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 Now start the development server with our basic chained method in
363 place and the startup debug output should change to something along
364 the lines of the following:
366 [debug] Loaded Path actions:
367 .-------------------------------------+--------------------------------------.
369 +-------------------------------------+--------------------------------------+
372 | /books | /books/index |
373 | /books/list | /books/list |
374 '-------------------------------------+--------------------------------------'
376 [debug] Loaded Chained actions:
377 .-------------------------------------+--------------------------------------.
378 | Path Spec | Private |
379 +-------------------------------------+--------------------------------------+
380 | /books/url_create/*/*/* | /books/url_create |
381 '-------------------------------------+--------------------------------------'
383 C<url_create> has disappeared form the "Loaded Path actions" section
384 but it now shows up under the newly created "Loaded Chained actions"
385 section. And the "/*/*/*" portion clearly shows our requirement for
388 As with our non-chained version of C<url_create>, use your browser to
389 enter the following URL:
391 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
393 You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
394 'Stevens' with a rating of 5." along with a dump of the new book model
395 object. Click the "Return to list" link, and you should find that there
396 are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>).
399 =head2 Refactor to Use a 'base' Method to Start the Chains
401 Let's make a quick update to our initial Chained action to show a
402 little more of the power of chaining. First, open
403 C<lib/MyApp/Controller/Books.pm> in your editor and add the following
408 Can place common logic to start chained dispatch here
412 sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
415 # Store the ResultSet in stash so it's available for other methods
416 $c->stash->{resultset} = $c->model('DB::Book');
418 # Print a message to the debug log
419 $c->log->debug('*** INSIDE BASE METHOD ***');
422 Here we print a log message and store the DBIC ResultSet in
423 C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available
424 for other actions that chain off C<base>. If your controller always
425 needs a book ID as its first argument, you could have the base method
426 capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
427 book object with C<-E<gt>find($id)> and leave it in the stash for
428 later parts of your chains to then act upon. Because we have several
429 actions that don't need to retrieve a book (such as the C<url_create>
430 we are working with now), we will instead add that functionality
431 to a common C<object> action shortly.
433 As for C<url_create>, let's modify it to first dispatch to C<base>.
434 Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for
435 C<url_create> to match the following:
437 sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
439 Once you save C<lib/MyApp/Controller/Books.pm>, notice that the
440 development server will restart and our "Loaded Chained actions" section
441 will changed slightly:
443 [debug] Loaded Chained actions:
444 .-------------------------------------+--------------------------------------.
445 | Path Spec | Private |
446 +-------------------------------------+--------------------------------------+
447 | /books/url_create/*/*/* | /books/base (0) |
448 | | => /books/url_create |
449 '-------------------------------------+--------------------------------------'
451 The "Path Spec" is the same, but now it maps to two Private actions as
452 we would expect. The C<base> method is being triggered by the
453 C</books> part of the URL. However, the processing then continues to
454 the C<url_create> method because this method "chained" off C<base> and
455 specified C<:PathPart('url_create')> (note that we could have omitted
456 the "PathPart" here because it matches the name of the method, but we
457 will include it to make the logic as explicit as possible).
459 Once again, enter the following URL into your browser:
461 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
463 The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
464 rating of 5." message and a dump of the new book object should appear.
465 Also notice the extra "INSIDE BASE METHOD" debug message in the
466 development server output from the C<base> method. Click the "Return
467 to list" link, and you should find that there are now eight books
468 shown. (You may have a larger number of books if you repeated any of
469 the "create" actions more than once. Don't worry about it as long as
470 the number of books is appropriate for the number of times you added
471 new books... there should be the original five books added via
472 C<myapp01.sql> plus one additional book for each time you ran one
473 of the url_create variations above.)
476 =head1 MANUALLY BUILDING A CREATE FORM
478 Although the C<url_create> action in the previous step does begin to
479 reveal the power and flexibility of both Catalyst and DBIC, it's
480 obviously not a very realistic example of how users should be expected
481 to enter data. This section begins to address that concern.
484 =head2 Add Method to Display The Form
486 Edit C<lib/MyApp/Controller/Books.pm> and add the following method:
490 Display form to collect information for book to create
494 sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
497 # Set the TT template to use
498 $c->stash->{template} = 'books/form_create.tt2';
501 This action simply invokes a view containing a form to create a book.
504 =head2 Add a Template for the Form
506 Open C<root/src/books/form_create.tt2> in your editor and enter:
508 [% META title = 'Manual Form Book Create' -%]
510 <form method="post" action="[% c.uri_for('form_create_do') %]">
512 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
513 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
514 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
516 <input type="submit" name="Submit" value="Submit">
519 Note that we have specified the target of the form data as
520 C<form_create_do>, the method created in the section that follows.
523 =head2 Add a Method to Process Form Values and Update Database
525 Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
526 save the form information to the database:
528 =head2 form_create_do
530 Take information from form and add to database
534 sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
537 # Retrieve the values from the form
538 my $title = $c->request->params->{title} || 'N/A';
539 my $rating = $c->request->params->{rating} || 'N/A';
540 my $author_id = $c->request->params->{author_id} || '1';
543 my $book = $c->model('DB::Book')->create({
547 # Handle relationship with author
548 $book->add_to_book_authors({author_id => $author_id});
549 # Note: Above is a shortcut for this:
550 # $book->create_related('book_authors', {author_id => $author_id});
552 # Store new model object in stash
553 $c->stash->{book} = $book;
555 # Avoid Data::Dumper issue mentioned earlier
556 # You can probably omit this
557 $Data::Dumper::Useperl = 1;
559 # Set the TT template to use
560 $c->stash->{template} = 'books/create_done.tt2';
564 =head2 Test Out The Form
566 Notice that the server startup log reflects the two new chained
567 methods that we added:
569 [debug] Loaded Chained actions:
570 .-------------------------------------+--------------------------------------.
571 | Path Spec | Private |
572 +-------------------------------------+--------------------------------------+
573 | /books/form_create | /books/base (0) |
574 | | => /books/form_create |
575 | /books/form_create_do | /books/base (0) |
576 | | => /books/form_create_do |
577 | /books/url_create/*/*/* | /books/base (0) |
578 | | => /books/url_create |
579 '-------------------------------------+--------------------------------------'
581 Point your browser to L<http://localhost:3000/books/form_create> and
582 enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
583 author ID of 4. You should then see the output of the same
584 C<create_done.tt2> template seen in earlier examples. Finally, click
585 "Return to list" to view the full list of books.
587 B<Note:> Having the user enter the primary key ID for the author is
588 obviously crude; we will address this concern with a drop-down list and
589 add validation to our forms in Chapter 9.
592 =head1 A SIMPLE DELETE FEATURE
594 Turning our attention to the Delete portion of CRUD, this section
595 illustrates some basic techniques that can be used to remove information
599 =head2 Include a Delete Link in the List
601 Edit C<root/src/books/list.tt2> and update it to match the following (two
602 sections have changed: 1) the additional '<th>Links</th>' table header,
603 and 2) the four lines for the Delete link near the bottom):
605 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
606 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
607 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
608 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
610 [% # Provide a title -%]
611 [% META title = 'Book List' -%]
614 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
615 [% # Display each book in a table row %]
616 [% FOREACH book IN books -%]
618 <td>[% book.title %]</td>
619 <td>[% book.rating %]</td>
621 [% # NOTE: See "Exploring The Power of DBIC" for a better way to do this! -%]
622 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
623 [% # loop in 'side effect notation' to load just the last names of the -%]
624 [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%]
625 [% # a value, so nothing will be printed here. But, if you have something -%]
626 [% # in TT that does return a value and you don't want it printed, you can -%]
627 [% # 1) assign it to a bogus value, or -%]
628 [% # 2) use the CALL keyword to call it and discard the return value. -%]
630 tt_authors.push(author.last_name) FOREACH author = book.authors %]
631 [% # Now use a TT 'virtual method' to display the author count in parens -%]
632 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
633 ([% tt_authors.size | html %])
634 [% # Use another TT vmethod to join & print the names & comma separators -%]
635 [% tt_authors.join(', ') | html %]
638 [% # Add a link to delete a book %]
639 <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a>
645 The additional code is obviously designed to add a new column to the
646 right side of the table with a C<Delete> "button" (for simplicity, links
647 will be used instead of full HTML buttons; in practice, anything that
648 modifies data should be handled with a form sending a POST request).
650 Also notice that we are using a more advanced form of C<uri_for> than
651 we have seen before. Here we use
652 C<$c-E<gt>controller-E<gt>action_for> to automatically generate a URI
653 appropriate for that action based on the method we want to link to
654 while inserting the C<book.id> value into the appropriate place. Now,
655 if you ever change C<:PathPart('delete')> in your controller method to
656 C<:PathPart('kill')>, then your links will automatically update
657 without any changes to your .tt2 template file. As long as the name
658 of your method does not change (here, "delete"), then your links will
659 still be correct. There are a few shortcuts and options when using
666 If you are referring to a method in the current controller, you can
667 use C<$self-E<gt>action_for('_method_name_')>.
671 If you are referring to a method in a different controller, you need
672 to include that controller's name as an argument to C<controller()>, as in
673 C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>.
677 B<Note:> In practice you should B<never> use a GET request to delete a
678 record -- always use POST for actions that will modify data. We are
679 doing it here for illustrative and simplicity purposes only.
682 =head2 Add a Common Method to Retrieve a Book for the Chain
684 As mentioned earlier, since we have a mixture of actions that operate
685 on a single book ID and others that do not, we should not have C<base>
686 capture the book ID, find the corresponding book in the database and
687 save it in the stash for later links in the chain. However, just
688 because that logic does not belong in C<base> doesn't mean that we
689 can't create another location to centralize the book lookup code. In
690 our case, we will create a method called C<object> that will store the
691 specific book in the stash. Chains that always operate on a single
692 existing book can chain off this method, but methods such as
693 C<url_create> that don't operate on an existing book can chain
696 To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm>
697 and add the following code:
701 Fetch the specified book object based on the book ID and store
706 sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
707 # $id = primary key of book to delete
708 my ($self, $c, $id) = @_;
710 # Find the book object and store it in the stash
711 $c->stash(object => $c->stash->{resultset}->find($id));
713 # Make sure the lookup was successful. You would probably
714 # want to do something like this in a real app:
715 # $c->detach('/error_404') if !$c->stash->{object};
716 die "Book $id not found!" if !$c->stash->{object};
718 # Print a message to the debug log
719 $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***");
722 Now, any other method that chains off C<object> will automatically
723 have the appropriate book waiting for it in
724 C<$c-E<gt>stash-E<gt>{object}>.
727 =head2 Add a Delete Action to the Controller
729 Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
738 sub delete :Chained('object') :PathPart('delete') :Args(0) {
741 # Use the book object saved by 'object' and delete it along
742 # with related 'book_author' entries
743 $c->stash->{object}->delete;
745 # Set a status message to be displayed at the top of the view
746 $c->stash->{status_msg} = "Book deleted.";
748 # Forward to the list action/method in this controller
752 This method first deletes the book object saved by the C<object> method.
753 However, it also removes the corresponding entry from the
754 C<book_author> table with a cascading delete.
756 Then, rather than forwarding to a "delete done" page as we did with the
757 earlier create example, it simply sets the C<status_msg> to display a
758 notification to the user as the normal list view is rendered.
760 The C<delete> action uses the context C<forward> method to return the
761 user to the book list. The C<detach> method could have also been used.
762 Whereas C<forward> I<returns> to the original action once it is
763 completed, C<detach> does I<not> return. Other than that, the two are
767 =head2 Try the Delete Feature
769 One you save the Books controller, the server should automatically restart.
770 The C<delete> method should now appear in the "Loaded Chained actions" section
771 of the startup debug output:
773 [debug] Loaded Chained actions:
774 .-------------------------------------+--------------------------------------.
775 | Path Spec | Private |
776 +-------------------------------------+--------------------------------------+
777 | /books/id/*/delete | /books/base (0) |
778 | | -> /books/object (1) |
779 | | => /books/delete |
780 | /books/form_create | /books/base (0) |
781 | | => /books/form_create |
782 | /books/form_create_do | /books/base (0) |
783 | | => /books/form_create_do |
784 | /books/url_create/*/*/* | /books/base (0) |
785 | | => /books/url_create |
786 '-------------------------------------+--------------------------------------'
788 Then point your browser to L<http://localhost:3000/books/list> and click
789 the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green
790 "Book deleted" status message should display at the top of the page,
791 along with a list of the eight remaining books. You will also see the
792 cascading delete operation via the DBIC_TRACE output:
794 SELECT me.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6'
795 DELETE FROM book WHERE ( id = ? ): '6'
796 SELECT me.book_id, me.author_id FROM book_author me WHERE ( me.book_id = ? ): '6'
797 DELETE FROM book_author WHERE ( author_id = ? AND book_id = ? ): '4', '6'
800 =head2 Fixing a Dangerous URL
802 Note the URL in your browser once you have performed the deletion in the
803 prior step -- it is still referencing the delete action:
805 http://localhost:3000/books/id/6/delete
807 What if the user were to press reload with this URL still active? In
808 this case the redundant delete is harmless (although it does generate
809 an exception screen, it doesn't perform any undesirable actions on the
810 application or database), but in other cases this could clearly be
813 We can improve the logic by converting to a redirect. Unlike
814 C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform
815 a server-side alteration in the flow of processing, a redirect is a
816 client-side mechanism that causes the browser to issue an entirely
817 new request. As a result, the URL in the browser is updated to match
818 the destination of the redirection URL.
820 To convert the forward used in the previous section to a redirect,
821 open C<lib/MyApp/Controller/Books.pm> and edit the existing
822 C<sub delete> method to match:
830 sub delete :Chained('object') :PathPart('delete') :Args(0) {
833 # Use the book object saved by 'object' and delete it along
834 # with related 'book_author' entries
835 $c->stash->{object}->delete;
837 # Set a status message to be displayed at the top of the view
838 $c->stash->{status_msg} = "Book deleted.";
840 # Redirect the user back to the list page. Note the use
841 # of $self->action_for as earlier in this section (BasicCRUD)
842 $c->response->redirect($c->uri_for($self->action_for('list')));
846 =head2 Try the Delete and Redirect Logic
848 Point your browser to L<http://localhost:3000/books/list> (don't just
849 hit "Refresh" in your browser since we left the URL in an invalid state
850 in the previous section!) and delete the first copy of the remaining two
851 "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return
852 to the L<http://localhost:3000/books/list> URL, so that is an
853 improvement, but notice that I<no green "Book deleted" status message is
854 displayed>. Because the stash is reset on every request (and a redirect
855 involves a second request), the C<status_msg> is cleared before it can
859 =head2 Using 'uri_for' to Pass Query Parameters
861 There are several ways to pass information across a redirect. One
862 option is to use the C<flash> technique that we will see in Chapter 5
863 of this tutorial; however, here we will pass the information via query
864 parameters on the redirect itself. Open
865 C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete>
866 method to match the following:
874 sub delete :Chained('object') :PathPart('delete') :Args(0) {
877 # Use the book object saved by 'object' and delete it along
878 # with related 'book_author' entries
879 $c->stash->{object}->delete;
881 # Redirect the user back to the list page with status msg as an arg
882 $c->response->redirect($c->uri_for($self->action_for('list'),
883 {status_msg => "Book deleted."}));
886 This modification simply leverages the ability of C<uri_for> to include
887 an arbitrary number of name/value pairs in a hash reference. Next, we
888 need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a
893 [%# Status and error messages %]
894 <span class="message">[% status_msg || c.request.params.status_msg %]</span>
895 <span class="error">[% error_msg %]</span>
896 [%# This is where TT will stick all of your template's contents. -%]
898 </div><!-- end content -->
901 Although the sample above only shows the C<content> div, leave the
902 rest of the file intact -- the only change we made to the C<wrapper.tt2>
903 was to add "C<|| c.request.params.status_msg>" to the
904 C<E<lt>span class="message"E<gt>> line.
907 =head2 Try the Delete and Redirect With Query Param Logic
909 Point your browser to L<http://localhost:3000/books/list> (you should
910 now be able to safely hit "refresh" in your browser). Then delete the
911 remaining copy of "TCPIP_Illustrated_Vol-2". The green "Book deleted"
912 status message should return.
914 B<NOTE:> Another popular method for maintaining server-side
915 information across a redirect is to use the C<flash> technique we
916 discuss in the next chapter of the tutorial,
917 L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>. While
918 C<flash> is a "slicker" mechanism in that it's all handled by the
919 server and doesn't "pollute" your URLs, B<it is important to note that
920 C<flash> can lead to situations where the wrong information shows up
921 in the wrong browser window if the user has multiple windows or
922 browser tabs open>. For example, Window A causes something to be
923 placed in the stash, but before that window performs a redirect,
924 Window B makes a request to the server and gets the status information
925 that should really go to Window A. For this reason, you may wish
926 to use the "query param" technique shown here in your applications.
929 =head1 EXPLORING THE POWER OF DBIC
931 In this section we will explore some additional capabilities offered
932 by DBIx::Class. Although these features have relatively little to do
933 with Catalyst per se, you will almost certainly want to take advantage
934 of them in your applications.
937 =head2 Add Datetime Columns to Our Existing Books Table
939 Let's add two columns to our existing C<books> table to track when
940 each book was added and when each book is updated:
943 sqlite> ALTER TABLE book ADD created INTEGER;
944 sqlite> ALTER TABLE book ADD updated INTEGER;
945 sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
946 sqlite> SELECT * FROM book;
947 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
948 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
949 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
950 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
951 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
952 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
956 This will modify the C<books> table to include the two new fields
957 and populate those fields with the current time.
960 =head2 Update DBIx::Class to Automatically Handle the Datetime Columns
962 Next, we should re-run the DBIC helper to update the Result Classes
965 $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
966 create=static components=TimeStamp dbi:SQLite:myapp.db \
967 on_connect_do="PRAGMA foreign_keys = ON"
968 exists "/root/dev/MyApp/script/../lib/MyApp/Model"
969 exists "/root/dev/MyApp/script/../t"
970 Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
971 Schema dump completed.
972 exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
974 Notice that we modified our use of the helper slightly: we told
975 it to include the L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp>
976 in the C<load_components> line of the Result Classes.
978 If you open C<lib/MyApp/Schema/Result/Book.pm> in your editor you should
979 see that the C<created> and C<updated> fields are now included in the
980 call to C<add_columns()>. However, also notice that the C<many_to_many>
981 relationships we manually added below the "C<# DO NOT MODIFY...>" line
982 were automatically preserved.
984 While we have this file open, let's update it with some additional
985 information to have DBIC automatically handle the updating of these
986 two fields for us. Insert the following code at the bottom of the
987 file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and
988 B<above> the C<1;> on the last line):
991 # Enable automatic date handling
993 __PACKAGE__->add_columns(
995 { data_type => 'datetime', set_on_create => 1 },
997 { data_type => 'datetime', set_on_create => 1, set_on_update => 1 },
1000 This will override the definition for these fields that Schema::Loader
1001 placed at the top of the file. The C<set_on_create> and
1002 C<set_on_update> options will cause DBIx::Class to automatically
1003 update the timestamps in these columns whenever a row is created or
1006 Then enter the following URL into your web browser:
1008 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
1010 You should get the same "Book Created" screen we saw above. However,
1011 if you now use the sqlite3 command-line tool to dump the C<books> table,
1012 you will see that the new book we added has an appropriate date and
1013 time entered for it (see the last line in the listing below):
1015 $ sqlite3 myapp.db "select * from book"
1016 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1017 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1018 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45
1019 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1020 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1021 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
1022 10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42
1024 Notice in the debug log that the SQL DBIC generated has changed to
1025 incorporate the datetime logic:
1027 INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ):
1028 '2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42'
1029 INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10'
1032 =head2 Create a ResultSet Class
1034 An often overlooked but extremely powerful features of DBIC is that it
1035 allows you to supply your own subclasses of C<DBIx::Class::ResultSet>.
1036 It allows you to pull complex and unsightly "query code" out of your
1037 controllers and encapsulate it in a method of your ResultSet Class.
1038 These "canned queries" in your ResultSet Class can then be invoked
1039 via a single call, resulting in much cleaner and easier to read
1042 To illustrate the concept with a fairly simple example, let's create a
1043 method that returns books added in the last 10 minutes. Start by
1044 making a directory where DBIx::Class will look for our ResultSet Class:
1046 $ mkdir lib/MyApp/Schema/ResultSet
1048 Then open C<lib/MyApp/Schema/ResultSet/Book.pm> and enter the following:
1050 package MyApp::Schema::ResultSet::Book;
1054 use base 'DBIx::Class::ResultSet';
1056 =head2 created_after
1058 A predefined search for recently added books
1063 my ($self, $datetime) = @_;
1065 my $date_str = $self->result_source->schema->storage
1066 ->datetime_parser->format_datetime($datetime);
1068 return $self->search({
1069 created => { '>' => $date_str }
1075 Then add the following method to the C<lib/MyApp/Controller/Books.pm>:
1079 List recently created books
1083 sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
1084 my ($self, $c, $mins) = @_;
1086 # Retrieve all of the book records as book model objects and store in the
1087 # stash where they can be accessed by the TT template, but only
1088 # retrieve books created within the last $min number of minutes
1089 $c->stash->{books} = [$c->model('DB::Book')
1090 ->created_after(DateTime->now->subtract(minutes => $mins))];
1092 # Set the TT template to use. You will almost always want to do this
1093 # in your action methods (action methods respond to user input in
1094 # your controllers).
1095 $c->stash->{template} = 'books/list.tt2';
1098 Now try different values for the "minutes" argument (the final number
1099 value) using the URL C<http://localhost:3000/books/list_recent/_#_> in
1100 your browser. For example, this would list all books added in the last
1103 http://localhost:3000/books/list_recent/15
1105 Depending on how recently you added books, you might want to
1106 try a higher or lower value.
1109 =head2 Chaining ResultSets
1111 One of the most helpful and powerful features in DBIx::Class is that
1112 it allows you to "chain together" a series of queries (note that this
1113 has nothing to do with the "Chained Dispatch" for Catalyst that we
1114 were discussing above). Because each ResultSet returns another
1115 ResultSet, you can take an initial query and immediately feed that
1116 into a second query (and so on for as many queries you need). Note
1117 that no matter how many ResultSets you chain together, the database
1118 itself will not be hit until you use a method that attempts to access
1119 the data. And, because this technique carries over to the ResultSet
1120 Class feature we implemented in the previous section for our "canned
1121 search", we can combine the two capabilities. For example, let's add
1122 an action to our C<Books> controller that lists books that are both
1123 recent I<and> have "TCP" in the title. Open up
1124 C<lib/MyApp/Controller/Books.pm> and add the following method:
1126 =head2 list_recent_tcp
1128 List recently created books
1132 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1133 my ($self, $c, $mins) = @_;
1135 # Retrieve all of the book records as book model objects and store in the
1136 # stash where they can be accessed by the TT template, but only
1137 # retrieve books created within the last $min number of minutes
1138 # AND that have 'TCP' in the title
1139 $c->stash->{books} = [$c->model('DB::Book')
1140 ->created_after(DateTime->now->subtract(minutes => $mins))
1141 ->search({title => {'like', '%TCP%'}})
1144 # Set the TT template to use. You will almost always want to do this
1145 # in your action methods (action methods respond to user input in
1146 # your controllers).
1147 $c->stash->{template} = 'books/list.tt2';
1150 To try this out, enter the following URL into your browser:
1152 http://localhost:3000/books/list_recent_tcp/100
1154 And you should get a list of books added in the last 100 minutes that
1155 contain the string "TCP" in the title. However, if you look at all
1156 books within the last 100 minutes, you should get a longer list
1157 (again, you might have to adjust the number of minutes depending on
1158 how recently you added books to your database):
1160 http://localhost:3000/books/list_recent/100
1162 Take a look at the DBIC_TRACE output in the development server log for
1163 the first URL and you should see something similar to the following:
1165 SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me
1166 WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32'
1168 However, let's not pollute our controller code with this raw "TCP"
1169 query -- it would be cleaner to encapsulate that code in a method on
1170 our ResultSet Class. To do this, open
1171 C<lib/MyApp/Schema/ResultSet/Book.pm> and add the following method:
1175 A predefined search for books with a 'LIKE' search in the string
1180 my ($self, $title_str) = @_;
1182 return $self->search({
1183 title => { 'like' => "%$title_str%" }
1187 We defined the search string as C<$title_str> to make the method more
1188 flexible. Now update the C<list_recent_tcp> method in
1189 C<lib/MyApp/Controller/Books.pm> to match the following (we have
1190 replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line
1191 shown here -- the rest of the method should be the same):
1193 =head2 list_recent_tcp
1195 List recently created books
1199 sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
1200 my ($self, $c, $mins) = @_;
1202 # Retrieve all of the book records as book model objects and store in the
1203 # stash where they can be accessed by the TT template, but only
1204 # retrieve books created within the last $min number of minutes
1205 # AND that have 'TCP' in the title
1206 $c->stash->{books} = [$c->model('DB::Book')
1207 ->created_after(DateTime->now->subtract(minutes => $mins))
1211 # Set the TT template to use. You will almost always want to do this
1212 # in your action methods (action methods respond to user input in
1213 # your controllers).
1214 $c->stash->{template} = 'books/list.tt2';
1217 Try out the C<list_recent_tcp> and C<list_recent> URLs as we did above.
1218 They should work just the same, but our code is obviously cleaner and
1219 more modular, while also being more flexible at the same time.
1222 =head2 Adding Methods to Result Classes
1224 In the previous two sections we saw a good example of how we could use
1225 DBIx::Class ResultSet Classes to clean up our code for an entire query
1226 (for example, our "canned searches" that filtered the entire query).
1227 We can do a similar improvement when working with individual rows as
1228 well. Whereas the ResultSet construct is used in DBIC to correspond
1229 to an entire query, the Result Class construct is used to represent a
1230 row. Therefore, we can add row-specific "helper methods" to our Result
1231 Classes stored in C<lib/MyApp/Schema/Result/>. For example, open
1232 C<lib/MyApp/Schema/Result/Author.pm> and add the following method (as
1233 always, it must be above the closing "C<1;>"):
1241 return $self->first_name . ' ' . $self->last_name;
1244 This will allow us to conveniently retrieve both the first and last
1245 name for an author in one shot. Now open C<root/src/books/list.tt2>
1246 and change the definition of C<tt_authors> from this:
1249 [% tt_authors = [ ];
1250 tt_authors.push(author.last_name) FOREACH author = book.authors %]
1256 [% tt_authors = [ ];
1257 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1260 (Only C<author.last_name> was changed to C<author.full_name> -- the
1261 rest of the file should remain the same.)
1263 Now go to the standard book list URL:
1265 http://localhost:3000/books/list
1267 The "Author(s)" column will now contain both the first and last name.
1268 And, because the concatenation logic was encapsulated inside our
1269 Result Class, it keeps the code inside our TT template nice and clean
1270 (remember, we want the templates to be as close to pure HTML markup as
1271 possible). Obviously, this capability becomes even more useful as you
1272 use to to remove even more complicated row-specific logic from your
1276 =head2 Moving Complicated View Code to the Model
1278 The previous section illustrated how we could use a Result Class
1279 method to print the full names of the authors without adding any extra
1280 code to our view, but it still left us with a fairly ugly mess (see
1281 C<root/src/books/list.tt2>):
1285 [% # NOTE: See Chapter 4 for a better way to do this! -%]
1286 [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
1287 [% # loop in 'side effect notation' to load just the last names of the -%]
1288 [% # authors into the list. Note that the 'push' TT vmethod does not print -%]
1289 [% # a value, so nothing will be printed here. But, if you have something -%]
1290 [% # in TT that does return a method and you don't want it printed, you -%]
1291 [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
1292 [% # call it and discard the return value. -%]
1293 [% tt_authors = [ ];
1294 tt_authors.push(author.full_name) FOREACH author = book.authors %]
1295 [% # Now use a TT 'virtual method' to display the author count in parens -%]
1296 [% # Note the use of the TT filter "| html" to escape dangerous characters -%]
1297 ([% tt_authors.size | html %])
1298 [% # Use another TT vmethod to join & print the names & comma separators -%]
1299 [% tt_authors.join(', ') | html %]
1303 Let's combine some of the techniques used earlier in this section to
1304 clean this up. First, let's add a method to our Book Result Class to
1305 return the number of authors for a book. Open
1306 C<lib/MyApp/Schema/Result/Book.pm> and add the following method:
1310 Return the number of authors for the current book
1317 # Use the 'many_to_many' relationship to fetch all of the authors for the current
1318 # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT
1319 return $self->authors->count;
1322 Next, let's add a method to return a list of authors for a book to the
1323 same C<lib/MyApp/Schema/Result/Book.pm> file:
1327 Return a comma-separated list of authors for the current book
1334 # Loop through all authors for the current book, calling all the 'full_name'
1335 # Result Class method for each
1337 foreach my $author ($self->authors) {
1338 push(@names, $author->full_name);
1341 return join(', ', @names);
1344 This method loops through each author, using the C<full_name> Result
1345 Class method we added to C<lib/MyApp/Schema/Result/Author.pm> in the
1348 Using these two methods, we can simplify our TT code. Open
1349 C<root/src/books/list.tt2> and update the "Author(s)" table cell to
1350 match the following:
1354 [% # Print count and author list using Result Class methods -%]
1355 ([% book.author_count | html %]) [% book.author_list | html %]
1359 Although most of the code we removed comprised comments, the overall
1360 effect is dramatic... because our view code is so simple, we don't need
1361 huge comments to clue people in to the gist of our code. The view code
1362 is now self-documenting and readable enough that you could probably get
1363 by with no comments at all. All of the "complex" work is being done in
1364 our Result Class methods (and, because we have broken the code into
1365 nice, modular chucks, the Result Class code is hardly something you
1366 would call complex).
1368 As we saw in this section, always strive to keep your view AND
1369 controller code as simple as possible by pulling code out into your
1370 model objects. Because DBIx::Class can be easily extended in so many
1371 ways, it's an excellent to way accomplish this objective. It will
1372 make your code cleaner, easier to write, less error-prone, and easier
1373 to debug and maintain.
1375 Before you conclude this section, hit Refresh in your browser... the
1376 output should be the same even though the backend code has been trimmed
1382 Kennedy Clark, C<hkclark@gmail.com>
1384 Please report any errors, issues or suggestions to the author. The
1385 most recent version of the Catalyst Tutorial can be found at
1386 L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
1388 Copyright 2006-2008, Kennedy Clark, under Creative Commons License
1389 (L<http://creativecommons.org/licenses/by-sa/3.0/us/>).