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 $c) that Catalyst passes to
89 every component throughout the framework.
90 Take a look at the file lib/MyApp.pm that the helper created above. By
92 default, Catalyst enables three plugins/flags:
93 · "-Debug" Flag
95 Enables the Catalyst debug output you saw when we started the
97 script/myapp_server.pl development server earlier. You can remove
98 this item when you place your application into production.
99 To be technically correct, it turns out that "-Debug" is not a
101 plugin, but a flag. Although most of the items specified on the
102 "use Catalyst" line of your application class will be plugins,
103 Catalyst supports a limited number of flag options (of these,
104 "-Debug" is the most common). See the documentation for
105 Catalyst.pm to get details on other flags (currently "-Engine",
106 "-Home", "-Log", and "-Stats").
107 If you prefer, there are several other ways to enable debug output:
109 · the "$c->debug" method on the $c Catalyst context object
111 · the "-d" option on the script/myapp_server.pl script
113 · the "CATALYST_DEBUG=1" environment variable (or
115 "CATALYST_DEBUG=0" to temporarily disable debug output)
116 TIP: Depending on your needs, it can be helpful to permanently
118 remove "-Debug" from "lib/MyApp.pm" and then use the "-d" option to
119 script/myapp_server.pl to re-enable it when needed. We will not be
120 using that approach in the tutorial, but feel free to make use of
121 it in your own projects.
122 · Catalyst::Plugin::ConfigLoader
124 "ConfigLoader" provides an automatic way to load configurable
126 parameters for your application from a central Config::General file
127 (versus having the values hard-coded inside your Perl modules).
128 Config::General uses syntax very similar to Apache configuration
129 files. We will see how to use this feature of Catalyst during the
130 authentication and authorization sections (Chapter 5 and Chapter
131 6).
132 IMPORTANT NOTE: If you are using a version of Catalyst::Devel prior
134 to version 1.06, be aware that Catalyst changed the default format
135 from YAML to the more straightforward Config::General style. This
136 tutorial uses the newer "myapp.conf" file for Config::General.
137 However, Catalyst supports both formats and will automatically use
138 either myapp.conf or myapp.yml (or any other format supported by
139 Catalyst::Plugin::ConfigLoader and Config::Any). If you are using
140 a version of Catalyst::Devel prior to 1.06, you can convert to the
141 newer format by simply creating the myapp.conf file manually and
142 deleting myapp.yml. The default contents of the myapp.conf you
143 create should only consist of one line:
144 name MyApp
146 TIP: This script can be useful for converting between configuration
148 formats:
149 perl -Ilib -e 'use MyApp; use Config::General;
151 Config::General->new->save_file("myapp.conf", MyApp->config);'
152 · Catalyst::Plugin::Static::Simple
154 "Static::Simple" provides an easy way to serve static content, such
156 as images and CSS files, from the development server.
157 For our application, we want to add one new plugin to the mix. To do
159 this, edit lib/MyApp.pm (this file is generally referred to as your
160 application class) and delete the lines with:
161 use Catalyst qw/
163 -Debug
164 ConfigLoader
165 Static::Simple
166 /;
167 Then replace it with:
169 # Load plugins
171 use Catalyst qw/
172 -Debug
173 ConfigLoader
174 Static::Simple
175 StackTrace
177 /;
178 Note: Recent versions of Catalyst::Devel have used a variety of
180 techniques to load these plugins/flags. For example, you might see the
181 following:
182 __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/);
184 Don't let these variations confuse you -- they all accomplish the same
186 result.
187 This tells Catalyst to start using one additional plugin,
189 Catalyst::Plugin::StackTrace, to add a stack trace near the top of the
190 standard Catalyst "debug screen" (the screen Catalyst sends to your
191 browser when an error occurs). Be aware that StackTrace output appears
192 in your browser, not in the console window from which you're running
193 your application, which is where logging output usually goes.
194 Make sure when adding new plugins you also include them as a new
196 dependency within the Makefile.PL file. For example, after adding the
197 StackTrace plugin the Makefile.PL should include the following line:
198 requires 'Catalyst::Plugin::StackTrace';
200 Notes:
202 · "__PACKAGE__" is just a shorthand way of referencing the name of
204 the package where it is used. Therefore, in MyApp.pm,
205 "__PACKAGE__" is equivalent to "MyApp".
206 · You will want to disable StackTrace before you put your application
208 into production, but it can be helpful during development.
209 · When specifying plugins, you can omit "Catalyst::Plugin::" from the
211 name. Additionally, you can spread the plugin names across
212 multiple lines as shown here or place them all on one line.
213 · If you want to see what the StackTrace error screen looks like,
215 edit lib/MyApp/Controller/Root.pm and put a "die "Oops";" command
216 in the "sub index :Path :Args(0)" method. Then start the
217 development server and open "http://localhost:3000/" in your
218 browser. You should get a screen that starts with "Caught
219 exception in MyApp::Controller::Root->index" with sections showing
220 a stacktrace, information about the Request and Response objects,
221 the stash (something we will learn about soon), and the
222 applications configuration. Just don't forget to remove the die
223 before you continue the tutorial! :-)
224
226 As discussed earlier, controllers are where you write methods that
227 interact with user input. Typically, controller methods respond to
228 "GET" and "POST" requests from the user's web browser.
229 Use the Catalyst "create" script to add a controller for book-related
231 actions:
232 $ script/myapp_create.pl controller Books
234 exists "/home/catalyst/MyApp/script/../lib/MyApp/Controller"
235 exists "/home/catalyst/MyApp/script/../t"
236 created "/home/catalyst/MyApp/script/../lib/MyApp/Controller/Books.pm"
237 created "/home/catalyst/MyApp/script/../t/controller_Books.t"
238 Then edit lib/MyApp/Controller/Books.pm (as discussed in Chapter 2 of
240 the Tutorial, Catalyst has a separate directory under lib/MyApp for
241 each of the three parts of MVC: "Model", "View" and "Controller") and
242 add the following method to the controller:
243 =head2 list
245 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
247 =cut
249 sub list :Local {
251 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
252 # 'Context' that's used to 'glue together' the various components
253 # that make up the application
254 my ($self, $c) = @_;
255 # Retrieve all of the book records as book model objects and store in the
257 # stash where they can be accessed by the TT template
258 # $c->stash(books => [$c->model('DB::Book')->all]);
259 # But, for now, use this code until we create the model later
260 $c->stash(books => '');
261 # Set the TT template to use. You will almost always want to do this
263 # in your action methods (action methods respond to user input in
264 # your controllers).
265 $c->stash(template => 'books/list.tt2');
266 }
267 TIP: See Appendix 1 for tips on removing the leading spaces when
269 cutting and pasting example code from POD-based documents.
270 Programmers experienced with object-oriented Perl should recognize
272 $self as a reference to the object where this method was called. On
273 the other hand, $c will be new to many Perl programmers who have not
274 used Catalyst before. This is the "Catalyst Context object", and it is
275 automatically passed as the second argument to all Catalyst action
276 methods. It is used to pass information between components and provide
277 access to Catalyst and plugin functionality.
278 Catalyst Controller actions are regular Perl methods, but they make use
280 of attributes (the "":Local"" next to the ""sub list"" in the code
281 above) to provide additional information to the Catalyst dispatcher
282 logic (note that there can be an optional space between the colon and
283 the attribute name; you will see attributes written both ways). Most
284 Catalyst Controllers use one of five action types:
285 · :Private -- Use ":Private" for methods that you want to make into
287 an action, but you do not want Catalyst to directly expose the
288 method to your users. Catalyst will not map ":Private" methods to
289 a URI. Use them for various sorts of "special" methods (the
290 "begin", "auto", etc. discussed below) or for methods you want to
291 be able to "forward" or "detach" to. (If the method is a "plain
292 old method" that you don't want to be an action at all, then just
293 define the method without any attribute -- you can call it in your
294 code, but the Catalyst dispatcher will ignore it. You will also
295 have to manually include $c if you want access to the context
296 object in the method vs. having Catalyst automatically include $c
297 in the argument list for you if it's a full-fledged action.)
298 There are five types of "special" built-in ":Private" actions:
300 "begin", "end", "default", "index", and "auto".
301 · With "begin", "end", "default", "index" private actions, only
303 the most specific action of each type will be called. For
304 example, if you define a "begin" action in your controller it
305 will override a "begin" action in your application/root
306 controller -- only the action in your controller will be
307 called.
308 · Unlike the other actions where only a single method is called
310 for each request, every auto action along the chain of
311 namespaces will be called. Each "auto" action will be called
312 from the application/root controller down through the most
313 specific class.
314 · :Path -- ":Path" actions let you map a method to an explicit URI
316 path. For example, "":Path('list')"" in
317 lib/MyApp/Controller/Books.pm would match on the URL
318 "http://localhost:3000/books/list", but "":Path('/list')"" would
319 match on "http://localhost:3000/list" (because of the leading
320 slash). You can use ":Args()" to specify how many arguments an
321 action should accept. See "Action-types" in
322 Catalyst::Manual::Intro for more information and examples.
323 · :Local -- ":Local" is merely a shorthand for
325 "":Path('_name_of_method_')"". For example, these are equivalent:
326 ""sub create_book :Local {...}"" and ""sub create_book
327 :Path('create_book') {...}"".
328 · :Global -- ":Global" is merely a shorthand for
330 "":Path('/_name_of_method_')"". For example, these are equivalent:
331 ""sub create_book :Global {...}"" and ""sub create_book
332 :Path('/create_book') {...}"".
333 · :Chained -- Newer Catalyst applications tend to use the Chained
335 dispatch form of action types because of its power and flexibility.
336 It allows a series of controller methods to be automatically
337 dispatched when servicing a single user request. See
338 Catalyst::Manual::Tutorial::04_BasicCRUD and
339 Catalyst::DispatchType::Chained for more information on chained
340 actions.
341 You should refer to "Action-types" in Catalyst::Manual::Intro for
343 additional information and for coverage of some lesser-used action
344 types not discussed here ("Regex" and "LocalRegex").
345
347 As mentioned in Chapter 2 of the tutorial, views are where you render
348 output, typically for display in the user's web browser (but can
349 generate other types of output such as PDF or JSON). The code in
350 lib/MyApp/View selects the type of view to use, with the actual
351 rendering template found in the "root" directory. As with virtually
352 every aspect of Catalyst, options abound when it comes to the specific
353 view technology you adopt inside your application. However, most
354 Catalyst applications use the Template Toolkit, known as TT (for more
355 information on TT, see <http://www.template-toolkit.org>). Other
356 somewhat popular view technologies include Mason
357 (<http://www.masonhq.com> and
358 <https://masonbook.houseabsolute.com/book/>) and HTML::Template.
359 Create a Catalyst View
361 When using TT for the Catalyst view, the main helper script is
362 Catalyst::Helper::View::TT. You may also come across references to
363 Catalyst::Helper::View::TTSite, but its use is now deprecated.
364 For our book application, enter the following command to enable the
366 "TT" style of view rendering:
367 $ script/myapp_create.pl view HTML TT
369 exists "/home/catalyst/MyApp/script/../lib/MyApp/View"
370 exists "/home/catalyst/MyApp/script/../t"
371 created "/home/catalyst/MyApp/script/../lib/MyApp/View/HTML.pm"
372 created "/home/catalyst/MyApp/script/../t/view_HTML.t"
373 This creates a view called "HTML" (the first argument) in a file called
375 "HTML.pm" that uses Catalyst::View::TT (the second argument) as the
376 "rendering engine".
377 It is now up to you to decide how you want to structure your view
379 layout. For the tutorial, we will start with a very simple TT template
380 to initially demonstrate the concepts, but quickly migrate to a more
381 typical "wrapper page" type of configuration (where the "wrapper"
382 controls the overall "look and feel" of your site from a single file or
383 set of files).
384 Edit lib/MyApp/View/HTML.pm and you should see something similar to the
386 following:
387 __PACKAGE__->config(
389 TEMPLATE_EXTENSION => '.tt',
390 render_die => 1,
391 );
392 And update it to match:
394 __PACKAGE__->config(
396 # Change default TT extension
397 TEMPLATE_EXTENSION => '.tt2',
398 render_die => 1,
399 );
400 This changes the default extension for Template Toolkit from '.tt' to
402 '.tt2'.
403 You can also configure components in your application class. For
405 example, Edit lib/MyApp.pm and you should see the default configuration
406 above the call to "_PACKAGE__->setup" (your defaults could be different
407 depending on the version of Catalyst you are using):
408 __PACKAGE__->config(
410 name => 'MyApp',
411 # Disable deprecated behavior needed by old applications
412 disable_component_resolution_regex_fallback => 1,
413 );
414 Change this to match the following (insert a new "__PACKAGE__->config"
416 below the existing statement):
417 __PACKAGE__->config(
419 name => 'MyApp',
420 # Disable deprecated behavior needed by old applications
421 disable_component_resolution_regex_fallback => 1,
422 );
423 __PACKAGE__->config(
424 # Configure the view
425 'View::HTML' => {
426 #Set the location for TT files
427 INCLUDE_PATH => [
428 __PACKAGE__->path_to( 'root', 'src' ),
429 ],
430 },
431 );
432 This changes the base directory for your template files from "root" to
434 root/src.
435 Please stick with the settings above for the duration of the tutorial,
437 but feel free to use whatever options you desire in your applications
438 (as with most things in Perl, there's more than one way to do it...).
439 Note: We will use root/src as the base directory for our template
441 files, with a full naming convention of
442 root/src/_controller_name_/_action_name_.tt2. Another popular option
443 is to use root/ as the base (with a full filename pattern of
444 root/_controller_name_/_action_name_.tt2).
445 Create a TT Template Page
447 First create a directory for book-related TT templates:
448 $ mkdir -p root/src/books
450 Then create root/src/books/list.tt2 in your editor and enter:
452 [% # This is a TT comment. -%]
454 [%- # Provide a title -%]
456 [% META title = 'Book List' -%]
457 [% # Note That the '-' at the beginning or end of TT code -%]
459 [% # "chomps" the whitespace/newline at that end of the -%]
460 [% # output (use View Source in browser to see the effect) -%]
461 [% # Some basic HTML with a loop to display books -%]
463 <table>
464 <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr>
465 [% # Display each book in a table row %]
466 [% FOREACH book IN books -%]
467 <tr>
468 <td>[% book.title %]</td>
469 <td>[% book.rating %]</td>
470 <td></td>
471 </tr>
472 [% END -%]
473 </table>
474 As indicated by the inline comments above, the "META title" line uses
476 TT's META feature to provide a title to the "wrapper" that we will
477 create later (and essentially does nothing at the moment). Meanwhile,
478 the "FOREACH" loop iterates through each "book" model object and prints
479 the "title" and "rating" fields.
480 The "[%" and "%]" tags are used to delimit Template Toolkit code. TT
482 supports a wide variety of directives for "calling" other files,
483 looping, conditional logic, etc. In general, TT simplifies the usual
484 range of Perl operators down to the single dot (".") operator. This
485 applies to operations as diverse as method calls, hash lookups, and
486 list index values (see Template::Manual::Variables for details and
487 examples). In addition to the usual Template::Toolkit module Pod
488 documentation, you can access the TT manual at Template::Manual.
489 TIP: While you can build all sorts of complex logic into your TT
491 templates, you should in general keep the "code" part of your templates
492 as simple as possible. If you need more complex logic, create helper
493 methods in your model that abstract out a set of code into a single
494 call from your TT template. (Note that the same is true of your
495 controller logic as well -- complex sections of code in your
496 controllers should often be pulled out and placed into your model
497 objects.) In Chapter 4 of the tutorial we will explore some extremely
498 helpful and powerful features of DBIx::Class that allow you to pull
499 code out of your views and controllers and place it where it rightfully
500 belongs in a model class.
501 Test Run The Application
503 To test your work so far, first start the development server:
504 $ script/myapp_server.pl -r
506 Then point your browser to <http://localhost:3000> and you should still
508 get the Catalyst welcome page. Next, change the URL in your browser to
509 <http://localhost:3000/books/list>. If you have everything working so
510 far, you should see a web page that displays nothing other than our
511 column headers for "Title", "Rating", and "Author(s)" -- we will not
512 see any books until we get the database and model working below.
513 If you run into problems getting your application to run correctly, it
515 might be helpful to refer to some of the debugging techniques covered
516 in the Debugging chapter of the tutorial.
517
519 In this step, we make a text file with the required SQL commands to
520 create a database table and load some sample data. We will use SQLite
521 (<https://www.sqlite.org>), a popular database that is lightweight and
522 easy to use. Be sure to get at least version 3. Open myapp01.sql in
523 your editor and enter:
524 --
526 -- Create a very simple database to hold book and author information
527 --
528 PRAGMA foreign_keys = ON;
529 CREATE TABLE book (
530 id INTEGER PRIMARY KEY,
531 title TEXT ,
532 rating INTEGER
533 );
534 -- 'book_author' is a many-to-many join table between books & authors
535 CREATE TABLE book_author (
536 book_id INTEGER REFERENCES book(id) ON DELETE CASCADE ON UPDATE CASCADE,
537 author_id INTEGER REFERENCES author(id) ON DELETE CASCADE ON UPDATE CASCADE,
538 PRIMARY KEY (book_id, author_id)
539 );
540 CREATE TABLE author (
541 id INTEGER PRIMARY KEY,
542 first_name TEXT,
543 last_name TEXT
544 );
545 ---
546 --- Load some sample data
547 ---
548 INSERT INTO book VALUES (1, 'CCSP SNRS Exam Certification Guide', 5);
549 INSERT INTO book VALUES (2, 'TCP/IP Illustrated, Volume 1', 5);
550 INSERT INTO book VALUES (3, 'Internetworking with TCP/IP Vol.1', 4);
551 INSERT INTO book VALUES (4, 'Perl Cookbook', 5);
552 INSERT INTO book VALUES (5, 'Designing with Web Standards', 5);
553 INSERT INTO author VALUES (1, 'Greg', 'Bastien');
554 INSERT INTO author VALUES (2, 'Sara', 'Nasseh');
555 INSERT INTO author VALUES (3, 'Christian', 'Degu');
556 INSERT INTO author VALUES (4, 'Richard', 'Stevens');
557 INSERT INTO author VALUES (5, 'Douglas', 'Comer');
558 INSERT INTO author VALUES (6, 'Tom', 'Christiansen');
559 INSERT INTO author VALUES (7, 'Nathan', 'Torkington');
560 INSERT INTO author VALUES (8, 'Jeffrey', 'Zeldman');
561 INSERT INTO book_author VALUES (1, 1);
562 INSERT INTO book_author VALUES (1, 2);
563 INSERT INTO book_author VALUES (1, 3);
564 INSERT INTO book_author VALUES (2, 4);
565 INSERT INTO book_author VALUES (3, 5);
566 INSERT INTO book_author VALUES (4, 6);
567 INSERT INTO book_author VALUES (4, 7);
568 INSERT INTO book_author VALUES (5, 8);
569 Then use the following command to build a myapp.db SQLite database:
571 $ sqlite3 myapp.db < myapp01.sql
573 If you need to create the database more than once, you probably want to
575 issue the "rm myapp.db" command to delete the database before you use
576 the "sqlite3 myapp.db < myapp01.sql" command.
577 Once the myapp.db database file has been created and initialized, you
579 can use the SQLite command line environment to do a quick dump of the
580 database contents:
581 $ sqlite3 myapp.db
583 SQLite version 3.7.3
584 Enter ".help" for instructions
585 Enter SQL statements terminated with a ";"
586 sqlite> select * from book;
587 1|CCSP SNRS Exam Certification Guide|5
588 2|TCP/IP Illustrated, Volume 1|5
589 3|Internetworking with TCP/IP Vol.1|4
590 4|Perl Cookbook|5
591 5|Designing with Web Standards|5
592 sqlite> .q
593 $
594 Or:
596 $ sqlite3 myapp.db "select * from book"
598 1|CCSP SNRS Exam Certification Guide|5
599 2|TCP/IP Illustrated, Volume 1|5
600 3|Internetworking with TCP/IP Vol.1|4
601 4|Perl Cookbook|5
602 5|Designing with Web Standards|5
603 As with most other SQL tools, if you are using the full "interactive"
605 environment you need to terminate your SQL commands with a ";" (it's
606 not required if you do a single SQL statement on the command line).
607 Use ".q" to exit from SQLite from the SQLite interactive mode and
608 return to your OS command prompt.
609 Please note that here we have chosen to use 'singular' table names.
611 This is because the default inflection code for older versions of
612 DBIx::Class::Schema::Loader does NOT handle plurals. There has been
613 much philosophical discussion on whether table names should be plural
614 or singular. There is no one correct answer, as long as one makes a
615 choice and remains consistent with it. If you prefer plural table names
616 (e.g. you think that they are easier to read) then see the
617 documentation in "naming" in DBIx::Class::Schema::Loader::Base (version
618 0.05 or greater).
619 For using other databases, such as PostgreSQL or MySQL, see Appendix 2.
621
623 Catalyst can be used with virtually any form of datastore available via
624 Perl. For example, Catalyst::Model::DBI can be used to access
625 databases through the traditional Perl DBI interface or you can use a
626 model to access files of any type on the filesystem. However, most
627 Catalyst applications use some form of object-relational mapping (ORM)
628 technology to create objects associated with tables in a relational
629 database, and Matt Trout's DBIx::Class (abbreviated as "DBIC") is the
630 usual choice (this tutorial will use DBIx::Class).
631 Although DBIx::Class has included support for a "create=dynamic" mode
633 to automatically read the database structure every time the application
634 starts, its use is no longer recommended. While it can make for
635 "flashy" demos, the use of the "create=static" mode we use below can be
636 implemented just as quickly and provides many advantages (such as the
637 ability to add your own methods to the overall DBIC framework, a
638 technique that we see in Chapter 4).
639 Create Static DBIx::Class Schema Files
641 Note: If you are not following along in the Tutorial Virtual Machine,
642 please be sure that you have version 1.27 or higher of DBD::SQLite and
643 version 0.39 or higher of Catalyst::Model::DBIC::Schema. (The Tutorial
644 VM already has versions that are known to work.) You can get your
645 currently installed version numbers with the following commands.
646 $ perl -MCatalyst::Model::DBIC::Schema\ 999
648 $ perl -MDBD::SQLite\ 999
649 Before you continue, make sure your myapp.db database file is in the
651 application's topmost directory. Now use the model helper with the
652 "create=static" option to read the database with
653 DBIx::Class::Schema::Loader and automatically build the required files
654 for us:
655 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
657 create=static dbi:SQLite:myapp.db \
658 on_connect_do="PRAGMA foreign_keys = ON"
659 exists "/home/catalyst/MyApp/script/../lib/MyApp/Model"
660 exists "/home/catalyst/MyApp/script/../t"
661 Dumping manual schema for MyApp::Schema to directory /home/catalyst/MyApp/script/../lib ...
662 Schema dump completed.
663 created "/home/catalyst/MyApp/script/../lib/MyApp/Model/DB.pm"
664 created "/home/catalyst/MyApp/script/../t/model_DB.t"
665 Please note the '\' above. Depending on your environment, you might be
667 able to cut and paste the text as shown or need to remove the '\'
668 character to that the command is all on a single line.
669 The script/myapp_create.pl command breaks down like this:
671 · "DB" is the name of the model class to be created by the helper in
673 the lib/MyApp/Model directory.
674 · "DBIC::Schema" is the type of the model to create. This equates to
676 Catalyst::Model::DBIC::Schema, the standard way to use a DBIC-based
677 model inside of Catalyst.
678 · "MyApp::Schema" is the name of the DBIC schema file written to
680 lib/MyApp/Schema.pm.
681 · "create=static" causes DBIx::Class::Schema::Loader to load the
683 schema as it runs and then write that information out into
684 lib/MyApp/Schema.pm and files under the lib/MyApp/Schema directory.
685 · "dbi:SQLite:myapp.db" is the standard DBI connect string for use
687 with SQLite.
688 · And finally, the "on_connect_do" string requests that
690 DBIx::Class::Schema::Loader create foreign key relationships for us
691 (this is not needed for databases such as PostgreSQL and MySQL, but
692 is required for SQLite). If you take a look at
693 lib/MyApp/Model/DB.pm, you will see that the SQLite pragma is
694 propagated to the Model, so that SQLite's recent (and optional)
695 foreign key enforcement is enabled at the start of every database
696 connection.
697 If you look in the lib/MyApp/Schema.pm file, you will find that it only
699 contains a call to the "load_namespaces" method. You will also find
700 that lib/MyApp contains a "Schema" subdirectory, which then has a
701 subdirectory called "Result". This "Result" subdirectory then has
702 files named according to each of the tables in our simple database
703 (Author.pm, BookAuthor.pm, and Book.pm). These three files are called
704 "Result Classes" (or "ResultSource Classes") in DBIx::Class
705 nomenclature. Although the Result Class files are named after tables in
706 our database, the classes correspond to the row-level data that is
707 returned by DBIC (more on this later, especially in "EXPLORING THE
708 POWER OF DBIC" in Catalyst::Manual::Tutorial::04_BasicCRUD).
709 The idea with the Result Source files created under
711 lib/MyApp/Schema/Result by the "create=static" option is to only edit
712 the files below the "# DO NOT MODIFY THIS OR ANYTHING ABOVE!" warning.
713 If you place all of your changes below that point in the file, you can
714 regenerate the automatically created information at the top of each
715 file should your database structure get updated.
716 Also note the "flow" of the model information across the various files
718 and directories. Catalyst will initially load the model from
719 lib/MyApp/Model/DB.pm. This file contains a reference to
720 lib/MyApp/Schema.pm, so that file is loaded next. Finally, the call to
721 "load_namespaces" in "Schema.pm" will load each of the "Result Class"
722 files from the lib/MyApp/Schema/Result subdirectory. The final outcome
723 is that Catalyst will dynamically create three table-specific Catalyst
724 models every time the application starts (you can see these three model
725 files listed in the debug output generated when you launch the
726 application).
727 Additionally, the lib/MyApp/Schema.pm model can easily be loaded
729 outside of Catalyst, for example, in command-line utilities and/or cron
730 jobs. lib/MyApp/Model/DB.pm provides a very thin "bridge" between
731 Catalyst and this external database model. Once you see how we can add
732 some powerful features to our DBIC model in Chapter 4, the elegance of
733 this approach will start to become more obvious.
734 NOTE: Older versions of Catalyst::Model::DBIC::Schema use the
736 deprecated DBIx::Class "load_classes" technique instead of the newer
737 "load_namespaces". For new applications, please try to use
738 "load_namespaces" since it more easily supports a very useful DBIC
739 technique called "ResultSet Classes." If you need to convert an
740 existing application from "load_classes" to "load_namespaces," you can
741 use this process to automate the migration, but first make sure you
742 have version 0.39 of Catalyst::Model::DBIC::Schema and
743 DBIx::Class::Schema::Loader version 0.05000 or later.
744 $ # Re-run the helper to upgrade for you
746 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
747 create=static naming=current use_namespaces=1 \
748 dbi:SQLite:myapp.db \
749 on_connect_do="PRAGMA foreign_keys = ON"
750
752 Open lib/MyApp/Controller/Books.pm and un-comment the model code we
753 left disabled earlier so that your version matches the following (un-
754 comment the line containing "[$c->model('DB::Book')->all]" and delete
755 the next 2 lines):
756 =head2 list
758 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
760 =cut
762 sub list :Local {
764 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
765 # 'Context' that's used to 'glue together' the various components
766 # that make up the application
767 my ($self, $c) = @_;
768 # Retrieve all of the book records as book model objects and store
770 # in the stash where they can be accessed by the TT template
771 $c->stash(books => [$c->model('DB::Book')->all]);
772 # Set the TT template to use. You will almost always want to do this
774 # in your action methods (action methods respond to user input in
775 # your controllers).
776 $c->stash(template => 'books/list.tt2');
777 }
778 TIP: You may see the "$c->model('DB::Book')" un-commented above written
780 as "$c->model('DB')->resultset('Book')". The two are equivalent.
781 Either way, "$c->model" returns a DBIx::Class::ResultSet which handles
782 queries against the database and iterating over the set of results that
783 is returned.
784 We are using the "->all" to fetch all of the books. DBIC supports a
786 wide variety of more advanced operations to easily do things like
787 filtering and sorting the results. For example, the following could be
788 used to sort the results by descending title:
789 $c->model('DB::Book')->search({}, {order_by => 'title DESC'});
791 Some other examples are provided in "Complex WHERE clauses" in
793 DBIx::Class::Manual::Cookbook, with additional information found at
794 "search" in DBIx::Class::ResultSet, "Searching" in
795 DBIx::Class::Manual::FAQ, DBIx::Class::Manual::Intro and
796 Catalyst::Model::DBIC::Schema.
797 Test Run The Application
799 First, let's enable an environment variable that causes DBIx::Class to
800 dump the SQL statements used to access the database. This is a helpful
801 trick when you are trying to debug your database-oriented code. Press
802 "Ctrl-C" to break out of the development server and enter:
803 $ export DBIC_TRACE=1
805 $ script/myapp_server.pl -r
806 This assumes you are using bash as your shell -- adjust accordingly if
808 you are using a different shell (for example, under tcsh, use "setenv
809 DBIC_TRACE 1").
810 NOTE: You can also set this in your code using
812 "$class->storage->debug(1);". See DBIx::Class::Manual::Troubleshooting
813 for details (including options to log to a file instead of displaying
814 to the Catalyst development server log).
815 Then launch the Catalyst development server. The log output should
817 display something like:
818 $ script/myapp_server.pl -r
820 [debug] Debug messages enabled
821 [debug] Statistics enabled
822 [debug] Loaded plugins:
823 .----------------------------------------------------------------------------.
824 | Catalyst::Plugin::ConfigLoader 0.30 |
825 | Catalyst::Plugin::StackTrace 0.11 |
826 '----------------------------------------------------------------------------'
827 [debug] Loaded dispatcher "Catalyst::Dispatcher"
829 [debug] Loaded engine "Catalyst::Engine"
830 [debug] Found home "/home/catalyst/MyApp"
831 [debug] Loaded Config "/home/catalyst/MyApp/myapp.conf"
832 [debug] Loaded components:
833 .-----------------------------------------------------------------+----------.
834 | Class | Type |
835 +-----------------------------------------------------------------+----------+
836 | MyApp::Controller::Books | instance |
837 | MyApp::Controller::Root | instance |
838 | MyApp::Model::DB | instance |
839 | MyApp::Model::DB::Author | class |
840 | MyApp::Model::DB::Book | class |
841 | MyApp::Model::DB::BookAuthor | class |
842 | MyApp::View::HTML | instance |
843 '-----------------------------------------------------------------+----------'
844 [debug] Loaded Private actions:
846 .----------------------+--------------------------------------+--------------.
847 | Private | Class | Method |
848 +----------------------+--------------------------------------+--------------+
849 | /default | MyApp::Controller::Root | default |
850 | /end | MyApp::Controller::Root | end |
851 | /index | MyApp::Controller::Root | index |
852 | /books/index | MyApp::Controller::Books | index |
853 | /books/list | MyApp::Controller::Books | list |
854 '----------------------+--------------------------------------+--------------'
855 [debug] Loaded Path actions:
857 .-------------------------------------+--------------------------------------.
858 | Path | Private |
859 +-------------------------------------+--------------------------------------+
860 | / | /default |
861 | / | /index |
862 | /books | /books/index |
863 | /books/list | /books/list |
864 '-------------------------------------+--------------------------------------'
865 [info] MyApp powered by Catalyst 5.80020
867 HTTP::Server::PSGI: Accepting connections at http://0:3000
868 NOTE: Be sure you run the script/myapp_server.pl command from the
870 'base' directory of your application, not inside the script directory
871 itself or it will not be able to locate the myapp.db database file.
872 You can use a fully qualified or a relative path to locate the database
873 file, but we did not specify that when we ran the model helper earlier.
874 Some things you should note in the output above:
876 · Catalyst::Model::DBIC::Schema dynamically created three model
878 classes, one to represent each of the three tables in our database
879 ("MyApp::Model::DB::Author", "MyApp::Model::DB::BookAuthor", and
880 "MyApp::Model::DB::Book").
881 · The "list" action in our Books controller showed up with a path of
883 "/books/list".
884 Point your browser to <http://localhost:3000> and you should still get
886 the Catalyst welcome page.
887 Next, to view the book list, change the URL in your browser to
889 <http://localhost:3000/books/list>. You should get a list of the five
890 books loaded by the myapp01.sql script above without any formatting.
891 The rating for each book should appear on each row, but the "Author(s)"
892 column will still be blank (we will fill that in later).
893 Also notice in the output of the script/myapp_server.pl that
895 DBIx::Class used the following SQL to retrieve the data:
896 SELECT me.id, me.title, me.rating FROM book me
898 because we enabled DBIC_TRACE.
900 You now have the beginnings of a simple but workable web application.
902 Continue on to future sections and we will develop the application more
903 fully.
904
906 When using TT, you can (and should) create a wrapper that will
907 literally wrap content around each of your templates. This is
908 certainly useful as you have one main source for changing things that
909 will appear across your entire site/application instead of having to
910 edit many individual files.
911 Configure HTML.pm For The Wrapper
913 In order to create a wrapper, you must first edit your TT view and tell
914 it where to find your wrapper file.
915 Edit your TT view in lib/MyApp/View/HTML.pm and change it to match the
917 following:
918 __PACKAGE__->config(
920 # Change default TT extension
921 TEMPLATE_EXTENSION => '.tt2',
922 # Set the location for TT files
923 INCLUDE_PATH => [
924 MyApp->path_to( 'root', 'src' ),
925 ],
926 # Set to 1 for detailed timer stats in your HTML as comments
927 TIMER => 0,
928 # This is your wrapper template located in the 'root/src'
929 WRAPPER => 'wrapper.tt2',
930 );
931 Create the Wrapper Template File and Stylesheet
933 Next you need to set up your wrapper template. Basically, you'll want
934 to take the overall layout of your site and put it into this file. For
935 the tutorial, open root/src/wrapper.tt2 and input the following:
936 <?xml version="1.0" encoding="UTF-8"?>
938 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" [%#
939 %]"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
940 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
941 <head>
942 <title>[% template.title or "My Catalyst App!" %]</title>
943 <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" />
944 </head>
945 <body>
947 <div id="outer">
948 <div id="header">
949 [%# Your logo could go here -%]
950 <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" />
951 [%# Insert the page title -%]
952 <h1>[% template.title or site.title %]</h1>
953 </div>
954 <div id="bodyblock">
956 <div id="menu">
957 Navigation:
958 <ul>
959 <li><a href="[% c.uri_for('/books/list') %]">Home</a></li>
960 <li><a href="[% c.uri_for('/')
961 %]" title="Catalyst Welcome Page">Welcome</a></li>
962 </ul>
963 </div><!-- end menu -->
964 <div id="content">
966 [%# Status and error messages %]
967 <span class="message">[% status_msg %]</span>
968 <span class="error">[% error_msg %]</span>
969 [%# This is where TT will stick all of your template's contents. -%]
970 [% content %]
971 </div><!-- end content -->
972 </div><!-- end bodyblock -->
973 <div id="footer">Copyright (c) your name goes here</div>
975 </div><!-- end outer -->
976 </body>
978 </html>
979 Notice the status and error message sections in the code above:
981 <span class="status">[% status_msg %]</span>
983 <span class="error">[% error_msg %]</span>
984 If we set either message in the Catalyst stash (e.g.,
986 "$c->stash->{status_msg} = 'Request was successful!'") it will be
987 displayed whenever any view used by that request is rendered. The
988 "message" and "error" CSS styles can be customized to suit your needs
989 in the root/static/css/main.css file we create below.
990 Notes:
992 · The Catalyst stash only lasts for a single HTTP request. If you
994 need to retain information across requests you can use
995 Catalyst::Plugin::Session (we will use Catalyst sessions in the
996 Authentication chapter of the tutorial).
997 · Although it is beyond the scope of this tutorial, you may wish to
999 use a JavaScript or AJAX tool such as jQuery
1000 (<https://www.jquery.com>) or Dojo (<https://dojotoolkit.org/>).
1001 Create A Basic Stylesheet
1003 First create a central location for stylesheets under the static
1005 directory:
1006 $ mkdir root/static/css
1008 Then open the file root/static/css/main.css (the file referenced in the
1010 stylesheet href link of our wrapper above) and add the following
1011 content:
1012 #header {
1014 text-align: center;
1015 }
1016 #header h1 {
1017 margin: 0;
1018 }
1019 #header img {
1020 float: right;
1021 }
1022 #footer {
1023 text-align: center;
1024 font-style: italic;
1025 padding-top: 20px;
1026 }
1027 #menu {
1028 font-weight: bold;
1029 background-color: #ddd;
1030 }
1031 #menu ul {
1032 list-style: none;
1033 float: left;
1034 margin: 0;
1035 padding: 0 0 50% 5px;
1036 font-weight: normal;
1037 background-color: #ddd;
1038 width: 100px;
1039 }
1040 #content {
1041 margin-left: 120px;
1042 }
1043 .message {
1044 color: #390;
1045 }
1046 .error {
1047 color: #f00;
1048 }
1049 You may wish to check out a "CSS Framework" like Emastic
1051 (<http://code.google.com/p/emastic/>) as a way to quickly provide lots
1052 of high-quality CSS functionality.
1053 Test Run The Application
1055 Hit "Reload" in your web browser and you should now see a formatted
1056 version of our basic book list. (Again, the development server should
1057 have automatically restarted when you made changes to
1058 lib/MyApp/View/HTML.pm. If you are not using the "-r" option, you will
1059 need to hit "Ctrl-C" and manually restart it. Also note that the
1060 development server does NOT need to restart for changes to the TT and
1061 static files we created and edited in the "root" directory -- those
1062 updates are handled on a per-request basis.)
1063 Although our wrapper and stylesheet are obviously very simple, you
1065 should see how it allows us to control the overall look of an entire
1066 website from two central files. To add new pages to the site, just
1067 provide a template that fills in the "content" section of our wrapper
1068 template -- the wrapper will provide the overall feel of the page.
1069 Updating the Generated DBIx::Class Result Class Files
1071 If you take a look at the Schema files automatically generated by
1072 DBIx::Class::Schema::Loader, you will see that it has already defined
1073 "has_many" and "belongs_to" relationships on each side of our foreign
1074 keys. For example, take a look at lib/MyApp/Schema/Result/Book.pm and
1075 notice the following code:
1076 =head1 RELATIONS
1078 =head2 book_authors
1080 Type: has_many
1082 Related object: L<MyApp::Schema::Result::BookAuthor>
1084 =cut
1086 __PACKAGE__->has_many(
1088 "book_authors",
1089 "MyApp::Schema::Result::BookAuthor",
1090 { "foreign.book_id" => "self.id" },
1091 { cascade_copy => 0, cascade_delete => 0 },
1092 );
1093 Each "Book" "has_many" "book_authors", where "BookAuthor" is the many-
1095 to-many table that allows each Book to have multiple Authors, and each
1096 Author to have multiple books. The arguments to "has_many" are:
1097 · "book_authors" - The name for this relationship. DBIC will create
1099 an accessor on the "Books" DBIC Row object with this name.
1100 · "MyApp::Schema::Result::BookAuthor" - The name of the DBIC model
1102 class referenced by this "has_many" relationship.
1103 · "foreign.book_id" - "book_id" is the name of the foreign key column
1105 in the foreign table that points back to this table.
1106 · "self.id" - "id" is the name of the column in this table that is
1108 referenced by the foreign key.
1109 See "has_many" in DBIx::Class::Relationship for additional information.
1111 Note that you might see a "hand coded" version of the "has_many"
1112 relationship above expressed as:
1113 __PACKAGE__->has_many(
1115 "book_authors",
1116 "MyApp::Schema::Result::BookAuthor",
1117 "book_id",
1118 );
1119 Where the third argument is simply the name of the column in the
1121 foreign table. However, the hashref syntax used by
1122 DBIx::Class::Schema::Loader is more flexible (for example, it can
1123 handle "multi-column foreign keys").
1124 Note: If you are using older versions of SQLite and related DBIC tools,
1126 you will need to manually define your "has_many" and "belongs_to"
1127 relationships. We recommend upgrading to the versions specified above.
1128 :-)
1129 Have a look at lib/MyApp/Schema/Result/BookAuthor.pm and notice that
1131 there is a "belongs_to" relationship defined that acts as the "mirror
1132 image" to the "has_many" relationship we just looked at above:
1133 =head1 RELATIONS
1135 =head2 book
1137 Type: belongs_to
1139 Related object: L<MyApp::Schema::Result::Book>
1141 =cut
1143 __PACKAGE__->belongs_to(
1145 "book",
1146 "MyApp::Schema::Result::Book",
1147 { id => "book_id" },
1148 { join_type => "LEFT", on_delete => "CASCADE", on_update => "CASCADE" },
1149 );
1150 The arguments are similar, but see "belongs_to" in
1152 DBIx::Class::Relationship for the details.
1153 Although recent versions of SQLite and DBIx::Class::Schema::Loader
1155 automatically handle the "has_many" and "belongs_to" relationships,
1156 "many_to_many" relationship bridges (not technically a relationship)
1157 currently need to be manually inserted. To add a "many_to_many"
1158 relationship bridge, first edit lib/MyApp/Schema/Result/Book.pm and add
1159 the following text below the "# You can replace this text..." comment:
1160 # many_to_many():
1162 # args:
1163 # 1) Name of relationship bridge, DBIC will create accessor with this name
1164 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1165 # 3) Name of belongs_to() relationship in model class of has_many() above
1166 # You must already have the has_many() defined to use a many_to_many().
1167 __PACKAGE__->many_to_many(authors => 'book_authors', 'author');
1168 Note: Be careful to put this code above the "1;" at the end of the
1170 file. As with any Perl package, we need to end the last line with a
1171 statement that evaluates to "true". This is customarily done with "1;"
1172 on a line by itself.
1173 The "many_to_many" relationship bridge is optional, but it makes it
1175 easier to map a book to its collection of authors. Without it, we
1176 would have to "walk" through the "book_author" table as in
1177 "$book->book_author->first->author->last_name" (we will see examples on
1178 how to use DBIx::Class objects in your code soon, but note that because
1179 "$book->book_author" can return multiple authors, we have to use
1180 "first" to display a single author). "many_to_many" allows us to use
1181 the shorter "$book->author->first->last_name". Note that you cannot
1182 define a "many_to_many" relationship bridge without also having the
1183 "has_many" relationship in place.
1184 Then edit lib/MyApp/Schema/Result/Author.pm and add the reverse
1186 "many_to_many" relationship bridge for "Author" as follows (again, be
1187 careful to put in above the "1;" but below the "# DO NOT MODIFY THIS OR
1188 ANYTHING ABOVE!" comment):
1189 # many_to_many():
1191 # args:
1192 # 1) Name of relationship bridge, DBIC will create accessor with this name
1193 # 2) Name of has_many() relationship this many_to_many() is shortcut for
1194 # 3) Name of belongs_to() relationship in model class of has_many() above
1195 # You must already have the has_many() defined to use a many_to_many().
1196 __PACKAGE__->many_to_many(books => 'book_authors', 'book');
1197 Run The Application
1199 Run the Catalyst development server script with the "DBIC_TRACE" option
1200 (it might still be enabled from earlier in the tutorial, but here is an
1201 alternate way to specify the trace option just in case):
1202 $ DBIC_TRACE=1 script/myapp_server.pl -r
1204 Make sure that the application loads correctly and that you see the
1206 three dynamically created model classes (one for each of the Result
1207 Classes we created).
1208 Then hit the URL <http://localhost:3000/books/list> with your browser
1210 and be sure that the book list still displays correctly.
1211 Note: You will not see the authors yet because the view isn't taking
1213 advantage of these relationships. Read on to the next section where we
1214 update the template to do that.
1215
1217 Let's add a new column to our book list page that takes advantage of
1218 the relationship information we manually added to our schema files in
1219 the previous section. Edit root/src/books/list.tt2 and replace the
1220 "empty" table cell ""<td></td>"" with the following:
1221 ...
1223 <td>
1224 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1225 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1226 [% # loop in 'side effect notation' to load just the last names of the -%]
1227 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
1228 [% # a value, so nothing will be printed here. But, if you have something -%]
1229 [% # in TT that does return a value and you don't want it printed, you -%]
1230 [% # 1) assign it to a bogus value, or -%]
1231 [% # 2) use the CALL keyword to call it and discard the return value. -%]
1232 [% tt_authors = [ ];
1233 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1234 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1235 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1236 ([% tt_authors.size | html %])
1237 [% # Use another TT vmethod to join & print the names & comma separators -%]
1238 [% tt_authors.join(', ') | html %]
1239 </td>
1240 ...
1241 IMPORTANT NOTE: Again, you should keep as much "logic code" as possible
1243 out of your views. This kind of logic belongs in your model (the same
1244 goes for controllers -- keep them as "thin" as possible and push all of
1245 the "complicated code" out to your model objects). Avoid code like you
1246 see in the previous example -- we are only using it here to show some
1247 extra features in TT until we get to the more advanced model features
1248 we will see in Chapter 4 (see "EXPLORING THE POWER OF DBIC" in
1249 Catalyst::Manual::Tutorial::04_BasicCRUD).
1250 Then hit "Reload" in your browser (note that you don't need to reload
1252 the development server or use the "-r" option when updating TT
1253 templates) and you should now see the number of authors each book has
1254 along with a comma-separated list of the authors' last names. (If you
1255 didn't leave the development server running from the previous step, you
1256 will obviously need to start it before you can refresh your browser
1257 window.)
1258 If you are still running the development server with "DBIC_TRACE"
1260 enabled, you should also now see five more "SELECT" statements in the
1261 debug output (one for each book as the authors are being retrieved by
1262 DBIx::Class):
1263 SELECT me.id, me.title, me.rating FROM book me:
1265 SELECT author.id, author.first_name, author.last_name FROM book_author me
1266 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '1'
1267 SELECT author.id, author.first_name, author.last_name FROM book_author me
1268 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '2'
1269 SELECT author.id, author.first_name, author.last_name FROM book_author me
1270 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '3'
1271 SELECT author.id, author.first_name, author.last_name FROM book_author me
1272 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '4'
1273 SELECT author.id, author.first_name, author.last_name FROM book_author me
1274 JOIN author author ON author.id = me.author_id WHERE ( me.book_id = ? ): '5'
1275 Also note in root/src/books/list.tt2 that we are using "| html", a type
1277 of TT filter, to escape characters such as < and > to < and > and
1278 avoid various types of dangerous hacks against your application. In a
1279 real application, you would probably want to put "| html" at the end of
1280 every field where a user has control over the information that can
1281 appear in that field (and can therefore inject markup or code if you
1282 don't "neutralize" those fields). In addition to "| html", Template
1283 Toolkit has a variety of other useful filters that can be found in the
1284 documentation for Template::Filters. (While we are on the topic of
1285 security and escaping of dangerous values, one of the advantages of
1286 using tools like DBIC for database access or HTML::FormFu for form
1287 management [see Chapter 9] is that they automatically handle most
1288 escaping for you and therefore dramatically increase the security of
1289 your app.)
1290
1292 In some situations, it can be useful to run your application and
1293 display a page without using a browser. Catalyst lets you do this
1294 using the script/myapp_test.pl script. Just supply the URL you wish to
1295 display and it will run that request through the normal controller
1296 dispatch logic and use the appropriate view to render the output
1297 (obviously, complex pages may dump a lot of text to your terminal
1298 window). For example, if "Ctrl+C" out of the development server and
1299 then type:
1300 $ script/myapp_test.pl "/books/list"
1302 You should get the same text as if you visited
1304 <http://localhost:3000/books/list> with the normal development server
1305 and asked your browser to view the page source. You can even pipe this
1306 HTML text output to a text-based browser using a command like:
1307 $ script/myapp_test.pl "/books/list" | lynx -stdin
1309 And you should see a fully rendered text-based view of your page. (If
1311 you are following along in Debian 6, type "sudo aptitude -y install
1312 lynx" to install lynx.) If you do start lynx, you can use the "Q" key
1313 to quit.
1314
1316 NOTE: The rest of this chapter of the tutorial is optional. You can
1317 skip to Chapter 4, Basic CRUD, if you wish.
1318 Using 'RenderView' for the Default View
1320 Once your controller logic has processed the request from a user, it
1321 forwards processing to your view in order to generate the appropriate
1322 response output. Catalyst uses Catalyst::Action::RenderView by default
1323 to automatically perform this operation. If you look in
1324 lib/MyApp/Controller/Root.pm, you should see the empty definition for
1325 the "sub end" method:
1326 sub end : ActionClass('RenderView') {}
1328 The following bullet points provide a quick overview of the
1330 "RenderView" process:
1331 · Root.pm is designed to hold application-wide logic.
1333 · At the end of a given user request, Catalyst will call the most
1335 specific "end" method that's appropriate. For example, if the
1336 controller for a request has an "end" method defined, it will be
1337 called. However, if the controller does not define a controller-
1338 specific "end" method, the "global" "end" method in Root.pm will be
1339 called.
1340 · Because the definition includes an "ActionClass" attribute, the
1342 Catalyst::Action::RenderView logic will be executed after any code
1343 inside the definition of "sub end" is run. See
1344 Catalyst::Manual::Actions for more information on "ActionClass".
1345 · Because "sub end" is empty, this effectively just runs the default
1347 logic in "RenderView". However, you can easily extend the
1348 "RenderView" logic by adding your own code inside the empty method
1349 body ("{}") created by the Catalyst Helpers when we first ran the
1350 catalyst.pl to initialize our application. See
1351 Catalyst::Action::RenderView for more detailed information on how
1352 to extend "RenderView" in "sub end".
1353 RenderView's "dump_info" Feature
1355 One of the nice features of "RenderView" is that it automatically
1356 allows you to add "dump_info=1" to the end of any URL for your
1357 application and it will force the display of the "exception dump"
1358 screen to the client browser. You can try this out by pointing your
1359 browser to this URL:
1360 http://localhost:3000/books/list?dump_info=1
1362 You should get a page with the following message at the top:
1364 Caught exception in MyApp::Controller::Root->end "Forced debug -
1366 Scrubbed output at /usr/share/perl5/Catalyst/Action/RenderView.pm line 46."
1367 Along with a summary of your application's state at the end of the
1369 processing for that request. The "Stash" section should show a
1370 summarized version of the DBIC book model objects. If desired, you can
1371 adjust the summarization logic (called "scrubbing" logic) -- see
1372 Catalyst::Action::RenderView for details.
1373 Note that you shouldn't need to worry about "normal clients" using this
1375 technique to "reverse engineer" your application -- "RenderView" only
1376 supports the "dump_info=1" feature when your application is running in
1377 "-Debug" mode (something you won't do once you have your application
1378 deployed in production).
1379 Using The Default Template Name
1381 By default, "Catalyst::View::TT" will look for a template that uses the
1382 same name as your controller action, allowing you to save the step of
1383 manually specifying the template name in each action. For example,
1384 this would allow us to remove the "$c->stash->{template} =
1385 'books/list.tt2';" line of our "list" action in the Books controller.
1386 Open "lib/MyApp/Controller/Books.pm" in your editor and comment out
1387 this line to match the following (only the "$c->stash->{template}" line
1388 has changed):
1389 =head2 list
1391 Fetch all book objects and pass to books/list.tt2 in stash to be displayed
1393 =cut
1395 sub list :Local {
1397 # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst
1398 # 'Context' that's used to 'glue together' the various components
1399 # that make up the application
1400 my ($self, $c) = @_;
1401 # Retrieve all of the book records as book model objects and store in the
1403 # stash where they can be accessed by the TT template
1404 $c->stash(books => [$c->model('DB::Book')->all]);
1405 # Set the TT template to use. You will almost always want to do this
1407 # in your action methods (actions methods respond to user input in
1408 # your controllers).
1409 #$c->stash(template => 'books/list.tt2');
1410 }
1411 You should now be able to access the <http://localhost:3000/books/list>
1413 URL as before.
1414 NOTE: If you use the default template technique, you will not be able
1416 to use either the "$c->forward" or the "$c->detach" mechanisms (these
1417 are discussed in Chapter 2 and Chapter 9 of the Tutorial).
1418 IMPORTANT: Make sure that you do not skip the following section before
1420 continuing to the next chapter 4 Basic CRUD.
1421 Return To A Manually Specified Template
1423 In order to be able to use "$c->forward" and "$c->detach" later in the
1424 tutorial, you should remove the comment from the statement in "sub
1425 list" in lib/MyApp/Controller/Books.pm:
1426 $c->stash(template => 'books/list.tt2');
1428 Then delete the "TEMPLATE_EXTENSION" line in lib/MyApp/View/HTML.pm.
1430 Check the <http://localhost:3000/books/list> URL in your browser. It
1432 should look the same manner as with earlier sections.
1433 You can jump to the next chapter of the tutorial here: Basic CRUD
1435
1437 Kennedy Clark, "hkclark@gmail.com"
1438 Feel free to contact the author for any errors or suggestions, but the
1440 best way to report issues is via the CPAN RT Bug system at
1441 <https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
1442 Copyright 2006-2011, Kennedy Clark, under the Creative Commons
1444 Attribution Share-Alike License Version 3.0
1445 (<https://creativecommons.org/licenses/by-sa/3.0/us/>).
1446perl v5.30.0 Catalyst2:0:1M9a-n0u7a-l2:6:Tutorial::03_MoreCatalystBasics(3)