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1 | =head1 NAME |
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2 | |
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3 | Catalyst::Manual::Tutorial::BasicCRUD - Catalyst Tutorial - Part 4: Basic CRUD |
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4 | |
5 | |
6 | =head1 OVERVIEW |
7 | |
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8 | This is B<Part 4 of 10> for the Catalyst tutorial. |
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9 | |
10 | L<Tutorial Overview|Catalyst::Manual::Tutorial> |
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 | |
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24 | L<More Catalyst Basics|Catalyst::Manual::Tutorial::MoreCatalystBasics> |
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25 | |
26 | =item 4 |
27 | |
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28 | B<Basic CRUD> |
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29 | |
30 | =item 5 |
31 | |
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32 | L<Authentication|Catalyst::Manual::Tutorial::Authentication> |
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33 | |
34 | =item 6 |
35 | |
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36 | L<Authorization|Catalyst::Manual::Tutorial::Authorization> |
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37 | |
38 | =item 7 |
39 | |
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40 | L<Debugging|Catalyst::Manual::Tutorial::Debugging> |
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41 | |
42 | =item 8 |
43 | |
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44 | L<Testing|Catalyst::Manual::Tutorial::Testing> |
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45 | |
46 | =item 9 |
47 | |
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48 | L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD> |
49 | |
50 | =item 10 |
51 | |
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52 | L<Appendices|Catalyst::Manual::Tutorial::Appendices> |
53 | |
54 | =back |
55 | |
56 | |
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57 | =head1 DESCRIPTION |
58 | |
59 | This part of the tutorial builds on the fairly primitive application |
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60 | created in Part 3 to add basic support for Create, Read, Update, and |
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61 | Delete (CRUD) of C<Book> objects. Note that the 'list' function in Part |
62 | 2 already implements the Read portion of CRUD (although Read normally |
63 | refers to reading a single object; you could implement full read |
64 | functionality using the techniques introduced below). This section will |
65 | focus on the Create and Delete aspects of CRUD. More advanced |
66 | capabilities, including full Update functionality, will be addressed in |
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67 | Part 9. |
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68 | |
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69 | Although this part 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's quick |
72 | and easy. For example, see |
73 | L<CatalystX::ListFramework::Builder|CatalystX::ListFramework::Builder>, |
74 | L<CatalystX::CRUD|CatalystX::CRUD>, and |
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75 | L<CatalystX::CRUD::YUI|CatalystX::CRUD::YUI>. |
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76 | |
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77 | You can checkout the source code for this example from the catalyst |
78 | subversion repository as per the instructions in |
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79 | L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>. |
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80 | |
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81 | |
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82 | =head1 FORMLESS SUBMISSION |
83 | |
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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). |
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87 | |
88 | |
89 | =head2 Include a Create Action in the Books Controller |
90 | |
91 | Edit C<lib/MyApp/Controller/Books.pm> and enter the following method: |
92 | |
93 | =head2 url_create |
94 | |
95 | Create a book with the supplied title, rating, and author |
96 | |
97 | =cut |
98 | |
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 @_ |
104 | my ($self, $c, $title, $rating, $author_id) = @_; |
105 | |
106 | # Call create() on the book model object. Pass the table |
107 | # columns/field values we want to set as hash values |
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108 | my $book = $c->model('DB::Books')->create({ |
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109 | title => $title, |
110 | rating => $rating |
111 | }); |
112 | |
113 | # Add a record to the join table for this book, mapping to |
114 | # appropriate author |
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}); |
118 | |
119 | # Assign the Book object to the stash for display in the view |
120 | $c->stash->{book} = $book; |
121 | |
122 | # This is a hack to disable XSUB processing in Data::Dumper |
123 | # (it's used in the view). This is a work-around for a bug in |
124 | # the interaction of some versions or Perl, Data::Dumper & DBIC. |
125 | # You won't need this if you aren't using Data::Dumper (or if |
126 | # you are running DBIC 0.06001 or greater), but adding it doesn't |
127 | # hurt anything either. |
128 | $Data::Dumper::Useperl = 1; |
129 | |
130 | # Set the TT template to use |
131 | $c->stash->{template} = 'books/create_done.tt2'; |
132 | } |
133 | |
134 | Notice that Catalyst takes "extra slash-separated information" from the |
135 | URL and passes it as arguments in C<@_>. The C<url_create> action then |
136 | uses a simple call to the DBIC C<create> method to add the requested |
137 | information to the database (with a separate call to |
138 | C<add_to_book_authors> to update the join table). As do virtually all |
139 | controller methods (at least the ones that directly handle user input), |
140 | it then sets the template that should handle this request. |
141 | |
142 | |
143 | =head2 Include a Template for the C<url_create> Action: |
144 | |
145 | Edit C<root/src/books/create_done.tt2> and then enter: |
146 | |
147 | [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%] |
148 | [% # Not a good idea for production use, though. :-) 'Indent=1' is -%] |
149 | [% # optional, but prevents "massive indenting" of deeply nested objects -%] |
150 | [% USE Dumper(Indent=1) -%] |
151 | |
152 | [% # Set the page title. META can 'go back' and set values in templates -%] |
153 | [% # that have been processed 'before' this template (here it's for -%] |
154 | [% # root/lib/site/html and root/lib/site/header). Note that META on -%] |
155 | [% # simple strings (e.g., no variable interpolation). -%] |
156 | [% META title = 'Book Created' %] |
157 | |
158 | [% # Output information about the record that was added. First title. -%] |
159 | <p>Added book '[% book.title %]' |
160 | |
161 | [% # Output the last name of the first author. This is complicated by an -%] |
162 | [% # issue in TT 2.15 where blessed hash objects are not handled right. -%] |
163 | [% # First, fetch 'book.authors' from the DB once. -%] |
164 | [% authors = book.authors %] |
165 | [% # Now use IF statements to test if 'authors.first' is "working". If so, -%] |
166 | [% # we use it. Otherwise we use a hack that seems to keep TT 2.15 happy. -%] |
167 | by '[% authors.first.last_name IF authors.first; |
168 | authors.list.first.value.last_name IF ! authors.first %]' |
169 | |
170 | [% # Output the rating for the book that was added -%] |
171 | with a rating of [% book.rating %].</p> |
172 | |
173 | [% # Provide a link back to the list page -%] |
174 | [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%] |
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175 | <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p> |
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176 | |
177 | [% # Try out the TT Dumper (for development only!) -%] |
178 | <pre> |
179 | Dump of the 'book' variable: |
180 | [% Dumper.dump(book) %] |
181 | </pre> |
182 | |
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183 | The TT C<USE> directive allows access to a variety of plugin modules |
184 | (TT plugins, that is, not Catalyst plugins) to add extra functionality |
185 | to the base TT capabilities. Here, the plugin allows |
186 | L<Data::Dumper|Data::Dumper> "pretty printing" of objects and |
187 | variables. Other than that, the rest of the code should be familiar |
188 | from the examples in Part 3. |
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189 | |
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190 | |
191 | =head2 Try the C<url_create> Feature |
192 | |
193 | If the application is still running from before, use C<Ctrl-C> to kill |
194 | it. Then restart the server: |
195 | |
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196 | $ DBIC_TRACE=1 script/myapp_server.pl |
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197 | |
198 | Note that new path for C</books/url_create> appears in the startup debug |
199 | output. |
200 | |
201 | B<TIP>: You can use C<script/myapp_server.pl -r> to have the development |
202 | server auto-detect changed files and reload itself (if your browser acts |
203 | odd, you should also try throwing in a C<-k>). If you make changes to |
204 | the TT templates only, you do not need to reload the development server |
205 | (only changes to "compiled code" such as Controller and Model C<.pm> |
206 | files require a reload). |
207 | |
208 | Next, use your browser to enter the following URL: |
209 | |
210 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
211 | |
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212 | Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by |
213 | 'Stevens' with a rating of 5." along with a dump of the new book model |
214 | object as it was returned by DBIC. You should also see the following |
215 | DBIC debug messages displayed in the development server log messages |
216 | if you have DBIC_TRACE set: |
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217 | |
218 | INSERT INTO books (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2' |
219 | INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): `4', `6' |
220 | SELECT author.id, author.first_name, author.last_name |
221 | FROM book_authors me JOIN authors author |
222 | ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '6' |
223 | |
224 | The C<INSERT> statements are obviously adding the book and linking it to |
225 | the existing record for Richard Stevens. The C<SELECT> statement results |
226 | from DBIC automatically fetching the book for the C<Dumper.dump(book)>. |
227 | |
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228 | If you then click the "Return to list" link, you should find that |
229 | there are now six books shown (if necessary, Shift+Reload or |
230 | Ctrl+Reload your browser at the C</books/list> page). |
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231 | |
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232 | |
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233 | =head1 CONVERT TO A CHAINED ACTION |
234 | |
235 | Although the example above uses the same C<Local> action type for the |
236 | method that we saw in the previous part of the tutorial, there is an |
237 | alternate approach that allows us to be more specific while also |
238 | paving the way for more advanced capabilities. Change the method |
239 | declaration for C<url_create> in C<lib/MyApp/Controller/Books.pm> you |
240 | entered above to match the following: |
241 | |
242 | sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) { |
243 | |
244 | This converts the method to take advantage of the Chained |
245 | action/dispatch type. Chaining let's you have a single URL |
246 | automatically dispatch to several controller methods, each of which |
247 | can have precise control over the number of arguments that it will |
248 | receive. A chain can essentially be thought of having three parts -- |
249 | a beginning, a middle and an end. The bullets below summarize the key |
250 | points behind each of these parts of a chain: |
251 | |
252 | |
253 | =over 4 |
254 | |
255 | |
256 | =item * |
257 | |
258 | Beginning |
259 | |
260 | =over 4 |
261 | |
262 | =item * |
263 | |
264 | B<Use "C<:Chained('/')>" to start a chain> |
265 | |
266 | =item * |
267 | |
268 | Get arguments through C<CaptureArgs()> |
269 | |
270 | =item * |
271 | |
272 | Specify the path to match with C<PathPart()> |
273 | |
274 | =back |
275 | |
276 | |
277 | =item * |
278 | |
279 | Middle |
280 | |
281 | =over 4 |
282 | |
283 | =item * |
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284 | |
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285 | Link to previous part of the chain with C<:Chained('_name_')> |
286 | |
287 | =item * |
288 | |
289 | Get arguments through C<CaptureArgs()> |
290 | |
291 | =item * |
292 | |
293 | Specify the path to match with C<PathPart()> |
294 | |
295 | =back |
296 | |
297 | |
298 | =item * |
299 | |
300 | End |
301 | |
302 | =over 4 |
303 | |
304 | =item * |
305 | |
306 | Link to previous part of the chain with C<:Chained('_name_')> |
307 | |
308 | =item * |
309 | |
310 | B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain> |
311 | |
312 | =item * |
313 | |
314 | Specify the path to match with C<PathPart()> |
315 | |
316 | =back |
317 | |
318 | |
319 | =back |
320 | |
321 | In our C<url_create> method above, we have combined all 3 parts into a |
322 | single method: C<:Chained('/')> to start the chain, |
323 | C<:PathPart('books/url_create')> to specify the base URL to match, |
324 | along with C<:Args(3)> to capture exactly 3 arguments and also end the |
325 | chain. |
326 | |
327 | As we will see shortly, a chain can consist of as many "links" as you |
328 | wish, with each part capturing some arguments and doing some work |
329 | along the way. We will continue to use the Chained action type in this |
330 | part of the tutorial and explore slightly more advanced capabilities |
331 | with the base method and delete feature below. But Chained dispatch |
332 | is capable of far more. For additional information, see |
333 | L<Catalyst::Manual::Intro/Action types>, |
334 | L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>, |
335 | and the 2006 advent calendar entry on the subject: |
336 | L<http://www.catalystframework.org/calendar/2006/10>. |
337 | |
338 | |
339 | =head2 Try the Chained Action |
340 | |
341 | If you look back at the development server startup logs from your |
342 | initial version of the C<url_create> method (the one using the |
343 | C<:Local> attribute), you will notice that it produced output similar |
344 | to the following: |
345 | |
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346 | [debug] Loaded Path actions: |
347 | .-------------------------------------+--------------------------------------. |
348 | | Path | Private | |
349 | +-------------------------------------+--------------------------------------+ |
350 | | / | /default | |
351 | | / | /index | |
352 | | /books | /books/index | |
353 | | /books/list | /books/list | |
354 | | /books/url_create | /books/url_create | |
355 | '-------------------------------------+--------------------------------------' |
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356 | |
357 | Now start the development server with our basic chained method in |
358 | place and the startup debug output should change to something along |
359 | the lines of the following: |
360 | |
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361 | [debug] Loaded Path actions: |
362 | .-------------------------------------+--------------------------------------. |
363 | | Path | Private | |
364 | +-------------------------------------+--------------------------------------+ |
365 | | / | /default | |
366 | | / | /index | |
367 | | /books | /books/index | |
368 | | /books/list | /books/list | |
369 | '-------------------------------------+--------------------------------------' |
370 | |
371 | [debug] Loaded Chained actions: |
372 | .-------------------------------------+--------------------------------------. |
373 | | Path Spec | Private | |
374 | +-------------------------------------+--------------------------------------+ |
375 | | /books/url_create/*/*/* | /books/url_create | |
376 | '-------------------------------------+--------------------------------------' |
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377 | |
378 | C<url_create> has disappeared form the "Loaded Path actions" section |
379 | but it now shows up under the newly created "Loaded Chained actions" |
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380 | section. And, the "/*/*/*" portion clearly shows our requirement for |
381 | three arguments. |
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382 | |
383 | As with our non-chained version of C<url_create>, use your browser to |
384 | enter the following URL: |
385 | |
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386 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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387 | |
388 | You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by |
389 | 'Stevens' with a rating of 5." along with a dump of the new book model |
390 | object. Click the "Return to list" link, you should find that there |
391 | are now seven books shown (two copies of TCPIP_Illustrated_Vol-2). |
392 | |
393 | |
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394 | =head2 Refactor to Use a "Base" Method to Start the Chains |
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395 | |
396 | Let's make a quick update to our initial Chained action to show a |
397 | little more of the power of chaining. First, open |
398 | C<lib/MyApp/Controller/Books.pm> in your editor and add the following |
399 | method: |
400 | |
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401 | =head2 base |
402 | |
403 | Can place common logic to start chained dispatch here |
404 | |
405 | =cut |
406 | |
407 | sub base :Chained('/') :PathPart('books') :CaptureArgs(0) { |
408 | my ($self, $c) = @_; |
409 | |
410 | # Store the resultset in stash so it's available for other methods |
411 | $c->stash->{resultset} = $c->model('DB::Books'); |
412 | |
413 | # Print a message to the debug log |
414 | $c->log->debug('*** INSIDE BASE METHOD ***'); |
415 | } |
416 | |
417 | Here we print a log message and store the DBIC resultset in |
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418 | C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available |
419 | for other actions that chain off C<base>. If your controller always |
420 | needs a book ID as it's first argument, you could have the base method |
421 | capture that argument (with C<:CaptureArgs(1)>) and use it to pull the |
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422 | book object with C<-E<gt>find($id)> and leave it in the stash for |
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423 | later parts of your chains to then act upon. Because we have several |
424 | actions that don't need to retrieve a book (such as the C<url_create> |
425 | we are working with now), we will instead add that functionality |
426 | to a common C<object> action shortly. |
427 | |
428 | As for C<url_create>, let's modify it to first dispatch to C<base>. |
429 | Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for |
430 | C<url_create> to match the following: |
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431 | |
432 | sub url_create :Chained('base') :PathPart('url_create') :Args(3) { |
433 | |
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434 | Next, try out the refactored chain by restarting the development |
435 | server. Notice that our "Loaded Chained actions" section has changed |
436 | slightly: |
437 | |
438 | [debug] Loaded Chained actions: |
439 | .-------------------------------------+--------------------------------------. |
440 | | Path Spec | Private | |
441 | +-------------------------------------+--------------------------------------+ |
442 | | /books/url_create/*/*/* | /books/base (0) | |
443 | | | => /books/url_create | |
444 | '-------------------------------------+--------------------------------------' |
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445 | |
446 | The "Path Spec" is the same, but now it maps to two Private actions as |
447 | we would expect. |
448 | |
449 | Once again, enter the following URL into your browser: |
450 | |
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451 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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452 | |
453 | The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a |
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454 | rating of 5" message and dump of the new book object should appear. |
455 | Also notice the extra debug message in the development server output |
456 | from the C<base> method. Click the "Return to list" link, you should |
457 | find that there are now eight books shown. |
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458 | |
459 | |
460 | =head1 MANUALLY BUILDING A CREATE FORM |
461 | |
462 | Although the C<url_create> action in the previous step does begin to |
463 | reveal the power and flexibility of both Catalyst and DBIC, it's |
464 | obviously not a very realistic example of how users should be expected |
465 | to enter data. This section begins to address that concern. |
466 | |
467 | |
468 | =head2 Add Method to Display The Form |
469 | |
470 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method: |
471 | |
472 | =head2 form_create |
473 | |
474 | Display form to collect information for book to create |
475 | |
476 | =cut |
477 | |
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478 | sub form_create :Chained('base') :PathPart('form_create') :Args(0) { |
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479 | my ($self, $c) = @_; |
480 | |
481 | # Set the TT template to use |
482 | $c->stash->{template} = 'books/form_create.tt2'; |
483 | } |
484 | |
485 | This action simply invokes a view containing a book creation form. |
486 | |
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487 | |
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488 | =head2 Add a Template for the Form |
489 | |
490 | Open C<root/src/books/form_create.tt2> in your editor and enter: |
491 | |
492 | [% META title = 'Manual Form Book Create' -%] |
493 | |
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494 | <form method="post" action="[% c.uri_for('form_create_do') %]"> |
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495 | <table> |
496 | <tr><td>Title:</td><td><input type="text" name="title"></td></tr> |
497 | <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr> |
498 | <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr> |
499 | </table> |
500 | <input type="submit" name="Submit" value="Submit"> |
501 | </form> |
502 | |
503 | Note that we have specified the target of the form data as |
504 | C<form_create_do>, the method created in the section that follows. |
505 | |
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506 | |
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507 | =head2 Add a Method to Process Form Values and Update Database |
508 | |
509 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method to |
510 | save the form information to the database: |
511 | |
512 | =head2 form_create_do |
513 | |
514 | Take information from form and add to database |
515 | |
516 | =cut |
517 | |
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518 | sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) { |
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519 | my ($self, $c) = @_; |
520 | |
521 | # Retrieve the values from the form |
522 | my $title = $c->request->params->{title} || 'N/A'; |
523 | my $rating = $c->request->params->{rating} || 'N/A'; |
524 | my $author_id = $c->request->params->{author_id} || '1'; |
525 | |
526 | # Create the book |
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527 | my $book = $c->model('DB::Books')->create({ |
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528 | title => $title, |
529 | rating => $rating, |
530 | }); |
531 | # Handle relationship with author |
532 | $book->add_to_book_authors({author_id => $author_id}); |
533 | |
534 | # Store new model object in stash |
535 | $c->stash->{book} = $book; |
536 | |
537 | # Avoid Data::Dumper issue mentioned earlier |
538 | # You can probably omit this |
539 | $Data::Dumper::Useperl = 1; |
540 | |
541 | # Set the TT template to use |
542 | $c->stash->{template} = 'books/create_done.tt2'; |
543 | } |
544 | |
545 | |
546 | =head2 Test Out The Form |
547 | |
548 | If the application is still running from before, use C<Ctrl-C> to kill |
549 | it. Then restart the server: |
550 | |
551 | $ script/myapp_server.pl |
552 | |
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553 | Notice that the server startup log reflects the two new chained |
554 | methods that we added: |
555 | |
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556 | [debug] Loaded Chained actions: |
557 | .-------------------------------------+--------------------------------------. |
558 | | Path Spec | Private | |
559 | +-------------------------------------+--------------------------------------+ |
560 | | /books/form_create | /books/base (0) | |
561 | | | => /books/form_create | |
562 | | /books/form_create_do | /books/base (0) | |
563 | | | => /books/form_create_do | |
564 | | /books/url_create/*/*/* | /books/base (0) | |
565 | | | => /books/url_create | |
566 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
567 | |
d442cc9f |
568 | Point your browser to L<http://localhost:3000/books/form_create> and |
569 | enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an |
1390ef0e |
570 | author ID of 4. You should then see the output of the same |
d442cc9f |
571 | C<create_done.tt2> template seen in earlier examples. Finally, click |
572 | "Return to list" to view the full list of books. |
573 | |
574 | B<Note:> Having the user enter the primary key ID for the author is |
575 | obviously crude; we will address this concern with a drop-down list in |
3533daff |
576 | Part 9. |
d442cc9f |
577 | |
578 | |
579 | =head1 A SIMPLE DELETE FEATURE |
580 | |
581 | Turning our attention to the delete portion of CRUD, this section |
582 | illustrates some basic techniques that can be used to remove information |
583 | from the database. |
584 | |
585 | |
586 | =head2 Include a Delete Link in the List |
587 | |
588 | Edit C<root/src/books/list.tt2> and update it to the following (two |
589 | sections have changed: 1) the additional '<th>Links</th>' table header, |
590 | and 2) the four lines for the Delete link near the bottom). |
591 | |
592 | [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%] |
593 | [% # see this "chomping" in your browser because HTML ignores blank lines, but -%] |
594 | [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%] |
595 | [%- # optional, but both the beginning and the ending TT tags support chomping. -%] |
596 | |
597 | [% # Provide a title to root/lib/site/header -%] |
598 | [% META title = 'Book List' -%] |
599 | |
600 | <table> |
601 | <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr> |
602 | [% # Display each book in a table row %] |
603 | [% FOREACH book IN books -%] |
604 | <tr> |
605 | <td>[% book.title %]</td> |
606 | <td>[% book.rating %]</td> |
607 | <td> |
608 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
609 | [% # loop in 'side effect notation' to load just the last names of the -%] |
610 | [% # authors into the list. Note that the 'push' TT vmethod does not -%] |
611 | [% # a value, so nothing will be printed here. But, if you have something -%] |
612 | [% # in TT that does return a method and you don't want it printed, you -%] |
613 | [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%] |
614 | [% # call it and discard the return value. -%] |
615 | [% tt_authors = [ ]; |
616 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
617 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
618 | ([% tt_authors.size %]) |
619 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
620 | [% tt_authors.join(', ') %] |
621 | </td> |
622 | <td> |
623 | [% # Add a link to delete a book %] |
e075db0c |
624 | <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a> |
d442cc9f |
625 | </td> |
626 | </tr> |
627 | [% END -%] |
628 | </table> |
629 | |
fe01b24f |
630 | The additional code is obviously designed to add a new column to the |
631 | right side of the table with a C<Delete> "button" (for simplicity, |
632 | links will be used instead of full HTML buttons). |
633 | |
b2ad8bbd |
634 | Also notice that we are using a more advanced form of C<uri_for> than |
0416017e |
635 | we have seen before. Here we use C<$c-E<gt>controller- |
636 | E<gt>action_for> to automatically generate a URI appropriate for that |
637 | action based on the method we want to link to while inserting the |
638 | C<book.id> value into the appropriate place. Now, if you ever change |
639 | C<:PathPart('delete')> in your controller method to |
640 | C<:PathPart('kill')>, then your links will automatically update |
641 | without any changes to your .tt2 template file. As long as the name |
642 | of your method does not changed ("delete" here), then your links will |
643 | still be correct. There are a few shortcuts and options when using |
644 | C<action_for()>: |
645 | |
646 | =over 4 |
647 | |
648 | =item * |
649 | |
650 | If you are referring to a method in the current controller, you can |
651 | use C<$self-E<gt>action_for('_method_name_')>. |
652 | |
653 | =item * |
654 | |
655 | If you are referring to a method in a different controller, you need |
fbbb9084 |
656 | to include that controller's name as an argument to C<controller()>, as in |
0416017e |
657 | C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>. |
658 | |
659 | =back |
b2ad8bbd |
660 | |
c5d94181 |
661 | B<Note:> In practice you should B<never> use a GET request to delete a |
662 | record -- always use POST for actions that will modify data. We are |
663 | doing it here for illustrative and simplicity purposes only. |
d442cc9f |
664 | |
1390ef0e |
665 | |
994b66ad |
666 | =head2 Add a Common Method to Retrieve a Book for the Chain |
667 | |
fbbb9084 |
668 | As mentioned earlier, since we have a mixture of actions that operate |
669 | on a single book ID and others that do no, we should not have C<base> |
994b66ad |
670 | capture the book ID, find the corresponding book in the database and |
671 | save it in the stash for later links in the chain. However, just |
fbbb9084 |
672 | because that logic does not belong in C<base> doesn't mean that we |
673 | can't create another location to centralize the book lookup code. In |
674 | our case, we will create a method called C<object> that will store the |
675 | specific book in the stash. Chains that always operate on a single |
676 | existing book can chain off this method, but methods such as |
677 | C<url_create> that don't operate on an existing book can chain |
678 | directly off base. |
994b66ad |
679 | |
680 | To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm> |
681 | and add the following code: |
682 | |
e075db0c |
683 | =head2 object |
684 | |
685 | Fetch the specified book object based on the book ID and store |
686 | it in the stash |
687 | |
688 | =cut |
689 | |
994b66ad |
690 | sub object :Chained('base') :PathPart('id') :CaptureArgs(1) { |
fbbb9084 |
691 | # $id = primary key of book to delete |
994b66ad |
692 | my ($self, $c, $id) = @_; |
693 | |
694 | # Find the book object and store it in the stash |
695 | $c->stash(object => $c->stash->{resultset}->find($id)); |
696 | |
697 | # Make sure the lookup was successful. You would probably |
698 | # want to do something like this in a real app: |
699 | # $c->detach('/error_404') if !$c->stash->{object}; |
700 | die "Book $id not found!" if !$c->stash->{object}; |
701 | } |
702 | |
703 | Now, any other method that chains off C<object> will automatically |
704 | have the appropriate book waiting for it in |
705 | C<$c-E<gt>stash-Egt>{object}>. |
706 | |
707 | Also note that we are using different technique for setting |
708 | C<$c-E<gt>stash>. The advantage of this style is that it let's you |
709 | set multiple stash variables at a time. For example: |
710 | |
711 | $c->stash(object => $c->stash->{resultset}->find($id), |
712 | another_thing => 1); |
713 | |
714 | or as a hashref: |
715 | |
716 | $c->stash({object => $c->stash->{resultset}->find($id), |
717 | another_thing => 1}); |
718 | |
fbbb9084 |
719 | Either format works, but the C<$c-E<gt>stash(name =E<gt> value);> |
994b66ad |
720 | style is growing in popularity -- you may which to use it all |
721 | the time (even when you are only setting a single value). |
722 | |
723 | |
d442cc9f |
724 | =head2 Add a Delete Action to the Controller |
725 | |
726 | Open C<lib/MyApp/Controller/Books.pm> in your editor and add the |
727 | following method: |
728 | |
1390ef0e |
729 | =head2 delete |
d442cc9f |
730 | |
731 | Delete a book |
732 | |
733 | =cut |
734 | |
994b66ad |
735 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
994b66ad |
736 | my ($self, $c) = @_; |
d442cc9f |
737 | |
994b66ad |
738 | # Use the book object saved by 'object' and delete it along |
739 | # with related 'book_authors' entries |
740 | $c->stash->{object}->delete; |
d442cc9f |
741 | |
742 | # Set a status message to be displayed at the top of the view |
743 | $c->stash->{status_msg} = "Book deleted."; |
744 | |
745 | # Forward to the list action/method in this controller |
746 | $c->forward('list'); |
747 | } |
748 | |
994b66ad |
749 | This method first deletes the book object saved by the C<object> method. |
750 | However, it also removes the corresponding entry from the |
fbbb9084 |
751 | C<book_authors> table with a cascading delete. |
d442cc9f |
752 | |
753 | Then, rather than forwarding to a "delete done" page as we did with the |
754 | earlier create example, it simply sets the C<status_msg> to display a |
755 | notification to the user as the normal list view is rendered. |
756 | |
757 | The C<delete> action uses the context C<forward> method to return the |
758 | user to the book list. The C<detach> method could have also been used. |
759 | Whereas C<forward> I<returns> to the original action once it is |
760 | completed, C<detach> does I<not> return. Other than that, the two are |
761 | equivalent. |
762 | |
763 | |
764 | =head2 Try the Delete Feature |
765 | |
766 | If the application is still running from before, use C<Ctrl-C> to kill |
767 | it. Then restart the server: |
768 | |
994b66ad |
769 | $ DBIC_TRACE=1 script/myapp_server.pl |
d442cc9f |
770 | |
89d3dae9 |
771 | The C<delete> method now appears in the "Loaded Chained actions" section |
772 | of the startup debug output: |
773 | |
fbbb9084 |
774 | [debug] Loaded Chained actions: |
994b66ad |
775 | .-------------------------------------+--------------------------------------. |
776 | | Path Spec | Private | |
777 | +-------------------------------------+--------------------------------------+ |
778 | | /books/id/*/delete | /books/base (0) | |
779 | | | -> /books/object (1) | |
780 | | | => /books/delete | |
781 | | /books/form_create | /books/base (0) | |
782 | | | => /books/form_create | |
783 | | /books/form_create_do | /books/base (0) | |
784 | | | => /books/form_create_do | |
785 | | /books/url_create/*/*/* | /books/base (0) | |
786 | | | => /books/url_create | |
787 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
788 | |
d442cc9f |
789 | Then point your browser to L<http://localhost:3000/books/list> and click |
790 | the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green |
791 | "Book deleted" status message should display at the top of the page, |
994b66ad |
792 | along with a list of the eight remaining books. You will also see the |
793 | cascading delete operation via the DBIC_TRACE output: |
794 | |
795 | DELETE FROM books WHERE ( id = ? ): '6' |
796 | SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '6' |
797 | DELETE FROM book_authors WHERE ( author_id = ? AND book_id = ? ): '4', '6' |
d442cc9f |
798 | |
799 | |
800 | =head2 Fixing a Dangerous URL |
801 | |
5edc2aae |
802 | Note the URL in your browser once you have performed the deletion in the |
d442cc9f |
803 | prior step -- it is still referencing the delete action: |
804 | |
805 | http://localhost:3000/books/delete/6 |
806 | |
fbbb9084 |
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 |
811 | extremely dangerous. |
d442cc9f |
812 | |
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 |
3533daff |
816 | client-side mechanism that causes the browser to issue an entirely |
d442cc9f |
817 | new request. As a result, the URL in the browser is updated to match |
818 | the destination of the redirection URL. |
819 | |
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: |
823 | |
994b66ad |
824 | =head2 delete |
d442cc9f |
825 | |
826 | Delete a book |
994b66ad |
827 | |
d442cc9f |
828 | =cut |
829 | |
994b66ad |
830 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
831 | my ($self, $c) = @_; |
d442cc9f |
832 | |
994b66ad |
833 | # Use the book object saved by 'object' and delete it along |
834 | # with related 'book_authors' entries |
835 | $c->stash->{object}->delete; |
d442cc9f |
836 | |
837 | # Set a status message to be displayed at the top of the view |
838 | $c->stash->{status_msg} = "Book deleted."; |
839 | |
0416017e |
840 | # Redirect the user back to the list page. Note the use |
841 | # of $self->action_for as earlier in this section (BasicCRUD) |
fbbb9084 |
842 | $c->response->redirect($c->uri_for($self->action_for('list'))); |
d442cc9f |
843 | } |
844 | |
845 | |
846 | =head2 Try the Delete and Redirect Logic |
847 | |
848 | Restart the development server and point your browser to |
994b66ad |
849 | L<http://localhost:3000/books/list> (don't just hit "Refresh" in your |
850 | browser since we left the URL in an invalid state in the previous |
851 | section!) and delete the first copy of the remaining two |
852 | "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return |
853 | to the L<http://localhost:3000/books/list> URL, so that is an |
854 | improvement, but notice that I<no green "Book deleted" status message is |
855 | displayed>. Because the stash is reset on every request (and a redirect |
856 | involves a second request), the C<status_msg> is cleared before it can |
857 | be displayed. |
d442cc9f |
858 | |
859 | |
860 | =head2 Using C<uri_for> to Pass Query Parameters |
861 | |
89d3dae9 |
862 | There are several ways to pass information across a redirect. One |
863 | option is to use the C<flash> technique that we will see in Part 5 of |
864 | the tutorial; however, here we will pass the information via query |
865 | parameters on the redirect itself. Open |
866 | C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete> |
867 | method to match the following: |
d442cc9f |
868 | |
869 | =head2 delete |
870 | |
871 | Delete a book |
872 | |
873 | =cut |
874 | |
994b66ad |
875 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
876 | my ($self, $c) = @_; |
d442cc9f |
877 | |
994b66ad |
878 | # Use the book object saved by 'object' and delete it along |
879 | # with related 'book_authors' entries |
880 | $c->stash->{object}->delete; |
d442cc9f |
881 | |
882 | # Redirect the user back to the list page with status msg as an arg |
e075db0c |
883 | $c->response->redirect($c->uri_for($self->action_for('list'), |
d442cc9f |
884 | {status_msg => "Book deleted."})); |
885 | } |
886 | |
887 | This modification simply leverages the ability of C<uri_for> to include |
888 | an arbitrary number of name/value pairs in a hash reference. Next, we |
89d3dae9 |
889 | need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a |
d442cc9f |
890 | query parameter: |
891 | |
1390ef0e |
892 | ... |
d442cc9f |
893 | <div id="content"> |
1390ef0e |
894 | [%# Status and error messages %] |
895 | <span class="message">[% status_msg || c.request.params.status_msg %]</span> |
896 | <span class="error">[% error_msg %]</span> |
897 | [%# This is where TT will stick all of your template's contents. -%] |
898 | [% content %] |
899 | </div><!-- end content --> |
900 | ... |
901 | |
902 | Although the sample above only shows the C<content> div, leave the |
903 | rest of the file intact -- the only change we made to the C<wrapper.tt2> |
904 | was to add "C<|| c.request.params.status_msg>" to the |
905 | C<E<lt>span class="message"E<gt>> line. |
d442cc9f |
906 | |
907 | |
908 | =head2 Try the Delete and Redirect With Query Param Logic |
909 | |
910 | Restart the development server and point your browser to |
994b66ad |
911 | L<http://localhost:3000/books/list> (you should now be able to safely |
912 | hit "refresh" in your browser). Then delete the remaining copy of |
913 | "TCPIP_Illustrated_Vol-2". The green "Book deleted" status message |
d442cc9f |
914 | should return. |
915 | |
89d3dae9 |
916 | B<NOTE:> Another popular method for maintaining server-side |
917 | information across a redirect is to use the C<flash> technique we |
918 | discuss in the next part of the tutorial, |
919 | L<Authentication|Catalyst::Manual::Tutorial::Authentication>. While |
920 | C<flash> is a "slicker" mechanism in that it's all handled by the |
921 | server and doesn't "pollute" your URLs, B<it is important to note that |
922 | C<flash> can lead to situations where the wrong information shows up |
923 | in the wrong browser window if the user has multiple windows or |
994b66ad |
924 | browser tabs open.> For example, Window A causes something to be |
89d3dae9 |
925 | placed in the stash, but before that window performs a redirect, |
926 | Window B makes a request to the server and gets the status information |
994b66ad |
927 | that should really go to Window A. For this reason, you may wish |
89d3dae9 |
928 | to use the "query param" technique shown here in your applications. |
d442cc9f |
929 | |
930 | |
931 | =head1 AUTHOR |
932 | |
933 | Kennedy Clark, C<hkclark@gmail.com> |
934 | |
935 | Please report any errors, issues or suggestions to the author. The |
936 | most recent version of the Catalyst Tutorial can be found at |
82ab4bbf |
937 | L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>. |
d442cc9f |
938 | |
45c7830f |
939 | Copyright 2006-2008, Kennedy Clark, under Creative Commons License |
95674086 |
940 | (L<http://creativecommons.org/licenses/by-sa/3.0/us/>). |