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
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 can be
72 quick and easy. For example, see
73 L<Catalyst::Plugin::AutoCRUD|Catalyst::Plugin::AutoCRUD>,
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::01_Intro|Catalyst::Manual::Tutorial::01_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/"
103 # into @_. The args are separated by the '/' char on the URL.
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::Book')->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. -%]
155 by '[% book.authors.first.last_name %]'
157 [% # Output the rating for the book that was added -%]
158 with a rating of [% book.rating %].</p>
160 [% # Provide a link back to the list page -%]
161 [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%]
162 <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
164 [% # Try out the TT Dumper (for development only!) -%]
166 Dump of the 'book' variable:
167 [% Dumper.dump(book) %]
170 The TT C<USE> directive allows access to a variety of plugin modules
171 (TT plugins, that is, not Catalyst plugins) to add extra functionality
172 to the base TT capabilities. Here, the plugin allows
173 L<Data::Dumper|Data::Dumper> "pretty printing" of objects and
174 variables. Other than that, the rest of the code should be familiar
175 from the examples in Chapter 3.
177 Note: If you are using TT v2.15 you will need to change the code that
178 outputs the "last name for the first author" above to match this:
180 [% authors = book.authors %]
181 by '[% authors.first.last_name IF authors.first;
182 authors.list.first.value.last_name IF ! authors.first %]'
184 to get around an issue in TT v2.15 where blessed hash objects were not
185 handled correctly. But, if you are still using v2.15, it's probably
186 time to upgrade (v2.15 is almost 4 years old). If you are following
187 along in Debian, then you should be on at least v2.20. You can test
188 your version of Template Toolkit with the following:
190 perl -MTemplate -e 'print "$Template::VERSION\n"'
193 =head2 Try the 'url_create' Feature
195 Make sure the development server is running with the "-r" restart
198 $ DBIC_TRACE=1 script/myapp_server.pl -r
200 Note that new path for C</books/url_create> appears in the startup debug
203 Next, use your browser to enter the following URL:
205 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
207 Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by
208 'Stevens' with a rating of 5." along with a dump of the new book model
209 object as it was returned by DBIC. You should also see the following
210 DBIC debug messages displayed in the development server log messages
211 if you have DBIC_TRACE set:
213 INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
214 INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6'
216 The C<INSERT> statements are obviously adding the book and linking it to
217 the existing record for Richard Stevens. The C<SELECT> statement results
218 from DBIC automatically fetching the book for the C<Dumper.dump(book)>.
220 If you then click the "Return to list" link, you should find that
221 there are now six books shown (if necessary, Shift+Reload or
222 Ctrl+Reload your browser at the C</books/list> page). You should now
223 see the six DBIC debug messages similar to the following (where
226 SELECT author.id, author.first_name, author.last_name
227 FROM book_author me JOIN author author
228 ON author.id = me.author_id WHERE ( me.book_id = ? ): 'N'
231 =head1 CONVERT TO A CHAINED ACTION
233 Although the example above uses the same C<Local> action type for the
234 method that we saw in the previous chapter of the tutorial, there is an
235 alternate approach that allows us to be more specific while also
236 paving the way for more advanced capabilities. Change the method
237 declaration for C<url_create> in C<lib/MyApp/Controller/Books.pm> you
238 entered above to match the following:
240 sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
241 # In addition to self & context, get the title, rating, &
242 # author_id args from the URL. Note that Catalyst automatically
243 # puts the first 3 arguments worth of extra information after the
244 # "/<controller_name>/<action_name/" into @_ because we specified
245 # "Args(3)". The args are separated by the '/' char on the URL.
246 my ($self, $c, $title, $rating, $author_id) = @_;
250 This converts the method to take advantage of the Chained
251 action/dispatch type. Chaining lets you have a single URL
252 automatically dispatch to several controller methods, each of which
253 can have precise control over the number of arguments that it will
254 receive. A chain can essentially be thought of having three parts --
255 a beginning, a middle, and an end. The bullets below summarize the key
256 points behind each of these parts of a chain:
270 B<Use "C<:Chained('/')>" to start a chain>
274 Get arguments through C<CaptureArgs()>
278 Specify the path to match with C<PathPart()>
291 Link to previous part of the chain with C<:Chained('_name_')>
295 Get arguments through C<CaptureArgs()>
299 Specify the path to match with C<PathPart()>
312 Link to previous part of the chain with C<:Chained('_name_')>
316 B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain>
320 Specify the path to match with C<PathPart()>
327 In our C<url_create> method above, we have combined all three parts into
328 a single method: C<:Chained('/')> to start the chain,
329 C<:PathPart('books/url_create')> to specify the base URL to match, and
330 C<:Args(3)> to capture exactly three arguments and to end the chain.
332 As we will see shortly, a chain can consist of as many "links" as you
333 wish, with each part capturing some arguments and doing some work
334 along the way. We will continue to use the Chained action type in this
335 chapter of the tutorial and explore slightly more advanced capabilities
336 with the base method and delete feature below. But Chained dispatch
337 is capable of far more. For additional information, see
338 L<Catalyst::Manual::Intro/Action types>,
339 L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>,
340 and the 2006 Advent calendar entry on the subject:
341 L<http://www.catalystframework.org/calendar/2006/10>.
344 =head2 Try the Chained Action
346 If you look back at the development server startup logs from your
347 initial version of the C<url_create> method (the one using the
348 C<:Local> attribute), you will notice that it produced output similar
351 [debug] Loaded Path actions:
352 .-------------------------------------+--------------------------------------.
354 +-------------------------------------+--------------------------------------+
357 | /books | /books/index |
358 | /books/list | /books/list |
359 | /books/url_create | /books/url_create |
360 '-------------------------------------+--------------------------------------'
362 When the development server restarts, the debug output should change
363 to something along the lines of the following:
365 [debug] Loaded Path actions:
366 .-------------------------------------+--------------------------------------.
368 +-------------------------------------+--------------------------------------+
371 | /books | /books/index |
372 | /books/list | /books/list |
373 '-------------------------------------+--------------------------------------'
375 [debug] Loaded Chained actions:
376 .-------------------------------------+--------------------------------------.
377 | Path Spec | Private |
378 +-------------------------------------+--------------------------------------+
379 | /books/url_create/*/*/* | /books/url_create |
380 '-------------------------------------+--------------------------------------'
382 C<url_create> has disappeared form the "Loaded Path actions" section
383 but it now shows up under the newly created "Loaded Chained actions"
384 section. And the "/*/*/*" portion clearly shows our requirement for
387 As with our non-chained version of C<url_create>, use your browser to
388 enter the following URL:
390 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
392 You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
393 'Stevens' with a rating of 5." along with a dump of the new book model
394 object. Click the "Return to list" link, and you should find that there
395 are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>).
398 =head2 Refactor to Use a 'base' Method to Start the Chains
400 Let's make a quick update to our initial Chained action to show a
401 little more of the power of chaining. First, open
402 C<lib/MyApp/Controller/Books.pm> in your editor and add the following
407 Can place common logic to start chained dispatch here
411 sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
414 # Store the ResultSet in stash so it's available for other methods
415 $c->stash->{resultset} = $c->model('DB::Book');
417 # Print a message to the debug log
418 $c->log->debug('*** INSIDE BASE METHOD ***');
421 Here we print a log message and store the DBIC ResultSet in
422 C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available
423 for other actions that chain off C<base>. If your controller always
424 needs a book ID as its first argument, you could have the base method
425 capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
426 book object with C<-E<gt>find($id)> and leave it in the stash for
427 later parts of your chains to then act upon. Because we have several
428 actions that don't need to retrieve a book (such as the C<url_create>
429 we are working with now), we will instead add that functionality
430 to a common C<object> action shortly.
432 As for C<url_create>, let's modify it to first dispatch to C<base>.
433 Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for
434 C<url_create> to match the following:
436 sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
438 Once you save C<lib/MyApp/Controller/Books.pm>, notice that the
439 development server will restart and our "Loaded Chained actions" section
440 will changed slightly:
442 [debug] Loaded Chained actions:
443 .-------------------------------------+--------------------------------------.
444 | Path Spec | Private |
445 +-------------------------------------+--------------------------------------+
446 | /books/url_create/*/*/* | /books/base (0) |
447 | | => /books/url_create |
448 '-------------------------------------+--------------------------------------'
450 The "Path Spec" is the same, but now it maps to two Private actions as
451 we would expect. The C<base> method is being triggered by the
452 C</books> part of the URL. However, the processing then continues to
453 the C<url_create> method because this method "chained" off C<base> and
454 specified C<:PathPart('url_create')> (note that we could have omitted
455 the "PathPart" here because it matches the name of the method, but we
456 will include it to make the logic as explicit as possible).
458 Once again, enter the following URL into your browser:
460 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
462 The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
463 rating of 5." message and a dump of the new book object should appear.
464 Also notice the extra "INSIDE BASE METHOD" debug message in the
465 development server output from the C<base> method. Click the "Return
466 to list" link, and you should find that there are now eight books
467 shown. (You may have a larger number of books if you repeated any of
468 the "create" actions more than once. Don't worry about it as long as
469 the number of books is appropriate for the number of times you added
470 new books... there should be the original five books added via
471 C<myapp01.sql> plus one additional book for each time you ran one
472 of the url_create variations above.)
475 =head1 MANUALLY BUILDING A CREATE FORM
477 Although the C<url_create> action in the previous step does begin to
478 reveal the power and flexibility of both Catalyst and DBIC, it's
479 obviously not a very realistic example of how users should be expected
480 to enter data. This section begins to address that concern.
483 =head2 Add Method to Display The Form
485 Edit C<lib/MyApp/Controller/Books.pm> and add the following method:
489 Display form to collect information for book to create
493 sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
496 # Set the TT template to use
497 $c->stash->{template} = 'books/form_create.tt2';
500 This action simply invokes a view containing a form to create a book.
503 =head2 Add a Template for the Form
505 Open C<root/src/books/form_create.tt2> in your editor and enter:
507 [% META title = 'Manual Form Book Create' -%]
509 <form method="post" action="[% c.uri_for('form_create_do') %]">
511 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
512 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
513 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
515 <input type="submit" name="Submit" value="Submit">
518 Note that we have specified the target of the form data as
519 C<form_create_do>, the method created in the section that follows.
522 =head2 Add a Method to Process Form Values and Update Database
524 Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
525 save the form information to the database:
527 =head2 form_create_do
529 Take information from form and add to database
533 sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
536 # Retrieve the values from the form
537 my $title = $c->request->params->{title} || 'N/A';
538 my $rating = $c->request->params->{rating} || 'N/A';
539 my $author_id = $c->request->params->{author_id} || '1';
542 my $book = $c->model('DB::Book')->create({
546 # Handle relationship with author
547 $book->add_to_book_authors({author_id => $author_id});
548 # Note: Above is a shortcut for this:
549 # $book->create_related('book_authors', {author_id => $author_id});
551 # Store new model object in stash
552 $c->stash->{book} = $book;
554 # Avoid Data::Dumper issue mentioned earlier
555 # You can probably omit this
556 $Data::Dumper::Useperl = 1;
558 # Set the TT template to use
559 $c->stash->{template} = 'books/create_done.tt2';
563 =head2 Test Out The Form
565 Notice that the server startup log reflects the two new chained
566 methods that we added:
568 [debug] Loaded Chained actions:
569 .-------------------------------------+--------------------------------------.
570 | Path Spec | Private |
571 +-------------------------------------+--------------------------------------+
572 | /books/form_create | /books/base (0) |
573 | | => /books/form_create |
574 | /books/form_create_do | /books/base (0) |
575 | | => /books/form_create_do |
576 | /books/url_create/*/*/* | /books/base (0) |
577 | | => /books/url_create |
578 '-------------------------------------+--------------------------------------'
580 Point your browser to L<http://localhost:3000/books/form_create> and
581 enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
582 author ID of 4. You should then see the output of the same
583 C<create_done.tt2> template seen in earlier examples. Finally, click
584 "Return to list" to view the full list of books.
586 B<Note:> Having the user enter the primary key ID for the author is
587 obviously crude; we will address this concern with a drop-down list and
588 add validation to our forms in Chapter 9.
591 =head1 A SIMPLE DELETE FEATURE
593 Turning our attention to the Delete portion of CRUD, this section
594 illustrates some basic techniques that can be used to remove information
598 =head2 Include a Delete Link in the List
600 Edit C<root/src/books/list.tt2> and update it to match the following (two
601 sections have changed: 1) the additional '<th>Links</th>' table header,
602 and 2) the four lines for the Delete link near the bottom):
604 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
605 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
606 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
607 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
609 [% # Provide a title -%]
610 [% META title = 'Book List' -%]
613 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
614 [% # Display each book in a table row %]
615 [% FOREACH book IN books -%]
617 <td>[% book.title %]</td>
618 <td>[% book.rating %]</td>
620 [% # NOTE: See "Exploring The Power of DBIC" for a better way to do this! -%]
621 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
622 [% # loop in 'side effect notation' to load just the last names of the -%]
623 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
624 [% # a value, so nothing will be printed here. But, if you have something -%]
625 [% # in TT that does return a value and you don't want it printed, you can -%]
626 [% # 1) assign it to a bogus value, or -%]
627 [% # 2) use the CALL keyword to call it and discard the return value. -%]
629 tt_authors.push(author.last_name) FOREACH author = book.authors %]
630 [% # Now use a TT 'virtual method' to display the author count in parens -%]
631 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
632 ([% tt_authors.size | html %])
633 [% # Use another TT vmethod to join & print the names & comma separators -%]
634 [% tt_authors.join(', ') | html %]
637 [% # Add a link to delete a book %]
638 <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a>
644 The additional code is obviously designed to add a new column to the
645 right side of the table with a C<Delete> "button" (for simplicity, links
646 will be used instead of full HTML buttons; in practice, anything that
647 modifies data should be handled with a form sending a POST request).
649 Also notice that we are using a more advanced form of C<uri_for> than
650 we have seen before. Here we use
651 C<$c-E<gt>controller-E<gt>action_for> to automatically generate a URI
652 appropriate for that action based on the method we want to link to
653 while inserting the C<book.id> value into the appropriate place. Now,
654 if you ever change C<:PathPart('delete')> in your controller method to
655 C<:PathPart('kill')>, then your links will automatically update
656 without any changes to your .tt2 template file. As long as the name
657 of your method does not change (here, "delete"), then your links will
658 still be correct. There are a few shortcuts and options when using
665 If you are referring to a method in the current controller, you can
666 use C<$self-E<gt>action_for('_method_name_')>.
670 If you are referring to a method in a different controller, you need
671 to include that controller's name as an argument to C<controller()>, as in
672 C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>.
676 B<Note:> In practice you should B<never> use a GET request to delete a
677 record -- always use POST for actions that will modify data. We are
678 doing it here for illustrative and simplicity purposes only.
681 =head2 Add a Common Method to Retrieve a Book for the Chain
683 As mentioned earlier, since we have a mixture of actions that operate
684 on a single book ID and others that do not, we should not have C<base>
685 capture the book ID, find the corresponding book in the database and
686 save it in the stash for later links in the chain. However, just
687 because that logic does not belong in C<base> doesn't mean that we
688 can't create another location to centralize the book lookup code. In
689 our case, we will create a method called C<object> that will store the
690 specific book in the stash. Chains that always operate on a single
691 existing book can chain off this method, but methods such as
692 C<url_create> that don't operate on an existing book can chain
695 To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm>
696 and add the following code:
700 Fetch the specified book object based on the book ID and store
705 sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
706 # $id = primary key of book to delete
707 my ($self, $c, $id) = @_;
709 # Find the book object and store it in the stash
710 $c->stash(object => $c->stash->{resultset}->find($id));
712 # Make sure the lookup was successful. You would probably
713 # want to do something like this in a real app:
714 # $c->detach('/error_404') if !$c->stash->{object};
715 die "Book $id not found!" if !$c->stash->{object};
717 # Print a message to the debug log
718 $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***");
721 Now, any other method that chains off C<object> will automatically
722 have the appropriate book waiting for it in
723 C<$c-E<gt>stash-E<gt>{object}>.
726 =head2 Add a Delete Action to the Controller
728 Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
737 sub delete :Chained('object') :PathPart('delete') :Args(0) {
740 # Use the book object saved by 'object' and delete it along
741 # with related 'book_author' entries
742 $c->stash->{object}->delete;
744 # Set a status message to be displayed at the top of the view
745 $c->stash->{status_msg} = "Book deleted.";
747 # Forward to the list action/method in this controller
751 This method first deletes the book object saved by the C<object> method.
752 However, it also removes the corresponding entry from the
753 C<book_author> table with a cascading delete.
755 Then, rather than forwarding to a "delete done" page as we did with the
756 earlier create example, it simply sets the C<status_msg> to display a
757 notification to the user as the normal list view is rendered.
759 The C<delete> action uses the context C<forward> method to return the
760 user to the book list. The C<detach> method could have also been used.
761 Whereas C<forward> I<returns> to the original action once it is
762 completed, C<detach> does I<not> return. Other than that, the two are
766 =head2 Try the Delete Feature
768 One you save the Books controller, the server should automatically restart.
769 The C<delete> method should now appear in the "Loaded Chained actions" section
770 of the startup debug output:
772 [debug] Loaded Chained actions:
773 .-------------------------------------+--------------------------------------.
774 | Path Spec | Private |
775 +-------------------------------------+--------------------------------------+
776 | /books/id/*/delete | /books/base (0) |
777 | | -> /books/object (1) |
778 | | => /books/delete |
779 | /books/form_create | /books/base (0) |
780 | | => /books/form_create |
781 | /books/form_create_do | /books/base (0) |
782 | | => /books/form_create_do |
783 | /books/url_create/*/*/* | /books/base (0) |
784 | | => /books/url_create |
785 '-------------------------------------+--------------------------------------'
787 Then point your browser to L<http://localhost:3000/books/list> and click
788 the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green
789 "Book deleted" status message should display at the top of the page,
790 along with a list of the eight remaining books. You will also see the
791 cascading delete operation via the DBIC_TRACE output:
793 SELECT me.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6'
794 DELETE FROM book WHERE ( id = ? ): '6'
795 SELECT me.book_id, me.author_id FROM book_author me WHERE ( me.book_id = ? ): '6'
796 DELETE FROM book_author WHERE ( author_id = ? AND book_id = ? ): '4', '6'
799 =head2 Fixing a Dangerous URL
801 Note the URL in your browser once you have performed the deletion in the
802 prior step -- it is still referencing the delete action:
804 http://localhost:3000/books/id/6/delete
806 What if the user were to press reload with this URL still active? In
807 this case the redundant delete is harmless (although it does generate
808 an exception screen, it doesn't perform any undesirable actions on the
809 application or database), but in other cases this could clearly be
812 We can improve the logic by converting to a redirect. Unlike
813 C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform
814 a server-side alteration in the flow of processing, a redirect is a
815 client-side mechanism that causes the browser to issue an entirely
816 new request. As a result, the URL in the browser is updated to match
817 the destination of the redirection URL.
819 To convert the forward used in the previous section to a redirect,
820 open C<lib/MyApp/Controller/Books.pm> and edit the existing
821 C<sub delete> method to match:
829 sub delete :Chained('object') :PathPart('delete') :Args(0) {
832 # Use the book object saved by 'object' and delete it along
833 # with related 'book_author' entries
834 $c->stash->{object}->delete;
836 # Set a status message to be displayed at the top of the view
837 $c->stash->{status_msg} = "Book deleted.";
839 # Redirect the user back to the list page. Note the use
840 # of $self->action_for as earlier in this section (BasicCRUD)
841 $c->response->redirect($c->uri_for($self->action_for('list')));
845 =head2 Try the Delete and Redirect Logic
847 Point your browser to L<http://localhost:3000/books/list> (don't just
848 hit "Refresh" in your browser since we left the URL in an invalid state
849 in the previous section!) and delete the first copy of the remaining two
850 "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return
851 to the L<http://localhost:3000/books/list> URL, so that is an
852 improvement, but notice that I<no green "Book deleted" status message is
853 displayed>. Because the stash is reset on every request (and a redirect
854 involves a second request), the C<status_msg> is cleared before it can
858 =head2 Using 'uri_for' to Pass Query Parameters
860 There are several ways to pass information across a redirect. One
861 option is to use the C<flash> technique that we will see in Chapter 5
862 of this tutorial; however, here we will pass the information via query
863 parameters on the redirect itself. Open
864 C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete>
865 method to match the following:
873 sub delete :Chained('object') :PathPart('delete') :Args(0) {
876 # Use the book object saved by 'object' and delete it along
877 # with related 'book_author' entries
878 $c->stash->{object}->delete;
880 # Redirect the user back to the list page with status msg as an arg
881 $c->response->redirect($c->uri_for($self->action_for('list'),
882 {status_msg => "Book deleted."}));
885 This modification simply leverages the ability of C<uri_for> to include
886 an arbitrary number of name/value pairs in a hash reference. Next, we
887 need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a
892 [%# Status and error messages %]
893 <span class="message">[% status_msg || c.request.params.status_msg %]</span>
894 <span class="error">[% error_msg %]</span>
895 [%# This is where TT will stick all of your template's contents. -%]
897 </div><!-- end content -->
900 Although the sample above only shows the C<content> div, leave the
901 rest of the file intact -- the only change we made to the C<wrapper.tt2>
902 was to add "C<|| c.request.params.status_msg>" to the
903 C<E<lt>span class="message"E<gt>> line.
906 =head2 Try the Delete and Redirect With Query Param Logic
908 Point your browser to L<http://localhost:3000/books/list> (you should
909 now be able to safely hit "refresh" in your browser). Then delete the
910 remaining copy of "TCPIP_Illustrated_Vol-2". The green "Book deleted"
911 status message should return.
913 B<NOTE:> Another popular method for maintaining server-side
914 information across a redirect is to use the C<flash> technique we
915 discuss in the next chapter of the tutorial,
916 L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>. While
917 C<flash> is a "slicker" mechanism in that it's all handled by the
918 server and doesn't "pollute" your URLs, B<it is important to note that
919 C<flash> can lead to situations where the wrong information shows up
920 in the wrong browser window if the user has multiple windows or
921 browser tabs open>. For example, Window A causes something to be
922 placed in the stash, but before that window performs a redirect,
923 Window B makes a request to the server and gets the status information
924 that should really go to Window A. For this reason, you may wish
925 to use the "query param" technique shown here in your applications.
928 =head1 EXPLORING THE POWER OF DBIC
930 In this section we will explore some additional capabilities offered
931 by DBIx::Class. Although these features have relatively little to do
932 with Catalyst per se, you will almost certainly want to take advantage
933 of them in your applications.
936 =head2 Add Datetime Columns to Our Existing Books Table
938 Let's add two columns to our existing C<books> table to track when
939 each book was added and when each book is updated:
942 sqlite> ALTER TABLE book ADD created INTEGER;
943 sqlite> ALTER TABLE book ADD updated INTEGER;
944 sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
945 sqlite> SELECT * FROM book;
946 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
947 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
948 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
949 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
950 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
951 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
955 This will modify the C<books> table to include the two new fields
956 and populate those fields with the current time.
959 =head2 Update DBIx::Class to Automatically Handle the Datetime Columns
961 Next, we should re-run the DBIC helper to update the Result Classes
964 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
965 create=static components=TimeStamp dbi:SQLite:myapp.db \
966 on_connect_do="PRAGMA foreign_keys = ON"
967 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
968 exists "/root/dev/MyApp/script/../t"
969 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
970 Schema dump completed.
971 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
973 Notice that we modified our use of the helper slightly: we told
974 it to include the L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp>
975 in the C<load_components> line of the Result Classes.
977 If you open C<lib/MyApp/Schema/Result/Book.pm> in your editor you should
978 see that the C<created> and C<updated> fields are now included in the
979 call to C<add_columns()>. However, also notice that the C<many_to_many>
980 relationships we manually added below the "C<# DO NOT MODIFY...>" line
981 were automatically preserved.
983 While we have this file open, let's update it with some additional
984 information to have DBIC automatically handle the updating of these
985 two fields for us. Insert the following code at the bottom of the
986 file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and
987 B<above> the C<1;> on the last line):
990 # Enable automatic date handling
992 __PACKAGE__->add_columns(
994 { data_type => 'datetime', set_on_create => 1 },
996 { data_type => 'datetime', set_on_create => 1, set_on_update => 1 },
999 This will override the definition for these fields that Schema::Loader
1000 placed at the top of the file. The C<set_on_create> and
1001 C<set_on_update> options will cause DBIx::Class to automatically
1002 update the timestamps in these columns whenever a row is created or
1005 Then enter the following URL into your web browser:
1007 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
1009 You should get the same "Book Created" screen we saw above. However,
1010 if you now use the sqlite3 command-line tool to dump the C<books> table,
1011 you will see that the new book we added has an appropriate date and
1012 time entered for it (see the last line in the listing below):
1014 $ sqlite3 myapp.db "select * from book"
1015 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1016 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1017 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
1018 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1019 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1020 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1021 10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42
1023 Notice in the debug log that the SQL DBIC generated has changed to
1024 incorporate the datetime logic:
1026 INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ):
1027 '2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42'
1028 INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10'
1031 =head2 Create a ResultSet Class
1033 An often overlooked but extremely powerful features of DBIC is that it
1034 allows you to supply your own subclasses of C<DBIx::Class::ResultSet>.
1035 It allows you to pull complex and unsightly "query code" out of your
1036 controllers and encapsulate it in a method of your ResultSet Class.
1037 These "canned queries" in your ResultSet Class can then be invoked
1038 via a single call, resulting in much cleaner and easier to read
1041 To illustrate the concept with a fairly simple example, let's create a
1042 method that returns books added in the last 10 minutes. Start by
1043 making a directory where DBIx::Class will look for our ResultSet Class:
1045 $ mkdir lib/MyApp/Schema/ResultSet
1047 Then open C<lib/MyApp/Schema/ResultSet/Book.pm> and enter the following:
1049 package MyApp::Schema::ResultSet::Book;
1053 use base 'DBIx::Class::ResultSet';
1055 =head2 created_after
1057 A predefined search for recently added books
1062 my ($self, $datetime) = @_;
1064 my $date_str = $self->result_source->schema->storage
1065 ->datetime_parser->format_datetime($datetime);
1067 return $self->search({
1068 created => { '>' => $date_str }
1074 Then add the following method to the C<lib/MyApp/Controller/Books.pm>:
1078 List recently created books
1082 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
1083 my ($self, $c, $mins) = @_;
1085 # Retrieve all of the book records as book model objects and store in the
1086 # stash where they can be accessed by the TT template, but only
1087 # retrieve books created within the last $min number of minutes
1088 $c->stash->{books} = [$c->model('DB::Book')
1089 ->created_after(DateTime->now->subtract(minutes => $mins))];
1091 # Set the TT template to use. You will almost always want to do this
1092 # in your action methods (action methods respond to user input in
1093 # your controllers).
1094 $c->stash->{template} = 'books/list.tt2';
1097 Now try different values for the "minutes" argument (the final number
1098 value) using the URL C<http://localhost:3000/books/list_recent/_#_> in
1099 your browser. For example, this would list all books added in the last
1102 http://localhost:3000/books/list_recent/15
1104 Depending on how recently you added books, you might want to
1105 try a higher or lower value.
1108 =head2 Chaining ResultSets
1110 One of the most helpful and powerful features in DBIx::Class is that
1111 it allows you to "chain together" a series of queries (note that this
1112 has nothing to do with the "Chained Dispatch" for Catalyst that we
1113 were discussing above). Because each ResultSet returns another
1114 ResultSet, you can take an initial query and immediately feed that
1115 into a second query (and so on for as many queries you need). Note
1116 that no matter how many ResultSets you chain together, the database
1117 itself will not be hit until you use a method that attempts to access
1118 the data. And, because this technique carries over to the ResultSet
1119 Class feature we implemented in the previous section for our "canned
1120 search", we can combine the two capabilities. For example, let's add
1121 an action to our C<Books> controller that lists books that are both
1122 recent I<and> have "TCP" in the title. Open up
1123 C<lib/MyApp/Controller/Books.pm> and add the following method:
1125 =head2 list_recent_tcp
1127 List recently created books
1131 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1132 my ($self, $c, $mins) = @_;
1134 # Retrieve all of the book records as book model objects and store in the
1135 # stash where they can be accessed by the TT template, but only
1136 # retrieve books created within the last $min number of minutes
1137 # AND that have 'TCP' in the title
1138 $c->stash->{books} = [$c->model('DB::Book')
1139 ->created_after(DateTime->now->subtract(minutes => $mins))
1140 ->search({title => {'like', '%TCP%'}})
1143 # Set the TT template to use. You will almost always want to do this
1144 # in your action methods (action methods respond to user input in
1145 # your controllers).
1146 $c->stash->{template} = 'books/list.tt2';
1149 To try this out, enter the following URL into your browser:
1151 http://localhost:3000/books/list_recent_tcp/100
1153 And you should get a list of books added in the last 100 minutes that
1154 contain the string "TCP" in the title. However, if you look at all
1155 books within the last 100 minutes, you should get a longer list
1156 (again, you might have to adjust the number of minutes depending on
1157 how recently you added books to your database):
1159 http://localhost:3000/books/list_recent/100
1161 Take a look at the DBIC_TRACE output in the development server log for
1162 the first URL and you should see something similar to the following:
1164 SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me
1165 WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32'
1167 However, let's not pollute our controller code with this raw "TCP"
1168 query -- it would be cleaner to encapsulate that code in a method on
1169 our ResultSet Class. To do this, open
1170 C<lib/MyApp/Schema/ResultSet/Book.pm> and add the following method:
1174 A predefined search for books with a 'LIKE' search in the string
1179 my ($self, $title_str) = @_;
1181 return $self->search({
1182 title => { 'like' => "%$title_str%" }
1186 We defined the search string as C<$title_str> to make the method more
1187 flexible. Now update the C<list_recent_tcp> method in
1188 C<lib/MyApp/Controller/Books.pm> to match the following (we have
1189 replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line
1190 shown here -- the rest of the method should be the same):
1192 =head2 list_recent_tcp
1194 List recently created books
1198 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1199 my ($self, $c, $mins) = @_;
1201 # Retrieve all of the book records as book model objects and store in the
1202 # stash where they can be accessed by the TT template, but only
1203 # retrieve books created within the last $min number of minutes
1204 # AND that have 'TCP' in the title
1205 $c->stash->{books} = [$c->model('DB::Book')
1206 ->created_after(DateTime->now->subtract(minutes => $mins))
1210 # Set the TT template to use. You will almost always want to do this
1211 # in your action methods (action methods respond to user input in
1212 # your controllers).
1213 $c->stash->{template} = 'books/list.tt2';
1216 Try out the C<list_recent_tcp> and C<list_recent> URLs as we did above.
1217 They should work just the same, but our code is obviously cleaner and
1218 more modular, while also being more flexible at the same time.
1221 =head2 Adding Methods to Result Classes
1223 In the previous two sections we saw a good example of how we could use
1224 DBIx::Class ResultSet Classes to clean up our code for an entire query
1225 (for example, our "canned searches" that filtered the entire query).
1226 We can do a similar improvement when working with individual rows as
1227 well. Whereas the ResultSet construct is used in DBIC to correspond
1228 to an entire query, the Result Class construct is used to represent a
1229 row. Therefore, we can add row-specific "helper methods" to our Result
1230 Classes stored in C<lib/MyApp/Schema/Result/>. For example, open
1231 C<lib/MyApp/Schema/Result/Author.pm> and add the following method (as
1232 always, it must be above the closing "C<1;>"):
1240 return $self->first_name . ' ' . $self->last_name;
1243 This will allow us to conveniently retrieve both the first and last
1244 name for an author in one shot. Now open C<root/src/books/list.tt2>
1245 and change the definition of C<tt_authors> from this:
1248 [% tt_authors = [ ];
1249 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1255 [% tt_authors = [ ];
1256 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1259 (Only C<author.last_name> was changed to C<author.full_name> -- the
1260 rest of the file should remain the same.)
1262 Now go to the standard book list URL:
1264 http://localhost:3000/books/list
1266 The "Author(s)" column will now contain both the first and last name.
1267 And, because the concatenation logic was encapsulated inside our
1268 Result Class, it keeps the code inside our TT template nice and clean
1269 (remember, we want the templates to be as close to pure HTML markup as
1270 possible). Obviously, this capability becomes even more useful as you
1271 use to to remove even more complicated row-specific logic from your
1275 =head2 Moving Complicated View Code to the Model
1277 The previous section illustrated how we could use a Result Class
1278 method to print the full names of the authors without adding any extra
1279 code to our view, but it still left us with a fairly ugly mess (see
1280 C<root/src/books/list.tt2>):
1284 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1285 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1286 [% # loop in 'side effect notation' to load just the last names of the -%]
1287 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1288 [% # a value, so nothing will be printed here. But, if you have something -%]
1289 [% # in TT that does return a method and you don't want it printed, you -%]
1290 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1291 [% # call it and discard the return value. -%]
1292 [% tt_authors = [ ];
1293 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1294 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1295 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1296 ([% tt_authors.size | html %])
1297 [% # Use another TT vmethod to join & print the names & comma separators -%]
1298 [% tt_authors.join(', ') | html %]
1302 Let's combine some of the techniques used earlier in this section to
1303 clean this up. First, let's add a method to our Book Result Class to
1304 return the number of authors for a book. Open
1305 C<lib/MyApp/Schema/Result/Book.pm> and add the following method:
1309 Return the number of authors for the current book
1316 # Use the 'many_to_many' relationship to fetch all of the authors for the current
1317 # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT
1318 return $self->authors->count;
1321 Next, let's add a method to return a list of authors for a book to the
1322 same C<lib/MyApp/Schema/Result/Book.pm> file:
1326 Return a comma-separated list of authors for the current book
1333 # Loop through all authors for the current book, calling all the 'full_name'
1334 # Result Class method for each
1336 foreach my $author ($self->authors) {
1337 push(@names, $author->full_name);
1340 return join(', ', @names);
1343 This method loops through each author, using the C<full_name> Result
1344 Class method we added to C<lib/MyApp/Schema/Result/Author.pm> in the
1347 Using these two methods, we can simplify our TT code. Open
1348 C<root/src/books/list.tt2> and update the "Author(s)" table cell to
1349 match the following:
1353 [% # Print count and author list using Result Class methods -%]
1354 ([% book.author_count | html %]) [% book.author_list | html %]
1358 Although most of the code we removed comprised comments, the overall
1359 effect is dramatic... because our view code is so simple, we don't need
1360 huge comments to clue people in to the gist of our code. The view code
1361 is now self-documenting and readable enough that you could probably get
1362 by with no comments at all. All of the "complex" work is being done in
1363 our Result Class methods (and, because we have broken the code into
1364 nice, modular chucks, the Result Class code is hardly something you
1365 would call complex).
1367 As we saw in this section, always strive to keep your view AND
1368 controller code as simple as possible by pulling code out into your
1369 model objects. Because DBIx::Class can be easily extended in so many
1370 ways, it's an excellent to way accomplish this objective. It will
1371 make your code cleaner, easier to write, less error-prone, and easier
1372 to debug and maintain.
1374 Before you conclude this section, hit Refresh in your browser... the
1375 output should be the same even though the backend code has been trimmed
1381 Kennedy Clark, C<hkclark@gmail.com>
1383 Please report any errors, issues or suggestions to the author. The
1384 most recent version of the Catalyst Tutorial can be found at
1385 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
1387 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1388 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).