3 Catalyst::Manual::Tutorial::BasicCRUD - Catalyst Tutorial - Part 3: Basic CRUD
8 This is B<Part 3 of 9> for the Catalyst tutorial.
10 L<Tutorial Overview|Catalyst::Manual::Tutorial>
16 L<Introduction|Catalyst::Manual::Tutorial::Intro>
20 L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics>
28 L<Authentication|Catalyst::Manual::Tutorial::Authentication>
32 L<Authorization|Catalyst::Manual::Tutorial::Authorization>
36 L<Debugging|Catalyst::Manual::Tutorial::Debugging>
40 L<Testing|Catalyst::Manual::Tutorial::Testing>
44 L<AdvancedCRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
48 L<Appendicies|Catalyst::Manual::Tutorial::Appendicies>
56 This part of the tutorial builds on the fairly primitive application
57 created in Part 2 to add basic support for Create, Read, Update, and
58 Delete (CRUD) of C<Book> objects. Note that the 'list' function in Part
59 2 already implements the Read portion of Crud (although Read normally
60 refers to reading a single object; you could implement full read
61 functionality using the techniques introduced below). This section will
62 focus on the Create and Delete aspects of CRUD. More advanced
63 capabilities, including full Update functionality, will be addressed in
66 B<TIP>: Note that all of the code for this part of the tutorial can be
67 pulled from the Catalyst Subversion repository in one step with the
70 svn checkout http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/Tutorial@###
71 IMPORTANT: Does not work yet. Will be completed for final version.
75 =head1 FORMLESS SUBMISSION
77 Our initial attempt at object creation will utilize the "URL arguments"
78 feature of Catalyst (we will employ the more common form-based
79 submission in the sections that follow).
82 =head2 Include a Create Action in the Books Controller
84 Edit C<lib/MyApp/Controller/Books.pm> and enter the following method:
88 Create a book with the supplied title, rating and author
92 sub url_create : Local {
93 # In addition to self & context, get the title, rating & author_id args
94 # from the URL. Note that Catalyst automatically puts extra information
95 # after the "/<controller_name>/<action_name/" into @_
96 my ($self, $c, $title, $rating, $author_id) = @_;
98 # Call create() on the book model object. Pass the table
99 # columns/field values we want to set as hash values
100 my $book = $c->model('MyAppDB::Book')->create({
105 # Add a record to the join table for this book, mapping to
107 $book->add_to_book_authors({author_id => $author_id});
108 # Note: Above is a shortcut for this:
109 # $book->create_related('book_authors', {author_id => $author_id});
111 # Assign the Book object to the stash for display in the view
112 $c->stash->{book} = $book;
114 # This is a hack to disable XSUB processing in Data::Dumper
115 # (it's used in the view). This is a work-around for a bug in
116 # the interaction of some versions or Perl, Data::Dumper & DBIC.
117 # You won't need this if you aren't using Data::Dumper (or if
118 # you are running DBIC 0.06001 or greater), but adding it doesn't
119 # hurt anything either.
120 $Data::Dumper::Useperl = 1;
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 C<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 -%]
145 [% META title = 'Book Created' %]
147 [% # Output information about the record that was added. Note use -%]
148 [% # of 'first' to only list the first author (if > 1 author). -%]
149 <p>Added book '[% book.title %]' by '[% book.authors.first.last_name %]'
150 with a rating of [% book.rating %].</p>
152 [% # Provide a link back to the list page -%]
153 [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%]
154 <p><a href="[% Catalyst.uri_for('/books/list') %]">Return to list</a></p>
156 [% # Try out the TT Dumper -%]
158 Dump of the 'book' variable:
159 [% Dumper.dump(book) %]
162 The TT C<USE> directive allows access to a variety of plugin modules (we
163 are talking TT plugins here, not Catalyst plugins) to add extra
164 functionality to the base TT capabilities. Here, the plugin allows
165 L<Data::Dumper|Data::Dumper> "pretty printing" of objects and variables.
166 Other than that, the rest of the code should be familiar from the
169 B<IMPORTANT NOTE> As mentioned earlier, the C<MyApp::View::TT.pm> view
170 class created by TTSite redefines the name used to access the Catalyst
171 context object in TT templates from the usual C<c> to C<Catalyst>.
174 =head2 Try the C<url_create> Feature
176 If the application is still running from before, use C<Ctrl-C> to kill
177 it. Then restart the server:
179 $ script/myapp_server.pl
181 Note that new path for C</books/url_create> appears in the startup debug
184 B<TIP>: You can use C<script/myapp_server.pl -r> to have the development
185 server auto-detect changed files and reload itself (if your browser acts
186 odd, you should also try throwing in a C<-k>). If you make changes to
187 just the TT templates, you do not need to reload the development server
188 (only changes to "compiled code" such as Controller and Model C<.pm>
189 files require a reload).
191 Next, use your browser to enter the following URL:
193 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
195 Your browser should display " Added book 'TCPIP_Illustrated_Vol-2' by
196 'Stevens' with a rating of 5." along with a dump of the new book model
197 object. You should also see the following DBIC debug messages displayed
198 in the development server log messages:
200 INSERT INTO books (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
201 INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): `4', `6'
203 If you then click the "Return to list" link, you should find that there
204 are now six books shown (if necessary, Shift-Reload your browser at the
205 C</books/list> page).
209 =head1 MANUALLY BUILDING A CREATE FORM
211 Although the C<url_create> action in the previous step does begin to
212 reveal the power and flexibility of both Catalyst and DBIC, it's
213 obviously not a very realistic example of how users should be expected
214 to enter data. This section begins to address that concern.
217 =head2 Add Method to Display The Form
219 Edit C<lib/MyApp/Controller/Books.pm> and add the following method:
223 Display form to collect information for book to create
227 sub form_create : Local {
230 # Set the TT template to use
231 $c->stash->{template} = 'books/form_create.tt2';
234 This action merely invokes a view containing a book creation form.
237 =head2 Add a Template for the Form
239 Open C<root/src/books/form_create.tt2> in your editor and enter:
241 [% META title = 'Book Create' -%]
243 <form method="post" action="[% Catalyst.uri_for('form_create_do') %]">
245 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
246 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
247 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
249 <input type="submit" name="Submit" value="Submit">
252 Note that we have specified the target of the form data as
253 C<form_create_do>, the method created in the section that follows.
256 =head2 Add Method to Process Form Values and Update Database
258 Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
259 save the form information to the databse:
261 =head2 form_create_do
263 Take information from form and add to database
267 sub form_create_do : Local {
270 # Retrieve the values from the form
271 my $title = $c->request->params->{title} || 'N/A';
272 my $rating = $c->request->params->{rating} || 'N/A';
273 my $author_id = $c->request->params->{author_id} || '1';
276 my $book = $c->model('MyAppDB::Book')->create({
280 # Handle relationship with author
281 $book->add_to_book_authors({author_id => $author_id});
283 # Store new model object in stash
284 $c->stash->{book} = $book;
286 # Avoid Data::Dumper issue mention earlier
287 # You can probably omit this
288 $Data::Dumper::Useperl = 1;
290 # Set the TT template to use
291 $c->stash->{template} = 'books/create_done.tt2';
295 =head2 Test Out The Form
297 If the application is still running from before, use C<Ctrl-C> to kill it. Then restart the server:
299 $ script/myapp_server.pl
301 Point your browser to L<http://localhost:3000/books/form_create> and
302 enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
303 author ID of 4. You should then be forwarded to the same
304 C<create_done.tt2> template seen in earlier examples. Finally, click
305 "Return to list" to view the full list of books.
307 B<Note:> Having the user enter the primary key ID for the author is
308 obviously a bit crude; we will address this concern with a drop-down
313 =head1 A SIMPLE DELETE FEATURE
315 Turning out attention to the delete portion of CRUD, this section
316 illustrates some basic techniques that can be used to remove information
320 =head2 Include a Delete Link in the List
322 Edit C<root/src/books/list.tt2> and update it to the following (two
323 sections have changed: 1) the additional '<th>Links</th>' table header,
324 and 2) the four lines for the Delete link near the bottom).
326 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
327 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
328 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
329 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
331 [% # Provide a title to root/lib/site/header -%]
332 [% META title = 'Book List' -%]
335 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
336 [% # Display each book in a table row %]
337 [% FOREACH book IN books -%]
339 <td>[% book.title %]</td>
340 <td>[% book.rating %]</td>
342 [% # Print author count in parens. 'book.authors' uses the 'many_to_many' -%]
343 [% # relationship to retrieve all of the authors of a book. 'size' is a -%]
344 [% # TT VMethod to get the number of elements in a list. -%]
345 ([% book.authors.size %])
346 [% # Use an alternate form of a FOREACH loop to display authors. -%]
347 [% # _ below is the TT string concatenation operator. -%]
348 [% author.last_name _' ' FOREACH author = book.authors %]
349 [% # Note: if many_to_many relationship not used in Authors.pm, you could -%]
350 [% # have used the following to 'walk' through the 'join table objects' -%]
351 [% # bk_author.author.last_name _' ' FOREACH bk_author = book.book_authors %]
354 [% # Add a link to delete a book %]
355 <a href="[% Catalyst.uri_for('delete/') _ book.id %]">Delete</a>
361 The additional code is obviously designed to add a new column to the
362 right side of the table with a C<Delete> "button" (for simplicity, links
363 will be used instead of full HTML buttons).
366 =head2 Add a Delete Action to the Controller
368 Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
378 # $id = primary key of book to delete
379 my ($self, $c, $id) = @_;
381 # Search for the book and then delete it
382 $c->model('MyAppDB::Book')->search({id => $id})->delete_all;
384 # Set a status message to be displayed at the top of the view
385 $c->stash->{status_msg} = "Book deleted.";
387 # Forward to the list action/method in this controller
391 This method first deletes the book with the specified primary key ID.
392 However, it also removes the corresponding entry from the
393 C<book_authors> table. Note that C<delete_all> was used instead of
394 C<delete>: whereas C<delete_all> also removes the join table entries in
395 C<book_authors>, C<delete> does not.
397 Then, rather than forwarding to a "delete done" page as we did with the
398 earlier create example, it simply sets the C<status_msg> to display a
399 notification to the user as the normal list view is rendered.
401 The C<delete> action uses the context C<forward> method to return the
402 user to the book list. The C<detach> method could have also been used.
403 Whereas C<forward> I<returns> to the original action once it is
404 completed, C<detach> does I<not> return. Other than that, the two are
407 Another alternative to C<forward> would be to use
408 C<$c-E<gt>response-E<gt>redirect($c-E<gt>uri_for('/books/list'))>. The
409 C<forward> and C<redirect> operations differ in several important
410 respects that stem from the fact that redirects cause the client browser
411 to issue an entirely new HTTP request. In doing so, this results in a
412 new URL showing in the browser window. And, because the stash
413 information is reset for every request, the "Book deleted" message would
417 =head2 Try the Delete Feature
419 If the application is still running from before, use C<Ctrl-C> to kill
420 it. Then restart the server:
422 $ script/myapp_server.pl
424 Then point your browser to L<http://localhost:3000/books/list> and click
425 the "Delete" link next to "TCPIP_Illustrated_Vol-2". A green "Book
426 deleted" status message should display at the top of the page, along
427 with a list of the six remaining books.
432 Kennedy Clark, C<hkclark@gmail.com>
434 Please report any errors, issues or suggestions to the author.
436 Copyright 2006, Kennedy Clark, under Creative Commons License
437 (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).