3 Catalyst::Manual::Tutorial::04_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::01_Intro>
20 L<Catalyst Basics|Catalyst::Manual::Tutorial::02_CatalystBasics>
24 L<More Catalyst Basics|Catalyst::Manual::Tutorial::03_MoreCatalystBasics>
32 L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>
36 L<Authorization|Catalyst::Manual::Tutorial::06_Authorization>
40 L<Debugging|Catalyst::Manual::Tutorial::07_Debugging>
44 L<Testing|Catalyst::Manual::Tutorial::08_Testing>
48 L<Advanced CRUD|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
52 L<Appendices|Catalyst::Manual::Tutorial::10_Appendices>
59 This chapter of the tutorial builds on the fairly primitive application
61 L<Chapter 3|Catalyst::Manual::Tutorial::03_MoreCatalystBasics> to add
62 basic support for Create, Read, Update, and Delete (CRUD) of C<Book>
63 objects. Note that the 'list' function in
64 L<Chapter 3|Catalyst::Manual::Tutorial::03_MoreCatalystBasics> already
65 implements the Read portion of CRUD (although Read normally refers to
66 reading a single object; you could implement full Read functionality
67 using the techniques introduced below). This section will focus on the
68 Create and Delete aspects of CRUD. More advanced capabilities,
69 including full Update functionality, will be addressed in
70 L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>.
72 Although this chapter of the tutorial will show you how to build CRUD
73 functionality yourself, another option is to use a "CRUD builder" type
74 of tool to automate the process. You get less control, but it can be
75 quick and easy. For example, see L<Catalyst::Plugin::AutoCRUD>,
76 L<CatalystX::CRUD>, and L<CatalystX::CRUD::YUI>.
78 Source code for the tutorial in included in the F</root/Final> directory
79 of the Tutorial Virtual machine (one subdirectory per chapter). There
80 are also instructions for downloading the code in
81 L<Catalyst::Manual::Tutorial::01_Intro>.
84 =head1 FORMLESS SUBMISSION
86 Our initial attempt at object creation will utilize the "URL arguments"
87 feature of Catalyst (we will employ the more common form-based
88 submission in the sections that follow).
91 =head2 Include a Create Action in the Books Controller
93 Edit C<lib/MyApp/Controller/Books.pm> and enter the following method:
97 Create a book with the supplied title, rating, and author
101 sub url_create :Local {
102 # In addition to self & context, get the title, rating, &
103 # author_id args from the URL. Note that Catalyst automatically
104 # puts extra information after the "/<controller_name>/<action_name/"
105 # into @_. The args are separated by the '/' char on the URL.
106 my ($self, $c, $title, $rating, $author_id) = @_;
108 # Call create() on the book model object. Pass the table
109 # columns/field values we want to set as hash values
110 my $book = $c->model('DB::Book')->create({
115 # Add a record to the join table for this book, mapping to
117 $book->add_to_book_authors({author_id => $author_id});
118 # Note: Above is a shortcut for this:
119 # $book->create_related('book_authors', {author_id => $author_id});
121 # Assign the Book object to the stash for display and set template
122 $c->stash(book => $book,
123 template => 'books/create_done.tt2');
125 # Disable caching for this page
126 $c->response->header('Cache-Control' => 'no-cache');
129 Notice that Catalyst takes "extra slash-separated information" from the
130 URL and passes it as arguments in C<@_> (as long as the number of
131 arguments is not "fixed" using an attribute like C<:Args(0)>). The
132 C<url_create> action then uses a simple call to the DBIC C<create>
133 method to add the requested information to the database (with a separate
134 call to C<add_to_book_authors> to update the join table). As do
135 virtually all controller methods (at least the ones that directly handle
136 user input), it then sets the template that should handle this request.
138 Also note that we are explicitly setting a C<no-cache> "Cache-Control"
139 header to force browsers using the page to get a fresh copy every time.
140 You could even move this to a C<auto> method in
141 C<lib/MyApp/Controller/Root.pm> and it would automatically get applied
142 to every page in the whole application via a single line of code
143 (remember from Chapter 3, that every C<auto> method gets run in the
144 Controller hierarchy).
147 =head2 Include a Template for the 'url_create' Action:
149 Edit C<root/src/books/create_done.tt2> and then enter:
151 [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%]
152 [% # Not a good idea for production use, though. :-) 'Indent=1' is -%]
153 [% # optional, but prevents "massive indenting" of deeply nested objects -%]
154 [% USE Dumper(Indent=1) -%]
156 [% # Set the page title. META can 'go back' and set values in templates -%]
157 [% # that have been processed 'before' this template (here it's updating -%]
158 [% # the title in the root/src/wrapper.tt2 wrapper template). Note that -%]
159 [% # META only works on simple/static strings (i.e. there is no variable -%]
160 [% # interpolation -- if you need dynamic/interpolated content in your -%]
161 [% # title, set "$c->stash(title => $something)" in the controller). -%]
162 [% META title = 'Book Created' %]
164 [% # Output information about the record that was added. First title. -%]
165 <p>Added book '[% book.title %]'
167 [% # Then, output the last name of the first author -%]
168 by '[% book.authors.first.last_name %]'
170 [% # Then, output the rating for the book that was added -%]
171 with a rating of [% book.rating %].</p>
173 [% # Provide a link back to the list page. 'c.uri_for' builds -%]
174 [% # a full URI; e.g., 'http://localhost:3000/books/list' -%]
175 <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
177 [% # Try out the TT Dumper (for development only!) -%]
179 Dump of the 'book' variable:
180 [% Dumper.dump(book) %]
183 The TT C<USE> directive allows access to a variety of plugin modules (TT
184 plugins, that is, not Catalyst plugins) to add extra functionality to
185 the base TT capabilities. Here, the plugin allows L<Data::Dumper>
186 "pretty printing" of objects and variables. Other than that, the rest
187 of the code should be familiar from the examples in Chapter 3.
190 =head2 Try the 'url_create' Feature
192 Make sure the development server is running with the "-r" restart
195 $ DBIC_TRACE=1 script/myapp_server.pl -r
197 Note that new path for C</books/url_create> appears in the startup debug
200 Next, use your browser to enter the following URL:
202 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
204 Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by
205 'Stevens' with a rating of 5." along with a dump of the new book model
206 object as it was returned by DBIC. You should also see the following
207 DBIC debug messages displayed in the development server log messages if
208 you have DBIC_TRACE set:
210 INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
211 INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6'
213 The C<INSERT> statements are obviously adding the book and linking it to
214 the existing record for Richard Stevens. The C<SELECT> statement
215 results from DBIC automatically fetching the book for the
216 C<Dumper.dump(book)>.
218 If you then click the "Return to list" link, you should find that there
219 are now six books shown (if necessary, Shift+Reload or Ctrl+Reload your
220 browser at the C</books/list> page). You should now see the six DBIC
221 debug messages similar to the following (where N=1-6):
223 SELECT author.id, author.first_name, author.last_name
224 FROM book_author me JOIN author author
225 ON author.id = me.author_id WHERE ( me.book_id = ? ): 'N'
228 =head1 CONVERT TO A CHAINED ACTION
230 Although the example above uses the same C<Local> action type for the
231 method that we saw in the previous chapter of the tutorial, there is an
232 alternate approach that allows us to be more specific while also paving
233 the way for more advanced capabilities. Change the method declaration
234 for C<url_create> in C<lib/MyApp/Controller/Books.pm> you entered above
235 to match the following:
237 sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
238 # In addition to self & context, get the title, rating, &
239 # author_id args from the URL. Note that Catalyst automatically
240 # puts the first 3 arguments worth of extra information after the
241 # "/<controller_name>/<action_name/" into @_ because we specified
242 # "Args(3)". The args are separated by the '/' char on the URL.
243 my ($self, $c, $title, $rating, $author_id) = @_;
247 This converts the method to take advantage of the Chained
248 action/dispatch type. Chaining lets you have a single URL automatically
249 dispatch to several controller methods, each of which can have precise
250 control over the number of arguments that it will receive. A chain can
251 essentially be thought of having three parts -- a beginning, a middle,
252 and an end. The bullets below summarize the key points behind each of
253 these parts of a chain:
267 B<Use "C<:Chained('/')>" to start a chain>
271 Get arguments through C<CaptureArgs()>
275 Specify the path to match with C<PathPart()>
288 Link to previous part of the chain with C<:Chained('_name_')>
292 Get arguments through C<CaptureArgs()>
296 Specify the path to match with C<PathPart()>
309 Link to previous part of the chain with C<:Chained('_name_')>
313 B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain>
317 Specify the path to match with C<PathPart()>
324 In our C<url_create> method above, we have combined all three parts into
325 a single method: C<:Chained('/')> to start the chain,
326 C<:PathPart('books/url_create')> to specify the base URL to match, and
327 C<:Args(3)> to capture exactly three arguments and to end the chain.
329 As we will see shortly, a chain can consist of as many "links" as you
330 wish, with each part capturing some arguments and doing some work along
331 the way. We will continue to use the Chained action type in this
332 chapter of the tutorial and explore slightly more advanced capabilities
333 with the base method and delete feature below. But Chained dispatch is
334 capable of far more. For additional information, see
335 L<Catalyst::Manual::Intro/Action types>,
336 L<Catalyst::DispatchType::Chained>, and the 2006 Advent calendar entry
337 on the subject: L<http://www.catalystframework.org/calendar/2006/10>.
340 =head2 Try the Chained Action
342 If you look back at the development server startup logs from your
343 initial version of the C<url_create> method (the one using the C<:Local>
344 attribute), you will notice that it produced output similar to the
347 [debug] Loaded Path actions:
348 .-------------------------------------+--------------------------------------.
350 +-------------------------------------+--------------------------------------+
353 | /books | /books/index |
354 | /books/list | /books/list |
355 | /books/url_create | /books/url_create |
356 '-------------------------------------+--------------------------------------'
358 When the development server restarts after our conversion to Chained
359 dispatch, the debug output should change to something along the lines of
362 [debug] Loaded Path actions:
363 .-------------------------------------+--------------------------------------.
365 +-------------------------------------+--------------------------------------+
368 | /books | /books/index |
369 | /books/list | /books/list |
370 '-------------------------------------+--------------------------------------'
372 [debug] Loaded Chained actions:
373 .-------------------------------------+--------------------------------------.
374 | Path Spec | Private |
375 +-------------------------------------+--------------------------------------+
376 | /books/url_create/*/*/* | /books/url_create |
377 '-------------------------------------+--------------------------------------'
379 C<url_create> has disappeared from the "Loaded Path actions" section but
380 it now shows up under the newly created "Loaded Chained actions"
381 section. And the "/*/*/*" portion clearly shows our requirement for
384 As with our non-chained version of C<url_create>, use your browser to
385 enter the following URL:
387 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
389 You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
390 'Stevens' with a rating of 5." along with a dump of the new book model
391 object. Click the "Return to list" link, and you should find that there
392 are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>).
395 =head2 Refactor to Use a 'base' Method to Start the Chains
397 Let's make a quick update to our initial Chained action to show a little
398 more of the power of chaining. First, open
399 C<lib/MyApp/Controller/Books.pm> in your editor and add the following
404 Can place common logic to start chained dispatch here
408 sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
411 # Store the ResultSet in stash so it's available for other methods
412 $c->stash(resultset => $c->model('DB::Book'));
414 # Print a message to the debug log
415 $c->log->debug('*** INSIDE BASE METHOD ***');
418 Here we print a log message and store the DBIC ResultSet in
419 C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available
420 for other actions that chain off C<base>. If your controller always
421 needs a book ID as its first argument, you could have the base method
422 capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
423 book object with C<-E<gt>find($id)> and leave it in the stash for later
424 parts of your chains to then act upon. Because we have several actions
425 that don't need to retrieve a book (such as the C<url_create> we are
426 working with now), we will instead add that functionality to a common
427 C<object> action shortly.
429 As for C<url_create>, let's modify it to first dispatch to C<base>.
430 Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for
431 C<url_create> to match the following:
433 sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
435 Once you save C<lib/MyApp/Controller/Books.pm>, notice that the
436 development server will restart and our "Loaded Chained actions" section
437 will changed slightly:
439 [debug] Loaded Chained actions:
440 .-------------------------------------+--------------------------------------.
441 | Path Spec | Private |
442 +-------------------------------------+--------------------------------------+
443 | /books/url_create/*/*/* | /books/base (0) |
444 | | => /books/url_create |
445 '-------------------------------------+--------------------------------------'
447 The "Path Spec" is the same, but now it maps to two Private actions as
448 we would expect. The C<base> method is being triggered by the C</books>
449 part of the URL. However, the processing then continues to the
450 C<url_create> method because this method "chained" off C<base> and
451 specified C<:PathPart('url_create')> (note that we could have omitted
452 the "PathPart" here because it matches the name of the method, but we
453 will include it to make the logic as explicit as possible).
455 Once again, enter the following URL into your browser:
457 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
459 The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
460 rating of 5." message and a dump of the new book object should appear.
461 Also notice the extra "INSIDE BASE METHOD" debug message in the
462 development server output from the C<base> method. Click the "Return to
463 list" link, and you should find that there are now eight books shown.
464 (You may have a larger number of books if you repeated any of the
465 "create" actions more than once. Don't worry about it as long as the
466 number of books is appropriate for the number of times you added new
467 books... there should be the original five books added via
468 C<myapp01.sql> plus one additional book for each time you ran one of the
469 url_create variations above.)
472 =head1 MANUALLY BUILDING A CREATE FORM
474 Although the C<url_create> action in the previous step does begin to
475 reveal the power and flexibility of both Catalyst and DBIC, it's
476 obviously not a very realistic example of how users should be expected
477 to enter data. This section begins to address that concern (but just
478 barely, see L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
479 for better options for handling web-based forms).
482 =head2 Add Method to Display The Form
484 Edit C<lib/MyApp/Controller/Books.pm> and add the following method:
488 Display form to collect information for book to create
492 sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
495 # Set the TT template to use
496 $c->stash(template => 'books/form_create.tt2');
499 This action simply invokes a view containing a form to create a book.
502 =head2 Add a Template for the Form
504 Open C<root/src/books/form_create.tt2> in your editor and enter:
506 [% META title = 'Manual Form Book Create' -%]
508 <form method="post" action="[% c.uri_for('form_create_do') %]">
510 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
511 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
512 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
514 <input type="submit" name="Submit" value="Submit">
517 Note that we have specified the target of the form data as
518 C<form_create_do>, the method created in the section that follows.
521 =head2 Add a Method to Process Form Values and Update Database
523 Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
524 save the form information to the database:
526 =head2 form_create_do
528 Take information from form and add to database
532 sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
535 # Retrieve the values from the form
536 my $title = $c->request->params->{title} || 'N/A';
537 my $rating = $c->request->params->{rating} || 'N/A';
538 my $author_id = $c->request->params->{author_id} || '1';
541 my $book = $c->model('DB::Book')->create({
545 # Handle relationship with author
546 $book->add_to_book_authors({author_id => $author_id});
547 # Note: Above is a shortcut for this:
548 # $book->create_related('book_authors', {author_id => $author_id});
550 # Store new model object in stash and set template
551 $c->stash(book => $book,
552 template => 'books/create_done.tt2');
556 =head2 Test Out The Form
558 Notice that the server startup log reflects the two new chained methods
561 [debug] Loaded Chained actions:
562 .-------------------------------------+--------------------------------------.
563 | Path Spec | Private |
564 +-------------------------------------+--------------------------------------+
565 | /books/form_create | /books/base (0) |
566 | | => /books/form_create |
567 | /books/form_create_do | /books/base (0) |
568 | | => /books/form_create_do |
569 | /books/url_create/*/*/* | /books/base (0) |
570 | | => /books/url_create |
571 '-------------------------------------+--------------------------------------'
573 Point your browser to L<http://localhost:3000/books/form_create> and
574 enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
575 author ID of 4. You should then see the output of the same
576 C<create_done.tt2> template seen in earlier examples. Finally, click
577 "Return to list" to view the full list of books.
579 B<Note:> Having the user enter the primary key ID for the author is
580 obviously crude; we will address this concern with a drop-down list and
581 add validation to our forms in
582 L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>.
585 =head1 A SIMPLE DELETE FEATURE
587 Turning our attention to the Delete portion of CRUD, this section
588 illustrates some basic techniques that can be used to remove information
592 =head2 Include a Delete Link in the List
594 Edit C<root/src/books/list.tt2> and update it to match the following
595 (two sections have changed: 1) the additional '<th>Links</th>' table
596 header, and 2) the five lines for the Delete link near the bottom):
598 [% # This is a TT comment. -%]
600 [%- # Provide a title -%]
601 [% META title = 'Book List' -%]
603 [% # Note That the '-' at the beginning or end of TT code -%]
604 [% # "chomps" the whitespace/newline at that end of the -%]
605 [% # output (use View Source in browser to see the effect) -%]
607 [% # Some basic HTML with a loop to display books -%]
609 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
610 [% # Display each book in a table row %]
611 [% FOREACH book IN books -%]
613 <td>[% book.title %]</td>
614 <td>[% book.rating %]</td>
616 [% # NOTE: See Chapter 4 for a better way to do this! -%]
617 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
618 [% # loop in 'side effect notation' to load just the last names of the -%]
619 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
620 [% # a value, so nothing will be printed here. But, if you have something -%]
621 [% # in TT that does return a value and you don't want it printed, you -%]
622 [% # 1) assign it to a bogus value, or -%]
623 [% # 2) use the CALL keyword to call it and discard the return value. -%]
625 tt_authors.push(author.last_name) FOREACH author = book.authors %]
626 [% # Now use a TT 'virtual method' to display the author count in parens -%]
627 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
628 ([% tt_authors.size | html %])
629 [% # Use another TT vmethod to join & print the names & comma separators -%]
630 [% tt_authors.join(', ') | html %]
633 [% # Add a link to delete a book %]
635 c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a>
641 The additional code is obviously designed to add a new column to the
642 right side of the table with a C<Delete> "button" (for simplicity, links
643 will be used instead of full HTML buttons; but, in practice, anything
644 that modifies data should be handled with a form sending a POST
647 Also notice that we are using a more advanced form of C<uri_for> than we
648 have seen before. Here we use C<$c-E<gt>controller-E<gt>action_for> to
649 automatically generate a URI appropriate for that action based on the
650 method we want to link to while inserting the C<book.id> value into the
651 appropriate place. Now, if you ever change C<:PathPart('delete')> in
652 your controller method to something like C<:PathPart('kill')>, then your
653 links will automatically update without any changes to your .tt2
654 template file. As long as the name of your method does not change
655 (here, "delete"), then your links will still be correct. There are a
656 few shortcuts and options when using C<action_for()>:
662 If you are referring to a method in the current controller, you can use
663 C<$self-E<gt>action_for('_method_name_')>.
667 If you are referring to a method in a different controller, you need to
668 include that controller's name as an argument to C<controller()>, as in
669 C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>.
673 B<Note:> In practice you should B<never> use a GET request to delete a
674 record -- always use POST for actions that will modify data. We are
675 doing it here for illustrative and simplicity purposes only.
678 =head2 Add a Common Method to Retrieve a Book for the Chain
680 As mentioned earlier, since we have a mixture of actions that operate on
681 a single book ID and others that do not, we should not have C<base>
682 capture the book ID, find the corresponding book in the database and
683 save it in the stash for later links in the chain. However, just
684 because that logic does not belong in C<base> doesn't mean that we can't
685 create another location to centralize the book lookup code. In our
686 case, we will create a method called C<object> that will store the
687 specific book in the stash. Chains that always operate on a single
688 existing book can chain off this method, but methods such as
689 C<url_create> that don't operate on an existing book can chain directly
692 To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm> and
693 add the following code:
697 Fetch the specified book object based on the book ID and store
702 sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
703 # $id = primary key of book to delete
704 my ($self, $c, $id) = @_;
706 # Find the book object and store it in the stash
707 $c->stash(object => $c->stash->{resultset}->find($id));
709 # Make sure the lookup was successful. You would probably
710 # want to do something like this in a real app:
711 # $c->detach('/error_404') if !$c->stash->{object};
712 die "Book $id not found!" if !$c->stash->{object};
714 # Print a message to the debug log
715 $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***");
718 Now, any other method that chains off C<object> will automatically have
719 the appropriate book waiting for it in C<$c-E<gt>stash-E<gt>{object}>.
722 =head2 Add a Delete Action to the Controller
724 Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
733 sub delete :Chained('object') :PathPart('delete') :Args(0) {
736 # Use the book object saved by 'object' and delete it along
737 # with related 'book_author' entries
738 $c->stash->{object}->delete;
740 # Set a status message to be displayed at the top of the view
741 $c->stash->{status_msg} = "Book deleted.";
743 # Forward to the list action/method in this controller
747 This method first deletes the book object saved by the C<object> method.
748 However, it also removes the corresponding entry from the C<book_author>
749 table with a cascading delete.
751 Then, rather than forwarding to a "delete done" page as we did with the
752 earlier create example, it simply sets the C<status_msg> to display a
753 notification to the user as the normal list view is rendered.
755 The C<delete> action uses the context C<forward> method to return the
756 user to the book list. The C<detach> method could have also been used.
757 Whereas C<forward> I<returns> to the original action once it is
758 completed, C<detach> does I<not> return. Other than that, the two are
762 =head2 Try the Delete Feature
764 Once you save the Books controller, the server should automatically
765 restart. The C<delete> method should now appear in the "Loaded Chained
766 actions" section of the startup debug output:
768 [debug] Loaded Chained actions:
769 .-------------------------------------+--------------------------------------.
770 | Path Spec | Private |
771 +-------------------------------------+--------------------------------------+
772 | /books/id/*/delete | /books/base (0) |
773 | | -> /books/object (1) |
774 | | => /books/delete |
775 | /books/form_create | /books/base (0) |
776 | | => /books/form_create |
777 | /books/form_create_do | /books/base (0) |
778 | | => /books/form_create_do |
779 | /books/url_create/*/*/* | /books/base (0) |
780 | | => /books/url_create |
781 '-------------------------------------+--------------------------------------'
783 Then point your browser to L<http://localhost:3000/books/list> and click
784 the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green
785 "Book deleted" status message should display at the top of the page,
786 along with a list of the eight remaining books. You will also see the
787 cascading delete operation via the DBIC_TRACE output:
789 SELECT me.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6'
790 DELETE FROM book WHERE ( id = ? ): '6'
793 =head2 Fixing a Dangerous URL
795 Note the URL in your browser once you have performed the deletion in the
796 prior step -- it is still referencing the delete action:
798 http://localhost:3000/books/id/6/delete
800 What if the user were to press reload with this URL still active? In
801 this case the redundant delete is harmless (although it does generate an
802 exception screen, it doesn't perform any undesirable actions on the
803 application or database), but in other cases this could clearly lead to
806 We can improve the logic by converting to a redirect. Unlike
807 C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform a
808 server-side alteration in the flow of processing, a redirect is a
809 client-side mechanism that causes the browser to issue an entirely new
810 request. As a result, the URL in the browser is updated to match the
811 destination of the redirection URL.
813 To convert the forward used in the previous section to a redirect, open
814 C<lib/MyApp/Controller/Books.pm> and edit the existing C<sub delete>
823 sub delete :Chained('object') :PathPart('delete') :Args(0) {
826 # Use the book object saved by 'object' and delete it along
827 # with related 'book_author' entries
828 $c->stash->{object}->delete;
830 # Set a status message to be displayed at the top of the view
831 $c->stash->{status_msg} = "Book deleted.";
833 # Redirect the user back to the list page. Note the use
834 # of $self->action_for as earlier in this section (BasicCRUD)
835 $c->response->redirect($c->uri_for($self->action_for('list')));
839 =head2 Try the Delete and Redirect Logic
841 Point your browser to L<http://localhost:3000/books/list> (don't just
842 hit "Refresh" in your browser since we left the URL in an invalid state
843 in the previous section!) and delete the first copy of the remaining two
844 "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return
845 to the L<http://localhost:3000/books/list> URL, so that is an
846 improvement, but notice that I<no green "Book deleted" status message is
847 displayed>. Because the stash is reset on every request (and a redirect
848 involves a second request), the C<status_msg> is cleared before it can
852 =head2 Using 'uri_for' to Pass Query Parameters
854 There are several ways to pass information across a redirect. One option
855 is to use the C<flash> technique that we will see in
856 L<Chapter 5|Catalyst::Manual::Tutorial::05_Authentication> of this
857 tutorial; however, here we will pass the information via query
858 parameters on the redirect itself. Open
859 C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete>
860 method to match the following:
868 sub delete :Chained('object') :PathPart('delete') :Args(0) {
871 # Use the book object saved by 'object' and delete it along
872 # with related 'book_author' entries
873 $c->stash->{object}->delete;
875 # Redirect the user back to the list page with status msg as an arg
876 $c->response->redirect($c->uri_for($self->action_for('list'),
877 {status_msg => "Book deleted."}));
880 This modification simply leverages the ability of C<uri_for> to include
881 an arbitrary number of name/value pairs in a hash reference. Next, we
882 need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a
887 [%# Status and error messages %]
888 <span class="message">[%
889 status_msg || c.request.params.status_msg | html %]</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 rest
897 of the file intact -- the only change we made to the C<wrapper.tt2> was
898 to add "C<|| c.request.params.status_msg>" to the
899 C<E<lt>span class="message"E<gt>> line. Note that we definitely want
900 the "C<| html>" TT filter here since it would be easy for users to
901 modify the message on the URL and possibly inject harmful code into the
902 application if we left that off.
905 =head2 Try the Delete and Redirect With Query Param Logic
907 Point your browser to L<http://localhost:3000/books/list> (you should
908 now be able to safely hit "refresh" in your browser). Then delete the
909 remaining copy of "TCPIP_Illustrated_Vol-2". The green "Book deleted"
910 status message should return. But notice that you can now hit the
911 "Reload" button in your browser and it just redisplays the book list
912 (and it correctly shows it without the "Book deleted" message on
915 B<NOTE:> Be sure to check out
916 L<Authentication|Catalyst::Manual::Tutorial::05_Authentication> where we
917 use an improved technique that is better suited to your real world
921 =head1 EXPLORING THE POWER OF DBIC
923 In this section we will explore some additional capabilities offered by
924 L<DBIx::Class>. Although these features have relatively little to do
925 with Catalyst per se, you will almost certainly want to take advantage
926 of them in your applications.
929 =head2 Add Datetime Columns to Our Existing Books Table
931 Let's add two columns to our existing C<books> table to track when each
932 book was added and when each book is updated:
935 sqlite> ALTER TABLE book ADD created TIMESTAMP;
936 sqlite> ALTER TABLE book ADD updated TIMESTAMP;
937 sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
938 sqlite> SELECT * FROM book;
939 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
940 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
941 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
942 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
943 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
944 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
948 Here are the commands without the surrounding sqlite3 prompt and output
949 in case you want to cut and paste them as a single block (but still
950 start sqlite3 before you paste these in):
952 ALTER TABLE book ADD created TIMESTAMP;
953 ALTER TABLE book ADD updated TIMESTAMP;
954 UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
957 This will modify the C<books> table to include the two new fields and
958 populate those fields with the current time.
961 =head2 Update DBIx::Class to Automatically Handle the Datetime Columns
963 Next, we should re-run the DBIC helper to update the Result Classes with
966 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
967 create=static components=TimeStamp dbi:SQLite:myapp.db \
968 on_connect_do="PRAGMA foreign_keys = ON"
969 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
970 exists "/root/dev/MyApp/script/../t"
971 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
972 Schema dump completed.
973 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
975 Notice that we modified our use of the helper slightly: we told it to
976 include the L<DBIx::Class::TimeStamp> in the C<load_components> line of
979 If you open C<lib/MyApp/Schema/Result/Book.pm> in your editor you should
980 see that the C<created> and C<updated> fields are now included in the
981 call to C<add_columns()>. However, also notice that the C<many_to_many>
982 relationships we manually added below the "C<# DO NOT MODIFY...>" line
983 were automatically preserved.
985 While we C<lib/MyApp/Schema/Result/Book.pm> open, let's update it with
986 some additional information to have DBIC automatically handle the
987 updating of these two fields for us. Insert the following code at the
988 bottom of the file (it B<must> be B<below> the "C<# DO NOT MODIFY...>"
989 line and B<above> the C<1;> on the last line):
992 # Enable automatic date handling
994 __PACKAGE__->add_columns(
996 { data_type => 'timestamp', set_on_create => 1 },
998 { data_type => 'timestamp', set_on_create => 1, set_on_update => 1 },
1001 This will override the definition for these fields that Schema::Loader
1002 placed at the top of the file. The C<set_on_create> and
1003 C<set_on_update> options will cause DBIx::Class to automatically update
1004 the timestamps in these columns whenever a row is created or modified.
1006 B<Note> that adding the lines above will cause the development server to
1007 automatically restart if you are running it with the "-r" option. In
1008 other words, the development server is smart enough to restart not only
1009 for code under the C<MyApp/Controller/>, C<MyApp/Model/>, and
1010 C<MyApp/View/> directories, but also under other directions such as our
1011 "external DBIC model" in C<MyApp/Schema/>. However, also note that it's
1012 smart enough to B<not> restart when you edit your C<.tt2> files under
1015 Then enter the following URL into your web browser:
1017 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
1019 You should get the same "Book Created" screen we saw earlier. However, if
1020 you now use the sqlite3 command-line tool to dump the C<books> table,
1021 you will see that the new book we added has an appropriate date and time
1022 entered for it (see the last line in the listing below):
1024 $ sqlite3 myapp.db "select * from book"
1025 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1026 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1027 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
1028 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1029 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1030 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1031 10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42
1033 Notice in the debug log that the SQL DBIC generated has changed to
1034 incorporate the datetime logic:
1036 INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ):
1037 '2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42'
1038 INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10'
1041 =head2 Create a ResultSet Class
1043 An often overlooked but extremely powerful features of DBIC is that it
1044 allows you to supply your own subclasses of C<DBIx::Class::ResultSet>.
1045 This can be used to pull complex and unsightly "query code" out of your
1046 controllers and encapsulate it in a method of your ResultSet Class.
1047 These "canned queries" in your ResultSet Class can then be invoked via a
1048 single call, resulting in much cleaner and easier to read controller
1049 code (or View code, if that's where you want to call it).
1051 To illustrate the concept with a fairly simple example, let's create a
1052 method that returns books added in the last 10 minutes. Start by making
1053 a directory where DBIx::Class will look for our ResultSet Class:
1055 $ mkdir lib/MyApp/Schema/ResultSet
1057 Then open C<lib/MyApp/Schema/ResultSet/Book.pm> and enter the following:
1059 package MyApp::Schema::ResultSet::Book;
1063 use base 'DBIx::Class::ResultSet';
1065 =head2 created_after
1067 A predefined search for recently added books
1072 my ($self, $datetime) = @_;
1074 my $date_str = $self->result_source->schema->storage
1075 ->datetime_parser->format_datetime($datetime);
1077 return $self->search({
1078 created => { '>' => $date_str }
1084 Then add the following method to the C<lib/MyApp/Controller/Books.pm>:
1088 List recently created books
1092 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
1093 my ($self, $c, $mins) = @_;
1095 # Retrieve all of the book records as book model objects and store in the
1096 # stash where they can be accessed by the TT template, but only
1097 # retrieve books created within the last $min number of minutes
1098 $c->stash(books => [$c->model('DB::Book')
1099 ->created_after(DateTime->now->subtract(minutes => $mins))]);
1101 # Set the TT template to use. You will almost always want to do this
1102 # in your action methods (action methods respond to user input in
1103 # your controllers).
1104 $c->stash(template => 'books/list.tt2');
1107 Now try different values for the "minutes" argument (the final number
1108 value) using the URL C<http://localhost:3000/books/list_recent/_#_> in
1109 your browser. For example, this would list all books added in the last
1112 http://localhost:3000/books/list_recent/15
1114 Depending on how recently you added books, you might want to try a
1115 higher or lower value for the minutes.
1118 =head2 Chaining ResultSets
1120 One of the most helpful and powerful features in C<DBIx::Class> is that
1121 it allows you to "chain together" a series of queries (note that this
1122 has nothing to do with the "Chained Dispatch" for Catalyst that we were
1123 discussing earlier). Because each ResultSet method returns another
1124 ResultSet, you can take an initial query and immediately feed that into
1125 a second query (and so on for as many queries you need). Note that no
1126 matter how many ResultSets you chain together, the database itself will
1127 not be hit until you use a method that attempts to access the data. And,
1128 because this technique carries over to the ResultSet Class feature we
1129 implemented in the previous section for our "canned search", we can
1130 combine the two capabilities. For example, let's add an action to our
1131 C<Books> controller that lists books that are both recent I<and> have
1132 "TCP" in the title. Open up C<lib/MyApp/Controller/Books.pm> and add
1133 the following method:
1135 =head2 list_recent_tcp
1137 List recently created books
1141 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1142 my ($self, $c, $mins) = @_;
1144 # Retrieve all of the book records as book model objects and store in the
1145 # stash where they can be accessed by the TT template, but only
1146 # retrieve books created within the last $min number of minutes
1147 # AND that have 'TCP' in the title
1148 $c->stash(books => [
1149 $c->model('DB::Book')
1150 ->created_after(DateTime->now->subtract(minutes => $mins))
1151 ->search({title => {'like', '%TCP%'}})
1154 # Set the TT template to use. You will almost always want to do this
1155 # in your action methods (action methods respond to user input in
1156 # your controllers).
1157 $c->stash(template => 'books/list.tt2');
1160 To try this out, enter the following URL into your browser:
1162 http://localhost:3000/books/list_recent_tcp/100
1164 And you should get a list of books added in the last 100 minutes that
1165 contain the string "TCP" in the title. However, if you look at all
1166 books within the last 100 minutes, you should get a longer list (again,
1167 you might have to adjust the number of minutes depending on how recently
1168 you added books to your database):
1170 http://localhost:3000/books/list_recent/100
1172 Take a look at the DBIC_TRACE output in the development server log for
1173 the first URL and you should see something similar to the following:
1175 SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me
1176 WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32'
1178 However, let's not pollute our controller code with this raw "TCP" query
1179 -- it would be cleaner to encapsulate that code in a method on our
1180 ResultSet Class. To do this, open C<lib/MyApp/Schema/ResultSet/Book.pm>
1181 and add the following method:
1185 A predefined search for books with a 'LIKE' search in the string
1190 my ($self, $title_str) = @_;
1192 return $self->search({
1193 title => { 'like' => "%$title_str%" }
1197 We defined the search string as C<$title_str> to make the method more
1198 flexible. Now update the C<list_recent_tcp> method in
1199 C<lib/MyApp/Controller/Books.pm> to match the following (we have
1200 replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line
1201 shown here -- the rest of the method should be the same):
1203 =head2 list_recent_tcp
1205 List recently created books
1209 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1210 my ($self, $c, $mins) = @_;
1212 # Retrieve all of the book records as book model objects and store in the
1213 # stash where they can be accessed by the TT template, but only
1214 # retrieve books created within the last $min number of minutes
1215 # AND that have 'TCP' in the title
1216 $c->stash(books => [
1217 $c->model('DB::Book')
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 Try out the C<list_recent_tcp> and C<list_recent> URLs as we did above.
1229 They should work just the same, but our code is obviously cleaner and
1230 more modular, while also being more flexible at the same time.
1233 =head2 Adding Methods to Result Classes
1235 In the previous two sections we saw a good example of how we could use
1236 DBIx::Class ResultSet Classes to clean up our code for an entire query
1237 (for example, our "canned searches" that filtered the entire query). We
1238 can do a similar improvement when working with individual rows as well.
1239 Whereas the ResultSet construct is used in DBIC to correspond to an
1240 entire query, the Result Class construct is used to represent a row.
1241 Therefore, we can add row-specific "helper methods" to our Result
1242 Classes stored in C<lib/MyApp/Schema/Result/>. For example, open
1243 C<lib/MyApp/Schema/Result/Author.pm> and add the following method (as
1244 always, it must be above the closing "C<1;>"):
1247 # Row-level helper methods
1252 return $self->first_name . ' ' . $self->last_name;
1255 This will allow us to conveniently retrieve both the first and last name
1256 for an author in one shot. Now open C<root/src/books/list.tt2> and
1257 change the definition of C<tt_authors> from this:
1260 [% tt_authors = [ ];
1261 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1267 [% tt_authors = [ ];
1268 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1271 (Only C<author.last_name> was changed to C<author.full_name> -- the rest
1272 of the file should remain the same.)
1274 Now go to the standard book list URL:
1276 http://localhost:3000/books/list
1278 The "Author(s)" column will now contain both the first and last name.
1279 And, because the concatenation logic was encapsulated inside our Result
1280 Class, it keeps the code inside our TT template nice and clean
1281 (remember, we want the templates to be as close to pure HTML markup as
1282 possible). Obviously, this capability becomes even more useful as you
1283 use it to remove even more complicated row-specific logic from your
1287 =head2 Moving Complicated View Code to the Model
1289 The previous section illustrated how we could use a Result Class method
1290 to print the full names of the authors without adding any extra code to
1291 our view, but it still left us with a fairly ugly mess (see
1292 C<root/src/books/list.tt2>):
1296 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1297 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1298 [% # loop in 'side effect notation' to load just the last names of the -%]
1299 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1300 [% # a value, so nothing will be printed here. But, if you have something -%]
1301 [% # in TT that does return a method and you don't want it printed, you -%]
1302 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1303 [% # call it and discard the return value. -%]
1304 [% tt_authors = [ ];
1305 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1306 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1307 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1308 ([% tt_authors.size | html %])
1309 [% # Use another TT vmethod to join & print the names & comma separators -%]
1310 [% tt_authors.join(', ') | html %]
1314 Let's combine some of the techniques used earlier in this section to
1315 clean this up. First, let's add a method to our Book Result Class to
1316 return the number of authors for a book. Open
1317 C<lib/MyApp/Schema/Result/Book.pm> and add the following method:
1321 Return the number of authors for the current book
1328 # Use the 'many_to_many' relationship to fetch all of the authors for the current
1329 # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT
1330 return $self->authors->count;
1333 Next, let's add a method to return a list of authors for a book to the
1334 same C<lib/MyApp/Schema/Result/Book.pm> file:
1338 Return a comma-separated list of authors for the current book
1345 # Loop through all authors for the current book, calling all the 'full_name'
1346 # Result Class method for each
1348 foreach my $author ($self->authors) {
1349 push(@names, $author->full_name);
1352 return join(', ', @names);
1355 This method loops through each author, using the C<full_name> Result
1356 Class method we added to C<lib/MyApp/Schema/Result/Author.pm> in the
1359 Using these two methods, we can simplify our TT code. Open
1360 C<root/src/books/list.tt2> and update the "Author(s)" table cell to
1361 match the following:
1365 [% # Print count and author list using Result Class methods -%]
1366 ([% book.author_count | html %]) [% book.author_list | html %]
1370 Although most of the code we removed comprised comments, the overall
1371 effect is dramatic... because our view code is so simple, we don't need
1372 huge comments to clue people in to the gist of our code. The view code
1373 is now self-documenting and readable enough that you could probably get
1374 by with no comments at all. All of the "complex" work is being done in
1375 our Result Class methods (and, because we have broken the code into
1376 nice, modular chunks, the Result Class code is hardly something you
1377 would call complex).
1379 As we saw in this section, always strive to keep your view AND
1380 controller code as simple as possible by pulling code out into your
1381 model objects. Because L<DBIx::Class> can be easily extended in so many
1382 ways, it's an excellent to way accomplish this objective. It will make
1383 your code cleaner, easier to write, less error-prone, and easier to
1386 Before you conclude this section, hit Refresh in your browser... the
1387 output should be the same even though the backend code has been trimmed
1393 Kennedy Clark, C<hkclark@gmail.com>
1395 Feel free to contact the author for any errors or suggestions, but the
1396 best way to report issues is via the CPAN RT Bug system at
1397 <https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
1399 The most recent version of the Catalyst Tutorial can be found at
1400 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
1402 Copyright 2006-2010, Kennedy Clark, under the
1403 Creative Commons Attribution Share-Alike License Version 3.0
1404 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).