3 Catalyst::Manual::Tutorial::BasicCRUD - Catalyst Tutorial - Chapter 4: Basic CRUD
8 This is B<Chapter 4 of 10> for the Catalyst tutorial.
10 L<Tutorial Overview|Catalyst::Manual::Tutorial>
16 L<Introduction|Catalyst::Manual::Tutorial::Intro>
20 L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics>
24 L<More Catalyst Basics|Catalyst::Manual::Tutorial::MoreCatalystBasics>
32 L<Authentication|Catalyst::Manual::Tutorial::Authentication>
36 L<Authorization|Catalyst::Manual::Tutorial::Authorization>
40 L<Debugging|Catalyst::Manual::Tutorial::Debugging>
44 L<Testing|Catalyst::Manual::Tutorial::Testing>
48 L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
52 L<Appendices|Catalyst::Manual::Tutorial::Appendices>
59 This chapter of the tutorial builds on the fairly primitive
60 application created in Chapter 3 to add basic support for Create,
61 Read, Update, and Delete (CRUD) of C<Book> objects. Note that the
62 'list' function in Chapter 2 already implements the Read portion of
63 CRUD (although Read normally refers to reading a single object; you
64 could implement full read functionality using the techniques
65 introduced below). This section will focus on the Create and Delete
66 aspects of CRUD. More advanced capabilities, including full Update
67 functionality, will be addressed in Chapter 9.
69 Although this chapter of the tutorial will show you how to build CRUD
70 functionality yourself, another option is to use a "CRUD builder" type
71 of tool to automate the process. You get less control, but it's quick
72 and easy. For example, see
73 L<CatalystX::ListFramework::Builder|CatalystX::ListFramework::Builder>,
74 L<CatalystX::CRUD|CatalystX::CRUD>, and
75 L<CatalystX::CRUD::YUI|CatalystX::CRUD::YUI>.
77 You can checkout the source code for this example from the catalyst
78 subversion repository as per the instructions in
79 L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>.
82 =head1 FORMLESS SUBMISSION
84 Our initial attempt at object creation will utilize the "URL
85 arguments" feature of Catalyst (we will employ the more common form-
86 based submission in the sections that follow).
89 =head2 Include a Create Action in the Books Controller
91 Edit C<lib/MyApp/Controller/Books.pm> and enter the following method:
95 Create a book with the supplied title, rating, and author
99 sub url_create : Local {
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/"
104 my ($self, $c, $title, $rating, $author_id) = @_;
106 # Call create() on the book model object. Pass the table
107 # columns/field values we want to set as hash values
108 my $book = $c->model('DB::Books')->create({
113 # Add a record to the join table for this book, mapping to
115 $book->add_to_book_authors({author_id => $author_id});
116 # Note: Above is a shortcut for this:
117 # $book->create_related('book_authors', {author_id => $author_id});
119 # Assign the Book object to the stash for display in the view
120 $c->stash->{book} = $book;
122 # This is a hack to disable XSUB processing in Data::Dumper
123 # (it's used in the view). This is a work-around for a bug in
124 # the interaction of some versions or Perl, Data::Dumper & DBIC.
125 # You won't need this if you aren't using Data::Dumper (or if
126 # you are running DBIC 0.06001 or greater), but adding it doesn't
127 # hurt anything either.
128 $Data::Dumper::Useperl = 1;
130 # Set the TT template to use
131 $c->stash->{template} = 'books/create_done.tt2';
134 Notice that Catalyst takes "extra slash-separated information" from the
135 URL and passes it as arguments in C<@_>. The C<url_create> action then
136 uses a simple call to the DBIC C<create> method to add the requested
137 information to the database (with a separate call to
138 C<add_to_book_authors> to update the join table). As do virtually all
139 controller methods (at least the ones that directly handle user input),
140 it then sets the template that should handle this request.
143 =head2 Include a Template for the C<url_create> Action:
145 Edit C<root/src/books/create_done.tt2> and then enter:
147 [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%]
148 [% # Not a good idea for production use, though. :-) 'Indent=1' is -%]
149 [% # optional, but prevents "massive indenting" of deeply nested objects -%]
150 [% USE Dumper(Indent=1) -%]
152 [% # Set the page title. META can 'go back' and set values in templates -%]
153 [% # that have been processed 'before' this template (here it's for -%]
154 [% # root/lib/site/html and root/lib/site/header). Note that META on -%]
155 [% # simple strings (e.g., no variable interpolation). -%]
156 [% META title = 'Book Created' %]
158 [% # Output information about the record that was added. First title. -%]
159 <p>Added book '[% book.title %]'
161 [% # Output the last name of the first author. This is complicated by an -%]
162 [% # issue in TT 2.15 where blessed hash objects are not handled right. -%]
163 [% # First, fetch 'book.authors' from the DB once. -%]
164 [% authors = book.authors %]
165 [% # Now use IF statements to test if 'authors.first' is "working". If so, -%]
166 [% # we use it. Otherwise we use a hack that seems to keep TT 2.15 happy. -%]
167 by '[% authors.first.last_name IF authors.first;
168 authors.list.first.value.last_name IF ! authors.first %]'
170 [% # Output the rating for the book that was added -%]
171 with a rating of [% book.rating %].</p>
173 [% # Provide a link back to the list page -%]
174 [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%]
175 <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
177 [% # Try out the TT Dumper (for development only!) -%]
179 Dump of the 'book' variable:
180 [% Dumper.dump(book) %]
183 The TT C<USE> directive allows access to a variety of plugin modules
184 (TT plugins, that is, not Catalyst plugins) to add extra functionality
185 to the base TT capabilities. Here, the plugin allows
186 L<Data::Dumper|Data::Dumper> "pretty printing" of objects and
187 variables. Other than that, the rest of the code should be familiar
188 from the examples in Chapter 3.
191 =head2 Try the C<url_create> Feature
193 If the application is still running from before, use C<Ctrl-C> to kill
194 it. Then restart the server:
196 $ DBIC_TRACE=1 script/myapp_server.pl
198 Note that new path for C</books/url_create> appears in the startup debug
201 B<TIP>: You can use C<script/myapp_server.pl -r> to have the development
202 server auto-detect changed files and reload itself (if your browser acts
203 odd, you should also try throwing in a C<-k>). If you make changes to
204 the TT templates only, you do not need to reload the development server
205 (only changes to "compiled code" such as Controller and Model C<.pm>
206 files require a reload).
208 Next, use your browser to enter the following URL:
210 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
212 Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by
213 'Stevens' with a rating of 5." along with a dump of the new book model
214 object as it was returned by DBIC. You should also see the following
215 DBIC debug messages displayed in the development server log messages
216 if you have DBIC_TRACE set:
218 INSERT INTO books (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
219 INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): `4', `6'
220 SELECT author.id, author.first_name, author.last_name
221 FROM book_authors me JOIN authors author
222 ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '6'
224 The C<INSERT> statements are obviously adding the book and linking it to
225 the existing record for Richard Stevens. The C<SELECT> statement results
226 from DBIC automatically fetching the book for the C<Dumper.dump(book)>.
228 If you then click the "Return to list" link, you should find that
229 there are now six books shown (if necessary, Shift+Reload or
230 Ctrl+Reload your browser at the C</books/list> page).
233 =head1 CONVERT TO A CHAINED ACTION
235 Although the example above uses the same C<Local> action type for the
236 method that we saw in the previous chapter of the tutorial, there is an
237 alternate approach that allows us to be more specific while also
238 paving the way for more advanced capabilities. Change the method
239 declaration for C<url_create> in C<lib/MyApp/Controller/Books.pm> you
240 entered above to match the following:
242 sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
244 This converts the method to take advantage of the Chained
245 action/dispatch type. Chaining let's you have a single URL
246 automatically dispatch to several controller methods, each of which
247 can have precise control over the number of arguments that it will
248 receive. A chain can essentially be thought of having three parts --
249 a beginning, a middle and an end. The bullets below summarize the key
250 points behind each of these parts of a chain:
264 B<Use "C<:Chained('/')>" to start a chain>
268 Get arguments through C<CaptureArgs()>
272 Specify the path to match with C<PathPart()>
285 Link to previous part of the chain with C<:Chained('_name_')>
289 Get arguments through C<CaptureArgs()>
293 Specify the path to match with C<PathPart()>
306 Link to previous part of the chain with C<:Chained('_name_')>
310 B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain>
314 Specify the path to match with C<PathPart()>
321 In our C<url_create> method above, we have combined all 3 parts into a
322 single method: C<:Chained('/')> to start the chain,
323 C<:PathPart('books/url_create')> to specify the base URL to match,
324 along with C<:Args(3)> to capture exactly 3 arguments and also end the
327 As we will see shortly, a chain can consist of as many "links" as you
328 wish, with each part capturing some arguments and doing some work
329 along the way. We will continue to use the Chained action type in this
330 chapter of the tutorial and explore slightly more advanced capabilities
331 with the base method and delete feature below. But Chained dispatch
332 is capable of far more. For additional information, see
333 L<Catalyst::Manual::Intro/Action types>,
334 L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>,
335 and the 2006 advent calendar entry on the subject:
336 L<http://www.catalystframework.org/calendar/2006/10>.
339 =head2 Try the Chained Action
341 If you look back at the development server startup logs from your
342 initial version of the C<url_create> method (the one using the
343 C<:Local> attribute), you will notice that it produced output similar
346 [debug] Loaded Path actions:
347 .-------------------------------------+--------------------------------------.
349 +-------------------------------------+--------------------------------------+
352 | /books | /books/index |
353 | /books/list | /books/list |
354 | /books/url_create | /books/url_create |
355 '-------------------------------------+--------------------------------------'
357 Now start the development server with our basic chained method in
358 place and the startup debug output should change to something along
359 the lines of the following:
361 [debug] Loaded Path actions:
362 .-------------------------------------+--------------------------------------.
364 +-------------------------------------+--------------------------------------+
367 | /books | /books/index |
368 | /books/list | /books/list |
369 '-------------------------------------+--------------------------------------'
371 [debug] Loaded Chained actions:
372 .-------------------------------------+--------------------------------------.
373 | Path Spec | Private |
374 +-------------------------------------+--------------------------------------+
375 | /books/url_create/*/*/* | /books/url_create |
376 '-------------------------------------+--------------------------------------'
378 C<url_create> has disappeared form the "Loaded Path actions" section
379 but it now shows up under the newly created "Loaded Chained actions"
380 section. And, the "/*/*/*" portion clearly shows our requirement for
383 As with our non-chained version of C<url_create>, use your browser to
384 enter the following URL:
386 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
388 You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
389 'Stevens' with a rating of 5." along with a dump of the new book model
390 object. Click the "Return to list" link, you should find that there
391 are now seven books shown (two copies of TCPIP_Illustrated_Vol-2).
394 =head2 Refactor to Use a "Base" Method to Start the Chains
396 Let's make a quick update to our initial Chained action to show a
397 little more of the power of chaining. First, open
398 C<lib/MyApp/Controller/Books.pm> in your editor and add the following
403 Can place common logic to start chained dispatch here
407 sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
410 # Store the ResultSet in stash so it's available for other methods
411 $c->stash->{resultset} = $c->model('DB::Books');
413 # Print a message to the debug log
414 $c->log->debug('*** INSIDE BASE METHOD ***');
417 Here we print a log message and store the DBIC ResultSet in
418 C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available
419 for other actions that chain off C<base>. If your controller always
420 needs a book ID as it's first argument, you could have the base method
421 capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
422 book object with C<-E<gt>find($id)> and leave it in the stash for
423 later parts of your chains to then act upon. Because we have several
424 actions that don't need to retrieve a book (such as the C<url_create>
425 we are working with now), we will instead add that functionality
426 to a common C<object> action shortly.
428 As for C<url_create>, let's modify it to first dispatch to C<base>.
429 Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for
430 C<url_create> to match the following:
432 sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
434 Next, try out the refactored chain by restarting the development
435 server. Notice that our "Loaded Chained actions" section has changed
438 [debug] Loaded Chained actions:
439 .-------------------------------------+--------------------------------------.
440 | Path Spec | Private |
441 +-------------------------------------+--------------------------------------+
442 | /books/url_create/*/*/* | /books/base (0) |
443 | | => /books/url_create |
444 '-------------------------------------+--------------------------------------'
446 The "Path Spec" is the same, but now it maps to two Private actions as
449 Once again, enter the following URL into your browser:
451 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
453 The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
454 rating of 5" message and dump of the new book object should appear.
455 Also notice the extra debug message in the development server output
456 from the C<base> method. Click the "Return to list" link, you should
457 find that there are now eight books shown.
460 =head1 MANUALLY BUILDING A CREATE FORM
462 Although the C<url_create> action in the previous step does begin to
463 reveal the power and flexibility of both Catalyst and DBIC, it's
464 obviously not a very realistic example of how users should be expected
465 to enter data. This section begins to address that concern.
468 =head2 Add Method to Display The Form
470 Edit C<lib/MyApp/Controller/Books.pm> and add the following method:
474 Display form to collect information for book to create
478 sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
481 # Set the TT template to use
482 $c->stash->{template} = 'books/form_create.tt2';
485 This action simply invokes a view containing a book creation form.
488 =head2 Add a Template for the Form
490 Open C<root/src/books/form_create.tt2> in your editor and enter:
492 [% META title = 'Manual Form Book Create' -%]
494 <form method="post" action="[% c.uri_for('form_create_do') %]">
496 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
497 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
498 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
500 <input type="submit" name="Submit" value="Submit">
503 Note that we have specified the target of the form data as
504 C<form_create_do>, the method created in the section that follows.
507 =head2 Add a Method to Process Form Values and Update Database
509 Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
510 save the form information to the database:
512 =head2 form_create_do
514 Take information from form and add to database
518 sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
521 # Retrieve the values from the form
522 my $title = $c->request->params->{title} || 'N/A';
523 my $rating = $c->request->params->{rating} || 'N/A';
524 my $author_id = $c->request->params->{author_id} || '1';
527 my $book = $c->model('DB::Books')->create({
531 # Handle relationship with author
532 $book->add_to_book_authors({author_id => $author_id});
534 # Store new model object in stash
535 $c->stash->{book} = $book;
537 # Avoid Data::Dumper issue mentioned earlier
538 # You can probably omit this
539 $Data::Dumper::Useperl = 1;
541 # Set the TT template to use
542 $c->stash->{template} = 'books/create_done.tt2';
546 =head2 Test Out The Form
548 If the application is still running from before, use C<Ctrl-C> to kill
549 it. Then restart the server:
551 $ script/myapp_server.pl
553 Notice that the server startup log reflects the two new chained
554 methods that we added:
556 [debug] Loaded Chained actions:
557 .-------------------------------------+--------------------------------------.
558 | Path Spec | Private |
559 +-------------------------------------+--------------------------------------+
560 | /books/form_create | /books/base (0) |
561 | | => /books/form_create |
562 | /books/form_create_do | /books/base (0) |
563 | | => /books/form_create_do |
564 | /books/url_create/*/*/* | /books/base (0) |
565 | | => /books/url_create |
566 '-------------------------------------+--------------------------------------'
568 Point your browser to L<http://localhost:3000/books/form_create> and
569 enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
570 author ID of 4. You should then see the output of the same
571 C<create_done.tt2> template seen in earlier examples. Finally, click
572 "Return to list" to view the full list of books.
574 B<Note:> Having the user enter the primary key ID for the author is
575 obviously crude; we will address this concern with a drop-down list in
579 =head1 A SIMPLE DELETE FEATURE
581 Turning our attention to the delete portion of CRUD, this section
582 illustrates some basic techniques that can be used to remove information
586 =head2 Include a Delete Link in the List
588 Edit C<root/src/books/list.tt2> and update it to match the following (two
589 sections have changed: 1) the additional '<th>Links</th>' table header,
590 and 2) the four lines for the Delete link near the bottom).
592 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
593 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
594 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
595 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
597 [% # Provide a title to root/lib/site/header -%]
598 [% META title = 'Book List' -%]
601 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
602 [% # Display each book in a table row %]
603 [% FOREACH book IN books -%]
605 <td>[% book.title %]</td>
606 <td>[% book.rating %]</td>
608 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
609 [% # loop in 'side effect notation' to load just the last names of the -%]
610 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
611 [% # a value, so nothing will be printed here. But, if you have something -%]
612 [% # in TT that does return a value and you don't want it printed, you can -%]
613 [% # 1) assign it to a bogus value, or -%]
614 [% # 2) use the CALL keyword to call it and discard the return value. -%]
616 tt_authors.push(author.last_name) FOREACH author = book.authors %]
617 [% # Now use a TT 'virtual method' to display the author count in parens -%]
618 ([% tt_authors.size %])
619 [% # Use another TT vmethod to join & print the names & comma separators -%]
620 [% tt_authors.join(', ') %]
623 [% # Add a link to delete a book %]
624 <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a>
630 The additional code is obviously designed to add a new column to the
631 right side of the table with a C<Delete> "button" (for simplicity,
632 links will be used instead of full HTML buttons).
634 Also notice that we are using a more advanced form of C<uri_for> than
635 we have seen before. Here we use
636 C<$c-E<gt>controller-E<gt>action_for> to automatically generate a URI
637 appropriate for that action based on the method we want to link to
638 while inserting the C<book.id> value into the appropriate place. Now,
639 if you ever change C<:PathPart('delete')> in your controller method to
640 C<:PathPart('kill')>, then your links will automatically update
641 without any changes to your .tt2 template file. As long as the name
642 of your method does not change ("delete" here), then your links will
643 still be correct. There are a few shortcuts and options when using
650 If you are referring to a method in the current controller, you can
651 use C<$self-E<gt>action_for('_method_name_')>.
655 If you are referring to a method in a different controller, you need
656 to include that controller's name as an argument to C<controller()>, as in
657 C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>.
661 B<Note:> In practice you should B<never> use a GET request to delete a
662 record -- always use POST for actions that will modify data. We are
663 doing it here for illustrative and simplicity purposes only.
666 =head2 Add a Common Method to Retrieve a Book for the Chain
668 As mentioned earlier, since we have a mixture of actions that operate
669 on a single book ID and others that do not, we should not have C<base>
670 capture the book ID, find the corresponding book in the database and
671 save it in the stash for later links in the chain. However, just
672 because that logic does not belong in C<base> doesn't mean that we
673 can't create another location to centralize the book lookup code. In
674 our case, we will create a method called C<object> that will store the
675 specific book in the stash. Chains that always operate on a single
676 existing book can chain off this method, but methods such as
677 C<url_create> that don't operate on an existing book can chain
680 To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm>
681 and add the following code:
685 Fetch the specified book object based on the book ID and store
690 sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
691 # $id = primary key of book to delete
692 my ($self, $c, $id) = @_;
694 # Find the book object and store it in the stash
695 $c->stash(object => $c->stash->{resultset}->find($id));
697 # Make sure the lookup was successful. You would probably
698 # want to do something like this in a real app:
699 # $c->detach('/error_404') if !$c->stash->{object};
700 die "Book $id not found!" if !$c->stash->{object};
703 Now, any other method that chains off C<object> will automatically
704 have the appropriate book waiting for it in
705 C<$c-E<gt>stash-E<gt>{object}>.
707 Also note that we are using different technique for setting
708 C<$c-E<gt>stash>. The advantage of this style is that it let's you
709 set multiple stash variables at a time. For example:
711 $c->stash(object => $c->stash->{resultset}->find($id),
716 $c->stash({object => $c->stash->{resultset}->find($id),
717 another_thing => 1});
719 Either format works, but the C<$c-E<gt>stash(name =E<gt> value);>
720 style is growing in popularity -- you may which to use it all
721 the time (even when you are only setting a single value).
724 =head2 Add a Delete Action to the Controller
726 Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
735 sub delete :Chained('object') :PathPart('delete') :Args(0) {
738 # Use the book object saved by 'object' and delete it along
739 # with related 'book_authors' entries
740 $c->stash->{object}->delete;
742 # Set a status message to be displayed at the top of the view
743 $c->stash->{status_msg} = "Book deleted.";
745 # Forward to the list action/method in this controller
749 This method first deletes the book object saved by the C<object> method.
750 However, it also removes the corresponding entry from the
751 C<book_authors> table with a cascading delete.
753 Then, rather than forwarding to a "delete done" page as we did with the
754 earlier create example, it simply sets the C<status_msg> to display a
755 notification to the user as the normal list view is rendered.
757 The C<delete> action uses the context C<forward> method to return the
758 user to the book list. The C<detach> method could have also been used.
759 Whereas C<forward> I<returns> to the original action once it is
760 completed, C<detach> does I<not> return. Other than that, the two are
764 =head2 Try the Delete Feature
766 If the application is still running from before, use C<Ctrl-C> to kill
767 it. Then restart the server:
769 $ DBIC_TRACE=1 script/myapp_server.pl
771 The C<delete> method now appears in the "Loaded Chained actions" section
772 of the startup debug output:
774 [debug] Loaded Chained actions:
775 .-------------------------------------+--------------------------------------.
776 | Path Spec | Private |
777 +-------------------------------------+--------------------------------------+
778 | /books/id/*/delete | /books/base (0) |
779 | | -> /books/object (1) |
780 | | => /books/delete |
781 | /books/form_create | /books/base (0) |
782 | | => /books/form_create |
783 | /books/form_create_do | /books/base (0) |
784 | | => /books/form_create_do |
785 | /books/url_create/*/*/* | /books/base (0) |
786 | | => /books/url_create |
787 '-------------------------------------+--------------------------------------'
789 Then point your browser to L<http://localhost:3000/books/list> and click
790 the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green
791 "Book deleted" status message should display at the top of the page,
792 along with a list of the eight remaining books. You will also see the
793 cascading delete operation via the DBIC_TRACE output:
795 SELECT me.id, me.title, me.rating FROM books me WHERE ( ( me.id = ? ) ): '6'
796 DELETE FROM books WHERE ( id = ? ): '6'
797 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '6'
798 DELETE FROM book_authors WHERE ( author_id = ? AND book_id = ? ): '4', '6'
801 =head2 Fixing a Dangerous URL
803 Note the URL in your browser once you have performed the deletion in the
804 prior step -- it is still referencing the delete action:
806 http://localhost:3000/books/id/6/delete
808 What if the user were to press reload with this URL still active? In
809 this case the redundant delete is harmless (although it does generate
810 an exception screen, it doesn't perform any undesirable actions on the
811 application or database), but in other cases this could clearly be
814 We can improve the logic by converting to a redirect. Unlike
815 C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform
816 a server-side alteration in the flow of processing, a redirect is a
817 client-side mechanism that causes the browser to issue an entirely
818 new request. As a result, the URL in the browser is updated to match
819 the destination of the redirection URL.
821 To convert the forward used in the previous section to a redirect,
822 open C<lib/MyApp/Controller/Books.pm> and edit the existing
823 C<sub delete> method to match:
831 sub delete :Chained('object') :PathPart('delete') :Args(0) {
834 # Use the book object saved by 'object' and delete it along
835 # with related 'book_authors' entries
836 $c->stash->{object}->delete;
838 # Set a status message to be displayed at the top of the view
839 $c->stash->{status_msg} = "Book deleted.";
841 # Redirect the user back to the list page. Note the use
842 # of $self->action_for as earlier in this section (BasicCRUD)
843 $c->response->redirect($c->uri_for($self->action_for('list')));
847 =head2 Try the Delete and Redirect Logic
849 Restart the development server and point your browser to
850 L<http://localhost:3000/books/list> (don't just hit "Refresh" in your
851 browser since we left the URL in an invalid state in the previous
852 section!) and delete the first copy of the remaining two
853 "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return
854 to the L<http://localhost:3000/books/list> URL, so that is an
855 improvement, but notice that I<no green "Book deleted" status message is
856 displayed>. Because the stash is reset on every request (and a redirect
857 involves a second request), the C<status_msg> is cleared before it can
861 =head2 Using C<uri_for> to Pass Query Parameters
863 There are several ways to pass information across a redirect. One
864 option is to use the C<flash> technique that we will see in Chapter 5
865 of the tutorial; however, here we will pass the information via query
866 parameters on the redirect itself. Open
867 C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete>
868 method to match the following:
876 sub delete :Chained('object') :PathPart('delete') :Args(0) {
879 # Use the book object saved by 'object' and delete it along
880 # with related 'book_authors' entries
881 $c->stash->{object}->delete;
883 # Redirect the user back to the list page with status msg as an arg
884 $c->response->redirect($c->uri_for($self->action_for('list'),
885 {status_msg => "Book deleted."}));
888 This modification simply leverages the ability of C<uri_for> to include
889 an arbitrary number of name/value pairs in a hash reference. Next, we
890 need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a
895 [%# Status and error messages %]
896 <span class="message">[% status_msg || c.request.params.status_msg %]</span>
897 <span class="error">[% error_msg %]</span>
898 [%# This is where TT will stick all of your template's contents. -%]
900 </div><!-- end content -->
903 Although the sample above only shows the C<content> div, leave the
904 rest of the file intact -- the only change we made to the C<wrapper.tt2>
905 was to add "C<|| c.request.params.status_msg>" to the
906 C<E<lt>span class="message"E<gt>> line.
909 =head2 Try the Delete and Redirect With Query Param Logic
911 Restart the development server and point your browser to
912 L<http://localhost:3000/books/list> (you should now be able to safely
913 hit "refresh" in your browser). Then delete the remaining copy of
914 "TCPIP_Illustrated_Vol-2". The green "Book deleted" status message
917 B<NOTE:> Another popular method for maintaining server-side
918 information across a redirect is to use the C<flash> technique we
919 discuss in the next chapter of the tutorial,
920 L<Authentication|Catalyst::Manual::Tutorial::Authentication>. While
921 C<flash> is a "slicker" mechanism in that it's all handled by the
922 server and doesn't "pollute" your URLs, B<it is important to note that
923 C<flash> can lead to situations where the wrong information shows up
924 in the wrong browser window if the user has multiple windows or
925 browser tabs open.> For example, Window A causes something to be
926 placed in the stash, but before that window performs a redirect,
927 Window B makes a request to the server and gets the status information
928 that should really go to Window A. For this reason, you may wish
929 to use the "query param" technique shown here in your applications.
932 =head1 EXPLORING THE POWER OF DBIC
934 In this section we will explore some additional capabilities offered
935 by DBIx::Class. Although these features have relatively little to do
936 with Catalyst per se, you will almost certainly want to take advantage
937 of them in your applications.
940 =head2 Add Datetime Columns to Our Existing Books Table
942 Let's add two columns to our existing C<books> table to track when
943 each book was added and when each book is updated:
946 sqlite> ALTER TABLE books ADD created INTEGER;
947 sqlite> ALTER TABLE books ADD updated INTEGER;
948 sqlite> UPDATE books SET created = DATETIME('NOW'), updated = DATETIME('NOW');
949 sqlite> SELECT * FROM books;
950 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35
951 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35
952 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35
953 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35
954 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35
955 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35
959 This will modify the C<books> table to include the two new fields
960 and populate those fields with the current time.
963 =head2 Update DBIC to Automatically Handle the Datetime Columns
965 Next, we should re-run the DBIC helper to update the Result Classes
968 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
969 create=static components=TimeStamp dbi:SQLite:myapp.db
970 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
971 exists "/root/dev/MyApp/script/../t"
972 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
973 Schema dump completed.
974 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
976 Notice that we modified our use of the helper slightly: we told
977 it to include the L<DBIx::Class::Timestamp|DBIx::Class::Timestamp>
978 in the C<load_components> line of the Result Classes.
980 If you open C<lib/MyApp/Schema/Result/Books.pm> in your editor you
981 should see that the C<created> and C<updated> fields are now included
982 in the call to add_columns(), but our relationship information below
983 the "C<# DO NOT MODIFY...>" line was automatically preserved.
985 While we have this file open, let's update it with some additional
986 information to have DBIC automatically handle the updating of these
987 two fields for us. Insert the following code at the bottom of the
988 file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and
989 B<above> the C<1;> on the last line):
992 # Enable automatic date handling
994 __PACKAGE__->add_columns(
996 { data_type => 'datetime', set_on_create => 1 },
998 { data_type => 'datetime', set_on_create => 1, set_on_update => 1 },
1001 This will override the definition for these fields that Schema::Loader
1002 placed at the top of the file. The C<set_on_create> and
1003 C<set_on_update> options will cause DBIC to automatically update the
1004 timestamps in these columns whenever a row is created or modified.
1006 To test this out, restart the development server using the
1007 C<DBIC_TRACE=1> option:
1009 DBIC_TRACE=1 script/myapp_server.pl
1011 Then enter the following URL into your web browser:
1013 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
1015 You should get the same "Book Created" screen we saw above. However,
1016 if you now use the sqlite3 command-line tool to dump the C<books> table,
1017 you will see that the new book we added has an appropriate date and
1018 time entered for it (see the last line in the listing below):
1020 sqlite3 myapp.db "select * from books"
1021 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1022 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1023 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35
1024 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1025 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1026 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1027 10|TCPIP_Illustrated_Vol-2|5|2009-03-08 16:29:08|2009-03-08 16:29:08
1029 Notice in the debug log that the SQL DBIC generated has changed to
1030 incorporate the datetime logic:
1032 INSERT INTO books (created, rating, title, updated) VALUES (?, ?, ?, ?):
1033 '2009-03-08 16:29:08', '5', 'TCPIP_Illustrated_Vol-2', '2009-03-08 16:29:08'
1034 INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): '4', '10'
1037 =head2 Create a ResultSet Class
1039 An often overlooked but extremely powerful features of DBIC is that it
1040 allows you to supply your own subclasses of C<DBIx::Class::ResultSet>.
1041 It allows you to pull complex and unsightly "query code" out of your
1042 controllers and encapsulate it in a method of your ResultSet Class.
1043 These "canned queries" in your ResultSet Class can then be invoked
1044 via a single call, resulting in much cleaner and easier to read
1047 To illustrate the concept with a fairly simple example, let's create a
1048 method that returns books added in the last 10 minutes. Start by
1049 making a directory where DBIC will look for our ResultSet Class:
1051 mkdir lib/MyApp/Schema/ResultSet
1053 Then open C<lib/MyApp/Schema/ResultSet/Books.pm> and enter the following:
1055 package MyApp::Schema::ResultSet::Books;
1059 use base 'DBIx::Class::ResultSet';
1061 =head2 created_after
1063 A predefined search for recently added books
1068 my ($self, $datetime) = @_;
1070 my $date_str = $self->_source_handle->schema->storage
1071 ->datetime_parser->format_datetime($datetime);
1073 return $self->search({
1074 created => { '>' => $date_str }
1080 Then we need to tell the Result Class to to treat this as a ResultSet
1081 Class. Open C<lib/MyApp/Schema/Result/Books.pm> and add the following
1082 above the "C<1;>" at the bottom of the file:
1085 # Set ResultSet Class
1087 __PACKAGE__->resultset_class('MyApp::Schema::ResultSet::Books');
1089 Then add the following method to the C<lib/MyApp/Controller/Books.pm>:
1093 List recently created books
1097 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
1098 my ($self, $c, $mins) = @_;
1100 # Retrieve all of the book records as book model objects and store in the
1101 # stash where they can be accessed by the TT template, but only
1102 # retrieve books created within the last $min number of minutes
1103 $c->stash->{books} = [$c->model('DB::Books')
1104 ->created_after(DateTime->now->subtract(minutes => $mins))];
1106 # Set the TT template to use. You will almost always want to do this
1107 # in your action methods (action methods respond to user input in
1108 # your controllers).
1109 $c->stash->{template} = 'books/list.tt2';
1112 Now start the development server with C<DBIC_TRACE=1> and try
1113 different values for the minutes argument (the final number value) for
1114 the URL C<http://localhost:3000/books/list_recent/10>. For example,
1115 this would list all books added in the last fifteen minutes:
1117 http://localhost:3000/books/list_recent/15
1119 Depending on how recently you added books, you might want to
1120 try a higher or lower value.
1123 =head2 Chaining ResultSets
1125 One of the most helpful and powerful features in DBIC is that it
1126 allows you to "chain together" a series of queries (note that this has
1127 nothing to do with the "Chained Dispatch" for Catalyst that we were
1128 discussing above). Because each ResultSet returns another ResultSet,
1129 you can take an initial query and immediately feed that into a second
1130 query (and so on for as many queries you need). And, because this
1131 technique carries over to the ResultSet Class feature we implemented
1132 in the previous section for our "canned search", we can combine the
1133 two capabilities. For example, let's add an action to our C<Books>
1134 controller that lists books that are both recent I<and> have "TCP" in
1135 the title. Open up C<lib/MyApp/Controller/Books.pm> and add the
1138 =head2 list_recent_tcp
1140 List recently created books
1144 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1145 my ($self, $c, $mins) = @_;
1147 # Retrieve all of the book records as book model objects and store in the
1148 # stash where they can be accessed by the TT template, but only
1149 # retrieve books created within the last $min number of minutes
1150 # AND that have 'TCP' in the title
1151 $c->stash->{books} = [$c->model('DB::Books')
1152 ->created_after(DateTime->now->subtract(minutes => $mins))
1153 ->search({title => {'like', '%TCP%'}})
1156 # Set the TT template to use. You will almost always want to do this
1157 # in your action methods (action methods respond to user input in
1158 # your controllers).
1159 $c->stash->{template} = 'books/list.tt2';
1162 To try this out, restart the development server with:
1164 DBIC_TRACE=1 script/myapp_server.pl
1166 And enter the following URL into your browser:
1168 http://localhost:3000/books/list_recent_tcp/100
1170 And you should get a list of books added in the last 100 minutes that
1171 contain the string "TCP" in the title. However, if you look at all
1172 books within the last 100 minutes, you should get a longer list
1173 (again, you might have to adjust the number of minutes depending on
1174 how recently you added books to your database):
1176 http://localhost:3000/books/list_recent/100
1178 Take a look at the DBIC_TRACE output in the development server log for
1179 the first URL and you should see something similar to the following:
1181 SELECT me.id, me.title, me.rating, me.created, me.updated FROM books me
1182 WHERE ( ( ( title LIKE ? ) AND ( created > ? ) ) ): '%TCP%', '2009-03-08 14:52:54'
1184 However, let's not pollute our controller code with this raw "TCP"
1185 query -- it would be cleaner to encapsulate that code in a method on
1186 our ResultSet Class. To do this, open
1187 C<lib/MyApp/Schema/ResultSet/Books.pm> and add the following method:
1191 A predefined search for books with a 'LIKE' search in the string
1196 my ($self, $title_str) = @_;
1198 return $self->search({
1199 title => { 'like' => "%$title_str%" }
1203 We defined the search string as C<$title_str> to make the method more
1204 flexible. Now update the C<list_recent_tcp> method in
1205 C<lib/MyApp/Controller/Books.pm> to match the following (we have
1206 replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line
1207 shown here -- the rest of the method should be the same):
1209 =head2 list_recent_tcp
1211 List recently created books
1215 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1216 my ($self, $c, $mins) = @_;
1218 # Retrieve all of the book records as book model objects and store in the
1219 # stash where they can be accessed by the TT template, but only
1220 # retrieve books created within the last $min number of minutes
1221 # AND that have 'TCP' in the title
1222 $c->stash->{books} = [$c->model('DB::Books')
1223 ->created_after(DateTime->now->subtract(minutes => $mins))
1227 # Set the TT template to use. You will almost always want to do this
1228 # in your action methods (action methods respond to user input in
1229 # your controllers).
1230 $c->stash->{template} = 'books/list.tt2';
1233 Then restart the development server and try out the C<list_recent_tcp>
1234 and C<list_recent> URL as we did above. It should work just the same,
1235 but our code is obviously cleaner and more modular, while also being
1236 more flexible at the same time.
1239 =head2 Adding Methods to Result Classes
1241 In the previous two sections we saw a good example of how we could use
1242 DBIC ResultSet Classes to clean up our code for an entire query (for
1243 example, our "canned searches" that filtered the entire query). We
1244 can do a similar improvement when working with individual rows as
1245 well. Whereas the ResultSet construct is used in DBIC to correspond
1246 to an entire query, the Result Class construct is used to represent a
1247 row. Therefore, we can add row-specific "helper methods" to our Result
1248 Classes stored in C<lib/MyApp/Schema/Result/>. For example, open
1249 C<lib/MyApp/Schema/Result/Authors.pm> and add the following method
1250 (as always, it must be above the closing "C<1;>"):
1258 return $self->first_name . ' ' . $self->last_name;
1261 This will allow us to conveniently retrieve both the first and last
1262 name for an author in one shot. Now open C<root/src/books/list.tt2>
1263 and change the definition of C<tt_authors> from this:
1266 [% tt_authors = [ ];
1267 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1273 [% tt_authors = [ ];
1274 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1277 (Only C<author.last_name> was changed to C<author.full_name> -- the
1278 rest of the file should remain the same.)
1280 Now restart the development server and go to the standard book list
1283 http://localhost:3000/books/list
1285 The "Author(s)" column will now contain both the first and last name.
1286 And, because the concatenation logic was encapsulated inside our
1287 Result Class, it keeps the code inside our .tt template nice and clean
1288 (remember, we want the templates to be as close to pure HTML markup as
1289 possible). Obviously, this capability becomes even more useful as you
1290 use to to remove even more complicated row-specific logic from your
1296 Kennedy Clark, C<hkclark@gmail.com>
1298 Please report any errors, issues or suggestions to the author. The
1299 most recent version of the Catalyst Tutorial can be found at
1300 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
1302 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1303 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).