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1 | =head1 NAME |
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2 | |
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3 | Catalyst::Manual::Tutorial::04_BasicCRUD - Catalyst Tutorial - Chapter 4: Basic CRUD |
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4 | |
5 | |
6 | =head1 OVERVIEW |
7 | |
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8 | This is B<Chapter 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 | |
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16 | L<Introduction|Catalyst::Manual::Tutorial::01_Intro> |
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17 | |
18 | =item 2 |
19 | |
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20 | L<Catalyst Basics|Catalyst::Manual::Tutorial::02_CatalystBasics> |
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21 | |
22 | =item 3 |
23 | |
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24 | L<More Catalyst Basics|Catalyst::Manual::Tutorial::03_MoreCatalystBasics> |
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25 | |
26 | =item 4 |
27 | |
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28 | B<04_Basic CRUD> |
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29 | |
30 | =item 5 |
31 | |
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32 | L<Authentication|Catalyst::Manual::Tutorial::05_Authentication> |
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33 | |
34 | =item 6 |
35 | |
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36 | L<Authorization|Catalyst::Manual::Tutorial::06_Authorization> |
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37 | |
38 | =item 7 |
39 | |
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40 | L<Debugging|Catalyst::Manual::Tutorial::07_Debugging> |
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41 | |
42 | =item 8 |
43 | |
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44 | L<Testing|Catalyst::Manual::Tutorial::08_Testing> |
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45 | |
46 | =item 9 |
47 | |
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48 | L<Advanced CRUD|Catalyst::Manual::Tutorial::09_AdvancedCRUD> |
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49 | |
50 | =item 10 |
51 | |
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52 | L<Appendices|Catalyst::Manual::Tutorial::10_Appendices> |
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53 | |
54 | =back |
55 | |
56 | |
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57 | =head1 DESCRIPTION |
58 | |
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59 | This chapter of the tutorial builds on the fairly primitive |
60 | application created in Chapter 3 to add basic support for Create, |
61 | Read, Update, and Delete (CRUD) of C<Book> objects. Note that the |
62 | 'list' function in Chapter 2 already implements the Read portion of |
63 | CRUD (although Read normally refers to reading a single object; you |
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64 | could implement full Read functionality using the techniques |
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65 | introduced below). This section will focus on the Create and Delete |
66 | aspects of CRUD. More advanced capabilities, including full Update |
67 | functionality, will be addressed in Chapter 9. |
68 | |
69 | Although this chapter of the tutorial will show you how to build CRUD |
70 | functionality yourself, another option is to use a "CRUD builder" type |
71 | of tool to automate the process. You get less control, but it's quick |
72 | and easy. For example, see |
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73 | L<Catalyst::Plugin::AutoCRUD|Catalyst::Plugin::AutoCRUD>, |
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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 check out 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::01_Intro|Catalyst::Manual::Tutorial::01_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 |
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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 |
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94 | |
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95 | Create a book with the supplied title, rating, and author |
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96 | |
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97 | =cut |
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98 | |
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99 | sub url_create : Local { |
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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/" |
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103 | # into @_. The args are separated by the '/' char on the URL. |
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104 | my ($self, $c, $title, $rating, $author_id) = @_; |
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105 | |
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106 | # Call create() on the book model object. Pass the table |
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107 | # columns/field values we want to set as hash values |
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108 | my $book = $c->model('DB::Book')->create({ |
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109 | title => $title, |
110 | rating => $rating |
111 | }); |
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112 | |
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113 | # Add a record to the join table for this book, mapping to |
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114 | # appropriate author |
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115 | $book->add_to_book_authors({author_id => $author_id}); |
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116 | # Note: Above is a shortcut for this: |
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117 | # $book->create_related('book_authors', {author_id => $author_id}); |
118 | |
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119 | # Assign the Book object to the stash for display in the view |
120 | $c->stash->{book} = $book; |
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121 | |
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122 | # Set the TT template to use |
123 | $c->stash->{template} = 'books/create_done.tt2'; |
124 | } |
125 | |
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 |
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130 | C<add_to_book_authors> to update the join table). As do virtually all |
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131 | controller methods (at least the ones that directly handle user input), |
132 | it then sets the template that should handle this request. |
133 | |
134 | |
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135 | =head2 Include a Template for the 'url_create' Action: |
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136 | |
137 | Edit C<root/src/books/create_done.tt2> and then enter: |
138 | |
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) -%] |
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143 | |
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144 | [% # Set the page title. META can 'go back' and set values in templates -%] |
145 | [% # that have been processed 'before' this template (here it's for -%] |
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146 | [% # root/lib/site/html and root/lib/site/header). Note that META only -%] |
147 | [% # works on simple/static strings (i.e. there is no variable -%] |
148 | [% # interpolation). -%] |
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149 | [% META title = 'Book Created' %] |
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150 | |
151 | [% # Output information about the record that was added. First title. -%] |
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152 | <p>Added book '[% book.title %]' |
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153 | |
154 | [% # Output the last name of the first author. -%] |
155 | by '[% book.authors.first.last_name %]' |
156 | |
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157 | [% # Output the rating for the book that was added -%] |
158 | with a rating of [% book.rating %].</p> |
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159 | |
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160 | [% # Provide a link back to the list page -%] |
161 | [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%] |
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162 | <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p> |
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163 | |
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164 | [% # Try out the TT Dumper (for development only!) -%] |
165 | <pre> |
166 | Dump of the 'book' variable: |
167 | [% Dumper.dump(book) %] |
168 | </pre> |
169 | |
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170 | The TT C<USE> directive allows access to a variety of plugin modules |
171 | (TT plugins, that is, not Catalyst plugins) to add extra functionality |
172 | to the base TT capabilities. Here, the plugin allows |
173 | L<Data::Dumper|Data::Dumper> "pretty printing" of objects and |
174 | variables. Other than that, the rest of the code should be familiar |
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175 | from the examples in Chapter 3. |
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176 | |
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177 | Note: If you are using TT v2.15 you will need to change the code that |
178 | outputs the "last name for the first author" above to match this: |
179 | |
180 | [% authors = book.authors %] |
181 | by '[% authors.first.last_name IF authors.first; |
182 | authors.list.first.value.last_name IF ! authors.first %]' |
183 | |
184 | to get around an issue in TT v2.15 where blessed hash objects were not |
185 | handled correctly. But, if you are still using v2.15, it's probably |
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186 | time to upgrade (v2.15 is 3.5+ years old). If you are following |
187 | along in Debian, then you should be on at least v2.20. You can test |
188 | your version of Template Toolkit with the following: |
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189 | |
190 | perl -MTemplate -e 'print "$Template::VERSION\n"' |
191 | |
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192 | |
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193 | =head2 Try the 'url_create' Feature |
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194 | |
195 | If the application is still running from before, use C<Ctrl-C> to kill |
196 | it. Then restart the server: |
197 | |
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198 | $ DBIC_TRACE=1 script/myapp_server.pl |
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199 | |
200 | Note that new path for C</books/url_create> appears in the startup debug |
201 | output. |
202 | |
203 | B<TIP>: You can use C<script/myapp_server.pl -r> to have the development |
204 | server auto-detect changed files and reload itself (if your browser acts |
205 | odd, you should also try throwing in a C<-k>). If you make changes to |
206 | the TT templates only, you do not need to reload the development server |
207 | (only changes to "compiled code" such as Controller and Model C<.pm> |
208 | files require a reload). |
209 | |
210 | Next, use your browser to enter the following URL: |
211 | |
212 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
213 | |
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214 | Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by |
215 | 'Stevens' with a rating of 5." along with a dump of the new book model |
216 | object as it was returned by DBIC. You should also see the following |
217 | DBIC debug messages displayed in the development server log messages |
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218 | if you have DBIC_TRACE set: |
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219 | |
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220 | INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2' |
221 | INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6' |
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222 | |
223 | The C<INSERT> statements are obviously adding the book and linking it to |
224 | the existing record for Richard Stevens. The C<SELECT> statement results |
225 | from DBIC automatically fetching the book for the C<Dumper.dump(book)>. |
226 | |
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227 | If you then click the "Return to list" link, you should find that |
228 | there are now six books shown (if necessary, Shift+Reload or |
229 | Ctrl+Reload your browser at the C</books/list> page). You should now |
230 | see the six DBIC debug messages similar to the following (where |
231 | N=1-6): |
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232 | |
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233 | SELECT author.id, author.first_name, author.last_name |
234 | FROM book_author me JOIN author author |
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235 | ON author.id = me.author_id WHERE ( me.book_id = ? ): 'N' |
236 | |
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237 | |
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238 | =head1 CONVERT TO A CHAINED ACTION |
239 | |
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240 | Although the example above uses the same C<Local> action type for the |
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241 | method that we saw in the previous chapter of the tutorial, there is an |
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242 | alternate approach that allows us to be more specific while also |
243 | paving the way for more advanced capabilities. Change the method |
244 | declaration for C<url_create> in C<lib/MyApp/Controller/Books.pm> you |
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245 | entered above to match the following: |
246 | |
247 | sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) { |
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248 | # In addition to self & context, get the title, rating, & |
249 | # author_id args from the URL. Note that Catalyst automatically |
250 | # puts the first 3 arguments worth of extra information after the |
251 | # "/<controller_name>/<action_name/" into @_ because we specified |
252 | # "Args(3)". The args are separated by the '/' char on the URL. |
253 | my ($self, $c, $title, $rating, $author_id) = @_; |
254 | |
255 | ... |
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256 | |
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257 | This converts the method to take advantage of the Chained |
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258 | action/dispatch type. Chaining lets you have a single URL |
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259 | automatically dispatch to several controller methods, each of which |
260 | can have precise control over the number of arguments that it will |
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261 | receive. A chain can essentially be thought of having three parts -- |
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262 | a beginning, a middle, and an end. The bullets below summarize the key |
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263 | points behind each of these parts of a chain: |
264 | |
265 | |
266 | =over 4 |
267 | |
268 | |
269 | =item * |
270 | |
271 | Beginning |
272 | |
273 | =over 4 |
274 | |
275 | =item * |
276 | |
277 | B<Use "C<:Chained('/')>" to start a chain> |
278 | |
279 | =item * |
280 | |
281 | Get arguments through C<CaptureArgs()> |
282 | |
283 | =item * |
284 | |
285 | Specify the path to match with C<PathPart()> |
286 | |
287 | =back |
288 | |
289 | |
290 | =item * |
291 | |
292 | Middle |
293 | |
294 | =over 4 |
295 | |
296 | =item * |
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297 | |
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298 | Link to previous part of the chain with C<:Chained('_name_')> |
299 | |
300 | =item * |
301 | |
302 | Get arguments through C<CaptureArgs()> |
303 | |
304 | =item * |
305 | |
306 | Specify the path to match with C<PathPart()> |
307 | |
308 | =back |
309 | |
310 | |
311 | =item * |
312 | |
313 | End |
314 | |
315 | =over 4 |
316 | |
317 | =item * |
318 | |
319 | Link to previous part of the chain with C<:Chained('_name_')> |
320 | |
321 | =item * |
322 | |
323 | B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain> |
324 | |
325 | =item * |
326 | |
327 | Specify the path to match with C<PathPart()> |
328 | |
329 | =back |
330 | |
331 | |
332 | =back |
333 | |
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334 | In our C<url_create> method above, we have combined all three parts into |
335 | a single method: C<:Chained('/')> to start the chain, |
336 | C<:PathPart('books/url_create')> to specify the base URL to match, and |
337 | C<:Args(3)> to capture exactly three arguments and to end the chain. |
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338 | |
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339 | As we will see shortly, a chain can consist of as many "links" as you |
340 | wish, with each part capturing some arguments and doing some work |
341 | along the way. We will continue to use the Chained action type in this |
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342 | chapter of the tutorial and explore slightly more advanced capabilities |
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343 | with the base method and delete feature below. But Chained dispatch |
344 | is capable of far more. For additional information, see |
345 | L<Catalyst::Manual::Intro/Action types>, |
346 | L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>, |
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347 | and the 2006 Advent calendar entry on the subject: |
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348 | L<http://www.catalystframework.org/calendar/2006/10>. |
349 | |
350 | |
351 | =head2 Try the Chained Action |
352 | |
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353 | If you look back at the development server startup logs from your |
354 | initial version of the C<url_create> method (the one using the |
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355 | C<:Local> attribute), you will notice that it produced output similar |
356 | to the following: |
357 | |
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358 | [debug] Loaded Path actions: |
359 | .-------------------------------------+--------------------------------------. |
360 | | Path | Private | |
361 | +-------------------------------------+--------------------------------------+ |
362 | | / | /default | |
363 | | / | /index | |
364 | | /books | /books/index | |
365 | | /books/list | /books/list | |
366 | | /books/url_create | /books/url_create | |
367 | '-------------------------------------+--------------------------------------' |
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368 | |
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369 | Now start the development server with our basic chained method in |
370 | place and the startup debug output should change to something along |
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371 | the lines of the following: |
372 | |
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373 | [debug] Loaded Path actions: |
374 | .-------------------------------------+--------------------------------------. |
375 | | Path | Private | |
376 | +-------------------------------------+--------------------------------------+ |
377 | | / | /default | |
378 | | / | /index | |
379 | | /books | /books/index | |
380 | | /books/list | /books/list | |
381 | '-------------------------------------+--------------------------------------' |
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382 | |
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383 | [debug] Loaded Chained actions: |
384 | .-------------------------------------+--------------------------------------. |
385 | | Path Spec | Private | |
386 | +-------------------------------------+--------------------------------------+ |
387 | | /books/url_create/*/*/* | /books/url_create | |
388 | '-------------------------------------+--------------------------------------' |
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389 | |
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390 | C<url_create> has disappeared form the "Loaded Path actions" section |
391 | but it now shows up under the newly created "Loaded Chained actions" |
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392 | section. And the "/*/*/*" portion clearly shows our requirement for |
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393 | three arguments. |
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394 | |
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395 | As with our non-chained version of C<url_create>, use your browser to |
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396 | enter the following URL: |
397 | |
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398 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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399 | |
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400 | You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by |
401 | 'Stevens' with a rating of 5." along with a dump of the new book model |
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402 | object. Click the "Return to list" link, and you should find that there |
403 | are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>). |
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404 | |
405 | |
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406 | =head2 Refactor to Use a 'base' Method to Start the Chains |
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407 | |
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408 | Let's make a quick update to our initial Chained action to show a |
409 | little more of the power of chaining. First, open |
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410 | C<lib/MyApp/Controller/Books.pm> in your editor and add the following |
411 | method: |
412 | |
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413 | =head2 base |
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414 | |
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415 | Can place common logic to start chained dispatch here |
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416 | |
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417 | =cut |
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418 | |
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419 | sub base :Chained('/') :PathPart('books') :CaptureArgs(0) { |
420 | my ($self, $c) = @_; |
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421 | |
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422 | # Store the ResultSet in stash so it's available for other methods |
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423 | $c->stash->{resultset} = $c->model('DB::Book'); |
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424 | |
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425 | # Print a message to the debug log |
426 | $c->log->debug('*** INSIDE BASE METHOD ***'); |
427 | } |
428 | |
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429 | Here we print a log message and store the DBIC ResultSet in |
430 | C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available |
431 | for other actions that chain off C<base>. If your controller always |
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432 | needs a book ID as its first argument, you could have the base method |
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433 | capture that argument (with C<:CaptureArgs(1)>) and use it to pull the |
434 | book object with C<-E<gt>find($id)> and leave it in the stash for |
435 | later parts of your chains to then act upon. Because we have several |
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436 | actions that don't need to retrieve a book (such as the C<url_create> |
437 | we are working with now), we will instead add that functionality |
438 | to a common C<object> action shortly. |
439 | |
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440 | As for C<url_create>, let's modify it to first dispatch to C<base>. |
441 | Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for |
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442 | C<url_create> to match the following: |
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443 | |
444 | sub url_create :Chained('base') :PathPart('url_create') :Args(3) { |
445 | |
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446 | Next, try out the refactored chain by restarting the development |
447 | server. Notice that our "Loaded Chained actions" section has changed |
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448 | slightly: |
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449 | |
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450 | [debug] Loaded Chained actions: |
451 | .-------------------------------------+--------------------------------------. |
452 | | Path Spec | Private | |
453 | +-------------------------------------+--------------------------------------+ |
454 | | /books/url_create/*/*/* | /books/base (0) | |
455 | | | => /books/url_create | |
456 | '-------------------------------------+--------------------------------------' |
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457 | |
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458 | The "Path Spec" is the same, but now it maps to two Private actions as |
459 | we would expect. The C<base> method is being triggered by the |
460 | C</books> part of the URL. However, the processing then continues to |
461 | the C<url_create> method because this method "chained" off C<base> and |
462 | specified C<:PathPart('url_create')> (note that we could have omitted |
463 | the "PathPart" here because it matches the name of the method, but we |
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464 | will include it to make the logic as explicit as possible). |
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465 | |
466 | Once again, enter the following URL into your browser: |
467 | |
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468 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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469 | |
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470 | The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a |
471 | rating of 5." message and a dump of the new book object should appear. |
472 | Also notice the extra "INSIDE BASE METHOD" debug message in the |
473 | development server output from the C<base> method. Click the "Return |
474 | to list" link, and you should find that there are now eight books |
475 | shown. (You may have a larger number of books if you repeated any of |
476 | the "create" actions more than once. Don't worry about it as long as |
477 | the number of books is appropriate for the number of times you added |
478 | new books... there should be the original five books added via |
479 | C<myapp01.sql> plus one additional book for each time you ran one |
480 | of the url_create variations above.) |
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481 | |
482 | |
483 | =head1 MANUALLY BUILDING A CREATE FORM |
484 | |
485 | Although the C<url_create> action in the previous step does begin to |
486 | reveal the power and flexibility of both Catalyst and DBIC, it's |
487 | obviously not a very realistic example of how users should be expected |
488 | to enter data. This section begins to address that concern. |
489 | |
490 | |
491 | =head2 Add Method to Display The Form |
492 | |
493 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method: |
494 | |
495 | =head2 form_create |
fce83e5f |
496 | |
d442cc9f |
497 | Display form to collect information for book to create |
fce83e5f |
498 | |
d442cc9f |
499 | =cut |
fce83e5f |
500 | |
89d3dae9 |
501 | sub form_create :Chained('base') :PathPart('form_create') :Args(0) { |
d442cc9f |
502 | my ($self, $c) = @_; |
fce83e5f |
503 | |
d442cc9f |
504 | # Set the TT template to use |
505 | $c->stash->{template} = 'books/form_create.tt2'; |
506 | } |
507 | |
72609296 |
508 | This action simply invokes a view containing a form to create a book. |
d442cc9f |
509 | |
1390ef0e |
510 | |
d442cc9f |
511 | =head2 Add a Template for the Form |
512 | |
513 | Open C<root/src/books/form_create.tt2> in your editor and enter: |
514 | |
515 | [% META title = 'Manual Form Book Create' -%] |
444d6b27 |
516 | |
8a7c5151 |
517 | <form method="post" action="[% c.uri_for('form_create_do') %]"> |
d442cc9f |
518 | <table> |
519 | <tr><td>Title:</td><td><input type="text" name="title"></td></tr> |
520 | <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr> |
521 | <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr> |
522 | </table> |
523 | <input type="submit" name="Submit" value="Submit"> |
524 | </form> |
525 | |
526 | Note that we have specified the target of the form data as |
527 | C<form_create_do>, the method created in the section that follows. |
528 | |
1390ef0e |
529 | |
d442cc9f |
530 | =head2 Add a Method to Process Form Values and Update Database |
531 | |
532 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method to |
533 | save the form information to the database: |
534 | |
535 | =head2 form_create_do |
fce83e5f |
536 | |
d442cc9f |
537 | Take information from form and add to database |
fce83e5f |
538 | |
d442cc9f |
539 | =cut |
fce83e5f |
540 | |
89d3dae9 |
541 | sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) { |
d442cc9f |
542 | my ($self, $c) = @_; |
fce83e5f |
543 | |
d442cc9f |
544 | # Retrieve the values from the form |
545 | my $title = $c->request->params->{title} || 'N/A'; |
546 | my $rating = $c->request->params->{rating} || 'N/A'; |
547 | my $author_id = $c->request->params->{author_id} || '1'; |
fce83e5f |
548 | |
d442cc9f |
549 | # Create the book |
3b1fa91b |
550 | my $book = $c->model('DB::Book')->create({ |
d442cc9f |
551 | title => $title, |
552 | rating => $rating, |
553 | }); |
554 | # Handle relationship with author |
fce83e5f |
555 | $book->add_to_book_authors({author_id => $author_id}); |
556 | # Note: Above is a shortcut for this: |
557 | # $book->create_related('book_authors', {author_id => $author_id}); |
558 | |
d442cc9f |
559 | # Store new model object in stash |
560 | $c->stash->{book} = $book; |
fce83e5f |
561 | |
d442cc9f |
562 | # Avoid Data::Dumper issue mentioned earlier |
55490817 |
563 | # You can probably omit this |
d442cc9f |
564 | $Data::Dumper::Useperl = 1; |
fce83e5f |
565 | |
d442cc9f |
566 | # Set the TT template to use |
567 | $c->stash->{template} = 'books/create_done.tt2'; |
568 | } |
569 | |
570 | |
571 | =head2 Test Out The Form |
572 | |
573 | If the application is still running from before, use C<Ctrl-C> to kill |
574 | it. Then restart the server: |
575 | |
576 | $ script/myapp_server.pl |
577 | |
55490817 |
578 | Notice that the server startup log reflects the two new chained |
89d3dae9 |
579 | methods that we added: |
580 | |
fbbb9084 |
581 | [debug] Loaded Chained actions: |
582 | .-------------------------------------+--------------------------------------. |
583 | | Path Spec | Private | |
584 | +-------------------------------------+--------------------------------------+ |
585 | | /books/form_create | /books/base (0) | |
586 | | | => /books/form_create | |
587 | | /books/form_create_do | /books/base (0) | |
588 | | | => /books/form_create_do | |
589 | | /books/url_create/*/*/* | /books/base (0) | |
590 | | | => /books/url_create | |
591 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
592 | |
d442cc9f |
593 | Point your browser to L<http://localhost:3000/books/form_create> and |
594 | enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an |
1390ef0e |
595 | author ID of 4. You should then see the output of the same |
d442cc9f |
596 | C<create_done.tt2> template seen in earlier examples. Finally, click |
597 | "Return to list" to view the full list of books. |
598 | |
599 | B<Note:> Having the user enter the primary key ID for the author is |
fce83e5f |
600 | obviously crude; we will address this concern with a drop-down list and |
601 | add validation to our forms in Chapter 9. |
d442cc9f |
602 | |
603 | |
604 | =head1 A SIMPLE DELETE FEATURE |
605 | |
72609296 |
606 | Turning our attention to the Delete portion of CRUD, this section |
d442cc9f |
607 | illustrates some basic techniques that can be used to remove information |
608 | from the database. |
609 | |
610 | |
611 | =head2 Include a Delete Link in the List |
612 | |
1cde0fd6 |
613 | Edit C<root/src/books/list.tt2> and update it to match the following (two |
d442cc9f |
614 | sections have changed: 1) the additional '<th>Links</th>' table header, |
72609296 |
615 | and 2) the four lines for the Delete link near the bottom): |
d442cc9f |
616 | |
617 | [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%] |
618 | [% # see this "chomping" in your browser because HTML ignores blank lines, but -%] |
619 | [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%] |
620 | [%- # optional, but both the beginning and the ending TT tags support chomping. -%] |
fce83e5f |
621 | |
28c32bc6 |
622 | [% # Provide a title -%] |
d442cc9f |
623 | [% META title = 'Book List' -%] |
fce83e5f |
624 | |
d442cc9f |
625 | <table> |
626 | <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr> |
627 | [% # Display each book in a table row %] |
628 | [% FOREACH book IN books -%] |
629 | <tr> |
630 | <td>[% book.title %]</td> |
631 | <td>[% book.rating %]</td> |
632 | <td> |
fce83e5f |
633 | [% # NOTE: See "Exploring The Power of DBIC" for a better way to do this! -%] |
d442cc9f |
634 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
635 | [% # loop in 'side effect notation' to load just the last names of the -%] |
55490817 |
636 | [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%] |
d442cc9f |
637 | [% # a value, so nothing will be printed here. But, if you have something -%] |
55490817 |
638 | [% # in TT that does return a value and you don't want it printed, you can -%] |
6d97b973 |
639 | [% # 1) assign it to a bogus value, or -%] |
640 | [% # 2) use the CALL keyword to call it and discard the return value. -%] |
d442cc9f |
641 | [% tt_authors = [ ]; |
fce83e5f |
642 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
d442cc9f |
643 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
3b1fa91b |
644 | [% # Note the use of the TT filter "| html" to escape dangerous characters -%] |
645 | ([% tt_authors.size | html %]) |
d442cc9f |
646 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
3b1fa91b |
647 | [% tt_authors.join(', ') | html %] |
d442cc9f |
648 | </td> |
649 | <td> |
650 | [% # Add a link to delete a book %] |
e075db0c |
651 | <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a> |
d442cc9f |
652 | </td> |
653 | </tr> |
654 | [% END -%] |
655 | </table> |
656 | |
55490817 |
657 | The additional code is obviously designed to add a new column to the |
72609296 |
658 | right side of the table with a C<Delete> "button" (for simplicity, links |
659 | will be used instead of full HTML buttons; in practice, anything that |
fce83e5f |
660 | modifies data should be handled with a form sending a POST request). |
fe01b24f |
661 | |
55490817 |
662 | Also notice that we are using a more advanced form of C<uri_for> than |
663 | we have seen before. Here we use |
664 | C<$c-E<gt>controller-E<gt>action_for> to automatically generate a URI |
665 | appropriate for that action based on the method we want to link to |
666 | while inserting the C<book.id> value into the appropriate place. Now, |
667 | if you ever change C<:PathPart('delete')> in your controller method to |
668 | C<:PathPart('kill')>, then your links will automatically update |
669 | without any changes to your .tt2 template file. As long as the name |
72609296 |
670 | of your method does not change (here, "delete"), then your links will |
55490817 |
671 | still be correct. There are a few shortcuts and options when using |
0416017e |
672 | C<action_for()>: |
673 | |
674 | =over 4 |
675 | |
676 | =item * |
677 | |
678 | If you are referring to a method in the current controller, you can |
679 | use C<$self-E<gt>action_for('_method_name_')>. |
680 | |
681 | =item * |
682 | |
683 | If you are referring to a method in a different controller, you need |
fbbb9084 |
684 | to include that controller's name as an argument to C<controller()>, as in |
0416017e |
685 | C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>. |
686 | |
687 | =back |
b2ad8bbd |
688 | |
55490817 |
689 | B<Note:> In practice you should B<never> use a GET request to delete a |
690 | record -- always use POST for actions that will modify data. We are |
c5d94181 |
691 | doing it here for illustrative and simplicity purposes only. |
d442cc9f |
692 | |
1390ef0e |
693 | |
994b66ad |
694 | =head2 Add a Common Method to Retrieve a Book for the Chain |
695 | |
55490817 |
696 | As mentioned earlier, since we have a mixture of actions that operate |
697 | on a single book ID and others that do not, we should not have C<base> |
698 | capture the book ID, find the corresponding book in the database and |
699 | save it in the stash for later links in the chain. However, just |
700 | because that logic does not belong in C<base> doesn't mean that we |
701 | can't create another location to centralize the book lookup code. In |
702 | our case, we will create a method called C<object> that will store the |
703 | specific book in the stash. Chains that always operate on a single |
704 | existing book can chain off this method, but methods such as |
705 | C<url_create> that don't operate on an existing book can chain |
fbbb9084 |
706 | directly off base. |
994b66ad |
707 | |
708 | To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm> |
709 | and add the following code: |
710 | |
e075db0c |
711 | =head2 object |
fce83e5f |
712 | |
e075db0c |
713 | Fetch the specified book object based on the book ID and store |
714 | it in the stash |
fce83e5f |
715 | |
e075db0c |
716 | =cut |
fce83e5f |
717 | |
994b66ad |
718 | sub object :Chained('base') :PathPart('id') :CaptureArgs(1) { |
fbbb9084 |
719 | # $id = primary key of book to delete |
994b66ad |
720 | my ($self, $c, $id) = @_; |
fce83e5f |
721 | |
994b66ad |
722 | # Find the book object and store it in the stash |
723 | $c->stash(object => $c->stash->{resultset}->find($id)); |
fce83e5f |
724 | |
994b66ad |
725 | # Make sure the lookup was successful. You would probably |
726 | # want to do something like this in a real app: |
727 | # $c->detach('/error_404') if !$c->stash->{object}; |
728 | die "Book $id not found!" if !$c->stash->{object}; |
fce83e5f |
729 | |
730 | # Print a message to the debug log |
731 | $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***"); |
994b66ad |
732 | } |
733 | |
734 | Now, any other method that chains off C<object> will automatically |
55490817 |
735 | have the appropriate book waiting for it in |
acbd7bdd |
736 | C<$c-E<gt>stash-E<gt>{object}>. |
994b66ad |
737 | |
72609296 |
738 | Also note that we are using a different technique for setting |
739 | C<$c-E<gt>stash>. The advantage of this style is that it lets you set |
740 | multiple stash variables at a time. For example: |
994b66ad |
741 | |
742 | $c->stash(object => $c->stash->{resultset}->find($id), |
743 | another_thing => 1); |
744 | |
745 | or as a hashref: |
746 | |
747 | $c->stash({object => $c->stash->{resultset}->find($id), |
748 | another_thing => 1}); |
749 | |
fbbb9084 |
750 | Either format works, but the C<$c-E<gt>stash(name =E<gt> value);> |
72609296 |
751 | style is growing in popularity -- you may wish to use it all |
994b66ad |
752 | the time (even when you are only setting a single value). |
753 | |
754 | |
d442cc9f |
755 | =head2 Add a Delete Action to the Controller |
756 | |
757 | Open C<lib/MyApp/Controller/Books.pm> in your editor and add the |
758 | following method: |
759 | |
1390ef0e |
760 | =head2 delete |
fce83e5f |
761 | |
d442cc9f |
762 | Delete a book |
fce83e5f |
763 | |
d442cc9f |
764 | =cut |
fce83e5f |
765 | |
994b66ad |
766 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
994b66ad |
767 | my ($self, $c) = @_; |
fce83e5f |
768 | |
994b66ad |
769 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
770 | # with related 'book_author' entries |
994b66ad |
771 | $c->stash->{object}->delete; |
fce83e5f |
772 | |
d442cc9f |
773 | # Set a status message to be displayed at the top of the view |
774 | $c->stash->{status_msg} = "Book deleted."; |
fce83e5f |
775 | |
d442cc9f |
776 | # Forward to the list action/method in this controller |
777 | $c->forward('list'); |
778 | } |
779 | |
55490817 |
780 | This method first deletes the book object saved by the C<object> method. |
781 | However, it also removes the corresponding entry from the |
3b1fa91b |
782 | C<book_author> table with a cascading delete. |
d442cc9f |
783 | |
784 | Then, rather than forwarding to a "delete done" page as we did with the |
785 | earlier create example, it simply sets the C<status_msg> to display a |
786 | notification to the user as the normal list view is rendered. |
787 | |
788 | The C<delete> action uses the context C<forward> method to return the |
789 | user to the book list. The C<detach> method could have also been used. |
790 | Whereas C<forward> I<returns> to the original action once it is |
791 | completed, C<detach> does I<not> return. Other than that, the two are |
792 | equivalent. |
793 | |
794 | |
795 | =head2 Try the Delete Feature |
796 | |
797 | If the application is still running from before, use C<Ctrl-C> to kill |
798 | it. Then restart the server: |
799 | |
994b66ad |
800 | $ DBIC_TRACE=1 script/myapp_server.pl |
d442cc9f |
801 | |
89d3dae9 |
802 | The C<delete> method now appears in the "Loaded Chained actions" section |
803 | of the startup debug output: |
804 | |
fbbb9084 |
805 | [debug] Loaded Chained actions: |
994b66ad |
806 | .-------------------------------------+--------------------------------------. |
807 | | Path Spec | Private | |
808 | +-------------------------------------+--------------------------------------+ |
809 | | /books/id/*/delete | /books/base (0) | |
810 | | | -> /books/object (1) | |
811 | | | => /books/delete | |
812 | | /books/form_create | /books/base (0) | |
813 | | | => /books/form_create | |
814 | | /books/form_create_do | /books/base (0) | |
815 | | | => /books/form_create_do | |
816 | | /books/url_create/*/*/* | /books/base (0) | |
817 | | | => /books/url_create | |
818 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
819 | |
d442cc9f |
820 | Then point your browser to L<http://localhost:3000/books/list> and click |
55490817 |
821 | the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green |
822 | "Book deleted" status message should display at the top of the page, |
994b66ad |
823 | along with a list of the eight remaining books. You will also see the |
824 | cascading delete operation via the DBIC_TRACE output: |
825 | |
3b1fa91b |
826 | SELECT me.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6' |
827 | DELETE FROM book WHERE ( id = ? ): '6' |
828 | SELECT me.book_id, me.author_id FROM book_author me WHERE ( me.book_id = ? ): '6' |
829 | DELETE FROM book_author WHERE ( author_id = ? AND book_id = ? ): '4', '6' |
d442cc9f |
830 | |
831 | |
832 | =head2 Fixing a Dangerous URL |
833 | |
55490817 |
834 | Note the URL in your browser once you have performed the deletion in the |
d442cc9f |
835 | prior step -- it is still referencing the delete action: |
836 | |
acbd7bdd |
837 | http://localhost:3000/books/id/6/delete |
d442cc9f |
838 | |
55490817 |
839 | What if the user were to press reload with this URL still active? In |
840 | this case the redundant delete is harmless (although it does generate |
841 | an exception screen, it doesn't perform any undesirable actions on the |
842 | application or database), but in other cases this could clearly be |
fbbb9084 |
843 | extremely dangerous. |
d442cc9f |
844 | |
845 | We can improve the logic by converting to a redirect. Unlike |
846 | C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform |
847 | a server-side alteration in the flow of processing, a redirect is a |
3533daff |
848 | client-side mechanism that causes the browser to issue an entirely |
d442cc9f |
849 | new request. As a result, the URL in the browser is updated to match |
850 | the destination of the redirection URL. |
851 | |
852 | To convert the forward used in the previous section to a redirect, |
55490817 |
853 | open C<lib/MyApp/Controller/Books.pm> and edit the existing |
d442cc9f |
854 | C<sub delete> method to match: |
855 | |
994b66ad |
856 | =head2 delete |
fce83e5f |
857 | |
d442cc9f |
858 | Delete a book |
fce83e5f |
859 | |
d442cc9f |
860 | =cut |
fce83e5f |
861 | |
994b66ad |
862 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
863 | my ($self, $c) = @_; |
fce83e5f |
864 | |
994b66ad |
865 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
866 | # with related 'book_author' entries |
994b66ad |
867 | $c->stash->{object}->delete; |
fce83e5f |
868 | |
d442cc9f |
869 | # Set a status message to be displayed at the top of the view |
870 | $c->stash->{status_msg} = "Book deleted."; |
fce83e5f |
871 | |
0416017e |
872 | # Redirect the user back to the list page. Note the use |
873 | # of $self->action_for as earlier in this section (BasicCRUD) |
fbbb9084 |
874 | $c->response->redirect($c->uri_for($self->action_for('list'))); |
d442cc9f |
875 | } |
876 | |
877 | |
878 | =head2 Try the Delete and Redirect Logic |
879 | |
55490817 |
880 | Restart the development server and point your browser to |
881 | L<http://localhost:3000/books/list> (don't just hit "Refresh" in your |
882 | browser since we left the URL in an invalid state in the previous |
883 | section!) and delete the first copy of the remaining two |
884 | "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return |
885 | to the L<http://localhost:3000/books/list> URL, so that is an |
886 | improvement, but notice that I<no green "Book deleted" status message is |
887 | displayed>. Because the stash is reset on every request (and a redirect |
888 | involves a second request), the C<status_msg> is cleared before it can |
994b66ad |
889 | be displayed. |
d442cc9f |
890 | |
891 | |
8a472b34 |
892 | =head2 Using 'uri_for' to Pass Query Parameters |
d442cc9f |
893 | |
4b4d3884 |
894 | There are several ways to pass information across a redirect. One |
895 | option is to use the C<flash> technique that we will see in Chapter 5 |
72609296 |
896 | of this tutorial; however, here we will pass the information via query |
4b4d3884 |
897 | parameters on the redirect itself. Open |
898 | C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete> |
89d3dae9 |
899 | method to match the following: |
d442cc9f |
900 | |
55490817 |
901 | =head2 delete |
fce83e5f |
902 | |
d442cc9f |
903 | Delete a book |
fce83e5f |
904 | |
d442cc9f |
905 | =cut |
fce83e5f |
906 | |
994b66ad |
907 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
908 | my ($self, $c) = @_; |
fce83e5f |
909 | |
994b66ad |
910 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
911 | # with related 'book_author' entries |
994b66ad |
912 | $c->stash->{object}->delete; |
fce83e5f |
913 | |
d442cc9f |
914 | # Redirect the user back to the list page with status msg as an arg |
55490817 |
915 | $c->response->redirect($c->uri_for($self->action_for('list'), |
d442cc9f |
916 | {status_msg => "Book deleted."})); |
917 | } |
918 | |
919 | This modification simply leverages the ability of C<uri_for> to include |
55490817 |
920 | an arbitrary number of name/value pairs in a hash reference. Next, we |
921 | need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a |
d442cc9f |
922 | query parameter: |
923 | |
1390ef0e |
924 | ... |
d442cc9f |
925 | <div id="content"> |
1390ef0e |
926 | [%# Status and error messages %] |
927 | <span class="message">[% status_msg || c.request.params.status_msg %]</span> |
928 | <span class="error">[% error_msg %]</span> |
929 | [%# This is where TT will stick all of your template's contents. -%] |
930 | [% content %] |
931 | </div><!-- end content --> |
932 | ... |
933 | |
55490817 |
934 | Although the sample above only shows the C<content> div, leave the |
1390ef0e |
935 | rest of the file intact -- the only change we made to the C<wrapper.tt2> |
55490817 |
936 | was to add "C<|| c.request.params.status_msg>" to the |
1390ef0e |
937 | C<E<lt>span class="message"E<gt>> line. |
d442cc9f |
938 | |
939 | |
940 | =head2 Try the Delete and Redirect With Query Param Logic |
941 | |
55490817 |
942 | Restart the development server and point your browser to |
943 | L<http://localhost:3000/books/list> (you should now be able to safely |
944 | hit "refresh" in your browser). Then delete the remaining copy of |
945 | "TCPIP_Illustrated_Vol-2". The green "Book deleted" status message |
d442cc9f |
946 | should return. |
947 | |
55490817 |
948 | B<NOTE:> Another popular method for maintaining server-side |
949 | information across a redirect is to use the C<flash> technique we |
4b4d3884 |
950 | discuss in the next chapter of the tutorial, |
3ab6187c |
951 | L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>. While |
55490817 |
952 | C<flash> is a "slicker" mechanism in that it's all handled by the |
953 | server and doesn't "pollute" your URLs, B<it is important to note that |
954 | C<flash> can lead to situations where the wrong information shows up |
955 | in the wrong browser window if the user has multiple windows or |
72609296 |
956 | browser tabs open>. For example, Window A causes something to be |
55490817 |
957 | placed in the stash, but before that window performs a redirect, |
958 | Window B makes a request to the server and gets the status information |
994b66ad |
959 | that should really go to Window A. For this reason, you may wish |
89d3dae9 |
960 | to use the "query param" technique shown here in your applications. |
d442cc9f |
961 | |
962 | |
1cde0fd6 |
963 | =head1 EXPLORING THE POWER OF DBIC |
964 | |
55490817 |
965 | In this section we will explore some additional capabilities offered |
966 | by DBIx::Class. Although these features have relatively little to do |
967 | with Catalyst per se, you will almost certainly want to take advantage |
1cde0fd6 |
968 | of them in your applications. |
969 | |
970 | |
1cde0fd6 |
971 | =head2 Add Datetime Columns to Our Existing Books Table |
972 | |
55490817 |
973 | Let's add two columns to our existing C<books> table to track when |
1cde0fd6 |
974 | each book was added and when each book is updated: |
975 | |
976 | $ sqlite3 myapp.db |
3b1fa91b |
977 | sqlite> ALTER TABLE book ADD created INTEGER; |
978 | sqlite> ALTER TABLE book ADD updated INTEGER; |
979 | sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW'); |
980 | sqlite> SELECT * FROM book; |
acbd7bdd |
981 | 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
982 | 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
983 | 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35 |
984 | 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
985 | 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
986 | 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1cde0fd6 |
987 | sqlite> .quit |
988 | $ |
989 | |
990 | This will modify the C<books> table to include the two new fields |
991 | and populate those fields with the current time. |
992 | |
acbd7bdd |
993 | |
a46b474e |
994 | =head2 Update DBIx::Class to Automatically Handle the Datetime Columns |
1cde0fd6 |
995 | |
996 | Next, we should re-run the DBIC helper to update the Result Classes |
997 | with the new fields: |
998 | |
999 | $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \ |
b66dd084 |
1000 | create=static components=TimeStamp dbi:SQLite:myapp.db \ |
1001 | on_connect_do="PRAGMA foreign_keys = ON" |
1cde0fd6 |
1002 | exists "/root/dev/MyApp/script/../lib/MyApp/Model" |
1003 | exists "/root/dev/MyApp/script/../t" |
1004 | Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ... |
1005 | Schema dump completed. |
1006 | exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm" |
1007 | |
1008 | Notice that we modified our use of the helper slightly: we told |
d05dbc42 |
1009 | it to include the L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp> |
1cde0fd6 |
1010 | in the C<load_components> line of the Result Classes. |
1011 | |
3b1fa91b |
1012 | If you open C<lib/MyApp/Schema/Result/Book.pm> in your editor you |
55490817 |
1013 | should see that the C<created> and C<updated> fields are now included |
72609296 |
1014 | in the call to C<add_columns()>, but our relationship information below |
55490817 |
1015 | the "C<# DO NOT MODIFY...>" line was automatically preserved. |
1cde0fd6 |
1016 | |
55490817 |
1017 | While we have this file open, let's update it with some additional |
1018 | information to have DBIC automatically handle the updating of these |
1019 | two fields for us. Insert the following code at the bottom of the |
1020 | file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and |
1cde0fd6 |
1021 | B<above> the C<1;> on the last line): |
1022 | |
1023 | # |
1024 | # Enable automatic date handling |
1025 | # |
1026 | __PACKAGE__->add_columns( |
1027 | "created", |
1028 | { data_type => 'datetime', set_on_create => 1 }, |
1029 | "updated", |
1030 | { data_type => 'datetime', set_on_create => 1, set_on_update => 1 }, |
55490817 |
1031 | ); |
1cde0fd6 |
1032 | |
a46b474e |
1033 | This will override the definition for these fields that Schema::Loader |
1034 | placed at the top of the file. The C<set_on_create> and |
1035 | C<set_on_update> options will cause DBIx::Class to automatically |
1036 | update the timestamps in these columns whenever a row is created or |
1037 | modified. |
1cde0fd6 |
1038 | |
1039 | To test this out, restart the development server using the |
1040 | C<DBIC_TRACE=1> option: |
1041 | |
1042 | DBIC_TRACE=1 script/myapp_server.pl |
1043 | |
1044 | Then enter the following URL into your web browser: |
1045 | |
1046 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
1047 | |
1048 | You should get the same "Book Created" screen we saw above. However, |
1049 | if you now use the sqlite3 command-line tool to dump the C<books> table, |
1050 | you will see that the new book we added has an appropriate date and |
1051 | time entered for it (see the last line in the listing below): |
1052 | |
444d6b27 |
1053 | $ sqlite3 myapp.db "select * from book" |
acbd7bdd |
1054 | 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1055 | 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1056 | 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1057 | 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1058 | 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1059 | 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1060 | 10|TCPIP_Illustrated_Vol-2|5|2009-03-08 16:29:08|2009-03-08 16:29:08 |
1cde0fd6 |
1061 | |
55490817 |
1062 | Notice in the debug log that the SQL DBIC generated has changed to |
1cde0fd6 |
1063 | incorporate the datetime logic: |
1064 | |
2a6eb5f9 |
1065 | INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ): |
fce83e5f |
1066 | '2009-05-25 20:39:41', '5', 'TCPIP_Illustrated_Vol-2', '2009-05-25 20:39:41' |
2a6eb5f9 |
1067 | INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10' |
1cde0fd6 |
1068 | |
1069 | |
1070 | =head2 Create a ResultSet Class |
1071 | |
444d6b27 |
1072 | An often overlooked but extremely powerful features of DBIC is that it |
55490817 |
1073 | allows you to supply your own subclasses of C<DBIx::Class::ResultSet>. |
1074 | It allows you to pull complex and unsightly "query code" out of your |
1cde0fd6 |
1075 | controllers and encapsulate it in a method of your ResultSet Class. |
1076 | These "canned queries" in your ResultSet Class can then be invoked |
1077 | via a single call, resulting in much cleaner and easier to read |
1078 | controller code. |
1079 | |
55490817 |
1080 | To illustrate the concept with a fairly simple example, let's create a |
1cde0fd6 |
1081 | method that returns books added in the last 10 minutes. Start by |
a46b474e |
1082 | making a directory where DBIx::Class will look for our ResultSet Class: |
1cde0fd6 |
1083 | |
444d6b27 |
1084 | $ mkdir lib/MyApp/Schema/ResultSet |
1cde0fd6 |
1085 | |
3b1fa91b |
1086 | Then open C<lib/MyApp/Schema/ResultSet/Book.pm> and enter the following: |
1cde0fd6 |
1087 | |
3b1fa91b |
1088 | package MyApp::Schema::ResultSet::Book; |
fce83e5f |
1089 | |
1cde0fd6 |
1090 | use strict; |
1091 | use warnings; |
1092 | use base 'DBIx::Class::ResultSet'; |
fce83e5f |
1093 | |
1cde0fd6 |
1094 | =head2 created_after |
fce83e5f |
1095 | |
1cde0fd6 |
1096 | A predefined search for recently added books |
fce83e5f |
1097 | |
1cde0fd6 |
1098 | =cut |
fce83e5f |
1099 | |
1cde0fd6 |
1100 | sub created_after { |
fadc4ae7 |
1101 | my ($self, $datetime) = @_; |
fce83e5f |
1102 | |
b66dd084 |
1103 | my $date_str = $self->result_source->schema->storage |
fadc4ae7 |
1104 | ->datetime_parser->format_datetime($datetime); |
fce83e5f |
1105 | |
fadc4ae7 |
1106 | return $self->search({ |
1107 | created => { '>' => $date_str } |
1108 | }); |
1cde0fd6 |
1109 | } |
fce83e5f |
1110 | |
1cde0fd6 |
1111 | 1; |
1112 | |
1cde0fd6 |
1113 | Then add the following method to the C<lib/MyApp/Controller/Books.pm>: |
1114 | |
1115 | =head2 list_recent |
fce83e5f |
1116 | |
1cde0fd6 |
1117 | List recently created books |
fce83e5f |
1118 | |
1cde0fd6 |
1119 | =cut |
fce83e5f |
1120 | |
1cde0fd6 |
1121 | sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) { |
1122 | my ($self, $c, $mins) = @_; |
fce83e5f |
1123 | |
1cde0fd6 |
1124 | # Retrieve all of the book records as book model objects and store in the |
1125 | # stash where they can be accessed by the TT template, but only |
1126 | # retrieve books created within the last $min number of minutes |
3b1fa91b |
1127 | $c->stash->{books} = [$c->model('DB::Book') |
1cde0fd6 |
1128 | ->created_after(DateTime->now->subtract(minutes => $mins))]; |
fce83e5f |
1129 | |
1cde0fd6 |
1130 | # Set the TT template to use. You will almost always want to do this |
1131 | # in your action methods (action methods respond to user input in |
1132 | # your controllers). |
1133 | $c->stash->{template} = 'books/list.tt2'; |
1134 | } |
1135 | |
55490817 |
1136 | Now start the development server with C<DBIC_TRACE=1> and try |
1137 | different values for the minutes argument (the final number value) for |
1138 | the URL C<http://localhost:3000/books/list_recent/10>. For example, |
1cde0fd6 |
1139 | this would list all books added in the last fifteen minutes: |
1140 | |
1141 | http://localhost:3000/books/list_recent/15 |
1142 | |
1143 | Depending on how recently you added books, you might want to |
1144 | try a higher or lower value. |
1145 | |
1146 | |
1147 | =head2 Chaining ResultSets |
1148 | |
a46b474e |
1149 | One of the most helpful and powerful features in DBIx::Class is that |
1150 | it allows you to "chain together" a series of queries (note that this |
1151 | has nothing to do with the "Chained Dispatch" for Catalyst that we |
1152 | were discussing above). Because each ResultSet returns another |
1153 | ResultSet, you can take an initial query and immediately feed that |
1154 | into a second query (and so on for as many queries you need). Note |
1155 | that no matter how many ResultSets you chain together, the database |
1156 | itself will not be hit until you use a method that attempts to access |
1157 | the data. And, because this technique carries over to the ResultSet |
1158 | Class feature we implemented in the previous section for our "canned |
1159 | search", we can combine the two capabilities. For example, let's add |
1160 | an action to our C<Books> controller that lists books that are both |
1161 | recent I<and> have "TCP" in the title. Open up |
1162 | C<lib/MyApp/Controller/Books.pm> and add the following method: |
1cde0fd6 |
1163 | |
acbd7bdd |
1164 | =head2 list_recent_tcp |
fce83e5f |
1165 | |
1cde0fd6 |
1166 | List recently created books |
fce83e5f |
1167 | |
1cde0fd6 |
1168 | =cut |
fce83e5f |
1169 | |
1cde0fd6 |
1170 | sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) { |
1171 | my ($self, $c, $mins) = @_; |
fce83e5f |
1172 | |
1cde0fd6 |
1173 | # Retrieve all of the book records as book model objects and store in the |
1174 | # stash where they can be accessed by the TT template, but only |
1175 | # retrieve books created within the last $min number of minutes |
1176 | # AND that have 'TCP' in the title |
3b1fa91b |
1177 | $c->stash->{books} = [$c->model('DB::Book') |
1cde0fd6 |
1178 | ->created_after(DateTime->now->subtract(minutes => $mins)) |
1179 | ->search({title => {'like', '%TCP%'}}) |
1180 | ]; |
fce83e5f |
1181 | |
1cde0fd6 |
1182 | # Set the TT template to use. You will almost always want to do this |
1183 | # in your action methods (action methods respond to user input in |
1184 | # your controllers). |
1185 | $c->stash->{template} = 'books/list.tt2'; |
1186 | } |
1187 | |
1188 | To try this out, restart the development server with: |
1189 | |
1190 | DBIC_TRACE=1 script/myapp_server.pl |
1191 | |
1192 | And enter the following URL into your browser: |
1193 | |
1194 | http://localhost:3000/books/list_recent_tcp/100 |
1195 | |
55490817 |
1196 | And you should get a list of books added in the last 100 minutes that |
1197 | contain the string "TCP" in the title. However, if you look at all |
1198 | books within the last 100 minutes, you should get a longer list |
1199 | (again, you might have to adjust the number of minutes depending on |
1cde0fd6 |
1200 | how recently you added books to your database): |
1201 | |
1202 | http://localhost:3000/books/list_recent/100 |
1203 | |
55490817 |
1204 | Take a look at the DBIC_TRACE output in the development server log for |
1cde0fd6 |
1205 | the first URL and you should see something similar to the following: |
1206 | |
fce83e5f |
1207 | SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me |
1208 | WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2009-05-25 19:09:13' |
1cde0fd6 |
1209 | |
55490817 |
1210 | However, let's not pollute our controller code with this raw "TCP" |
1211 | query -- it would be cleaner to encapsulate that code in a method on |
1212 | our ResultSet Class. To do this, open |
3b1fa91b |
1213 | C<lib/MyApp/Schema/ResultSet/Book.pm> and add the following method: |
1cde0fd6 |
1214 | |
1215 | =head2 title_like |
fce83e5f |
1216 | |
1cde0fd6 |
1217 | A predefined search for books with a 'LIKE' search in the string |
fce83e5f |
1218 | |
1cde0fd6 |
1219 | =cut |
fce83e5f |
1220 | |
1cde0fd6 |
1221 | sub title_like { |
fadc4ae7 |
1222 | my ($self, $title_str) = @_; |
fce83e5f |
1223 | |
fadc4ae7 |
1224 | return $self->search({ |
1225 | title => { 'like' => "%$title_str%" } |
1226 | }); |
1cde0fd6 |
1227 | } |
1228 | |
55490817 |
1229 | We defined the search string as C<$title_str> to make the method more |
1230 | flexible. Now update the C<list_recent_tcp> method in |
1231 | C<lib/MyApp/Controller/Books.pm> to match the following (we have |
1232 | replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line |
1cde0fd6 |
1233 | shown here -- the rest of the method should be the same): |
1234 | |
1235 | =head2 list_recent_tcp |
fce83e5f |
1236 | |
1cde0fd6 |
1237 | List recently created books |
fce83e5f |
1238 | |
1cde0fd6 |
1239 | =cut |
fce83e5f |
1240 | |
1cde0fd6 |
1241 | sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) { |
1242 | my ($self, $c, $mins) = @_; |
fce83e5f |
1243 | |
1cde0fd6 |
1244 | # Retrieve all of the book records as book model objects and store in the |
1245 | # stash where they can be accessed by the TT template, but only |
1246 | # retrieve books created within the last $min number of minutes |
1247 | # AND that have 'TCP' in the title |
3b1fa91b |
1248 | $c->stash->{books} = [$c->model('DB::Book') |
1cde0fd6 |
1249 | ->created_after(DateTime->now->subtract(minutes => $mins)) |
1250 | ->title_like('TCP') |
1251 | ]; |
fce83e5f |
1252 | |
1cde0fd6 |
1253 | # Set the TT template to use. You will almost always want to do this |
1254 | # in your action methods (action methods respond to user input in |
1255 | # your controllers). |
1256 | $c->stash->{template} = 'books/list.tt2'; |
1257 | } |
1258 | |
55490817 |
1259 | Then restart the development server and try out the C<list_recent_tcp> |
1260 | and C<list_recent> URL as we did above. It should work just the same, |
1261 | but our code is obviously cleaner and more modular, while also being |
1cde0fd6 |
1262 | more flexible at the same time. |
1263 | |
1264 | |
1265 | =head2 Adding Methods to Result Classes |
1266 | |
a46b474e |
1267 | In the previous two sections we saw a good example of how we could use |
1268 | DBIx::Class ResultSet Classes to clean up our code for an entire query |
1269 | (for example, our "canned searches" that filtered the entire query). |
1270 | We can do a similar improvement when working with individual rows as |
1271 | well. Whereas the ResultSet construct is used in DBIC to correspond |
1272 | to an entire query, the Result Class construct is used to represent a |
1273 | row. Therefore, we can add row-specific "helper methods" to our Result |
1274 | Classes stored in C<lib/MyApp/Schema/Result/>. For example, open |
3b1fa91b |
1275 | C<lib/MyApp/Schema/Result/Author.pm> and add the following method (as |
a46b474e |
1276 | always, it must be above the closing "C<1;>"): |
1cde0fd6 |
1277 | |
1278 | # |
1279 | # Helper methods |
1280 | # |
1281 | sub full_name { |
1282 | my ($self) = @_; |
fce83e5f |
1283 | |
1cde0fd6 |
1284 | return $self->first_name . ' ' . $self->last_name; |
1285 | } |
1286 | |
55490817 |
1287 | This will allow us to conveniently retrieve both the first and last |
1288 | name for an author in one shot. Now open C<root/src/books/list.tt2> |
1cde0fd6 |
1289 | and change the definition of C<tt_authors> from this: |
1290 | |
acbd7bdd |
1291 | ... |
1cde0fd6 |
1292 | [% tt_authors = [ ]; |
fce83e5f |
1293 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
acbd7bdd |
1294 | ... |
1cde0fd6 |
1295 | |
1296 | to: |
1297 | |
acbd7bdd |
1298 | ... |
1cde0fd6 |
1299 | [% tt_authors = [ ]; |
fce83e5f |
1300 | tt_authors.push(author.full_name) FOREACH author = book.authors %] |
acbd7bdd |
1301 | ... |
1cde0fd6 |
1302 | |
55490817 |
1303 | (Only C<author.last_name> was changed to C<author.full_name> -- the |
1cde0fd6 |
1304 | rest of the file should remain the same.) |
1305 | |
1306 | Now restart the development server and go to the standard book list |
1307 | URL: |
1308 | |
1309 | http://localhost:3000/books/list |
1310 | |
55490817 |
1311 | The "Author(s)" column will now contain both the first and last name. |
1312 | And, because the concatenation logic was encapsulated inside our |
444d6b27 |
1313 | Result Class, it keeps the code inside our TT template nice and clean |
55490817 |
1314 | (remember, we want the templates to be as close to pure HTML markup as |
1315 | possible). Obviously, this capability becomes even more useful as you |
444d6b27 |
1316 | use to to remove even more complicated row-specific logic from your |
1cde0fd6 |
1317 | templates! |
1318 | |
1319 | |
fce83e5f |
1320 | =head2 Moving Complicated View Code to the Model |
1321 | |
1322 | The previous section illustrated how we could use a Result Class |
1323 | method to print the full names of the authors without adding any extra |
1324 | code to our view, but it still left us with a fairly ugly mess (see |
1325 | C<root/src/books/list.tt2>): |
1326 | |
1327 | ... |
1328 | <td> |
1329 | [% # NOTE: See Chapter 4 for a better way to do this! -%] |
1330 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
1331 | [% # loop in 'side effect notation' to load just the last names of the -%] |
1332 | [% # authors into the list. Note that the 'push' TT vmethod does not print -%] |
1333 | [% # a value, so nothing will be printed here. But, if you have something -%] |
1334 | [% # in TT that does return a method and you don't want it printed, you -%] |
1335 | [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%] |
1336 | [% # call it and discard the return value. -%] |
1337 | [% tt_authors = [ ]; |
1338 | tt_authors.push(author.full_name) FOREACH author = book.authors %] |
1339 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
1340 | [% # Note the use of the TT filter "| html" to escape dangerous characters -%] |
1341 | ([% tt_authors.size | html %]) |
1342 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
1343 | [% tt_authors.join(', ') | html %] |
1344 | </td> |
1345 | ... |
1346 | |
1347 | Let's combine some of the techniques used earlier in this section to |
1348 | clean this up. First, let's add a method to our Book Result Class to |
1349 | return the number of authors for a book. Open |
1350 | C<lib/MyApp/Schema/Result/Book.pm> and add the following method: |
1351 | |
444d6b27 |
1352 | =head2 author_count |
1353 | |
1354 | Return the number of authors for the current book |
1355 | |
fce83e5f |
1356 | =cut |
1357 | |
1358 | sub author_count { |
1359 | my ($self) = @_; |
1360 | |
1361 | # Use the 'many_to_many' relationship to fetch all of the authors for the current |
1362 | # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT |
1363 | return $self->authors->count; |
1364 | } |
1365 | |
1366 | Next, let's add a method to return a list of authors for a book to the |
1367 | same C<lib/MyApp/Schema/Result/Book.pm> file: |
1368 | |
1369 | =head2 author_list |
1370 | |
1371 | Return a comma-separated list of authors for the current book |
1372 | |
1373 | =cut |
1374 | |
1375 | sub author_list { |
1376 | my ($self) = @_; |
1377 | |
1378 | # Loop through all authors for the current book, calling all the 'full_name' |
1379 | # Result Class method for each |
1380 | my @names; |
1381 | foreach my $author ($self->authors) { |
1382 | push(@names, $author->full_name); |
1383 | } |
1384 | |
1385 | return join(', ', @names); |
1386 | } |
1387 | |
1388 | This method loops through each author, using the C<full_name> Result |
1389 | Class method we added to C<lib/MyApp/Schema/Result/Author.pm> in the |
1390 | prior section. |
1391 | |
1392 | Using these two methods, we can simplify our TT code. Open |
1393 | C<root/src/books/list.tt2> and update the "Author(s)" table cell to |
1394 | match the following: |
1395 | |
1396 | ... |
1397 | <td> |
1398 | [% # Print count and author list using Result Class methods -%] |
1399 | ([% book.author_count | html %]) [% book.author_list | html %] |
1400 | </td> |
1401 | ... |
1402 | |
1403 | Although most of the code we removed comprised comments, the overall |
1404 | effect is dramatic... because our view code is so simple, we don't |
444d6b27 |
1405 | huge comments to clue people in to the gist of our code. The view |
fce83e5f |
1406 | code is now self-documenting and readable enough that you could |
1407 | probably get by with no comments at all. All of the "complex" work is |
1408 | being done in our Result Class methods (and, because we have broken |
1409 | the code into nice, modular chucks, the Result Class code is hardly |
1410 | something you would call complex). |
1411 | |
1412 | As we saw in this section, always strive to keep your view AND |
1413 | controller code as simple as possible by pulling code out into your |
1414 | model objects. Because DBIx::Class can be easily extended in so many |
1415 | ways, it's an excellent to way accomplish this objective. It will |
1416 | make your code cleaner, easier to write, less error-prone, and easier |
1417 | to debug and maintain. |
1418 | |
444d6b27 |
1419 | Before you conclude this section, fire up the development server and |
1420 | hit Refresh in your browser... the output should be the same even |
1421 | though the backend code has been trimmed down. |
1422 | |
fce83e5f |
1423 | |
d442cc9f |
1424 | =head1 AUTHOR |
1425 | |
1426 | Kennedy Clark, C<hkclark@gmail.com> |
1427 | |
1428 | Please report any errors, issues or suggestions to the author. The |
1429 | most recent version of the Catalyst Tutorial can be found at |
59884771 |
1430 | L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>. |
d442cc9f |
1431 | |
45c7830f |
1432 | Copyright 2006-2008, Kennedy Clark, under Creative Commons License |
95674086 |
1433 | (L<http://creativecommons.org/licenses/by-sa/3.0/us/>). |