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 check out 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 '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 only -%]
155 [% # works on simple/static strings (i.e. there is no variable -%]
156 [% # interpolation). -%]
157 [% META title = 'Book Created' %]
159 [% # Output information about the record that was added. First title. -%]
160 <p>Added book '[% book.title %]'
162 [% # Output the last name of the first author. This is complicated by an -%]
163 [% # issue in TT 2.15 where blessed hash objects are not handled right. -%]
164 [% # First, fetch 'book.authors' from the DB once. -%]
165 [% authors = book.authors %]
166 [% # Now use IF statements to test if 'authors.first' is "working". If so, -%]
167 [% # we use it. Otherwise we use a hack that seems to keep TT 2.15 happy. -%]
168 by '[% authors.first.last_name IF authors.first;
169 authors.list.first.value.last_name IF ! authors.first %]'
171 [% # Output the rating for the book that was added -%]
172 with a rating of [% book.rating %].</p>
174 [% # Provide a link back to the list page -%]
175 [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%]
176 <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
178 [% # Try out the TT Dumper (for development only!) -%]
180 Dump of the 'book' variable:
181 [% Dumper.dump(book) %]
184 The TT C<USE> directive allows access to a variety of plugin modules
185 (TT plugins, that is, not Catalyst plugins) to add extra functionality
186 to the base TT capabilities. Here, the plugin allows
187 L<Data::Dumper|Data::Dumper> "pretty printing" of objects and
188 variables. Other than that, the rest of the code should be familiar
189 from the examples in Chapter 3.
192 =head2 Try the 'url_create' Feature
194 If the application is still running from before, use C<Ctrl-C> to kill
195 it. Then restart the server:
197 $ DBIC_TRACE=1 script/myapp_server.pl
199 Note that new path for C</books/url_create> appears in the startup debug
202 B<TIP>: You can use C<script/myapp_server.pl -r> to have the development
203 server auto-detect changed files and reload itself (if your browser acts
204 odd, you should also try throwing in a C<-k>). If you make changes to
205 the TT templates only, you do not need to reload the development server
206 (only changes to "compiled code" such as Controller and Model C<.pm>
207 files require a reload).
209 Next, use your browser to enter the following URL:
211 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
213 Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by
214 'Stevens' with a rating of 5." along with a dump of the new book model
215 object as it was returned by DBIC. You should also see the following
216 DBIC debug messages displayed in the development server log messages
217 if you have DBIC_TRACE set:
219 INSERT INTO books (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
220 INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): `4', `6'
221 SELECT author.id, author.first_name, author.last_name
222 FROM book_authors me JOIN authors author
223 ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '6'
225 The C<INSERT> statements are obviously adding the book and linking it to
226 the existing record for Richard Stevens. The C<SELECT> statement results
227 from DBIC automatically fetching the book for the C<Dumper.dump(book)>.
229 If you then click the "Return to list" link, you should find that
230 there are now six books shown (if necessary, Shift+Reload or
231 Ctrl+Reload your browser at the C</books/list> page).
234 =head1 CONVERT TO A CHAINED ACTION
236 Although the example above uses the same C<Local> action type for the
237 method that we saw in the previous chapter of the tutorial, there is an
238 alternate approach that allows us to be more specific while also
239 paving the way for more advanced capabilities. Change the method
240 declaration for C<url_create> in C<lib/MyApp/Controller/Books.pm> you
241 entered above to match the following:
243 sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
245 This converts the method to take advantage of the Chained
246 action/dispatch type. Chaining lets you have a single URL
247 automatically dispatch to several controller methods, each of which
248 can have precise control over the number of arguments that it will
249 receive. A chain can essentially be thought of having three parts --
250 a beginning, a middle, and an end. The bullets below summarize the key
251 points behind each of these parts of a chain:
265 B<Use "C<:Chained('/')>" to start a chain>
269 Get arguments through C<CaptureArgs()>
273 Specify the path to match with C<PathPart()>
286 Link to previous part of the chain with C<:Chained('_name_')>
290 Get arguments through C<CaptureArgs()>
294 Specify the path to match with C<PathPart()>
307 Link to previous part of the chain with C<:Chained('_name_')>
311 B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain>
315 Specify the path to match with C<PathPart()>
322 In our C<url_create> method above, we have combined all three parts into
323 a single method: C<:Chained('/')> to start the chain,
324 C<:PathPart('books/url_create')> to specify the base URL to match, and
325 C<:Args(3)> to capture exactly three arguments and to end the chain.
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, and you should find that there
391 are now seven books shown (two copies of I<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 its 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 a 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, and you
457 should 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 form to create a book.
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, links
632 will be used instead of full HTML buttons; in practice, anything that
633 modifies data should be handled with a form sending a PUT request).
635 Also notice that we are using a more advanced form of C<uri_for> than
636 we have seen before. Here we use
637 C<$c-E<gt>controller-E<gt>action_for> to automatically generate a URI
638 appropriate for that action based on the method we want to link to
639 while inserting the C<book.id> value into the appropriate place. Now,
640 if you ever change C<:PathPart('delete')> in your controller method to
641 C<:PathPart('kill')>, then your links will automatically update
642 without any changes to your .tt2 template file. As long as the name
643 of your method does not change (here, "delete"), then your links will
644 still be correct. There are a few shortcuts and options when using
651 If you are referring to a method in the current controller, you can
652 use C<$self-E<gt>action_for('_method_name_')>.
656 If you are referring to a method in a different controller, you need
657 to include that controller's name as an argument to C<controller()>, as in
658 C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>.
662 B<Note:> In practice you should B<never> use a GET request to delete a
663 record -- always use POST for actions that will modify data. We are
664 doing it here for illustrative and simplicity purposes only.
667 =head2 Add a Common Method to Retrieve a Book for the Chain
669 As mentioned earlier, since we have a mixture of actions that operate
670 on a single book ID and others that do not, we should not have C<base>
671 capture the book ID, find the corresponding book in the database and
672 save it in the stash for later links in the chain. However, just
673 because that logic does not belong in C<base> doesn't mean that we
674 can't create another location to centralize the book lookup code. In
675 our case, we will create a method called C<object> that will store the
676 specific book in the stash. Chains that always operate on a single
677 existing book can chain off this method, but methods such as
678 C<url_create> that don't operate on an existing book can chain
681 To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm>
682 and add the following code:
686 Fetch the specified book object based on the book ID and store
691 sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
692 # $id = primary key of book to delete
693 my ($self, $c, $id) = @_;
695 # Find the book object and store it in the stash
696 $c->stash(object => $c->stash->{resultset}->find($id));
698 # Make sure the lookup was successful. You would probably
699 # want to do something like this in a real app:
700 # $c->detach('/error_404') if !$c->stash->{object};
701 die "Book $id not found!" if !$c->stash->{object};
704 Now, any other method that chains off C<object> will automatically
705 have the appropriate book waiting for it in
706 C<$c-E<gt>stash-E<gt>{object}>.
708 Also note that we are using a different technique for setting
709 C<$c-E<gt>stash>. The advantage of this style is that it lets you set
710 multiple stash variables at a time. For example:
712 $c->stash(object => $c->stash->{resultset}->find($id),
717 $c->stash({object => $c->stash->{resultset}->find($id),
718 another_thing => 1});
720 Either format works, but the C<$c-E<gt>stash(name =E<gt> value);>
721 style is growing in popularity -- you may wish to use it all
722 the time (even when you are only setting a single value).
725 =head2 Add a Delete Action to the Controller
727 Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
736 sub delete :Chained('object') :PathPart('delete') :Args(0) {
739 # Use the book object saved by 'object' and delete it along
740 # with related 'book_authors' entries
741 $c->stash->{object}->delete;
743 # Set a status message to be displayed at the top of the view
744 $c->stash->{status_msg} = "Book deleted.";
746 # Forward to the list action/method in this controller
750 This method first deletes the book object saved by the C<object> method.
751 However, it also removes the corresponding entry from the
752 C<book_authors> table with a cascading delete.
754 Then, rather than forwarding to a "delete done" page as we did with the
755 earlier create example, it simply sets the C<status_msg> to display a
756 notification to the user as the normal list view is rendered.
758 The C<delete> action uses the context C<forward> method to return the
759 user to the book list. The C<detach> method could have also been used.
760 Whereas C<forward> I<returns> to the original action once it is
761 completed, C<detach> does I<not> return. Other than that, the two are
765 =head2 Try the Delete Feature
767 If the application is still running from before, use C<Ctrl-C> to kill
768 it. Then restart the server:
770 $ DBIC_TRACE=1 script/myapp_server.pl
772 The C<delete> method now appears in the "Loaded Chained actions" section
773 of the startup debug output:
775 [debug] Loaded Chained actions:
776 .-------------------------------------+--------------------------------------.
777 | Path Spec | Private |
778 +-------------------------------------+--------------------------------------+
779 | /books/id/*/delete | /books/base (0) |
780 | | -> /books/object (1) |
781 | | => /books/delete |
782 | /books/form_create | /books/base (0) |
783 | | => /books/form_create |
784 | /books/form_create_do | /books/base (0) |
785 | | => /books/form_create_do |
786 | /books/url_create/*/*/* | /books/base (0) |
787 | | => /books/url_create |
788 '-------------------------------------+--------------------------------------'
790 Then point your browser to L<http://localhost:3000/books/list> and click
791 the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green
792 "Book deleted" status message should display at the top of the page,
793 along with a list of the eight remaining books. You will also see the
794 cascading delete operation via the DBIC_TRACE output:
796 SELECT me.id, me.title, me.rating FROM books me WHERE ( ( me.id = ? ) ): '6'
797 DELETE FROM books WHERE ( id = ? ): '6'
798 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '6'
799 DELETE FROM book_authors WHERE ( author_id = ? AND book_id = ? ): '4', '6'
802 =head2 Fixing a Dangerous URL
804 Note the URL in your browser once you have performed the deletion in the
805 prior step -- it is still referencing the delete action:
807 http://localhost:3000/books/id/6/delete
809 What if the user were to press reload with this URL still active? In
810 this case the redundant delete is harmless (although it does generate
811 an exception screen, it doesn't perform any undesirable actions on the
812 application or database), but in other cases this could clearly be
815 We can improve the logic by converting to a redirect. Unlike
816 C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform
817 a server-side alteration in the flow of processing, a redirect is a
818 client-side mechanism that causes the browser to issue an entirely
819 new request. As a result, the URL in the browser is updated to match
820 the destination of the redirection URL.
822 To convert the forward used in the previous section to a redirect,
823 open C<lib/MyApp/Controller/Books.pm> and edit the existing
824 C<sub delete> method to match:
832 sub delete :Chained('object') :PathPart('delete') :Args(0) {
835 # Use the book object saved by 'object' and delete it along
836 # with related 'book_authors' entries
837 $c->stash->{object}->delete;
839 # Set a status message to be displayed at the top of the view
840 $c->stash->{status_msg} = "Book deleted.";
842 # Redirect the user back to the list page. Note the use
843 # of $self->action_for as earlier in this section (BasicCRUD)
844 $c->response->redirect($c->uri_for($self->action_for('list')));
848 =head2 Try the Delete and Redirect Logic
850 Restart the development server and point your browser to
851 L<http://localhost:3000/books/list> (don't just hit "Refresh" in your
852 browser since we left the URL in an invalid state in the previous
853 section!) and delete the first copy of the remaining two
854 "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return
855 to the L<http://localhost:3000/books/list> URL, so that is an
856 improvement, but notice that I<no green "Book deleted" status message is
857 displayed>. Because the stash is reset on every request (and a redirect
858 involves a second request), the C<status_msg> is cleared before it can
862 =head2 Using 'uri_for' to Pass Query Parameters
864 There are several ways to pass information across a redirect. One
865 option is to use the C<flash> technique that we will see in Chapter 5
866 of this tutorial; however, here we will pass the information via query
867 parameters on the redirect itself. Open
868 C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete>
869 method to match the following:
877 sub delete :Chained('object') :PathPart('delete') :Args(0) {
880 # Use the book object saved by 'object' and delete it along
881 # with related 'book_authors' entries
882 $c->stash->{object}->delete;
884 # Redirect the user back to the list page with status msg as an arg
885 $c->response->redirect($c->uri_for($self->action_for('list'),
886 {status_msg => "Book deleted."}));
889 This modification simply leverages the ability of C<uri_for> to include
890 an arbitrary number of name/value pairs in a hash reference. Next, we
891 need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a
896 [%# Status and error messages %]
897 <span class="message">[% status_msg || c.request.params.status_msg %]</span>
898 <span class="error">[% error_msg %]</span>
899 [%# This is where TT will stick all of your template's contents. -%]
901 </div><!-- end content -->
904 Although the sample above only shows the C<content> div, leave the
905 rest of the file intact -- the only change we made to the C<wrapper.tt2>
906 was to add "C<|| c.request.params.status_msg>" to the
907 C<E<lt>span class="message"E<gt>> line.
910 =head2 Try the Delete and Redirect With Query Param Logic
912 Restart the development server and point your browser to
913 L<http://localhost:3000/books/list> (you should now be able to safely
914 hit "refresh" in your browser). Then delete the remaining copy of
915 "TCPIP_Illustrated_Vol-2". The green "Book deleted" status message
918 B<NOTE:> Another popular method for maintaining server-side
919 information across a redirect is to use the C<flash> technique we
920 discuss in the next chapter of the tutorial,
921 L<Authentication|Catalyst::Manual::Tutorial::Authentication>. While
922 C<flash> is a "slicker" mechanism in that it's all handled by the
923 server and doesn't "pollute" your URLs, B<it is important to note that
924 C<flash> can lead to situations where the wrong information shows up
925 in the wrong browser window if the user has multiple windows or
926 browser tabs open>. For example, Window A causes something to be
927 placed in the stash, but before that window performs a redirect,
928 Window B makes a request to the server and gets the status information
929 that should really go to Window A. For this reason, you may wish
930 to use the "query param" technique shown here in your applications.
933 =head1 EXPLORING THE POWER OF DBIC
935 In this section we will explore some additional capabilities offered
936 by DBIx::Class. Although these features have relatively little to do
937 with Catalyst per se, you will almost certainly want to take advantage
938 of them in your applications.
941 =head2 Add Datetime Columns to Our Existing Books Table
943 Let's add two columns to our existing C<books> table to track when
944 each book was added and when each book is updated:
947 sqlite> ALTER TABLE books ADD created INTEGER;
948 sqlite> ALTER TABLE books ADD updated INTEGER;
949 sqlite> UPDATE books SET created = DATETIME('NOW'), updated = DATETIME('NOW');
950 sqlite> SELECT * FROM books;
951 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35
952 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35
953 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35
954 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35
955 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35
956 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35
960 This will modify the C<books> table to include the two new fields
961 and populate those fields with the current time.
964 =head2 Update DBIC to Automatically Handle the Datetime Columns
966 Next, we should re-run the DBIC helper to update the Result Classes
969 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
970 create=static components=TimeStamp dbi:SQLite:myapp.db
971 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
972 exists "/root/dev/MyApp/script/../t"
973 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
974 Schema dump completed.
975 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
977 Notice that we modified our use of the helper slightly: we told
978 it to include the L<DBIx::Class::Timestamp|DBIx::Class::Timestamp>
979 in the C<load_components> line of the Result Classes.
981 If you open C<lib/MyApp/Schema/Result/Books.pm> in your editor you
982 should see that the C<created> and C<updated> fields are now included
983 in the call to C<add_columns()>, but our relationship information below
984 the "C<# DO NOT MODIFY...>" line was automatically preserved.
986 While we have this file open, let's update it with some additional
987 information to have DBIC automatically handle the updating of these
988 two fields for us. Insert the following code at the bottom of the
989 file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and
990 B<above> the C<1;> on the last line):
993 # Enable automatic date handling
995 __PACKAGE__->add_columns(
997 { data_type => 'datetime', set_on_create => 1 },
999 { data_type => 'datetime', set_on_create => 1, set_on_update => 1 },
1002 This will override the definition for these fields that Schema::Loader
1003 placed at the top of the file. The C<set_on_create> and
1004 C<set_on_update> options will cause DBIC to automatically update the
1005 timestamps in these columns whenever a row is created or modified.
1007 To test this out, restart the development server using the
1008 C<DBIC_TRACE=1> option:
1010 DBIC_TRACE=1 script/myapp_server.pl
1012 Then enter the following URL into your web browser:
1014 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
1016 You should get the same "Book Created" screen we saw above. However,
1017 if you now use the sqlite3 command-line tool to dump the C<books> table,
1018 you will see that the new book we added has an appropriate date and
1019 time entered for it (see the last line in the listing below):
1021 sqlite3 myapp.db "select * from books"
1022 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1023 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1024 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35
1025 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1026 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1027 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1028 10|TCPIP_Illustrated_Vol-2|5|2009-03-08 16:29:08|2009-03-08 16:29:08
1030 Notice in the debug log that the SQL DBIC generated has changed to
1031 incorporate the datetime logic:
1033 INSERT INTO books (created, rating, title, updated) VALUES (?, ?, ?, ?):
1034 '2009-03-08 16:29:08', '5', 'TCPIP_Illustrated_Vol-2', '2009-03-08 16:29:08'
1035 INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): '4', '10'
1038 =head2 Create a ResultSet Class
1040 An often overlooked but extremely powerful features of DBIC is that it
1041 allows you to supply your own subclasses of C<DBIx::Class::ResultSet>.
1042 It allows you to pull complex and unsightly "query code" out of your
1043 controllers and encapsulate it in a method of your ResultSet Class.
1044 These "canned queries" in your ResultSet Class can then be invoked
1045 via a single call, resulting in much cleaner and easier to read
1048 To illustrate the concept with a fairly simple example, let's create a
1049 method that returns books added in the last 10 minutes. Start by
1050 making a directory where DBIC will look for our ResultSet Class:
1052 mkdir lib/MyApp/Schema/ResultSet
1054 Then open C<lib/MyApp/Schema/ResultSet/Books.pm> and enter the following:
1056 package MyApp::Schema::ResultSet::Books;
1060 use base 'DBIx::Class::ResultSet';
1062 =head2 created_after
1064 A predefined search for recently added books
1069 my ($self, $datetime) = @_;
1071 my $date_str = $self->_source_handle->schema->storage
1072 ->datetime_parser->format_datetime($datetime);
1074 return $self->search({
1075 created => { '>' => $date_str }
1081 Then we need to tell the Result Class to to treat this as a ResultSet
1082 Class. Open C<lib/MyApp/Schema/Result/Books.pm> and add the following
1083 above the "C<1;>" at the bottom of the file:
1086 # Set ResultSet Class
1088 __PACKAGE__->resultset_class('MyApp::Schema::ResultSet::Books');
1090 Then add the following method to the C<lib/MyApp/Controller/Books.pm>:
1094 List recently created books
1098 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
1099 my ($self, $c, $mins) = @_;
1101 # Retrieve all of the book records as book model objects and store in the
1102 # stash where they can be accessed by the TT template, but only
1103 # retrieve books created within the last $min number of minutes
1104 $c->stash->{books} = [$c->model('DB::Books')
1105 ->created_after(DateTime->now->subtract(minutes => $mins))];
1107 # Set the TT template to use. You will almost always want to do this
1108 # in your action methods (action methods respond to user input in
1109 # your controllers).
1110 $c->stash->{template} = 'books/list.tt2';
1113 Now start the development server with C<DBIC_TRACE=1> and try
1114 different values for the minutes argument (the final number value) for
1115 the URL C<http://localhost:3000/books/list_recent/10>. For example,
1116 this would list all books added in the last fifteen minutes:
1118 http://localhost:3000/books/list_recent/15
1120 Depending on how recently you added books, you might want to
1121 try a higher or lower value.
1124 =head2 Chaining ResultSets
1126 One of the most helpful and powerful features in DBIC is that it allows
1127 you to "chain together" a series of queries (note that this has nothing
1128 to do with the "Chained Dispatch" for Catalyst that we were discussing
1129 above). Because each ResultSet returns another ResultSet, you can take
1130 an initial query and immediately feed that into a second query (and so
1131 on for as many queries you need). Note that no matter how many
1132 ResultSets you chain together, the database itself will not be hit until
1133 you use a method that attempts to access the data. And, because this
1134 technique carries over to the ResultSet Class feature we implemented in
1135 the previous section for our "canned search", we can combine the two
1136 capabilities. For example, let's add an action to our C<Books>
1137 controller that lists books that are both recent I<and> have "TCP" in
1138 the title. Open up C<lib/MyApp/Controller/Books.pm> and add the
1141 =head2 list_recent_tcp
1143 List recently created books
1147 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1148 my ($self, $c, $mins) = @_;
1150 # Retrieve all of the book records as book model objects and store in the
1151 # stash where they can be accessed by the TT template, but only
1152 # retrieve books created within the last $min number of minutes
1153 # AND that have 'TCP' in the title
1154 $c->stash->{books} = [$c->model('DB::Books')
1155 ->created_after(DateTime->now->subtract(minutes => $mins))
1156 ->search({title => {'like', '%TCP%'}})
1159 # Set the TT template to use. You will almost always want to do this
1160 # in your action methods (action methods respond to user input in
1161 # your controllers).
1162 $c->stash->{template} = 'books/list.tt2';
1165 To try this out, restart the development server with:
1167 DBIC_TRACE=1 script/myapp_server.pl
1169 And enter the following URL into your browser:
1171 http://localhost:3000/books/list_recent_tcp/100
1173 And you should get a list of books added in the last 100 minutes that
1174 contain the string "TCP" in the title. However, if you look at all
1175 books within the last 100 minutes, you should get a longer list
1176 (again, you might have to adjust the number of minutes depending on
1177 how recently you added books to your database):
1179 http://localhost:3000/books/list_recent/100
1181 Take a look at the DBIC_TRACE output in the development server log for
1182 the first URL and you should see something similar to the following:
1184 SELECT me.id, me.title, me.rating, me.created, me.updated FROM books me
1185 WHERE ( ( ( title LIKE ? ) AND ( created > ? ) ) ): '%TCP%', '2009-03-08 14:52:54'
1187 However, let's not pollute our controller code with this raw "TCP"
1188 query -- it would be cleaner to encapsulate that code in a method on
1189 our ResultSet Class. To do this, open
1190 C<lib/MyApp/Schema/ResultSet/Books.pm> and add the following method:
1194 A predefined search for books with a 'LIKE' search in the string
1199 my ($self, $title_str) = @_;
1201 return $self->search({
1202 title => { 'like' => "%$title_str%" }
1206 We defined the search string as C<$title_str> to make the method more
1207 flexible. Now update the C<list_recent_tcp> method in
1208 C<lib/MyApp/Controller/Books.pm> to match the following (we have
1209 replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line
1210 shown here -- the rest of the method should be the same):
1212 =head2 list_recent_tcp
1214 List recently created books
1218 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1219 my ($self, $c, $mins) = @_;
1221 # Retrieve all of the book records as book model objects and store in the
1222 # stash where they can be accessed by the TT template, but only
1223 # retrieve books created within the last $min number of minutes
1224 # AND that have 'TCP' in the title
1225 $c->stash->{books} = [$c->model('DB::Books')
1226 ->created_after(DateTime->now->subtract(minutes => $mins))
1230 # Set the TT template to use. You will almost always want to do this
1231 # in your action methods (action methods respond to user input in
1232 # your controllers).
1233 $c->stash->{template} = 'books/list.tt2';
1236 Then restart the development server and try out the C<list_recent_tcp>
1237 and C<list_recent> URL as we did above. It should work just the same,
1238 but our code is obviously cleaner and more modular, while also being
1239 more flexible at the same time.
1242 =head2 Adding Methods to Result Classes
1244 In the previous two sections we saw a good example of how we could use
1245 DBIC ResultSet Classes to clean up our code for an entire query (for
1246 example, our "canned searches" that filtered the entire query). We
1247 can do a similar improvement when working with individual rows as
1248 well. Whereas the ResultSet construct is used in DBIC to correspond
1249 to an entire query, the Result Class construct is used to represent a
1250 row. Therefore, we can add row-specific "helper methods" to our Result
1251 Classes stored in C<lib/MyApp/Schema/Result/>. For example, open
1252 C<lib/MyApp/Schema/Result/Authors.pm> and add the following method
1253 (as always, it must be above the closing "C<1;>"):
1261 return $self->first_name . ' ' . $self->last_name;
1264 This will allow us to conveniently retrieve both the first and last
1265 name for an author in one shot. Now open C<root/src/books/list.tt2>
1266 and change the definition of C<tt_authors> from this:
1269 [% tt_authors = [ ];
1270 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1276 [% tt_authors = [ ];
1277 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1280 (Only C<author.last_name> was changed to C<author.full_name> -- the
1281 rest of the file should remain the same.)
1283 Now restart the development server and go to the standard book list
1286 http://localhost:3000/books/list
1288 The "Author(s)" column will now contain both the first and last name.
1289 And, because the concatenation logic was encapsulated inside our
1290 Result Class, it keeps the code inside our .tt template nice and clean
1291 (remember, we want the templates to be as close to pure HTML markup as
1292 possible). Obviously, this capability becomes even more useful as you
1293 use to to remove even more complicated row-specific logic from your
1299 Kennedy Clark, C<hkclark@gmail.com>
1301 Please report any errors, issues or suggestions to the author. The
1302 most recent version of the Catalyst Tutorial can be found at
1303 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
1305 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1306 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).