various formatting cleanups
[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
477a6d5b 78Source code for the tutorial in included in the F</home/catalyst/Final>
79directory of the Tutorial Virtual machine (one subdirectory per
80chapter). There are also instructions for downloading the code in
2217b252 81L<Catalyst::Manual::Tutorial::01_Intro>.
d442cc9f 82
3533daff 83
d442cc9f 84=head1 FORMLESS SUBMISSION
ee53cc71 86Our initial attempt at object creation will utilize the "URL arguments"
22fe0f18 87feature of Catalyst (we will employ the more common form-based
ee53cc71 88submission in the sections that follow).
d442cc9f 89
91=head2 Include a Create Action in the Books Controller
f4e9de4a 93Edit F<lib/MyApp/Controller/> and enter the following method:
d442cc9f 94
95 =head2 url_create
7ce05098 96
d442cc9f 97 Create a book with the supplied title, rating, and author
7ce05098 98
d442cc9f 99 =cut
7ce05098 100
f2bbfc36 101 sub url_create :Local {
55490817 102 # In addition to self & context, get the title, rating, &
103 # author_id args from the URL. Note that Catalyst automatically
104 # puts extra information after the "/<controller_name>/<action_name/"
fce83e5f 105 # into @_. The args are separated by the '/' char on the URL.
d442cc9f 106 my ($self, $c, $title, $rating, $author_id) = @_;
7ce05098 107
55490817 108 # Call create() on the book model object. Pass the table
d442cc9f 109 # columns/field values we want to set as hash values
3b1fa91b 110 my $book = $c->model('DB::Book')->create({
d442cc9f 111 title => $title,
112 rating => $rating
113 });
7ce05098 114
55490817 115 # Add a record to the join table for this book, mapping to
d442cc9f 116 # appropriate author
fce83e5f 117 $book->add_to_book_authors({author_id => $author_id});
d442cc9f 118 # Note: Above is a shortcut for this:
fce83e5f 119 # $book->create_related('book_authors', {author_id => $author_id});
7ce05098 120
0ed3df53 121 # Assign the Book object to the stash for display and set template
122 $c->stash(book => $book,
123 template => 'books/create_done.tt2');
7ce05098 124
22fe0f18 125 # Disable caching for this page
126 $c->response->header('Cache-Control' => 'no-cache');
d442cc9f 127 }
129Notice that Catalyst takes "extra slash-separated information" from the
22fe0f18 130URL and passes it as arguments in C<@_> (as long as the number of
131arguments is not "fixed" using an attribute like C<:Args(0)>). The
132C<url_create> action then uses a simple call to the DBIC C<create>
133method to add the requested information to the database (with a separate
134call to C<add_to_book_authors> to update the join table). As do
135virtually all controller methods (at least the ones that directly handle
136user input), it then sets the template that should handle this request.
138Also note that we are explicitly setting a C<no-cache> "Cache-Control"
139header to force browsers using the page to get a fresh copy every time.
140You could even move this to a C<auto> method in
f4e9de4a 141F<lib/MyApp/Controller/> and it would automatically get applied
22fe0f18 142to every page in the whole application via a single line of code
143(remember from Chapter 3, that every C<auto> method gets run in the
144Controller hierarchy).
d442cc9f 145
8a472b34 147=head2 Include a Template for the 'url_create' Action:
d442cc9f 148
f4e9de4a 149Edit F<root/src/books/create_done.tt2> and then enter:
d442cc9f 150
151 [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%]
152 [% # Not a good idea for production use, though. :-) 'Indent=1' is -%]
153 [% # optional, but prevents "massive indenting" of deeply nested objects -%]
154 [% USE Dumper(Indent=1) -%]
7ce05098 155
d442cc9f 156 [% # Set the page title. META can 'go back' and set values in templates -%]
22fe0f18 157 [% # that have been processed 'before' this template (here it's updating -%]
158 [% # the title in the root/src/wrapper.tt2 wrapper template). Note that -%]
159 [% # META only works on simple/static strings (i.e. there is no variable -%]
160 [% # interpolation -- if you need dynamic/interpolated content in your -%]
161 [% # title, set "$c->stash(title => $something)" in the controller). -%]
d442cc9f 162 [% META title = 'Book Created' %]
7ce05098 163
fce83e5f 164 [% # Output information about the record that was added. First title. -%]
d442cc9f 165 <p>Added book '[% book.title %]'
7ce05098 166
22fe0f18 167 [% # Then, output the last name of the first author -%]
fce83e5f 168 by '[% book.authors.first.last_name %]'
7ce05098 169
22fe0f18 170 [% # Then, output the rating for the book that was added -%]
d442cc9f 171 with a rating of [% book.rating %].</p>
7ce05098 172
22fe0f18 173 [% # Provide a link back to the list page. 'c.uri_for' builds -%]
174 [% # a full URI; e.g., 'http://localhost:3000/books/list' -%]
8a7c5151 175 <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
7ce05098 176
d442cc9f 177 [% # Try out the TT Dumper (for development only!) -%]
178 <pre>
179 Dump of the 'book' variable:
180 [% Dumper.dump(book) %]
181 </pre>
ee53cc71 183The TT C<USE> directive allows access to a variety of plugin modules (TT
184plugins, that is, not Catalyst plugins) to add extra functionality to
185the base TT capabilities. Here, the plugin allows L<Data::Dumper>
186"pretty printing" of objects and variables. Other than that, the rest
187of the code should be familiar from the examples in Chapter 3.
d442cc9f 188
d442cc9f 189
8a472b34 190=head2 Try the 'url_create' Feature
d442cc9f 191
f2bbfc36 192Make sure the development server is running with the "-r" restart
d442cc9f 194
f2bbfc36 195 $ DBIC_TRACE=1 script/ -r
d442cc9f 196
197Note that new path for C</books/url_create> appears in the startup debug
d442cc9f 200Next, use your browser to enter the following URL:
202 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
55490817 204Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by
205'Stevens' with a rating of 5." along with a dump of the new book model
206object as it was returned by DBIC. You should also see the following
ee53cc71 207DBIC debug messages displayed in the development server log messages if
208you have DBIC_TRACE set:
d442cc9f 209
3b1fa91b 210 INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
211 INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6'
d442cc9f 212
213The C<INSERT> statements are obviously adding the book and linking it to
ee53cc71 214the existing record for Richard Stevens. The C<SELECT> statement
215results from DBIC automatically fetching the book for the
d442cc9f 217
ee53cc71 218If you then click the "Return to list" link, you should find that there
219are now six books shown (if necessary, Shift+Reload or Ctrl+Reload your
220browser at the C</books/list> page). You should now see the six DBIC
221debug messages similar to the following (where N=1-6):
3b1fa91b 222
7ce05098 223 SELECT, author.first_name, author.last_name
224 FROM book_author me JOIN author author
fce83e5f 225 ON = me.author_id WHERE ( me.book_id = ? ): 'N'
d442cc9f 227
89d3dae9 228=head1 CONVERT TO A CHAINED ACTION
55490817 230Although the example above uses the same C<Local> action type for the
4b4d3884 231method that we saw in the previous chapter of the tutorial, there is an
ee53cc71 232alternate approach that allows us to be more specific while also paving
233the way for more advanced capabilities. Change the method declaration
f4e9de4a 234for C<url_create> in F<lib/MyApp/Controller/> you entered above
ee53cc71 235to match the following:
89d3dae9 236
237 sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
fce83e5f 238 # In addition to self & context, get the title, rating, &
239 # author_id args from the URL. Note that Catalyst automatically
7ce05098 240 # puts the first 3 arguments worth of extra information after the
fce83e5f 241 # "/<controller_name>/<action_name/" into @_ because we specified
242 # "Args(3)". The args are separated by the '/' char on the URL.
243 my ($self, $c, $title, $rating, $author_id) = @_;
7ce05098 244
fce83e5f 245 ...
89d3dae9 246
55490817 247This converts the method to take advantage of the Chained
ee53cc71 248action/dispatch type. Chaining lets you have a single URL automatically
249dispatch to several controller methods, each of which can have precise
250control over the number of arguments that it will receive. A chain can
251essentially be thought of having three parts -- a beginning, a middle,
252and an end. The bullets below summarize the key points behind each of
253these parts of a chain:
89d3dae9 254
256=over 4
259=item *
263=over 4
265=item *
267B<Use "C<:Chained('/')>" to start a chain>
269=item *
271Get arguments through C<CaptureArgs()>
273=item *
275Specify the path to match with C<PathPart()>
280=item *
284=over 4
286=item *
d442cc9f 287
89d3dae9 288Link to previous part of the chain with C<:Chained('_name_')>
290=item *
292Get arguments through C<CaptureArgs()>
294=item *
296Specify the path to match with C<PathPart()>
301=item *
305=over 4
307=item *
309Link to previous part of the chain with C<:Chained('_name_')>
311=item *
e8200f38 313B<< Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain >>
89d3dae9 314
315=item *
317Specify the path to match with C<PathPart()>
72609296 324In our C<url_create> method above, we have combined all three parts into
325a single method: C<:Chained('/')> to start the chain,
326C<:PathPart('books/url_create')> to specify the base URL to match, and
327C<:Args(3)> to capture exactly three arguments and to end the chain.
89d3dae9 328
55490817 329As we will see shortly, a chain can consist of as many "links" as you
ee53cc71 330wish, with each part capturing some arguments and doing some work along
331the way. We will continue to use the Chained action type in this
4b4d3884 332chapter of the tutorial and explore slightly more advanced capabilities
ee53cc71 333with the base method and delete feature below. But Chained dispatch is
334capable of far more. For additional information, see
55490817 335L<Catalyst::Manual::Intro/Action types>,
ee53cc71 336L<Catalyst::DispatchType::Chained>, and the 2006 Advent calendar entry
337on the subject: L<>.
89d3dae9 338
340=head2 Try the Chained Action
55490817 342If you look back at the development server startup logs from your
ee53cc71 343initial version of the C<url_create> method (the one using the C<:Local>
344attribute), you will notice that it produced output similar to the
89d3dae9 346
fbbb9084 347 [debug] Loaded Path actions:
348 .-------------------------------------+--------------------------------------.
349 | Path | Private |
350 +-------------------------------------+--------------------------------------+
351 | / | /default |
352 | / | /index |
353 | /books | /books/index |
354 | /books/list | /books/list |
355 | /books/url_create | /books/url_create |
356 '-------------------------------------+--------------------------------------'
89d3dae9 357
22fe0f18 358When the development server restarts after our conversion to Chained
359dispatch, the debug output should change to something along the lines of
360the following:
89d3dae9 361
fbbb9084 362 [debug] Loaded Path actions:
363 .-------------------------------------+--------------------------------------.
364 | Path | Private |
365 +-------------------------------------+--------------------------------------+
366 | / | /default |
367 | / | /index |
368 | /books | /books/index |
369 | /books/list | /books/list |
370 '-------------------------------------+--------------------------------------'
7ce05098 371
fbbb9084 372 [debug] Loaded Chained actions:
373 .-------------------------------------+--------------------------------------.
374 | Path Spec | Private |
375 +-------------------------------------+--------------------------------------+
376 | /books/url_create/*/*/* | /books/url_create |
377 '-------------------------------------+--------------------------------------'
89d3dae9 378
ee53cc71 379C<url_create> has disappeared from the "Loaded Path actions" section but
380it now shows up under the newly created "Loaded Chained actions"
72609296 381section. And the "/*/*/*" portion clearly shows our requirement for
fbbb9084 382three arguments.
89d3dae9 383
55490817 384As with our non-chained version of C<url_create>, use your browser to
89d3dae9 385enter the following URL:
fbbb9084 387 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
89d3dae9 388
55490817 389You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
390'Stevens' with a rating of 5." along with a dump of the new book model
72609296 391object. Click the "Return to list" link, and you should find that there
392are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>).
89d3dae9 393
8a472b34 395=head2 Refactor to Use a 'base' Method to Start the Chains
89d3dae9 396
ee53cc71 397Let's make a quick update to our initial Chained action to show a little
398more of the power of chaining. First, open
f4e9de4a 399F<lib/MyApp/Controller/> in your editor and add the following
89d3dae9 400method:
fbbb9084 402 =head2 base
7ce05098 403
fbbb9084 404 Can place common logic to start chained dispatch here
7ce05098 405
fbbb9084 406 =cut
7ce05098 407
fbbb9084 408 sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
409 my ($self, $c) = @_;
7ce05098 410
1cde0fd6 411 # Store the ResultSet in stash so it's available for other methods
0ed3df53 412 $c->stash(resultset => $c->model('DB::Book'));
7ce05098 413
fbbb9084 414 # Print a message to the debug log
415 $c->log->debug('*** INSIDE BASE METHOD ***');
416 }
55490817 418Here we print a log message and store the DBIC ResultSet in
429d1caf 419C<< $c->stash->{resultset} >> so that it's automatically available
55490817 420for other actions that chain off C<base>. If your controller always
72609296 421needs a book ID as its first argument, you could have the base method
55490817 422capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
429d1caf 423book object with C<< ->find($id) >> and leave it in the stash for later
ee53cc71 424parts of your chains to then act upon. Because we have several actions
425that don't need to retrieve a book (such as the C<url_create> we are
426working with now), we will instead add that functionality to a common
427C<object> action shortly.
994b66ad 428
55490817 429As for C<url_create>, let's modify it to first dispatch to C<base>.
f4e9de4a 430Open up F<lib/MyApp/Controller/> and edit the declaration for
994b66ad 431C<url_create> to match the following:
89d3dae9 432
433 sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
f4e9de4a 435Once you save F<lib/MyApp/Controller/>, notice that the
ee53cc71 436development server will restart and our "Loaded Chained actions" section
f2bbfc36 437will changed slightly:
55490817 438
fbbb9084 439 [debug] Loaded Chained actions:
440 .-------------------------------------+--------------------------------------.
441 | Path Spec | Private |
442 +-------------------------------------+--------------------------------------+
443 | /books/url_create/*/*/* | /books/base (0) |
444 | | => /books/url_create |
445 '-------------------------------------+--------------------------------------'
89d3dae9 446
ee53cc71 447The "Path Spec" is the same, but now it maps to two Private actions as
448we would expect. The C<base> method is being triggered by the C</books>
449part of the URL. However, the processing then continues to the
450C<url_create> method because this method "chained" off C<base> and
451specified C<:PathPart('url_create')> (note that we could have omitted
452the "PathPart" here because it matches the name of the method, but we
444d6b27 453will include it to make the logic as explicit as possible).
89d3dae9 454
455Once again, enter the following URL into your browser:
fbbb9084 457 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
89d3dae9 458
ee53cc71 459The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
460rating of 5." message and a dump of the new book object should appear.
461Also notice the extra "INSIDE BASE METHOD" debug message in the
462development server output from the C<base> method. Click the "Return to
463list" link, and you should find that there are now eight books shown.
464(You may have a larger number of books if you repeated any of the
465"create" actions more than once. Don't worry about it as long as the
466number of books is appropriate for the number of times you added new
467books... there should be the original five books added via
f4e9de4a 468F<myapp01.sql> plus one additional book for each time you ran one of the
ee53cc71 469url_create variations above.)
d442cc9f 470
474Although the C<url_create> action in the previous step does begin to
475reveal the power and flexibility of both Catalyst and DBIC, it's
476obviously not a very realistic example of how users should be expected
22fe0f18 477to enter data. This section begins to address that concern (but just
478barely, see L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
479for better options for handling web-based forms).
d442cc9f 480
482=head2 Add Method to Display The Form
f4e9de4a 484Edit F<lib/MyApp/Controller/> and add the following method:
d442cc9f 485
486 =head2 form_create
7ce05098 487
d442cc9f 488 Display form to collect information for book to create
7ce05098 489
d442cc9f 490 =cut
7ce05098 491
89d3dae9 492 sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
d442cc9f 493 my ($self, $c) = @_;
7ce05098 494
d442cc9f 495 # Set the TT template to use
0ed3df53 496 $c->stash(template => 'books/form_create.tt2');
d442cc9f 497 }
72609296 499This action simply invokes a view containing a form to create a book.
d442cc9f 500
1390ef0e 501
d442cc9f 502=head2 Add a Template for the Form
f4e9de4a 504Open F<root/src/books/form_create.tt2> in your editor and enter:
d442cc9f 505
506 [% META title = 'Manual Form Book Create' -%]
7ce05098 507
8a7c5151 508 <form method="post" action="[% c.uri_for('form_create_do') %]">
d442cc9f 509 <table>
02bb2b5a 510 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
511 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
512 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
d442cc9f 513 </table>
514 <input type="submit" name="Submit" value="Submit">
515 </form>
517Note that we have specified the target of the form data as
518C<form_create_do>, the method created in the section that follows.
1390ef0e 520
d442cc9f 521=head2 Add a Method to Process Form Values and Update Database
f4e9de4a 523Edit F<lib/MyApp/Controller/> and add the following method to
d442cc9f 524save the form information to the database:
526 =head2 form_create_do
7ce05098 527
d442cc9f 528 Take information from form and add to database
7ce05098 529
d442cc9f 530 =cut
7ce05098 531
89d3dae9 532 sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
d442cc9f 533 my ($self, $c) = @_;
7ce05098 534
d442cc9f 535 # Retrieve the values from the form
536 my $title = $c->request->params->{title} || 'N/A';
537 my $rating = $c->request->params->{rating} || 'N/A';
538 my $author_id = $c->request->params->{author_id} || '1';
7ce05098 539
d442cc9f 540 # Create the book
3b1fa91b 541 my $book = $c->model('DB::Book')->create({
d442cc9f 542 title => $title,
543 rating => $rating,
544 });
545 # Handle relationship with author
fce83e5f 546 $book->add_to_book_authors({author_id => $author_id});
547 # Note: Above is a shortcut for this:
548 # $book->create_related('book_authors', {author_id => $author_id});
7ce05098 549
0ed3df53 550 # Store new model object in stash and set template
551 $c->stash(book => $book,
552 template => 'books/create_done.tt2');
d442cc9f 553 }
556=head2 Test Out The Form
ee53cc71 558Notice that the server startup log reflects the two new chained methods
559that we added:
89d3dae9 560
fbbb9084 561 [debug] Loaded Chained actions:
562 .-------------------------------------+--------------------------------------.
563 | Path Spec | Private |
564 +-------------------------------------+--------------------------------------+
565 | /books/form_create | /books/base (0) |
566 | | => /books/form_create |
567 | /books/form_create_do | /books/base (0) |
568 | | => /books/form_create_do |
569 | /books/url_create/*/*/* | /books/base (0) |
570 | | => /books/url_create |
571 '-------------------------------------+--------------------------------------'
89d3dae9 572
d442cc9f 573Point your browser to L<http://localhost:3000/books/form_create> and
574enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
1390ef0e 575author ID of 4. You should then see the output of the same
f4e9de4a 576F<create_done.tt2> template seen in earlier examples. Finally, click
d442cc9f 577"Return to list" to view the full list of books.
579B<Note:> Having the user enter the primary key ID for the author is
fce83e5f 580obviously crude; we will address this concern with a drop-down list and
22fe0f18 581add validation to our forms in
582L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>.
d442cc9f 583
72609296 587Turning our attention to the Delete portion of CRUD, this section
d442cc9f 588illustrates some basic techniques that can be used to remove information
589from the database.
592=head2 Include a Delete Link in the List
f4e9de4a 594Edit F<root/src/books/list.tt2> and update it to match the following
ee53cc71 595(two sections have changed: 1) the additional '<th>Links</th>' table
22fe0f18 596header, and 2) the five lines for the Delete link near the bottom):
d442cc9f 597
22fe0f18 598 [% # This is a TT comment. -%]
7ce05098 599
22fe0f18 600 [%- # Provide a title -%]
d442cc9f 601 [% META title = 'Book List' -%]
7ce05098 602
22fe0f18 603 [% # Note That the '-' at the beginning or end of TT code -%]
604 [% # "chomps" the whitespace/newline at that end of the -%]
605 [% # output (use View Source in browser to see the effect) -%]
7ce05098 606
22fe0f18 607 [% # Some basic HTML with a loop to display books -%]
d442cc9f 608 <table>
609 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
610 [% # Display each book in a table row %]
611 [% FOREACH book IN books -%]
02bb2b5a 612 <tr>
613 <td>[% book.title %]</td>
614 <td>[% book.rating %]</td>
615 <td>
616 [% # NOTE: See Chapter 4 for a better way to do this! -%]
617 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
618 [% # loop in 'side effect notation' to load just the last names of the -%]
619 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
620 [% # a value, so nothing will be printed here. But, if you have something -%]
621 [% # in TT that does return a value and you don't want it printed, you -%]
622 [% # 1) assign it to a bogus value, or -%]
623 [% # 2) use the CALL keyword to call it and discard the return value. -%]
624 [% tt_authors = [ ];
625 tt_authors.push(author.last_name) FOREACH author = book.authors %]
626 [% # Now use a TT 'virtual method' to display the author count in parens -%]
627 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
628 ([% tt_authors.size | html %])
629 [% # Use another TT vmethod to join & print the names & comma separators -%]
630 [% tt_authors.join(', ') | html %]
631 </td>
632 <td>
633 [% # Add a link to delete a book %]
634 <a href="[%
635 c.uri_for(c.controller.action_for('delete'), []) %]">Delete</a>
636 </td>
637 </tr>
d442cc9f 638 [% END -%]
639 </table>
55490817 641The additional code is obviously designed to add a new column to the
72609296 642right side of the table with a C<Delete> "button" (for simplicity, links
22fe0f18 643will be used instead of full HTML buttons; but, in practice, anything
644that modifies data should be handled with a form sending a POST
fe01b24f 646
ee53cc71 647Also notice that we are using a more advanced form of C<uri_for> than we
429d1caf 648have seen before. Here we use C<< $c->controller->action_for >> to
ee53cc71 649automatically generate a URI appropriate for that action based on the
650method we want to link to while inserting the C<> value into the
651appropriate place. Now, if you ever change C<:PathPart('delete')> in
22fe0f18 652your controller method to something like C<:PathPart('kill')>, then your
653links will automatically update without any changes to your .tt2
654template file. As long as the name of your method does not change
655(here, "delete"), then your links will still be correct. There are a
656few shortcuts and options when using C<action_for()>:
0416017e 657
658=over 4
660=item *
ee53cc71 662If you are referring to a method in the current controller, you can use
429d1caf 663C<< $self->action_for('_method_name_') >>.
0416017e 664
665=item *
ee53cc71 667If you are referring to a method in a different controller, you need to
668include that controller's name as an argument to C<controller()>, as in
429d1caf 669C<< $c->controller('_controller_name_')->action_for('_method_name_') >>.
0416017e 670
b2ad8bbd 672
55490817 673B<Note:> In practice you should B<never> use a GET request to delete a
674record -- always use POST for actions that will modify data. We are
c5d94181 675doing it here for illustrative and simplicity purposes only.
d442cc9f 676
1390ef0e 677
994b66ad 678=head2 Add a Common Method to Retrieve a Book for the Chain
ee53cc71 680As mentioned earlier, since we have a mixture of actions that operate on
681a single book ID and others that do not, we should not have C<base>
55490817 682capture the book ID, find the corresponding book in the database and
683save it in the stash for later links in the chain. However, just
ee53cc71 684because that logic does not belong in C<base> doesn't mean that we can't
685create another location to centralize the book lookup code. In our
686case, we will create a method called C<object> that will store the
55490817 687specific book in the stash. Chains that always operate on a single
688existing book can chain off this method, but methods such as
ee53cc71 689C<url_create> that don't operate on an existing book can chain directly
690off base.
994b66ad 691
f4e9de4a 692To add the C<object> method, edit F<lib/MyApp/Controller/> and
ee53cc71 693add the following code:
994b66ad 694
e075db0c 695 =head2 object
7ce05098 696
e075db0c 697 Fetch the specified book object based on the book ID and store
698 it in the stash
7ce05098 699
e075db0c 700 =cut
7ce05098 701
994b66ad 702 sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
fbbb9084 703 # $id = primary key of book to delete
994b66ad 704 my ($self, $c, $id) = @_;
7ce05098 705
994b66ad 706 # Find the book object and store it in the stash
707 $c->stash(object => $c->stash->{resultset}->find($id));
7ce05098 708
994b66ad 709 # Make sure the lookup was successful. You would probably
710 # want to do something like this in a real app:
711 # $c->detach('/error_404') if !$c->stash->{object};
712 die "Book $id not found!" if !$c->stash->{object};
7ce05098 713
fce83e5f 714 # Print a message to the debug log
715 $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***");
994b66ad 716 }
ee53cc71 718Now, any other method that chains off C<object> will automatically have
429d1caf 719the appropriate book waiting for it in C<< $c->stash->{object} >>.
994b66ad 720
994b66ad 721
d442cc9f 722=head2 Add a Delete Action to the Controller
f4e9de4a 724Open F<lib/MyApp/Controller/> in your editor and add the
d442cc9f 725following method:
1390ef0e 727 =head2 delete
7ce05098 728
d442cc9f 729 Delete a book
7ce05098 730
d442cc9f 731 =cut
7ce05098 732
994b66ad 733 sub delete :Chained('object') :PathPart('delete') :Args(0) {
994b66ad 734 my ($self, $c) = @_;
7ce05098 735
994b66ad 736 # Use the book object saved by 'object' and delete it along
3b1fa91b 737 # with related 'book_author' entries
994b66ad 738 $c->stash->{object}->delete;
7ce05098 739
d442cc9f 740 # Set a status message to be displayed at the top of the view
741 $c->stash->{status_msg} = "Book deleted.";
7ce05098 742
d442cc9f 743 # Forward to the list action/method in this controller
744 $c->forward('list');
745 }
55490817 747This method first deletes the book object saved by the C<object> method.
ee53cc71 748However, it also removes the corresponding entry from the C<book_author>
749table with a cascading delete.
d442cc9f 750
751Then, rather than forwarding to a "delete done" page as we did with the
752earlier create example, it simply sets the C<status_msg> to display a
753notification to the user as the normal list view is rendered.
755The C<delete> action uses the context C<forward> method to return the
756user to the book list. The C<detach> method could have also been used.
757Whereas C<forward> I<returns> to the original action once it is
758completed, C<detach> does I<not> return. Other than that, the two are
762=head2 Try the Delete Feature
ee53cc71 764Once you save the Books controller, the server should automatically
765restart. The C<delete> method should now appear in the "Loaded Chained
766actions" section of the startup debug output:
89d3dae9 767
fbbb9084 768 [debug] Loaded Chained actions:
994b66ad 769 .-------------------------------------+--------------------------------------.
770 | Path Spec | Private |
771 +-------------------------------------+--------------------------------------+
772 | /books/id/*/delete | /books/base (0) |
773 | | -> /books/object (1) |
774 | | => /books/delete |
775 | /books/form_create | /books/base (0) |
776 | | => /books/form_create |
777 | /books/form_create_do | /books/base (0) |
778 | | => /books/form_create_do |
779 | /books/url_create/*/*/* | /books/base (0) |
780 | | => /books/url_create |
781 '-------------------------------------+--------------------------------------'
89d3dae9 782
d442cc9f 783Then point your browser to L<http://localhost:3000/books/list> and click
55490817 784the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green
785"Book deleted" status message should display at the top of the page,
994b66ad 786along with a list of the eight remaining books. You will also see the
787cascading delete operation via the DBIC_TRACE output:
3b1fa91b 789 SELECT, me.title, me.rating FROM book me WHERE ( ( = ? ) ): '6'
790 DELETE FROM book WHERE ( id = ? ): '6'
d442cc9f 791
d28e06d1 792If you get the error C<file error - books/delete.tt2: not found> then you
793probably forgot to uncomment the template line in C<sub list> at the end of
794chapter 3.
d442cc9f 795
796=head2 Fixing a Dangerous URL
55490817 798Note the URL in your browser once you have performed the deletion in the
d442cc9f 799prior step -- it is still referencing the delete action:
acbd7bdd 801 http://localhost:3000/books/id/6/delete
d442cc9f 802
55490817 803What if the user were to press reload with this URL still active? In
ee53cc71 804this case the redundant delete is harmless (although it does generate an
805exception screen, it doesn't perform any undesirable actions on the
22fe0f18 806application or database), but in other cases this could clearly lead to
d442cc9f 808
809We can improve the logic by converting to a redirect. Unlike
429d1caf 810C<< $c->forward('list')) >> or C<< $c->detach('list')) >> that perform a
ee53cc71 811server-side alteration in the flow of processing, a redirect is a
812client-side mechanism that causes the browser to issue an entirely new
813request. As a result, the URL in the browser is updated to match the
814destination of the redirection URL.
d442cc9f 815
ee53cc71 816To convert the forward used in the previous section to a redirect, open
f4e9de4a 817F<lib/MyApp/Controller/> and edit the existing C<sub delete>
ee53cc71 818method to match:
d442cc9f 819
994b66ad 820 =head2 delete
7ce05098 821
d442cc9f 822 Delete a book
7ce05098 823
d442cc9f 824 =cut
7ce05098 825
994b66ad 826 sub delete :Chained('object') :PathPart('delete') :Args(0) {
fbbb9084 827 my ($self, $c) = @_;
7ce05098 828
994b66ad 829 # Use the book object saved by 'object' and delete it along
3b1fa91b 830 # with related 'book_author' entries
994b66ad 831 $c->stash->{object}->delete;
7ce05098 832
d442cc9f 833 # Set a status message to be displayed at the top of the view
834 $c->stash->{status_msg} = "Book deleted.";
7ce05098 835
0416017e 836 # Redirect the user back to the list page. Note the use
837 # of $self->action_for as earlier in this section (BasicCRUD)
fbbb9084 838 $c->response->redirect($c->uri_for($self->action_for('list')));
d442cc9f 839 }
842=head2 Try the Delete and Redirect Logic
ee53cc71 844Point your browser to L<http://localhost:3000/books/list> (don't just
845hit "Refresh" in your browser since we left the URL in an invalid state
846in the previous section!) and delete the first copy of the remaining two
847"TCPIP_Illustrated_Vol-2" books. The URL in your browser should return
848to the L<http://localhost:3000/books/list> URL, so that is an
849improvement, but notice that I<no green "Book deleted" status message is
850displayed>. Because the stash is reset on every request (and a redirect
851involves a second request), the C<status_msg> is cleared before it can
22fe0f18 852be displayed.
d442cc9f 853
8a472b34 855=head2 Using 'uri_for' to Pass Query Parameters
d442cc9f 856
ee53cc71 857There are several ways to pass information across a redirect. One option
22fe0f18 858is to use the C<flash> technique that we will see in
859L<Chapter 5|Catalyst::Manual::Tutorial::05_Authentication> of this
ee53cc71 860tutorial; however, here we will pass the information via query
861parameters on the redirect itself. Open
f4e9de4a 862F<lib/MyApp/Controller/> and update the existing C<sub delete>
89d3dae9 863method to match the following:
d442cc9f 864
55490817 865 =head2 delete
7ce05098 866
d442cc9f 867 Delete a book
7ce05098 868
d442cc9f 869 =cut
7ce05098 870
994b66ad 871 sub delete :Chained('object') :PathPart('delete') :Args(0) {
fbbb9084 872 my ($self, $c) = @_;
7ce05098 873
994b66ad 874 # Use the book object saved by 'object' and delete it along
3b1fa91b 875 # with related 'book_author' entries
994b66ad 876 $c->stash->{object}->delete;
7ce05098 877
d442cc9f 878 # Redirect the user back to the list page with status msg as an arg
55490817 879 $c->response->redirect($c->uri_for($self->action_for('list'),
d442cc9f 880 {status_msg => "Book deleted."}));
881 }
883This modification simply leverages the ability of C<uri_for> to include
55490817 884an arbitrary number of name/value pairs in a hash reference. Next, we
f4e9de4a 885need to update F<root/src/wrapper.tt2> to handle C<status_msg> as a
d442cc9f 886query parameter:
1390ef0e 888 ...
d442cc9f 889 <div id="content">
1390ef0e 890 [%# Status and error messages %]
ee53cc71 891 <span class="message">[%
892 status_msg || c.request.params.status_msg | html %]</span>
1390ef0e 893 <span class="error">[% error_msg %]</span>
894 [%# This is where TT will stick all of your template's contents. -%]
895 [% content %]
896 </div><!-- end content -->
897 ...
ee53cc71 899Although the sample above only shows the C<content> div, leave the rest
f4e9de4a 900of the file intact -- the only change we made to the F<wrapper.tt2> was
22fe0f18 901to add "C<|| c.request.params.status_msg>" to the
429d1caf 902C<< <span class="message"> >> line. Note that we definitely want
b3876d9e 903the "C<| html>" TT filter here since it would be easy for users to
904modify the message on the URL and possibly inject harmful code into the
905application if we left that off.
d442cc9f 906
908=head2 Try the Delete and Redirect With Query Param Logic
ee53cc71 910Point your browser to L<http://localhost:3000/books/list> (you should
911now be able to safely hit "refresh" in your browser). Then delete the
912remaining copy of "TCPIP_Illustrated_Vol-2". The green "Book deleted"
a608d8ce 913status message should return. But notice that you can now hit the
ee53cc71 914"Reload" button in your browser and it just redisplays the book list
915(and it correctly shows it without the "Book deleted" message on
d442cc9f 917
22fe0f18 918B<NOTE:> Be sure to check out
919L<Authentication|Catalyst::Manual::Tutorial::05_Authentication> where we
920use an improved technique that is better suited to your real world
d442cc9f 922
1cde0fd6 924=head1 EXPLORING THE POWER OF DBIC
ee53cc71 926In this section we will explore some additional capabilities offered by
22fe0f18 927L<DBIx::Class>. Although these features have relatively little to do
928with Catalyst per se, you will almost certainly want to take advantage
929of them in your applications.
1cde0fd6 930
1cde0fd6 932=head2 Add Datetime Columns to Our Existing Books Table
ee53cc71 934Let's add two columns to our existing C<books> table to track when each
935book was added and when each book is updated:
1cde0fd6 936
937 $ sqlite3 myapp.db
33f1d5d0 938 sqlite> ALTER TABLE book ADD created TIMESTAMP;
939 sqlite> ALTER TABLE book ADD updated TIMESTAMP;
3b1fa91b 940 sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
941 sqlite> SELECT * FROM book;
f2bbfc36 942 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
943 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
944 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
945 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
946 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
947 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1cde0fd6 948 sqlite> .quit
949 $
d5d7ee98 951Here are the commands without the surrounding sqlite3 prompt and output
952in case you want to cut and paste them as a single block (but still
953start sqlite3 before you paste these in):
957 UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
958 SELECT * FROM book;
ee53cc71 960This will modify the C<books> table to include the two new fields and
961populate those fields with the current time.
1cde0fd6 962
acbd7bdd 963
a46b474e 964=head2 Update DBIx::Class to Automatically Handle the Datetime Columns
1cde0fd6 965
ee53cc71 966Next, we should re-run the DBIC helper to update the Result Classes with
967the new fields:
1cde0fd6 968
969 $ script/ model DB DBIC::Schema MyApp::Schema \
b6e53c1c 970 create=static components=TimeStamp dbi:SQLite:myapp.db \
b66dd084 971 on_connect_do="PRAGMA foreign_keys = ON"
477a6d5b 972 exists "/home/catalyst/dev/MyApp/script/../lib/MyApp/Model"
973 exists "/home/catalyst/dev/MyApp/script/../t"
974 Dumping manual schema for MyApp::Schema to directory /home/catalyst/dev/MyApp/script/../lib ...
1cde0fd6 975 Schema dump completed.
477a6d5b 976 exists "/home/catalyst/dev/MyApp/script/../lib/MyApp/Model/"
1cde0fd6 977
ee53cc71 978Notice that we modified our use of the helper slightly: we told it to
979include the L<DBIx::Class::TimeStamp> in the C<load_components> line of
980the Result Classes.
1cde0fd6 981
f4e9de4a 982If you open F<lib/MyApp/Schema/Result/> in your editor you should
ee53cc71 983see that the C<created> and C<updated> fields are now included in the
984call to C<add_columns()>. However, also notice that the C<many_to_many>
985relationships we manually added below the "C<# DO NOT MODIFY...>" line
986were automatically preserved.
1cde0fd6 987
f4e9de4a 988While we F<lib/MyApp/Schema/Result/> open, let's update it with
d5d7ee98 989some additional information to have DBIC automatically handle the
990updating of these two fields for us. Insert the following code at the
991bottom of the file (it B<must> be B<below> the "C<# DO NOT MODIFY...>"
992line and B<above> the C<1;> on the last line):
1cde0fd6 993
994 #
995 # Enable automatic date handling
996 #
997 __PACKAGE__->add_columns(
998 "created",
33f1d5d0 999 { data_type => 'timestamp', set_on_create => 1 },
1cde0fd6 1000 "updated",
33f1d5d0 1001 { data_type => 'timestamp', set_on_create => 1, set_on_update => 1 },
55490817 1002 );
1cde0fd6 1003
ee53cc71 1004This will override the definition for these fields that Schema::Loader
1005placed at the top of the file. The C<set_on_create> and
1006C<set_on_update> options will cause DBIx::Class to automatically update
1007the timestamps in these columns whenever a row is created or modified.
1cde0fd6 1008
22fe0f18 1009B<Note> that adding the lines above will cause the development server to
1010automatically restart if you are running it with the "-r" option. In
1011other words, the development server is smart enough to restart not only
f4e9de4a 1012for code under the F<MyApp/Controller/>, F<MyApp/Model/>, and
1013F<MyApp/View/> directories, but also under other directions such as our
1014"external DBIC model" in F<MyApp/Schema/>. However, also note that it's
22fe0f18 1015smart enough to B<not> restart when you edit your C<.tt2> files under
f4e9de4a 1016F<root/>.
22fe0f18 1017
1cde0fd6 1018Then enter the following URL into your web browser:
1020 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
22fe0f18 1022You should get the same "Book Created" screen we saw earlier. However, if
ee53cc71 1023you now use the sqlite3 command-line tool to dump the C<books> table,
1024you will see that the new book we added has an appropriate date and time
1025entered for it (see the last line in the listing below):
1cde0fd6 1026
444d6b27 1027 $ sqlite3 myapp.db "select * from book"
f2bbfc36 1028 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1029 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1030 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
1031 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1032 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1033 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1034 10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42
1cde0fd6 1035
55490817 1036Notice in the debug log that the SQL DBIC generated has changed to
1cde0fd6 1037incorporate the datetime logic:
7ce05098 1039 INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ):
f2bbfc36 1040 '2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42'
2a6eb5f9 1041 INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10'
1cde0fd6 1042
1044=head2 Create a ResultSet Class
444d6b27 1046An often overlooked but extremely powerful features of DBIC is that it
cacb3819 1047allows you to supply your own subclasses of L<DBIx::Class::ResultSet>.
22fe0f18 1048This can be used to pull complex and unsightly "query code" out of your
1cde0fd6 1049controllers and encapsulate it in a method of your ResultSet Class.
ee53cc71 1050These "canned queries" in your ResultSet Class can then be invoked via a
1051single call, resulting in much cleaner and easier to read controller
22fe0f18 1052code (or View code, if that's where you want to call it).
1cde0fd6 1053
55490817 1054To illustrate the concept with a fairly simple example, let's create a
ee53cc71 1055method that returns books added in the last 10 minutes. Start by making
1056a directory where DBIx::Class will look for our ResultSet Class:
1cde0fd6 1057
444d6b27 1058 $ mkdir lib/MyApp/Schema/ResultSet
1cde0fd6 1059
f4e9de4a 1060Then open F<lib/MyApp/Schema/ResultSet/> and enter the following:
1cde0fd6 1061
3b1fa91b 1062 package MyApp::Schema::ResultSet::Book;
7ce05098 1063
1cde0fd6 1064 use strict;
1065 use warnings;
1066 use base 'DBIx::Class::ResultSet';
7ce05098 1067
1cde0fd6 1068 =head2 created_after
7ce05098 1069
1cde0fd6 1070 A predefined search for recently added books
7ce05098 1071
1cde0fd6 1072 =cut
7ce05098 1073
1cde0fd6 1074 sub created_after {
fadc4ae7 1075 my ($self, $datetime) = @_;
7ce05098 1076
b66dd084 1077 my $date_str = $self->result_source->schema->storage
fadc4ae7 1078 ->datetime_parser->format_datetime($datetime);
7ce05098 1079
fadc4ae7 1080 return $self->search({
1081 created => { '>' => $date_str }
1082 });
1cde0fd6 1083 }
7ce05098 1084
1cde0fd6 1085 1;
f4e9de4a 1087Then add the following method to the F<lib/MyApp/Controller/>:
1cde0fd6 1088
1089 =head2 list_recent
7ce05098 1090
1cde0fd6 1091 List recently created books
7ce05098 1092
1cde0fd6 1093 =cut
7ce05098 1094
1cde0fd6 1095 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
1096 my ($self, $c, $mins) = @_;
7ce05098 1097
1cde0fd6 1098 # Retrieve all of the book records as book model objects and store in the
1099 # stash where they can be accessed by the TT template, but only
1100 # retrieve books created within the last $min number of minutes
0ed3df53 1101 $c->stash(books => [$c->model('DB::Book')
1102 ->created_after(DateTime->now->subtract(minutes => $mins))]);
7ce05098 1103
1cde0fd6 1104 # Set the TT template to use. You will almost always want to do this
1105 # in your action methods (action methods respond to user input in
1106 # your controllers).
0ed3df53 1107 $c->stash(template => 'books/list.tt2');
1cde0fd6 1108 }
ee53cc71 1110Now try different values for the "minutes" argument (the final number
1111value) using the URL C<http://localhost:3000/books/list_recent/_#_> in
1112your browser. For example, this would list all books added in the last
1113fifteen minutes:
1cde0fd6 1114
1115 http://localhost:3000/books/list_recent/15
ee53cc71 1117Depending on how recently you added books, you might want to try a
1118higher or lower value for the minutes.
1cde0fd6 1119
1121=head2 Chaining ResultSets
cacb3819 1123One of the most helpful and powerful features in L<DBIx::Class> is that
22fe0f18 1124it allows you to "chain together" a series of queries (note that this
1125has nothing to do with the "Chained Dispatch" for Catalyst that we were
1126discussing earlier). Because each ResultSet method returns another
1127ResultSet, you can take an initial query and immediately feed that into
1128a second query (and so on for as many queries you need). Note that no
1129matter how many ResultSets you chain together, the database itself will
1130not be hit until you use a method that attempts to access the data. And,
1131because this technique carries over to the ResultSet Class feature we
ee53cc71 1132implemented in the previous section for our "canned search", we can
1133combine the two capabilities. For example, let's add an action to our
1134C<Books> controller that lists books that are both recent I<and> have
f4e9de4a 1135"TCP" in the title. Open up F<lib/MyApp/Controller/> and add
ee53cc71 1136the following method:
1cde0fd6 1137
acbd7bdd 1138 =head2 list_recent_tcp
7ce05098 1139
1cde0fd6 1140 List recently created books
7ce05098 1141
1cde0fd6 1142 =cut
7ce05098 1143
1cde0fd6 1144 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1145 my ($self, $c, $mins) = @_;
7ce05098 1146
1cde0fd6 1147 # Retrieve all of the book records as book model objects and store in the
1148 # stash where they can be accessed by the TT template, but only
1149 # retrieve books created within the last $min number of minutes
1150 # AND that have 'TCP' in the title
22fe0f18 1151 $c->stash(books => [
1152 $c->model('DB::Book')
1153 ->created_after(DateTime->now->subtract(minutes => $mins))
1154 ->search({title => {'like', '%TCP%'}})
1155 ]);
7ce05098 1156
1cde0fd6 1157 # Set the TT template to use. You will almost always want to do this
1158 # in your action methods (action methods respond to user input in
1159 # your controllers).
0ed3df53 1160 $c->stash(template => 'books/list.tt2');
1cde0fd6 1161 }
f2bbfc36 1163To try this out, enter the following URL into your browser:
1cde0fd6 1164
1165 http://localhost:3000/books/list_recent_tcp/100
55490817 1167And you should get a list of books added in the last 100 minutes that
1168contain the string "TCP" in the title. However, if you look at all
ee53cc71 1169books within the last 100 minutes, you should get a longer list (again,
1170you might have to adjust the number of minutes depending on how recently
1171you added books to your database):
1cde0fd6 1172
1173 http://localhost:3000/books/list_recent/100
55490817 1175Take a look at the DBIC_TRACE output in the development server log for
1cde0fd6 1176the first URL and you should see something similar to the following:
7ce05098 1178 SELECT, me.title, me.rating, me.created, me.updated FROM book me
f2bbfc36 1179 WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32'
1cde0fd6 1180
ee53cc71 1181However, let's not pollute our controller code with this raw "TCP" query
1182-- it would be cleaner to encapsulate that code in a method on our
f4e9de4a 1183ResultSet Class. To do this, open F<lib/MyApp/Schema/ResultSet/>
ee53cc71 1184and add the following method:
1cde0fd6 1185
1186 =head2 title_like
7ce05098 1187
1cde0fd6 1188 A predefined search for books with a 'LIKE' search in the string
7ce05098 1189
1cde0fd6 1190 =cut
7ce05098 1191
1cde0fd6 1192 sub title_like {
fadc4ae7 1193 my ($self, $title_str) = @_;
7ce05098 1194
fadc4ae7 1195 return $self->search({
1196 title => { 'like' => "%$title_str%" }
1197 });
1cde0fd6 1198 }
55490817 1200We defined the search string as C<$title_str> to make the method more
1201flexible. Now update the C<list_recent_tcp> method in
f4e9de4a 1202F<lib/MyApp/Controller/> to match the following (we have
429d1caf 1203replaced the C<< ->search >> line with the C<< ->title_like >> line
1cde0fd6 1204shown here -- the rest of the method should be the same):
1206 =head2 list_recent_tcp
7ce05098 1207
1cde0fd6 1208 List recently created books
7ce05098 1209
1cde0fd6 1210 =cut
7ce05098 1211
1cde0fd6 1212 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1213 my ($self, $c, $mins) = @_;
7ce05098 1214
1cde0fd6 1215 # Retrieve all of the book records as book model objects and store in the
1216 # stash where they can be accessed by the TT template, but only
1217 # retrieve books created within the last $min number of minutes
1218 # AND that have 'TCP' in the title
22fe0f18 1219 $c->stash(books => [
1220 $c->model('DB::Book')
1221 ->created_after(DateTime->now->subtract(minutes => $mins))
1222 ->title_like('TCP')
1223 ]);
7ce05098 1224
1cde0fd6 1225 # Set the TT template to use. You will almost always want to do this
1226 # in your action methods (action methods respond to user input in
1227 # your controllers).
0ed3df53 1228 $c->stash(template => 'books/list.tt2');
1cde0fd6 1229 }
ee53cc71 1231Try out the C<list_recent_tcp> and C<list_recent> URLs as we did above.
1232They should work just the same, but our code is obviously cleaner and
1233more modular, while also being more flexible at the same time.
1cde0fd6 1234
1236=head2 Adding Methods to Result Classes
ee53cc71 1238In the previous two sections we saw a good example of how we could use
1239DBIx::Class ResultSet Classes to clean up our code for an entire query
1240(for example, our "canned searches" that filtered the entire query). We
1241can do a similar improvement when working with individual rows as well.
1242Whereas the ResultSet construct is used in DBIC to correspond to an
1243entire query, the Result Class construct is used to represent a row.
1244Therefore, we can add row-specific "helper methods" to our Result
f4e9de4a 1245Classes stored in F<lib/MyApp/Schema/Result/>. For example, open
1246F<lib/MyApp/Schema/Result/> and add the following method (as
a46b474e 1247always, it must be above the closing "C<1;>"):
1cde0fd6 1248
1249 #
a608d8ce 1250 # Row-level helper methods
1cde0fd6 1251 #
1252 sub full_name {
1253 my ($self) = @_;
7ce05098 1254
1cde0fd6 1255 return $self->first_name . ' ' . $self->last_name;
1256 }
ee53cc71 1258This will allow us to conveniently retrieve both the first and last name
f4e9de4a 1259for an author in one shot. Now open F<root/src/books/list.tt2> and
ee53cc71 1260change the definition of C<tt_authors> from this:
1cde0fd6 1261
acbd7bdd 1262 ...
1cde0fd6 1263 [% tt_authors = [ ];
fce83e5f 1264 tt_authors.push(author.last_name) FOREACH author = book.authors %]
acbd7bdd 1265 ...
1cde0fd6 1266
acbd7bdd 1269 ...
1cde0fd6 1270 [% tt_authors = [ ];
fce83e5f 1271 tt_authors.push(author.full_name) FOREACH author = book.authors %]
acbd7bdd 1272 ...
1cde0fd6 1273
ee53cc71 1274(Only C<author.last_name> was changed to C<author.full_name> -- the rest
1275of the file should remain the same.)
1cde0fd6 1276
f2bbfc36 1277Now go to the standard book list URL:
1cde0fd6 1278
1279 http://localhost:3000/books/list
55490817 1281The "Author(s)" column will now contain both the first and last name.
ee53cc71 1282And, because the concatenation logic was encapsulated inside our Result
1283Class, it keeps the code inside our TT template nice and clean
55490817 1284(remember, we want the templates to be as close to pure HTML markup as
1285possible). Obviously, this capability becomes even more useful as you
0ed0d69a 1286use it to remove even more complicated row-specific logic from your
1cde0fd6 1287templates!
fce83e5f 1290=head2 Moving Complicated View Code to the Model
ee53cc71 1292The previous section illustrated how we could use a Result Class method
1293to print the full names of the authors without adding any extra code to
1294our view, but it still left us with a fairly ugly mess (see
f4e9de4a 1295F<root/src/books/list.tt2>):
fce83e5f 1296
1297 ...
1298 <td>
02bb2b5a 1299 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1300 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1301 [% # loop in 'side effect notation' to load just the last names of the -%]
1302 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1303 [% # a value, so nothing will be printed here. But, if you have something -%]
1304 [% # in TT that does return a method and you don't want it printed, you -%]
1305 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1306 [% # call it and discard the return value. -%]
1307 [% tt_authors = [ ];
1308 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1309 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1310 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1311 ([% tt_authors.size | html %])
1312 [% # Use another TT vmethod to join & print the names & comma separators -%]
1313 [% tt_authors.join(', ') | html %]
fce83e5f 1314 </td>
1315 ...
ee53cc71 1317Let's combine some of the techniques used earlier in this section to
1318clean this up. First, let's add a method to our Book Result Class to
1319return the number of authors for a book. Open
f4e9de4a 1320F<lib/MyApp/Schema/Result/> and add the following method:
fce83e5f 1321
444d6b27 1322 =head2 author_count
7ce05098 1323
444d6b27 1324 Return the number of authors for the current book
7ce05098 1325
fce83e5f 1326 =cut
7ce05098 1327
fce83e5f 1328 sub author_count {
1329 my ($self) = @_;
7ce05098 1330
fce83e5f 1331 # Use the 'many_to_many' relationship to fetch all of the authors for the current
1332 # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT
1333 return $self->authors->count;
1334 }
1336Next, let's add a method to return a list of authors for a book to the
f4e9de4a 1337same F<lib/MyApp/Schema/Result/> file:
fce83e5f 1338
1339 =head2 author_list
7ce05098 1340
fce83e5f 1341 Return a comma-separated list of authors for the current book
7ce05098 1342
fce83e5f 1343 =cut
7ce05098 1344
fce83e5f 1345 sub author_list {
1346 my ($self) = @_;
7ce05098 1347
1348 # Loop through all authors for the current book, calling all the 'full_name'
fce83e5f 1349 # Result Class method for each
1350 my @names;
1351 foreach my $author ($self->authors) {
1352 push(@names, $author->full_name);
1353 }
7ce05098 1354
fce83e5f 1355 return join(', ', @names);
1356 }
ee53cc71 1358This method loops through each author, using the C<full_name> Result
f4e9de4a 1359Class method we added to F<lib/MyApp/Schema/Result/> in the
fce83e5f 1360prior section.
1362Using these two methods, we can simplify our TT code. Open
f4e9de4a 1363F<root/src/books/list.tt2> and update the "Author(s)" table cell to
fce83e5f 1364match the following:
1366 ...
1367 <td>
02bb2b5a 1368 [% # Print count and author list using Result Class methods -%]
1369 ([% book.author_count | html %]) [% book.author_list | html %]
fce83e5f 1370 </td>
1371 ...
ee53cc71 1373Although most of the code we removed comprised comments, the overall
1374effect is dramatic... because our view code is so simple, we don't need
22fe0f18 1375huge comments to clue people in to the gist of our code. The view code
ee53cc71 1376is now self-documenting and readable enough that you could probably get
22fe0f18 1377by with no comments at all. All of the "complex" work is being done in
ee53cc71 1378our Result Class methods (and, because we have broken the code into
1379nice, modular chunks, the Result Class code is hardly something you
f2bbfc36 1380would call complex).
fce83e5f 1381
ee53cc71 1382As we saw in this section, always strive to keep your view AND
1383controller code as simple as possible by pulling code out into your
22fe0f18 1384model objects. Because L<DBIx::Class> can be easily extended in so many
ee53cc71 1385ways, it's an excellent to way accomplish this objective. It will make
1386your code cleaner, easier to write, less error-prone, and easier to
1387debug and maintain.
fce83e5f 1388
ee53cc71 1389Before you conclude this section, hit Refresh in your browser... the
1390output should be the same even though the backend code has been trimmed
444d6b27 1392
fce83e5f 1393
24acc5d7 1394You can jump to the next chapter of the tutorial here:
d442cc9f 1398=head1 AUTHOR
1400Kennedy Clark, C<>
53243324 1402Feel free to contact the author for any errors or suggestions, but the
1403best way to report issues is via the CPAN RT Bug system at
bb0999d3 1404L<>.
53243324 1405
bb0999d3 1406Copyright 2006-2011, Kennedy Clark, under the
ec3ef4ad 1407Creative Commons Attribution Share-Alike License Version 3.0
95674086 1408(L<>).