1Catalyst::Manual::TutorUisaelr:C:Ca0ot3na_tlMryoisrbteu:Ct:aeMtdaanlPuyeasrltl:B:aDTsouictcuosmr(ei3na)tla:t:i0o3n_MoreCatalystBasics(3)
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6 Catalyst::Manual::Tutorial::03_MoreCatalystBasics - Catalyst Tutorial -
7 Chapter 3: More Catalyst Application Development Basics
8
10 This is Chapter 3 of 10 for the Catalyst tutorial.
11 Tutorial Overview
13 1. Introduction
15 2. Catalyst Basics
17 3. 03_More Catalyst Basics
19 4. Basic CRUD
21 5. Authentication
23 6. Authorization
25 7. Debugging
27 8. Testing
29 9. Advanced CRUD
31 10. Appendices
33
35 This chapter of the tutorial builds on the work done in Chapter 2 to
36 explore some features that are more typical of "real world" web
37 applications. From this chapter of the tutorial onward, we will be
38 building a simple book database application. Although the application
39 will be too limited to be of use to anyone, it should provide a basic
40 environment where we can explore a variety of features used in
41 virtually all web applications.
42 Source code for the tutorial in included in the /home/catalyst/Final
44 directory of the Tutorial Virtual machine (one subdirectory per
45 chapter). There are also instructions for downloading the code in
46 Catalyst::Manual::Tutorial::01_Intro.
47 Please take a look at "STARTING WITH THE TUTORIAL VIRTUAL MACHINE" in
49 Catalyst::Manual::Tutorial::01_Intro before doing the rest of this
50 tutorial. Although the tutorial should work correctly under most any
51 recent version of Perl running on any operating system, the tutorial
52 has been written using the virtual machine that is available for
53 download. The entire tutorial has been tested to be sure it runs
54 correctly in this environment, so it is the most trouble-free way to
55 get started with Catalyst.
56
58 The remainder of the tutorial will build an application called "MyApp".
59 First use the Catalyst "catalyst.pl" script to initialize the framework
60 for the "MyApp" application (make sure you aren't still inside the
61 directory of the "Hello" application from the previous chapter of the
62 tutorial or in a directory that already has a "MyApp" subdirectory):
63 $ catalyst.pl MyApp
65 created "MyApp"
66 created "MyApp/script"
67 created "MyApp/lib"
68 created "MyApp/root"
69 ...
70 created "MyApp/script/myapp_create.pl"
71 Change to application directory and Run "perl Makefile.PL" to make sure your install is complete
72 And change the "MyApp" directory the helper created:
74 $ cd MyApp
76 This creates a similar skeletal structure to what we saw in Chapter 2
78 of the tutorial, except with "MyApp" and "myapp" substituted for
79 "Hello" and "hello". (As noted in Chapter 2, omit the ".pl" from the
80 command if you are using Strawberry Perl.)
81
83 One of the greatest benefits of Catalyst is that it has such a large
84 library of base classes and plugins available that you can use to
85 easily add functionality to your application. Plugins are used to
86 seamlessly integrate existing Perl modules into the overall Catalyst
87 framework. In general, they do this by adding additional methods to the
88 "context" object (generally written as $c) that Catalyst passes to
89 every component throughout the framework.
90 Take a look at the file "lib/MyApp.pm" that the helper created above.
92 By default, Catalyst enables three plugins/flags:
93 · "-Debug" Flag
95 Enables the Catalyst debug output you saw when we started the
97 "script/myapp_server.pl" development server earlier. You can
98 remove this item when you place your application into production.
99 To be technically correct, it turns out that "-Debug" is not a
101 plugin, but a flag. Although most of the items specified on the
102 "use Catalyst" line of your application class will be plugins,
103 Catalyst supports a limited number of flag options (of these,
104 "-Debug" is the most common). See the documentation for
105 <https://metacpan.org/module/Catalyst|Catalyst.pm> to get details
106 on other flags (currently "-Engine", "-Home", "-Log", and
107 "-Stats").
108 If you prefer, there are several other ways to enable debug output:
110 · the "$c->debug" method on the $c Catalyst context object
112 · the "-d" option on the "script/myapp_server.pl" script
114 · the "CATALYST_DEBUG=1" environment variable (or
116 "CATALYST_DEBUG=0" to temporarily disable debug output)
117 TIP: Depending on your needs, it can be helpful to permanently
119 remove "-Debug" from "lib/MyApp.pm" and then use the "-d" option to
120 "script/myapp_server.pl" to re-enable it when needed. We will not
121 be using that approach in the tutorial, but feel free to make use
122 of it in your own projects.
123 · Catalyst::Plugin::ConfigLoader
125 "ConfigLoader" provides an automatic way to load configurable
127 parameters for your application from a central Config::General file
128 (versus having the values hard-coded inside your Perl modules).
129 Config::General uses syntax very similar to Apache configuration
130 files. We will see how to use this feature of Catalyst during the
131 authentication and authorization sections (Chapter 5 and Chapter
132 6).
133 IMPORTANT NOTE: If you are using a version of Catalyst::Devel prior
135 to version 1.06, be aware that Catalyst changed the default format
136 from YAML to the more straightforward "Config::General" style.
137 This tutorial uses the newer "myapp.conf" file for
138 "Config::General". However, Catalyst supports both formats and will
139 automatically use either "myapp.conf" or "myapp.yml" (or any other
140 format supported by Catalyst::Plugin::ConfigLoader and
141 Config::Any). If you are using a version of Catalyst::Devel prior
142 to 1.06, you can convert to the newer format by simply creating the
143 "myapp.conf" file manually and deleting "myapp.yml". The default
144 contents of the "myapp.conf" you create should only consist of one
145 line:
146 name MyApp
148 TIP: This script can be useful for converting between configuration
150 formats:
151 perl -Ilib -e 'use MyApp; use Config::General;
153 Config::General->new->save_file("myapp.conf", MyApp->config);'
154 · Catalyst::Plugin::Static::Simple
156 "Static::Simple" provides an easy way to serve static content, such
158 as images and CSS files, from the development server.
159 For our application, we want to add one new plugin to the mix. To do
161 this, edit "lib/MyApp.pm" (this file is generally referred to as your
162 application class) and delete the lines with:
163 use Catalyst qw/
165 -Debug
166 ConfigLoader
167 Static::Simple
168 /;
169 Then replace it with:
171 # Load plugins
173 use Catalyst qw/
174 -Debug
175 ConfigLoader
176 Static::Simple
177 StackTrace
179 /;
180 Note: Recent versions of "Catalyst::Devel" have used a variety of
182 techniques to load these plugins/flags. For example, you might see the
183 following:
184 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
186 Don't let these variations confuse you -- they all accomplish the same
188 result.
189 This tells Catalyst to start using one additional plugin,
191 Catalyst::Plugin::StackTrace, to add a stack trace near the top of the
192 standard Catalyst "debug screen" (the screen Catalyst sends to your
193 browser when an error occurs). Be aware that StackTrace output appears
194 in your browser, not in the console window from which you're running
195 your application, which is where logging output usually goes.
196 Make sure when adding new plugins you also include them as a new
198 dependency within the Makefile.PL file. For example, after adding the
199 StackTrace plugin the Makefile.PL should include the following line:
200 requires 'Catalyst::Plugin::StackTrace';
202 Notes:
204 · "__PACKAGE__" is just a shorthand way of referencing the name of
206 the package where it is used. Therefore, in "MyApp.pm",
207 "__PACKAGE__" is equivalent to "MyApp".
208 · You will want to disable StackTrace before you put your application
210 into production, but it can be helpful during development.
211 · When specifying plugins, you can omit "Catalyst::Plugin::" from the
213 name. Additionally, you can spread the plugin names across
214 multiple lines as shown here or place them all on one line.
215 · If you want to see what the StackTrace error screen looks like,
217 edit "lib/MyApp/Controller/Root.pm" and put a "die "Oops";" command
218 in the "sub index :Path :Args(0)" method. Then start the
219 development server and open "http://localhost:3000/" in your
220 browser. You should get a screen that starts with "Caught
221 exception in MyApp::Controller::Root->index" with sections showing
222 a stacktrace, information about the Request and Response objects,
223 the stash (something we will learn about soon), and the
224 applications configuration. Just don't forget to remove the die
225 before you continue the tutorial! :-)
226
228 As discussed earlier, controllers are where you write methods that
229 interact with user input. Typically, controller methods respond to
230 "GET" and "POST" requests from the user's web browser.
231 Use the Catalyst "create" script to add a controller for book-related
233 actions:
234 $ script/myapp_create.pl controller Books
236 exists "/home/catalyst/MyApp/script/../lib/MyApp/Controller"
237 exists "/home/catalyst/MyApp/script/../t"
238 created "/home/catalyst/MyApp/script/../lib/MyApp/Controller/Books.pm"
239 created "/home/catalyst/MyApp/script/../t/controller_Books.t"
240 Then edit "lib/MyApp/Controller/Books.pm" (as discussed in Chapter 2 of
242 the Tutorial, Catalyst has a separate directory under "lib/MyApp" for
243 each of the three parts of MVC: "Model", "View" and "Controller") and
244 add the following method to the controller:
245 =head2 list
247 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
249 =cut
251 sub list :Local {
253 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
254 # 'Context' that's used to 'glue together' the various components
255 # that make up the application
256 my ($self, $c) = @_;
257 # Retrieve all of the book records as book model objects and store in the
259 # stash where they can be accessed by the TT template
260 # $c->stash(books => [$c->model('DB::Book')->all]);
261 # But, for now, use this code until we create the model later
262 $c->stash(books => '');
263 # Set the TT template to use. You will almost always want to do this
265 # in your action methods (action methods respond to user input in
266 # your controllers).
267 $c->stash(template => 'books/list.tt2');
268 }
269 TIP: See Appendix 1 for tips on removing the leading spaces when
271 cutting and pasting example code from POD-based documents.
272 Programmers experienced with object-oriented Perl should recognize
274 $self as a reference to the object where this method was called. On
275 the other hand, $c will be new to many Perl programmers who have not
276 used Catalyst before. This is the "Catalyst Context object", and it is
277 automatically passed as the second argument to all Catalyst action
278 methods. It is used to pass information between components and provide
279 access to Catalyst and plugin functionality.
280 Catalyst Controller actions are regular Perl methods, but they make use
282 of attributes (the "":Local"" next to the ""sub list"" in the code
283 above) to provide additional information to the Catalyst dispatcher
284 logic (note that there can be an optional space between the colon and
285 the attribute name; you will see attributes written both ways). Most
286 Catalyst Controllers use one of five action types:
287 · :Private -- Use ":Private" for methods that you want to make into
289 an action, but you do not want Catalyst to directly expose the
290 method to your users. Catalyst will not map ":Private" methods to
291 a URI. Use them for various sorts of "special" methods (the
292 "begin", "auto", etc. discussed below) or for methods you want to
293 be able to "forward" or "detach" to. (If the method is a "plain
294 old method" that you don't want to be an action at all, then just
295 define the method without any attribute -- you can call it in your
296 code, but the Catalyst dispatcher will ignore it. You will also
297 have to manually include $c if you want access to the context
298 object in the method vs. having Catalyst automatically include $c
299 in the argument list for you if it's a full-fledged action.)
300 There are five types of "special" built-in ":Private" actions:
302 "begin", "end", "default", "index", and "auto".
303 · With "begin", "end", "default", "index" private actions, only
305 the most specific action of each type will be called. For
306 example, if you define a "begin" action in your controller it
307 will override a "begin" action in your application/root
308 controller -- only the action in your controller will be
309 called.
310 · Unlike the other actions where only a single method is called
312 for each request, every auto action along the chain of
313 namespaces will be called. Each "auto" action will be called
314 from the application/root controller down through the most
315 specific class.
316 · :Path -- ":Path" actions let you map a method to an explicit URI
318 path. For example, "":Path('list')"" in
319 "lib/MyApp/Controller/Books.pm" would match on the URL
320 "http://localhost:3000/books/list", but "":Path('/list')"" would
321 match on "http://localhost:3000/list" (because of the leading
322 slash). You can use ":Args()" to specify how many arguments an
323 action should accept. See "Action-types" in
324 Catalyst::Manual::Intro for more information and examples.
325 · :Local -- ":Local" is merely a shorthand for
327 "":Path('_name_of_method_')"". For example, these are equivalent:
328 ""sub create_book :Local {...}"" and ""sub create_book
329 :Path('create_book') {...}"".
330 · :Global -- ":Global" is merely a shorthand for
332 "":Path('/_name_of_method_')"". For example, these are equivalent:
333 ""sub create_book :Global {...}"" and ""sub create_book
334 :Path('/create_book') {...}"".
335 · :Chained -- Newer Catalyst applications tend to use the Chained
337 dispatch form of action types because of its power and flexibility.
338 It allows a series of controller methods to be automatically
339 dispatched when servicing a single user request. See
340 Catalyst::Manual::Tutorial::04_BasicCRUD and
341 Catalyst::DispatchType::Chained for more information on chained
342 actions.
343 You should refer to "Action-types" in Catalyst::Manual::Intro for
345 additional information and for coverage of some lesser-used action
346 types not discussed here ("Regex" and "LocalRegex").
347
349 As mentioned in Chapter 2 of the tutorial, views are where you render
350 output, typically for display in the user's web browser (but can
351 generate other types of output such as PDF or JSON). The code in
352 "lib/MyApp/View" selects the type of view to use, with the actual
353 rendering template found in the "root" directory. As with virtually
354 every aspect of Catalyst, options abound when it comes to the specific
355 view technology you adopt inside your application. However, most
356 Catalyst applications use the Template Toolkit, known as TT (for more
357 information on TT, see <http://www.template-toolkit.org>). Other
358 somewhat popular view technologies include Mason
359 (<http://www.masonhq.com> and <http://www.masonbook.com>) and
360 HTML::Template (<http://html-template.sourceforge.net>).
361 Create a Catalyst View
363 When using TT for the Catalyst view, the main helper script is
364 Catalyst::Helper::View::TT. You may also come across references to
365 Catalyst::Helper::View::TTSite, but its use is now deprecated.
366 For our book application, enter the following command to enable the
368 "TT" style of view rendering:
369 $ script/myapp_create.pl view HTML TT
371 exists "/home/catalyst/MyApp/script/../lib/MyApp/View"
372 exists "/home/catalyst/MyApp/script/../t"
373 created "/home/catalyst/MyApp/script/../lib/MyApp/View/HTML.pm"
374 created "/home/catalyst/MyApp/script/../t/view_HTML.t"
375 This creates a view called "HTML" (the first argument) in a file called
377 "HTML.pm" that uses Catalyst::View::TT (the second argument) as the
378 "rendering engine".
379 It is now up to you to decide how you want to structure your view
381 layout. For the tutorial, we will start with a very simple TT template
382 to initially demonstrate the concepts, but quickly migrate to a more
383 typical "wrapper page" type of configuration (where the "wrapper"
384 controls the overall "look and feel" of your site from a single file or
385 set of files).
386 Edit "lib/MyApp/View/HTML.pm" and you should see something similar to
388 the following:
389 __PACKAGE__->config(
391 TEMPLATE_EXTENSION => '.tt',
392 render_die => 1,
393 );
394 And update it to match:
396 __PACKAGE__->config(
398 # Change default TT extension
399 TEMPLATE_EXTENSION => '.tt2',
400 render_die => 1,
401 );
402 This changes the default extension for Template Toolkit from '.tt' to
404 '.tt2'.
405 You can also configure components in your application class. For
407 example, Edit "lib/MyApp.pm" and you should see the default
408 configuration above the call to "_PACKAGE__->setup" (your defaults
409 could be different depending on the version of Catalyst you are using):
410 __PACKAGE__->config(
412 name => 'MyApp',
413 # Disable deprecated behavior needed by old applications
414 disable_component_resolution_regex_fallback => 1,
415 );
416 Change this to match the following (insert a new "__PACKAGE__->config"
418 below the existing statement):
419 __PACKAGE__->config(
421 name => 'MyApp',
422 # Disable deprecated behavior needed by old applications
423 disable_component_resolution_regex_fallback => 1,
424 );
425 __PACKAGE__->config(
426 # Configure the view
427 'View::HTML' => {
428 #Set the location for TT files
429 INCLUDE_PATH => [
430 __PACKAGE__->path_to( 'root', 'src' ),
431 ],
432 },
433 );
434 This changes the base directory for your template files from "root" to
436 "root/src".
437 Please stick with the settings above for the duration of the tutorial,
439 but feel free to use whatever options you desire in your applications
440 (as with most things in Perl, there's more than one way to do it...).
441 Note: We will use "root/src" as the base directory for our template
443 files, with a full naming convention of
444 "root/src/_controller_name_/_action_name_.tt2". Another popular option
445 is to use "root/" as the base (with a full filename pattern of
446 "root/_controller_name_/_action_name_.tt2").
447 Create a TT Template Page
449 First create a directory for book-related TT templates:
450 $ mkdir -p root/src/books
452 Then create "root/src/books/list.tt2" in your editor and enter:
454 [% # This is a TT comment. -%]
456 [%- # Provide a title -%]
458 [% META title = 'Book List' -%]
459 [% # Note That the '-' at the beginning or end of TT code -%]
461 [% # "chomps" the whitespace/newline at that end of the -%]
462 [% # output (use View Source in browser to see the effect) -%]
463 [% # Some basic HTML with a loop to display books -%]
465 <table>
466 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
467 [% # Display each book in a table row %]
468 [% FOREACH book IN books -%]
469 <tr>
470 <td>[% book.title %]</td>
471 <td>[% book.rating %]</td>
472 <td></td>
473 </tr>
474 [% END -%]
475 </table>
476 As indicated by the inline comments above, the "META title" line uses
478 TT's META feature to provide a title to the "wrapper" that we will
479 create later (and essentially does nothing at the moment). Meanwhile,
480 the "FOREACH" loop iterates through each "book" model object and prints
481 the "title" and "rating" fields.
482 The "[%" and "%]" tags are used to delimit Template Toolkit code. TT
484 supports a wide variety of directives for "calling" other files,
485 looping, conditional logic, etc. In general, TT simplifies the usual
486 range of Perl operators down to the single dot (".") operator. This
487 applies to operations as diverse as method calls, hash lookups, and
488 list index values (see Template::Manual::Variables for details and
489 examples). In addition to the usual Template::Toolkit module Pod
490 documentation, you can access the TT manual at
491 <https://metacpan.org/module/Template::Manual>.
492 TIP: While you can build all sorts of complex logic into your TT
494 templates, you should in general keep the "code" part of your templates
495 as simple as possible. If you need more complex logic, create helper
496 methods in your model that abstract out a set of code into a single
497 call from your TT template. (Note that the same is true of your
498 controller logic as well -- complex sections of code in your
499 controllers should often be pulled out and placed into your model
500 objects.) In Chapter 4 of the tutorial we will explore some extremely
501 helpful and powerful features of DBIx::Class that allow you to pull
502 code out of your views and controllers and place it where it rightfully
503 belongs in a model class.
504 Test Run The Application
506 To test your work so far, first start the development server:
507 $ script/myapp_server.pl -r
509 Then point your browser to <http://localhost:3000> and you should still
511 get the Catalyst welcome page. Next, change the URL in your browser to
512 <http://localhost:3000/books/list>. If you have everything working so
513 far, you should see a web page that displays nothing other than our
514 column headers for "Title", "Rating", and "Author(s)" -- we will not
515 see any books until we get the database and model working below.
516 If you run into problems getting your application to run correctly, it
518 might be helpful to refer to some of the debugging techniques covered
519 in the Debugging chapter of the tutorial.
520
522 In this step, we make a text file with the required SQL commands to
523 create a database table and load some sample data. We will use SQLite
524 (<http://www.sqlite.org>), a popular database that is lightweight and
525 easy to use. Be sure to get at least version 3. Open "myapp01.sql" in
526 your editor and enter:
527 --
529 -- Create a very simple database to hold book and author information
530 --
531 PRAGMA foreign_keys = ON;
532 CREATE TABLE book (
533 id INTEGER PRIMARY KEY,
534 title TEXT ,
535 rating INTEGER
536 );
537 -- 'book_author' is a many-to-many join table between books & authors
538 CREATE TABLE book_author (
539 book_id INTEGER REFERENCES book(id) ON DELETE CASCADE ON UPDATE CASCADE,
540 author_id INTEGER REFERENCES author(id) ON DELETE CASCADE ON UPDATE CASCADE,
541 PRIMARY KEY (book_id, author_id)
542 );
543 CREATE TABLE author (
544 id INTEGER PRIMARY KEY,
545 first_name TEXT,
546 last_name TEXT
547 );
548 ---
549 --- Load some sample data
550 ---
551 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
552 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
553 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
554 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
555 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
556 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
557 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
558 INSERT INTO author VALUES (3, 'Christian', 'Degu');
559 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
560 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
561 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
562 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
563 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
564 INSERT INTO book_author VALUES (1, 1);
565 INSERT INTO book_author VALUES (1, 2);
566 INSERT INTO book_author VALUES (1, 3);
567 INSERT INTO book_author VALUES (2, 4);
568 INSERT INTO book_author VALUES (3, 5);
569 INSERT INTO book_author VALUES (4, 6);
570 INSERT INTO book_author VALUES (4, 7);
571 INSERT INTO book_author VALUES (5, 8);
572 Then use the following command to build a "myapp.db" SQLite database:
574 $ sqlite3 myapp.db < myapp01.sql
576 If you need to create the database more than once, you probably want to
578 issue the "rm myapp.db" command to delete the database before you use
579 the "sqlite3 myapp.db < myapp01.sql" command.
580 Once the "myapp.db" database file has been created and initialized, you
582 can use the SQLite command line environment to do a quick dump of the
583 database contents:
584 $ sqlite3 myapp.db
586 SQLite version 3.7.3
587 Enter ".help" for instructions
588 Enter SQL statements terminated with a ";"
589 sqlite> select * from book;
590 1|CCSP SNRS Exam Certification Guide|5
591 2|TCP/IP Illustrated, Volume 1|5
592 3|Internetworking with TCP/IP Vol.1|4
593 4|Perl Cookbook|5
594 5|Designing with Web Standards|5
595 sqlite> .q
596 $
597 Or:
599 $ sqlite3 myapp.db "select * from book"
601 1|CCSP SNRS Exam Certification Guide|5
602 2|TCP/IP Illustrated, Volume 1|5
603 3|Internetworking with TCP/IP Vol.1|4
604 4|Perl Cookbook|5
605 5|Designing with Web Standards|5
606 As with most other SQL tools, if you are using the full "interactive"
608 environment you need to terminate your SQL commands with a ";" (it's
609 not required if you do a single SQL statement on the command line).
610 Use ".q" to exit from SQLite from the SQLite interactive mode and
611 return to your OS command prompt.
612 Please note that here we have chosen to use 'singular' table names.
614 This is because the default inflection code for older versions of
615 DBIx::Class::Schema::Loader does NOT handle plurals. There has been
616 much philosophical discussion on whether table names should be plural
617 or singular. There is no one correct answer, as long as one makes a
618 choice and remains consistent with it. If you prefer plural table names
619 (e.g. you think that they are easier to read) then see the
620 documentation in "naming" in DBIx::Class::Schema::Loader::Base (version
621 0.05 or greater).
622 For using other databases, such as PostgreSQL or MySQL, see Appendix 2.
624
626 Catalyst can be used with virtually any form of datastore available via
627 Perl. For example, Catalyst::Model::DBI can be used to access
628 databases through the traditional Perl DBI interface or you can use a
629 model to access files of any type on the filesystem. However, most
630 Catalyst applications use some form of object-relational mapping (ORM)
631 technology to create objects associated with tables in a relational
632 database, and Matt Trout's DBIx::Class (abbreviated as "DBIC") is the
633 usual choice (this tutorial will use DBIx::Class).
634 Although DBIx::Class has included support for a "create=dynamic" mode
636 to automatically read the database structure every time the application
637 starts, its use is no longer recommended. While it can make for
638 "flashy" demos, the use of the "create=static" mode we use below can be
639 implemented just as quickly and provides many advantages (such as the
640 ability to add your own methods to the overall DBIC framework, a
641 technique that we see in Chapter 4).
642 Create Static DBIx::Class Schema Files
644 Note: If you are not following along in the Tutorial Virtual Machine,
645 please be sure that you have version 1.27 or higher of DBD::SQLite and
646 version 0.39 or higher of Catalyst::Model::DBIC::Schema. (The Tutorial
647 VM already has versions that are known to work.) You can get your
648 currently installed version numbers with the following commands.
649 $ perl -MCatalyst::Model::DBIC::Schema\ 999
651 $ perl -MDBD::SQLite\ 999
652 Before you continue, make sure your "myapp.db" database file is in the
654 application's topmost directory. Now use the model helper with the
655 "create=static" option to read the database with
656 DBIx::Class::Schema::Loader and automatically build the required files
657 for us:
658 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
660 create=static dbi:SQLite:myapp.db \
661 on_connect_do="PRAGMA foreign_keys = ON"
662 exists "/home/catalyst/MyApp/script/../lib/MyApp/Model"
663 exists "/home/catalyst/MyApp/script/../t"
664 Dumping manual schema for MyApp::Schema to directory /home/catalyst/MyApp/script/../lib ...
665 Schema dump completed.
666 created "/home/catalyst/MyApp/script/../lib/MyApp/Model/DB.pm"
667 created "/home/catalyst/MyApp/script/../t/model_DB.t"
668 Please note the '\' above. Depending on your environment, you might be
670 able to cut and paste the text as shown or need to remove the '\'
671 character to that the command is all on a single line.
672 The "script/myapp_create.pl" command breaks down like this:
674 · "DB" is the name of the model class to be created by the helper in
676 the "lib/MyApp/Model" directory.
677 · "DBIC::Schema" is the type of the model to create. This equates to
679 Catalyst::Model::DBIC::Schema, the standard way to use a DBIC-based
680 model inside of Catalyst.
681 · "MyApp::Schema" is the name of the DBIC schema file written to
683 "lib/MyApp/Schema.pm".
684 · "create=static" causes DBIx::Class::Schema::Loader to load the
686 schema as it runs and then write that information out into
687 "lib/MyApp/Schema.pm" and files under the "lib/MyApp/Schema"
688 directory.
689 · "dbi:SQLite:myapp.db" is the standard DBI connect string for use
691 with SQLite.
692 · And finally, the "on_connect_do" string requests that
694 DBIx::Class::Schema::Loader create foreign key relationships for us
695 (this is not needed for databases such as PostgreSQL and MySQL, but
696 is required for SQLite). If you take a look at
697 "lib/MyApp/Model/DB.pm", you will see that the SQLite pragma is
698 propagated to the Model, so that SQLite's recent (and optional)
699 foreign key enforcement is enabled at the start of every database
700 connection.
701 If you look in the "lib/MyApp/Schema.pm" file, you will find that it
703 only contains a call to the "load_namespaces" method. You will also
704 find that "lib/MyApp" contains a "Schema" subdirectory, which then has
705 a subdirectory called "Result". This "Result" subdirectory then has
706 files named according to each of the tables in our simple database
707 ("Author.pm", "BookAuthor.pm", and "Book.pm"). These three files are
708 called "Result Classes" (or "ResultSource Classes") in DBIx::Class
709 nomenclature. Although the Result Class files are named after tables in
710 our database, the classes correspond to the row-level data that is
711 returned by DBIC (more on this later, especially in "EXPLORING THE
712 POWER OF DBIC" in Catalyst::Manual::Tutorial::04_BasicCRUD).
713 The idea with the Result Source files created under
715 "lib/MyApp/Schema/Result" by the "create=static" option is to only edit
716 the files below the "# DO NOT MODIFY THIS OR ANYTHING ABOVE!" warning.
717 If you place all of your changes below that point in the file, you can
718 regenerate the automatically created information at the top of each
719 file should your database structure get updated.
720 Also note the "flow" of the model information across the various files
722 and directories. Catalyst will initially load the model from
723 "lib/MyApp/Model/DB.pm". This file contains a reference to
724 "lib/MyApp/Schema.pm", so that file is loaded next. Finally, the call
725 to "load_namespaces" in "Schema.pm" will load each of the "Result
726 Class" files from the "lib/MyApp/Schema/Result" subdirectory. The
727 final outcome is that Catalyst will dynamically create three table-
728 specific Catalyst models every time the application starts (you can see
729 these three model files listed in the debug output generated when you
730 launch the application).
731 Additionally, the "lib/MyApp/Schema.pm" model can easily be loaded
733 outside of Catalyst, for example, in command-line utilities and/or cron
734 jobs. "lib/MyApp/Model/DB.pm" provides a very thin "bridge" between
735 Catalyst and this external database model. Once you see how we can add
736 some powerful features to our DBIC model in Chapter 4, the elegance of
737 this approach will start to become more obvious.
738 NOTE: Older versions of Catalyst::Model::DBIC::Schema use the
740 deprecated DBIx::Class "load_classes" technique instead of the newer
741 "load_namespaces". For new applications, please try to use
742 "load_namespaces" since it more easily supports a very useful DBIC
743 technique called "ResultSet Classes." If you need to convert an
744 existing application from "load_classes" to "load_namespaces," you can
745 use this process to automate the migration, but first make sure you
746 have version 0.39 of Catalyst::Model::DBIC::Schema and
747 DBIx::Class::Schema::Loader version 0.05000 or later.
748 $ # Re-run the helper to upgrade for you
750 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
751 create=static naming=current use_namespaces=1 \
752 dbi:SQLite:myapp.db \
753 on_connect_do="PRAGMA foreign_keys = ON"
754
756 Open "lib/MyApp/Controller/Books.pm" and un-comment the model code we
757 left disabled earlier so that your version matches the following (un-
758 comment the line containing "[$c->model('DB::Book')->all]" and delete
759 the next 2 lines):
760 =head2 list
762 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
764 =cut
766 sub list :Local {
768 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
769 # 'Context' that's used to 'glue together' the various components
770 # that make up the application
771 my ($self, $c) = @_;
772 # Retrieve all of the book records as book model objects and store
774 # in the stash where they can be accessed by the TT template
775 $c->stash(books => [$c->model('DB::Book')->all]);
776 # Set the TT template to use. You will almost always want to do this
778 # in your action methods (action methods respond to user input in
779 # your controllers).
780 $c->stash(template => 'books/list.tt2');
781 }
782 TIP: You may see the "$c->model('DB::Book')" un-commented above written
784 as "$c->model('DB')->resultset('Book')". The two are equivalent.
785 Either way, "$c->model" returns a DBIx::Class::ResultSet which handles
786 queries against the database and iterating over the set of results that
787 is returned.
788 We are using the "->all" to fetch all of the books. DBIC supports a
790 wide variety of more advanced operations to easily do things like
791 filtering and sorting the results. For example, the following could be
792 used to sort the results by descending title:
793 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
795 Some other examples are provided in "Complex WHERE clauses" in
797 DBIx::Class::Manual::Cookbook, with additional information found at
798 "search" in DBIx::Class::ResultSet, "Searching" in
799 DBIx::Class::Manual::FAQ, DBIx::Class::Manual::Intro and
800 Catalyst::Model::DBIC::Schema.
801 Test Run The Application
803 First, let's enable an environment variable that causes DBIx::Class to
804 dump the SQL statements used to access the database. This is a helpful
805 trick when you are trying to debug your database-oriented code. Press
806 "Ctrl-C" to break out of the development server and enter:
807 $ export DBIC_TRACE=1
809 $ script/myapp_server.pl -r
810 This assumes you are using bash as your shell -- adjust accordingly if
812 you are using a different shell (for example, under tcsh, use "setenv
813 DBIC_TRACE 1").
814 NOTE: You can also set this in your code using
816 "$class->storage->debug(1);". See DBIx::Class::Manual::Troubleshooting
817 for details (including options to log to a file instead of displaying
818 to the Catalyst development server log).
819 Then launch the Catalyst development server. The log output should
821 display something like:
822 $ script/myapp_server.pl -r
824 [debug] Debug messages enabled
825 [debug] Statistics enabled
826 [debug] Loaded plugins:
827 .----------------------------------------------------------------------------.
828 | Catalyst::Plugin::ConfigLoader 0.30 |
829 | Catalyst::Plugin::StackTrace 0.11 |
830 '----------------------------------------------------------------------------'
831 [debug] Loaded dispatcher "Catalyst::Dispatcher"
833 [debug] Loaded engine "Catalyst::Engine"
834 [debug] Found home "/home/catalyst/MyApp"
835 [debug] Loaded Config "/home/catalyst/MyApp/myapp.conf"
836 [debug] Loaded components:
837 .-----------------------------------------------------------------+----------.
838 | Class | Type |
839 +-----------------------------------------------------------------+----------+
840 | MyApp::Controller::Books | instance |
841 | MyApp::Controller::Root | instance |
842 | MyApp::Model::DB | instance |
843 | MyApp::Model::DB::Author | class |
844 | MyApp::Model::DB::Book | class |
845 | MyApp::Model::DB::BookAuthor | class |
846 | MyApp::View::HTML | instance |
847 '-----------------------------------------------------------------+----------'
848 [debug] Loaded Private actions:
850 .----------------------+--------------------------------------+--------------.
851 | Private | Class | Method |
852 +----------------------+--------------------------------------+--------------+
853 | /default | MyApp::Controller::Root | default |
854 | /end | MyApp::Controller::Root | end |
855 | /index | MyApp::Controller::Root | index |
856 | /books/index | MyApp::Controller::Books | index |
857 | /books/list | MyApp::Controller::Books | list |
858 '----------------------+--------------------------------------+--------------'
859 [debug] Loaded Path actions:
861 .-------------------------------------+--------------------------------------.
862 | Path | Private |
863 +-------------------------------------+--------------------------------------+
864 | / | /default |
865 | / | /index |
866 | /books | /books/index |
867 | /books/list | /books/list |
868 '-------------------------------------+--------------------------------------'
869 [info] MyApp powered by Catalyst 5.80020
871 HTTP::Server::PSGI: Accepting connections at http://0:3000
872 NOTE: Be sure you run the "script/myapp_server.pl" command from the
874 'base' directory of your application, not inside the "script" directory
875 itself or it will not be able to locate the "myapp.db" database file.
876 You can use a fully qualified or a relative path to locate the database
877 file, but we did not specify that when we ran the model helper earlier.
878 Some things you should note in the output above:
880 · Catalyst::Model::DBIC::Schema dynamically created three model
882 classes, one to represent each of the three tables in our database
883 ("MyApp::Model::DB::Author", "MyApp::Model::DB::BookAuthor", and
884 "MyApp::Model::DB::Book").
885 · The "list" action in our Books controller showed up with a path of
887 "/books/list".
888 Point your browser to <http://localhost:3000> and you should still get
890 the Catalyst welcome page.
891 Next, to view the book list, change the URL in your browser to
893 <http://localhost:3000/books/list>. You should get a list of the five
894 books loaded by the "myapp01.sql" script above without any formatting.
895 The rating for each book should appear on each row, but the "Author(s)"
896 column will still be blank (we will fill that in later).
897 Also notice in the output of the "script/myapp_server.pl" that
899 DBIx::Class used the following SQL to retrieve the data:
900 SELECT me.id, me.title, me.rating FROM book me
902 because we enabled DBIC_TRACE.
904 You now have the beginnings of a simple but workable web application.
906 Continue on to future sections and we will develop the application more
907 fully.
908
910 When using TT, you can (and should) create a wrapper that will
911 literally wrap content around each of your templates. This is
912 certainly useful as you have one main source for changing things that
913 will appear across your entire site/application instead of having to
914 edit many individual files.
915 Configure HTML.pm For The Wrapper
917 In order to create a wrapper, you must first edit your TT view and tell
918 it where to find your wrapper file.
919 Edit your TT view in "lib/MyApp/View/HTML.pm" and change it to match
921 the following:
922 __PACKAGE__->config(
924 # Change default TT extension
925 TEMPLATE_EXTENSION => '.tt2',
926 # Set the location for TT files
927 INCLUDE_PATH => [
928 MyApp->path_to( 'root', 'src' ),
929 ],
930 # Set to 1 for detailed timer stats in your HTML as comments
931 TIMER => 0,
932 # This is your wrapper template located in the 'root/src'
933 WRAPPER => 'wrapper.tt2',
934 );
935 Create the Wrapper Template File and Stylesheet
937 Next you need to set up your wrapper template. Basically, you'll want
938 to take the overall layout of your site and put it into this file. For
939 the tutorial, open "root/src/wrapper.tt2" and input the following:
940 <?xml version="1.0" encoding="UTF-8"?>
942 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" [%#
943 %]"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
944 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
945 <head>
946 <title>[% template.title or "My Catalyst App!" %]</title>
947 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
948 </head>
949 <body>
951 <div id="outer">
952 <div id="header">
953 [%# Your logo could go here -%]
954 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
955 [%# Insert the page title -%]
956 <h1>[% template.title or site.title %]</h1>
957 </div>
958 <div id="bodyblock">
960 <div id="menu">
961 Navigation:
962 <ul>
963 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
964 <li><a href="[% c.uri_for('/')
965 %]" title="Catalyst Welcome Page">Welcome</a></li>
966 </ul>
967 </div><!-- end menu -->
968 <div id="content">
970 [%# Status and error messages %]
971 <span class="message">[% status_msg %]</span>
972 <span class="error">[% error_msg %]</span>
973 [%# This is where TT will stick all of your template's contents. -%]
974 [% content %]
975 </div><!-- end content -->
976 </div><!-- end bodyblock -->
977 <div id="footer">Copyright (c) your name goes here</div>
979 </div><!-- end outer -->
980 </body>
982 </html>
983 Notice the status and error message sections in the code above:
985 <span class="status">[% status_msg %]</span>
987 <span class="error">[% error_msg %]</span>
988 If we set either message in the Catalyst stash (e.g.,
990 "$c->stash->{status_msg} = 'Request was successful!'") it will be
991 displayed whenever any view used by that request is rendered. The
992 "message" and "error" CSS styles can be customized to suit your needs
993 in the "root/static/css/main.css" file we create below.
994 Notes:
996 · The Catalyst stash only lasts for a single HTTP request. If you
998 need to retain information across requests you can use
999 Catalyst::Plugin::Session (we will use Catalyst sessions in the
1000 Authentication chapter of the tutorial).
1001 · Although it is beyond the scope of this tutorial, you may wish to
1003 use a JavaScript or AJAX tool such as jQuery
1004 (<http://www.jquery.com>) or Dojo (<http://www.dojotoolkit.org>).
1005 Create A Basic Stylesheet
1007 First create a central location for stylesheets under the static
1009 directory:
1010 $ mkdir root/static/css
1012 Then open the file "root/static/css/main.css" (the file referenced in
1014 the stylesheet href link of our wrapper above) and add the following
1015 content:
1016 #header {
1018 text-align: center;
1019 }
1020 #header h1 {
1021 margin: 0;
1022 }
1023 #header img {
1024 float: right;
1025 }
1026 #footer {
1027 text-align: center;
1028 font-style: italic;
1029 padding-top: 20px;
1030 }
1031 #menu {
1032 font-weight: bold;
1033 background-color: #ddd;
1034 }
1035 #menu ul {
1036 list-style: none;
1037 float: left;
1038 margin: 0;
1039 padding: 0 0 50% 5px;
1040 font-weight: normal;
1041 background-color: #ddd;
1042 width: 100px;
1043 }
1044 #content {
1045 margin-left: 120px;
1046 }
1047 .message {
1048 color: #390;
1049 }
1050 .error {
1051 color: #f00;
1052 }
1053 You may wish to check out a "CSS Framework" like Emastic
1055 (<http://code.google.com/p/emastic/>) as a way to quickly provide lots
1056 of high-quality CSS functionality.
1057 Test Run The Application
1059 Hit "Reload" in your web browser and you should now see a formatted
1060 version of our basic book list. (Again, the development server should
1061 have automatically restarted when you made changes to
1062 "lib/MyApp/View/HTML.pm". If you are not using the "-r" option, you
1063 will need to hit "Ctrl-C" and manually restart it. Also note that the
1064 development server does NOT need to restart for changes to the TT and
1065 static files we created and edited in the "root" directory -- those
1066 updates are handled on a per-request basis.)
1067 Although our wrapper and stylesheet are obviously very simple, you
1069 should see how it allows us to control the overall look of an entire
1070 website from two central files. To add new pages to the site, just
1071 provide a template that fills in the "content" section of our wrapper
1072 template -- the wrapper will provide the overall feel of the page.
1073 Updating the Generated DBIx::Class Result Class Files
1075 If you take a look at the Schema files automatically generated by
1076 DBIx::Class::Schema::Loader, you will see that it has already defined
1077 "has_many" and "belongs_to" relationships on each side of our foreign
1078 keys. For example, take a look at "lib/MyApp/Schema/Result/Book.pm" and
1079 notice the following code:
1080 =head1 RELATIONS
1082 =head2 book_authors
1084 Type: has_many
1086 Related object: L<MyApp::Schema::Result::BookAuthor>
1088 =cut
1090 __PACKAGE__->has_many(
1092 "book_authors",
1093 "MyApp::Schema::Result::BookAuthor",
1094 { "foreign.book_id" => "self.id" },
1095 { cascade_copy => 0, cascade_delete => 0 },
1096 );
1097 Each "Book" "has_many" "book_authors", where "BookAuthor" is the many-
1099 to-many table that allows each Book to have multiple Authors, and each
1100 Author to have multiple books. The arguments to "has_many" are:
1101 · "book_authors" - The name for this relationship. DBIC will create
1103 an accessor on the "Books" DBIC Row object with this name.
1104 · "MyApp::Schema::Result::BookAuthor" - The name of the DBIC model
1106 class referenced by this "has_many" relationship.
1107 · "foreign.book_id" - "book_id" is the name of the foreign key column
1109 in the foreign table that points back to this table.
1110 · "self.id" - "id" is the name of the column in this table that is
1112 referenced by the foreign key.
1113 See "has_many" in DBIx::Class::Relationship for additional information.
1115 Note that you might see a "hand coded" version of the "has_many"
1116 relationship above expressed as:
1117 __PACKAGE__->has_many(
1119 "book_authors",
1120 "MyApp::Schema::Result::BookAuthor",
1121 "book_id",
1122 );
1123 Where the third argument is simply the name of the column in the
1125 foreign table. However, the hashref syntax used by
1126 DBIx::Class::Schema::Loader is more flexible (for example, it can
1127 handle "multi-column foreign keys").
1128 Note: If you are using older versions of SQLite and related DBIC tools,
1130 you will need to manually define your "has_many" and "belongs_to"
1131 relationships. We recommend upgrading to the versions specified above.
1132 :-)
1133 Have a look at "lib/MyApp/Schema/Result/BookAuthor.pm" and notice that
1135 there is a "belongs_to" relationship defined that acts as the "mirror
1136 image" to the "has_many" relationship we just looked at above:
1137 =head1 RELATIONS
1139 =head2 book
1141 Type: belongs_to
1143 Related object: L<MyApp::Schema::Result::Book>
1145 =cut
1147 __PACKAGE__->belongs_to(
1149 "book",
1150 "MyApp::Schema::Result::Book",
1151 { id => "book_id" },
1152 { join_type => "LEFT", on_delete => "CASCADE", on_update => "CASCADE" },
1153 );
1154 The arguments are similar, but see "belongs_to" in
1156 DBIx::Class::Relationship for the details.
1157 Although recent versions of SQLite and DBIx::Class::Schema::Loader
1159 automatically handle the "has_many" and "belongs_to" relationships,
1160 "many_to_many" relationship bridges (not technically a relationship)
1161 currently need to be manually inserted. To add a "many_to_many"
1162 relationship bridge, first edit "lib/MyApp/Schema/Result/Book.pm" and
1163 add the following text below the "# You can replace this text..."
1164 comment:
1165 # many_to_many():
1167 # args:
1168 # 1) Name of relationship bridge, DBIC will create accessor with this name
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
1171 # You must already have the has_many() defined to use a many_to_many().
1172 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1173 Note: Be careful to put this code above the "1;" at the end of the
1175 file. As with any Perl package, we need to end the last line with a
1176 statement that evaluates to "true". This is customarily done with "1;"
1177 on a line by itself.
1178 The "many_to_many" relationship bridge is optional, but it makes it
1180 easier to map a book to its collection of authors. Without it, we
1181 would have to "walk" through the "book_author" table as in
1182 "$book->book_author->first->author->last_name" (we will see examples on
1183 how to use DBIx::Class objects in your code soon, but note that because
1184 "$book->book_author" can return multiple authors, we have to use
1185 "first" to display a single author). "many_to_many" allows us to use
1186 the shorter "$book->author->first->last_name". Note that you cannot
1187 define a "many_to_many" relationship bridge without also having the
1188 "has_many" relationship in place.
1189 Then edit "lib/MyApp/Schema/Result/Author.pm" and add the reverse
1191 "many_to_many" relationship bridge for "Author" as follows (again, be
1192 careful to put in above the "1;" but below the "# DO NOT MODIFY THIS OR
1193 ANYTHING ABOVE!" comment):
1194 # many_to_many():
1196 # args:
1197 # 1) Name of relationship bridge, DBIC will create accessor with this name
1198 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1199 # 3) Name of belongs_to() relationship in model class of has_many() above
1200 # You must already have the has_many() defined to use a many_to_many().
1201 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
1202 Run The Application
1204 Run the Catalyst development server script with the "DBIC_TRACE" option
1205 (it might still be enabled from earlier in the tutorial, but here is an
1206 alternate way to specify the trace option just in case):
1207 $ DBIC_TRACE=1 script/myapp_server.pl -r
1209 Make sure that the application loads correctly and that you see the
1211 three dynamically created model classes (one for each of the Result
1212 Classes we created).
1213 Then hit the URL <http://localhost:3000/books/list> with your browser
1215 and be sure that the book list still displays correctly.
1216 Note: You will not see the authors yet because the view isn't taking
1218 advantage of these relationships. Read on to the next section where we
1219 update the template to do that.
1220
1222 Let's add a new column to our book list page that takes advantage of
1223 the relationship information we manually added to our schema files in
1224 the previous section. Edit "root/src/books/list.tt2" and replace the
1225 "empty" table cell "<td></td>" with the following:
1226 ...
1228 <td>
1229 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1230 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1231 [% # loop in 'side effect notation' to load just the last names of the -%]
1232 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
1233 [% # a value, so nothing will be printed here. But, if you have something -%]
1234 [% # in TT that does return a value and you don't want it printed, you -%]
1235 [% # 1) assign it to a bogus value, or -%]
1236 [% # 2) use the CALL keyword to call it and discard the return value. -%]
1237 [% tt_authors = [ ];
1238 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1239 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1240 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1241 ([% tt_authors.size | html %])
1242 [% # Use another TT vmethod to join & print the names & comma separators -%]
1243 [% tt_authors.join(', ') | html %]
1244 </td>
1245 ...
1246 IMPORTANT NOTE: Again, you should keep as much "logic code" as possible
1248 out of your views. This kind of logic belongs in your model (the same
1249 goes for controllers -- keep them as "thin" as possible and push all of
1250 the "complicated code" out to your model objects). Avoid code like you
1251 see in the previous example -- we are only using it here to show some
1252 extra features in TT until we get to the more advanced model features
1253 we will see in Chapter 4 (see "EXPLORING THE POWER OF DBIC" in
1254 Catalyst::Manual::Tutorial::04_BasicCRUD).
1255 Then hit "Reload" in your browser (note that you don't need to reload
1257 the development server or use the "-r" option when updating TT
1258 templates) and you should now see the number of authors each book has
1259 along with a comma-separated list of the authors' last names. (If you
1260 didn't leave the development server running from the previous step, you
1261 will obviously need to start it before you can refresh your browser
1262 window.)
1263 If you are still running the development server with "DBIC_TRACE"
1265 enabled, you should also now see five more "SELECT" statements in the
1266 debug output (one for each book as the authors are being retrieved by
1267 DBIx::Class):
1268 SELECT me.id, me.title, me.rating FROM book me:
1270 SELECT author.id, author.first_name, author.last_name FROM book_author me
1271 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '1'
1272 SELECT author.id, author.first_name, author.last_name FROM book_author me
1273 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '2'
1274 SELECT author.id, author.first_name, author.last_name FROM book_author me
1275 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '3'
1276 SELECT author.id, author.first_name, author.last_name FROM book_author me
1277 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '4'
1278 SELECT author.id, author.first_name, author.last_name FROM book_author me
1279 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '5'
1280 Also note in "root/src/books/list.tt2" that we are using "| html", a
1282 type of TT filter, to escape characters such as < and > to < and
1283 > and avoid various types of dangerous hacks against your
1284 application. In a real application, you would probably want to put "|
1285 html" at the end of every field where a user has control over the
1286 information that can appear in that field (and can therefore inject
1287 markup or code if you don't "neutralize" those fields). In addition to
1288 "| html", Template Toolkit has a variety of other useful filters that
1289 can be found in the documentation for Template::Filters. (While we are
1290 on the topic of security and escaping of dangerous values, one of the
1291 advantages of using tools like DBIC for database access or HTML::FormFu
1292 for form management [see Chapter 9] is that they automatically handle
1293 most escaping for you and therefore dramatically increase the security
1294 of your app.)
1295
1297 In some situations, it can be useful to run your application and
1298 display a page without using a browser. Catalyst lets you do this
1299 using the "script/myapp_test.pl" script. Just supply the URL you wish
1300 to display and it will run that request through the normal controller
1301 dispatch logic and use the appropriate view to render the output
1302 (obviously, complex pages may dump a lot of text to your terminal
1303 window). For example, if "Ctrl+C" out of the development server and
1304 then type:
1305 $ script/myapp_test.pl "/books/list"
1307 You should get the same text as if you visited
1309 <http://localhost:3000/books/list> with the normal development server
1310 and asked your browser to view the page source. You can even pipe this
1311 HTML text output to a text-based browser using a command like:
1312 $ script/myapp_test.pl "/books/list" | lynx -stdin
1314 And you should see a fully rendered text-based view of your page. (If
1316 you are following along in Debian 6, type "sudo aptitude -y install
1317 lynx" to install lynx.) If you do start lynx, you can use the "Q" key
1318 to quit.
1319
1321 NOTE: The rest of this chapter of the tutorial is optional. You can
1322 skip to Chapter 4, Basic CRUD, if you wish.
1323 Using 'RenderView' for the Default View
1325 Once your controller logic has processed the request from a user, it
1326 forwards processing to your view in order to generate the appropriate
1327 response output. Catalyst uses Catalyst::Action::RenderView by default
1328 to automatically perform this operation. If you look in
1329 "lib/MyApp/Controller/Root.pm", you should see the empty definition for
1330 the "sub end" method:
1331 sub end : ActionClass('RenderView') {}
1333 The following bullet points provide a quick overview of the
1335 "RenderView" process:
1336 · "Root.pm" is designed to hold application-wide logic.
1338 · At the end of a given user request, Catalyst will call the most
1340 specific "end" method that's appropriate. For example, if the
1341 controller for a request has an "end" method defined, it will be
1342 called. However, if the controller does not define a controller-
1343 specific "end" method, the "global" "end" method in "Root.pm" will
1344 be called.
1345 · Because the definition includes an "ActionClass" attribute, the
1347 Catalyst::Action::RenderView logic will be executed after any code
1348 inside the definition of "sub end" is run. See
1349 Catalyst::Manual::Actions for more information on "ActionClass".
1350 · Because "sub end" is empty, this effectively just runs the default
1352 logic in "RenderView". However, you can easily extend the
1353 "RenderView" logic by adding your own code inside the empty method
1354 body ("{}") created by the Catalyst Helpers when we first ran the
1355 "catalyst.pl" to initialize our application. See
1356 Catalyst::Action::RenderView for more detailed information on how
1357 to extend "RenderView" in "sub end".
1358 RenderView's "dump_info" Feature
1360 One of the nice features of "RenderView" is that it automatically
1361 allows you to add "dump_info=1" to the end of any URL for your
1362 application and it will force the display of the "exception dump"
1363 screen to the client browser. You can try this out by pointing your
1364 browser to this URL:
1365 http://localhost:3000/books/list?dump_info=1
1367 You should get a page with the following message at the top:
1369 Caught exception in MyApp::Controller::Root->end "Forced debug -
1371 Scrubbed output at /usr/share/perl5/Catalyst/Action/RenderView.pm line 46."
1372 Along with a summary of your application's state at the end of the
1374 processing for that request. The "Stash" section should show a
1375 summarized version of the DBIC book model objects. If desired, you can
1376 adjust the summarization logic (called "scrubbing" logic) -- see
1377 Catalyst::Action::RenderView for details.
1378 Note that you shouldn't need to worry about "normal clients" using this
1380 technique to "reverse engineer" your application -- "RenderView" only
1381 supports the "dump_info=1" feature when your application is running in
1382 "-Debug" mode (something you won't do once you have your application
1383 deployed in production).
1384 Using The Default Template Name
1386 By default, "Catalyst::View::TT" will look for a template that uses the
1387 same name as your controller action, allowing you to save the step of
1388 manually specifying the template name in each action. For example,
1389 this would allow us to remove the "$c->stash->{template} =
1390 'books/list.tt2';" line of our "list" action in the Books controller.
1391 Open "lib/MyApp/Controller/Books.pm" in your editor and comment out
1392 this line to match the following (only the "$c->stash->{template}" line
1393 has changed):
1394 =head2 list
1396 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1398 =cut
1400 sub list :Local {
1402 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1403 # 'Context' that's used to 'glue together' the various components
1404 # that make up the application
1405 my ($self, $c) = @_;
1406 # Retrieve all of the book records as book model objects and store in the
1408 # stash where they can be accessed by the TT template
1409 $c->stash(books => [$c->model('DB::Book')->all]);
1410 # Set the TT template to use. You will almost always want to do this
1412 # in your action methods (actions methods respond to user input in
1413 # your controllers).
1414 #$c->stash(template => 'books/list.tt2');
1415 }
1416 You should now be able to access the <http://localhost:3000/books/list>
1418 URL as before.
1419 NOTE: If you use the default template technique, you will not be able
1421 to use either the "$c->forward" or the "$c->detach" mechanisms (these
1422 are discussed in Chapter 2 and Chapter 9 of the Tutorial).
1423 IMPORTANT: Make sure that you do not skip the following section before
1425 continuing to the next chapter 4 Basic CRUD.
1426 Return To A Manually Specified Template
1428 In order to be able to use "$c->forward" and "$c->detach" later in the
1429 tutorial, you should remove the comment from the statement in "sub
1430 list" in "lib/MyApp/Controller/Books.pm":
1431 $c->stash(template => 'books/list.tt2');
1433 Then delete the "TEMPLATE_EXTENSION" line in "lib/MyApp/View/HTML.pm".
1435 Check the <http://localhost:3000/books/list> URL in your browser. It
1437 should look the same manner as with earlier sections.
1438 You can jump to the next chapter of the tutorial here: Basic CRUD
1440
1442 Kennedy Clark, "hkclark@gmail.com"
1443 Feel free to contact the author for any errors or suggestions, but the
1445 best way to report issues is via the CPAN RT Bug system at
1446 <https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
1447 Copyright 2006-2011, Kennedy Clark, under the Creative Commons
1449 Attribution Share-Alike License Version 3.0
1450 (<http://creativecommons.org/licenses/by-sa/3.0/us/>).
1451perl v5.28.0 Catalyst2:0:1M4a-n1u2a-l1:3:Tutorial::03_MoreCatalystBasics(3)