A few minor clarifications/adjustments
[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
4b4d3884 59This chapter of the tutorial builds on the fairly primitive
60application created in Chapter 3 to add basic support for Create,
61Read, Update, and Delete (CRUD) of C<Book> objects. Note that the
62'list' function in Chapter 2 already implements the Read portion of
63CRUD (although Read normally refers to reading a single object; you
72609296 64could implement full Read functionality using the techniques
4b4d3884 65introduced below). This section will focus on the Create and Delete
66aspects of CRUD. More advanced capabilities, including full Update
67functionality, will be addressed in Chapter 9.
69Although this chapter of the tutorial will show you how to build CRUD
70functionality yourself, another option is to use a "CRUD builder" type
f2bbfc36 71of tool to automate the process. You get less control, but it can be
72quick and easy. For example, see
d7db9156 73L<Catalyst::Plugin::AutoCRUD|Catalyst::Plugin::AutoCRUD>,
4b4d3884 74L<CatalystX::CRUD|CatalystX::CRUD>, and
7edc5484 75L<CatalystX::CRUD::YUI|CatalystX::CRUD::YUI>.
1390ef0e 76
72609296 77You can check out the source code for this example from the Catalyst
78Subversion repository as per the instructions in
3ab6187c 79L<Catalyst::Manual::Tutorial::01_Intro|Catalyst::Manual::Tutorial::01_Intro>.
d442cc9f 80
3533daff 81
d442cc9f 82=head1 FORMLESS SUBMISSION
55490817 84Our initial attempt at object creation will utilize the "URL
3533daff 85arguments" feature of Catalyst (we will employ the more common form-
86based submission in the sections that follow).
d442cc9f 87
89=head2 Include a Create Action in the Books Controller
91Edit C<lib/MyApp/Controller/Books.pm> and enter the following method:
93 =head2 url_create
fce83e5f 94
d442cc9f 95 Create a book with the supplied title, rating, and author
fce83e5f 96
d442cc9f 97 =cut
fce83e5f 98
f2bbfc36 99 sub url_create :Local {
55490817 100 # In addition to self & context, get the title, rating, &
101 # author_id args from the URL. Note that Catalyst automatically
102 # puts extra information after the "/<controller_name>/<action_name/"
fce83e5f 103 # into @_. The args are separated by the '/' char on the URL.
d442cc9f 104 my ($self, $c, $title, $rating, $author_id) = @_;
fce83e5f 105
55490817 106 # Call create() on the book model object. Pass the table
d442cc9f 107 # columns/field values we want to set as hash values
3b1fa91b 108 my $book = $c->model('DB::Book')->create({
d442cc9f 109 title => $title,
110 rating => $rating
111 });
fce83e5f 112
55490817 113 # Add a record to the join table for this book, mapping to
d442cc9f 114 # appropriate author
fce83e5f 115 $book->add_to_book_authors({author_id => $author_id});
d442cc9f 116 # Note: Above is a shortcut for this:
fce83e5f 117 # $book->create_related('book_authors', {author_id => $author_id});
0ed3df53 119 # Assign the Book object to the stash for display and set template
120 $c->stash(book => $book,
121 template => 'books/create_done.tt2');
d442cc9f 122 }
124Notice that Catalyst takes "extra slash-separated information" from the
125URL and passes it as arguments in C<@_>. The C<url_create> action then
126uses a simple call to the DBIC C<create> method to add the requested
127information to the database (with a separate call to
fce83e5f 128C<add_to_book_authors> to update the join table). As do virtually all
d442cc9f 129controller methods (at least the ones that directly handle user input),
130it then sets the template that should handle this request.
8a472b34 133=head2 Include a Template for the 'url_create' Action:
d442cc9f 134
135Edit C<root/src/books/create_done.tt2> and then enter:
137 [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%]
138 [% # Not a good idea for production use, though. :-) 'Indent=1' is -%]
139 [% # optional, but prevents "massive indenting" of deeply nested objects -%]
140 [% USE Dumper(Indent=1) -%]
fce83e5f 141
d442cc9f 142 [% # Set the page title. META can 'go back' and set values in templates -%]
143 [% # that have been processed 'before' this template (here it's for -%]
72609296 144 [% # root/lib/site/html and root/lib/site/header). Note that META only -%]
145 [% # works on simple/static strings (i.e. there is no variable -%]
146 [% # interpolation). -%]
d442cc9f 147 [% META title = 'Book Created' %]
fce83e5f 148
149 [% # Output information about the record that was added. First title. -%]
d442cc9f 150 <p>Added book '[% book.title %]'
fce83e5f 151
152 [% # Output the last name of the first author. -%]
153 by '[% book.authors.first.last_name %]'
d442cc9f 155 [% # Output the rating for the book that was added -%]
156 with a rating of [% book.rating %].</p>
fce83e5f 157
d442cc9f 158 [% # Provide a link back to the list page -%]
159 [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%]
8a7c5151 160 <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
fce83e5f 161
d442cc9f 162 [% # Try out the TT Dumper (for development only!) -%]
163 <pre>
164 Dump of the 'book' variable:
165 [% Dumper.dump(book) %]
166 </pre>
55490817 168The TT C<USE> directive allows access to a variety of plugin modules
169(TT plugins, that is, not Catalyst plugins) to add extra functionality
170to the base TT capabilities. Here, the plugin allows
171L<Data::Dumper|Data::Dumper> "pretty printing" of objects and
172variables. Other than that, the rest of the code should be familiar
4b4d3884 173from the examples in Chapter 3.
d442cc9f 174
fce83e5f 175Note: If you are using TT v2.15 you will need to change the code that
176outputs the "last name for the first author" above to match this:
178 [% authors = book.authors %]
179 by '[% authors.first.last_name IF authors.first;
180 authors.list.first.value.last_name IF ! authors.first %]'
182to get around an issue in TT v2.15 where blessed hash objects were not
183handled correctly. But, if you are still using v2.15, it's probably
f2bbfc36 184time to upgrade (v2.15 is almost 4 years old). If you are following
444d6b27 185along in Debian, then you should be on at least v2.20. You can test
186your version of Template Toolkit with the following:
fce83e5f 187
188 perl -MTemplate -e 'print "$Template::VERSION\n"'
d442cc9f 190
8a472b34 191=head2 Try the 'url_create' Feature
d442cc9f 192
f2bbfc36 193Make sure the development server is running with the "-r" restart
d442cc9f 195
f2bbfc36 196 $ DBIC_TRACE=1 script/myapp_server.pl -r
d442cc9f 197
198Note that new path for C</books/url_create> appears in the startup debug
d442cc9f 201Next, use your browser to enter the following URL:
203 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
55490817 205Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by
206'Stevens' with a rating of 5." along with a dump of the new book model
207object as it was returned by DBIC. You should also see the following
208DBIC debug messages displayed in the development server log messages
fbbb9084 209if you have DBIC_TRACE set:
d442cc9f 210
3b1fa91b 211 INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
212 INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6'
d442cc9f 213
214The C<INSERT> statements are obviously adding the book and linking it to
215the existing record for Richard Stevens. The C<SELECT> statement results
216from DBIC automatically fetching the book for the C<Dumper.dump(book)>.
fce83e5f 218If you then click the "Return to list" link, you should find that
219there are now six books shown (if necessary, Shift+Reload or
220Ctrl+Reload your browser at the C</books/list> page). You should now
221see the six DBIC debug messages similar to the following (where
3b1fa91b 223
a467a714 224 SELECT author.id, author.first_name, author.last_name
225 FROM book_author me JOIN author author
fce83e5f 226 ON author.id = me.author_id WHERE ( me.book_id = ? ): 'N'
d442cc9f 228
89d3dae9 229=head1 CONVERT TO A CHAINED ACTION
55490817 231Although the example above uses the same C<Local> action type for the
4b4d3884 232method that we saw in the previous chapter of the tutorial, there is an
55490817 233alternate approach that allows us to be more specific while also
234paving the way for more advanced capabilities. Change the method
235declaration for C<url_create> in C<lib/MyApp/Controller/Books.pm> you
89d3dae9 236entered above to match the following:
238 sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
fce83e5f 239 # In addition to self & context, get the title, rating, &
240 # author_id args from the URL. Note that Catalyst automatically
241 # puts the first 3 arguments worth of extra information after the
242 # "/<controller_name>/<action_name/" into @_ because we specified
243 # "Args(3)". The args are separated by the '/' char on the URL.
244 my ($self, $c, $title, $rating, $author_id) = @_;
246 ...
89d3dae9 247
55490817 248This converts the method to take advantage of the Chained
72609296 249action/dispatch type. Chaining lets you have a single URL
55490817 250automatically dispatch to several controller methods, each of which
251can have precise control over the number of arguments that it will
89d3dae9 252receive. A chain can essentially be thought of having three parts --
72609296 253a beginning, a middle, and an end. The bullets below summarize the key
89d3dae9 254points behind each of these parts of a chain:
257=over 4
260=item *
264=over 4
266=item *
268B<Use "C<:Chained('/')>" to start a chain>
270=item *
272Get arguments through C<CaptureArgs()>
274=item *
276Specify the path to match with C<PathPart()>
281=item *
285=over 4
287=item *
d442cc9f 288
89d3dae9 289Link to previous part of the chain with C<:Chained('_name_')>
291=item *
293Get arguments through C<CaptureArgs()>
295=item *
297Specify the path to match with C<PathPart()>
302=item *
306=over 4
308=item *
310Link to previous part of the chain with C<:Chained('_name_')>
312=item *
314B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain>
316=item *
318Specify the path to match with C<PathPart()>
72609296 325In our C<url_create> method above, we have combined all three parts into
326a single method: C<:Chained('/')> to start the chain,
327C<:PathPart('books/url_create')> to specify the base URL to match, and
328C<:Args(3)> to capture exactly three arguments and to end the chain.
89d3dae9 329
55490817 330As we will see shortly, a chain can consist of as many "links" as you
331wish, with each part capturing some arguments and doing some work
332along the way. We will continue to use the Chained action type in this
4b4d3884 333chapter of the tutorial and explore slightly more advanced capabilities
55490817 334with the base method and delete feature below. But Chained dispatch
335is capable of far more. For additional information, see
336L<Catalyst::Manual::Intro/Action types>,
72609296 338and the 2006 Advent calendar entry on the subject:
89d3dae9 339L<http://www.catalystframework.org/calendar/2006/10>.
342=head2 Try the Chained Action
55490817 344If you look back at the development server startup logs from your
345initial version of the C<url_create> method (the one using the
89d3dae9 346C<:Local> attribute), you will notice that it produced output similar
347to the following:
fbbb9084 349 [debug] Loaded Path actions:
350 .-------------------------------------+--------------------------------------.
351 | Path | Private |
352 +-------------------------------------+--------------------------------------+
353 | / | /default |
354 | / | /index |
355 | /books | /books/index |
356 | /books/list | /books/list |
357 | /books/url_create | /books/url_create |
358 '-------------------------------------+--------------------------------------'
89d3dae9 359
6961c906 360When the development server restarts, the debug output should change
361to something along the lines of the following:
89d3dae9 362
fbbb9084 363 [debug] Loaded Path actions:
364 .-------------------------------------+--------------------------------------.
365 | Path | Private |
366 +-------------------------------------+--------------------------------------+
367 | / | /default |
368 | / | /index |
369 | /books | /books/index |
370 | /books/list | /books/list |
371 '-------------------------------------+--------------------------------------'
fce83e5f 372
fbbb9084 373 [debug] Loaded Chained actions:
374 .-------------------------------------+--------------------------------------.
375 | Path Spec | Private |
376 +-------------------------------------+--------------------------------------+
377 | /books/url_create/*/*/* | /books/url_create |
378 '-------------------------------------+--------------------------------------'
89d3dae9 379
55490817 380C<url_create> has disappeared form the "Loaded Path actions" section
381but it now shows up under the newly created "Loaded Chained actions"
72609296 382section. And the "/*/*/*" portion clearly shows our requirement for
fbbb9084 383three arguments.
89d3dae9 384
55490817 385As with our non-chained version of C<url_create>, use your browser to
89d3dae9 386enter the following URL:
fbbb9084 388 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
89d3dae9 389
55490817 390You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
391'Stevens' with a rating of 5." along with a dump of the new book model
72609296 392object. Click the "Return to list" link, and you should find that there
393are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>).
89d3dae9 394
8a472b34 396=head2 Refactor to Use a 'base' Method to Start the Chains
89d3dae9 397
55490817 398Let's make a quick update to our initial Chained action to show a
399little more of the power of chaining. First, open
89d3dae9 400C<lib/MyApp/Controller/Books.pm> in your editor and add the following
fbbb9084 403 =head2 base
fce83e5f 404
fbbb9084 405 Can place common logic to start chained dispatch here
fce83e5f 406
fbbb9084 407 =cut
fce83e5f 408
fbbb9084 409 sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
410 my ($self, $c) = @_;
fce83e5f 411
1cde0fd6 412 # Store the ResultSet in stash so it's available for other methods
0ed3df53 413 $c->stash(resultset => $c->model('DB::Book'));
fce83e5f 414
fbbb9084 415 # Print a message to the debug log
416 $c->log->debug('*** INSIDE BASE METHOD ***');
417 }
55490817 419Here we print a log message and store the DBIC ResultSet in
420C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available
421for other actions that chain off C<base>. If your controller always
72609296 422needs a book ID as its first argument, you could have the base method
55490817 423capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
424book object with C<-E<gt>find($id)> and leave it in the stash for
425later parts of your chains to then act upon. Because we have several
994b66ad 426actions that don't need to retrieve a book (such as the C<url_create>
427we are working with now), we will instead add that functionality
428to a common C<object> action shortly.
55490817 430As for C<url_create>, let's modify it to first dispatch to C<base>.
431Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for
994b66ad 432C<url_create> to match the following:
89d3dae9 433
434 sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
f2bbfc36 436Once you save C<lib/MyApp/Controller/Books.pm>, notice that the
437development server will restart and our "Loaded Chained actions" section
438will changed slightly:
55490817 439
fbbb9084 440 [debug] Loaded Chained actions:
441 .-------------------------------------+--------------------------------------.
442 | Path Spec | Private |
443 +-------------------------------------+--------------------------------------+
444 | /books/url_create/*/*/* | /books/base (0) |
445 | | => /books/url_create |
446 '-------------------------------------+--------------------------------------'
89d3dae9 447
fce83e5f 448The "Path Spec" is the same, but now it maps to two Private actions as
449we would expect. The C<base> method is being triggered by the
450C</books> part of the URL. However, the processing then continues to
451the C<url_create> method because this method "chained" off C<base> and
452specified C<:PathPart('url_create')> (note that we could have omitted
453the "PathPart" here because it matches the name of the method, but we
444d6b27 454will include it to make the logic as explicit as possible).
89d3dae9 455
456Once again, enter the following URL into your browser:
fbbb9084 458 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
89d3dae9 459
fce83e5f 460The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
461rating of 5." message and a dump of the new book object should appear.
462Also notice the extra "INSIDE BASE METHOD" debug message in the
463development server output from the C<base> method. Click the "Return
464to list" link, and you should find that there are now eight books
465shown. (You may have a larger number of books if you repeated any of
466the "create" actions more than once. Don't worry about it as long as
467the number of books is appropriate for the number of times you added
468new books... there should be the original five books added via
469C<myapp01.sql> plus one additional book for each time you ran one
470of the url_create variations above.)
d442cc9f 471
475Although the C<url_create> action in the previous step does begin to
476reveal the power and flexibility of both Catalyst and DBIC, it's
477obviously not a very realistic example of how users should be expected
478to enter data. This section begins to address that concern.
481=head2 Add Method to Display The Form
483Edit C<lib/MyApp/Controller/Books.pm> 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 $c->stash(template => 'books/form_create.tt2');
d442cc9f 496 }
72609296 498This action simply invokes a view containing a form to create a book.
d442cc9f 499
1390ef0e 500
d442cc9f 501=head2 Add a Template for the Form
503Open C<root/src/books/form_create.tt2> in your editor and enter:
505 [% META title = 'Manual Form Book Create' -%]
444d6b27 506
8a7c5151 507 <form method="post" action="[% c.uri_for('form_create_do') %]">
d442cc9f 508 <table>
509 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
510 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
511 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
512 </table>
513 <input type="submit" name="Submit" value="Submit">
514 </form>
516Note that we have specified the target of the form data as
517C<form_create_do>, the method created in the section that follows.
1390ef0e 519
d442cc9f 520=head2 Add a Method to Process Form Values and Update Database
522Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
523save the form information to the database:
525 =head2 form_create_do
fce83e5f 526
d442cc9f 527 Take information from form and add to database
fce83e5f 528
d442cc9f 529 =cut
fce83e5f 530
89d3dae9 531 sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
d442cc9f 532 my ($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});
d442cc9f 549 # Avoid Data::Dumper issue mentioned earlier
55490817 550 # You can probably omit this
d442cc9f 551 $Data::Dumper::Useperl = 1;
fce83e5f 552
0ed3df53 553 # Store new model object in stash and set template
554 $c->stash(book => $book,
555 template => 'books/create_done.tt2');
d442cc9f 556 }
559=head2 Test Out The Form
55490817 561Notice that the server startup log reflects the two new chained
89d3dae9 562methods that we added:
fbbb9084 564 [debug] Loaded Chained actions:
565 .-------------------------------------+--------------------------------------.
566 | Path Spec | Private |
567 +-------------------------------------+--------------------------------------+
568 | /books/form_create | /books/base (0) |
569 | | => /books/form_create |
570 | /books/form_create_do | /books/base (0) |
571 | | => /books/form_create_do |
572 | /books/url_create/*/*/* | /books/base (0) |
573 | | => /books/url_create |
574 '-------------------------------------+--------------------------------------'
89d3dae9 575
d442cc9f 576Point your browser to L<http://localhost:3000/books/form_create> and
577enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
1390ef0e 578author ID of 4. You should then see the output of the same
d442cc9f 579C<create_done.tt2> template seen in earlier examples. Finally, click
580"Return to list" to view the full list of books.
582B<Note:> Having the user enter the primary key ID for the author is
fce83e5f 583obviously crude; we will address this concern with a drop-down list and
584add validation to our forms in Chapter 9.
d442cc9f 585
72609296 589Turning our attention to the Delete portion of CRUD, this section
d442cc9f 590illustrates some basic techniques that can be used to remove information
591from the database.
594=head2 Include a Delete Link in the List
1cde0fd6 596Edit C<root/src/books/list.tt2> and update it to match the following (two
d442cc9f 597sections have changed: 1) the additional '<th>Links</th>' table header,
72609296 598and 2) the four lines for the Delete link near the bottom):
d442cc9f 599
600 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
601 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
602 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
603 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
fce83e5f 604
28c32bc6 605 [% # Provide a title -%]
d442cc9f 606 [% META title = 'Book List' -%]
fce83e5f 607
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 -%]
612 <tr>
613 <td>[% book.title %]</td>
614 <td>[% book.rating %]</td>
615 <td>
fce83e5f 616 [% # NOTE: See "Exploring The Power of DBIC" for a better way to do this! -%]
d442cc9f 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 -%]
55490817 619 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
d442cc9f 620 [% # a value, so nothing will be printed here. But, if you have something -%]
55490817 621 [% # in TT that does return a value and you don't want it printed, you can -%]
6d97b973 622 [% # 1) assign it to a bogus value, or -%]
623 [% # 2) use the CALL keyword to call it and discard the return value. -%]
d442cc9f 624 [% tt_authors = [ ];
fce83e5f 625 tt_authors.push(author.last_name) FOREACH author = book.authors %]
d442cc9f 626 [% # Now use a TT 'virtual method' to display the author count in parens -%]
3b1fa91b 627 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
628 ([% tt_authors.size | html %])
d442cc9f 629 [% # Use another TT vmethod to join & print the names & comma separators -%]
3b1fa91b 630 [% tt_authors.join(', ') | html %]
d442cc9f 631 </td>
632 <td>
633 [% # Add a link to delete a book %]
e075db0c 634 <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">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
642will be used instead of full HTML buttons; in practice, anything that
fce83e5f 643modifies data should be handled with a form sending a POST request).
fe01b24f 644
55490817 645Also notice that we are using a more advanced form of C<uri_for> than
646we have seen before. Here we use
647C<$c-E<gt>controller-E<gt>action_for> to automatically generate a URI
648appropriate for that action based on the method we want to link to
649while inserting the C<book.id> value into the appropriate place. Now,
650if you ever change C<:PathPart('delete')> in your controller method to
651C<:PathPart('kill')>, then your links will automatically update
652without any changes to your .tt2 template file. As long as the name
72609296 653of your method does not change (here, "delete"), then your links will
55490817 654still be correct. There are a few shortcuts and options when using
0416017e 655C<action_for()>:
657=over 4
659=item *
661If you are referring to a method in the current controller, you can
662use C<$self-E<gt>action_for('_method_name_')>.
664=item *
666If you are referring to a method in a different controller, you need
fbbb9084 667to include that controller's name as an argument to C<controller()>, as in
0416017e 668C<$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
55490817 679As mentioned earlier, since we have a mixture of actions that operate
680on a single book ID and others that do not, we should not have C<base>
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
683because that logic does not belong in C<base> doesn't mean that we
684can't create another location to centralize the book lookup code. In
685our case, we will create a method called C<object> that will store the
686specific book in the stash. Chains that always operate on a single
687existing book can chain off this method, but methods such as
688C<url_create> that don't operate on an existing book can chain
fbbb9084 689directly off base.
994b66ad 690
691To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm>
692and add the following code:
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 }
717Now, any other method that chains off C<object> will automatically
55490817 718have the appropriate book waiting for it in
acbd7bdd 719C<$c-E<gt>stash-E<gt>{object}>.
994b66ad 720
994b66ad 721
d442cc9f 722=head2 Add a Delete Action to the Controller
724Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
725following method:
1390ef0e 727 =head2 delete
fce83e5f 728
d442cc9f 729 Delete a book
fce83e5f 730
d442cc9f 731 =cut
fce83e5f 732
994b66ad 733 sub delete :Chained('object') :PathPart('delete') :Args(0) {
994b66ad 734 my ($self, $c) = @_;
fce83e5f 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;
fce83e5f 739
d442cc9f 740 # Set a status message to be displayed at the top of the view
741 $c->stash->{status_msg} = "Book deleted.";
fce83e5f 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.
748However, it also removes the corresponding entry from the
3b1fa91b 749C<book_author> table 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
f2bbfc36 764One you save the Books controller, the server should automatically restart.
765The C<delete> method should now appear in the "Loaded Chained actions" section
89d3dae9 766of the startup debug output:
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.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6'
790 DELETE FROM book WHERE ( id = ? ): '6'
791 SELECT me.book_id, me.author_id FROM book_author me WHERE ( me.book_id = ? ): '6'
792 DELETE FROM book_author WHERE ( author_id = ? AND book_id = ? ): '4', '6'
d442cc9f 793
795=head2 Fixing a Dangerous URL
55490817 797Note the URL in your browser once you have performed the deletion in the
d442cc9f 798prior step -- it is still referencing the delete action:
acbd7bdd 800 http://localhost:3000/books/id/6/delete
d442cc9f 801
55490817 802What if the user were to press reload with this URL still active? In
803this case the redundant delete is harmless (although it does generate
804an exception screen, it doesn't perform any undesirable actions on the
805application or database), but in other cases this could clearly be
fbbb9084 806extremely dangerous.
d442cc9f 807
808We can improve the logic by converting to a redirect. Unlike
809C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform
810a server-side alteration in the flow of processing, a redirect is a
3533daff 811client-side mechanism that causes the browser to issue an entirely
d442cc9f 812new request. As a result, the URL in the browser is updated to match
813the destination of the redirection URL.
815To convert the forward used in the previous section to a redirect,
55490817 816open C<lib/MyApp/Controller/Books.pm> and edit the existing
d442cc9f 817C<sub delete> method to match:
994b66ad 819 =head2 delete
fce83e5f 820
d442cc9f 821 Delete a book
fce83e5f 822
d442cc9f 823 =cut
fce83e5f 824
994b66ad 825 sub delete :Chained('object') :PathPart('delete') :Args(0) {
fbbb9084 826 my ($self, $c) = @_;
fce83e5f 827
994b66ad 828 # Use the book object saved by 'object' and delete it along
3b1fa91b 829 # with related 'book_author' entries
994b66ad 830 $c->stash->{object}->delete;
fce83e5f 831
d442cc9f 832 # Set a status message to be displayed at the top of the view
833 $c->stash->{status_msg} = "Book deleted.";
fce83e5f 834
0416017e 835 # Redirect the user back to the list page. Note the use
836 # of $self->action_for as earlier in this section (BasicCRUD)
fbbb9084 837 $c->response->redirect($c->uri_for($self->action_for('list')));
d442cc9f 838 }
841=head2 Try the Delete and Redirect Logic
f2bbfc36 843Point your browser to L<http://localhost:3000/books/list> (don't just
844hit "Refresh" in your browser since we left the URL in an invalid state
845in the previous section!) and delete the first copy of the remaining two
846"TCPIP_Illustrated_Vol-2" books. The URL in your browser should return
847to the L<http://localhost:3000/books/list> URL, so that is an
848improvement, but notice that I<no green "Book deleted" status message is
849displayed>. Because the stash is reset on every request (and a redirect
850involves a second request), the C<status_msg> is cleared before it can
851be displayed.
d442cc9f 852
8a472b34 854=head2 Using 'uri_for' to Pass Query Parameters
d442cc9f 855
4b4d3884 856There are several ways to pass information across a redirect. One
857option is to use the C<flash> technique that we will see in Chapter 5
72609296 858of this tutorial; however, here we will pass the information via query
4b4d3884 859parameters on the redirect itself. Open
860C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete>
89d3dae9 861method to match the following:
d442cc9f 862
55490817 863 =head2 delete
fce83e5f 864
d442cc9f 865 Delete a book
fce83e5f 866
d442cc9f 867 =cut
fce83e5f 868
994b66ad 869 sub delete :Chained('object') :PathPart('delete') :Args(0) {
fbbb9084 870 my ($self, $c) = @_;
fce83e5f 871
994b66ad 872 # Use the book object saved by 'object' and delete it along
3b1fa91b 873 # with related 'book_author' entries
994b66ad 874 $c->stash->{object}->delete;
fce83e5f 875
d442cc9f 876 # Redirect the user back to the list page with status msg as an arg
55490817 877 $c->response->redirect($c->uri_for($self->action_for('list'),
d442cc9f 878 {status_msg => "Book deleted."}));
879 }
881This modification simply leverages the ability of C<uri_for> to include
55490817 882an arbitrary number of name/value pairs in a hash reference. Next, we
883need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a
d442cc9f 884query parameter:
1390ef0e 886 ...
d442cc9f 887 <div id="content">
1390ef0e 888 [%# Status and error messages %]
889 <span class="message">[% status_msg || c.request.params.status_msg %]</span>
890 <span class="error">[% error_msg %]</span>
891 [%# This is where TT will stick all of your template's contents. -%]
892 [% content %]
893 </div><!-- end content -->
894 ...
55490817 896Although the sample above only shows the C<content> div, leave the
1390ef0e 897rest of the file intact -- the only change we made to the C<wrapper.tt2>
55490817 898was to add "C<|| c.request.params.status_msg>" to the
1390ef0e 899C<E<lt>span class="message"E<gt>> line.
d442cc9f 900
902=head2 Try the Delete and Redirect With Query Param Logic
f2bbfc36 904Point your browser to L<http://localhost:3000/books/list> (you should
905now be able to safely hit "refresh" in your browser). Then delete the
906remaining copy of "TCPIP_Illustrated_Vol-2". The green "Book deleted"
a608d8ce 907status message should return. But notice that you can now hit the
908"Reload" button in your browser and it just redisplays the book
909list (and it correctly shows it without the "Book deleted" message
910on redisplay).
d442cc9f 911
55490817 912B<NOTE:> Another popular method for maintaining server-side
913information across a redirect is to use the C<flash> technique we
4b4d3884 914discuss in the next chapter of the tutorial,
3ab6187c 915L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>. While
55490817 916C<flash> is a "slicker" mechanism in that it's all handled by the
917server and doesn't "pollute" your URLs, B<it is important to note that
918C<flash> can lead to situations where the wrong information shows up
919in the wrong browser window if the user has multiple windows or
72609296 920browser tabs open>. For example, Window A causes something to be
55490817 921placed in the stash, but before that window performs a redirect,
922Window B makes a request to the server and gets the status information
994b66ad 923that should really go to Window A. For this reason, you may wish
89d3dae9 924to use the "query param" technique shown here in your applications.
d442cc9f 925
1cde0fd6 927=head1 EXPLORING THE POWER OF DBIC
55490817 929In this section we will explore some additional capabilities offered
930by DBIx::Class. Although these features have relatively little to do
931with Catalyst per se, you will almost certainly want to take advantage
1cde0fd6 932of them in your applications.
1cde0fd6 935=head2 Add Datetime Columns to Our Existing Books Table
55490817 937Let's add two columns to our existing C<books> table to track when
1cde0fd6 938each book was added and when each book is updated:
940 $ sqlite3 myapp.db
3b1fa91b 941 sqlite> ALTER TABLE book ADD created INTEGER;
942 sqlite> ALTER TABLE book ADD updated INTEGER;
943 sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
944 sqlite> SELECT * FROM book;
f2bbfc36 945 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
946 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
947 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
948 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
949 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
950 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1cde0fd6 951 sqlite> .quit
952 $
954This will modify the C<books> table to include the two new fields
955and populate those fields with the current time.
acbd7bdd 957
a46b474e 958=head2 Update DBIx::Class to Automatically Handle the Datetime Columns
1cde0fd6 959
960Next, we should re-run the DBIC helper to update the Result Classes
961with the new fields:
963 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
b66dd084 964 create=static components=TimeStamp dbi:SQLite:myapp.db \
965 on_connect_do="PRAGMA foreign_keys = ON"
1cde0fd6 966 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
967 exists "/root/dev/MyApp/script/../t"
968 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
969 Schema dump completed.
970 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
972Notice that we modified our use of the helper slightly: we told
d05dbc42 973it to include the L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp>
1cde0fd6 974in the C<load_components> line of the Result Classes.
f2bbfc36 976If you open C<lib/MyApp/Schema/Result/Book.pm> in your editor you should
977see that the C<created> and C<updated> fields are now included in the
978call to C<add_columns()>. However, also notice that the C<many_to_many>
979relationships we manually added below the "C<# DO NOT MODIFY...>" line
980were automatically preserved.
1cde0fd6 981
55490817 982While we have this file open, let's update it with some additional
983information to have DBIC automatically handle the updating of these
984two fields for us. Insert the following code at the bottom of the
985file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and
1cde0fd6 986B<above> the C<1;> on the last line):
988 #
989 # Enable automatic date handling
990 #
991 __PACKAGE__->add_columns(
992 "created",
993 { data_type => 'datetime', set_on_create => 1 },
994 "updated",
995 { data_type => 'datetime', set_on_create => 1, set_on_update => 1 },
55490817 996 );
1cde0fd6 997
a46b474e 998This will override the definition for these fields that Schema::Loader
999placed at the top of the file. The C<set_on_create> and
1000C<set_on_update> options will cause DBIx::Class to automatically
1001update the timestamps in these columns whenever a row is created or
1cde0fd6 1003
1cde0fd6 1004Then enter the following URL into your web browser:
1006 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
1008You should get the same "Book Created" screen we saw above. However,
1009if you now use the sqlite3 command-line tool to dump the C<books> table,
1010you will see that the new book we added has an appropriate date and
1011time entered for it (see the last line in the listing below):
444d6b27 1013 $ sqlite3 myapp.db "select * from book"
f2bbfc36 1014 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1015 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1016 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
1017 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1018 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1019 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1020 10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42
a608d8ce 1021 sqlite> .q
1cde0fd6 1022
55490817 1023Notice in the debug log that the SQL DBIC generated has changed to
1cde0fd6 1024incorporate the datetime logic:
2a6eb5f9 1026 INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ):
f2bbfc36 1027 '2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42'
2a6eb5f9 1028 INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10'
1cde0fd6 1029
1031=head2 Create a ResultSet Class
444d6b27 1033An often overlooked but extremely powerful features of DBIC is that it
55490817 1034allows you to supply your own subclasses of C<DBIx::Class::ResultSet>.
1035It allows you to pull complex and unsightly "query code" out of your
1cde0fd6 1036controllers and encapsulate it in a method of your ResultSet Class.
1037These "canned queries" in your ResultSet Class can then be invoked
1038via a single call, resulting in much cleaner and easier to read
1039controller code.
55490817 1041To illustrate the concept with a fairly simple example, let's create a
1cde0fd6 1042method that returns books added in the last 10 minutes. Start by
a46b474e 1043making a directory where DBIx::Class will look for our ResultSet Class:
1cde0fd6 1044
444d6b27 1045 $ mkdir lib/MyApp/Schema/ResultSet
1cde0fd6 1046
3b1fa91b 1047Then open C<lib/MyApp/Schema/ResultSet/Book.pm> and enter the following:
1cde0fd6 1048
3b1fa91b 1049 package MyApp::Schema::ResultSet::Book;
fce83e5f 1050
1cde0fd6 1051 use strict;
1052 use warnings;
1053 use base 'DBIx::Class::ResultSet';
fce83e5f 1054
1cde0fd6 1055 =head2 created_after
fce83e5f 1056
1cde0fd6 1057 A predefined search for recently added books
fce83e5f 1058
1cde0fd6 1059 =cut
fce83e5f 1060
1cde0fd6 1061 sub created_after {
fadc4ae7 1062 my ($self, $datetime) = @_;
fce83e5f 1063
b66dd084 1064 my $date_str = $self->result_source->schema->storage
fadc4ae7 1065 ->datetime_parser->format_datetime($datetime);
fce83e5f 1066
fadc4ae7 1067 return $self->search({
1068 created => { '>' => $date_str }
1069 });
1cde0fd6 1070 }
fce83e5f 1071
1cde0fd6 1072 1;
1cde0fd6 1074Then add the following method to the C<lib/MyApp/Controller/Books.pm>:
1076 =head2 list_recent
fce83e5f 1077
1cde0fd6 1078 List recently created books
fce83e5f 1079
1cde0fd6 1080 =cut
fce83e5f 1081
1cde0fd6 1082 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
1083 my ($self, $c, $mins) = @_;
fce83e5f 1084
1cde0fd6 1085 # Retrieve all of the book records as book model objects and store in the
1086 # stash where they can be accessed by the TT template, but only
1087 # retrieve books created within the last $min number of minutes
0ed3df53 1088 $c->stash(books => [$c->model('DB::Book')
1089 ->created_after(DateTime->now->subtract(minutes => $mins))]);
fce83e5f 1090
1cde0fd6 1091 # Set the TT template to use. You will almost always want to do this
1092 # in your action methods (action methods respond to user input in
1093 # your controllers).
0ed3df53 1094 $c->stash(template => 'books/list.tt2');
1cde0fd6 1095 }
f2bbfc36 1097Now try different values for the "minutes" argument (the final number
1098value) using the URL C<http://localhost:3000/books/list_recent/_#_> in
1099your browser. For example, this would list all books added in the last
1100fifteen minutes:
1cde0fd6 1101
1102 http://localhost:3000/books/list_recent/15
1104Depending on how recently you added books, you might want to
a608d8ce 1105try a higher or lower value for the minutes.
1cde0fd6 1106
1108=head2 Chaining ResultSets
a46b474e 1110One of the most helpful and powerful features in DBIx::Class is that
1111it allows you to "chain together" a series of queries (note that this
1112has nothing to do with the "Chained Dispatch" for Catalyst that we
1113were discussing above). Because each ResultSet returns another
1114ResultSet, you can take an initial query and immediately feed that
1115into a second query (and so on for as many queries you need). Note
1116that no matter how many ResultSets you chain together, the database
1117itself will not be hit until you use a method that attempts to access
1118the data. And, because this technique carries over to the ResultSet
1119Class feature we implemented in the previous section for our "canned
1120search", we can combine the two capabilities. For example, let's add
1121an action to our C<Books> controller that lists books that are both
1122recent I<and> have "TCP" in the title. Open up
1123C<lib/MyApp/Controller/Books.pm> and add the following method:
1cde0fd6 1124
acbd7bdd 1125 =head2 list_recent_tcp
fce83e5f 1126
1cde0fd6 1127 List recently created books
fce83e5f 1128
1cde0fd6 1129 =cut
fce83e5f 1130
1cde0fd6 1131 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1132 my ($self, $c, $mins) = @_;
fce83e5f 1133
1cde0fd6 1134 # Retrieve all of the book records as book model objects and store in the
1135 # stash where they can be accessed by the TT template, but only
1136 # retrieve books created within the last $min number of minutes
1137 # AND that have 'TCP' in the title
0ed3df53 1138 $c->stash(books => [$c->model('DB::Book')
1cde0fd6 1139 ->created_after(DateTime->now->subtract(minutes => $mins))
1140 ->search({title => {'like', '%TCP%'}})
0ed3df53 1141 ]);
fce83e5f 1142
1cde0fd6 1143 # Set the TT template to use. You will almost always want to do this
1144 # in your action methods (action methods respond to user input in
1145 # your controllers).
0ed3df53 1146 $c->stash(template => 'books/list.tt2');
1cde0fd6 1147 }
f2bbfc36 1149To try this out, enter the following URL into your browser:
1cde0fd6 1150
1151 http://localhost:3000/books/list_recent_tcp/100
55490817 1153And you should get a list of books added in the last 100 minutes that
1154contain the string "TCP" in the title. However, if you look at all
1155books within the last 100 minutes, you should get a longer list
1156(again, you might have to adjust the number of minutes depending on
1cde0fd6 1157how recently you added books to your database):
1159 http://localhost:3000/books/list_recent/100
55490817 1161Take a look at the DBIC_TRACE output in the development server log for
1cde0fd6 1162the first URL and you should see something similar to the following:
fce83e5f 1164 SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me
f2bbfc36 1165 WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32'
1cde0fd6 1166
55490817 1167However, let's not pollute our controller code with this raw "TCP"
1168query -- it would be cleaner to encapsulate that code in a method on
1169our ResultSet Class. To do this, open
3b1fa91b 1170C<lib/MyApp/Schema/ResultSet/Book.pm> and add the following method:
1cde0fd6 1171
1172 =head2 title_like
fce83e5f 1173
1cde0fd6 1174 A predefined search for books with a 'LIKE' search in the string
fce83e5f 1175
1cde0fd6 1176 =cut
fce83e5f 1177
1cde0fd6 1178 sub title_like {
fadc4ae7 1179 my ($self, $title_str) = @_;
fce83e5f 1180
fadc4ae7 1181 return $self->search({
1182 title => { 'like' => "%$title_str%" }
1183 });
1cde0fd6 1184 }
55490817 1186We defined the search string as C<$title_str> to make the method more
1187flexible. Now update the C<list_recent_tcp> method in
1188C<lib/MyApp/Controller/Books.pm> to match the following (we have
1189replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line
1cde0fd6 1190shown here -- the rest of the method should be the same):
1192 =head2 list_recent_tcp
fce83e5f 1193
1cde0fd6 1194 List recently created books
fce83e5f 1195
1cde0fd6 1196 =cut
fce83e5f 1197
1cde0fd6 1198 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1199 my ($self, $c, $mins) = @_;
fce83e5f 1200
1cde0fd6 1201 # Retrieve all of the book records as book model objects and store in the
1202 # stash where they can be accessed by the TT template, but only
1203 # retrieve books created within the last $min number of minutes
1204 # AND that have 'TCP' in the title
0ed3df53 1205 $c->stash(books => [$c->model('DB::Book')
1cde0fd6 1206 ->created_after(DateTime->now->subtract(minutes => $mins))
1207 ->title_like('TCP')
0ed3df53 1208 ]);
fce83e5f 1209
1cde0fd6 1210 # Set the TT template to use. You will almost always want to do this
1211 # in your action methods (action methods respond to user input in
1212 # your controllers).
0ed3df53 1213 $c->stash(template => 'books/list.tt2');
1cde0fd6 1214 }
f2bbfc36 1216Try out the C<list_recent_tcp> and C<list_recent> URLs as we did above.
1217They should work just the same, but our code is obviously cleaner and
1218more modular, while also being more flexible at the same time.
1cde0fd6 1219
1221=head2 Adding Methods to Result Classes
a46b474e 1223In the previous two sections we saw a good example of how we could use
1224DBIx::Class ResultSet Classes to clean up our code for an entire query
1225(for example, our "canned searches" that filtered the entire query).
1226We can do a similar improvement when working with individual rows as
1227well. Whereas the ResultSet construct is used in DBIC to correspond
1228to an entire query, the Result Class construct is used to represent a
1229row. Therefore, we can add row-specific "helper methods" to our Result
1230Classes stored in C<lib/MyApp/Schema/Result/>. For example, open
3b1fa91b 1231C<lib/MyApp/Schema/Result/Author.pm> and add the following method (as
a46b474e 1232always, it must be above the closing "C<1;>"):
1cde0fd6 1233
1234 #
a608d8ce 1235 # Row-level helper methods
1cde0fd6 1236 #
1237 sub full_name {
1238 my ($self) = @_;
fce83e5f 1239
1cde0fd6 1240 return $self->first_name . ' ' . $self->last_name;
1241 }
55490817 1243This will allow us to conveniently retrieve both the first and last
1244name for an author in one shot. Now open C<root/src/books/list.tt2>
1cde0fd6 1245and change the definition of C<tt_authors> from this:
acbd7bdd 1247 ...
1cde0fd6 1248 [% tt_authors = [ ];
fce83e5f 1249 tt_authors.push(author.last_name) FOREACH author = book.authors %]
acbd7bdd 1250 ...
1cde0fd6 1251
acbd7bdd 1254 ...
1cde0fd6 1255 [% tt_authors = [ ];
fce83e5f 1256 tt_authors.push(author.full_name) FOREACH author = book.authors %]
acbd7bdd 1257 ...
1cde0fd6 1258
55490817 1259(Only C<author.last_name> was changed to C<author.full_name> -- the
1cde0fd6 1260rest of the file should remain the same.)
f2bbfc36 1262Now go to the standard book list URL:
1cde0fd6 1263
1264 http://localhost:3000/books/list
55490817 1266The "Author(s)" column will now contain both the first and last name.
1267And, because the concatenation logic was encapsulated inside our
444d6b27 1268Result Class, it keeps the code inside our TT template nice and clean
55490817 1269(remember, we want the templates to be as close to pure HTML markup as
1270possible). Obviously, this capability becomes even more useful as you
444d6b27 1271use to to remove even more complicated row-specific logic from your
1cde0fd6 1272templates!
fce83e5f 1275=head2 Moving Complicated View Code to the Model
1277The previous section illustrated how we could use a Result Class
1278method to print the full names of the authors without adding any extra
1279code to our view, but it still left us with a fairly ugly mess (see
1282 ...
1283 <td>
1284 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1285 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1286 [% # loop in 'side effect notation' to load just the last names of the -%]
1287 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1288 [% # a value, so nothing will be printed here. But, if you have something -%]
1289 [% # in TT that does return a method and you don't want it printed, you -%]
1290 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1291 [% # call it and discard the return value. -%]
1292 [% tt_authors = [ ];
1293 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1294 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1295 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1296 ([% tt_authors.size | html %])
1297 [% # Use another TT vmethod to join & print the names & comma separators -%]
1298 [% tt_authors.join(', ') | html %]
1299 </td>
1300 ...
1302Let's combine some of the techniques used earlier in this section to
1303clean this up. First, let's add a method to our Book Result Class to
1304return the number of authors for a book. Open
1305C<lib/MyApp/Schema/Result/Book.pm> and add the following method:
444d6b27 1307 =head2 author_count
1309 Return the number of authors for the current book
fce83e5f 1311 =cut
1313 sub author_count {
1314 my ($self) = @_;
1316 # Use the 'many_to_many' relationship to fetch all of the authors for the current
1317 # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT
1318 return $self->authors->count;
1319 }
1321Next, let's add a method to return a list of authors for a book to the
1322same C<lib/MyApp/Schema/Result/Book.pm> file:
1324 =head2 author_list
1326 Return a comma-separated list of authors for the current book
1328 =cut
1330 sub author_list {
1331 my ($self) = @_;
1333 # Loop through all authors for the current book, calling all the 'full_name'
1334 # Result Class method for each
1335 my @names;
1336 foreach my $author ($self->authors) {
1337 push(@names, $author->full_name);
1338 }
1340 return join(', ', @names);
1341 }
1343This method loops through each author, using the C<full_name> Result
1344Class method we added to C<lib/MyApp/Schema/Result/Author.pm> in the
1345prior section.
1347Using these two methods, we can simplify our TT code. Open
1348C<root/src/books/list.tt2> and update the "Author(s)" table cell to
1349match the following:
1351 ...
1352 <td>
1353 [% # Print count and author list using Result Class methods -%]
1354 ([% book.author_count | html %]) [% book.author_list | html %]
1355 </td>
1356 ...
1358Although most of the code we removed comprised comments, the overall
f2bbfc36 1359effect is dramatic... because our view code is so simple, we don't need
1360huge comments to clue people in to the gist of our code. The view code
1361is now self-documenting and readable enough that you could probably get
1362by with no comments at all. All of the "complex" work is being done in
1363our Result Class methods (and, because we have broken the code into
1364nice, modular chucks, the Result Class code is hardly something you
1365would call complex).
fce83e5f 1366
1367As we saw in this section, always strive to keep your view AND
1368controller code as simple as possible by pulling code out into your
1369model objects. Because DBIx::Class can be easily extended in so many
1370ways, it's an excellent to way accomplish this objective. It will
1371make your code cleaner, easier to write, less error-prone, and easier
1372to debug and maintain.
f2bbfc36 1374Before you conclude this section, hit Refresh in your browser... the
1375output should be the same even though the backend code has been trimmed
444d6b27 1377
fce83e5f 1378
d442cc9f 1379=head1 AUTHOR
1381Kennedy Clark, C<hkclark@gmail.com>
1383Please report any errors, issues or suggestions to the author. The
1384most recent version of the Catalyst Tutorial can be found at
59884771 1385L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
d442cc9f 1386
45c7830f 1387Copyright 2006-2008, Kennedy Clark, under Creative Commons License
95674086 1388(L<http://creativecommons.org/licenses/by-sa/3.0/us/>).