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1 | =head1 NAME |
2 | |
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3 | Catalyst::Manual::Tutorial::BasicCRUD - Catalyst Tutorial - Part 3: Basic CRUD |
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4 | |
5 | |
6 | =head1 OVERVIEW |
7 | |
8 | This is B<Part 3 of 9> for the Catalyst tutorial. |
9 | |
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10 | L<Tutorial Overview|Catalyst::Manual::Tutorial> |
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11 | |
12 | =over 4 |
13 | |
14 | =item 1 |
15 | |
16 | L<Introduction|Catalyst::Manual::Tutorial::Intro> |
17 | |
18 | =item 2 |
19 | |
20 | L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics> |
21 | |
22 | =item 3 |
23 | |
24 | B<Basic CRUD> |
25 | |
26 | =item 4 |
27 | |
28 | L<Authentication|Catalyst::Manual::Tutorial::Authentication> |
29 | |
30 | =item 5 |
31 | |
32 | L<Authorization|Catalyst::Manual::Tutorial::Authorization> |
33 | |
34 | =item 6 |
35 | |
36 | L<Debugging|Catalyst::Manual::Tutorial::Debugging> |
37 | |
38 | =item 7 |
39 | |
40 | L<Testing|Catalyst::Manual::Tutorial::Testing> |
41 | |
42 | =item 8 |
43 | |
44 | L<AdvancedCRUD|Catalyst::Manual::Tutorial::AdvancedCRUD> |
45 | |
46 | =item 9 |
47 | |
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48 | L<Appendices|Catalyst::Manual::Tutorial::Appendices> |
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49 | |
50 | =back |
51 | |
52 | |
53 | |
54 | =head1 DESCRIPTION |
55 | |
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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 |
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59 | 2 already implements the Read portion of CRUD (although Read normally |
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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 |
64 | Part 8. |
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65 | |
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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 |
68 | following command: |
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69 | |
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70 | svn co http://dev.catalyst.perl.org/repos/Catalyst/tags/examples/Tutorial/5.7X/BasicCRUD MyApp |
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71 | |
72 | |
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73 | =head1 FORMLESS SUBMISSION |
74 | |
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75 | Our initial attempt at object creation will utilize the "URL arguments" |
76 | feature of Catalyst (we will employ the more common form-based |
77 | submission in the sections that follow). |
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78 | |
79 | |
80 | =head2 Include a Create Action in the Books Controller |
81 | |
82 | Edit C<lib/MyApp/Controller/Books.pm> and enter the following method: |
83 | |
84 | =head2 url_create |
85 | |
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86 | Create a book with the supplied title, rating, and author |
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87 | |
88 | =cut |
89 | |
90 | sub url_create : Local { |
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91 | # In addition to self & context, get the title, rating, & |
92 | # author_id args from the URL. Note that Catalyst automatically |
93 | # puts extra information after the "/<controller_name>/<action_name/" |
94 | # into @_ |
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95 | my ($self, $c, $title, $rating, $author_id) = @_; |
96 | |
97 | # Call create() on the book model object. Pass the table |
98 | # columns/field values we want to set as hash values |
99 | my $book = $c->model('MyAppDB::Book')->create({ |
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100 | title => $title, |
101 | rating => $rating |
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102 | }); |
103 | |
104 | # Add a record to the join table for this book, mapping to |
105 | # appropriate author |
106 | $book->add_to_book_authors({author_id => $author_id}); |
107 | # Note: Above is a shortcut for this: |
108 | # $book->create_related('book_authors', {author_id => $author_id}); |
109 | |
110 | # Assign the Book object to the stash for display in the view |
111 | $c->stash->{book} = $book; |
112 | |
113 | # This is a hack to disable XSUB processing in Data::Dumper |
114 | # (it's used in the view). This is a work-around for a bug in |
115 | # the interaction of some versions or Perl, Data::Dumper & DBIC. |
116 | # You won't need this if you aren't using Data::Dumper (or if |
117 | # you are running DBIC 0.06001 or greater), but adding it doesn't |
118 | # hurt anything either. |
119 | $Data::Dumper::Useperl = 1; |
120 | |
121 | # Set the TT template to use |
122 | $c->stash->{template} = 'books/create_done.tt2'; |
123 | } |
124 | |
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125 | Notice that Catalyst takes "extra slash-separated information" from the |
126 | URL and passes it as arguments in C<@_>. The C<url_create> action then |
127 | uses a simple call to the DBIC C<create> method to add the requested |
128 | information to the database (with a separate call to |
129 | C<add_to_book_authors> to update the join table). As do virtually all |
130 | controller methods (at least the ones that directly handle user input), |
131 | it then sets the template that should handle this request. |
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132 | |
133 | |
134 | =head2 Include a Template for the C<url_create> Action: |
135 | |
136 | Edit C<root/src/books/create_done.tt2> and then enter: |
137 | |
138 | [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%] |
139 | [% # Not a good idea for production use, though. :-) 'Indent=1' is -%] |
140 | [% # optional, but prevents "massive indenting" of deeply nested objects -%] |
141 | [% USE Dumper(Indent=1) -%] |
142 | |
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143 | [% # Set the page title. META can 'go back' and set values in templates -%] |
144 | [% # that have been processed 'before' this template (here it's for -%] |
145 | [% # root/lib/site/html and root/lib/site/header). Note that META on -%] |
146 | [% # simple strings (e.g., no variable interpolation). -%] |
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147 | [% META title = 'Book Created' %] |
148 | |
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149 | [% # Output information about the record that was added. First title. -%] |
150 | <p>Added book '[% book.title %]' |
151 | |
152 | [% # Output the last name of the first author. This is complicated by an -%] |
153 | [% # issue in TT 2.15 where blessed hash objects are not handled right. -%] |
154 | [% # First, fetch 'book.authors' from the DB once. -%] |
155 | [% authors = book.authors %] |
156 | [% # Now use IF statements to test if 'authors.first' is "working". If so, -%] |
157 | [% # we use it. Otherwise we use a hack that seems to keep TT 2.15 happy. -%] |
158 | by '[% authors.first.last_name IF authors.first; |
159 | authors.list.first.value.last_name IF ! authors.first %]' |
160 | |
161 | [% # Output the rating for the book that was added -%] |
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162 | with a rating of [% book.rating %].</p> |
163 | |
164 | [% # Provide a link back to the list page -%] |
165 | [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%] |
166 | <p><a href="[% Catalyst.uri_for('/books/list') %]">Return to list</a></p> |
167 | |
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168 | [% # Try out the TT Dumper (for development only!) -%] |
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169 | <pre> |
170 | Dump of the 'book' variable: |
171 | [% Dumper.dump(book) %] |
172 | </pre> |
173 | |
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174 | The TT C<USE> directive allows access to a variety of plugin modules (TT |
175 | plugins, that is, not Catalyst plugins) to add extra functionality to |
176 | the base TT capabilities. Here, the plugin allows L<Data::Dumper> |
177 | "pretty printing" of objects and variables. Other than that, the rest |
178 | of the code should be familiar from the examples in Part 2. |
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179 | |
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180 | B<IMPORTANT NOTE> As mentioned earlier, the C<MyApp::View::TT.pm> view |
181 | class created by TTSite redefines the name used to access the Catalyst |
182 | context object in TT templates from the usual C<c> to C<Catalyst>. |
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183 | |
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184 | =head2 Try the C<url_create> Feature |
185 | |
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186 | If the application is still running from before, use C<Ctrl-C> to kill |
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187 | it. Then restart the server: |
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188 | |
189 | $ script/myapp_server.pl |
190 | |
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191 | Note that new path for C</books/url_create> appears in the startup debug |
192 | output. |
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193 | |
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194 | B<TIP>: You can use C<script/myapp_server.pl -r> to have the development |
195 | server auto-detect changed files and reload itself (if your browser acts |
196 | odd, you should also try throwing in a C<-k>). If you make changes to |
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197 | the TT templates only, you do not need to reload the development server |
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198 | (only changes to "compiled code" such as Controller and Model C<.pm> |
199 | files require a reload). |
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200 | |
201 | Next, use your browser to enter the following URL: |
202 | |
203 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
204 | |
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205 | Your browser should display " Added book 'TCPIP_Illustrated_Vol-2' by |
206 | 'Stevens' with a rating of 5." along with a dump of the new book model |
207 | object. You should also see the following DBIC debug messages displayed |
208 | in the development server log messages: |
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209 | |
210 | INSERT INTO books (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2' |
211 | INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): `4', `6' |
212 | |
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213 | If you then click the "Return to list" link, you should find that there |
214 | are now six books shown (if necessary, Shift-Reload your browser at the |
215 | C</books/list> page). |
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216 | |
217 | |
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218 | =head1 MANUALLY BUILDING A CREATE FORM |
219 | |
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220 | Although the C<url_create> action in the previous step does begin to |
221 | reveal the power and flexibility of both Catalyst and DBIC, it's |
222 | obviously not a very realistic example of how users should be expected |
223 | to enter data. This section begins to address that concern. |
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224 | |
225 | |
226 | =head2 Add Method to Display The Form |
227 | |
228 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method: |
229 | |
230 | =head2 form_create |
231 | |
232 | Display form to collect information for book to create |
233 | |
234 | =cut |
235 | |
236 | sub form_create : Local { |
237 | my ($self, $c) = @_; |
238 | |
239 | # Set the TT template to use |
240 | $c->stash->{template} = 'books/form_create.tt2'; |
241 | } |
242 | |
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243 | This action simply invokes a view containing a book creation form. |
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244 | |
245 | =head2 Add a Template for the Form |
246 | |
247 | Open C<root/src/books/form_create.tt2> in your editor and enter: |
248 | |
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249 | [% META title = 'Manual Form Book Create' -%] |
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250 | |
251 | <form method="post" action="[% Catalyst.uri_for('form_create_do') %]"> |
252 | <table> |
253 | <tr><td>Title:</td><td><input type="text" name="title"></td></tr> |
254 | <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr> |
255 | <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr> |
256 | </table> |
257 | <input type="submit" name="Submit" value="Submit"> |
258 | </form> |
259 | |
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260 | Note that we have specified the target of the form data as |
261 | C<form_create_do>, the method created in the section that follows. |
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262 | |
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263 | =head2 Add Method to Process Form Values and Update Database |
264 | |
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265 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method to |
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266 | save the form information to the database: |
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267 | |
268 | =head2 form_create_do |
269 | |
270 | Take information from form and add to database |
271 | |
272 | =cut |
273 | |
274 | sub form_create_do : Local { |
275 | my ($self, $c) = @_; |
276 | |
277 | # Retrieve the values from the form |
278 | my $title = $c->request->params->{title} || 'N/A'; |
279 | my $rating = $c->request->params->{rating} || 'N/A'; |
280 | my $author_id = $c->request->params->{author_id} || '1'; |
281 | |
282 | # Create the book |
283 | my $book = $c->model('MyAppDB::Book')->create({ |
284 | title => $title, |
285 | rating => $rating, |
286 | }); |
287 | # Handle relationship with author |
288 | $book->add_to_book_authors({author_id => $author_id}); |
289 | |
290 | # Store new model object in stash |
291 | $c->stash->{book} = $book; |
292 | |
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293 | # Avoid Data::Dumper issue mentioned earlier |
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294 | # You can probably omit this |
295 | $Data::Dumper::Useperl = 1; |
296 | |
297 | # Set the TT template to use |
298 | $c->stash->{template} = 'books/create_done.tt2'; |
299 | } |
300 | |
301 | |
302 | =head2 Test Out The Form |
303 | |
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304 | If the application is still running from before, use C<Ctrl-C> to kill |
305 | it. Then restart the server: |
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306 | |
307 | $ script/myapp_server.pl |
308 | |
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309 | Point your browser to L<http://localhost:3000/books/form_create> and |
310 | enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an |
311 | author ID of 4. You should then be forwarded to the same |
312 | C<create_done.tt2> template seen in earlier examples. Finally, click |
313 | "Return to list" to view the full list of books. |
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314 | |
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315 | B<Note:> Having the user enter the primary key ID for the author is |
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316 | obviously crude; we will address this concern with a drop-down list in |
317 | Part 8. |
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318 | |
319 | =head1 A SIMPLE DELETE FEATURE |
320 | |
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321 | Turning our attention to the delete portion of CRUD, this section |
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322 | illustrates some basic techniques that can be used to remove information |
323 | from the database. |
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324 | |
325 | |
326 | =head2 Include a Delete Link in the List |
327 | |
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328 | Edit C<root/src/books/list.tt2> and update it to the following (two |
329 | sections have changed: 1) the additional '<th>Links</th>' table header, |
330 | and 2) the four lines for the Delete link near the bottom). |
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331 | |
332 | [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%] |
333 | [% # see this "chomping" in your browser because HTML ignores blank lines, but -%] |
334 | [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%] |
335 | [%- # optional, but both the beginning and the ending TT tags support chomping. -%] |
336 | |
337 | [% # Provide a title to root/lib/site/header -%] |
338 | [% META title = 'Book List' -%] |
339 | |
340 | <table> |
341 | <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr> |
342 | [% # Display each book in a table row %] |
343 | [% FOREACH book IN books -%] |
344 | <tr> |
345 | <td>[% book.title %]</td> |
346 | <td>[% book.rating %]</td> |
347 | <td> |
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348 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
349 | [% # loop in 'side effect notation' to load just the last names of the -%] |
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350 | [% # authors into the list. Note that the 'push' TT vmethod does not -%] |
351 | [% # a value, so nothing will be printed here. But, if you have something -%] |
352 | [% # in TT that does return a method and you don't want it printed, you -%] |
353 | [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%] |
354 | [% # call it and discard the return value. -%] |
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355 | [% tt_authors = [ ]; |
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356 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
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357 | [% # Now use a TT 'virtual method' to display the author count -%] |
358 | ([% tt_authors.size %]) |
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359 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
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360 | [% tt_authors.join(', ') %] |
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361 | </td> |
362 | <td> |
363 | [% # Add a link to delete a book %] |
364 | <a href="[% Catalyst.uri_for('delete/') _ book.id %]">Delete</a> |
365 | </td> |
366 | </tr> |
367 | [% END -%] |
368 | </table> |
369 | |
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370 | The additional code is obviously designed to add a new column to the |
371 | right side of the table with a C<Delete> "button" (for simplicity, links |
372 | will be used instead of full HTML buttons). |
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373 | |
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374 | =head2 Add a Delete Action to the Controller |
375 | |
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376 | Open C<lib/MyApp/Controller/Books.pm> in your editor and add the |
377 | following method: |
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378 | |
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379 | =head2 delete |
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380 | |
381 | Delete a book |
382 | |
383 | =cut |
384 | |
385 | sub delete : Local { |
386 | # $id = primary key of book to delete |
387 | my ($self, $c, $id) = @_; |
388 | |
389 | # Search for the book and then delete it |
390 | $c->model('MyAppDB::Book')->search({id => $id})->delete_all; |
391 | |
392 | # Set a status message to be displayed at the top of the view |
393 | $c->stash->{status_msg} = "Book deleted."; |
394 | |
395 | # Forward to the list action/method in this controller |
396 | $c->forward('list'); |
397 | } |
398 | |
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399 | This method first deletes the book with the specified primary key ID. |
400 | However, it also removes the corresponding entry from the |
401 | C<book_authors> table. Note that C<delete_all> was used instead of |
402 | C<delete>: whereas C<delete_all> also removes the join table entries in |
403 | C<book_authors>, C<delete> does not. |
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404 | |
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405 | Then, rather than forwarding to a "delete done" page as we did with the |
406 | earlier create example, it simply sets the C<status_msg> to display a |
407 | notification to the user as the normal list view is rendered. |
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408 | |
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409 | The C<delete> action uses the context C<forward> method to return the |
410 | user to the book list. The C<detach> method could have also been used. |
411 | Whereas C<forward> I<returns> to the original action once it is |
412 | completed, C<detach> does I<not> return. Other than that, the two are |
413 | equivalent. |
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414 | |
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415 | Another alternative to C<forward> would be to use |
416 | C<$c-E<gt>response-E<gt>redirect($c-E<gt>uri_for('/books/list'))>. The |
417 | C<forward> and C<redirect> operations differ in several important |
418 | respects that stem from the fact that redirects cause the client browser |
419 | to issue an entirely new HTTP request. In doing so, this results in a |
420 | new URL showing in the browser window. And, because the stash |
421 | information is reset for every request, the "Book deleted" message would |
422 | not be displayed. |
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423 | |
424 | |
425 | =head2 Try the Delete Feature |
426 | |
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427 | If the application is still running from before, use C<Ctrl-C> to kill |
428 | it. Then restart the server: |
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429 | |
430 | $ script/myapp_server.pl |
431 | |
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432 | Then point your browser to L<http://localhost:3000/books/list> and click |
433 | the "Delete" link next to "TCPIP_Illustrated_Vol-2". A green "Book |
434 | deleted" status message should display at the top of the page, along |
435 | with a list of the six remaining books. |
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436 | |
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437 | |
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438 | =head1 AUTHOR |
439 | |
440 | Kennedy Clark, C<hkclark@gmail.com> |
441 | |
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442 | Please report any errors, issues or suggestions to the author. The |
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443 | most recent version of the Catalyst Tutorial can be found at |
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444 | L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/Catalyst-Runtime/lib/Catalyst/Manual/Tutorial/>. |
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445 | |
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446 | Copyright 2006, Kennedy Clark, under Creative Commons License |
447 | (L<http://creativecommons.org/licenses/by-nc-sa/2.5/>). |
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448 | |