Initial set of tutorial edits to go along with depluralization update.
[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
71of tool to automate the process. You get less control, but it's quick
72and easy. For example, see
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/> 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
d442cc9f 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});
d442cc9f 119 # Assign the Book object to the stash for display in the view
120 $c->stash->{book} = $book;
fce83e5f 121
d442cc9f 122 # Set the TT template to use
123 $c->stash->{template} = 'books/create_done.tt2';
124 }
126Notice that Catalyst takes "extra slash-separated information" from the
127URL and passes it as arguments in C<@_>. The C<url_create> action then
128uses a simple call to the DBIC C<create> method to add the requested
129information to the database (with a separate call to
fce83e5f 130C<add_to_book_authors> to update the join table). As do virtually all
d442cc9f 131controller methods (at least the ones that directly handle user input),
132it then sets the template that should handle this request.
8a472b34 135=head2 Include a Template for the 'url_create' Action:
d442cc9f 136
137Edit C<root/src/books/create_done.tt2> and then enter:
139 [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%]
140 [% # Not a good idea for production use, though. :-) 'Indent=1' is -%]
141 [% # optional, but prevents "massive indenting" of deeply nested objects -%]
142 [% USE Dumper(Indent=1) -%]
fce83e5f 143
d442cc9f 144 [% # Set the page title. META can 'go back' and set values in templates -%]
145 [% # that have been processed 'before' this template (here it's for -%]
72609296 146 [% # root/lib/site/html and root/lib/site/header). Note that META only -%]
147 [% # works on simple/static strings (i.e. there is no variable -%]
148 [% # interpolation). -%]
d442cc9f 149 [% META title = 'Book Created' %]
fce83e5f 150
151 [% # Output information about the record that was added. First title. -%]
d442cc9f 152 <p>Added book '[% book.title %]'
fce83e5f 153
154 [% # Output the last name of the first author. -%]
155 by '[% book.authors.first.last_name %]'
d442cc9f 157 [% # Output the rating for the book that was added -%]
158 with a rating of [% book.rating %].</p>
fce83e5f 159
d442cc9f 160 [% # Provide a link back to the list page -%]
161 [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%]
8a7c5151 162 <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
fce83e5f 163
d442cc9f 164 [% # Try out the TT Dumper (for development only!) -%]
165 <pre>
166 Dump of the 'book' variable:
167 [% Dumper.dump(book) %]
168 </pre>
55490817 170The TT C<USE> directive allows access to a variety of plugin modules
171(TT plugins, that is, not Catalyst plugins) to add extra functionality
172to the base TT capabilities. Here, the plugin allows
173L<Data::Dumper|Data::Dumper> "pretty printing" of objects and
174variables. Other than that, the rest of the code should be familiar
4b4d3884 175from the examples in Chapter 3.
d442cc9f 176
fce83e5f 177Note: If you are using TT v2.15 you will need to change the code that
178outputs the "last name for the first author" above to match this:
180 [% authors = book.authors %]
181 by '[% authors.first.last_name IF authors.first;
182 authors.list.first.value.last_name IF ! authors.first %]'
184to get around an issue in TT v2.15 where blessed hash objects were not
185handled correctly. But, if you are still using v2.15, it's probably
186time to upgrade (v2.15 is exactly 3 years old on the day I'm typing
187this). If you are following along in Debian, then you should be on at
188least v2.20. You can test your version of Template Toolkit with the
191 perl -MTemplate -e 'print "$Template::VERSION\n"'
d442cc9f 193
8a472b34 194=head2 Try the 'url_create' Feature
d442cc9f 195
196If the application is still running from before, use C<Ctrl-C> to kill
197it. Then restart the server:
1390ef0e 199 $ DBIC_TRACE=1 script/
d442cc9f 200
201Note that new path for C</books/url_create> appears in the startup debug
204B<TIP>: You can use C<script/ -r> to have the development
205server auto-detect changed files and reload itself (if your browser acts
206odd, you should also try throwing in a C<-k>). If you make changes to
207the TT templates only, you do not need to reload the development server
208(only changes to "compiled code" such as Controller and Model C<.pm>
209files require a reload).
211Next, use your browser to enter the following URL:
213 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
55490817 215Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by
216'Stevens' with a rating of 5." along with a dump of the new book model
217object as it was returned by DBIC. You should also see the following
218DBIC debug messages displayed in the development server log messages
fbbb9084 219if you have DBIC_TRACE set:
d442cc9f 220
3b1fa91b 221 INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
222 INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6'
d442cc9f 223
224The C<INSERT> statements are obviously adding the book and linking it to
225the existing record for Richard Stevens. The C<SELECT> statement results
226from DBIC automatically fetching the book for the C<Dumper.dump(book)>.
fce83e5f 228If you then click the "Return to list" link, you should find that
229there are now six books shown (if necessary, Shift+Reload or
230Ctrl+Reload your browser at the C</books/list> page). You should now
231see the six DBIC debug messages similar to the following (where
3b1fa91b 233
234 SELECT, author.first_name, author.last_name \
235 FROM book_author me JOIN author author \
fce83e5f 236 ON = me.author_id WHERE ( me.book_id = ? ): 'N'
238(The '\' characters won't actually appear in the output -- we are
239using them as "line continuation markers" here.)
d442cc9f 240
d442cc9f 241
89d3dae9 242=head1 CONVERT TO A CHAINED ACTION
55490817 244Although the example above uses the same C<Local> action type for the
4b4d3884 245method that we saw in the previous chapter of the tutorial, there is an
55490817 246alternate approach that allows us to be more specific while also
247paving the way for more advanced capabilities. Change the method
248declaration for C<url_create> in C<lib/MyApp/Controller/> you
89d3dae9 249entered above to match the following:
251 sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
fce83e5f 252 # In addition to self & context, get the title, rating, &
253 # author_id args from the URL. Note that Catalyst automatically
254 # puts the first 3 arguments worth of extra information after the
255 # "/<controller_name>/<action_name/" into @_ because we specified
256 # "Args(3)". The args are separated by the '/' char on the URL.
257 my ($self, $c, $title, $rating, $author_id) = @_;
259 ...
89d3dae9 260
55490817 261This converts the method to take advantage of the Chained
72609296 262action/dispatch type. Chaining lets you have a single URL
55490817 263automatically dispatch to several controller methods, each of which
264can have precise control over the number of arguments that it will
89d3dae9 265receive. A chain can essentially be thought of having three parts --
72609296 266a beginning, a middle, and an end. The bullets below summarize the key
89d3dae9 267points behind each of these parts of a chain:
270=over 4
273=item *
277=over 4
279=item *
281B<Use "C<:Chained('/')>" to start a chain>
283=item *
285Get arguments through C<CaptureArgs()>
287=item *
289Specify the path to match with C<PathPart()>
294=item *
298=over 4
300=item *
d442cc9f 301
89d3dae9 302Link to previous part of the chain with C<:Chained('_name_')>
304=item *
306Get arguments through C<CaptureArgs()>
308=item *
310Specify the path to match with C<PathPart()>
315=item *
319=over 4
321=item *
323Link to previous part of the chain with C<:Chained('_name_')>
325=item *
327B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain>
329=item *
331Specify the path to match with C<PathPart()>
72609296 338In our C<url_create> method above, we have combined all three parts into
339a single method: C<:Chained('/')> to start the chain,
340C<:PathPart('books/url_create')> to specify the base URL to match, and
341C<:Args(3)> to capture exactly three arguments and to end the chain.
89d3dae9 342
55490817 343As we will see shortly, a chain can consist of as many "links" as you
344wish, with each part capturing some arguments and doing some work
345along the way. We will continue to use the Chained action type in this
4b4d3884 346chapter of the tutorial and explore slightly more advanced capabilities
55490817 347with the base method and delete feature below. But Chained dispatch
348is capable of far more. For additional information, see
349L<Catalyst::Manual::Intro/Action types>,
72609296 351and the 2006 Advent calendar entry on the subject:
89d3dae9 352L<>.
355=head2 Try the Chained Action
55490817 357If you look back at the development server startup logs from your
358initial version of the C<url_create> method (the one using the
89d3dae9 359C<:Local> attribute), you will notice that it produced output similar
360to the following:
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 | /books/url_create | /books/url_create |
371 '-------------------------------------+--------------------------------------'
89d3dae9 372
55490817 373Now start the development server with our basic chained method in
374place and the startup debug output should change to something along
89d3dae9 375the lines of the following:
fbbb9084 377 [debug] Loaded Path actions:
378 .-------------------------------------+--------------------------------------.
379 | Path | Private |
380 +-------------------------------------+--------------------------------------+
381 | / | /default |
382 | / | /index |
383 | /books | /books/index |
384 | /books/list | /books/list |
385 '-------------------------------------+--------------------------------------'
fce83e5f 386
fbbb9084 387 [debug] Loaded Chained actions:
388 .-------------------------------------+--------------------------------------.
389 | Path Spec | Private |
390 +-------------------------------------+--------------------------------------+
391 | /books/url_create/*/*/* | /books/url_create |
392 '-------------------------------------+--------------------------------------'
89d3dae9 393
55490817 394C<url_create> has disappeared form the "Loaded Path actions" section
395but it now shows up under the newly created "Loaded Chained actions"
72609296 396section. And the "/*/*/*" portion clearly shows our requirement for
fbbb9084 397three arguments.
89d3dae9 398
55490817 399As with our non-chained version of C<url_create>, use your browser to
89d3dae9 400enter the following URL:
fbbb9084 402 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
89d3dae9 403
55490817 404You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
405'Stevens' with a rating of 5." along with a dump of the new book model
72609296 406object. Click the "Return to list" link, and you should find that there
407are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>).
89d3dae9 408
8a472b34 410=head2 Refactor to Use a 'base' Method to Start the Chains
89d3dae9 411
55490817 412Let's make a quick update to our initial Chained action to show a
413little more of the power of chaining. First, open
89d3dae9 414C<lib/MyApp/Controller/> in your editor and add the following
fbbb9084 417 =head2 base
fce83e5f 418
fbbb9084 419 Can place common logic to start chained dispatch here
fce83e5f 420
fbbb9084 421 =cut
fce83e5f 422
fbbb9084 423 sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
424 my ($self, $c) = @_;
fce83e5f 425
1cde0fd6 426 # Store the ResultSet in stash so it's available for other methods
3b1fa91b 427 $c->stash->{resultset} = $c->model('DB::Book');
fce83e5f 428
fbbb9084 429 # Print a message to the debug log
430 $c->log->debug('*** INSIDE BASE METHOD ***');
431 }
55490817 433Here we print a log message and store the DBIC ResultSet in
434C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available
435for other actions that chain off C<base>. If your controller always
72609296 436needs a book ID as its first argument, you could have the base method
55490817 437capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
438book object with C<-E<gt>find($id)> and leave it in the stash for
439later parts of your chains to then act upon. Because we have several
994b66ad 440actions that don't need to retrieve a book (such as the C<url_create>
441we are working with now), we will instead add that functionality
442to a common C<object> action shortly.
55490817 444As for C<url_create>, let's modify it to first dispatch to C<base>.
445Open up C<lib/MyApp/Controller/> and edit the declaration for
994b66ad 446C<url_create> to match the following:
89d3dae9 447
448 sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
55490817 450Next, try out the refactored chain by restarting the development
451server. Notice that our "Loaded Chained actions" section has changed
fbbb9084 452slightly:
55490817 453
fbbb9084 454 [debug] Loaded Chained actions:
455 .-------------------------------------+--------------------------------------.
456 | Path Spec | Private |
457 +-------------------------------------+--------------------------------------+
458 | /books/url_create/*/*/* | /books/base (0) |
459 | | => /books/url_create |
460 '-------------------------------------+--------------------------------------'
89d3dae9 461
fce83e5f 462The "Path Spec" is the same, but now it maps to two Private actions as
463we would expect. The C<base> method is being triggered by the
464C</books> part of the URL. However, the processing then continues to
465the C<url_create> method because this method "chained" off C<base> and
466specified C<:PathPart('url_create')> (note that we could have omitted
467the "PathPart" here because it matches the name of the method, but we
468will include it to make the logic behind the tutorial as explicit as
89d3dae9 470
471Once again, enter the following URL into your browser:
fbbb9084 473 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
89d3dae9 474
fce83e5f 475The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
476rating of 5." message and a dump of the new book object should appear.
477Also notice the extra "INSIDE BASE METHOD" debug message in the
478development server output from the C<base> method. Click the "Return
479to list" link, and you should find that there are now eight books
480shown. (You may have a larger number of books if you repeated any of
481the "create" actions more than once. Don't worry about it as long as
482the number of books is appropriate for the number of times you added
483new books... there should be the original five books added via
484C<myapp01.sql> plus one additional book for each time you ran one
485of the url_create variations above.)
d442cc9f 486
490Although the C<url_create> action in the previous step does begin to
491reveal the power and flexibility of both Catalyst and DBIC, it's
492obviously not a very realistic example of how users should be expected
493to enter data. This section begins to address that concern.
496=head2 Add Method to Display The Form
498Edit C<lib/MyApp/Controller/> and add the following method:
500 =head2 form_create
fce83e5f 501
d442cc9f 502 Display form to collect information for book to create
fce83e5f 503
d442cc9f 504 =cut
fce83e5f 505
89d3dae9 506 sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
d442cc9f 507 my ($self, $c) = @_;
fce83e5f 508
d442cc9f 509 # Set the TT template to use
510 $c->stash->{template} = 'books/form_create.tt2';
511 }
72609296 513This action simply invokes a view containing a form to create a book.
d442cc9f 514
1390ef0e 515
d442cc9f 516=head2 Add a Template for the Form
518Open C<root/src/books/form_create.tt2> in your editor and enter:
520 [% META title = 'Manual Form Book Create' -%]
55490817 521
8a7c5151 522 <form method="post" action="[% c.uri_for('form_create_do') %]">
d442cc9f 523 <table>
524 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
525 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
526 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
527 </table>
528 <input type="submit" name="Submit" value="Submit">
529 </form>
531Note that we have specified the target of the form data as
532C<form_create_do>, the method created in the section that follows.
1390ef0e 534
d442cc9f 535=head2 Add a Method to Process Form Values and Update Database
537Edit C<lib/MyApp/Controller/> and add the following method to
538save the form information to the database:
540 =head2 form_create_do
fce83e5f 541
d442cc9f 542 Take information from form and add to database
fce83e5f 543
d442cc9f 544 =cut
fce83e5f 545
89d3dae9 546 sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
d442cc9f 547 my ($self, $c) = @_;
fce83e5f 548
d442cc9f 549 # Retrieve the values from the form
550 my $title = $c->request->params->{title} || 'N/A';
551 my $rating = $c->request->params->{rating} || 'N/A';
552 my $author_id = $c->request->params->{author_id} || '1';
fce83e5f 553
d442cc9f 554 # Create the book
3b1fa91b 555 my $book = $c->model('DB::Book')->create({
d442cc9f 556 title => $title,
557 rating => $rating,
558 });
559 # Handle relationship with author
fce83e5f 560 $book->add_to_book_authors({author_id => $author_id});
561 # Note: Above is a shortcut for this:
562 # $book->create_related('book_authors', {author_id => $author_id});
d442cc9f 564 # Store new model object in stash
565 $c->stash->{book} = $book;
fce83e5f 566
d442cc9f 567 # Avoid Data::Dumper issue mentioned earlier
55490817 568 # You can probably omit this
d442cc9f 569 $Data::Dumper::Useperl = 1;
fce83e5f 570
d442cc9f 571 # Set the TT template to use
572 $c->stash->{template} = 'books/create_done.tt2';
573 }
576=head2 Test Out The Form
578If the application is still running from before, use C<Ctrl-C> to kill
579it. Then restart the server:
581 $ script/
55490817 583Notice that the server startup log reflects the two new chained
89d3dae9 584methods that we added:
fbbb9084 586 [debug] Loaded Chained actions:
587 .-------------------------------------+--------------------------------------.
588 | Path Spec | Private |
589 +-------------------------------------+--------------------------------------+
590 | /books/form_create | /books/base (0) |
591 | | => /books/form_create |
592 | /books/form_create_do | /books/base (0) |
593 | | => /books/form_create_do |
594 | /books/url_create/*/*/* | /books/base (0) |
595 | | => /books/url_create |
596 '-------------------------------------+--------------------------------------'
89d3dae9 597
d442cc9f 598Point your browser to L<http://localhost:3000/books/form_create> and
599enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
1390ef0e 600author ID of 4. You should then see the output of the same
d442cc9f 601C<create_done.tt2> template seen in earlier examples. Finally, click
602"Return to list" to view the full list of books.
604B<Note:> Having the user enter the primary key ID for the author is
fce83e5f 605obviously crude; we will address this concern with a drop-down list and
606add validation to our forms in Chapter 9.
d442cc9f 607
72609296 611Turning our attention to the Delete portion of CRUD, this section
d442cc9f 612illustrates some basic techniques that can be used to remove information
613from the database.
616=head2 Include a Delete Link in the List
1cde0fd6 618Edit C<root/src/books/list.tt2> and update it to match the following (two
d442cc9f 619sections have changed: 1) the additional '<th>Links</th>' table header,
72609296 620and 2) the four lines for the Delete link near the bottom):
d442cc9f 621
622 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
623 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
624 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
625 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
fce83e5f 626
28c32bc6 627 [% # Provide a title -%]
d442cc9f 628 [% META title = 'Book List' -%]
fce83e5f 629
d442cc9f 630 <table>
631 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
632 [% # Display each book in a table row %]
633 [% FOREACH book IN books -%]
634 <tr>
635 <td>[% book.title %]</td>
636 <td>[% book.rating %]</td>
637 <td>
fce83e5f 638 [% # NOTE: See "Exploring The Power of DBIC" for a better way to do this! -%]
d442cc9f 639 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
640 [% # loop in 'side effect notation' to load just the last names of the -%]
55490817 641 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
d442cc9f 642 [% # a value, so nothing will be printed here. But, if you have something -%]
55490817 643 [% # in TT that does return a value and you don't want it printed, you can -%]
3b1fa91b 644 [% # 1) assign it to a bogus value, or # 2) use the CALL keyword to -%]
645 [% # call it and discard the return value. -%]
d442cc9f 646 [% tt_authors = [ ];
fce83e5f 647 tt_authors.push(author.last_name) FOREACH author = book.authors %]
d442cc9f 648 [% # Now use a TT 'virtual method' to display the author count in parens -%]
3b1fa91b 649 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
650 ([% tt_authors.size | html %])
d442cc9f 651 [% # Use another TT vmethod to join & print the names & comma separators -%]
3b1fa91b 652 [% tt_authors.join(', ') | html %]
d442cc9f 653 </td>
654 <td>
655 [% # Add a link to delete a book %]
e075db0c 656 <a href="[% c.uri_for(c.controller.action_for('delete'), []) %]">Delete</a>
d442cc9f 657 </td>
658 </tr>
659 [% END -%]
660 </table>
55490817 662The additional code is obviously designed to add a new column to the
72609296 663right side of the table with a C<Delete> "button" (for simplicity, links
664will be used instead of full HTML buttons; in practice, anything that
fce83e5f 665modifies data should be handled with a form sending a POST request).
fe01b24f 666
55490817 667Also notice that we are using a more advanced form of C<uri_for> than
668we have seen before. Here we use
669C<$c-E<gt>controller-E<gt>action_for> to automatically generate a URI
670appropriate for that action based on the method we want to link to
671while inserting the C<> value into the appropriate place. Now,
672if you ever change C<:PathPart('delete')> in your controller method to
673C<:PathPart('kill')>, then your links will automatically update
674without any changes to your .tt2 template file. As long as the name
72609296 675of your method does not change (here, "delete"), then your links will
55490817 676still be correct. There are a few shortcuts and options when using
0416017e 677C<action_for()>:
679=over 4
681=item *
683If you are referring to a method in the current controller, you can
684use C<$self-E<gt>action_for('_method_name_')>.
686=item *
688If you are referring to a method in a different controller, you need
fbbb9084 689to include that controller's name as an argument to C<controller()>, as in
0416017e 690C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>.
b2ad8bbd 693
55490817 694B<Note:> In practice you should B<never> use a GET request to delete a
695record -- always use POST for actions that will modify data. We are
c5d94181 696doing it here for illustrative and simplicity purposes only.
d442cc9f 697
1390ef0e 698
994b66ad 699=head2 Add a Common Method to Retrieve a Book for the Chain
55490817 701As mentioned earlier, since we have a mixture of actions that operate
702on a single book ID and others that do not, we should not have C<base>
703capture the book ID, find the corresponding book in the database and
704save it in the stash for later links in the chain. However, just
705because that logic does not belong in C<base> doesn't mean that we
706can't create another location to centralize the book lookup code. In
707our case, we will create a method called C<object> that will store the
708specific book in the stash. Chains that always operate on a single
709existing book can chain off this method, but methods such as
710C<url_create> that don't operate on an existing book can chain
fbbb9084 711directly off base.
994b66ad 712
713To add the C<object> method, edit C<lib/MyApp/Controller/>
714and add the following code:
e075db0c 716 =head2 object
fce83e5f 717
e075db0c 718 Fetch the specified book object based on the book ID and store
719 it in the stash
fce83e5f 720
e075db0c 721 =cut
fce83e5f 722
994b66ad 723 sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
fbbb9084 724 # $id = primary key of book to delete
994b66ad 725 my ($self, $c, $id) = @_;
fce83e5f 726
994b66ad 727 # Find the book object and store it in the stash
728 $c->stash(object => $c->stash->{resultset}->find($id));
fce83e5f 729
994b66ad 730 # Make sure the lookup was successful. You would probably
731 # want to do something like this in a real app:
732 # $c->detach('/error_404') if !$c->stash->{object};
733 die "Book $id not found!" if !$c->stash->{object};
fce83e5f 734
735 # Print a message to the debug log
736 $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***");
994b66ad 737 }
739Now, any other method that chains off C<object> will automatically
55490817 740have the appropriate book waiting for it in
acbd7bdd 741C<$c-E<gt>stash-E<gt>{object}>.
994b66ad 742
72609296 743Also note that we are using a different technique for setting
744C<$c-E<gt>stash>. The advantage of this style is that it lets you set
745multiple stash variables at a time. For example:
994b66ad 746
747 $c->stash(object => $c->stash->{resultset}->find($id),
748 another_thing => 1);
750or as a hashref:
752 $c->stash({object => $c->stash->{resultset}->find($id),
753 another_thing => 1});
fbbb9084 755Either format works, but the C<$c-E<gt>stash(name =E<gt> value);>
72609296 756style is growing in popularity -- you may wish to use it all
994b66ad 757the time (even when you are only setting a single value).
d442cc9f 760=head2 Add a Delete Action to the Controller
762Open C<lib/MyApp/Controller/> in your editor and add the
763following method:
1390ef0e 765 =head2 delete
fce83e5f 766
d442cc9f 767 Delete a book
fce83e5f 768
d442cc9f 769 =cut
fce83e5f 770
994b66ad 771 sub delete :Chained('object') :PathPart('delete') :Args(0) {
994b66ad 772 my ($self, $c) = @_;
fce83e5f 773
994b66ad 774 # Use the book object saved by 'object' and delete it along
3b1fa91b 775 # with related 'book_author' entries
994b66ad 776 $c->stash->{object}->delete;
fce83e5f 777
d442cc9f 778 # Set a status message to be displayed at the top of the view
779 $c->stash->{status_msg} = "Book deleted.";
fce83e5f 780
d442cc9f 781 # Forward to the list action/method in this controller
782 $c->forward('list');
783 }
55490817 785This method first deletes the book object saved by the C<object> method.
786However, it also removes the corresponding entry from the
3b1fa91b 787C<book_author> table with a cascading delete.
d442cc9f 788
789Then, rather than forwarding to a "delete done" page as we did with the
790earlier create example, it simply sets the C<status_msg> to display a
791notification to the user as the normal list view is rendered.
793The C<delete> action uses the context C<forward> method to return the
794user to the book list. The C<detach> method could have also been used.
795Whereas C<forward> I<returns> to the original action once it is
796completed, C<detach> does I<not> return. Other than that, the two are
800=head2 Try the Delete Feature
802If the application is still running from before, use C<Ctrl-C> to kill
803it. Then restart the server:
994b66ad 805 $ DBIC_TRACE=1 script/
d442cc9f 806
89d3dae9 807The C<delete> method now appears in the "Loaded Chained actions" section
808of the startup debug output:
fbbb9084 810 [debug] Loaded Chained actions:
994b66ad 811 .-------------------------------------+--------------------------------------.
812 | Path Spec | Private |
813 +-------------------------------------+--------------------------------------+
814 | /books/id/*/delete | /books/base (0) |
815 | | -> /books/object (1) |
816 | | => /books/delete |
817 | /books/form_create | /books/base (0) |
818 | | => /books/form_create |
819 | /books/form_create_do | /books/base (0) |
820 | | => /books/form_create_do |
821 | /books/url_create/*/*/* | /books/base (0) |
822 | | => /books/url_create |
823 '-------------------------------------+--------------------------------------'
89d3dae9 824
d442cc9f 825Then point your browser to L<http://localhost:3000/books/list> and click
55490817 826the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green
827"Book deleted" status message should display at the top of the page,
994b66ad 828along with a list of the eight remaining books. You will also see the
829cascading delete operation via the DBIC_TRACE output:
3b1fa91b 831 SELECT, me.title, me.rating FROM book me WHERE ( ( = ? ) ): '6'
832 DELETE FROM book WHERE ( id = ? ): '6'
833 SELECT me.book_id, me.author_id FROM book_author me WHERE ( me.book_id = ? ): '6'
834 DELETE FROM book_author WHERE ( author_id = ? AND book_id = ? ): '4', '6'
d442cc9f 835
837=head2 Fixing a Dangerous URL
55490817 839Note the URL in your browser once you have performed the deletion in the
d442cc9f 840prior step -- it is still referencing the delete action:
acbd7bdd 842 http://localhost:3000/books/id/6/delete
d442cc9f 843
55490817 844What if the user were to press reload with this URL still active? In
845this case the redundant delete is harmless (although it does generate
846an exception screen, it doesn't perform any undesirable actions on the
847application or database), but in other cases this could clearly be
fbbb9084 848extremely dangerous.
d442cc9f 849
850We can improve the logic by converting to a redirect. Unlike
851C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform
852a server-side alteration in the flow of processing, a redirect is a
3533daff 853client-side mechanism that causes the browser to issue an entirely
d442cc9f 854new request. As a result, the URL in the browser is updated to match
855the destination of the redirection URL.
857To convert the forward used in the previous section to a redirect,
55490817 858open C<lib/MyApp/Controller/> and edit the existing
d442cc9f 859C<sub delete> method to match:
994b66ad 861 =head2 delete
fce83e5f 862
d442cc9f 863 Delete a book
fce83e5f 864
d442cc9f 865 =cut
fce83e5f 866
994b66ad 867 sub delete :Chained('object') :PathPart('delete') :Args(0) {
fbbb9084 868 my ($self, $c) = @_;
fce83e5f 869
994b66ad 870 # Use the book object saved by 'object' and delete it along
3b1fa91b 871 # with related 'book_author' entries
994b66ad 872 $c->stash->{object}->delete;
fce83e5f 873
d442cc9f 874 # Set a status message to be displayed at the top of the view
875 $c->stash->{status_msg} = "Book deleted.";
fce83e5f 876
0416017e 877 # Redirect the user back to the list page. Note the use
878 # of $self->action_for as earlier in this section (BasicCRUD)
fbbb9084 879 $c->response->redirect($c->uri_for($self->action_for('list')));
d442cc9f 880 }
883=head2 Try the Delete and Redirect Logic
55490817 885Restart the development server and point your browser to
886L<http://localhost:3000/books/list> (don't just hit "Refresh" in your
887browser since we left the URL in an invalid state in the previous
888section!) and delete the first copy of the remaining two
889"TCPIP_Illustrated_Vol-2" books. The URL in your browser should return
890to the L<http://localhost:3000/books/list> URL, so that is an
891improvement, but notice that I<no green "Book deleted" status message is
892displayed>. Because the stash is reset on every request (and a redirect
893involves a second request), the C<status_msg> is cleared before it can
994b66ad 894be displayed.
d442cc9f 895
8a472b34 897=head2 Using 'uri_for' to Pass Query Parameters
d442cc9f 898
4b4d3884 899There are several ways to pass information across a redirect. One
900option is to use the C<flash> technique that we will see in Chapter 5
72609296 901of this tutorial; however, here we will pass the information via query
4b4d3884 902parameters on the redirect itself. Open
903C<lib/MyApp/Controller/> and update the existing C<sub delete>
89d3dae9 904method to match the following:
d442cc9f 905
55490817 906 =head2 delete
fce83e5f 907
d442cc9f 908 Delete a book
fce83e5f 909
d442cc9f 910 =cut
fce83e5f 911
994b66ad 912 sub delete :Chained('object') :PathPart('delete') :Args(0) {
fbbb9084 913 my ($self, $c) = @_;
fce83e5f 914
994b66ad 915 # Use the book object saved by 'object' and delete it along
3b1fa91b 916 # with related 'book_author' entries
994b66ad 917 $c->stash->{object}->delete;
fce83e5f 918
d442cc9f 919 # Redirect the user back to the list page with status msg as an arg
55490817 920 $c->response->redirect($c->uri_for($self->action_for('list'),
d442cc9f 921 {status_msg => "Book deleted."}));
922 }
924This modification simply leverages the ability of C<uri_for> to include
55490817 925an arbitrary number of name/value pairs in a hash reference. Next, we
926need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a
d442cc9f 927query parameter:
1390ef0e 929 ...
d442cc9f 930 <div id="content">
1390ef0e 931 [%# Status and error messages %]
932 <span class="message">[% status_msg || c.request.params.status_msg %]</span>
933 <span class="error">[% error_msg %]</span>
934 [%# This is where TT will stick all of your template's contents. -%]
935 [% content %]
936 </div><!-- end content -->
937 ...
55490817 939Although the sample above only shows the C<content> div, leave the
1390ef0e 940rest of the file intact -- the only change we made to the C<wrapper.tt2>
55490817 941was to add "C<|| c.request.params.status_msg>" to the
1390ef0e 942C<E<lt>span class="message"E<gt>> line.
d442cc9f 943
945=head2 Try the Delete and Redirect With Query Param Logic
55490817 947Restart the development server and point your browser to
948L<http://localhost:3000/books/list> (you should now be able to safely
949hit "refresh" in your browser). Then delete the remaining copy of
950"TCPIP_Illustrated_Vol-2". The green "Book deleted" status message
d442cc9f 951should return.
55490817 953B<NOTE:> Another popular method for maintaining server-side
954information across a redirect is to use the C<flash> technique we
4b4d3884 955discuss in the next chapter of the tutorial,
3ab6187c 956L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>. While
55490817 957C<flash> is a "slicker" mechanism in that it's all handled by the
958server and doesn't "pollute" your URLs, B<it is important to note that
959C<flash> can lead to situations where the wrong information shows up
960in the wrong browser window if the user has multiple windows or
72609296 961browser tabs open>. For example, Window A causes something to be
55490817 962placed in the stash, but before that window performs a redirect,
963Window B makes a request to the server and gets the status information
994b66ad 964that should really go to Window A. For this reason, you may wish
89d3dae9 965to use the "query param" technique shown here in your applications.
d442cc9f 966
1cde0fd6 968=head1 EXPLORING THE POWER OF DBIC
55490817 970In this section we will explore some additional capabilities offered
971by DBIx::Class. Although these features have relatively little to do
972with Catalyst per se, you will almost certainly want to take advantage
1cde0fd6 973of them in your applications.
1cde0fd6 976=head2 Add Datetime Columns to Our Existing Books Table
55490817 978Let's add two columns to our existing C<books> table to track when
1cde0fd6 979each book was added and when each book is updated:
981 $ sqlite3 myapp.db
3b1fa91b 982 sqlite> ALTER TABLE book ADD created INTEGER;
983 sqlite> ALTER TABLE book ADD updated INTEGER;
984 sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
985 sqlite> SELECT * FROM book;
acbd7bdd 986 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35
987 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35
988 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35
989 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35
990 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35
991 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1cde0fd6 992 sqlite> .quit
993 $
995This will modify the C<books> table to include the two new fields
996and populate those fields with the current time.
acbd7bdd 998
a46b474e 999=head2 Update DBIx::Class to Automatically Handle the Datetime Columns
1cde0fd6 1000
1001Next, we should re-run the DBIC helper to update the Result Classes
1002with the new fields:
1004 $ script/ model DB DBIC::Schema MyApp::Schema \
1005 create=static components=TimeStamp dbi:SQLite:myapp.db
1006 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
1007 exists "/root/dev/MyApp/script/../t"
1008 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
1009 Schema dump completed.
1010 exists "/root/dev/MyApp/script/../lib/MyApp/Model/"
1012Notice that we modified our use of the helper slightly: we told
d05dbc42 1013it to include the L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp>
1cde0fd6 1014in the C<load_components> line of the Result Classes.
3b1fa91b 1016If you open C<lib/MyApp/Schema/Result/> in your editor you
55490817 1017should see that the C<created> and C<updated> fields are now included
72609296 1018in the call to C<add_columns()>, but our relationship information below
55490817 1019the "C<# DO NOT MODIFY...>" line was automatically preserved.
1cde0fd6 1020
55490817 1021While we have this file open, let's update it with some additional
1022information to have DBIC automatically handle the updating of these
1023two fields for us. Insert the following code at the bottom of the
1024file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and
1cde0fd6 1025B<above> the C<1;> on the last line):
1027 #
1028 # Enable automatic date handling
1029 #
1030 __PACKAGE__->add_columns(
1031 "created",
1032 { data_type => 'datetime', set_on_create => 1 },
1033 "updated",
1034 { data_type => 'datetime', set_on_create => 1, set_on_update => 1 },
55490817 1035 );
1cde0fd6 1036
a46b474e 1037This will override the definition for these fields that Schema::Loader
1038placed at the top of the file. The C<set_on_create> and
1039C<set_on_update> options will cause DBIx::Class to automatically
1040update the timestamps in these columns whenever a row is created or
1cde0fd6 1042
1043To test this out, restart the development server using the
1044C<DBIC_TRACE=1> option:
1046 DBIC_TRACE=1 script/
1048Then enter the following URL into your web browser:
1050 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
1052You should get the same "Book Created" screen we saw above. However,
1053if you now use the sqlite3 command-line tool to dump the C<books> table,
1054you will see that the new book we added has an appropriate date and
1055time entered for it (see the last line in the listing below):
3b1fa91b 1057 sqlite3 myapp.db "select * from book"
acbd7bdd 1058 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1059 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1060 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35
1061 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1062 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1063 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1064 10|TCPIP_Illustrated_Vol-2|5|2009-03-08 16:29:08|2009-03-08 16:29:08
1cde0fd6 1065
55490817 1066Notice in the debug log that the SQL DBIC generated has changed to
1cde0fd6 1067incorporate the datetime logic:
fce83e5f 1069 INSERT INTO book ( created, rating, title, updated) VALUES ( ?, ?, ?, ? ):
1070 '2009-05-25 20:39:41', '5', 'TCPIP_Illustrated_Vol-2', '2009-05-25 20:39:41'
1071 INSERT INTO book_author ( author_id, book_id) VALUES ( ?, ? ): '4', '10'
1cde0fd6 1072
1074=head2 Create a ResultSet Class
55490817 1076An often overlooked but extremely powerful features of DBIC is that it
1077allows you to supply your own subclasses of C<DBIx::Class::ResultSet>.
1078It allows you to pull complex and unsightly "query code" out of your
1cde0fd6 1079controllers and encapsulate it in a method of your ResultSet Class.
1080These "canned queries" in your ResultSet Class can then be invoked
1081via a single call, resulting in much cleaner and easier to read
1082controller code.
55490817 1084To illustrate the concept with a fairly simple example, let's create a
1cde0fd6 1085method that returns books added in the last 10 minutes. Start by
a46b474e 1086making a directory where DBIx::Class will look for our ResultSet Class:
1cde0fd6 1087
1088 mkdir lib/MyApp/Schema/ResultSet
3b1fa91b 1090Then open C<lib/MyApp/Schema/ResultSet/> and enter the following:
1cde0fd6 1091
3b1fa91b 1092 package MyApp::Schema::ResultSet::Book;
fce83e5f 1093
1cde0fd6 1094 use strict;
1095 use warnings;
1096 use base 'DBIx::Class::ResultSet';
fce83e5f 1097
1cde0fd6 1098 =head2 created_after
fce83e5f 1099
1cde0fd6 1100 A predefined search for recently added books
fce83e5f 1101
1cde0fd6 1102 =cut
fce83e5f 1103
1cde0fd6 1104 sub created_after {
fadc4ae7 1105 my ($self, $datetime) = @_;
fce83e5f 1106
fadc4ae7 1107 my $date_str = $self->_source_handle->schema->storage
1108 ->datetime_parser->format_datetime($datetime);
fce83e5f 1109
fadc4ae7 1110 return $self->search({
1111 created => { '>' => $date_str }
1112 });
1cde0fd6 1113 }
fce83e5f 1114
1cde0fd6 1115 1;
55490817 1117Then we need to tell the Result Class to to treat this as a ResultSet
3b1fa91b 1118Class. Open C<lib/MyApp/Schema/Result/> and add the following
1cde0fd6 1119above the "C<1;>" at the bottom of the file:
1121 #
1122 # Set ResultSet Class
1123 #
3b1fa91b 1124 __PACKAGE__->resultset_class('MyApp::Schema::ResultSet::Book');
1cde0fd6 1125
1126Then add the following method to the C<lib/MyApp/Controller/>:
1128 =head2 list_recent
fce83e5f 1129
1cde0fd6 1130 List recently created books
fce83e5f 1131
1cde0fd6 1132 =cut
fce83e5f 1133
1cde0fd6 1134 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
1135 my ($self, $c, $mins) = @_;
fce83e5f 1136
1cde0fd6 1137 # Retrieve all of the book records as book model objects and store in the
1138 # stash where they can be accessed by the TT template, but only
1139 # retrieve books created within the last $min number of minutes
3b1fa91b 1140 $c->stash->{books} = [$c->model('DB::Book')
1cde0fd6 1141 ->created_after(DateTime->now->subtract(minutes => $mins))];
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).
1146 $c->stash->{template} = 'books/list.tt2';
1147 }
55490817 1149Now start the development server with C<DBIC_TRACE=1> and try
1150different values for the minutes argument (the final number value) for
1151the URL C<http://localhost:3000/books/list_recent/10>. For example,
1cde0fd6 1152this would list all books added in the last fifteen minutes:
1154 http://localhost:3000/books/list_recent/15
1156Depending on how recently you added books, you might want to
1157try a higher or lower value.
1160=head2 Chaining ResultSets
a46b474e 1162One of the most helpful and powerful features in DBIx::Class is that
1163it allows you to "chain together" a series of queries (note that this
1164has nothing to do with the "Chained Dispatch" for Catalyst that we
1165were discussing above). Because each ResultSet returns another
1166ResultSet, you can take an initial query and immediately feed that
1167into a second query (and so on for as many queries you need). Note
1168that no matter how many ResultSets you chain together, the database
1169itself will not be hit until you use a method that attempts to access
1170the data. And, because this technique carries over to the ResultSet
1171Class feature we implemented in the previous section for our "canned
1172search", we can combine the two capabilities. For example, let's add
1173an action to our C<Books> controller that lists books that are both
1174recent I<and> have "TCP" in the title. Open up
1175C<lib/MyApp/Controller/> and add the following method:
1cde0fd6 1176
acbd7bdd 1177 =head2 list_recent_tcp
fce83e5f 1178
1cde0fd6 1179 List recently created books
fce83e5f 1180
1cde0fd6 1181 =cut
fce83e5f 1182
1cde0fd6 1183 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1184 my ($self, $c, $mins) = @_;
fce83e5f 1185
1cde0fd6 1186 # Retrieve all of the book records as book model objects and store in the
1187 # stash where they can be accessed by the TT template, but only
1188 # retrieve books created within the last $min number of minutes
1189 # AND that have 'TCP' in the title
3b1fa91b 1190 $c->stash->{books} = [$c->model('DB::Book')
1cde0fd6 1191 ->created_after(DateTime->now->subtract(minutes => $mins))
1192 ->search({title => {'like', '%TCP%'}})
1193 ];
fce83e5f 1194
1cde0fd6 1195 # Set the TT template to use. You will almost always want to do this
1196 # in your action methods (action methods respond to user input in
1197 # your controllers).
1198 $c->stash->{template} = 'books/list.tt2';
1199 }
1201To try this out, restart the development server with:
1203 DBIC_TRACE=1 script/
1205And enter the following URL into your browser:
1207 http://localhost:3000/books/list_recent_tcp/100
55490817 1209And you should get a list of books added in the last 100 minutes that
1210contain the string "TCP" in the title. However, if you look at all
1211books within the last 100 minutes, you should get a longer list
1212(again, you might have to adjust the number of minutes depending on
1cde0fd6 1213how recently you added books to your database):
1215 http://localhost:3000/books/list_recent/100
55490817 1217Take a look at the DBIC_TRACE output in the development server log for
1cde0fd6 1218the first URL and you should see something similar to the following:
fce83e5f 1220 SELECT, me.title, me.rating, me.created, me.updated FROM book me
1221 WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2009-05-25 19:09:13'
1cde0fd6 1222
55490817 1223However, let's not pollute our controller code with this raw "TCP"
1224query -- it would be cleaner to encapsulate that code in a method on
1225our ResultSet Class. To do this, open
3b1fa91b 1226C<lib/MyApp/Schema/ResultSet/> and add the following method:
1cde0fd6 1227
1228 =head2 title_like
fce83e5f 1229
1cde0fd6 1230 A predefined search for books with a 'LIKE' search in the string
fce83e5f 1231
1cde0fd6 1232 =cut
fce83e5f 1233
1cde0fd6 1234 sub title_like {
fadc4ae7 1235 my ($self, $title_str) = @_;
fce83e5f 1236
fadc4ae7 1237 return $self->search({
1238 title => { 'like' => "%$title_str%" }
1239 });
1cde0fd6 1240 }
55490817 1242We defined the search string as C<$title_str> to make the method more
1243flexible. Now update the C<list_recent_tcp> method in
1244C<lib/MyApp/Controller/> to match the following (we have
1245replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line
1cde0fd6 1246shown here -- the rest of the method should be the same):
1248 =head2 list_recent_tcp
fce83e5f 1249
1cde0fd6 1250 List recently created books
fce83e5f 1251
1cde0fd6 1252 =cut
fce83e5f 1253
1cde0fd6 1254 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1255 my ($self, $c, $mins) = @_;
fce83e5f 1256
1cde0fd6 1257 # Retrieve all of the book records as book model objects and store in the
1258 # stash where they can be accessed by the TT template, but only
1259 # retrieve books created within the last $min number of minutes
1260 # AND that have 'TCP' in the title
3b1fa91b 1261 $c->stash->{books} = [$c->model('DB::Book')
1cde0fd6 1262 ->created_after(DateTime->now->subtract(minutes => $mins))
1263 ->title_like('TCP')
1264 ];
fce83e5f 1265
1cde0fd6 1266 # Set the TT template to use. You will almost always want to do this
1267 # in your action methods (action methods respond to user input in
1268 # your controllers).
1269 $c->stash->{template} = 'books/list.tt2';
1270 }
55490817 1272Then restart the development server and try out the C<list_recent_tcp>
1273and C<list_recent> URL as we did above. It should work just the same,
1274but our code is obviously cleaner and more modular, while also being
1cde0fd6 1275more flexible at the same time.
1278=head2 Adding Methods to Result Classes
a46b474e 1280In the previous two sections we saw a good example of how we could use
1281DBIx::Class ResultSet Classes to clean up our code for an entire query
1282(for example, our "canned searches" that filtered the entire query).
1283We can do a similar improvement when working with individual rows as
1284well. Whereas the ResultSet construct is used in DBIC to correspond
1285to an entire query, the Result Class construct is used to represent a
1286row. Therefore, we can add row-specific "helper methods" to our Result
1287Classes stored in C<lib/MyApp/Schema/Result/>. For example, open
3b1fa91b 1288C<lib/MyApp/Schema/Result/> and add the following method (as
a46b474e 1289always, it must be above the closing "C<1;>"):
1cde0fd6 1290
1291 #
1292 # Helper methods
1293 #
1294 sub full_name {
1295 my ($self) = @_;
fce83e5f 1296
1cde0fd6 1297 return $self->first_name . ' ' . $self->last_name;
1298 }
55490817 1300This will allow us to conveniently retrieve both the first and last
1301name for an author in one shot. Now open C<root/src/books/list.tt2>
1cde0fd6 1302and change the definition of C<tt_authors> from this:
acbd7bdd 1304 ...
1cde0fd6 1305 [% tt_authors = [ ];
fce83e5f 1306 tt_authors.push(author.last_name) FOREACH author = book.authors %]
acbd7bdd 1307 ...
1cde0fd6 1308
acbd7bdd 1311 ...
1cde0fd6 1312 [% tt_authors = [ ];
fce83e5f 1313 tt_authors.push(author.full_name) FOREACH author = book.authors %]
acbd7bdd 1314 ...
1cde0fd6 1315
55490817 1316(Only C<author.last_name> was changed to C<author.full_name> -- the
1cde0fd6 1317rest of the file should remain the same.)
1319Now restart the development server and go to the standard book list
1322 http://localhost:3000/books/list
55490817 1324The "Author(s)" column will now contain both the first and last name.
1325And, because the concatenation logic was encapsulated inside our
1326Result Class, it keeps the code inside our .tt template nice and clean
1327(remember, we want the templates to be as close to pure HTML markup as
1328possible). Obviously, this capability becomes even more useful as you
1329use to to remove even more complicated row-specific logic from your
1cde0fd6 1330templates!
fce83e5f 1333=head2 Moving Complicated View Code to the Model
1335The previous section illustrated how we could use a Result Class
1336method to print the full names of the authors without adding any extra
1337code to our view, but it still left us with a fairly ugly mess (see
1340 ...
1341 <td>
1342 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1343 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1344 [% # loop in 'side effect notation' to load just the last names of the -%]
1345 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1346 [% # a value, so nothing will be printed here. But, if you have something -%]
1347 [% # in TT that does return a method and you don't want it printed, you -%]
1348 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1349 [% # call it and discard the return value. -%]
1350 [% tt_authors = [ ];
1351 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1352 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1353 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1354 ([% tt_authors.size | html %])
1355 [% # Use another TT vmethod to join & print the names & comma separators -%]
1356 [% tt_authors.join(', ') | html %]
1357 </td>
1358 ...
1360Let's combine some of the techniques used earlier in this section to
1361clean this up. First, let's add a method to our Book Result Class to
1362return the number of authors for a book. Open
1363C<lib/MyApp/Schema/Result/> and add the following method:
1365=head2 author_count
1367Return the number of authors for the current book
1369 =cut
1371 sub author_count {
1372 my ($self) = @_;
1374 # Use the 'many_to_many' relationship to fetch all of the authors for the current
1375 # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT
1376 return $self->authors->count;
1377 }
1379Next, let's add a method to return a list of authors for a book to the
1380same C<lib/MyApp/Schema/Result/> file:
1382 =head2 author_list
1384 Return a comma-separated list of authors for the current book
1386 =cut
1388 sub author_list {
1389 my ($self) = @_;
1391 # Loop through all authors for the current book, calling all the 'full_name'
1392 # Result Class method for each
1393 my @names;
1394 foreach my $author ($self->authors) {
1395 push(@names, $author->full_name);
1396 }
1398 return join(', ', @names);
1399 }
1401This method loops through each author, using the C<full_name> Result
1402Class method we added to C<lib/MyApp/Schema/Result/> in the
1403prior section.
1405Using these two methods, we can simplify our TT code. Open
1406C<root/src/books/list.tt2> and update the "Author(s)" table cell to
1407match the following:
1409 ...
1410 <td>
1411 [% # Print count and author list using Result Class methods -%]
1412 ([% book.author_count | html %]) [% book.author_list | html %]
1413 </td>
1414 ...
1416Although most of the code we removed comprised comments, the overall
1417effect is dramatic... because our view code is so simple, we don't
1418huge comments to clue people in to the gist of our code. The view
1419code is now self-documenting and readable enough that you could
1420probably get by with no comments at all. All of the "complex" work is
1421being done in our Result Class methods (and, because we have broken
1422the code into nice, modular chucks, the Result Class code is hardly
1423something you would call complex).
1425As we saw in this section, always strive to keep your view AND
1426controller code as simple as possible by pulling code out into your
1427model objects. Because DBIx::Class can be easily extended in so many
1428ways, it's an excellent to way accomplish this objective. It will
1429make your code cleaner, easier to write, less error-prone, and easier
1430to debug and maintain.
d442cc9f 1433=head1 AUTHOR
1435Kennedy Clark, C<>
1437Please report any errors, issues or suggestions to the author. The
1438most recent version of the Catalyst Tutorial can be found at
82ab4bbf 1439L<>.
d442cc9f 1440
45c7830f 1441Copyright 2006-2008, Kennedy Clark, under Creative Commons License
95674086 1442(L<>).