1de5b65 1464can be found in the documentation for L<Template::Filters>. (While we
1465are on the topic of security and escaping of dangerous values, one of
1466the advantages of using tools like DBIC for database access or
c988c8b0 1467L<HTML::FormFu> for form management [see
a1de5b65 1468L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD::09_FormFu>]
c988c8b0 1469is that they automatically handle most escaping for you and therefore
1470dramatically increase the security of your app.)
3533daff 1471
a8f4e284 1475In some situations, it can be useful to run your application and display
1476a page without using a browser. Catalyst lets you do this using the
1477C<scripts/> script. Just supply the URL you wish to
1478display and it will run that request through the normal controller
1479dispatch logic and use the appropriate view to render the output
1480(obviously, complex pages may dump a lot of text to your terminal
01df1cc9 1481window). For example, if C<Ctrl+C> out of the development server
1482and then type:
1390ef0e 1483
1484 $ script/ "/books/list"
1486You should get the same text as if you visited
1487L<http://localhost:3000/books/list> with the normal development server
c988c8b0 1488and asked your browser to view the page source. You can even pipe this
1489HTML text output to a text-based browser using a command like:
1491 $ script/ "/books/list" | lynx -stdin
1493And you should see a fully rendered text-based view of your page. (If
1494you are following along in Debian 6, type
1495C<sudo aptitude -y install lynx> to install lynx.) If you do start
1496lynx, you can use the "Q" key to quit.
3533daff 1497
1390ef0e 1498
4b4d3884 1501B<NOTE: The rest of this chapter of the tutorial is optional. You can
3ab6187c 1502skip to Chapter 4, L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>,
3533daff 1503if you wish.>
acbd7bdd 1505
8a472b34 1506=head2 Using 'RenderView' for the Default View
1390ef0e 1507
1508Once your controller logic has processed the request from a user, it
1509forwards processing to your view in order to generate the appropriate
3533daff 1510response output. Catalyst uses
2217b252 1511L<Catalyst::Action::RenderView> by default
a8f4e284 1512to automatically perform this operation. If you look in
1513C<lib/MyApp/Controller/>, you should see the empty definition for
1514the C<sub end> method:
3533daff 1515
1516 sub end : ActionClass('RenderView') {}
1390ef0e 1518The following bullet points provide a quick overview of the
3533daff 1519C<RenderView> process:
1521=over 4
1523=item *
1525C<> is designed to hold application-wide logic.
1527=item *
1390ef0e 1529At the end of a given user request, Catalyst will call the most specific
1530C<end> method that's appropriate. For example, if the controller for a
1531request has an C<end> method defined, it will be called. However, if
1532the controller does not define a controller-specific C<end> method, the
3533daff 1533"global" C<end> method in C<> will be called.
1535=item *
1537Because the definition includes an C<ActionClass> attribute, the
c988c8b0 1538L<Catalyst::Action::RenderView> logic will be executed B<after> any code
1539inside the definition of C<sub end> is run. See
1540L<Catalyst::Manual::Actions> for more information on C<ActionClass>.
3533daff 1541
1542=item *
1390ef0e 1544Because C<sub end> is empty, this effectively just runs the default
1545logic in C<RenderView>. However, you can easily extend the
1546C<RenderView> logic by adding your own code inside the empty method body
1547(C<{}>) created by the Catalyst Helpers when we first ran the
1548C<> to initialize our application. See
2217b252 1549L<Catalyst::Action::RenderView> for more
4d63a0d5 1550detailed information on how to extend C<RenderView> in C<sub end>.
3533daff 1551
fce83e5f 1555=head2 RenderView's "dump_info" Feature
a8f4e284 1557One of the nice features of C<RenderView> is that it automatically
1558allows you to add C<dump_info=1> to the end of any URL for your
1559application and it will force the display of the "exception dump" screen
1560to the client browser. You can try this out by pointing your browser to
1561this URL:
fce83e5f 1562
1563 http://localhost:3000/books/list?dump_info=1
1565You should get a page with the following message at the top:
1567 Caught exception in MyApp::Controller::Root->end "Forced debug -
1568 Scrubbed output at /usr/share/perl5/Catalyst/Action/ line 46."
a8f4e284 1570Along with a summary of your application's state at the end of the
1571processing for that request. The "Stash" section should show a
1572summarized version of the DBIC book model objects. If desired, you can
1573adjust the summarization logic (called "scrubbing" logic) -- see
2217b252 1574L<Catalyst::Action::RenderView> for
fce83e5f 1575details.
a8f4e284 1577Note that you shouldn't need to worry about "normal clients" using this
1578technique to "reverse engineer" your application -- C<RenderView> only
1579supports the C<dump_info=1> feature when your application is running in
1580C<-Debug> mode (something you won't do once you have your application
1581deployed in production).
fce83e5f 1582
3533daff 1584=head2 Using The Default Template Name
1390ef0e 1586By default, C<Catalyst::View::TT> will look for a template that uses the
1587same name as your controller action, allowing you to save the step of
1588manually specifying the template name in each action. For example, this
c988c8b0 1589would allow us to remove the
1590C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';>
1591line of our C<list> action in the Books controller.
a8f4e284 1592Open C<lib/MyApp/Controller/> in your editor and comment out
1593this line to match the following (only the
1594C<$c-E<gt>stash-E<gt>{template}> line has changed):
3533daff 1595
1596 =head2 list
1598 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1600 =cut
ddfbd850 1602 sub list :Local {
3533daff 1603 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1604 # 'Context' that's used to 'glue together' the various components
1605 # that make up the application
1606 my ($self, $c) = @_;
1608 # Retrieve all of the book records as book model objects and store in the
1609 # stash where they can be accessed by the TT template
0ed3df53 1610 $c->stash(books => [$c->model('DB::Book')->all]);
3533daff 1611
1612 # Set the TT template to use. You will almost always want to do this
1613 # in your action methods (actions methods respond to user input in
1614 # your controllers).
61cb69fd 1615 #$c->stash(template => 'books/list.tt2');
3533daff 1616 }
3533daff 1618
6961c906 1619You should now be able to access the L<http://localhost:3000/books/list>
1620URL as before.
3533daff 1621
a1de5b65 1622B<NOTE:> If you use the default template technique, you
a8f4e284 1623will B<not> be able to use either the C<$c-E<gt>forward> or the
1624C<$c-E<gt>detach> mechanisms (these are discussed in Chapter 2 and
4b4d3884 1625Chapter 9 of the Tutorial).
3533daff 1626
a1de5b65 1627B<IMPORTANT:> Make sure that you do B<not> skip the following section
3b1fa91b 1628before continuing to the next chapter 4 Basic CRUD.
3533daff 1629
fce83e5f 1630
4d63a0d5 1631=head2 Return To A Manually Specified Template
3533daff 1632
1633In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach>
a8f4e284 1634later in the tutorial, you should remove the comment from the statement
1635in C<sub list> in C<lib/MyApp/Controller/>:
3533daff 1636
0ed3df53 1637 $c->stash(template => 'books/list.tt2');
3533daff 1638
a8f4e284 1639Then delete the C<TEMPLATE_EXTENSION> line in C<lib/MyApp/View/>.
3533daff 1640
a8f4e284 1641Check the L<http://localhost:3000/books/list> URL in your browser. It
1642should look the same manner as with earlier sections.
3533daff 1643
24acc5d7 1645You can jump to the next chapter of the tutorial here:
1646L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>
3533daff 1649=head1 AUTHOR
1651Kennedy Clark, C<>
53243324 1653Feel free to contact the author for any errors or suggestions, but the
1654best way to report issues is via the CPAN RT Bug system at
bb0999d3 1655L<>.
53243324 1656
bb0999d3 1657Copyright 2006-2011, Kennedy Clark, under the
ec3ef4ad 1658Creative Commons Attribution Share-Alike License Version 3.0
8482d557 1659(L<>).