Add clarification about need for "| html"
[catagits/Catalyst-Manual.git] / lib / Catalyst / Manual / Tutorial / 04_BasicCRUD.pod
fbbb9084 1=head1 NAME
d442cc9f 2
3ab6187c 3Catalyst::Manual::Tutorial::04_BasicCRUD - Catalyst Tutorial - Chapter 4: Basic CRUD
d442cc9f 4
6=head1 OVERVIEW
4b4d3884 8This is B<Chapter 4 of 10> for the Catalyst tutorial.
d442cc9f 9
10L<Tutorial Overview|Catalyst::Manual::Tutorial>
12=over 4
14=item 1
3ab6187c 16L<Introduction|Catalyst::Manual::Tutorial::01_Intro>
d442cc9f 17
18=item 2
3ab6187c 20L<Catalyst Basics|Catalyst::Manual::Tutorial::02_CatalystBasics>
d442cc9f 21
22=item 3
3ab6187c 24L<More Catalyst Basics|Catalyst::Manual::Tutorial::03_MoreCatalystBasics>
d442cc9f 25
26=item 4
3ab6187c 28B<04_Basic CRUD>
d442cc9f 29
30=item 5
3ab6187c 32L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>
d442cc9f 33
34=item 6
3ab6187c 36L<Authorization|Catalyst::Manual::Tutorial::06_Authorization>
d442cc9f 37
38=item 7
3ab6187c 40L<Debugging|Catalyst::Manual::Tutorial::07_Debugging>
d442cc9f 41
42=item 8
3ab6187c 44L<Testing|Catalyst::Manual::Tutorial::08_Testing>
d442cc9f 45
46=item 9
3ab6187c 48L<Advanced CRUD|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
3533daff 49
50=item 10
3ab6187c 52L<Appendices|Catalyst::Manual::Tutorial::10_Appendices>
d442cc9f 53
d442cc9f 57=head1 DESCRIPTION
ee53cc71 59This chapter of the tutorial builds on the fairly primitive application
22fe0f18 60created in
61L<Chapter 3|Catalyst::Manual::Tutorial::03_MoreCatalystBasics> to add
62basic support for Create, Read, Update, and Delete (CRUD) of C<Book>
a9a6fb3f 63objects. Note that the 'list' function in
64L<Chapter 3|Catalyst::Manual::Tutorial::03_MoreCatalystBasics> already
65implements the Read portion of CRUD (although Read normally refers to
66reading a single object; you could implement full Read functionality
67using the techniques introduced below). This section will focus on the
68Create and Delete aspects of CRUD. More advanced capabilities,
69including full Update functionality, will be addressed in
22fe0f18 70L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>.
ee53cc71 71
72Although this chapter of the tutorial will show you how to build CRUD
73functionality yourself, another option is to use a "CRUD builder" type
74of tool to automate the process. You get less control, but it can be
75quick and easy. For example, see L<Catalyst::Plugin::AutoCRUD>,
76L<CatalystX::CRUD>, and L<CatalystX::CRUD::YUI>.
1390ef0e 77
72609296 78You can check out the source code for this example from the Catalyst
79Subversion repository as per the instructions in
2217b252 80L<Catalyst::Manual::Tutorial::01_Intro>.
d442cc9f 81
3533daff 82
d442cc9f 83=head1 FORMLESS SUBMISSION
ee53cc71 85Our initial attempt at object creation will utilize the "URL arguments"
22fe0f18 86feature of Catalyst (we will employ the more common form-based
ee53cc71 87submission in the sections that follow).
d442cc9f 88
90=head2 Include a Create Action in the Books Controller
92Edit C<lib/MyApp/Controller/> and enter the following method:
94 =head2 url_create
fce83e5f 95
d442cc9f 96 Create a book with the supplied title, rating, and author
fce83e5f 97
d442cc9f 98 =cut
fce83e5f 99
f2bbfc36 100 sub url_create :Local {
55490817 101 # In addition to self & context, get the title, rating, &
102 # author_id args from the URL. Note that Catalyst automatically
103 # puts extra information after the "/<controller_name>/<action_name/"
fce83e5f 104 # into @_. The args are separated by the '/' char on the URL.
d442cc9f 105 my ($self, $c, $title, $rating, $author_id) = @_;
fce83e5f 106
55490817 107 # Call create() on the book model object. Pass the table
d442cc9f 108 # columns/field values we want to set as hash values
3b1fa91b 109 my $book = $c->model('DB::Book')->create({
d442cc9f 110 title => $title,
111 rating => $rating
112 });
fce83e5f 113
55490817 114 # Add a record to the join table for this book, mapping to
d442cc9f 115 # appropriate author
fce83e5f 116 $book->add_to_book_authors({author_id => $author_id});
d442cc9f 117 # Note: Above is a shortcut for this:
fce83e5f 118 # $book->create_related('book_authors', {author_id => $author_id});
0ed3df53 120 # Assign the Book object to the stash for display and set template
121 $c->stash(book => $book,
122 template => 'books/create_done.tt2');
22fe0f18 123
124 # Disable caching for this page
125 $c->response->header('Cache-Control' => 'no-cache');
d442cc9f 126 }
128Notice that Catalyst takes "extra slash-separated information" from the
22fe0f18 129URL and passes it as arguments in C<@_> (as long as the number of
130arguments is not "fixed" using an attribute like C<:Args(0)>). The
131C<url_create> action then uses a simple call to the DBIC C<create>
132method to add the requested information to the database (with a separate
133call to C<add_to_book_authors> to update the join table). As do
134virtually all controller methods (at least the ones that directly handle
135user input), it then sets the template that should handle this request.
137Also note that we are explicitly setting a C<no-cache> "Cache-Control"
138header to force browsers using the page to get a fresh copy every time.
139You could even move this to a C<auto> method in
140C<lib/MyApp/Controller/> and it would automatically get applied
141to every page in the whole application via a single line of code
142(remember from Chapter 3, that every C<auto> method gets run in the
143Controller hierarchy).
d442cc9f 144
8a472b34 146=head2 Include a Template for the 'url_create' Action:
d442cc9f 147
148Edit C<root/src/books/create_done.tt2> and then enter:
150 [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%]
151 [% # Not a good idea for production use, though. :-) 'Indent=1' is -%]
152 [% # optional, but prevents "massive indenting" of deeply nested objects -%]
153 [% USE Dumper(Indent=1) -%]
fce83e5f 154
d442cc9f 155 [% # Set the page title. META can 'go back' and set values in templates -%]
22fe0f18 156 [% # that have been processed 'before' this template (here it's updating -%]
157 [% # the title in the root/src/wrapper.tt2 wrapper template). Note that -%]
158 [% # META only works on simple/static strings (i.e. there is no variable -%]
159 [% # interpolation -- if you need dynamic/interpolated content in your -%]
160 [% # title, set "$c->stash(title => $something)" in the controller). -%]
d442cc9f 161 [% META title = 'Book Created' %]
fce83e5f 162
163 [% # Output information about the record that was added. First title. -%]
d442cc9f 164 <p>Added book '[% book.title %]'
fce83e5f 165
22fe0f18 166 [% # Then, output the last name of the first author -%]
fce83e5f 167 by '[% book.authors.first.last_name %]'
22fe0f18 169 [% # Then, output the rating for the book that was added -%]
d442cc9f 170 with a rating of [% book.rating %].</p>
fce83e5f 171
22fe0f18 172 [% # Provide a link back to the list page. 'c.uri_for' builds -%]
173 [% # a full URI; e.g., 'http://localhost:3000/books/list' -%]
8a7c5151 174 <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
fce83e5f 175
d442cc9f 176 [% # Try out the TT Dumper (for development only!) -%]
177 <pre>
178 Dump of the 'book' variable:
179 [% Dumper.dump(book) %]
180 </pre>
ee53cc71 182The TT C<USE> directive allows access to a variety of plugin modules (TT
183plugins, that is, not Catalyst plugins) to add extra functionality to
184the base TT capabilities. Here, the plugin allows L<Data::Dumper>
185"pretty printing" of objects and variables. Other than that, the rest
186of the code should be familiar from the examples in Chapter 3.
d442cc9f 187
d442cc9f 188
8a472b34 189=head2 Try the 'url_create' Feature
d442cc9f 190
f2bbfc36 191Make sure the development server is running with the "-r" restart
d442cc9f 193
f2bbfc36 194 $ DBIC_TRACE=1 script/ -r
d442cc9f 195
196Note that new path for C</books/url_create> appears in the startup debug
d442cc9f 199Next, use your browser to enter the following URL:
201 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
55490817 203Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by
204'Stevens' with a rating of 5." along with a dump of the new book model
205object as it was returned by DBIC. You should also see the following
ee53cc71 206DBIC debug messages displayed in the development server log messages if
207you have DBIC_TRACE set:
d442cc9f 208
3b1fa91b 209 INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
210 INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6'
d442cc9f 211
212The C<INSERT> statements are obviously adding the book and linking it to
ee53cc71 213the existing record for Richard Stevens. The C<SELECT> statement
214results from DBIC automatically fetching the book for the
d442cc9f 216
ee53cc71 217If you then click the "Return to list" link, you should find that there
218are now six books shown (if necessary, Shift+Reload or Ctrl+Reload your
219browser at the C</books/list> page). You should now see the six DBIC
220debug messages similar to the following (where N=1-6):
3b1fa91b 221
a467a714 222 SELECT, author.first_name, author.last_name
223 FROM book_author me JOIN author author
fce83e5f 224 ON = me.author_id WHERE ( me.book_id = ? ): 'N'
d442cc9f 226
89d3dae9 227=head1 CONVERT TO A CHAINED ACTION
55490817 229Although the example above uses the same C<Local> action type for the
4b4d3884 230method that we saw in the previous chapter of the tutorial, there is an
ee53cc71 231alternate approach that allows us to be more specific while also paving
232the way for more advanced capabilities. Change the method declaration
233for C<url_create> in C<lib/MyApp/Controller/> you entered above
234to match the following:
89d3dae9 235
236 sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
fce83e5f 237 # In addition to self & context, get the title, rating, &
238 # author_id args from the URL. Note that Catalyst automatically
239 # puts the first 3 arguments worth of extra information after the
240 # "/<controller_name>/<action_name/" into @_ because we specified
241 # "Args(3)". The args are separated by the '/' char on the URL.
242 my ($self, $c, $title, $rating, $author_id) = @_;
244 ...
89d3dae9 245
55490817 246This converts the method to take advantage of the Chained
ee53cc71 247action/dispatch type. Chaining lets you have a single URL automatically
248dispatch to several controller methods, each of which can have precise
249control over the number of arguments that it will receive. A chain can
250essentially be thought of having three parts -- a beginning, a middle,
251and an end. The bullets below summarize the key points behind each of
252these parts of a chain:
89d3dae9 253
255=over 4
258=item *
262=over 4
264=item *
266B<Use "C<:Chained('/')>" to start a chain>
268=item *
270Get arguments through C<CaptureArgs()>
272=item *
274Specify the path to match with C<PathPart()>
279=item *
283=over 4
285=item *
d442cc9f 286
89d3dae9 287Link to previous part of the chain with C<:Chained('_name_')>
289=item *
291Get arguments through C<CaptureArgs()>
293=item *
295Specify the path to match with C<PathPart()>
300=item *
304=over 4
306=item *
308Link to previous part of the chain with C<:Chained('_name_')>
310=item *
312B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain>
314=item *
316Specify the path to match with C<PathPart()>
72609296 323In our C<url_create> method above, we have combined all three parts into
324a single method: C<:Chained('/')> to start the chain,
325C<:PathPart('books/url_create')> to specify the base URL to match, and
326C<:Args(3)> to capture exactly three arguments and to end the chain.
89d3dae9 327
55490817 328As we will see shortly, a chain can consist of as many "links" as you
ee53cc71 329wish, with each part capturing some arguments and doing some work along
330the way. We will continue to use the Chained action type in this
4b4d3884 331chapter of the tutorial and explore slightly more advanced capabilities
ee53cc71 332with the base method and delete feature below. But Chained dispatch is
333capable of far more. For additional information, see
55490817 334L<Catalyst::Manual::Intro/Action types>,
ee53cc71 335L<Catalyst::DispatchType::Chained>, and the 2006 Advent calendar entry
336on the subject: L<>.
89d3dae9 337
339=head2 Try the Chained Action
55490817 341If you look back at the development server startup logs from your
ee53cc71 342initial version of the C<url_create> method (the one using the C<:Local>
343attribute), you will notice that it produced output similar to the
89d3dae9 345
fbbb9084 346 [debug] Loaded Path actions:
347 .-------------------------------------+--------------------------------------.
348 | Path | Private |
349 +-------------------------------------+--------------------------------------+
350 | / | /default |
351 | / | /index |
352 | /books | /books/index |
353 | /books/list | /books/list |
354 | /books/url_create | /books/url_create |
355 '-------------------------------------+--------------------------------------'
89d3dae9 356
22fe0f18 357When the development server restarts after our conversion to Chained
358dispatch, the debug output should change to something along the lines of
359the following:
89d3dae9 360
fbbb9084 361 [debug] Loaded Path actions:
362 .-------------------------------------+--------------------------------------.
363 | Path | Private |
364 +-------------------------------------+--------------------------------------+
365 | / | /default |
366 | / | /index |
367 | /books | /books/index |
368 | /books/list | /books/list |
369 '-------------------------------------+--------------------------------------'
fce83e5f 370
fbbb9084 371 [debug] Loaded Chained actions:
372 .-------------------------------------+--------------------------------------.
373 | Path Spec | Private |
374 +-------------------------------------+--------------------------------------+
375 | /books/url_create/*/*/* | /books/url_create |
376 '-------------------------------------+--------------------------------------'
89d3dae9 377
ee53cc71 378C<url_create> has disappeared from the "Loaded Path actions" section but
379it now shows up under the newly created "Loaded Chained actions"
72609296 380section. And the "/*/*/*" portion clearly shows our requirement for
fbbb9084 381three arguments.
89d3dae9 382
55490817 383As with our non-chained version of C<url_create>, use your browser to
89d3dae9 384enter the following URL:
fbbb9084 386 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
89d3dae9 387
55490817 388You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
389'Stevens' with a rating of 5." along with a dump of the new book model
72609296 390object. Click the "Return to list" link, and you should find that there
391are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>).
89d3dae9 392
8a472b34 394=head2 Refactor to Use a 'base' Method to Start the Chains
89d3dae9 395
ee53cc71 396Let's make a quick update to our initial Chained action to show a little
397more of the power of chaining. First, open
89d3dae9 398C<lib/MyApp/Controller/> in your editor and add the following
fbbb9084 401 =head2 base
fce83e5f 402
fbbb9084 403 Can place common logic to start chained dispatch here
fce83e5f 404
fbbb9084 405 =cut
fce83e5f 406
fbbb9084 407 sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
408 my ($self, $c) = @_;
fce83e5f 409
1cde0fd6 410 # Store the ResultSet in stash so it's available for other methods
0ed3df53 411 $c->stash(resultset => $c->model('DB::Book'));
fce83e5f 412
fbbb9084 413 # Print a message to the debug log
414 $c->log->debug('*** INSIDE BASE METHOD ***');
415 }
55490817 417Here we print a log message and store the DBIC ResultSet in
418C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available
419for other actions that chain off C<base>. If your controller always
72609296 420needs a book ID as its first argument, you could have the base method
55490817 421capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
ee53cc71 422book object with C<-E<gt>find($id)> and leave it in the stash for later
423parts of your chains to then act upon. Because we have several actions
424that don't need to retrieve a book (such as the C<url_create> we are
425working with now), we will instead add that functionality to a common
426C<object> action shortly.
994b66ad 427
55490817 428As for C<url_create>, let's modify it to first dispatch to C<base>.
429Open up C<lib/MyApp/Controller/> and edit the declaration for
994b66ad 430C<url_create> to match the following:
89d3dae9 431
432 sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
ee53cc71 434Once you save C<lib/MyApp/Controller/>, notice that the
435development server will restart and our "Loaded Chained actions" section
f2bbfc36 436will changed slightly:
55490817 437
fbbb9084 438 [debug] Loaded Chained actions:
439 .-------------------------------------+--------------------------------------.
440 | Path Spec | Private |
441 +-------------------------------------+--------------------------------------+
442 | /books/url_create/*/*/* | /books/base (0) |
443 | | => /books/url_create |
444 '-------------------------------------+--------------------------------------'
89d3dae9 445
ee53cc71 446The "Path Spec" is the same, but now it maps to two Private actions as
447we would expect. The C<base> method is being triggered by the C</books>
448part of the URL. However, the processing then continues to the
449C<url_create> method because this method "chained" off C<base> and
450specified C<:PathPart('url_create')> (note that we could have omitted
451the "PathPart" here because it matches the name of the method, but we
444d6b27 452will include it to make the logic as explicit as possible).
89d3dae9 453
454Once again, enter the following URL into your browser:
fbbb9084 456 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
89d3dae9 457
ee53cc71 458The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
459rating of 5." message and a dump of the new book object should appear.
460Also notice the extra "INSIDE BASE METHOD" debug message in the
461development server output from the C<base> method. Click the "Return to
462list" link, and you should find that there are now eight books shown.
463(You may have a larger number of books if you repeated any of the
464"create" actions more than once. Don't worry about it as long as the
465number of books is appropriate for the number of times you added new
466books... there should be the original five books added via
467C<myapp01.sql> plus one additional book for each time you ran one of the
468url_create variations above.)
d442cc9f 469
473Although the C<url_create> action in the previous step does begin to
474reveal the power and flexibility of both Catalyst and DBIC, it's
475obviously not a very realistic example of how users should be expected
22fe0f18 476to enter data. This section begins to address that concern (but just
477barely, see L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
478for better options for handling web-based forms).
d442cc9f 479
481=head2 Add Method to Display The Form
483Edit C<lib/MyApp/Controller/> and add the following method:
485 =head2 form_create
fce83e5f 486
d442cc9f 487 Display form to collect information for book to create
fce83e5f 488
d442cc9f 489 =cut
fce83e5f 490
89d3dae9 491 sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
d442cc9f 492 my ($self, $c) = @_;
fce83e5f 493
d442cc9f 494 # Set the TT template to use
0ed3df53 495 $c->stash(template => 'books/form_create.tt2');
d442cc9f 496 }
72609296 498This action simply invokes a view containing a form to create a book.
d442cc9f 499
1390ef0e 500
d442cc9f 501=head2 Add a Template for the Form
503Open C<root/src/books/form_create.tt2> in your editor and enter:
505 [% META title = 'Manual Form Book Create' -%]
444d6b27 506
8a7c5151 507 <form method="post" action="[% c.uri_for('form_create_do') %]">
d442cc9f 508 <table>
509 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
510 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
511 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
512 </table>
513 <input type="submit" name="Submit" value="Submit">
514 </form>
516Note that we have specified the target of the form data as
517C<form_create_do>, the method created in the section that follows.
1390ef0e 519
d442cc9f 520=head2 Add a Method to Process Form Values and Update Database
522Edit C<lib/MyApp/Controller/> and add the following method to
523save the form information to the database:
525 =head2 form_create_do
fce83e5f 526
d442cc9f 527 Take information from form and add to database
fce83e5f 528
d442cc9f 529 =cut
fce83e5f 530
89d3dae9 531 sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
d442cc9f 532 my ($self, $c) = @_;
fce83e5f 533
d442cc9f 534 # Retrieve the values from the form
535 my $title = $c->request->params->{title} || 'N/A';
536 my $rating = $c->request->params->{rating} || 'N/A';
537 my $author_id = $c->request->params->{author_id} || '1';
fce83e5f 538
d442cc9f 539 # Create the book
3b1fa91b 540 my $book = $c->model('DB::Book')->create({
d442cc9f 541 title => $title,
542 rating => $rating,
543 });
544 # Handle relationship with author
fce83e5f 545 $book->add_to_book_authors({author_id => $author_id});
546 # Note: Above is a shortcut for this:
547 # $book->create_related('book_authors', {author_id => $author_id});
0ed3df53 549 # Store new model object in stash and set template
550 $c->stash(book => $book,
551 template => 'books/create_done.tt2');
d442cc9f 552 }
555=head2 Test Out The Form
ee53cc71 557Notice that the server startup log reflects the two new chained methods
558that we added:
89d3dae9 559
fbbb9084 560 [debug] Loaded Chained actions:
561 .-------------------------------------+--------------------------------------.
562 | Path Spec | Private |
563 +-------------------------------------+--------------------------------------+
564 | /books/form_create | /books/base (0) |
565 | | => /books/form_create |
566 | /books/form_create_do | /books/base (0) |
567 | | => /books/form_create_do |
568 | /books/url_create/*/*/* | /books/base (0) |
569 | | => /books/url_create |
570 '-------------------------------------+--------------------------------------'
89d3dae9 571
d442cc9f 572Point your browser to L<http://localhost:3000/books/form_create> and
573enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
1390ef0e 574author ID of 4. You should then see the output of the same
d442cc9f 575C<create_done.tt2> template seen in earlier examples. Finally, click
576"Return to list" to view the full list of books.
578B<Note:> Having the user enter the primary key ID for the author is
fce83e5f 579obviously crude; we will address this concern with a drop-down list and
22fe0f18 580add validation to our forms in
581L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>.
d442cc9f 582
72609296 586Turning our attention to the Delete portion of CRUD, this section
d442cc9f 587illustrates some basic techniques that can be used to remove information
588from the database.
591=head2 Include a Delete Link in the List
ee53cc71 593Edit C<root/src/books/list.tt2> and update it to match the following
594(two sections have changed: 1) the additional '<th>Links</th>' table
22fe0f18 595header, and 2) the five lines for the Delete link near the bottom):
d442cc9f 596
22fe0f18 597 [% # This is a TT comment. -%]
3dba69ab 598
22fe0f18 599 [%- # Provide a title -%]
d442cc9f 600 [% META title = 'Book List' -%]
3dba69ab 601
22fe0f18 602 [% # Note That the '-' at the beginning or end of TT code -%]
603 [% # "chomps" the whitespace/newline at that end of the -%]
604 [% # output (use View Source in browser to see the effect) -%]
3dba69ab 605
22fe0f18 606 [% # Some basic HTML with a loop to display books -%]
d442cc9f 607 <table>
608 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
609 [% # Display each book in a table row %]
610 [% FOREACH book IN books -%]
611 <tr>
612 <td>[% book.title %]</td>
613 <td>[% book.rating %]</td>
614 <td>
22fe0f18 615 [% # NOTE: See Chapter 4 for a better way to do this! -%]
d442cc9f 616 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
617 [% # loop in 'side effect notation' to load just the last names of the -%]
55490817 618 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
d442cc9f 619 [% # a value, so nothing will be printed here. But, if you have something -%]
22fe0f18 620 [% # in TT that does return a value and you don't want it printed, you -%]
6d97b973 621 [% # 1) assign it to a bogus value, or -%]
622 [% # 2) use the CALL keyword to call it and discard the return value. -%]
d442cc9f 623 [% tt_authors = [ ];
fce83e5f 624 tt_authors.push(author.last_name) FOREACH author = book.authors %]
d442cc9f 625 [% # Now use a TT 'virtual method' to display the author count in parens -%]
3b1fa91b 626 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
627 ([% tt_authors.size | html %])
d442cc9f 628 [% # Use another TT vmethod to join & print the names & comma separators -%]
3b1fa91b 629 [% tt_authors.join(', ') | html %]
d442cc9f 630 </td>
631 <td>
632 [% # Add a link to delete a book %]
22fe0f18 633 <a href="[%
634 c.uri_for(c.controller.action_for('delete'), []) %]">Delete</a>
d442cc9f 635 </td>
636 </tr>
637 [% END -%]
638 </table>
55490817 640The additional code is obviously designed to add a new column to the
72609296 641right side of the table with a C<Delete> "button" (for simplicity, links
22fe0f18 642will be used instead of full HTML buttons; but, in practice, anything
643that modifies data should be handled with a form sending a POST
fe01b24f 645
ee53cc71 646Also notice that we are using a more advanced form of C<uri_for> than we
647have seen before. Here we use C<$c-E<gt>controller-E<gt>action_for> to
648automatically generate a URI appropriate for that action based on the
649method we want to link to while inserting the C<> value into the
650appropriate place. Now, if you ever change C<:PathPart('delete')> in
22fe0f18 651your controller method to something like C<:PathPart('kill')>, then your
652links will automatically update without any changes to your .tt2
653template file. As long as the name of your method does not change
654(here, "delete"), then your links will still be correct. There are a
655few shortcuts and options when using C<action_for()>:
0416017e 656
657=over 4
659=item *
ee53cc71 661If you are referring to a method in the current controller, you can use
0416017e 663
664=item *
ee53cc71 666If you are referring to a method in a different controller, you need to
667include that controller's name as an argument to C<controller()>, as in
0416017e 668C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>.
b2ad8bbd 671
55490817 672B<Note:> In practice you should B<never> use a GET request to delete a
673record -- always use POST for actions that will modify data. We are
c5d94181 674doing it here for illustrative and simplicity purposes only.
d442cc9f 675
1390ef0e 676
994b66ad 677=head2 Add a Common Method to Retrieve a Book for the Chain
ee53cc71 679As mentioned earlier, since we have a mixture of actions that operate on
680a single book ID and others that do not, we should not have C<base>
55490817 681capture the book ID, find the corresponding book in the database and
682save it in the stash for later links in the chain. However, just
ee53cc71 683because that logic does not belong in C<base> doesn't mean that we can't
684create another location to centralize the book lookup code. In our
685case, we will create a method called C<object> that will store the
55490817 686specific book in the stash. Chains that always operate on a single
687existing book can chain off this method, but methods such as
ee53cc71 688C<url_create> that don't operate on an existing book can chain directly
689off base.
994b66ad 690
ee53cc71 691To add the C<object> method, edit C<lib/MyApp/Controller/> and
692add the following code:
994b66ad 693
e075db0c 694 =head2 object
fce83e5f 695
e075db0c 696 Fetch the specified book object based on the book ID and store
697 it in the stash
fce83e5f 698
e075db0c 699 =cut
fce83e5f 700
994b66ad 701 sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
fbbb9084 702 # $id = primary key of book to delete
994b66ad 703 my ($self, $c, $id) = @_;
fce83e5f 704
994b66ad 705 # Find the book object and store it in the stash
706 $c->stash(object => $c->stash->{resultset}->find($id));
fce83e5f 707
994b66ad 708 # Make sure the lookup was successful. You would probably
709 # want to do something like this in a real app:
710 # $c->detach('/error_404') if !$c->stash->{object};
711 die "Book $id not found!" if !$c->stash->{object};
fce83e5f 712
713 # Print a message to the debug log
714 $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***");
994b66ad 715 }
ee53cc71 717Now, any other method that chains off C<object> will automatically have
718the appropriate book waiting for it in C<$c-E<gt>stash-E<gt>{object}>.
994b66ad 719
994b66ad 720
d442cc9f 721=head2 Add a Delete Action to the Controller
723Open C<lib/MyApp/Controller/> in your editor and add the
724following method:
1390ef0e 726 =head2 delete
fce83e5f 727
d442cc9f 728 Delete a book
fce83e5f 729
d442cc9f 730 =cut
fce83e5f 731
994b66ad 732 sub delete :Chained('object') :PathPart('delete') :Args(0) {
994b66ad 733 my ($self, $c) = @_;
fce83e5f 734
994b66ad 735 # Use the book object saved by 'object' and delete it along
3b1fa91b 736 # with related 'book_author' entries
994b66ad 737 $c->stash->{object}->delete;
fce83e5f 738
d442cc9f 739 # Set a status message to be displayed at the top of the view
740 $c->stash->{status_msg} = "Book deleted.";
fce83e5f 741
d442cc9f 742 # Forward to the list action/method in this controller
743 $c->forward('list');
744 }
55490817 746This method first deletes the book object saved by the C<object> method.
ee53cc71 747However, it also removes the corresponding entry from the C<book_author>
748table with a cascading delete.
d442cc9f 749
750Then, rather than forwarding to a "delete done" page as we did with the
751earlier create example, it simply sets the C<status_msg> to display a
752notification to the user as the normal list view is rendered.
754The C<delete> action uses the context C<forward> method to return the
755user to the book list. The C<detach> method could have also been used.
756Whereas C<forward> I<returns> to the original action once it is
757completed, C<detach> does I<not> return. Other than that, the two are
761=head2 Try the Delete Feature
ee53cc71 763Once you save the Books controller, the server should automatically
764restart. The C<delete> method should now appear in the "Loaded Chained
765actions" section of the startup debug output:
89d3dae9 766
fbbb9084 767 [debug] Loaded Chained actions:
994b66ad 768 .-------------------------------------+--------------------------------------.
769 | Path Spec | Private |
770 +-------------------------------------+--------------------------------------+
771 | /books/id/*/delete | /books/base (0) |
772 | | -> /books/object (1) |
773 | | => /books/delete |
774 | /books/form_create | /books/base (0) |
775 | | => /books/form_create |
776 | /books/form_create_do | /books/base (0) |
777 | | => /books/form_create_do |
778 | /books/url_create/*/*/* | /books/base (0) |
779 | | => /books/url_create |
780 '-------------------------------------+--------------------------------------'
89d3dae9 781
d442cc9f 782Then point your browser to L<http://localhost:3000/books/list> and click
55490817 783the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green
784"Book deleted" status message should display at the top of the page,
994b66ad 785along with a list of the eight remaining books. You will also see the
786cascading delete operation via the DBIC_TRACE output:
3b1fa91b 788 SELECT, me.title, me.rating FROM book me WHERE ( ( = ? ) ): '6'
789 DELETE FROM book WHERE ( id = ? ): '6'
d442cc9f 790
792=head2 Fixing a Dangerous URL
55490817 794Note the URL in your browser once you have performed the deletion in the
d442cc9f 795prior step -- it is still referencing the delete action:
acbd7bdd 797 http://localhost:3000/books/id/6/delete
d442cc9f 798
55490817 799What if the user were to press reload with this URL still active? In
ee53cc71 800this case the redundant delete is harmless (although it does generate an
801exception screen, it doesn't perform any undesirable actions on the
22fe0f18 802application or database), but in other cases this could clearly lead to
d442cc9f 804
805We can improve the logic by converting to a redirect. Unlike
ee53cc71 806C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform a
807server-side alteration in the flow of processing, a redirect is a
808client-side mechanism that causes the browser to issue an entirely new
809request. As a result, the URL in the browser is updated to match the
810destination of the redirection URL.
d442cc9f 811
ee53cc71 812To convert the forward used in the previous section to a redirect, open
813C<lib/MyApp/Controller/> and edit the existing C<sub delete>
814method to match:
d442cc9f 815
994b66ad 816 =head2 delete
fce83e5f 817
d442cc9f 818 Delete a book
fce83e5f 819
d442cc9f 820 =cut
fce83e5f 821
994b66ad 822 sub delete :Chained('object') :PathPart('delete') :Args(0) {
fbbb9084 823 my ($self, $c) = @_;
fce83e5f 824
994b66ad 825 # Use the book object saved by 'object' and delete it along
3b1fa91b 826 # with related 'book_author' entries
994b66ad 827 $c->stash->{object}->delete;
fce83e5f 828
d442cc9f 829 # Set a status message to be displayed at the top of the view
830 $c->stash->{status_msg} = "Book deleted.";
fce83e5f 831
0416017e 832 # Redirect the user back to the list page. Note the use
833 # of $self->action_for as earlier in this section (BasicCRUD)
fbbb9084 834 $c->response->redirect($c->uri_for($self->action_for('list')));
d442cc9f 835 }
838=head2 Try the Delete and Redirect Logic
ee53cc71 840Point your browser to L<http://localhost:3000/books/list> (don't just
841hit "Refresh" in your browser since we left the URL in an invalid state
842in the previous section!) and delete the first copy of the remaining two
843"TCPIP_Illustrated_Vol-2" books. The URL in your browser should return
844to the L<http://localhost:3000/books/list> URL, so that is an
845improvement, but notice that I<no green "Book deleted" status message is
846displayed>. Because the stash is reset on every request (and a redirect
847involves a second request), the C<status_msg> is cleared before it can
22fe0f18 848be displayed.
d442cc9f 849
8a472b34 851=head2 Using 'uri_for' to Pass Query Parameters
d442cc9f 852
ee53cc71 853There are several ways to pass information across a redirect. One option
22fe0f18 854is to use the C<flash> technique that we will see in
855L<Chapter 5|Catalyst::Manual::Tutorial::05_Authentication> of this
ee53cc71 856tutorial; however, here we will pass the information via query
857parameters on the redirect itself. Open
858C<lib/MyApp/Controller/> and update the existing C<sub delete>
89d3dae9 859method to match the following:
d442cc9f 860
55490817 861 =head2 delete
fce83e5f 862
d442cc9f 863 Delete a book
fce83e5f 864
d442cc9f 865 =cut
fce83e5f 866
994b66ad 867 sub delete :Chained('object') :PathPart('delete') :Args(0) {
fbbb9084 868 my ($self, $c) = @_;
fce83e5f 869
994b66ad 870 # Use the book object saved by 'object' and delete it along
3b1fa91b 871 # with related 'book_author' entries
994b66ad 872 $c->stash->{object}->delete;
fce83e5f 873
d442cc9f 874 # Redirect the user back to the list page with status msg as an arg
55490817 875 $c->response->redirect($c->uri_for($self->action_for('list'),
d442cc9f 876 {status_msg => "Book deleted."}));
877 }
879This modification simply leverages the ability of C<uri_for> to include
55490817 880an arbitrary number of name/value pairs in a hash reference. Next, we
881need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a
d442cc9f 882query parameter:
1390ef0e 884 ...
d442cc9f 885 <div id="content">
1390ef0e 886 [%# Status and error messages %]
ee53cc71 887 <span class="message">[%
888 status_msg || c.request.params.status_msg | html %]</span>
1390ef0e 889 <span class="error">[% error_msg %]</span>
890 [%# This is where TT will stick all of your template's contents. -%]
891 [% content %]
892 </div><!-- end content -->
893 ...
ee53cc71 895Although the sample above only shows the C<content> div, leave the rest
896of the file intact -- the only change we made to the C<wrapper.tt2> was
22fe0f18 897to add "C<|| c.request.params.status_msg>" to the
b3876d9e 898C<E<lt>span class="message"E<gt>> line. Note that we definitely want
899the "C<| html>" TT filter here since it would be easy for users to
900modify the message on the URL and possibly inject harmful code into the
901application if we left that off.
d442cc9f 902
904=head2 Try the Delete and Redirect With Query Param Logic
ee53cc71 906Point your browser to L<http://localhost:3000/books/list> (you should
907now be able to safely hit "refresh" in your browser). Then delete the
908remaining copy of "TCPIP_Illustrated_Vol-2". The green "Book deleted"
a608d8ce 909status message should return. But notice that you can now hit the
ee53cc71 910"Reload" button in your browser and it just redisplays the book list
911(and it correctly shows it without the "Book deleted" message on
d442cc9f 913
22fe0f18 914B<NOTE:> Be sure to check out
915L<Authentication|Catalyst::Manual::Tutorial::05_Authentication> where we
916use an improved technique that is better suited to your real world
d442cc9f 918
1cde0fd6 920=head1 EXPLORING THE POWER OF DBIC
ee53cc71 922In this section we will explore some additional capabilities offered by
22fe0f18 923L<DBIx::Class>. Although these features have relatively little to do
924with Catalyst per se, you will almost certainly want to take advantage
925of them in your applications.
1cde0fd6 926
1cde0fd6 928=head2 Add Datetime Columns to Our Existing Books Table
ee53cc71 930Let's add two columns to our existing C<books> table to track when each
931book was added and when each book is updated:
1cde0fd6 932
933 $ sqlite3 myapp.db
33f1d5d0 934 sqlite> ALTER TABLE book ADD created TIMESTAMP;
935 sqlite> ALTER TABLE book ADD updated TIMESTAMP;
3b1fa91b 936 sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
937 sqlite> SELECT * FROM book;
f2bbfc36 938 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
939 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
940 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
941 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
942 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
943 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1cde0fd6 944 sqlite> .quit
945 $
d5d7ee98 947Here are the commands without the surrounding sqlite3 prompt and output
948in case you want to cut and paste them as a single block (but still
949start sqlite3 before you paste these in):
953 UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
954 SELECT * FROM book;
ee53cc71 956This will modify the C<books> table to include the two new fields and
957populate those fields with the current time.
1cde0fd6 958
acbd7bdd 959
a46b474e 960=head2 Update DBIx::Class to Automatically Handle the Datetime Columns
1cde0fd6 961
ee53cc71 962Next, we should re-run the DBIC helper to update the Result Classes with
963the new fields:
1cde0fd6 964
965 $ script/ model DB DBIC::Schema MyApp::Schema \
b66dd084 966 create=static components=TimeStamp dbi:SQLite:myapp.db \
967 on_connect_do="PRAGMA foreign_keys = ON"
1cde0fd6 968 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
969 exists "/root/dev/MyApp/script/../t"
970 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
971 Schema dump completed.
972 exists "/root/dev/MyApp/script/../lib/MyApp/Model/"
ee53cc71 974Notice that we modified our use of the helper slightly: we told it to
975include the L<DBIx::Class::TimeStamp> in the C<load_components> line of
976the Result Classes.
1cde0fd6 977
ee53cc71 978If you open C<lib/MyApp/Schema/Result/> in your editor you should
979see that the C<created> and C<updated> fields are now included in the
980call to C<add_columns()>. However, also notice that the C<many_to_many>
981relationships we manually added below the "C<# DO NOT MODIFY...>" line
982were automatically preserved.
1cde0fd6 983
d5d7ee98 984While we C<lib/MyApp/Schema/Result/> open, let's update it with
985some additional information to have DBIC automatically handle the
986updating of these two fields for us. Insert the following code at the
987bottom of the file (it B<must> be B<below> the "C<# DO NOT MODIFY...>"
988line and B<above> the C<1;> on the last line):
1cde0fd6 989
990 #
991 # Enable automatic date handling
992 #
993 __PACKAGE__->add_columns(
994 "created",
33f1d5d0 995 { data_type => 'timestamp', set_on_create => 1 },
1cde0fd6 996 "updated",
33f1d5d0 997 { data_type => 'timestamp', set_on_create => 1, set_on_update => 1 },
55490817 998 );
1cde0fd6 999
ee53cc71 1000This will override the definition for these fields that Schema::Loader
1001placed at the top of the file. The C<set_on_create> and
1002C<set_on_update> options will cause DBIx::Class to automatically update
1003the timestamps in these columns whenever a row is created or modified.
1cde0fd6 1004
22fe0f18 1005B<Note> that adding the lines above will cause the development server to
1006automatically restart if you are running it with the "-r" option. In
1007other words, the development server is smart enough to restart not only
1008for code under the C<MyApp/Controller/>, C<MyApp/Model/>, and
1009C<MyApp/View/> directories, but also under other directions such as our
1010"external DBIC model" in C<MyApp/Schema/>. However, also note that it's
1011smart enough to B<not> restart when you edit your C<.tt2> files under
1cde0fd6 1014Then enter the following URL into your web browser:
1016 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
22fe0f18 1018You should get the same "Book Created" screen we saw earlier. However, if
ee53cc71 1019you now use the sqlite3 command-line tool to dump the C<books> table,
1020you will see that the new book we added has an appropriate date and time
1021entered for it (see the last line in the listing below):
1cde0fd6 1022
444d6b27 1023 $ sqlite3 myapp.db "select * from book"
f2bbfc36 1024 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1025 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1026 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
1027 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1028 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1029 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1030 10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42
1cde0fd6 1031
55490817 1032Notice in the debug log that the SQL DBIC generated has changed to
1cde0fd6 1033incorporate the datetime logic:
2a6eb5f9 1035 INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ):
f2bbfc36 1036 '2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42'
2a6eb5f9 1037 INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10'
1cde0fd6 1038
1040=head2 Create a ResultSet Class
444d6b27 1042An often overlooked but extremely powerful features of DBIC is that it
55490817 1043allows you to supply your own subclasses of C<DBIx::Class::ResultSet>.
22fe0f18 1044This can be used to pull complex and unsightly "query code" out of your
1cde0fd6 1045controllers and encapsulate it in a method of your ResultSet Class.
ee53cc71 1046These "canned queries" in your ResultSet Class can then be invoked via a
1047single call, resulting in much cleaner and easier to read controller
22fe0f18 1048code (or View code, if that's where you want to call it).
1cde0fd6 1049
55490817 1050To illustrate the concept with a fairly simple example, let's create a
ee53cc71 1051method that returns books added in the last 10 minutes. Start by making
1052a directory where DBIx::Class will look for our ResultSet Class:
1cde0fd6 1053
444d6b27 1054 $ mkdir lib/MyApp/Schema/ResultSet
1cde0fd6 1055
3b1fa91b 1056Then open C<lib/MyApp/Schema/ResultSet/> and enter the following:
1cde0fd6 1057
3b1fa91b 1058 package MyApp::Schema::ResultSet::Book;
fce83e5f 1059
1cde0fd6 1060 use strict;
1061 use warnings;
1062 use base 'DBIx::Class::ResultSet';
fce83e5f 1063
1cde0fd6 1064 =head2 created_after
fce83e5f 1065
1cde0fd6 1066 A predefined search for recently added books
fce83e5f 1067
1cde0fd6 1068 =cut
fce83e5f 1069
1cde0fd6 1070 sub created_after {
fadc4ae7 1071 my ($self, $datetime) = @_;
fce83e5f 1072
b66dd084 1073 my $date_str = $self->result_source->schema->storage
fadc4ae7 1074 ->datetime_parser->format_datetime($datetime);
fce83e5f 1075
fadc4ae7 1076 return $self->search({
1077 created => { '>' => $date_str }
1078 });
1cde0fd6 1079 }
fce83e5f 1080
1cde0fd6 1081 1;
1cde0fd6 1083Then add the following method to the C<lib/MyApp/Controller/>:
1085 =head2 list_recent
fce83e5f 1086
1cde0fd6 1087 List recently created books
fce83e5f 1088
1cde0fd6 1089 =cut
fce83e5f 1090
1cde0fd6 1091 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
1092 my ($self, $c, $mins) = @_;
fce83e5f 1093
1cde0fd6 1094 # Retrieve all of the book records as book model objects and store in the
1095 # stash where they can be accessed by the TT template, but only
1096 # retrieve books created within the last $min number of minutes
0ed3df53 1097 $c->stash(books => [$c->model('DB::Book')
1098 ->created_after(DateTime->now->subtract(minutes => $mins))]);
fce83e5f 1099
1cde0fd6 1100 # Set the TT template to use. You will almost always want to do this
1101 # in your action methods (action methods respond to user input in
1102 # your controllers).
0ed3df53 1103 $c->stash(template => 'books/list.tt2');
1cde0fd6 1104 }
ee53cc71 1106Now try different values for the "minutes" argument (the final number
1107value) using the URL C<http://localhost:3000/books/list_recent/_#_> in
1108your browser. For example, this would list all books added in the last
1109fifteen minutes:
1cde0fd6 1110
1111 http://localhost:3000/books/list_recent/15
ee53cc71 1113Depending on how recently you added books, you might want to try a
1114higher or lower value for the minutes.
1cde0fd6 1115
1117=head2 Chaining ResultSets
22fe0f18 1119One of the most helpful and powerful features in C<DBIx::Class> is that
1120it allows you to "chain together" a series of queries (note that this
1121has nothing to do with the "Chained Dispatch" for Catalyst that we were
1122discussing earlier). Because each ResultSet method returns another
1123ResultSet, you can take an initial query and immediately feed that into
1124a second query (and so on for as many queries you need). Note that no
1125matter how many ResultSets you chain together, the database itself will
1126not be hit until you use a method that attempts to access the data. And,
1127because this technique carries over to the ResultSet Class feature we
ee53cc71 1128implemented in the previous section for our "canned search", we can
1129combine the two capabilities. For example, let's add an action to our
1130C<Books> controller that lists books that are both recent I<and> have
1131"TCP" in the title. Open up C<lib/MyApp/Controller/> and add
1132the following method:
1cde0fd6 1133
acbd7bdd 1134 =head2 list_recent_tcp
fce83e5f 1135
1cde0fd6 1136 List recently created books
fce83e5f 1137
1cde0fd6 1138 =cut
fce83e5f 1139
1cde0fd6 1140 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1141 my ($self, $c, $mins) = @_;
fce83e5f 1142
1cde0fd6 1143 # Retrieve all of the book records as book model objects and store in the
1144 # stash where they can be accessed by the TT template, but only
1145 # retrieve books created within the last $min number of minutes
1146 # AND that have 'TCP' in the title
22fe0f18 1147 $c->stash(books => [
1148 $c->model('DB::Book')
1149 ->created_after(DateTime->now->subtract(minutes => $mins))
1150 ->search({title => {'like', '%TCP%'}})
1151 ]);
fce83e5f 1152
1cde0fd6 1153 # Set the TT template to use. You will almost always want to do this
1154 # in your action methods (action methods respond to user input in
1155 # your controllers).
0ed3df53 1156 $c->stash(template => 'books/list.tt2');
1cde0fd6 1157 }
f2bbfc36 1159To try this out, enter the following URL into your browser:
1cde0fd6 1160
1161 http://localhost:3000/books/list_recent_tcp/100
55490817 1163And you should get a list of books added in the last 100 minutes that
1164contain the string "TCP" in the title. However, if you look at all
ee53cc71 1165books within the last 100 minutes, you should get a longer list (again,
1166you might have to adjust the number of minutes depending on how recently
1167you added books to your database):
1cde0fd6 1168
1169 http://localhost:3000/books/list_recent/100
55490817 1171Take a look at the DBIC_TRACE output in the development server log for
1cde0fd6 1172the first URL and you should see something similar to the following:
fce83e5f 1174 SELECT, me.title, me.rating, me.created, me.updated FROM book me
f2bbfc36 1175 WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32'
1cde0fd6 1176
ee53cc71 1177However, let's not pollute our controller code with this raw "TCP" query
1178-- it would be cleaner to encapsulate that code in a method on our
1179ResultSet Class. To do this, open C<lib/MyApp/Schema/ResultSet/>
1180and add the following method:
1cde0fd6 1181
1182 =head2 title_like
fce83e5f 1183
1cde0fd6 1184 A predefined search for books with a 'LIKE' search in the string
fce83e5f 1185
1cde0fd6 1186 =cut
fce83e5f 1187
1cde0fd6 1188 sub title_like {
fadc4ae7 1189 my ($self, $title_str) = @_;
fce83e5f 1190
fadc4ae7 1191 return $self->search({
1192 title => { 'like' => "%$title_str%" }
1193 });
1cde0fd6 1194 }
55490817 1196We defined the search string as C<$title_str> to make the method more
1197flexible. Now update the C<list_recent_tcp> method in
1198C<lib/MyApp/Controller/> to match the following (we have
1199replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line
1cde0fd6 1200shown here -- the rest of the method should be the same):
1202 =head2 list_recent_tcp
fce83e5f 1203
1cde0fd6 1204 List recently created books
fce83e5f 1205
1cde0fd6 1206 =cut
fce83e5f 1207
1cde0fd6 1208 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1209 my ($self, $c, $mins) = @_;
fce83e5f 1210
1cde0fd6 1211 # Retrieve all of the book records as book model objects and store in the
1212 # stash where they can be accessed by the TT template, but only
1213 # retrieve books created within the last $min number of minutes
1214 # AND that have 'TCP' in the title
22fe0f18 1215 $c->stash(books => [
1216 $c->model('DB::Book')
1217 ->created_after(DateTime->now->subtract(minutes => $mins))
1218 ->title_like('TCP')
1219 ]);
fce83e5f 1220
1cde0fd6 1221 # Set the TT template to use. You will almost always want to do this
1222 # in your action methods (action methods respond to user input in
1223 # your controllers).
0ed3df53 1224 $c->stash(template => 'books/list.tt2');
1cde0fd6 1225 }
ee53cc71 1227Try out the C<list_recent_tcp> and C<list_recent> URLs as we did above.
1228They should work just the same, but our code is obviously cleaner and
1229more modular, while also being more flexible at the same time.
1cde0fd6 1230
1232=head2 Adding Methods to Result Classes
ee53cc71 1234In the previous two sections we saw a good example of how we could use
1235DBIx::Class ResultSet Classes to clean up our code for an entire query
1236(for example, our "canned searches" that filtered the entire query). We
1237can do a similar improvement when working with individual rows as well.
1238Whereas the ResultSet construct is used in DBIC to correspond to an
1239entire query, the Result Class construct is used to represent a row.
1240Therefore, we can add row-specific "helper methods" to our Result
1241Classes stored in C<lib/MyApp/Schema/Result/>. For example, open
1242C<lib/MyApp/Schema/Result/> and add the following method (as
a46b474e 1243always, it must be above the closing "C<1;>"):
1cde0fd6 1244
1245 #
a608d8ce 1246 # Row-level helper methods
1cde0fd6 1247 #
1248 sub full_name {
1249 my ($self) = @_;
fce83e5f 1250
1cde0fd6 1251 return $self->first_name . ' ' . $self->last_name;
1252 }
ee53cc71 1254This will allow us to conveniently retrieve both the first and last name
1255for an author in one shot. Now open C<root/src/books/list.tt2> and
1256change the definition of C<tt_authors> from this:
1cde0fd6 1257
acbd7bdd 1258 ...
1cde0fd6 1259 [% tt_authors = [ ];
fce83e5f 1260 tt_authors.push(author.last_name) FOREACH author = book.authors %]
acbd7bdd 1261 ...
1cde0fd6 1262
acbd7bdd 1265 ...
1cde0fd6 1266 [% tt_authors = [ ];
fce83e5f 1267 tt_authors.push(author.full_name) FOREACH author = book.authors %]
acbd7bdd 1268 ...
1cde0fd6 1269
ee53cc71 1270(Only C<author.last_name> was changed to C<author.full_name> -- the rest
1271of the file should remain the same.)
1cde0fd6 1272
f2bbfc36 1273Now go to the standard book list URL:
1cde0fd6 1274
1275 http://localhost:3000/books/list
55490817 1277The "Author(s)" column will now contain both the first and last name.
ee53cc71 1278And, because the concatenation logic was encapsulated inside our Result
1279Class, it keeps the code inside our TT template nice and clean
55490817 1280(remember, we want the templates to be as close to pure HTML markup as
1281possible). Obviously, this capability becomes even more useful as you
0ed0d69a 1282use it to remove even more complicated row-specific logic from your
1cde0fd6 1283templates!
fce83e5f 1286=head2 Moving Complicated View Code to the Model
ee53cc71 1288The previous section illustrated how we could use a Result Class method
1289to print the full names of the authors without adding any extra code to
1290our view, but it still left us with a fairly ugly mess (see
fce83e5f 1291C<root/src/books/list.tt2>):
1293 ...
1294 <td>
1295 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1296 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1297 [% # loop in 'side effect notation' to load just the last names of the -%]
1298 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1299 [% # a value, so nothing will be printed here. But, if you have something -%]
1300 [% # in TT that does return a method and you don't want it printed, you -%]
1301 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1302 [% # call it and discard the return value. -%]
1303 [% tt_authors = [ ];
1304 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1305 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1306 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1307 ([% tt_authors.size | html %])
1308 [% # Use another TT vmethod to join & print the names & comma separators -%]
1309 [% tt_authors.join(', ') | html %]
1310 </td>
1311 ...
ee53cc71 1313Let's combine some of the techniques used earlier in this section to
1314clean this up. First, let's add a method to our Book Result Class to
1315return the number of authors for a book. Open
fce83e5f 1316C<lib/MyApp/Schema/Result/> and add the following method:
444d6b27 1318 =head2 author_count
1320 Return the number of authors for the current book
fce83e5f 1322 =cut
1324 sub author_count {
1325 my ($self) = @_;
1327 # Use the 'many_to_many' relationship to fetch all of the authors for the current
1328 # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT
1329 return $self->authors->count;
1330 }
1332Next, let's add a method to return a list of authors for a book to the
1333same C<lib/MyApp/Schema/Result/> file:
1335 =head2 author_list
1337 Return a comma-separated list of authors for the current book
1339 =cut
1341 sub author_list {
1342 my ($self) = @_;
1344 # Loop through all authors for the current book, calling all the 'full_name'
1345 # Result Class method for each
1346 my @names;
1347 foreach my $author ($self->authors) {
1348 push(@names, $author->full_name);
1349 }
1351 return join(', ', @names);
1352 }
ee53cc71 1354This method loops through each author, using the C<full_name> Result
1355Class method we added to C<lib/MyApp/Schema/Result/> in the
fce83e5f 1356prior section.
1358Using these two methods, we can simplify our TT code. Open
1359C<root/src/books/list.tt2> and update the "Author(s)" table cell to
1360match the following:
1362 ...
1363 <td>
1364 [% # Print count and author list using Result Class methods -%]
1365 ([% book.author_count | html %]) [% book.author_list | html %]
1366 </td>
1367 ...
ee53cc71 1369Although most of the code we removed comprised comments, the overall
1370effect is dramatic... because our view code is so simple, we don't need
22fe0f18 1371huge comments to clue people in to the gist of our code. The view code
ee53cc71 1372is now self-documenting and readable enough that you could probably get
22fe0f18 1373by with no comments at all. All of the "complex" work is being done in
ee53cc71 1374our Result Class methods (and, because we have broken the code into
1375nice, modular chunks, the Result Class code is hardly something you
f2bbfc36 1376would call complex).
fce83e5f 1377
ee53cc71 1378As we saw in this section, always strive to keep your view AND
1379controller code as simple as possible by pulling code out into your
22fe0f18 1380model objects. Because L<DBIx::Class> can be easily extended in so many
ee53cc71 1381ways, it's an excellent to way accomplish this objective. It will make
1382your code cleaner, easier to write, less error-prone, and easier to
1383debug and maintain.
fce83e5f 1384
ee53cc71 1385Before you conclude this section, hit Refresh in your browser... the
1386output should be the same even though the backend code has been trimmed
444d6b27 1388
fce83e5f 1389
d442cc9f 1390=head1 AUTHOR
1392Kennedy Clark, C<>
53243324 1394Feel free to contact the author for any errors or suggestions, but the
1395best way to report issues is via the CPAN RT Bug system at
1398The most recent version of the Catalyst Tutorial can be found at
59884771 1399L<>.
d442cc9f 1400
ec3ef4ad 1401Copyright 2006-2010, Kennedy Clark, under the
1402Creative Commons Attribution Share-Alike License Version 3.0
95674086 1403(L<>).