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 # Set the TT template to use
123 $c->stash->{template} = 'books/create_done.tt2';
126 Notice that Catalyst takes "extra slash-separated information" from the
127 URL and passes it as arguments in C<@_>. The C<url_create> action then
128 uses a simple call to the DBIC C<create> method to add the requested
129 information to the database (with a separate call to
130 C<add_to_book_authors> to update the join table). As do virtually all
131 controller methods (at least the ones that directly handle user input),
132 it then sets the template that should handle this request.
135 =head2 Include a Template for the 'url_create' Action:
137 Edit C<root/src/books/create_done.tt2> and then enter:
139 [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%]
140 [% # Not a good idea for production use, though. :-) 'Indent=1' is -%]
141 [% # optional, but prevents "massive indenting" of deeply nested objects -%]
142 [% USE Dumper(Indent=1) -%]
144 [% # Set the page title. META can 'go back' and set values in templates -%]
145 [% # that have been processed 'before' this template (here it's for -%]
146 [% # root/lib/site/html and root/lib/site/header). Note that META only -%]
147 [% # works on simple/static strings (i.e. there is no variable -%]
148 [% # interpolation). -%]
149 [% META title = 'Book Created' %]
151 [% # Output information about the record that was added. First title. -%]
152 <p>Added book '[% book.title %]'
154 [% # Output the last name of the first author. This is complicated by an -%]
155 [% # issue in TT 2.15 where blessed hash objects are not handled right. -%]
156 [% # First, fetch 'book.authors' from the DB once. -%]
157 [% authors = book.authors %]
158 [% # Now use IF statements to test if 'authors.first' is "working". If so, -%]
159 [% # we use it. Otherwise we use a hack that seems to keep TT 2.15 happy. -%]
160 by '[% authors.first.last_name IF authors.first;
161 authors.list.first.value.last_name IF ! authors.first %]'
163 [% # Output the rating for the book that was added -%]
164 with a rating of [% book.rating %].</p>
166 [% # Provide a link back to the list page -%]
167 [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%]
168 <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
170 [% # Try out the TT Dumper (for development only!) -%]
172 Dump of the 'book' variable:
173 [% Dumper.dump(book) %]
176 The TT C<USE> directive allows access to a variety of plugin modules
177 (TT plugins, that is, not Catalyst plugins) to add extra functionality
178 to the base TT capabilities. Here, the plugin allows
179 L<Data::Dumper|Data::Dumper> "pretty printing" of objects and
180 variables. Other than that, the rest of the code should be familiar
181 from the examples in Chapter 3.
184 =head2 Try the 'url_create' Feature
186 If the application is still running from before, use C<Ctrl-C> to kill
187 it. Then restart the server:
189 $ DBIC_TRACE=1 script/myapp_server.pl
191 Note that new path for C</books/url_create> appears in the startup debug
194 B<TIP>: You can use C<script/myapp_server.pl -r> to have the development
195 server auto-detect changed files and reload itself (if your browser acts
196 odd, you should also try throwing in a C<-k>). If you make changes to
197 the TT templates only, you do not need to reload the development server
198 (only changes to "compiled code" such as Controller and Model C<.pm>
199 files require a reload).
201 Next, use your browser to enter the following URL:
203 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
205 Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by
206 'Stevens' with a rating of 5." along with a dump of the new book model
207 object as it was returned by DBIC. You should also see the following
208 DBIC debug messages displayed in the development server log messages
209 if you have DBIC_TRACE set:
211 INSERT INTO books (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
212 INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): `4', `6'
213 SELECT author.id, author.first_name, author.last_name
214 FROM book_authors me JOIN authors author
215 ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '6'
217 The C<INSERT> statements are obviously adding the book and linking it to
218 the existing record for Richard Stevens. The C<SELECT> statement results
219 from DBIC automatically fetching the book for the C<Dumper.dump(book)>.
221 If you then click the "Return to list" link, you should find that
222 there are now six books shown (if necessary, Shift+Reload or
223 Ctrl+Reload your browser at the C</books/list> page).
226 =head1 CONVERT TO A CHAINED ACTION
228 Although the example above uses the same C<Local> action type for the
229 method that we saw in the previous chapter of the tutorial, there is an
230 alternate approach that allows us to be more specific while also
231 paving the way for more advanced capabilities. Change the method
232 declaration for C<url_create> in C<lib/MyApp/Controller/Books.pm> you
233 entered above to match the following:
235 sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
237 This converts the method to take advantage of the Chained
238 action/dispatch type. Chaining lets you have a single URL
239 automatically dispatch to several controller methods, each of which
240 can have precise control over the number of arguments that it will
241 receive. A chain can essentially be thought of having three parts --
242 a beginning, a middle, and an end. The bullets below summarize the key
243 points behind each of these parts of a chain:
257 B<Use "C<:Chained('/')>" to start a chain>
261 Get arguments through C<CaptureArgs()>
265 Specify the path to match with C<PathPart()>
278 Link to previous part of the chain with C<:Chained('_name_')>
282 Get arguments through C<CaptureArgs()>
286 Specify the path to match with C<PathPart()>
299 Link to previous part of the chain with C<:Chained('_name_')>
303 B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain>
307 Specify the path to match with C<PathPart()>
314 In our C<url_create> method above, we have combined all three parts into
315 a single method: C<:Chained('/')> to start the chain,
316 C<:PathPart('books/url_create')> to specify the base URL to match, and
317 C<:Args(3)> to capture exactly three arguments and to end the chain.
319 As we will see shortly, a chain can consist of as many "links" as you
320 wish, with each part capturing some arguments and doing some work
321 along the way. We will continue to use the Chained action type in this
322 chapter of the tutorial and explore slightly more advanced capabilities
323 with the base method and delete feature below. But Chained dispatch
324 is capable of far more. For additional information, see
325 L<Catalyst::Manual::Intro/Action types>,
326 L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>,
327 and the 2006 Advent calendar entry on the subject:
328 L<http://www.catalystframework.org/calendar/2006/10>.
331 =head2 Try the Chained Action
333 If you look back at the development server startup logs from your
334 initial version of the C<url_create> method (the one using the
335 C<:Local> attribute), you will notice that it produced output similar
338 [debug] Loaded Path actions:
339 .-------------------------------------+--------------------------------------.
341 +-------------------------------------+--------------------------------------+
344 | /books | /books/index |
345 | /books/list | /books/list |
346 | /books/url_create | /books/url_create |
347 '-------------------------------------+--------------------------------------'
349 Now start the development server with our basic chained method in
350 place and the startup debug output should change to something along
351 the lines of the following:
353 [debug] Loaded Path actions:
354 .-------------------------------------+--------------------------------------.
356 +-------------------------------------+--------------------------------------+
359 | /books | /books/index |
360 | /books/list | /books/list |
361 '-------------------------------------+--------------------------------------'
363 [debug] Loaded Chained actions:
364 .-------------------------------------+--------------------------------------.
365 | Path Spec | Private |
366 +-------------------------------------+--------------------------------------+
367 | /books/url_create/*/*/* | /books/url_create |
368 '-------------------------------------+--------------------------------------'
370 C<url_create> has disappeared form the "Loaded Path actions" section
371 but it now shows up under the newly created "Loaded Chained actions"
372 section. And the "/*/*/*" portion clearly shows our requirement for
375 As with our non-chained version of C<url_create>, use your browser to
376 enter the following URL:
378 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
380 You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
381 'Stevens' with a rating of 5." along with a dump of the new book model
382 object. Click the "Return to list" link, and you should find that there
383 are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>).
386 =head2 Refactor to Use a 'base' Method to Start the Chains
388 Let's make a quick update to our initial Chained action to show a
389 little more of the power of chaining. First, open
390 C<lib/MyApp/Controller/Books.pm> in your editor and add the following
395 Can place common logic to start chained dispatch here
399 sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
402 # Store the ResultSet in stash so it's available for other methods
403 $c->stash->{resultset} = $c->model('DB::Books');
405 # Print a message to the debug log
406 $c->log->debug('*** INSIDE BASE METHOD ***');
409 Here we print a log message and store the DBIC ResultSet in
410 C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available
411 for other actions that chain off C<base>. If your controller always
412 needs a book ID as its first argument, you could have the base method
413 capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
414 book object with C<-E<gt>find($id)> and leave it in the stash for
415 later parts of your chains to then act upon. Because we have several
416 actions that don't need to retrieve a book (such as the C<url_create>
417 we are working with now), we will instead add that functionality
418 to a common C<object> action shortly.
420 As for C<url_create>, let's modify it to first dispatch to C<base>.
421 Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for
422 C<url_create> to match the following:
424 sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
426 Next, try out the refactored chain by restarting the development
427 server. Notice that our "Loaded Chained actions" section has changed
430 [debug] Loaded Chained actions:
431 .-------------------------------------+--------------------------------------.
432 | Path Spec | Private |
433 +-------------------------------------+--------------------------------------+
434 | /books/url_create/*/*/* | /books/base (0) |
435 | | => /books/url_create |
436 '-------------------------------------+--------------------------------------'
438 The "Path Spec" is the same, but now it maps to two Private actions as
441 Once again, enter the following URL into your browser:
443 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
445 The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
446 rating of 5." message and a dump of the new book object should appear.
447 Also notice the extra debug message in the development server output
448 from the C<base> method. Click the "Return to list" link, and you
449 should find that there are now eight books shown.
452 =head1 MANUALLY BUILDING A CREATE FORM
454 Although the C<url_create> action in the previous step does begin to
455 reveal the power and flexibility of both Catalyst and DBIC, it's
456 obviously not a very realistic example of how users should be expected
457 to enter data. This section begins to address that concern.
460 =head2 Add Method to Display The Form
462 Edit C<lib/MyApp/Controller/Books.pm> and add the following method:
466 Display form to collect information for book to create
470 sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
473 # Set the TT template to use
474 $c->stash->{template} = 'books/form_create.tt2';
477 This action simply invokes a view containing a form to create a book.
480 =head2 Add a Template for the Form
482 Open C<root/src/books/form_create.tt2> in your editor and enter:
484 [% META title = 'Manual Form Book Create' -%]
486 <form method="post" action="[% c.uri_for('form_create_do') %]">
488 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
489 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
490 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
492 <input type="submit" name="Submit" value="Submit">
495 Note that we have specified the target of the form data as
496 C<form_create_do>, the method created in the section that follows.
499 =head2 Add a Method to Process Form Values and Update Database
501 Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
502 save the form information to the database:
504 =head2 form_create_do
506 Take information from form and add to database
510 sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
513 # Retrieve the values from the form
514 my $title = $c->request->params->{title} || 'N/A';
515 my $rating = $c->request->params->{rating} || 'N/A';
516 my $author_id = $c->request->params->{author_id} || '1';
519 my $book = $c->model('DB::Books')->create({
523 # Handle relationship with author
524 $book->add_to_book_authors({author_id => $author_id});
526 # Store new model object in stash
527 $c->stash->{book} = $book;
529 # Avoid Data::Dumper issue mentioned earlier
530 # You can probably omit this
531 $Data::Dumper::Useperl = 1;
533 # Set the TT template to use
534 $c->stash->{template} = 'books/create_done.tt2';
538 =head2 Test Out The Form
540 If the application is still running from before, use C<Ctrl-C> to kill
541 it. Then restart the server:
543 $ script/myapp_server.pl
545 Notice that the server startup log reflects the two new chained
546 methods that we added:
548 [debug] Loaded Chained actions:
549 .-------------------------------------+--------------------------------------.
550 | Path Spec | Private |
551 +-------------------------------------+--------------------------------------+
552 | /books/form_create | /books/base (0) |
553 | | => /books/form_create |
554 | /books/form_create_do | /books/base (0) |
555 | | => /books/form_create_do |
556 | /books/url_create/*/*/* | /books/base (0) |
557 | | => /books/url_create |
558 '-------------------------------------+--------------------------------------'
560 Point your browser to L<http://localhost:3000/books/form_create> and
561 enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
562 author ID of 4. You should then see the output of the same
563 C<create_done.tt2> template seen in earlier examples. Finally, click
564 "Return to list" to view the full list of books.
566 B<Note:> Having the user enter the primary key ID for the author is
567 obviously crude; we will address this concern with a drop-down list in
571 =head1 A SIMPLE DELETE FEATURE
573 Turning our attention to the Delete portion of CRUD, this section
574 illustrates some basic techniques that can be used to remove information
578 =head2 Include a Delete Link in the List
580 Edit C<root/src/books/list.tt2> and update it to match the following (two
581 sections have changed: 1) the additional '<th>Links</th>' table header,
582 and 2) the four lines for the Delete link near the bottom):
584 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
585 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
586 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
587 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
589 [% # Provide a title to root/lib/site/header -%]
590 [% META title = 'Book List' -%]
593 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
594 [% # Display each book in a table row %]
595 [% FOREACH book IN books -%]
597 <td>[% book.title %]</td>
598 <td>[% book.rating %]</td>
600 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
601 [% # loop in 'side effect notation' to load just the last names of the -%]
602 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
603 [% # a value, so nothing will be printed here. But, if you have something -%]
604 [% # in TT that does return a value and you don't want it printed, you can -%]
605 [% # 1) assign it to a bogus value, or -%]
606 [% # 2) use the CALL keyword to call it and discard the return value. -%]
608 tt_authors.push(author.last_name) FOREACH author = book.authors %]
609 [% # Now use a TT 'virtual method' to display the author count in parens -%]
610 ([% tt_authors.size %])
611 [% # Use another TT vmethod to join & print the names & comma separators -%]
612 [% tt_authors.join(', ') %]
615 [% # Add a link to delete a book %]
616 <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a>
622 The additional code is obviously designed to add a new column to the
623 right side of the table with a C<Delete> "button" (for simplicity, links
624 will be used instead of full HTML buttons; in practice, anything that
625 modifies data should be handled with a form sending a PUT request).
627 Also notice that we are using a more advanced form of C<uri_for> than
628 we have seen before. Here we use
629 C<$c-E<gt>controller-E<gt>action_for> to automatically generate a URI
630 appropriate for that action based on the method we want to link to
631 while inserting the C<book.id> value into the appropriate place. Now,
632 if you ever change C<:PathPart('delete')> in your controller method to
633 C<:PathPart('kill')>, then your links will automatically update
634 without any changes to your .tt2 template file. As long as the name
635 of your method does not change (here, "delete"), then your links will
636 still be correct. There are a few shortcuts and options when using
643 If you are referring to a method in the current controller, you can
644 use C<$self-E<gt>action_for('_method_name_')>.
648 If you are referring to a method in a different controller, you need
649 to include that controller's name as an argument to C<controller()>, as in
650 C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>.
654 B<Note:> In practice you should B<never> use a GET request to delete a
655 record -- always use POST for actions that will modify data. We are
656 doing it here for illustrative and simplicity purposes only.
659 =head2 Add a Common Method to Retrieve a Book for the Chain
661 As mentioned earlier, since we have a mixture of actions that operate
662 on a single book ID and others that do not, we should not have C<base>
663 capture the book ID, find the corresponding book in the database and
664 save it in the stash for later links in the chain. However, just
665 because that logic does not belong in C<base> doesn't mean that we
666 can't create another location to centralize the book lookup code. In
667 our case, we will create a method called C<object> that will store the
668 specific book in the stash. Chains that always operate on a single
669 existing book can chain off this method, but methods such as
670 C<url_create> that don't operate on an existing book can chain
673 To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm>
674 and add the following code:
678 Fetch the specified book object based on the book ID and store
683 sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
684 # $id = primary key of book to delete
685 my ($self, $c, $id) = @_;
687 # Find the book object and store it in the stash
688 $c->stash(object => $c->stash->{resultset}->find($id));
690 # Make sure the lookup was successful. You would probably
691 # want to do something like this in a real app:
692 # $c->detach('/error_404') if !$c->stash->{object};
693 die "Book $id not found!" if !$c->stash->{object};
696 Now, any other method that chains off C<object> will automatically
697 have the appropriate book waiting for it in
698 C<$c-E<gt>stash-E<gt>{object}>.
700 Also note that we are using a different technique for setting
701 C<$c-E<gt>stash>. The advantage of this style is that it lets you set
702 multiple stash variables at a time. For example:
704 $c->stash(object => $c->stash->{resultset}->find($id),
709 $c->stash({object => $c->stash->{resultset}->find($id),
710 another_thing => 1});
712 Either format works, but the C<$c-E<gt>stash(name =E<gt> value);>
713 style is growing in popularity -- you may wish to use it all
714 the time (even when you are only setting a single value).
717 =head2 Add a Delete Action to the Controller
719 Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
728 sub delete :Chained('object') :PathPart('delete') :Args(0) {
731 # Use the book object saved by 'object' and delete it along
732 # with related 'book_authors' entries
733 $c->stash->{object}->delete;
735 # Set a status message to be displayed at the top of the view
736 $c->stash->{status_msg} = "Book deleted.";
738 # Forward to the list action/method in this controller
742 This method first deletes the book object saved by the C<object> method.
743 However, it also removes the corresponding entry from the
744 C<book_authors> table with a cascading delete.
746 Then, rather than forwarding to a "delete done" page as we did with the
747 earlier create example, it simply sets the C<status_msg> to display a
748 notification to the user as the normal list view is rendered.
750 The C<delete> action uses the context C<forward> method to return the
751 user to the book list. The C<detach> method could have also been used.
752 Whereas C<forward> I<returns> to the original action once it is
753 completed, C<detach> does I<not> return. Other than that, the two are
757 =head2 Try the Delete Feature
759 If the application is still running from before, use C<Ctrl-C> to kill
760 it. Then restart the server:
762 $ DBIC_TRACE=1 script/myapp_server.pl
764 The C<delete> method now appears in the "Loaded Chained actions" section
765 of the startup debug output:
767 [debug] Loaded Chained actions:
768 .-------------------------------------+--------------------------------------.
769 | Path Spec | Private |
770 +-------------------------------------+--------------------------------------+
771 | /books/id/*/delete | /books/base (0) |
772 | | -> /books/object (1) |
773 | | => /books/delete |
774 | /books/form_create | /books/base (0) |
775 | | => /books/form_create |
776 | /books/form_create_do | /books/base (0) |
777 | | => /books/form_create_do |
778 | /books/url_create/*/*/* | /books/base (0) |
779 | | => /books/url_create |
780 '-------------------------------------+--------------------------------------'
782 Then point your browser to L<http://localhost:3000/books/list> and click
783 the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green
784 "Book deleted" status message should display at the top of the page,
785 along with a list of the eight remaining books. You will also see the
786 cascading delete operation via the DBIC_TRACE output:
788 SELECT me.id, me.title, me.rating FROM books me WHERE ( ( me.id = ? ) ): '6'
789 DELETE FROM books WHERE ( id = ? ): '6'
790 SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '6'
791 DELETE FROM book_authors WHERE ( author_id = ? AND book_id = ? ): '4', '6'
794 =head2 Fixing a Dangerous URL
796 Note the URL in your browser once you have performed the deletion in the
797 prior step -- it is still referencing the delete action:
799 http://localhost:3000/books/id/6/delete
801 What if the user were to press reload with this URL still active? In
802 this case the redundant delete is harmless (although it does generate
803 an exception screen, it doesn't perform any undesirable actions on the
804 application or database), but in other cases this could clearly be
807 We can improve the logic by converting to a redirect. Unlike
808 C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform
809 a server-side alteration in the flow of processing, a redirect is a
810 client-side mechanism that causes the browser to issue an entirely
811 new request. As a result, the URL in the browser is updated to match
812 the destination of the redirection URL.
814 To convert the forward used in the previous section to a redirect,
815 open C<lib/MyApp/Controller/Books.pm> and edit the existing
816 C<sub delete> method to match:
824 sub delete :Chained('object') :PathPart('delete') :Args(0) {
827 # Use the book object saved by 'object' and delete it along
828 # with related 'book_authors' entries
829 $c->stash->{object}->delete;
831 # Set a status message to be displayed at the top of the view
832 $c->stash->{status_msg} = "Book deleted.";
834 # Redirect the user back to the list page. Note the use
835 # of $self->action_for as earlier in this section (BasicCRUD)
836 $c->response->redirect($c->uri_for($self->action_for('list')));
840 =head2 Try the Delete and Redirect Logic
842 Restart the development server and point your browser to
843 L<http://localhost:3000/books/list> (don't just hit "Refresh" in your
844 browser since we left the URL in an invalid state in the previous
845 section!) and delete the first copy of the remaining two
846 "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return
847 to the L<http://localhost:3000/books/list> URL, so that is an
848 improvement, but notice that I<no green "Book deleted" status message is
849 displayed>. Because the stash is reset on every request (and a redirect
850 involves a second request), the C<status_msg> is cleared before it can
854 =head2 Using 'uri_for' to Pass Query Parameters
856 There are several ways to pass information across a redirect. One
857 option is to use the C<flash> technique that we will see in Chapter 5
858 of this tutorial; however, here we will pass the information via query
859 parameters on the redirect itself. Open
860 C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete>
861 method to match the following:
869 sub delete :Chained('object') :PathPart('delete') :Args(0) {
872 # Use the book object saved by 'object' and delete it along
873 # with related 'book_authors' entries
874 $c->stash->{object}->delete;
876 # Redirect the user back to the list page with status msg as an arg
877 $c->response->redirect($c->uri_for($self->action_for('list'),
878 {status_msg => "Book deleted."}));
881 This modification simply leverages the ability of C<uri_for> to include
882 an arbitrary number of name/value pairs in a hash reference. Next, we
883 need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a
888 [%# Status and error messages %]
889 <span class="message">[% status_msg || c.request.params.status_msg %]</span>
890 <span class="error">[% error_msg %]</span>
891 [%# This is where TT will stick all of your template's contents. -%]
893 </div><!-- end content -->
896 Although the sample above only shows the C<content> div, leave the
897 rest of the file intact -- the only change we made to the C<wrapper.tt2>
898 was to add "C<|| c.request.params.status_msg>" to the
899 C<E<lt>span class="message"E<gt>> line.
902 =head2 Try the Delete and Redirect With Query Param Logic
904 Restart the development server and point your browser to
905 L<http://localhost:3000/books/list> (you should now be able to safely
906 hit "refresh" in your browser). Then delete the remaining copy of
907 "TCPIP_Illustrated_Vol-2". The green "Book deleted" status message
910 B<NOTE:> Another popular method for maintaining server-side
911 information across a redirect is to use the C<flash> technique we
912 discuss in the next chapter of the tutorial,
913 L<Authentication|Catalyst::Manual::Tutorial::Authentication>. While
914 C<flash> is a "slicker" mechanism in that it's all handled by the
915 server and doesn't "pollute" your URLs, B<it is important to note that
916 C<flash> can lead to situations where the wrong information shows up
917 in the wrong browser window if the user has multiple windows or
918 browser tabs open>. For example, Window A causes something to be
919 placed in the stash, but before that window performs a redirect,
920 Window B makes a request to the server and gets the status information
921 that should really go to Window A. For this reason, you may wish
922 to use the "query param" technique shown here in your applications.
925 =head1 EXPLORING THE POWER OF DBIC
927 In this section we will explore some additional capabilities offered
928 by DBIx::Class. Although these features have relatively little to do
929 with Catalyst per se, you will almost certainly want to take advantage
930 of them in your applications.
933 =head2 Add Datetime Columns to Our Existing Books Table
935 Let's add two columns to our existing C<books> table to track when
936 each book was added and when each book is updated:
939 sqlite> ALTER TABLE books ADD created INTEGER;
940 sqlite> ALTER TABLE books ADD updated INTEGER;
941 sqlite> UPDATE books SET created = DATETIME('NOW'), updated = DATETIME('NOW');
942 sqlite> SELECT * FROM books;
943 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35
944 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35
945 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35
946 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35
947 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35
948 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35
952 This will modify the C<books> table to include the two new fields
953 and populate those fields with the current time.
956 =head2 Update DBIC to Automatically Handle the Datetime Columns
958 Next, we should re-run the DBIC helper to update the Result Classes
961 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
962 create=static components=TimeStamp dbi:SQLite:myapp.db
963 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
964 exists "/root/dev/MyApp/script/../t"
965 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
966 Schema dump completed.
967 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
969 Notice that we modified our use of the helper slightly: we told
970 it to include the L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp>
971 in the C<load_components> line of the Result Classes.
973 If you open C<lib/MyApp/Schema/Result/Books.pm> in your editor you
974 should see that the C<created> and C<updated> fields are now included
975 in the call to C<add_columns()>, but our relationship information below
976 the "C<# DO NOT MODIFY...>" line was automatically preserved.
978 While we have this file open, let's update it with some additional
979 information to have DBIC automatically handle the updating of these
980 two fields for us. Insert the following code at the bottom of the
981 file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and
982 B<above> the C<1;> on the last line):
985 # Enable automatic date handling
987 __PACKAGE__->add_columns(
989 { data_type => 'datetime', set_on_create => 1 },
991 { data_type => 'datetime', set_on_create => 1, set_on_update => 1 },
994 This will override the definition for these fields that Schema::Loader
995 placed at the top of the file. The C<set_on_create> and
996 C<set_on_update> options will cause DBIC to automatically update the
997 timestamps in these columns whenever a row is created or modified.
999 To test this out, restart the development server using the
1000 C<DBIC_TRACE=1> option:
1002 DBIC_TRACE=1 script/myapp_server.pl
1004 Then enter the following URL into your web browser:
1006 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
1008 You should get the same "Book Created" screen we saw above. However,
1009 if you now use the sqlite3 command-line tool to dump the C<books> table,
1010 you will see that the new book we added has an appropriate date and
1011 time entered for it (see the last line in the listing below):
1013 sqlite3 myapp.db "select * from books"
1014 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1015 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1016 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35
1017 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1018 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1019 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35
1020 10|TCPIP_Illustrated_Vol-2|5|2009-03-08 16:29:08|2009-03-08 16:29:08
1022 Notice in the debug log that the SQL DBIC generated has changed to
1023 incorporate the datetime logic:
1025 INSERT INTO books (created, rating, title, updated) VALUES (?, ?, ?, ?):
1026 '2009-03-08 16:29:08', '5', 'TCPIP_Illustrated_Vol-2', '2009-03-08 16:29:08'
1027 INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): '4', '10'
1030 =head2 Create a ResultSet Class
1032 An often overlooked but extremely powerful features of DBIC is that it
1033 allows you to supply your own subclasses of C<DBIx::Class::ResultSet>.
1034 It allows you to pull complex and unsightly "query code" out of your
1035 controllers and encapsulate it in a method of your ResultSet Class.
1036 These "canned queries" in your ResultSet Class can then be invoked
1037 via a single call, resulting in much cleaner and easier to read
1040 To illustrate the concept with a fairly simple example, let's create a
1041 method that returns books added in the last 10 minutes. Start by
1042 making a directory where DBIC will look for our ResultSet Class:
1044 mkdir lib/MyApp/Schema/ResultSet
1046 Then open C<lib/MyApp/Schema/ResultSet/Books.pm> and enter the following:
1048 package MyApp::Schema::ResultSet::Books;
1052 use base 'DBIx::Class::ResultSet';
1054 =head2 created_after
1056 A predefined search for recently added books
1061 my ($self, $datetime) = @_;
1063 my $date_str = $self->_source_handle->schema->storage
1064 ->datetime_parser->format_datetime($datetime);
1066 return $self->search({
1067 created => { '>' => $date_str }
1073 Then we need to tell the Result Class to to treat this as a ResultSet
1074 Class. Open C<lib/MyApp/Schema/Result/Books.pm> and add the following
1075 above the "C<1;>" at the bottom of the file:
1078 # Set ResultSet Class
1080 __PACKAGE__->resultset_class('MyApp::Schema::ResultSet::Books');
1082 Then add the following method to the C<lib/MyApp/Controller/Books.pm>:
1086 List recently created books
1090 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
1091 my ($self, $c, $mins) = @_;
1093 # Retrieve all of the book records as book model objects and store in the
1094 # stash where they can be accessed by the TT template, but only
1095 # retrieve books created within the last $min number of minutes
1096 $c->stash->{books} = [$c->model('DB::Books')
1097 ->created_after(DateTime->now->subtract(minutes => $mins))];
1099 # Set the TT template to use. You will almost always want to do this
1100 # in your action methods (action methods respond to user input in
1101 # your controllers).
1102 $c->stash->{template} = 'books/list.tt2';
1105 Now start the development server with C<DBIC_TRACE=1> and try
1106 different values for the minutes argument (the final number value) for
1107 the URL C<http://localhost:3000/books/list_recent/10>. For example,
1108 this would list all books added in the last fifteen minutes:
1110 http://localhost:3000/books/list_recent/15
1112 Depending on how recently you added books, you might want to
1113 try a higher or lower value.
1116 =head2 Chaining ResultSets
1118 One of the most helpful and powerful features in DBIC is that it allows
1119 you to "chain together" a series of queries (note that this has nothing
1120 to do with the "Chained Dispatch" for Catalyst that we were discussing
1121 above). Because each ResultSet returns another ResultSet, you can take
1122 an initial query and immediately feed that into a second query (and so
1123 on for as many queries you need). Note that no matter how many
1124 ResultSets you chain together, the database itself will not be hit until
1125 you use a method that attempts to access the data. And, because this
1126 technique carries over to the ResultSet Class feature we implemented in
1127 the previous section for our "canned search", we can combine the two
1128 capabilities. For example, let's add an action to our C<Books>
1129 controller that lists books that are both recent I<and> have "TCP" in
1130 the title. Open up C<lib/MyApp/Controller/Books.pm> and add the
1133 =head2 list_recent_tcp
1135 List recently created books
1139 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1140 my ($self, $c, $mins) = @_;
1142 # Retrieve all of the book records as book model objects and store in the
1143 # stash where they can be accessed by the TT template, but only
1144 # retrieve books created within the last $min number of minutes
1145 # AND that have 'TCP' in the title
1146 $c->stash->{books} = [$c->model('DB::Books')
1147 ->created_after(DateTime->now->subtract(minutes => $mins))
1148 ->search({title => {'like', '%TCP%'}})
1151 # Set the TT template to use. You will almost always want to do this
1152 # in your action methods (action methods respond to user input in
1153 # your controllers).
1154 $c->stash->{template} = 'books/list.tt2';
1157 To try this out, restart the development server with:
1159 DBIC_TRACE=1 script/myapp_server.pl
1161 And enter the following URL into your browser:
1163 http://localhost:3000/books/list_recent_tcp/100
1165 And you should get a list of books added in the last 100 minutes that
1166 contain the string "TCP" in the title. However, if you look at all
1167 books within the last 100 minutes, you should get a longer list
1168 (again, you might have to adjust the number of minutes depending on
1169 how recently you added books to your database):
1171 http://localhost:3000/books/list_recent/100
1173 Take a look at the DBIC_TRACE output in the development server log for
1174 the first URL and you should see something similar to the following:
1176 SELECT me.id, me.title, me.rating, me.created, me.updated FROM books me
1177 WHERE ( ( ( title LIKE ? ) AND ( created > ? ) ) ): '%TCP%', '2009-03-08 14:52:54'
1179 However, let's not pollute our controller code with this raw "TCP"
1180 query -- it would be cleaner to encapsulate that code in a method on
1181 our ResultSet Class. To do this, open
1182 C<lib/MyApp/Schema/ResultSet/Books.pm> and add the following method:
1186 A predefined search for books with a 'LIKE' search in the string
1191 my ($self, $title_str) = @_;
1193 return $self->search({
1194 title => { 'like' => "%$title_str%" }
1198 We defined the search string as C<$title_str> to make the method more
1199 flexible. Now update the C<list_recent_tcp> method in
1200 C<lib/MyApp/Controller/Books.pm> to match the following (we have
1201 replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line
1202 shown here -- the rest of the method should be the same):
1204 =head2 list_recent_tcp
1206 List recently created books
1210 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1211 my ($self, $c, $mins) = @_;
1213 # Retrieve all of the book records as book model objects and store in the
1214 # stash where they can be accessed by the TT template, but only
1215 # retrieve books created within the last $min number of minutes
1216 # AND that have 'TCP' in the title
1217 $c->stash->{books} = [$c->model('DB::Books')
1218 ->created_after(DateTime->now->subtract(minutes => $mins))
1222 # Set the TT template to use. You will almost always want to do this
1223 # in your action methods (action methods respond to user input in
1224 # your controllers).
1225 $c->stash->{template} = 'books/list.tt2';
1228 Then restart the development server and try out the C<list_recent_tcp>
1229 and C<list_recent> URL as we did above. It should work just the same,
1230 but our code is obviously cleaner and more modular, while also being
1231 more flexible at the same time.
1234 =head2 Adding Methods to Result Classes
1236 In the previous two sections we saw a good example of how we could use
1237 DBIC ResultSet Classes to clean up our code for an entire query (for
1238 example, our "canned searches" that filtered the entire query). We
1239 can do a similar improvement when working with individual rows as
1240 well. Whereas the ResultSet construct is used in DBIC to correspond
1241 to an entire query, the Result Class construct is used to represent a
1242 row. Therefore, we can add row-specific "helper methods" to our Result
1243 Classes stored in C<lib/MyApp/Schema/Result/>. For example, open
1244 C<lib/MyApp/Schema/Result/Authors.pm> and add the following method
1245 (as always, it must be above the closing "C<1;>"):
1253 return $self->first_name . ' ' . $self->last_name;
1256 This will allow us to conveniently retrieve both the first and last
1257 name for an author in one shot. Now open C<root/src/books/list.tt2>
1258 and change the definition of C<tt_authors> from this:
1261 [% tt_authors = [ ];
1262 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1268 [% tt_authors = [ ];
1269 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1272 (Only C<author.last_name> was changed to C<author.full_name> -- the
1273 rest of the file should remain the same.)
1275 Now restart the development server and go to the standard book list
1278 http://localhost:3000/books/list
1280 The "Author(s)" column will now contain both the first and last name.
1281 And, because the concatenation logic was encapsulated inside our
1282 Result Class, it keeps the code inside our .tt template nice and clean
1283 (remember, we want the templates to be as close to pure HTML markup as
1284 possible). Obviously, this capability becomes even more useful as you
1285 use to to remove even more complicated row-specific logic from your
1291 Kennedy Clark, C<hkclark@gmail.com>
1293 Please report any errors, issues or suggestions to the author. The
1294 most recent version of the Catalyst Tutorial can be found at
1295 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
1297 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1298 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).