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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 application |
60 | created in Chapter 3 to add basic support for Create, Read, Update, and |
61 | Delete (CRUD) of C<Book> objects. Note that the 'list' function in |
62 | Chapter 2 already implements the Read portion of CRUD (although Read |
63 | normally refers to reading a single object; you could implement full |
64 | Read functionality using the techniques introduced below). This section |
65 | will focus on the Create and Delete aspects of CRUD. More advanced |
66 | capabilities, including full Update functionality, will be addressed in |
67 | 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 can be |
72 | quick and easy. For example, see L<Catalyst::Plugin::AutoCRUD>, |
73 | L<CatalystX::CRUD>, and L<CatalystX::CRUD::YUI>. |
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74 | |
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75 | You can check out the source code for this example from the Catalyst |
76 | Subversion repository as per the instructions in |
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77 | L<Catalyst::Manual::Tutorial::01_Intro>. |
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78 | |
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79 | |
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80 | =head1 FORMLESS SUBMISSION |
81 | |
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82 | Our initial attempt at object creation will utilize the "URL arguments" |
83 | feature of Catalyst (we will employ the more common form- based |
84 | submission in the sections that follow). |
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85 | |
86 | |
87 | =head2 Include a Create Action in the Books Controller |
88 | |
89 | Edit C<lib/MyApp/Controller/Books.pm> and enter the following method: |
90 | |
91 | =head2 url_create |
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92 | |
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93 | Create a book with the supplied title, rating, and author |
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94 | |
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95 | =cut |
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96 | |
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97 | sub url_create :Local { |
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98 | # In addition to self & context, get the title, rating, & |
99 | # author_id args from the URL. Note that Catalyst automatically |
100 | # puts extra information after the "/<controller_name>/<action_name/" |
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101 | # into @_. The args are separated by the '/' char on the URL. |
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102 | my ($self, $c, $title, $rating, $author_id) = @_; |
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103 | |
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104 | # Call create() on the book model object. Pass the table |
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105 | # columns/field values we want to set as hash values |
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106 | my $book = $c->model('DB::Book')->create({ |
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107 | title => $title, |
108 | rating => $rating |
109 | }); |
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110 | |
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111 | # Add a record to the join table for this book, mapping to |
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112 | # appropriate author |
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113 | $book->add_to_book_authors({author_id => $author_id}); |
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114 | # Note: Above is a shortcut for this: |
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115 | # $book->create_related('book_authors', {author_id => $author_id}); |
116 | |
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117 | # Assign the Book object to the stash for display and set template |
118 | $c->stash(book => $book, |
119 | template => 'books/create_done.tt2'); |
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120 | } |
121 | |
122 | Notice that Catalyst takes "extra slash-separated information" from the |
123 | URL and passes it as arguments in C<@_>. The C<url_create> action then |
124 | uses a simple call to the DBIC C<create> method to add the requested |
125 | information to the database (with a separate call to |
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126 | C<add_to_book_authors> to update the join table). As do virtually all |
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127 | controller methods (at least the ones that directly handle user input), |
128 | it then sets the template that should handle this request. |
129 | |
130 | |
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131 | =head2 Include a Template for the 'url_create' Action: |
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132 | |
133 | Edit C<root/src/books/create_done.tt2> and then enter: |
134 | |
135 | [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%] |
136 | [% # Not a good idea for production use, though. :-) 'Indent=1' is -%] |
137 | [% # optional, but prevents "massive indenting" of deeply nested objects -%] |
138 | [% USE Dumper(Indent=1) -%] |
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139 | |
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140 | [% # Set the page title. META can 'go back' and set values in templates -%] |
141 | [% # that have been processed 'before' this template (here it's for -%] |
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142 | [% # root/lib/site/html and root/lib/site/header). Note that META only -%] |
143 | [% # works on simple/static strings (i.e. there is no variable -%] |
144 | [% # interpolation). -%] |
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145 | [% META title = 'Book Created' %] |
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146 | |
147 | [% # Output information about the record that was added. First title. -%] |
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148 | <p>Added book '[% book.title %]' |
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149 | |
150 | [% # Output the last name of the first author. -%] |
151 | by '[% book.authors.first.last_name %]' |
152 | |
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153 | [% # Output the rating for the book that was added -%] |
154 | with a rating of [% book.rating %].</p> |
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155 | |
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156 | [% # Provide a link back to the list page -%] |
157 | [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%] |
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158 | <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p> |
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159 | |
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160 | [% # Try out the TT Dumper (for development only!) -%] |
161 | <pre> |
162 | Dump of the 'book' variable: |
163 | [% Dumper.dump(book) %] |
164 | </pre> |
165 | |
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166 | The TT C<USE> directive allows access to a variety of plugin modules (TT |
167 | plugins, that is, not Catalyst plugins) to add extra functionality to |
168 | the base TT capabilities. Here, the plugin allows L<Data::Dumper> |
169 | "pretty printing" of objects and variables. Other than that, the rest |
170 | of the code should be familiar from the examples in Chapter 3. |
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171 | |
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172 | Note: If you are using TT v2.15 you will need to change the code that |
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173 | outputs the "last name for the first author" above to match this: |
174 | |
175 | [% authors = book.authors %] |
176 | by '[% authors.first.last_name IF authors.first; |
177 | authors.list.first.value.last_name IF ! authors.first %]' |
178 | |
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179 | to get around an issue in TT v2.15 where blessed hash objects were not |
180 | handled correctly. But, if you are still using v2.15, it's probably |
181 | time to upgrade (v2.15 is almost 4 years old). If you are following |
182 | along in Debian, then you should be on at least v2.20. You can test |
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183 | your version of Template Toolkit with the following: |
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184 | |
185 | perl -MTemplate -e 'print "$Template::VERSION\n"' |
186 | |
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187 | |
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188 | =head2 Try the 'url_create' Feature |
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189 | |
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190 | Make sure the development server is running with the "-r" restart |
191 | option: |
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192 | |
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193 | $ DBIC_TRACE=1 script/myapp_server.pl -r |
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194 | |
195 | Note that new path for C</books/url_create> appears in the startup debug |
196 | output. |
197 | |
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198 | Next, use your browser to enter the following URL: |
199 | |
200 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
201 | |
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202 | Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by |
203 | 'Stevens' with a rating of 5." along with a dump of the new book model |
204 | object as it was returned by DBIC. You should also see the following |
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205 | DBIC debug messages displayed in the development server log messages if |
206 | you have DBIC_TRACE set: |
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207 | |
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208 | INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2' |
209 | INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6' |
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210 | |
211 | The C<INSERT> statements are obviously adding the book and linking it to |
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212 | the existing record for Richard Stevens. The C<SELECT> statement |
213 | results from DBIC automatically fetching the book for the |
214 | C<Dumper.dump(book)>. |
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215 | |
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216 | If you then click the "Return to list" link, you should find that there |
217 | are now six books shown (if necessary, Shift+Reload or Ctrl+Reload your |
218 | browser at the C</books/list> page). You should now see the six DBIC |
219 | debug messages similar to the following (where N=1-6): |
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220 | |
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221 | SELECT author.id, author.first_name, author.last_name |
222 | FROM book_author me JOIN author author |
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223 | ON author.id = me.author_id WHERE ( me.book_id = ? ): 'N' |
224 | |
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225 | |
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226 | =head1 CONVERT TO A CHAINED ACTION |
227 | |
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228 | Although the example above uses the same C<Local> action type for the |
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229 | method that we saw in the previous chapter of the tutorial, there is an |
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230 | alternate approach that allows us to be more specific while also paving |
231 | the way for more advanced capabilities. Change the method declaration |
232 | for C<url_create> in C<lib/MyApp/Controller/Books.pm> you entered above |
233 | to match the following: |
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234 | |
235 | sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) { |
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236 | # In addition to self & context, get the title, rating, & |
237 | # author_id args from the URL. Note that Catalyst automatically |
238 | # puts the first 3 arguments worth of extra information after the |
239 | # "/<controller_name>/<action_name/" into @_ because we specified |
240 | # "Args(3)". The args are separated by the '/' char on the URL. |
241 | my ($self, $c, $title, $rating, $author_id) = @_; |
242 | |
243 | ... |
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244 | |
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245 | This converts the method to take advantage of the Chained |
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246 | action/dispatch type. Chaining lets you have a single URL automatically |
247 | dispatch to several controller methods, each of which can have precise |
248 | control over the number of arguments that it will receive. A chain can |
249 | essentially be thought of having three parts -- a beginning, a middle, |
250 | and an end. The bullets below summarize the key points behind each of |
251 | these parts of a chain: |
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252 | |
253 | |
254 | =over 4 |
255 | |
256 | |
257 | =item * |
258 | |
259 | Beginning |
260 | |
261 | =over 4 |
262 | |
263 | =item * |
264 | |
265 | B<Use "C<:Chained('/')>" to start a chain> |
266 | |
267 | =item * |
268 | |
269 | Get arguments through C<CaptureArgs()> |
270 | |
271 | =item * |
272 | |
273 | Specify the path to match with C<PathPart()> |
274 | |
275 | =back |
276 | |
277 | |
278 | =item * |
279 | |
280 | Middle |
281 | |
282 | =over 4 |
283 | |
284 | =item * |
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285 | |
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286 | Link to previous part of the chain with C<:Chained('_name_')> |
287 | |
288 | =item * |
289 | |
290 | Get arguments through C<CaptureArgs()> |
291 | |
292 | =item * |
293 | |
294 | Specify the path to match with C<PathPart()> |
295 | |
296 | =back |
297 | |
298 | |
299 | =item * |
300 | |
301 | End |
302 | |
303 | =over 4 |
304 | |
305 | =item * |
306 | |
307 | Link to previous part of the chain with C<:Chained('_name_')> |
308 | |
309 | =item * |
310 | |
311 | B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain> |
312 | |
313 | =item * |
314 | |
315 | Specify the path to match with C<PathPart()> |
316 | |
317 | =back |
318 | |
319 | |
320 | =back |
321 | |
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322 | In our C<url_create> method above, we have combined all three parts into |
323 | a single method: C<:Chained('/')> to start the chain, |
324 | C<:PathPart('books/url_create')> to specify the base URL to match, and |
325 | C<:Args(3)> to capture exactly three arguments and to end the chain. |
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326 | |
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327 | As we will see shortly, a chain can consist of as many "links" as you |
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328 | wish, with each part capturing some arguments and doing some work along |
329 | the way. We will continue to use the Chained action type in this |
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330 | chapter of the tutorial and explore slightly more advanced capabilities |
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331 | with the base method and delete feature below. But Chained dispatch is |
332 | capable of far more. For additional information, see |
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333 | L<Catalyst::Manual::Intro/Action types>, |
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334 | L<Catalyst::DispatchType::Chained>, and the 2006 Advent calendar entry |
335 | on the subject: L<http://www.catalystframework.org/calendar/2006/10>. |
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336 | |
337 | |
338 | =head2 Try the Chained Action |
339 | |
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340 | If you look back at the development server startup logs from your |
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341 | initial version of the C<url_create> method (the one using the C<:Local> |
342 | attribute), you will notice that it produced output similar to the |
343 | following: |
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344 | |
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345 | [debug] Loaded Path actions: |
346 | .-------------------------------------+--------------------------------------. |
347 | | Path | Private | |
348 | +-------------------------------------+--------------------------------------+ |
349 | | / | /default | |
350 | | / | /index | |
351 | | /books | /books/index | |
352 | | /books/list | /books/list | |
353 | | /books/url_create | /books/url_create | |
354 | '-------------------------------------+--------------------------------------' |
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355 | |
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356 | When the development server restarts, the debug output should change to |
357 | something along the lines of the following: |
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358 | |
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359 | [debug] Loaded Path actions: |
360 | .-------------------------------------+--------------------------------------. |
361 | | Path | Private | |
362 | +-------------------------------------+--------------------------------------+ |
363 | | / | /default | |
364 | | / | /index | |
365 | | /books | /books/index | |
366 | | /books/list | /books/list | |
367 | '-------------------------------------+--------------------------------------' |
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368 | |
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369 | [debug] Loaded Chained actions: |
370 | .-------------------------------------+--------------------------------------. |
371 | | Path Spec | Private | |
372 | +-------------------------------------+--------------------------------------+ |
373 | | /books/url_create/*/*/* | /books/url_create | |
374 | '-------------------------------------+--------------------------------------' |
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375 | |
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376 | C<url_create> has disappeared from the "Loaded Path actions" section but |
377 | it now shows up under the newly created "Loaded Chained actions" |
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378 | section. And the "/*/*/*" portion clearly shows our requirement for |
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379 | three arguments. |
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380 | |
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381 | As with our non-chained version of C<url_create>, use your browser to |
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382 | enter the following URL: |
383 | |
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384 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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385 | |
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386 | You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by |
387 | 'Stevens' with a rating of 5." along with a dump of the new book model |
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388 | object. Click the "Return to list" link, and you should find that there |
389 | are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>). |
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390 | |
391 | |
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392 | =head2 Refactor to Use a 'base' Method to Start the Chains |
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393 | |
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394 | Let's make a quick update to our initial Chained action to show a little |
395 | more of the power of chaining. First, open |
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396 | C<lib/MyApp/Controller/Books.pm> in your editor and add the following |
397 | method: |
398 | |
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399 | =head2 base |
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400 | |
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401 | Can place common logic to start chained dispatch here |
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402 | |
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403 | =cut |
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404 | |
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405 | sub base :Chained('/') :PathPart('books') :CaptureArgs(0) { |
406 | my ($self, $c) = @_; |
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407 | |
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408 | # Store the ResultSet in stash so it's available for other methods |
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409 | $c->stash(resultset => $c->model('DB::Book')); |
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410 | |
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411 | # Print a message to the debug log |
412 | $c->log->debug('*** INSIDE BASE METHOD ***'); |
413 | } |
414 | |
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415 | Here we print a log message and store the DBIC ResultSet in |
416 | C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available |
417 | for other actions that chain off C<base>. If your controller always |
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418 | needs a book ID as its first argument, you could have the base method |
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419 | capture that argument (with C<:CaptureArgs(1)>) and use it to pull the |
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420 | book object with C<-E<gt>find($id)> and leave it in the stash for later |
421 | parts of your chains to then act upon. Because we have several actions |
422 | that don't need to retrieve a book (such as the C<url_create> we are |
423 | working with now), we will instead add that functionality to a common |
424 | C<object> action shortly. |
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425 | |
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426 | As for C<url_create>, let's modify it to first dispatch to C<base>. |
427 | Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for |
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428 | C<url_create> to match the following: |
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429 | |
430 | sub url_create :Chained('base') :PathPart('url_create') :Args(3) { |
431 | |
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432 | Once you save C<lib/MyApp/Controller/Books.pm>, notice that the |
433 | development server will restart and our "Loaded Chained actions" section |
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434 | will changed slightly: |
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435 | |
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436 | [debug] Loaded Chained actions: |
437 | .-------------------------------------+--------------------------------------. |
438 | | Path Spec | Private | |
439 | +-------------------------------------+--------------------------------------+ |
440 | | /books/url_create/*/*/* | /books/base (0) | |
441 | | | => /books/url_create | |
442 | '-------------------------------------+--------------------------------------' |
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443 | |
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444 | The "Path Spec" is the same, but now it maps to two Private actions as |
445 | we would expect. The C<base> method is being triggered by the C</books> |
446 | part of the URL. However, the processing then continues to the |
447 | C<url_create> method because this method "chained" off C<base> and |
448 | specified C<:PathPart('url_create')> (note that we could have omitted |
449 | the "PathPart" here because it matches the name of the method, but we |
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450 | will include it to make the logic as explicit as possible). |
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451 | |
452 | Once again, enter the following URL into your browser: |
453 | |
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454 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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455 | |
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456 | The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a |
457 | rating of 5." message and a dump of the new book object should appear. |
458 | Also notice the extra "INSIDE BASE METHOD" debug message in the |
459 | development server output from the C<base> method. Click the "Return to |
460 | list" link, and you should find that there are now eight books shown. |
461 | (You may have a larger number of books if you repeated any of the |
462 | "create" actions more than once. Don't worry about it as long as the |
463 | number of books is appropriate for the number of times you added new |
464 | books... there should be the original five books added via |
465 | C<myapp01.sql> plus one additional book for each time you ran one of the |
466 | url_create variations above.) |
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467 | |
468 | |
469 | =head1 MANUALLY BUILDING A CREATE FORM |
470 | |
471 | Although the C<url_create> action in the previous step does begin to |
472 | reveal the power and flexibility of both Catalyst and DBIC, it's |
473 | obviously not a very realistic example of how users should be expected |
474 | to enter data. This section begins to address that concern. |
475 | |
476 | |
477 | =head2 Add Method to Display The Form |
478 | |
479 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method: |
480 | |
481 | =head2 form_create |
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482 | |
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483 | Display form to collect information for book to create |
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484 | |
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485 | =cut |
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486 | |
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487 | sub form_create :Chained('base') :PathPart('form_create') :Args(0) { |
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488 | my ($self, $c) = @_; |
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489 | |
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490 | # Set the TT template to use |
0ed3df53 |
491 | $c->stash(template => 'books/form_create.tt2'); |
d442cc9f |
492 | } |
493 | |
72609296 |
494 | This action simply invokes a view containing a form to create a book. |
d442cc9f |
495 | |
1390ef0e |
496 | |
d442cc9f |
497 | =head2 Add a Template for the Form |
498 | |
499 | Open C<root/src/books/form_create.tt2> in your editor and enter: |
500 | |
501 | [% META title = 'Manual Form Book Create' -%] |
444d6b27 |
502 | |
8a7c5151 |
503 | <form method="post" action="[% c.uri_for('form_create_do') %]"> |
d442cc9f |
504 | <table> |
505 | <tr><td>Title:</td><td><input type="text" name="title"></td></tr> |
506 | <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr> |
507 | <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr> |
508 | </table> |
509 | <input type="submit" name="Submit" value="Submit"> |
510 | </form> |
511 | |
512 | Note that we have specified the target of the form data as |
513 | C<form_create_do>, the method created in the section that follows. |
514 | |
1390ef0e |
515 | |
d442cc9f |
516 | =head2 Add a Method to Process Form Values and Update Database |
517 | |
518 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method to |
519 | save the form information to the database: |
520 | |
521 | =head2 form_create_do |
fce83e5f |
522 | |
d442cc9f |
523 | Take information from form and add to database |
fce83e5f |
524 | |
d442cc9f |
525 | =cut |
fce83e5f |
526 | |
89d3dae9 |
527 | sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) { |
d442cc9f |
528 | my ($self, $c) = @_; |
fce83e5f |
529 | |
d442cc9f |
530 | # Retrieve the values from the form |
531 | my $title = $c->request->params->{title} || 'N/A'; |
532 | my $rating = $c->request->params->{rating} || 'N/A'; |
533 | my $author_id = $c->request->params->{author_id} || '1'; |
fce83e5f |
534 | |
d442cc9f |
535 | # Create the book |
3b1fa91b |
536 | my $book = $c->model('DB::Book')->create({ |
d442cc9f |
537 | title => $title, |
538 | rating => $rating, |
539 | }); |
540 | # Handle relationship with author |
fce83e5f |
541 | $book->add_to_book_authors({author_id => $author_id}); |
542 | # Note: Above is a shortcut for this: |
543 | # $book->create_related('book_authors', {author_id => $author_id}); |
544 | |
d442cc9f |
545 | # Avoid Data::Dumper issue mentioned earlier |
55490817 |
546 | # You can probably omit this |
d442cc9f |
547 | $Data::Dumper::Useperl = 1; |
fce83e5f |
548 | |
0ed3df53 |
549 | # Store new model object in stash and set template |
550 | $c->stash(book => $book, |
551 | template => 'books/create_done.tt2'); |
d442cc9f |
552 | } |
553 | |
554 | |
555 | =head2 Test Out The Form |
556 | |
ee53cc71 |
557 | Notice that the server startup log reflects the two new chained methods |
558 | that we added: |
89d3dae9 |
559 | |
fbbb9084 |
560 | [debug] Loaded Chained actions: |
561 | .-------------------------------------+--------------------------------------. |
562 | | Path Spec | Private | |
563 | +-------------------------------------+--------------------------------------+ |
564 | | /books/form_create | /books/base (0) | |
565 | | | => /books/form_create | |
566 | | /books/form_create_do | /books/base (0) | |
567 | | | => /books/form_create_do | |
568 | | /books/url_create/*/*/* | /books/base (0) | |
569 | | | => /books/url_create | |
570 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
571 | |
d442cc9f |
572 | Point your browser to L<http://localhost:3000/books/form_create> and |
573 | enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an |
1390ef0e |
574 | author ID of 4. You should then see the output of the same |
d442cc9f |
575 | C<create_done.tt2> template seen in earlier examples. Finally, click |
576 | "Return to list" to view the full list of books. |
577 | |
578 | B<Note:> Having the user enter the primary key ID for the author is |
fce83e5f |
579 | obviously crude; we will address this concern with a drop-down list and |
580 | add validation to our forms in Chapter 9. |
d442cc9f |
581 | |
582 | |
583 | =head1 A SIMPLE DELETE FEATURE |
584 | |
72609296 |
585 | Turning our attention to the Delete portion of CRUD, this section |
d442cc9f |
586 | illustrates some basic techniques that can be used to remove information |
587 | from the database. |
588 | |
589 | |
590 | =head2 Include a Delete Link in the List |
591 | |
ee53cc71 |
592 | Edit C<root/src/books/list.tt2> and update it to match the following |
593 | (two sections have changed: 1) the additional '<th>Links</th>' table |
594 | header, and 2) the four lines for the Delete link near the bottom): |
d442cc9f |
595 | |
596 | [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%] |
597 | [% # see this "chomping" in your browser because HTML ignores blank lines, but -%] |
598 | [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%] |
599 | [%- # optional, but both the beginning and the ending TT tags support chomping. -%] |
fce83e5f |
600 | |
28c32bc6 |
601 | [% # Provide a title -%] |
d442cc9f |
602 | [% META title = 'Book List' -%] |
fce83e5f |
603 | |
d442cc9f |
604 | <table> |
605 | <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr> |
606 | [% # Display each book in a table row %] |
607 | [% FOREACH book IN books -%] |
608 | <tr> |
609 | <td>[% book.title %]</td> |
610 | <td>[% book.rating %]</td> |
611 | <td> |
fce83e5f |
612 | [% # NOTE: See "Exploring The Power of DBIC" for a better way to do this! -%] |
d442cc9f |
613 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
614 | [% # loop in 'side effect notation' to load just the last names of the -%] |
55490817 |
615 | [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%] |
d442cc9f |
616 | [% # a value, so nothing will be printed here. But, if you have something -%] |
55490817 |
617 | [% # in TT that does return a value and you don't want it printed, you can -%] |
6d97b973 |
618 | [% # 1) assign it to a bogus value, or -%] |
619 | [% # 2) use the CALL keyword to call it and discard the return value. -%] |
d442cc9f |
620 | [% tt_authors = [ ]; |
fce83e5f |
621 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
d442cc9f |
622 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
3b1fa91b |
623 | [% # Note the use of the TT filter "| html" to escape dangerous characters -%] |
624 | ([% tt_authors.size | html %]) |
d442cc9f |
625 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
3b1fa91b |
626 | [% tt_authors.join(', ') | html %] |
d442cc9f |
627 | </td> |
628 | <td> |
629 | [% # Add a link to delete a book %] |
e075db0c |
630 | <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a> |
d442cc9f |
631 | </td> |
632 | </tr> |
633 | [% END -%] |
634 | </table> |
635 | |
55490817 |
636 | The additional code is obviously designed to add a new column to the |
72609296 |
637 | right side of the table with a C<Delete> "button" (for simplicity, links |
638 | will be used instead of full HTML buttons; in practice, anything that |
fce83e5f |
639 | modifies data should be handled with a form sending a POST request). |
fe01b24f |
640 | |
ee53cc71 |
641 | Also notice that we are using a more advanced form of C<uri_for> than we |
642 | have seen before. Here we use C<$c-E<gt>controller-E<gt>action_for> to |
643 | automatically generate a URI appropriate for that action based on the |
644 | method we want to link to while inserting the C<book.id> value into the |
645 | appropriate place. Now, if you ever change C<:PathPart('delete')> in |
646 | your controller method to C<:PathPart('kill')>, then your links will |
647 | automatically update without any changes to your .tt2 template file. As |
648 | long as the name of your method does not change (here, "delete"), then |
649 | your links will still be correct. There are a few shortcuts and options |
650 | when using C<action_for()>: |
0416017e |
651 | |
652 | =over 4 |
653 | |
654 | =item * |
655 | |
ee53cc71 |
656 | If you are referring to a method in the current controller, you can use |
657 | C<$self-E<gt>action_for('_method_name_')>. |
0416017e |
658 | |
659 | =item * |
660 | |
ee53cc71 |
661 | If you are referring to a method in a different controller, you need to |
662 | include that controller's name as an argument to C<controller()>, as in |
0416017e |
663 | C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>. |
664 | |
665 | =back |
b2ad8bbd |
666 | |
55490817 |
667 | B<Note:> In practice you should B<never> use a GET request to delete a |
668 | record -- always use POST for actions that will modify data. We are |
c5d94181 |
669 | doing it here for illustrative and simplicity purposes only. |
d442cc9f |
670 | |
1390ef0e |
671 | |
994b66ad |
672 | =head2 Add a Common Method to Retrieve a Book for the Chain |
673 | |
ee53cc71 |
674 | As mentioned earlier, since we have a mixture of actions that operate on |
675 | a single book ID and others that do not, we should not have C<base> |
55490817 |
676 | capture the book ID, find the corresponding book in the database and |
677 | save it in the stash for later links in the chain. However, just |
ee53cc71 |
678 | because that logic does not belong in C<base> doesn't mean that we can't |
679 | create another location to centralize the book lookup code. In our |
680 | case, we will create a method called C<object> that will store the |
55490817 |
681 | specific book in the stash. Chains that always operate on a single |
682 | existing book can chain off this method, but methods such as |
ee53cc71 |
683 | C<url_create> that don't operate on an existing book can chain directly |
684 | off base. |
994b66ad |
685 | |
ee53cc71 |
686 | To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm> and |
687 | add the following code: |
994b66ad |
688 | |
e075db0c |
689 | =head2 object |
fce83e5f |
690 | |
e075db0c |
691 | Fetch the specified book object based on the book ID and store |
692 | it in the stash |
fce83e5f |
693 | |
e075db0c |
694 | =cut |
fce83e5f |
695 | |
994b66ad |
696 | sub object :Chained('base') :PathPart('id') :CaptureArgs(1) { |
fbbb9084 |
697 | # $id = primary key of book to delete |
994b66ad |
698 | my ($self, $c, $id) = @_; |
fce83e5f |
699 | |
994b66ad |
700 | # Find the book object and store it in the stash |
701 | $c->stash(object => $c->stash->{resultset}->find($id)); |
fce83e5f |
702 | |
994b66ad |
703 | # Make sure the lookup was successful. You would probably |
704 | # want to do something like this in a real app: |
705 | # $c->detach('/error_404') if !$c->stash->{object}; |
706 | die "Book $id not found!" if !$c->stash->{object}; |
fce83e5f |
707 | |
708 | # Print a message to the debug log |
709 | $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***"); |
994b66ad |
710 | } |
711 | |
ee53cc71 |
712 | Now, any other method that chains off C<object> will automatically have |
713 | the appropriate book waiting for it in C<$c-E<gt>stash-E<gt>{object}>. |
994b66ad |
714 | |
994b66ad |
715 | |
d442cc9f |
716 | =head2 Add a Delete Action to the Controller |
717 | |
718 | Open C<lib/MyApp/Controller/Books.pm> in your editor and add the |
719 | following method: |
720 | |
1390ef0e |
721 | =head2 delete |
fce83e5f |
722 | |
d442cc9f |
723 | Delete a book |
fce83e5f |
724 | |
d442cc9f |
725 | =cut |
fce83e5f |
726 | |
994b66ad |
727 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
994b66ad |
728 | my ($self, $c) = @_; |
fce83e5f |
729 | |
994b66ad |
730 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
731 | # with related 'book_author' entries |
994b66ad |
732 | $c->stash->{object}->delete; |
fce83e5f |
733 | |
d442cc9f |
734 | # Set a status message to be displayed at the top of the view |
735 | $c->stash->{status_msg} = "Book deleted."; |
fce83e5f |
736 | |
d442cc9f |
737 | # Forward to the list action/method in this controller |
738 | $c->forward('list'); |
739 | } |
740 | |
55490817 |
741 | This method first deletes the book object saved by the C<object> method. |
ee53cc71 |
742 | However, it also removes the corresponding entry from the C<book_author> |
743 | table with a cascading delete. |
d442cc9f |
744 | |
745 | Then, rather than forwarding to a "delete done" page as we did with the |
746 | earlier create example, it simply sets the C<status_msg> to display a |
747 | notification to the user as the normal list view is rendered. |
748 | |
749 | The C<delete> action uses the context C<forward> method to return the |
750 | user to the book list. The C<detach> method could have also been used. |
751 | Whereas C<forward> I<returns> to the original action once it is |
752 | completed, C<detach> does I<not> return. Other than that, the two are |
753 | equivalent. |
754 | |
755 | |
756 | =head2 Try the Delete Feature |
757 | |
ee53cc71 |
758 | Once you save the Books controller, the server should automatically |
759 | restart. The C<delete> method should now appear in the "Loaded Chained |
760 | actions" section of the startup debug output: |
89d3dae9 |
761 | |
fbbb9084 |
762 | [debug] Loaded Chained actions: |
994b66ad |
763 | .-------------------------------------+--------------------------------------. |
764 | | Path Spec | Private | |
765 | +-------------------------------------+--------------------------------------+ |
766 | | /books/id/*/delete | /books/base (0) | |
767 | | | -> /books/object (1) | |
768 | | | => /books/delete | |
769 | | /books/form_create | /books/base (0) | |
770 | | | => /books/form_create | |
771 | | /books/form_create_do | /books/base (0) | |
772 | | | => /books/form_create_do | |
773 | | /books/url_create/*/*/* | /books/base (0) | |
774 | | | => /books/url_create | |
775 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
776 | |
d442cc9f |
777 | Then point your browser to L<http://localhost:3000/books/list> and click |
55490817 |
778 | the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green |
779 | "Book deleted" status message should display at the top of the page, |
994b66ad |
780 | along with a list of the eight remaining books. You will also see the |
781 | cascading delete operation via the DBIC_TRACE output: |
782 | |
3b1fa91b |
783 | SELECT me.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6' |
784 | DELETE FROM book WHERE ( id = ? ): '6' |
785 | SELECT me.book_id, me.author_id FROM book_author me WHERE ( me.book_id = ? ): '6' |
786 | DELETE FROM book_author WHERE ( author_id = ? AND book_id = ? ): '4', '6' |
d442cc9f |
787 | |
788 | |
789 | =head2 Fixing a Dangerous URL |
790 | |
55490817 |
791 | Note the URL in your browser once you have performed the deletion in the |
d442cc9f |
792 | prior step -- it is still referencing the delete action: |
793 | |
acbd7bdd |
794 | http://localhost:3000/books/id/6/delete |
d442cc9f |
795 | |
55490817 |
796 | What if the user were to press reload with this URL still active? In |
ee53cc71 |
797 | this case the redundant delete is harmless (although it does generate an |
798 | exception screen, it doesn't perform any undesirable actions on the |
55490817 |
799 | application or database), but in other cases this could clearly be |
fbbb9084 |
800 | extremely dangerous. |
d442cc9f |
801 | |
802 | We can improve the logic by converting to a redirect. Unlike |
ee53cc71 |
803 | C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform a |
804 | server-side alteration in the flow of processing, a redirect is a |
805 | client-side mechanism that causes the browser to issue an entirely new |
806 | request. As a result, the URL in the browser is updated to match the |
807 | destination of the redirection URL. |
d442cc9f |
808 | |
ee53cc71 |
809 | To convert the forward used in the previous section to a redirect, open |
810 | C<lib/MyApp/Controller/Books.pm> and edit the existing C<sub delete> |
811 | method to match: |
d442cc9f |
812 | |
994b66ad |
813 | =head2 delete |
fce83e5f |
814 | |
d442cc9f |
815 | Delete a book |
fce83e5f |
816 | |
d442cc9f |
817 | =cut |
fce83e5f |
818 | |
994b66ad |
819 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
820 | my ($self, $c) = @_; |
fce83e5f |
821 | |
994b66ad |
822 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
823 | # with related 'book_author' entries |
994b66ad |
824 | $c->stash->{object}->delete; |
fce83e5f |
825 | |
d442cc9f |
826 | # Set a status message to be displayed at the top of the view |
827 | $c->stash->{status_msg} = "Book deleted."; |
fce83e5f |
828 | |
0416017e |
829 | # Redirect the user back to the list page. Note the use |
830 | # of $self->action_for as earlier in this section (BasicCRUD) |
fbbb9084 |
831 | $c->response->redirect($c->uri_for($self->action_for('list'))); |
d442cc9f |
832 | } |
833 | |
834 | |
835 | =head2 Try the Delete and Redirect Logic |
836 | |
ee53cc71 |
837 | Point your browser to L<http://localhost:3000/books/list> (don't just |
838 | hit "Refresh" in your browser since we left the URL in an invalid state |
839 | in the previous section!) and delete the first copy of the remaining two |
840 | "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return |
841 | to the L<http://localhost:3000/books/list> URL, so that is an |
842 | improvement, but notice that I<no green "Book deleted" status message is |
843 | displayed>. Because the stash is reset on every request (and a redirect |
844 | involves a second request), the C<status_msg> is cleared before it can |
f2bbfc36 |
845 | be displayed. |
d442cc9f |
846 | |
847 | |
8a472b34 |
848 | =head2 Using 'uri_for' to Pass Query Parameters |
d442cc9f |
849 | |
ee53cc71 |
850 | There are several ways to pass information across a redirect. One option |
851 | is to use the C<flash> technique that we will see in Chapter 5 of this |
852 | tutorial; however, here we will pass the information via query |
853 | parameters on the redirect itself. Open |
854 | C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete> |
89d3dae9 |
855 | method to match the following: |
d442cc9f |
856 | |
55490817 |
857 | =head2 delete |
fce83e5f |
858 | |
d442cc9f |
859 | Delete a book |
fce83e5f |
860 | |
d442cc9f |
861 | =cut |
fce83e5f |
862 | |
994b66ad |
863 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
864 | my ($self, $c) = @_; |
fce83e5f |
865 | |
994b66ad |
866 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
867 | # with related 'book_author' entries |
994b66ad |
868 | $c->stash->{object}->delete; |
fce83e5f |
869 | |
d442cc9f |
870 | # Redirect the user back to the list page with status msg as an arg |
55490817 |
871 | $c->response->redirect($c->uri_for($self->action_for('list'), |
d442cc9f |
872 | {status_msg => "Book deleted."})); |
873 | } |
874 | |
875 | This modification simply leverages the ability of C<uri_for> to include |
55490817 |
876 | an arbitrary number of name/value pairs in a hash reference. Next, we |
877 | need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a |
d442cc9f |
878 | query parameter: |
879 | |
1390ef0e |
880 | ... |
d442cc9f |
881 | <div id="content"> |
1390ef0e |
882 | [%# Status and error messages %] |
ee53cc71 |
883 | <span class="message">[% |
884 | status_msg || c.request.params.status_msg | html %]</span> |
1390ef0e |
885 | <span class="error">[% error_msg %]</span> |
886 | [%# This is where TT will stick all of your template's contents. -%] |
887 | [% content %] |
888 | </div><!-- end content --> |
889 | ... |
890 | |
ee53cc71 |
891 | Although the sample above only shows the C<content> div, leave the rest |
892 | of the file intact -- the only change we made to the C<wrapper.tt2> was |
893 | to add "C<|| c.request.params.status_msg>" to the C<E<lt>span |
894 | class="message"E<gt>> line. |
d442cc9f |
895 | |
896 | |
897 | =head2 Try the Delete and Redirect With Query Param Logic |
898 | |
ee53cc71 |
899 | Point your browser to L<http://localhost:3000/books/list> (you should |
900 | now be able to safely hit "refresh" in your browser). Then delete the |
901 | remaining copy of "TCPIP_Illustrated_Vol-2". The green "Book deleted" |
a608d8ce |
902 | status message should return. But notice that you can now hit the |
ee53cc71 |
903 | "Reload" button in your browser and it just redisplays the book list |
904 | (and it correctly shows it without the "Book deleted" message on |
905 | redisplay). |
d442cc9f |
906 | |
ee53cc71 |
907 | B<NOTE:> Another popular method for maintaining server-side information |
908 | across a redirect is to use the C<flash> technique we discuss in the |
909 | next chapter of the tutorial, |
3ab6187c |
910 | L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>. While |
ee53cc71 |
911 | C<flash> is a "slicker" mechanism in that it's all handled by the server |
912 | and doesn't "pollute" your URLs, B<it is important to note that C<flash> |
913 | can lead to situations where the wrong information shows up in the wrong |
914 | browser window if the user has multiple windows or browser tabs open>. |
915 | For example, Window A causes something to be placed in the stash, but |
916 | before that window performs a redirect, Window B makes a request to the |
917 | server and gets the status information that should really go to Window |
918 | A. For this reason, you may wish to use the "query param" technique |
919 | shown here in your applications. |
d442cc9f |
920 | |
921 | |
1cde0fd6 |
922 | =head1 EXPLORING THE POWER OF DBIC |
923 | |
ee53cc71 |
924 | In this section we will explore some additional capabilities offered by |
925 | DBIx::Class. Although these features have relatively little to do with |
926 | Catalyst per se, you will almost certainly want to take advantage of |
927 | them in your applications. |
1cde0fd6 |
928 | |
929 | |
1cde0fd6 |
930 | =head2 Add Datetime Columns to Our Existing Books Table |
931 | |
ee53cc71 |
932 | Let's add two columns to our existing C<books> table to track when each |
933 | book was added and when each book is updated: |
1cde0fd6 |
934 | |
935 | $ sqlite3 myapp.db |
33f1d5d0 |
936 | sqlite> ALTER TABLE book ADD created TIMESTAMP; |
937 | sqlite> ALTER TABLE book ADD updated TIMESTAMP; |
3b1fa91b |
938 | sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW'); |
939 | sqlite> SELECT * FROM book; |
f2bbfc36 |
940 | 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
941 | 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
942 | 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45 |
943 | 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
944 | 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
945 | 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1cde0fd6 |
946 | sqlite> .quit |
947 | $ |
948 | |
ee53cc71 |
949 | This will modify the C<books> table to include the two new fields and |
950 | populate those fields with the current time. |
1cde0fd6 |
951 | |
acbd7bdd |
952 | |
a46b474e |
953 | =head2 Update DBIx::Class to Automatically Handle the Datetime Columns |
1cde0fd6 |
954 | |
ee53cc71 |
955 | Next, we should re-run the DBIC helper to update the Result Classes with |
956 | the new fields: |
1cde0fd6 |
957 | |
958 | $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \ |
b66dd084 |
959 | create=static components=TimeStamp dbi:SQLite:myapp.db \ |
960 | on_connect_do="PRAGMA foreign_keys = ON" |
1cde0fd6 |
961 | exists "/root/dev/MyApp/script/../lib/MyApp/Model" |
962 | exists "/root/dev/MyApp/script/../t" |
963 | Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ... |
964 | Schema dump completed. |
965 | exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm" |
966 | |
ee53cc71 |
967 | Notice that we modified our use of the helper slightly: we told it to |
968 | include the L<DBIx::Class::TimeStamp> in the C<load_components> line of |
969 | the Result Classes. |
1cde0fd6 |
970 | |
ee53cc71 |
971 | If you open C<lib/MyApp/Schema/Result/Book.pm> in your editor you should |
972 | see that the C<created> and C<updated> fields are now included in the |
973 | call to C<add_columns()>. However, also notice that the C<many_to_many> |
974 | relationships we manually added below the "C<# DO NOT MODIFY...>" line |
975 | were automatically preserved. |
1cde0fd6 |
976 | |
55490817 |
977 | While we have this file open, let's update it with some additional |
ee53cc71 |
978 | information to have DBIC automatically handle the updating of these two |
979 | fields for us. Insert the following code at the bottom of the file (it |
980 | B<must> be B<below> the "C<# DO NOT MODIFY...>" line and B<above> the |
981 | C<1;> on the last line): |
1cde0fd6 |
982 | |
983 | # |
984 | # Enable automatic date handling |
985 | # |
986 | __PACKAGE__->add_columns( |
987 | "created", |
33f1d5d0 |
988 | { data_type => 'timestamp', set_on_create => 1 }, |
1cde0fd6 |
989 | "updated", |
33f1d5d0 |
990 | { data_type => 'timestamp', set_on_create => 1, set_on_update => 1 }, |
55490817 |
991 | ); |
1cde0fd6 |
992 | |
ee53cc71 |
993 | This will override the definition for these fields that Schema::Loader |
994 | placed at the top of the file. The C<set_on_create> and |
995 | C<set_on_update> options will cause DBIx::Class to automatically update |
996 | the timestamps in these columns whenever a row is created or modified. |
1cde0fd6 |
997 | |
1cde0fd6 |
998 | Then enter the following URL into your web browser: |
999 | |
1000 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
1001 | |
ee53cc71 |
1002 | You should get the same "Book Created" screen we saw above. However, if |
1003 | you now use the sqlite3 command-line tool to dump the C<books> table, |
1004 | you will see that the new book we added has an appropriate date and time |
1005 | entered for it (see the last line in the listing below): |
1cde0fd6 |
1006 | |
444d6b27 |
1007 | $ sqlite3 myapp.db "select * from book" |
f2bbfc36 |
1008 | 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1009 | 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1010 | 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1011 | 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1012 | 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1013 | 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1014 | 10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42 |
a608d8ce |
1015 | sqlite> .q |
1cde0fd6 |
1016 | |
55490817 |
1017 | Notice in the debug log that the SQL DBIC generated has changed to |
1cde0fd6 |
1018 | incorporate the datetime logic: |
1019 | |
2a6eb5f9 |
1020 | INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ): |
f2bbfc36 |
1021 | '2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42' |
2a6eb5f9 |
1022 | INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10' |
1cde0fd6 |
1023 | |
1024 | |
1025 | =head2 Create a ResultSet Class |
1026 | |
444d6b27 |
1027 | An often overlooked but extremely powerful features of DBIC is that it |
55490817 |
1028 | allows you to supply your own subclasses of C<DBIx::Class::ResultSet>. |
1029 | It allows you to pull complex and unsightly "query code" out of your |
1cde0fd6 |
1030 | controllers and encapsulate it in a method of your ResultSet Class. |
ee53cc71 |
1031 | These "canned queries" in your ResultSet Class can then be invoked via a |
1032 | single call, resulting in much cleaner and easier to read controller |
1033 | code. |
1cde0fd6 |
1034 | |
55490817 |
1035 | To illustrate the concept with a fairly simple example, let's create a |
ee53cc71 |
1036 | method that returns books added in the last 10 minutes. Start by making |
1037 | a directory where DBIx::Class will look for our ResultSet Class: |
1cde0fd6 |
1038 | |
444d6b27 |
1039 | $ mkdir lib/MyApp/Schema/ResultSet |
1cde0fd6 |
1040 | |
3b1fa91b |
1041 | Then open C<lib/MyApp/Schema/ResultSet/Book.pm> and enter the following: |
1cde0fd6 |
1042 | |
3b1fa91b |
1043 | package MyApp::Schema::ResultSet::Book; |
fce83e5f |
1044 | |
1cde0fd6 |
1045 | use strict; |
1046 | use warnings; |
1047 | use base 'DBIx::Class::ResultSet'; |
fce83e5f |
1048 | |
1cde0fd6 |
1049 | =head2 created_after |
fce83e5f |
1050 | |
1cde0fd6 |
1051 | A predefined search for recently added books |
fce83e5f |
1052 | |
1cde0fd6 |
1053 | =cut |
fce83e5f |
1054 | |
1cde0fd6 |
1055 | sub created_after { |
fadc4ae7 |
1056 | my ($self, $datetime) = @_; |
fce83e5f |
1057 | |
b66dd084 |
1058 | my $date_str = $self->result_source->schema->storage |
fadc4ae7 |
1059 | ->datetime_parser->format_datetime($datetime); |
fce83e5f |
1060 | |
fadc4ae7 |
1061 | return $self->search({ |
1062 | created => { '>' => $date_str } |
1063 | }); |
1cde0fd6 |
1064 | } |
fce83e5f |
1065 | |
1cde0fd6 |
1066 | 1; |
1067 | |
1cde0fd6 |
1068 | Then add the following method to the C<lib/MyApp/Controller/Books.pm>: |
1069 | |
1070 | =head2 list_recent |
fce83e5f |
1071 | |
1cde0fd6 |
1072 | List recently created books |
fce83e5f |
1073 | |
1cde0fd6 |
1074 | =cut |
fce83e5f |
1075 | |
1cde0fd6 |
1076 | sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) { |
1077 | my ($self, $c, $mins) = @_; |
fce83e5f |
1078 | |
1cde0fd6 |
1079 | # Retrieve all of the book records as book model objects and store in the |
1080 | # stash where they can be accessed by the TT template, but only |
1081 | # retrieve books created within the last $min number of minutes |
0ed3df53 |
1082 | $c->stash(books => [$c->model('DB::Book') |
1083 | ->created_after(DateTime->now->subtract(minutes => $mins))]); |
fce83e5f |
1084 | |
1cde0fd6 |
1085 | # Set the TT template to use. You will almost always want to do this |
1086 | # in your action methods (action methods respond to user input in |
1087 | # your controllers). |
0ed3df53 |
1088 | $c->stash(template => 'books/list.tt2'); |
1cde0fd6 |
1089 | } |
1090 | |
ee53cc71 |
1091 | Now try different values for the "minutes" argument (the final number |
1092 | value) using the URL C<http://localhost:3000/books/list_recent/_#_> in |
1093 | your browser. For example, this would list all books added in the last |
1094 | fifteen minutes: |
1cde0fd6 |
1095 | |
1096 | http://localhost:3000/books/list_recent/15 |
1097 | |
ee53cc71 |
1098 | Depending on how recently you added books, you might want to try a |
1099 | higher or lower value for the minutes. |
1cde0fd6 |
1100 | |
1101 | |
1102 | =head2 Chaining ResultSets |
1103 | |
ee53cc71 |
1104 | One of the most helpful and powerful features in DBIx::Class is that it |
1105 | allows you to "chain together" a series of queries (note that this has |
1106 | nothing to do with the "Chained Dispatch" for Catalyst that we were |
1107 | discussing above). Because each ResultSet returns another ResultSet, |
1108 | you can take an initial query and immediately feed that into a second |
1109 | query (and so on for as many queries you need). Note that no matter how |
1110 | many ResultSets you chain together, the database itself will not be hit |
1111 | until you use a method that attempts to access the data. And, because |
1112 | this technique carries over to the ResultSet Class feature we |
1113 | implemented in the previous section for our "canned search", we can |
1114 | combine the two capabilities. For example, let's add an action to our |
1115 | C<Books> controller that lists books that are both recent I<and> have |
1116 | "TCP" in the title. Open up C<lib/MyApp/Controller/Books.pm> and add |
1117 | the following method: |
1cde0fd6 |
1118 | |
acbd7bdd |
1119 | =head2 list_recent_tcp |
fce83e5f |
1120 | |
1cde0fd6 |
1121 | List recently created books |
fce83e5f |
1122 | |
1cde0fd6 |
1123 | =cut |
fce83e5f |
1124 | |
1cde0fd6 |
1125 | sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) { |
1126 | my ($self, $c, $mins) = @_; |
fce83e5f |
1127 | |
1cde0fd6 |
1128 | # Retrieve all of the book records as book model objects and store in the |
1129 | # stash where they can be accessed by the TT template, but only |
1130 | # retrieve books created within the last $min number of minutes |
1131 | # AND that have 'TCP' in the title |
0ed3df53 |
1132 | $c->stash(books => [$c->model('DB::Book') |
1cde0fd6 |
1133 | ->created_after(DateTime->now->subtract(minutes => $mins)) |
1134 | ->search({title => {'like', '%TCP%'}}) |
0ed3df53 |
1135 | ]); |
fce83e5f |
1136 | |
1cde0fd6 |
1137 | # Set the TT template to use. You will almost always want to do this |
1138 | # in your action methods (action methods respond to user input in |
1139 | # your controllers). |
0ed3df53 |
1140 | $c->stash(template => 'books/list.tt2'); |
1cde0fd6 |
1141 | } |
1142 | |
f2bbfc36 |
1143 | To try this out, enter the following URL into your browser: |
1cde0fd6 |
1144 | |
1145 | http://localhost:3000/books/list_recent_tcp/100 |
1146 | |
55490817 |
1147 | And you should get a list of books added in the last 100 minutes that |
1148 | contain the string "TCP" in the title. However, if you look at all |
ee53cc71 |
1149 | books within the last 100 minutes, you should get a longer list (again, |
1150 | you might have to adjust the number of minutes depending on how recently |
1151 | you added books to your database): |
1cde0fd6 |
1152 | |
1153 | http://localhost:3000/books/list_recent/100 |
1154 | |
55490817 |
1155 | Take a look at the DBIC_TRACE output in the development server log for |
1cde0fd6 |
1156 | the first URL and you should see something similar to the following: |
1157 | |
fce83e5f |
1158 | SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me |
f2bbfc36 |
1159 | WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32' |
1cde0fd6 |
1160 | |
ee53cc71 |
1161 | However, let's not pollute our controller code with this raw "TCP" query |
1162 | -- it would be cleaner to encapsulate that code in a method on our |
1163 | ResultSet Class. To do this, open C<lib/MyApp/Schema/ResultSet/Book.pm> |
1164 | and add the following method: |
1cde0fd6 |
1165 | |
1166 | =head2 title_like |
fce83e5f |
1167 | |
1cde0fd6 |
1168 | A predefined search for books with a 'LIKE' search in the string |
fce83e5f |
1169 | |
1cde0fd6 |
1170 | =cut |
fce83e5f |
1171 | |
1cde0fd6 |
1172 | sub title_like { |
fadc4ae7 |
1173 | my ($self, $title_str) = @_; |
fce83e5f |
1174 | |
fadc4ae7 |
1175 | return $self->search({ |
1176 | title => { 'like' => "%$title_str%" } |
1177 | }); |
1cde0fd6 |
1178 | } |
1179 | |
55490817 |
1180 | We defined the search string as C<$title_str> to make the method more |
1181 | flexible. Now update the C<list_recent_tcp> method in |
1182 | C<lib/MyApp/Controller/Books.pm> to match the following (we have |
1183 | replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line |
1cde0fd6 |
1184 | shown here -- the rest of the method should be the same): |
1185 | |
1186 | =head2 list_recent_tcp |
fce83e5f |
1187 | |
1cde0fd6 |
1188 | List recently created books |
fce83e5f |
1189 | |
1cde0fd6 |
1190 | =cut |
fce83e5f |
1191 | |
1cde0fd6 |
1192 | sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) { |
1193 | my ($self, $c, $mins) = @_; |
fce83e5f |
1194 | |
1cde0fd6 |
1195 | # Retrieve all of the book records as book model objects and store in the |
1196 | # stash where they can be accessed by the TT template, but only |
1197 | # retrieve books created within the last $min number of minutes |
1198 | # AND that have 'TCP' in the title |
0ed3df53 |
1199 | $c->stash(books => [$c->model('DB::Book') |
1cde0fd6 |
1200 | ->created_after(DateTime->now->subtract(minutes => $mins)) |
1201 | ->title_like('TCP') |
0ed3df53 |
1202 | ]); |
fce83e5f |
1203 | |
1cde0fd6 |
1204 | # Set the TT template to use. You will almost always want to do this |
1205 | # in your action methods (action methods respond to user input in |
1206 | # your controllers). |
0ed3df53 |
1207 | $c->stash(template => 'books/list.tt2'); |
1cde0fd6 |
1208 | } |
1209 | |
ee53cc71 |
1210 | Try out the C<list_recent_tcp> and C<list_recent> URLs as we did above. |
1211 | They should work just the same, but our code is obviously cleaner and |
1212 | more modular, while also being more flexible at the same time. |
1cde0fd6 |
1213 | |
1214 | |
1215 | =head2 Adding Methods to Result Classes |
1216 | |
ee53cc71 |
1217 | In the previous two sections we saw a good example of how we could use |
1218 | DBIx::Class ResultSet Classes to clean up our code for an entire query |
1219 | (for example, our "canned searches" that filtered the entire query). We |
1220 | can do a similar improvement when working with individual rows as well. |
1221 | Whereas the ResultSet construct is used in DBIC to correspond to an |
1222 | entire query, the Result Class construct is used to represent a row. |
1223 | Therefore, we can add row-specific "helper methods" to our Result |
1224 | Classes stored in C<lib/MyApp/Schema/Result/>. For example, open |
1225 | C<lib/MyApp/Schema/Result/Author.pm> and add the following method (as |
a46b474e |
1226 | always, it must be above the closing "C<1;>"): |
1cde0fd6 |
1227 | |
1228 | # |
a608d8ce |
1229 | # Row-level helper methods |
1cde0fd6 |
1230 | # |
1231 | sub full_name { |
1232 | my ($self) = @_; |
fce83e5f |
1233 | |
1cde0fd6 |
1234 | return $self->first_name . ' ' . $self->last_name; |
1235 | } |
1236 | |
ee53cc71 |
1237 | This will allow us to conveniently retrieve both the first and last name |
1238 | for an author in one shot. Now open C<root/src/books/list.tt2> and |
1239 | change the definition of C<tt_authors> from this: |
1cde0fd6 |
1240 | |
acbd7bdd |
1241 | ... |
1cde0fd6 |
1242 | [% tt_authors = [ ]; |
fce83e5f |
1243 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
acbd7bdd |
1244 | ... |
1cde0fd6 |
1245 | |
1246 | to: |
1247 | |
acbd7bdd |
1248 | ... |
1cde0fd6 |
1249 | [% tt_authors = [ ]; |
fce83e5f |
1250 | tt_authors.push(author.full_name) FOREACH author = book.authors %] |
acbd7bdd |
1251 | ... |
1cde0fd6 |
1252 | |
ee53cc71 |
1253 | (Only C<author.last_name> was changed to C<author.full_name> -- the rest |
1254 | of the file should remain the same.) |
1cde0fd6 |
1255 | |
f2bbfc36 |
1256 | Now go to the standard book list URL: |
1cde0fd6 |
1257 | |
1258 | http://localhost:3000/books/list |
1259 | |
55490817 |
1260 | The "Author(s)" column will now contain both the first and last name. |
ee53cc71 |
1261 | And, because the concatenation logic was encapsulated inside our Result |
1262 | Class, it keeps the code inside our TT template nice and clean |
55490817 |
1263 | (remember, we want the templates to be as close to pure HTML markup as |
1264 | possible). Obviously, this capability becomes even more useful as you |
0ed0d69a |
1265 | use it to remove even more complicated row-specific logic from your |
1cde0fd6 |
1266 | templates! |
1267 | |
1268 | |
fce83e5f |
1269 | =head2 Moving Complicated View Code to the Model |
1270 | |
ee53cc71 |
1271 | The previous section illustrated how we could use a Result Class method |
1272 | to print the full names of the authors without adding any extra code to |
1273 | our view, but it still left us with a fairly ugly mess (see |
fce83e5f |
1274 | C<root/src/books/list.tt2>): |
1275 | |
1276 | ... |
1277 | <td> |
1278 | [% # NOTE: See Chapter 4 for a better way to do this! -%] |
1279 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
1280 | [% # loop in 'side effect notation' to load just the last names of the -%] |
1281 | [% # authors into the list. Note that the 'push' TT vmethod does not print -%] |
1282 | [% # a value, so nothing will be printed here. But, if you have something -%] |
1283 | [% # in TT that does return a method and you don't want it printed, you -%] |
1284 | [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%] |
1285 | [% # call it and discard the return value. -%] |
1286 | [% tt_authors = [ ]; |
1287 | tt_authors.push(author.full_name) FOREACH author = book.authors %] |
1288 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
1289 | [% # Note the use of the TT filter "| html" to escape dangerous characters -%] |
1290 | ([% tt_authors.size | html %]) |
1291 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
1292 | [% tt_authors.join(', ') | html %] |
1293 | </td> |
1294 | ... |
1295 | |
ee53cc71 |
1296 | Let's combine some of the techniques used earlier in this section to |
1297 | clean this up. First, let's add a method to our Book Result Class to |
1298 | return the number of authors for a book. Open |
fce83e5f |
1299 | C<lib/MyApp/Schema/Result/Book.pm> and add the following method: |
1300 | |
444d6b27 |
1301 | =head2 author_count |
1302 | |
1303 | Return the number of authors for the current book |
1304 | |
fce83e5f |
1305 | =cut |
1306 | |
1307 | sub author_count { |
1308 | my ($self) = @_; |
1309 | |
1310 | # Use the 'many_to_many' relationship to fetch all of the authors for the current |
1311 | # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT |
1312 | return $self->authors->count; |
1313 | } |
1314 | |
1315 | Next, let's add a method to return a list of authors for a book to the |
1316 | same C<lib/MyApp/Schema/Result/Book.pm> file: |
1317 | |
1318 | =head2 author_list |
1319 | |
1320 | Return a comma-separated list of authors for the current book |
1321 | |
1322 | =cut |
1323 | |
1324 | sub author_list { |
1325 | my ($self) = @_; |
1326 | |
1327 | # Loop through all authors for the current book, calling all the 'full_name' |
1328 | # Result Class method for each |
1329 | my @names; |
1330 | foreach my $author ($self->authors) { |
1331 | push(@names, $author->full_name); |
1332 | } |
1333 | |
1334 | return join(', ', @names); |
1335 | } |
1336 | |
ee53cc71 |
1337 | This method loops through each author, using the C<full_name> Result |
1338 | Class method we added to C<lib/MyApp/Schema/Result/Author.pm> in the |
fce83e5f |
1339 | prior section. |
1340 | |
1341 | Using these two methods, we can simplify our TT code. Open |
1342 | C<root/src/books/list.tt2> and update the "Author(s)" table cell to |
1343 | match the following: |
1344 | |
1345 | ... |
1346 | <td> |
1347 | [% # Print count and author list using Result Class methods -%] |
1348 | ([% book.author_count | html %]) [% book.author_list | html %] |
1349 | </td> |
1350 | ... |
1351 | |
ee53cc71 |
1352 | Although most of the code we removed comprised comments, the overall |
1353 | effect is dramatic... because our view code is so simple, we don't need |
1354 | huge comments to clue people in to the gist of our code. The view code |
1355 | is now self-documenting and readable enough that you could probably get |
1356 | by with no comments at all. All of the "complex" work is being done in |
1357 | our Result Class methods (and, because we have broken the code into |
1358 | nice, modular chunks, the Result Class code is hardly something you |
f2bbfc36 |
1359 | would call complex). |
fce83e5f |
1360 | |
ee53cc71 |
1361 | As we saw in this section, always strive to keep your view AND |
1362 | controller code as simple as possible by pulling code out into your |
1363 | model objects. Because DBIx::Class can be easily extended in so many |
1364 | ways, it's an excellent to way accomplish this objective. It will make |
1365 | your code cleaner, easier to write, less error-prone, and easier to |
1366 | debug and maintain. |
fce83e5f |
1367 | |
ee53cc71 |
1368 | Before you conclude this section, hit Refresh in your browser... the |
1369 | output should be the same even though the backend code has been trimmed |
1370 | down. |
444d6b27 |
1371 | |
fce83e5f |
1372 | |
d442cc9f |
1373 | =head1 AUTHOR |
1374 | |
1375 | Kennedy Clark, C<hkclark@gmail.com> |
1376 | |
53243324 |
1377 | Feel free to contact the author for any errors or suggestions, but the |
1378 | best way to report issues is via the CPAN RT Bug system at |
1379 | <https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>. |
1380 | |
1381 | The most recent version of the Catalyst Tutorial can be found at |
59884771 |
1382 | L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>. |
d442cc9f |
1383 | |
ec3ef4ad |
1384 | Copyright 2006-2010, Kennedy Clark, under the |
1385 | Creative Commons Attribution Share-Alike License Version 3.0 |
95674086 |
1386 | (L<http://creativecommons.org/licenses/by-sa/3.0/us/>). |