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.
74 =head1 FORMLESS SUBMISSION
76 Our initial attempt at object creation will utilize the "URL arguments"
77 feature of Catalyst (we will employ the more common form-based
78 submission in the sections that follow).
81 =head2 Include a Create Action in the Books Controller
83 Edit C<lib/MyApp/Controller/Books.pm> and enter the following method:
87 Create a book with the supplied title, rating, and author
91 sub url_create : Local {
92 # In addition to self & context, get the title, rating, &
93 # author_id args from the URL. Note that Catalyst automatically
94 # puts extra information after the "/<controller_name>/<action_name/"
97 my ($self, $c, $title, $rating, $author_id) = @_;
99 # Call create() on the book model object. Pass the table
100 # columns/field values we want to set as hash values
101 my $book = $c->model('MyAppDB::Book')->create({
106 # Add a record to the join table for this book, mapping to
108 $book->add_to_book_authors({author_id => $author_id});
109 # Note: Above is a shortcut for this:
110 # $book->create_related('book_authors', {author_id => $author_id});
112 # Assign the Book object to the stash for display in the view
113 $c->stash->{book} = $book;
115 # This is a hack to disable XSUB processing in Data::Dumper
116 # (it's used in the view). This is a work-around for a bug in
117 # the interaction of some versions or Perl, Data::Dumper & DBIC.
118 # You won't need this if you aren't using Data::Dumper (or if
119 # you are running DBIC 0.06001 or greater), but adding it doesn't
120 # hurt anything either.
121 $Data::Dumper::Useperl = 1;
123 # Set the TT template to use
124 $c->stash->{template} = 'books/create_done.tt2';
127 Notice that Catalyst takes "extra slash-separated information" from the
128 URL and passes it as arguments in C<@_>. The C<url_create> action then
129 uses a simple call to the DBIC C<create> method to add the requested
130 information to the database (with a separate call to
131 C<add_to_book_authors> to update the join table). As do virtually all
132 controller methods (at least the ones that directly handle user input),
133 it then sets the template that should handle this request.
136 =head2 Include a Template for the C<url_create> Action:
138 Edit C<root/src/books/create_done.tt2> and then enter:
140 [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%]
141 [% # Not a good idea for production use, though. :-) 'Indent=1' is -%]
142 [% # optional, but prevents "massive indenting" of deeply nested objects -%]
143 [% USE Dumper(Indent=1) -%]
145 [% # Set the page title -%]
146 [% META title = 'Book Created' %]
148 [% # Output information about the record that was added. Note use -%]
149 [% # of 'first' to only list the first author (if > 1 author). -%]
150 <p>Added book '[% book.title %]' by '[% book.authors.first.last_name %]'
151 with a rating of [% book.rating %].</p>
153 [% # Provide a link back to the list page -%]
154 [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%]
155 <p><a href="[% Catalyst.uri_for('/books/list') %]">Return to list</a></p>
157 [% # Try out the TT Dumper (for development only!) -%]
159 Dump of the 'book' variable:
160 [% Dumper.dump(book) %]
163 The TT C<USE> directive allows access to a variety of plugin modules (TT
164 plugins, that is, not Catalyst plugins) to add extra functionality to
165 the base TT capabilities. Here, the plugin allows L<Data::Dumper>
166 "pretty printing" of objects and variables. Other than that, the rest
167 of the code should be familiar from the examples in Part 2.
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>.
173 =head2 Try the C<url_create> Feature
175 If the application is still running from before, use C<Ctrl-C> to kill
176 it. Then restart the server:
178 $ script/myapp_server.pl
180 Note that new path for C</books/url_create> appears in the startup debug
183 B<TIP>: You can use C<script/myapp_server.pl -r> to have the development
184 server auto-detect changed files and reload itself (if your browser acts
185 odd, you should also try throwing in a C<-k>). If you make changes to
186 the TT templates only, you do not need to reload the development server
187 (only changes to "compiled code" such as Controller and Model C<.pm>
188 files require a reload).
190 Next, use your browser to enter the following URL:
192 http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
194 Your browser should display " Added book 'TCPIP_Illustrated_Vol-2' by
195 'Stevens' with a rating of 5." along with a dump of the new book model
196 object. You should also see the following DBIC debug messages displayed
197 in the development server log messages:
199 INSERT INTO books (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
200 INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): `4', `6'
202 If you then click the "Return to list" link, you should find that there
203 are now six books shown (if necessary, Shift-Reload your browser at the
204 C</books/list> page).
207 =head1 MANUALLY BUILDING A CREATE FORM
209 Although the C<url_create> action in the previous step does begin to
210 reveal the power and flexibility of both Catalyst and DBIC, it's
211 obviously not a very realistic example of how users should be expected
212 to enter data. This section begins to address that concern.
215 =head2 Add Method to Display The Form
217 Edit C<lib/MyApp/Controller/Books.pm> and add the following method:
221 Display form to collect information for book to create
225 sub form_create : Local {
228 # Set the TT template to use
229 $c->stash->{template} = 'books/form_create.tt2';
232 This action simply invokes a view containing a book creation form.
234 =head2 Add a Template for the Form
236 Open C<root/src/books/form_create.tt2> in your editor and enter:
238 [% META title = 'Book Create' -%]
240 <form method="post" action="[% Catalyst.uri_for('form_create_do') %]">
242 <tr><td>Title:</td><td><input type="text" name="title"></td></tr>
243 <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
244 <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr>
246 <input type="submit" name="Submit" value="Submit">
249 Note that we have specified the target of the form data as
250 C<form_create_do>, the method created in the section that follows.
252 =head2 Add Method to Process Form Values and Update Database
254 Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
255 save the form information to the databse:
257 =head2 form_create_do
259 Take information from form and add to database
263 sub form_create_do : Local {
266 # Retrieve the values from the form
267 my $title = $c->request->params->{title} || 'N/A';
268 my $rating = $c->request->params->{rating} || 'N/A';
269 my $author_id = $c->request->params->{author_id} || '1';
272 my $book = $c->model('MyAppDB::Book')->create({
276 # Handle relationship with author
277 $book->add_to_book_authors({author_id => $author_id});
279 # Store new model object in stash
280 $c->stash->{book} = $book;
282 # Avoid Data::Dumper issue mentioned earlier
283 # You can probably omit this
284 $Data::Dumper::Useperl = 1;
286 # Set the TT template to use
287 $c->stash->{template} = 'books/create_done.tt2';
291 =head2 Test Out The Form
293 If the application is still running from before, use C<Ctrl-C> to kill
294 it. Then restart the server:
296 $ script/myapp_server.pl
298 Point your browser to L<http://localhost:3000/books/form_create> and
299 enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an
300 author ID of 4. You should then be forwarded to the same
301 C<create_done.tt2> template seen in earlier examples. Finally, click
302 "Return to list" to view the full list of books.
304 B<Note:> Having the user enter the primary key ID for the author is
305 obviously crude; we will address this concern with a drop-down list in
308 =head1 A SIMPLE DELETE FEATURE
310 Turning out attention to the delete portion of CRUD, this section
311 illustrates some basic techniques that can be used to remove information
315 =head2 Include a Delete Link in the List
317 Edit C<root/src/books/list.tt2> and update it to the following (two
318 sections have changed: 1) the additional '<th>Links</th>' table header,
319 and 2) the four lines for the Delete link near the bottom).
321 [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
322 [% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
323 [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
324 [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
326 [% # Provide a title to root/lib/site/header -%]
327 [% META title = 'Book List' -%]
330 <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
331 [% # Display each book in a table row %]
332 [% FOREACH book IN books -%]
334 <td>[% book.title %]</td>
335 <td>[% book.rating %]</td>
337 [% # Print author count in parens. 'book.authors' uses the 'many_to_many' -%]
338 [% # relationship to retrieve all of the authors of a book. 'size' is a -%]
339 [% # TT VMethod to get the number of elements in a list. -%]
340 ([% book.authors.size %])
341 [% # Use an alternate form of a FOREACH loop to display authors. -%]
342 [% # _ below is the TT string concatenation operator. -%]
343 [% author.last_name _' ' FOREACH author = book.authors %]
344 [% # Note: if many_to_many relationship not used in Authors.pm, you could -%]
345 [% # have used the following to 'walk' through the 'join table objects' -%]
346 [% # bk_author.author.last_name _' ' FOREACH bk_author = book.book_authors %]
349 [% # Add a link to delete a book %]
350 <a href="[% Catalyst.uri_for('delete/') _ book.id %]">Delete</a>
356 The additional code is obviously designed to add a new column to the
357 right side of the table with a C<Delete> "button" (for simplicity, links
358 will be used instead of full HTML buttons).
360 =head2 Add a Delete Action to the Controller
362 Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
372 # $id = primary key of book to delete
373 my ($self, $c, $id) = @_;
375 # Search for the book and then delete it
376 $c->model('MyAppDB::Book')->search({id => $id})->delete_all;
378 # Set a status message to be displayed at the top of the view
379 $c->stash->{status_msg} = "Book deleted.";
381 # Forward to the list action/method in this controller
385 This method first deletes the book with the specified primary key ID.
386 However, it also removes the corresponding entry from the
387 C<book_authors> table. Note that C<delete_all> was used instead of
388 C<delete>: whereas C<delete_all> also removes the join table entries in
389 C<book_authors>, C<delete> does not.
391 Then, rather than forwarding to a "delete done" page as we did with the
392 earlier create example, it simply sets the C<status_msg> to display a
393 notification to the user as the normal list view is rendered.
395 The C<delete> action uses the context C<forward> method to return the
396 user to the book list. The C<detach> method could have also been used.
397 Whereas C<forward> I<returns> to the original action once it is
398 completed, C<detach> does I<not> return. Other than that, the two are
401 Another alternative to C<forward> would be to use
402 C<$c-E<gt>response-E<gt>redirect($c-E<gt>uri_for('/books/list'))>. The
403 C<forward> and C<redirect> operations differ in several important
404 respects that stem from the fact that redirects cause the client browser
405 to issue an entirely new HTTP request. In doing so, this results in a
406 new URL showing in the browser window. And, because the stash
407 information is reset for every request, the "Book deleted" message would
411 =head2 Try the Delete Feature
413 If the application is still running from before, use C<Ctrl-C> to kill
414 it. Then restart the server:
416 $ script/myapp_server.pl
418 Then point your browser to L<http://localhost:3000/books/list> and click
419 the "Delete" link next to "TCPIP_Illustrated_Vol-2". A green "Book
420 deleted" status message should display at the top of the page, along
421 with a list of the six remaining books.
425 Kennedy Clark, C<hkclark@gmail.com>
427 Please report any errors, issues or suggestions to the author.
429 Copyright 2006, Kennedy Clark, under Creative Commons License
430 (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).