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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 |
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 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 @_ |
104 | my ($self, $c, $title, $rating, $author_id) = @_; |
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105 | |
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 | |
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_author({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_author', {author_id => $author_id}); |
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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_author> 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 | |
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151 | [% # Output information about the record that was added. First title. -%] |
152 | <p>Added book '[% book.title %]' |
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153 | |
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154 | [% # Output the last name of the first author. This is complicated by an -%] |
155 | [% # issue in TT 2.15 where blessed hash objects are not handled right. -%] |
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156 | [% # First, fetch 'book.author' from the DB once. -%] |
157 | [% authors = book.author %] |
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158 | [% # Now use IF statements to test if 'authors.first' is "working". If so, -%] |
159 | [% # we use it. Otherwise we use a hack that seems to keep TT 2.15 happy. -%] |
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160 | by '[% authors.first.last_name IF authors.first; |
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161 | authors.list.first.value.last_name IF ! authors.first %]' |
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162 | |
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163 | [% # Output the rating for the book that was added -%] |
164 | with a rating of [% book.rating %].</p> |
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165 | |
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166 | [% # Provide a link back to the list page -%] |
167 | [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%] |
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168 | <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p> |
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169 | |
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170 | [% # Try out the TT Dumper (for development only!) -%] |
171 | <pre> |
172 | Dump of the 'book' variable: |
173 | [% Dumper.dump(book) %] |
174 | </pre> |
175 | |
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176 | The TT C<USE> directive allows access to a variety of plugin modules |
177 | (TT plugins, that is, not Catalyst plugins) to add extra functionality |
178 | to the base TT capabilities. Here, the plugin allows |
179 | L<Data::Dumper|Data::Dumper> "pretty printing" of objects and |
180 | variables. Other than that, the rest of the code should be familiar |
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181 | from the examples in Chapter 3. |
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182 | |
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183 | |
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184 | =head2 Try the 'url_create' Feature |
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185 | |
186 | If the application is still running from before, use C<Ctrl-C> to kill |
187 | it. Then restart the server: |
188 | |
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189 | $ DBIC_TRACE=1 script/myapp_server.pl |
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190 | |
191 | Note that new path for C</books/url_create> appears in the startup debug |
192 | output. |
193 | |
194 | B<TIP>: You can use C<script/myapp_server.pl -r> to have the development |
195 | server auto-detect changed files and reload itself (if your browser acts |
196 | odd, you should also try throwing in a C<-k>). If you make changes to |
197 | the TT templates only, you do not need to reload the development server |
198 | (only changes to "compiled code" such as Controller and Model C<.pm> |
199 | files require a reload). |
200 | |
201 | Next, use your browser to enter the following URL: |
202 | |
203 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
204 | |
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205 | Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by |
206 | 'Stevens' with a rating of 5." along with a dump of the new book model |
207 | object as it was returned by DBIC. You should also see the following |
208 | DBIC debug messages displayed in the development server log messages |
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209 | if you have DBIC_TRACE set: |
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210 | |
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211 | INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2' |
212 | INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6' |
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213 | |
214 | The C<INSERT> statements are obviously adding the book and linking it to |
215 | the existing record for Richard Stevens. The C<SELECT> statement results |
216 | from DBIC automatically fetching the book for the C<Dumper.dump(book)>. |
217 | |
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218 | If you then click the "Return to list" link, you should find that |
219 | there are now six books shown (if necessary, Shift+Reload or |
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220 | Ctrl+Reload your browser at the C</books/list> page). You should now see |
221 | the following six DBIC debug messages displayed for N=1-6: |
222 | |
223 | SELECT author.id, author.first_name, author.last_name \ |
224 | FROM book_author me JOIN author author \ |
225 | ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): 'N' |
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226 | |
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227 | |
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228 | =head1 CONVERT TO A CHAINED ACTION |
229 | |
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230 | Although the example above uses the same C<Local> action type for the |
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231 | method that we saw in the previous chapter of the tutorial, there is an |
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232 | alternate approach that allows us to be more specific while also |
233 | paving the way for more advanced capabilities. Change the method |
234 | declaration for C<url_create> in C<lib/MyApp/Controller/Books.pm> you |
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235 | entered above to match the following: |
236 | |
237 | sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) { |
238 | |
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239 | This converts the method to take advantage of the Chained |
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240 | action/dispatch type. Chaining lets you have a single URL |
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241 | automatically dispatch to several controller methods, each of which |
242 | can have precise control over the number of arguments that it will |
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243 | receive. A chain can essentially be thought of having three parts -- |
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244 | a beginning, a middle, and an end. The bullets below summarize the key |
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245 | points behind each of these parts of a chain: |
246 | |
247 | |
248 | =over 4 |
249 | |
250 | |
251 | =item * |
252 | |
253 | Beginning |
254 | |
255 | =over 4 |
256 | |
257 | =item * |
258 | |
259 | B<Use "C<:Chained('/')>" to start a chain> |
260 | |
261 | =item * |
262 | |
263 | Get arguments through C<CaptureArgs()> |
264 | |
265 | =item * |
266 | |
267 | Specify the path to match with C<PathPart()> |
268 | |
269 | =back |
270 | |
271 | |
272 | =item * |
273 | |
274 | Middle |
275 | |
276 | =over 4 |
277 | |
278 | =item * |
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279 | |
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280 | Link to previous part of the chain with C<:Chained('_name_')> |
281 | |
282 | =item * |
283 | |
284 | Get arguments through C<CaptureArgs()> |
285 | |
286 | =item * |
287 | |
288 | Specify the path to match with C<PathPart()> |
289 | |
290 | =back |
291 | |
292 | |
293 | =item * |
294 | |
295 | End |
296 | |
297 | =over 4 |
298 | |
299 | =item * |
300 | |
301 | Link to previous part of the chain with C<:Chained('_name_')> |
302 | |
303 | =item * |
304 | |
305 | B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain> |
306 | |
307 | =item * |
308 | |
309 | Specify the path to match with C<PathPart()> |
310 | |
311 | =back |
312 | |
313 | |
314 | =back |
315 | |
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316 | In our C<url_create> method above, we have combined all three parts into |
317 | a single method: C<:Chained('/')> to start the chain, |
318 | C<:PathPart('books/url_create')> to specify the base URL to match, and |
319 | C<:Args(3)> to capture exactly three arguments and to end the chain. |
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320 | |
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321 | As we will see shortly, a chain can consist of as many "links" as you |
322 | wish, with each part capturing some arguments and doing some work |
323 | along the way. We will continue to use the Chained action type in this |
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324 | chapter of the tutorial and explore slightly more advanced capabilities |
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325 | with the base method and delete feature below. But Chained dispatch |
326 | is capable of far more. For additional information, see |
327 | L<Catalyst::Manual::Intro/Action types>, |
328 | L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>, |
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329 | and the 2006 Advent calendar entry on the subject: |
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330 | L<http://www.catalystframework.org/calendar/2006/10>. |
331 | |
332 | |
333 | =head2 Try the Chained Action |
334 | |
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335 | If you look back at the development server startup logs from your |
336 | initial version of the C<url_create> method (the one using the |
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337 | C<:Local> attribute), you will notice that it produced output similar |
338 | to the following: |
339 | |
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340 | [debug] Loaded Path actions: |
341 | .-------------------------------------+--------------------------------------. |
342 | | Path | Private | |
343 | +-------------------------------------+--------------------------------------+ |
344 | | / | /default | |
345 | | / | /index | |
346 | | /books | /books/index | |
347 | | /books/list | /books/list | |
348 | | /books/url_create | /books/url_create | |
349 | '-------------------------------------+--------------------------------------' |
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350 | |
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351 | Now start the development server with our basic chained method in |
352 | place and the startup debug output should change to something along |
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353 | the lines of the following: |
354 | |
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355 | [debug] Loaded Path actions: |
356 | .-------------------------------------+--------------------------------------. |
357 | | Path | Private | |
358 | +-------------------------------------+--------------------------------------+ |
359 | | / | /default | |
360 | | / | /index | |
361 | | /books | /books/index | |
362 | | /books/list | /books/list | |
363 | '-------------------------------------+--------------------------------------' |
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364 | |
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365 | [debug] Loaded Chained actions: |
366 | .-------------------------------------+--------------------------------------. |
367 | | Path Spec | Private | |
368 | +-------------------------------------+--------------------------------------+ |
369 | | /books/url_create/*/*/* | /books/url_create | |
370 | '-------------------------------------+--------------------------------------' |
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371 | |
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372 | C<url_create> has disappeared form the "Loaded Path actions" section |
373 | but it now shows up under the newly created "Loaded Chained actions" |
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374 | section. And the "/*/*/*" portion clearly shows our requirement for |
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375 | three arguments. |
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376 | |
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377 | As with our non-chained version of C<url_create>, use your browser to |
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378 | enter the following URL: |
379 | |
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380 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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381 | |
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382 | You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by |
383 | 'Stevens' with a rating of 5." along with a dump of the new book model |
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384 | object. Click the "Return to list" link, and you should find that there |
385 | are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>). |
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386 | |
387 | |
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388 | =head2 Refactor to Use a 'base' Method to Start the Chains |
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389 | |
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390 | Let's make a quick update to our initial Chained action to show a |
391 | little more of the power of chaining. First, open |
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392 | C<lib/MyApp/Controller/Books.pm> in your editor and add the following |
393 | method: |
394 | |
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395 | =head2 base |
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396 | |
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397 | Can place common logic to start chained dispatch here |
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398 | |
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399 | =cut |
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400 | |
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401 | sub base :Chained('/') :PathPart('books') :CaptureArgs(0) { |
402 | my ($self, $c) = @_; |
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403 | |
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404 | # Store the ResultSet in stash so it's available for other methods |
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405 | $c->stash->{resultset} = $c->model('DB::Book'); |
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406 | |
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407 | # Print a message to the debug log |
408 | $c->log->debug('*** INSIDE BASE METHOD ***'); |
409 | } |
410 | |
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411 | Here we print a log message and store the DBIC ResultSet in |
412 | C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available |
413 | for other actions that chain off C<base>. If your controller always |
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414 | needs a book ID as its first argument, you could have the base method |
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415 | capture that argument (with C<:CaptureArgs(1)>) and use it to pull the |
416 | book object with C<-E<gt>find($id)> and leave it in the stash for |
417 | later parts of your chains to then act upon. Because we have several |
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418 | actions that don't need to retrieve a book (such as the C<url_create> |
419 | we are working with now), we will instead add that functionality |
420 | to a common C<object> action shortly. |
421 | |
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422 | As for C<url_create>, let's modify it to first dispatch to C<base>. |
423 | Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for |
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424 | C<url_create> to match the following: |
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425 | |
426 | sub url_create :Chained('base') :PathPart('url_create') :Args(3) { |
427 | |
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428 | Next, try out the refactored chain by restarting the development |
429 | server. Notice that our "Loaded Chained actions" section has changed |
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430 | slightly: |
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431 | |
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432 | [debug] Loaded Chained actions: |
433 | .-------------------------------------+--------------------------------------. |
434 | | Path Spec | Private | |
435 | +-------------------------------------+--------------------------------------+ |
436 | | /books/url_create/*/*/* | /books/base (0) | |
437 | | | => /books/url_create | |
438 | '-------------------------------------+--------------------------------------' |
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439 | |
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440 | The "Path Spec" is the same, but now it maps to two Private actions as |
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441 | we would expect. |
442 | |
443 | Once again, enter the following URL into your browser: |
444 | |
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445 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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446 | |
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447 | The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a |
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448 | rating of 5." message and a dump of the new book object should appear. |
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449 | Also notice the extra debug message in the development server output |
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450 | from the C<base> method. Click the "Return to list" link, and you |
451 | should find that there are now eight books shown. |
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452 | |
453 | |
454 | =head1 MANUALLY BUILDING A CREATE FORM |
455 | |
456 | Although the C<url_create> action in the previous step does begin to |
457 | reveal the power and flexibility of both Catalyst and DBIC, it's |
458 | obviously not a very realistic example of how users should be expected |
459 | to enter data. This section begins to address that concern. |
460 | |
461 | |
462 | =head2 Add Method to Display The Form |
463 | |
464 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method: |
465 | |
466 | =head2 form_create |
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467 | |
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468 | Display form to collect information for book to create |
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469 | |
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470 | =cut |
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471 | |
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472 | sub form_create :Chained('base') :PathPart('form_create') :Args(0) { |
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473 | my ($self, $c) = @_; |
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474 | |
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475 | # Set the TT template to use |
476 | $c->stash->{template} = 'books/form_create.tt2'; |
477 | } |
478 | |
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479 | This action simply invokes a view containing a form to create a book. |
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480 | |
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481 | |
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482 | =head2 Add a Template for the Form |
483 | |
484 | Open C<root/src/books/form_create.tt2> in your editor and enter: |
485 | |
486 | [% META title = 'Manual Form Book Create' -%] |
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487 | |
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488 | <form method="post" action="[% c.uri_for('form_create_do') %]"> |
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489 | <table> |
490 | <tr><td>Title:</td><td><input type="text" name="title"></td></tr> |
491 | <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr> |
492 | <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr> |
493 | </table> |
494 | <input type="submit" name="Submit" value="Submit"> |
495 | </form> |
496 | |
497 | Note that we have specified the target of the form data as |
498 | C<form_create_do>, the method created in the section that follows. |
499 | |
1390ef0e |
500 | |
d442cc9f |
501 | =head2 Add a Method to Process Form Values and Update Database |
502 | |
503 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method to |
504 | save the form information to the database: |
505 | |
506 | =head2 form_create_do |
55490817 |
507 | |
d442cc9f |
508 | Take information from form and add to database |
55490817 |
509 | |
d442cc9f |
510 | =cut |
55490817 |
511 | |
89d3dae9 |
512 | sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) { |
d442cc9f |
513 | my ($self, $c) = @_; |
55490817 |
514 | |
d442cc9f |
515 | # Retrieve the values from the form |
516 | my $title = $c->request->params->{title} || 'N/A'; |
517 | my $rating = $c->request->params->{rating} || 'N/A'; |
518 | my $author_id = $c->request->params->{author_id} || '1'; |
55490817 |
519 | |
d442cc9f |
520 | # Create the book |
3b1fa91b |
521 | my $book = $c->model('DB::Book')->create({ |
d442cc9f |
522 | title => $title, |
523 | rating => $rating, |
524 | }); |
525 | # Handle relationship with author |
3b1fa91b |
526 | $book->add_to_book_author({author_id => $author_id}); |
55490817 |
527 | |
d442cc9f |
528 | # Store new model object in stash |
529 | $c->stash->{book} = $book; |
55490817 |
530 | |
d442cc9f |
531 | # Avoid Data::Dumper issue mentioned earlier |
55490817 |
532 | # You can probably omit this |
d442cc9f |
533 | $Data::Dumper::Useperl = 1; |
55490817 |
534 | |
d442cc9f |
535 | # Set the TT template to use |
536 | $c->stash->{template} = 'books/create_done.tt2'; |
537 | } |
538 | |
539 | |
540 | =head2 Test Out The Form |
541 | |
542 | If the application is still running from before, use C<Ctrl-C> to kill |
543 | it. Then restart the server: |
544 | |
545 | $ script/myapp_server.pl |
546 | |
55490817 |
547 | Notice that the server startup log reflects the two new chained |
89d3dae9 |
548 | methods that we added: |
549 | |
fbbb9084 |
550 | [debug] Loaded Chained actions: |
551 | .-------------------------------------+--------------------------------------. |
552 | | Path Spec | Private | |
553 | +-------------------------------------+--------------------------------------+ |
554 | | /books/form_create | /books/base (0) | |
555 | | | => /books/form_create | |
556 | | /books/form_create_do | /books/base (0) | |
557 | | | => /books/form_create_do | |
558 | | /books/url_create/*/*/* | /books/base (0) | |
559 | | | => /books/url_create | |
560 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
561 | |
d442cc9f |
562 | Point your browser to L<http://localhost:3000/books/form_create> and |
563 | enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an |
1390ef0e |
564 | author ID of 4. You should then see the output of the same |
d442cc9f |
565 | C<create_done.tt2> template seen in earlier examples. Finally, click |
566 | "Return to list" to view the full list of books. |
567 | |
568 | B<Note:> Having the user enter the primary key ID for the author is |
569 | obviously crude; we will address this concern with a drop-down list in |
4b4d3884 |
570 | Chapter 9. |
d442cc9f |
571 | |
572 | |
573 | =head1 A SIMPLE DELETE FEATURE |
574 | |
72609296 |
575 | Turning our attention to the Delete portion of CRUD, this section |
d442cc9f |
576 | illustrates some basic techniques that can be used to remove information |
577 | from the database. |
578 | |
579 | |
580 | =head2 Include a Delete Link in the List |
581 | |
1cde0fd6 |
582 | Edit C<root/src/books/list.tt2> and update it to match the following (two |
d442cc9f |
583 | sections have changed: 1) the additional '<th>Links</th>' table header, |
72609296 |
584 | and 2) the four lines for the Delete link near the bottom): |
d442cc9f |
585 | |
586 | [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%] |
587 | [% # see this "chomping" in your browser because HTML ignores blank lines, but -%] |
588 | [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%] |
589 | [%- # optional, but both the beginning and the ending TT tags support chomping. -%] |
55490817 |
590 | |
28c32bc6 |
591 | [% # Provide a title -%] |
d442cc9f |
592 | [% META title = 'Book List' -%] |
55490817 |
593 | |
d442cc9f |
594 | <table> |
595 | <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr> |
596 | [% # Display each book in a table row %] |
597 | [% FOREACH book IN books -%] |
598 | <tr> |
599 | <td>[% book.title %]</td> |
600 | <td>[% book.rating %]</td> |
601 | <td> |
602 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
603 | [% # loop in 'side effect notation' to load just the last names of the -%] |
55490817 |
604 | [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%] |
d442cc9f |
605 | [% # a value, so nothing will be printed here. But, if you have something -%] |
55490817 |
606 | [% # in TT that does return a value and you don't want it printed, you can -%] |
3b1fa91b |
607 | [% # 1) assign it to a bogus value, or # 2) use the CALL keyword to -%] |
608 | [% # call it and discard the return value. -%] |
d442cc9f |
609 | [% tt_authors = [ ]; |
3b1fa91b |
610 | tt_authors.push(author.last_name) FOREACH author = book.author %] |
d442cc9f |
611 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
3b1fa91b |
612 | [% # Note the use of the TT filter "| html" to escape dangerous characters -%] |
613 | ([% tt_authors.size | html %]) |
d442cc9f |
614 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
3b1fa91b |
615 | [% tt_authors.join(', ') | html %] |
d442cc9f |
616 | </td> |
617 | <td> |
618 | [% # Add a link to delete a book %] |
e075db0c |
619 | <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a> |
d442cc9f |
620 | </td> |
621 | </tr> |
622 | [% END -%] |
623 | </table> |
624 | |
55490817 |
625 | The additional code is obviously designed to add a new column to the |
72609296 |
626 | right side of the table with a C<Delete> "button" (for simplicity, links |
627 | will be used instead of full HTML buttons; in practice, anything that |
628 | modifies data should be handled with a form sending a PUT request). |
fe01b24f |
629 | |
55490817 |
630 | Also notice that we are using a more advanced form of C<uri_for> than |
631 | we have seen before. Here we use |
632 | C<$c-E<gt>controller-E<gt>action_for> to automatically generate a URI |
633 | appropriate for that action based on the method we want to link to |
634 | while inserting the C<book.id> value into the appropriate place. Now, |
635 | if you ever change C<:PathPart('delete')> in your controller method to |
636 | C<:PathPart('kill')>, then your links will automatically update |
637 | without any changes to your .tt2 template file. As long as the name |
72609296 |
638 | of your method does not change (here, "delete"), then your links will |
55490817 |
639 | still be correct. There are a few shortcuts and options when using |
0416017e |
640 | C<action_for()>: |
641 | |
642 | =over 4 |
643 | |
644 | =item * |
645 | |
646 | If you are referring to a method in the current controller, you can |
647 | use C<$self-E<gt>action_for('_method_name_')>. |
648 | |
649 | =item * |
650 | |
651 | If you are referring to a method in a different controller, you need |
fbbb9084 |
652 | to include that controller's name as an argument to C<controller()>, as in |
0416017e |
653 | C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>. |
654 | |
655 | =back |
b2ad8bbd |
656 | |
55490817 |
657 | B<Note:> In practice you should B<never> use a GET request to delete a |
658 | record -- always use POST for actions that will modify data. We are |
c5d94181 |
659 | doing it here for illustrative and simplicity purposes only. |
d442cc9f |
660 | |
1390ef0e |
661 | |
994b66ad |
662 | =head2 Add a Common Method to Retrieve a Book for the Chain |
663 | |
55490817 |
664 | As mentioned earlier, since we have a mixture of actions that operate |
665 | on a single book ID and others that do not, we should not have C<base> |
666 | capture the book ID, find the corresponding book in the database and |
667 | save it in the stash for later links in the chain. However, just |
668 | because that logic does not belong in C<base> doesn't mean that we |
669 | can't create another location to centralize the book lookup code. In |
670 | our case, we will create a method called C<object> that will store the |
671 | specific book in the stash. Chains that always operate on a single |
672 | existing book can chain off this method, but methods such as |
673 | C<url_create> that don't operate on an existing book can chain |
fbbb9084 |
674 | directly off base. |
994b66ad |
675 | |
676 | To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm> |
677 | and add the following code: |
678 | |
e075db0c |
679 | =head2 object |
55490817 |
680 | |
e075db0c |
681 | Fetch the specified book object based on the book ID and store |
682 | it in the stash |
55490817 |
683 | |
e075db0c |
684 | =cut |
55490817 |
685 | |
994b66ad |
686 | sub object :Chained('base') :PathPart('id') :CaptureArgs(1) { |
fbbb9084 |
687 | # $id = primary key of book to delete |
994b66ad |
688 | my ($self, $c, $id) = @_; |
55490817 |
689 | |
994b66ad |
690 | # Find the book object and store it in the stash |
691 | $c->stash(object => $c->stash->{resultset}->find($id)); |
55490817 |
692 | |
994b66ad |
693 | # Make sure the lookup was successful. You would probably |
694 | # want to do something like this in a real app: |
695 | # $c->detach('/error_404') if !$c->stash->{object}; |
696 | die "Book $id not found!" if !$c->stash->{object}; |
697 | } |
698 | |
699 | Now, any other method that chains off C<object> will automatically |
55490817 |
700 | have the appropriate book waiting for it in |
acbd7bdd |
701 | C<$c-E<gt>stash-E<gt>{object}>. |
994b66ad |
702 | |
72609296 |
703 | Also note that we are using a different technique for setting |
704 | C<$c-E<gt>stash>. The advantage of this style is that it lets you set |
705 | multiple stash variables at a time. For example: |
994b66ad |
706 | |
707 | $c->stash(object => $c->stash->{resultset}->find($id), |
708 | another_thing => 1); |
709 | |
710 | or as a hashref: |
711 | |
712 | $c->stash({object => $c->stash->{resultset}->find($id), |
713 | another_thing => 1}); |
714 | |
fbbb9084 |
715 | Either format works, but the C<$c-E<gt>stash(name =E<gt> value);> |
72609296 |
716 | style is growing in popularity -- you may wish to use it all |
994b66ad |
717 | the time (even when you are only setting a single value). |
718 | |
719 | |
d442cc9f |
720 | =head2 Add a Delete Action to the Controller |
721 | |
722 | Open C<lib/MyApp/Controller/Books.pm> in your editor and add the |
723 | following method: |
724 | |
1390ef0e |
725 | =head2 delete |
55490817 |
726 | |
d442cc9f |
727 | Delete a book |
55490817 |
728 | |
d442cc9f |
729 | =cut |
55490817 |
730 | |
994b66ad |
731 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
994b66ad |
732 | my ($self, $c) = @_; |
55490817 |
733 | |
994b66ad |
734 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
735 | # with related 'book_author' entries |
994b66ad |
736 | $c->stash->{object}->delete; |
55490817 |
737 | |
d442cc9f |
738 | # Set a status message to be displayed at the top of the view |
739 | $c->stash->{status_msg} = "Book deleted."; |
55490817 |
740 | |
d442cc9f |
741 | # Forward to the list action/method in this controller |
742 | $c->forward('list'); |
743 | } |
744 | |
55490817 |
745 | This method first deletes the book object saved by the C<object> method. |
746 | However, it also removes the corresponding entry from the |
3b1fa91b |
747 | C<book_author> table with a cascading delete. |
d442cc9f |
748 | |
749 | Then, rather than forwarding to a "delete done" page as we did with the |
750 | earlier create example, it simply sets the C<status_msg> to display a |
751 | notification to the user as the normal list view is rendered. |
752 | |
753 | The C<delete> action uses the context C<forward> method to return the |
754 | user to the book list. The C<detach> method could have also been used. |
755 | Whereas C<forward> I<returns> to the original action once it is |
756 | completed, C<detach> does I<not> return. Other than that, the two are |
757 | equivalent. |
758 | |
759 | |
760 | =head2 Try the Delete Feature |
761 | |
762 | If the application is still running from before, use C<Ctrl-C> to kill |
763 | it. Then restart the server: |
764 | |
994b66ad |
765 | $ DBIC_TRACE=1 script/myapp_server.pl |
d442cc9f |
766 | |
89d3dae9 |
767 | The C<delete> method now appears in the "Loaded Chained actions" section |
768 | of the startup debug output: |
769 | |
fbbb9084 |
770 | [debug] Loaded Chained actions: |
994b66ad |
771 | .-------------------------------------+--------------------------------------. |
772 | | Path Spec | Private | |
773 | +-------------------------------------+--------------------------------------+ |
774 | | /books/id/*/delete | /books/base (0) | |
775 | | | -> /books/object (1) | |
776 | | | => /books/delete | |
777 | | /books/form_create | /books/base (0) | |
778 | | | => /books/form_create | |
779 | | /books/form_create_do | /books/base (0) | |
780 | | | => /books/form_create_do | |
781 | | /books/url_create/*/*/* | /books/base (0) | |
782 | | | => /books/url_create | |
783 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
784 | |
d442cc9f |
785 | Then point your browser to L<http://localhost:3000/books/list> and click |
55490817 |
786 | the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green |
787 | "Book deleted" status message should display at the top of the page, |
994b66ad |
788 | along with a list of the eight remaining books. You will also see the |
789 | cascading delete operation via the DBIC_TRACE output: |
790 | |
3b1fa91b |
791 | SELECT me.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6' |
792 | DELETE FROM book WHERE ( id = ? ): '6' |
793 | SELECT me.book_id, me.author_id FROM book_author me WHERE ( me.book_id = ? ): '6' |
794 | DELETE FROM book_author WHERE ( author_id = ? AND book_id = ? ): '4', '6' |
d442cc9f |
795 | |
796 | |
797 | =head2 Fixing a Dangerous URL |
798 | |
55490817 |
799 | Note the URL in your browser once you have performed the deletion in the |
d442cc9f |
800 | prior step -- it is still referencing the delete action: |
801 | |
acbd7bdd |
802 | http://localhost:3000/books/id/6/delete |
d442cc9f |
803 | |
55490817 |
804 | What if the user were to press reload with this URL still active? In |
805 | this case the redundant delete is harmless (although it does generate |
806 | an exception screen, it doesn't perform any undesirable actions on the |
807 | application or database), but in other cases this could clearly be |
fbbb9084 |
808 | extremely dangerous. |
d442cc9f |
809 | |
810 | We can improve the logic by converting to a redirect. Unlike |
811 | C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform |
812 | a server-side alteration in the flow of processing, a redirect is a |
3533daff |
813 | client-side mechanism that causes the browser to issue an entirely |
d442cc9f |
814 | new request. As a result, the URL in the browser is updated to match |
815 | the destination of the redirection URL. |
816 | |
817 | To convert the forward used in the previous section to a redirect, |
55490817 |
818 | open C<lib/MyApp/Controller/Books.pm> and edit the existing |
d442cc9f |
819 | C<sub delete> method to match: |
820 | |
994b66ad |
821 | =head2 delete |
55490817 |
822 | |
d442cc9f |
823 | Delete a book |
55490817 |
824 | |
d442cc9f |
825 | =cut |
55490817 |
826 | |
994b66ad |
827 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
828 | my ($self, $c) = @_; |
55490817 |
829 | |
994b66ad |
830 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
831 | # with related 'book_author' entries |
994b66ad |
832 | $c->stash->{object}->delete; |
55490817 |
833 | |
d442cc9f |
834 | # Set a status message to be displayed at the top of the view |
835 | $c->stash->{status_msg} = "Book deleted."; |
55490817 |
836 | |
0416017e |
837 | # Redirect the user back to the list page. Note the use |
838 | # of $self->action_for as earlier in this section (BasicCRUD) |
fbbb9084 |
839 | $c->response->redirect($c->uri_for($self->action_for('list'))); |
d442cc9f |
840 | } |
841 | |
842 | |
843 | =head2 Try the Delete and Redirect Logic |
844 | |
55490817 |
845 | Restart the development server and point your browser to |
846 | L<http://localhost:3000/books/list> (don't just hit "Refresh" in your |
847 | browser since we left the URL in an invalid state in the previous |
848 | section!) and delete the first copy of the remaining two |
849 | "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return |
850 | to the L<http://localhost:3000/books/list> URL, so that is an |
851 | improvement, but notice that I<no green "Book deleted" status message is |
852 | displayed>. Because the stash is reset on every request (and a redirect |
853 | involves a second request), the C<status_msg> is cleared before it can |
994b66ad |
854 | be displayed. |
d442cc9f |
855 | |
856 | |
8a472b34 |
857 | =head2 Using 'uri_for' to Pass Query Parameters |
d442cc9f |
858 | |
4b4d3884 |
859 | There are several ways to pass information across a redirect. One |
860 | option is to use the C<flash> technique that we will see in Chapter 5 |
72609296 |
861 | of this tutorial; however, here we will pass the information via query |
4b4d3884 |
862 | parameters on the redirect itself. Open |
863 | C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete> |
89d3dae9 |
864 | method to match the following: |
d442cc9f |
865 | |
55490817 |
866 | =head2 delete |
867 | |
d442cc9f |
868 | Delete a book |
55490817 |
869 | |
d442cc9f |
870 | =cut |
55490817 |
871 | |
994b66ad |
872 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
873 | my ($self, $c) = @_; |
55490817 |
874 | |
994b66ad |
875 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
876 | # with related 'book_author' entries |
994b66ad |
877 | $c->stash->{object}->delete; |
55490817 |
878 | |
d442cc9f |
879 | # Redirect the user back to the list page with status msg as an arg |
55490817 |
880 | $c->response->redirect($c->uri_for($self->action_for('list'), |
d442cc9f |
881 | {status_msg => "Book deleted."})); |
882 | } |
883 | |
884 | This modification simply leverages the ability of C<uri_for> to include |
55490817 |
885 | an arbitrary number of name/value pairs in a hash reference. Next, we |
886 | need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a |
d442cc9f |
887 | query parameter: |
888 | |
1390ef0e |
889 | ... |
d442cc9f |
890 | <div id="content"> |
1390ef0e |
891 | [%# Status and error messages %] |
892 | <span class="message">[% status_msg || c.request.params.status_msg %]</span> |
893 | <span class="error">[% error_msg %]</span> |
894 | [%# This is where TT will stick all of your template's contents. -%] |
895 | [% content %] |
896 | </div><!-- end content --> |
897 | ... |
898 | |
55490817 |
899 | Although the sample above only shows the C<content> div, leave the |
1390ef0e |
900 | rest of the file intact -- the only change we made to the C<wrapper.tt2> |
55490817 |
901 | was to add "C<|| c.request.params.status_msg>" to the |
1390ef0e |
902 | C<E<lt>span class="message"E<gt>> line. |
d442cc9f |
903 | |
904 | |
905 | =head2 Try the Delete and Redirect With Query Param Logic |
906 | |
55490817 |
907 | Restart the development server and point your browser to |
908 | L<http://localhost:3000/books/list> (you should now be able to safely |
909 | hit "refresh" in your browser). Then delete the remaining copy of |
910 | "TCPIP_Illustrated_Vol-2". The green "Book deleted" status message |
d442cc9f |
911 | should return. |
912 | |
55490817 |
913 | B<NOTE:> Another popular method for maintaining server-side |
914 | information across a redirect is to use the C<flash> technique we |
4b4d3884 |
915 | discuss in the next chapter of the tutorial, |
3ab6187c |
916 | L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>. While |
55490817 |
917 | C<flash> is a "slicker" mechanism in that it's all handled by the |
918 | server and doesn't "pollute" your URLs, B<it is important to note that |
919 | C<flash> can lead to situations where the wrong information shows up |
920 | in the wrong browser window if the user has multiple windows or |
72609296 |
921 | browser tabs open>. For example, Window A causes something to be |
55490817 |
922 | placed in the stash, but before that window performs a redirect, |
923 | Window B makes a request to the server and gets the status information |
994b66ad |
924 | that should really go to Window A. For this reason, you may wish |
89d3dae9 |
925 | to use the "query param" technique shown here in your applications. |
d442cc9f |
926 | |
927 | |
1cde0fd6 |
928 | =head1 EXPLORING THE POWER OF DBIC |
929 | |
55490817 |
930 | In this section we will explore some additional capabilities offered |
931 | by DBIx::Class. Although these features have relatively little to do |
932 | with Catalyst per se, you will almost certainly want to take advantage |
1cde0fd6 |
933 | of them in your applications. |
934 | |
935 | |
1cde0fd6 |
936 | =head2 Add Datetime Columns to Our Existing Books Table |
937 | |
55490817 |
938 | Let's add two columns to our existing C<books> table to track when |
1cde0fd6 |
939 | each book was added and when each book is updated: |
940 | |
941 | $ sqlite3 myapp.db |
3b1fa91b |
942 | sqlite> ALTER TABLE book ADD created INTEGER; |
943 | sqlite> ALTER TABLE book ADD updated INTEGER; |
944 | sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW'); |
945 | sqlite> SELECT * FROM book; |
acbd7bdd |
946 | 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
947 | 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
948 | 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35 |
949 | 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
950 | 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
951 | 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1cde0fd6 |
952 | sqlite> .quit |
953 | $ |
954 | |
955 | This will modify the C<books> table to include the two new fields |
956 | and populate those fields with the current time. |
957 | |
acbd7bdd |
958 | |
a46b474e |
959 | =head2 Update DBIx::Class to Automatically Handle the Datetime Columns |
1cde0fd6 |
960 | |
961 | Next, we should re-run the DBIC helper to update the Result Classes |
962 | with the new fields: |
963 | |
964 | $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \ |
965 | create=static components=TimeStamp dbi:SQLite:myapp.db |
966 | exists "/root/dev/MyApp/script/../lib/MyApp/Model" |
967 | exists "/root/dev/MyApp/script/../t" |
968 | Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ... |
969 | Schema dump completed. |
970 | exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm" |
971 | |
972 | Notice that we modified our use of the helper slightly: we told |
d05dbc42 |
973 | it to include the L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp> |
1cde0fd6 |
974 | in the C<load_components> line of the Result Classes. |
975 | |
3b1fa91b |
976 | If you open C<lib/MyApp/Schema/Result/Book.pm> in your editor you |
55490817 |
977 | should see that the C<created> and C<updated> fields are now included |
72609296 |
978 | in the call to C<add_columns()>, but our relationship information below |
55490817 |
979 | the "C<# DO NOT MODIFY...>" line was automatically preserved. |
1cde0fd6 |
980 | |
55490817 |
981 | While we have this file open, let's update it with some additional |
982 | information to have DBIC automatically handle the updating of these |
983 | two fields for us. Insert the following code at the bottom of the |
984 | file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and |
1cde0fd6 |
985 | B<above> the C<1;> on the last line): |
986 | |
987 | # |
988 | # Enable automatic date handling |
989 | # |
990 | __PACKAGE__->add_columns( |
991 | "created", |
992 | { data_type => 'datetime', set_on_create => 1 }, |
993 | "updated", |
994 | { data_type => 'datetime', set_on_create => 1, set_on_update => 1 }, |
55490817 |
995 | ); |
1cde0fd6 |
996 | |
a46b474e |
997 | This will override the definition for these fields that Schema::Loader |
998 | placed at the top of the file. The C<set_on_create> and |
999 | C<set_on_update> options will cause DBIx::Class to automatically |
1000 | update the timestamps in these columns whenever a row is created or |
1001 | modified. |
1cde0fd6 |
1002 | |
1003 | To test this out, restart the development server using the |
1004 | C<DBIC_TRACE=1> option: |
1005 | |
1006 | DBIC_TRACE=1 script/myapp_server.pl |
1007 | |
1008 | Then enter the following URL into your web browser: |
1009 | |
1010 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
1011 | |
1012 | You should get the same "Book Created" screen we saw above. However, |
1013 | if you now use the sqlite3 command-line tool to dump the C<books> table, |
1014 | you will see that the new book we added has an appropriate date and |
1015 | time entered for it (see the last line in the listing below): |
1016 | |
3b1fa91b |
1017 | sqlite3 myapp.db "select * from book" |
acbd7bdd |
1018 | 1|CCSP SNRS Exam Certification Guide|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1019 | 2|TCP/IP Illustrated, Volume 1|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1020 | 3|Internetworking with TCP/IP Vol.1|4|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1021 | 4|Perl Cookbook|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1022 | 5|Designing with Web Standards|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1023 | 9|TCP/IP Illustrated, Vol 3|5|2009-03-08 16:26:35|2009-03-08 16:26:35 |
1024 | 10|TCPIP_Illustrated_Vol-2|5|2009-03-08 16:29:08|2009-03-08 16:29:08 |
1cde0fd6 |
1025 | |
55490817 |
1026 | Notice in the debug log that the SQL DBIC generated has changed to |
1cde0fd6 |
1027 | incorporate the datetime logic: |
1028 | |
3b1fa91b |
1029 | INSERT INTO book (created, rating, title, updated) VALUES (?, ?, ?, ?): |
acbd7bdd |
1030 | '2009-03-08 16:29:08', '5', 'TCPIP_Illustrated_Vol-2', '2009-03-08 16:29:08' |
3b1fa91b |
1031 | INSERT INTO book_author (author_id, book_id) VALUES (?, ?): '4', '10' |
1cde0fd6 |
1032 | |
1033 | |
1034 | =head2 Create a ResultSet Class |
1035 | |
55490817 |
1036 | An often overlooked but extremely powerful features of DBIC is that it |
1037 | allows you to supply your own subclasses of C<DBIx::Class::ResultSet>. |
1038 | It allows you to pull complex and unsightly "query code" out of your |
1cde0fd6 |
1039 | controllers and encapsulate it in a method of your ResultSet Class. |
1040 | These "canned queries" in your ResultSet Class can then be invoked |
1041 | via a single call, resulting in much cleaner and easier to read |
1042 | controller code. |
1043 | |
55490817 |
1044 | To illustrate the concept with a fairly simple example, let's create a |
1cde0fd6 |
1045 | method that returns books added in the last 10 minutes. Start by |
a46b474e |
1046 | making a directory where DBIx::Class will look for our ResultSet Class: |
1cde0fd6 |
1047 | |
1048 | mkdir lib/MyApp/Schema/ResultSet |
1049 | |
3b1fa91b |
1050 | Then open C<lib/MyApp/Schema/ResultSet/Book.pm> and enter the following: |
1cde0fd6 |
1051 | |
3b1fa91b |
1052 | package MyApp::Schema::ResultSet::Book; |
55490817 |
1053 | |
1cde0fd6 |
1054 | use strict; |
1055 | use warnings; |
1056 | use base 'DBIx::Class::ResultSet'; |
55490817 |
1057 | |
1cde0fd6 |
1058 | =head2 created_after |
55490817 |
1059 | |
1cde0fd6 |
1060 | A predefined search for recently added books |
55490817 |
1061 | |
1cde0fd6 |
1062 | =cut |
55490817 |
1063 | |
1cde0fd6 |
1064 | sub created_after { |
fadc4ae7 |
1065 | my ($self, $datetime) = @_; |
55490817 |
1066 | |
fadc4ae7 |
1067 | my $date_str = $self->_source_handle->schema->storage |
1068 | ->datetime_parser->format_datetime($datetime); |
55490817 |
1069 | |
fadc4ae7 |
1070 | return $self->search({ |
1071 | created => { '>' => $date_str } |
1072 | }); |
1cde0fd6 |
1073 | } |
55490817 |
1074 | |
1cde0fd6 |
1075 | 1; |
1076 | |
55490817 |
1077 | Then we need to tell the Result Class to to treat this as a ResultSet |
3b1fa91b |
1078 | Class. Open C<lib/MyApp/Schema/Result/Book.pm> and add the following |
1cde0fd6 |
1079 | above the "C<1;>" at the bottom of the file: |
1080 | |
1081 | # |
1082 | # Set ResultSet Class |
1083 | # |
3b1fa91b |
1084 | __PACKAGE__->resultset_class('MyApp::Schema::ResultSet::Book'); |
1cde0fd6 |
1085 | |
1086 | Then add the following method to the C<lib/MyApp/Controller/Books.pm>: |
1087 | |
1088 | =head2 list_recent |
55490817 |
1089 | |
1cde0fd6 |
1090 | List recently created books |
55490817 |
1091 | |
1cde0fd6 |
1092 | =cut |
55490817 |
1093 | |
1cde0fd6 |
1094 | sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) { |
1095 | my ($self, $c, $mins) = @_; |
55490817 |
1096 | |
1cde0fd6 |
1097 | # Retrieve all of the book records as book model objects and store in the |
1098 | # stash where they can be accessed by the TT template, but only |
1099 | # retrieve books created within the last $min number of minutes |
3b1fa91b |
1100 | $c->stash->{books} = [$c->model('DB::Book') |
1cde0fd6 |
1101 | ->created_after(DateTime->now->subtract(minutes => $mins))]; |
55490817 |
1102 | |
1cde0fd6 |
1103 | # Set the TT template to use. You will almost always want to do this |
1104 | # in your action methods (action methods respond to user input in |
1105 | # your controllers). |
1106 | $c->stash->{template} = 'books/list.tt2'; |
1107 | } |
1108 | |
55490817 |
1109 | Now start the development server with C<DBIC_TRACE=1> and try |
1110 | different values for the minutes argument (the final number value) for |
1111 | the URL C<http://localhost:3000/books/list_recent/10>. For example, |
1cde0fd6 |
1112 | this would list all books added in the last fifteen minutes: |
1113 | |
1114 | http://localhost:3000/books/list_recent/15 |
1115 | |
1116 | Depending on how recently you added books, you might want to |
1117 | try a higher or lower value. |
1118 | |
1119 | |
1120 | =head2 Chaining ResultSets |
1121 | |
a46b474e |
1122 | One of the most helpful and powerful features in DBIx::Class is that |
1123 | it allows you to "chain together" a series of queries (note that this |
1124 | has nothing to do with the "Chained Dispatch" for Catalyst that we |
1125 | were discussing above). Because each ResultSet returns another |
1126 | ResultSet, you can take an initial query and immediately feed that |
1127 | into a second query (and so on for as many queries you need). Note |
1128 | that no matter how many ResultSets you chain together, the database |
1129 | itself will not be hit until you use a method that attempts to access |
1130 | the data. And, because this technique carries over to the ResultSet |
1131 | Class feature we implemented in the previous section for our "canned |
1132 | search", we can combine the two capabilities. For example, let's add |
1133 | an action to our C<Books> controller that lists books that are both |
1134 | recent I<and> have "TCP" in the title. Open up |
1135 | C<lib/MyApp/Controller/Books.pm> and add the following method: |
1cde0fd6 |
1136 | |
acbd7bdd |
1137 | =head2 list_recent_tcp |
55490817 |
1138 | |
1cde0fd6 |
1139 | List recently created books |
55490817 |
1140 | |
1cde0fd6 |
1141 | =cut |
55490817 |
1142 | |
1cde0fd6 |
1143 | sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) { |
1144 | my ($self, $c, $mins) = @_; |
55490817 |
1145 | |
1cde0fd6 |
1146 | # Retrieve all of the book records as book model objects and store in the |
1147 | # stash where they can be accessed by the TT template, but only |
1148 | # retrieve books created within the last $min number of minutes |
1149 | # AND that have 'TCP' in the title |
3b1fa91b |
1150 | $c->stash->{books} = [$c->model('DB::Book') |
1cde0fd6 |
1151 | ->created_after(DateTime->now->subtract(minutes => $mins)) |
1152 | ->search({title => {'like', '%TCP%'}}) |
1153 | ]; |
55490817 |
1154 | |
1cde0fd6 |
1155 | # Set the TT template to use. You will almost always want to do this |
1156 | # in your action methods (action methods respond to user input in |
1157 | # your controllers). |
1158 | $c->stash->{template} = 'books/list.tt2'; |
1159 | } |
1160 | |
1161 | To try this out, restart the development server with: |
1162 | |
1163 | DBIC_TRACE=1 script/myapp_server.pl |
1164 | |
1165 | And enter the following URL into your browser: |
1166 | |
1167 | http://localhost:3000/books/list_recent_tcp/100 |
1168 | |
55490817 |
1169 | And you should get a list of books added in the last 100 minutes that |
1170 | contain the string "TCP" in the title. However, if you look at all |
1171 | books within the last 100 minutes, you should get a longer list |
1172 | (again, you might have to adjust the number of minutes depending on |
1cde0fd6 |
1173 | how recently you added books to your database): |
1174 | |
1175 | http://localhost:3000/books/list_recent/100 |
1176 | |
55490817 |
1177 | Take a look at the DBIC_TRACE output in the development server log for |
1cde0fd6 |
1178 | the first URL and you should see something similar to the following: |
1179 | |
3b1fa91b |
1180 | SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me |
acbd7bdd |
1181 | WHERE ( ( ( title LIKE ? ) AND ( created > ? ) ) ): '%TCP%', '2009-03-08 14:52:54' |
1cde0fd6 |
1182 | |
55490817 |
1183 | However, let's not pollute our controller code with this raw "TCP" |
1184 | query -- it would be cleaner to encapsulate that code in a method on |
1185 | our ResultSet Class. To do this, open |
3b1fa91b |
1186 | C<lib/MyApp/Schema/ResultSet/Book.pm> and add the following method: |
1cde0fd6 |
1187 | |
1188 | =head2 title_like |
55490817 |
1189 | |
1cde0fd6 |
1190 | A predefined search for books with a 'LIKE' search in the string |
55490817 |
1191 | |
1cde0fd6 |
1192 | =cut |
55490817 |
1193 | |
1cde0fd6 |
1194 | sub title_like { |
fadc4ae7 |
1195 | my ($self, $title_str) = @_; |
55490817 |
1196 | |
fadc4ae7 |
1197 | return $self->search({ |
1198 | title => { 'like' => "%$title_str%" } |
1199 | }); |
1cde0fd6 |
1200 | } |
1201 | |
55490817 |
1202 | We defined the search string as C<$title_str> to make the method more |
1203 | flexible. Now update the C<list_recent_tcp> method in |
1204 | C<lib/MyApp/Controller/Books.pm> to match the following (we have |
1205 | replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line |
1cde0fd6 |
1206 | shown here -- the rest of the method should be the same): |
1207 | |
1208 | =head2 list_recent_tcp |
55490817 |
1209 | |
1cde0fd6 |
1210 | List recently created books |
55490817 |
1211 | |
1cde0fd6 |
1212 | =cut |
55490817 |
1213 | |
1cde0fd6 |
1214 | sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) { |
1215 | my ($self, $c, $mins) = @_; |
55490817 |
1216 | |
1cde0fd6 |
1217 | # Retrieve all of the book records as book model objects and store in the |
1218 | # stash where they can be accessed by the TT template, but only |
1219 | # retrieve books created within the last $min number of minutes |
1220 | # AND that have 'TCP' in the title |
3b1fa91b |
1221 | $c->stash->{books} = [$c->model('DB::Book') |
1cde0fd6 |
1222 | ->created_after(DateTime->now->subtract(minutes => $mins)) |
1223 | ->title_like('TCP') |
1224 | ]; |
55490817 |
1225 | |
1cde0fd6 |
1226 | # Set the TT template to use. You will almost always want to do this |
1227 | # in your action methods (action methods respond to user input in |
1228 | # your controllers). |
1229 | $c->stash->{template} = 'books/list.tt2'; |
1230 | } |
1231 | |
55490817 |
1232 | Then restart the development server and try out the C<list_recent_tcp> |
1233 | and C<list_recent> URL as we did above. It should work just the same, |
1234 | but our code is obviously cleaner and more modular, while also being |
1cde0fd6 |
1235 | more flexible at the same time. |
1236 | |
1237 | |
1238 | =head2 Adding Methods to Result Classes |
1239 | |
a46b474e |
1240 | In the previous two sections we saw a good example of how we could use |
1241 | DBIx::Class ResultSet Classes to clean up our code for an entire query |
1242 | (for example, our "canned searches" that filtered the entire query). |
1243 | We can do a similar improvement when working with individual rows as |
1244 | well. Whereas the ResultSet construct is used in DBIC to correspond |
1245 | to an entire query, the Result Class construct is used to represent a |
1246 | row. Therefore, we can add row-specific "helper methods" to our Result |
1247 | Classes stored in C<lib/MyApp/Schema/Result/>. For example, open |
3b1fa91b |
1248 | C<lib/MyApp/Schema/Result/Author.pm> and add the following method (as |
a46b474e |
1249 | always, it must be above the closing "C<1;>"): |
1cde0fd6 |
1250 | |
1251 | # |
1252 | # Helper methods |
1253 | # |
1254 | sub full_name { |
1255 | my ($self) = @_; |
55490817 |
1256 | |
1cde0fd6 |
1257 | return $self->first_name . ' ' . $self->last_name; |
1258 | } |
1259 | |
55490817 |
1260 | This will allow us to conveniently retrieve both the first and last |
1261 | name for an author in one shot. Now open C<root/src/books/list.tt2> |
1cde0fd6 |
1262 | and change the definition of C<tt_authors> from this: |
1263 | |
acbd7bdd |
1264 | ... |
1cde0fd6 |
1265 | [% tt_authors = [ ]; |
3b1fa91b |
1266 | tt_authors.push(author.last_name) FOREACH author = book.author %] |
acbd7bdd |
1267 | ... |
1cde0fd6 |
1268 | |
1269 | to: |
1270 | |
acbd7bdd |
1271 | ... |
1cde0fd6 |
1272 | [% tt_authors = [ ]; |
3b1fa91b |
1273 | tt_authors.push(author.full_name) FOREACH author = book.author %] |
acbd7bdd |
1274 | ... |
1cde0fd6 |
1275 | |
55490817 |
1276 | (Only C<author.last_name> was changed to C<author.full_name> -- the |
1cde0fd6 |
1277 | rest of the file should remain the same.) |
1278 | |
1279 | Now restart the development server and go to the standard book list |
1280 | URL: |
1281 | |
1282 | http://localhost:3000/books/list |
1283 | |
55490817 |
1284 | The "Author(s)" column will now contain both the first and last name. |
1285 | And, because the concatenation logic was encapsulated inside our |
1286 | Result Class, it keeps the code inside our .tt template nice and clean |
1287 | (remember, we want the templates to be as close to pure HTML markup as |
1288 | possible). Obviously, this capability becomes even more useful as you |
1289 | use to to remove even more complicated row-specific logic from your |
1cde0fd6 |
1290 | templates! |
1291 | |
1292 | |
d442cc9f |
1293 | =head1 AUTHOR |
1294 | |
1295 | Kennedy Clark, C<hkclark@gmail.com> |
1296 | |
1297 | Please report any errors, issues or suggestions to the author. The |
1298 | most recent version of the Catalyst Tutorial can be found at |
82ab4bbf |
1299 | L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>. |
d442cc9f |
1300 | |
45c7830f |
1301 | Copyright 2006-2008, Kennedy Clark, under Creative Commons License |
95674086 |
1302 | (L<http://creativecommons.org/licenses/by-sa/3.0/us/>). |