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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 |
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71 | of tool to automate the process. You get less control, but it can be |
72 | quick and easy. For example, see |
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73 | L<Catalyst::Plugin::AutoCRUD|Catalyst::Plugin::AutoCRUD>, |
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74 | L<CatalystX::CRUD|CatalystX::CRUD>, and |
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75 | L<CatalystX::CRUD::YUI|CatalystX::CRUD::YUI>. |
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76 | |
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77 | You can check out the source code for this example from the Catalyst |
78 | Subversion repository as per the instructions in |
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79 | L<Catalyst::Manual::Tutorial::01_Intro|Catalyst::Manual::Tutorial::01_Intro>. |
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80 | |
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81 | |
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82 | =head1 FORMLESS SUBMISSION |
83 | |
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84 | Our initial attempt at object creation will utilize the "URL |
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85 | arguments" feature of Catalyst (we will employ the more common form- |
86 | based submission in the sections that follow). |
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87 | |
88 | |
89 | =head2 Include a Create Action in the Books Controller |
90 | |
91 | Edit C<lib/MyApp/Controller/Books.pm> and enter the following method: |
92 | |
93 | =head2 url_create |
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94 | |
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95 | Create a book with the supplied title, rating, and author |
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96 | |
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97 | =cut |
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98 | |
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99 | sub url_create :Local { |
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100 | # In addition to self & context, get the title, rating, & |
101 | # author_id args from the URL. Note that Catalyst automatically |
102 | # puts extra information after the "/<controller_name>/<action_name/" |
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103 | # into @_. The args are separated by the '/' char on the URL. |
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104 | my ($self, $c, $title, $rating, $author_id) = @_; |
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105 | |
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106 | # Call create() on the book model object. Pass the table |
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107 | # columns/field values we want to set as hash values |
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108 | my $book = $c->model('DB::Book')->create({ |
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109 | title => $title, |
110 | rating => $rating |
111 | }); |
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112 | |
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113 | # Add a record to the join table for this book, mapping to |
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114 | # appropriate author |
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115 | $book->add_to_book_authors({author_id => $author_id}); |
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116 | # Note: Above is a shortcut for this: |
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117 | # $book->create_related('book_authors', {author_id => $author_id}); |
118 | |
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119 | # Assign the Book object to the stash for display in the view |
120 | $c->stash->{book} = $book; |
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121 | |
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122 | # Set the TT template to use |
123 | $c->stash->{template} = 'books/create_done.tt2'; |
124 | } |
125 | |
126 | Notice that Catalyst takes "extra slash-separated information" from the |
127 | URL and passes it as arguments in C<@_>. The C<url_create> action then |
128 | uses a simple call to the DBIC C<create> method to add the requested |
129 | information to the database (with a separate call to |
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130 | C<add_to_book_authors> to update the join table). As do virtually all |
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131 | controller methods (at least the ones that directly handle user input), |
132 | it then sets the template that should handle this request. |
133 | |
134 | |
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135 | =head2 Include a Template for the 'url_create' Action: |
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136 | |
137 | Edit C<root/src/books/create_done.tt2> and then enter: |
138 | |
139 | [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%] |
140 | [% # Not a good idea for production use, though. :-) 'Indent=1' is -%] |
141 | [% # optional, but prevents "massive indenting" of deeply nested objects -%] |
142 | [% USE Dumper(Indent=1) -%] |
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143 | |
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144 | [% # Set the page title. META can 'go back' and set values in templates -%] |
145 | [% # that have been processed 'before' this template (here it's for -%] |
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146 | [% # root/lib/site/html and root/lib/site/header). Note that META only -%] |
147 | [% # works on simple/static strings (i.e. there is no variable -%] |
148 | [% # interpolation). -%] |
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149 | [% META title = 'Book Created' %] |
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150 | |
151 | [% # Output information about the record that was added. First title. -%] |
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152 | <p>Added book '[% book.title %]' |
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153 | |
154 | [% # Output the last name of the first author. -%] |
155 | by '[% book.authors.first.last_name %]' |
156 | |
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157 | [% # Output the rating for the book that was added -%] |
158 | with a rating of [% book.rating %].</p> |
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159 | |
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160 | [% # Provide a link back to the list page -%] |
161 | [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%] |
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162 | <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p> |
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163 | |
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164 | [% # Try out the TT Dumper (for development only!) -%] |
165 | <pre> |
166 | Dump of the 'book' variable: |
167 | [% Dumper.dump(book) %] |
168 | </pre> |
169 | |
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170 | The TT C<USE> directive allows access to a variety of plugin modules |
171 | (TT plugins, that is, not Catalyst plugins) to add extra functionality |
172 | to the base TT capabilities. Here, the plugin allows |
173 | L<Data::Dumper|Data::Dumper> "pretty printing" of objects and |
174 | variables. Other than that, the rest of the code should be familiar |
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175 | from the examples in Chapter 3. |
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176 | |
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177 | Note: If you are using TT v2.15 you will need to change the code that |
178 | outputs the "last name for the first author" above to match this: |
179 | |
180 | [% authors = book.authors %] |
181 | by '[% authors.first.last_name IF authors.first; |
182 | authors.list.first.value.last_name IF ! authors.first %]' |
183 | |
184 | to get around an issue in TT v2.15 where blessed hash objects were not |
185 | handled correctly. But, if you are still using v2.15, it's probably |
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186 | time to upgrade (v2.15 is almost 4 years old). If you are following |
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187 | along in Debian, then you should be on at least v2.20. You can test |
188 | your version of Template Toolkit with the following: |
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189 | |
190 | perl -MTemplate -e 'print "$Template::VERSION\n"' |
191 | |
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192 | |
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193 | =head2 Try the 'url_create' Feature |
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194 | |
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195 | Make sure the development server is running with the "-r" restart |
196 | option: |
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197 | |
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198 | $ DBIC_TRACE=1 script/myapp_server.pl -r |
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199 | |
200 | Note that new path for C</books/url_create> appears in the startup debug |
201 | output. |
202 | |
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203 | Next, use your browser to enter the following URL: |
204 | |
205 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
206 | |
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207 | Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by |
208 | 'Stevens' with a rating of 5." along with a dump of the new book model |
209 | object as it was returned by DBIC. You should also see the following |
210 | DBIC debug messages displayed in the development server log messages |
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211 | if you have DBIC_TRACE set: |
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212 | |
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213 | INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2' |
214 | INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6' |
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215 | |
216 | The C<INSERT> statements are obviously adding the book and linking it to |
217 | the existing record for Richard Stevens. The C<SELECT> statement results |
218 | from DBIC automatically fetching the book for the C<Dumper.dump(book)>. |
219 | |
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220 | If you then click the "Return to list" link, you should find that |
221 | there are now six books shown (if necessary, Shift+Reload or |
222 | Ctrl+Reload your browser at the C</books/list> page). You should now |
223 | see the six DBIC debug messages similar to the following (where |
224 | N=1-6): |
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225 | |
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226 | SELECT author.id, author.first_name, author.last_name |
227 | FROM book_author me JOIN author author |
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228 | ON author.id = me.author_id WHERE ( me.book_id = ? ): 'N' |
229 | |
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230 | |
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231 | =head1 CONVERT TO A CHAINED ACTION |
232 | |
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233 | Although the example above uses the same C<Local> action type for the |
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234 | method that we saw in the previous chapter of the tutorial, there is an |
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235 | alternate approach that allows us to be more specific while also |
236 | paving the way for more advanced capabilities. Change the method |
237 | declaration for C<url_create> in C<lib/MyApp/Controller/Books.pm> you |
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238 | entered above to match the following: |
239 | |
240 | sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) { |
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241 | # In addition to self & context, get the title, rating, & |
242 | # author_id args from the URL. Note that Catalyst automatically |
243 | # puts the first 3 arguments worth of extra information after the |
244 | # "/<controller_name>/<action_name/" into @_ because we specified |
245 | # "Args(3)". The args are separated by the '/' char on the URL. |
246 | my ($self, $c, $title, $rating, $author_id) = @_; |
247 | |
248 | ... |
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249 | |
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250 | This converts the method to take advantage of the Chained |
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251 | action/dispatch type. Chaining lets you have a single URL |
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252 | automatically dispatch to several controller methods, each of which |
253 | can have precise control over the number of arguments that it will |
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254 | receive. A chain can essentially be thought of having three parts -- |
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255 | a beginning, a middle, and an end. The bullets below summarize the key |
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256 | points behind each of these parts of a chain: |
257 | |
258 | |
259 | =over 4 |
260 | |
261 | |
262 | =item * |
263 | |
264 | Beginning |
265 | |
266 | =over 4 |
267 | |
268 | =item * |
269 | |
270 | B<Use "C<:Chained('/')>" to start a chain> |
271 | |
272 | =item * |
273 | |
274 | Get arguments through C<CaptureArgs()> |
275 | |
276 | =item * |
277 | |
278 | Specify the path to match with C<PathPart()> |
279 | |
280 | =back |
281 | |
282 | |
283 | =item * |
284 | |
285 | Middle |
286 | |
287 | =over 4 |
288 | |
289 | =item * |
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290 | |
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291 | Link to previous part of the chain with C<:Chained('_name_')> |
292 | |
293 | =item * |
294 | |
295 | Get arguments through C<CaptureArgs()> |
296 | |
297 | =item * |
298 | |
299 | Specify the path to match with C<PathPart()> |
300 | |
301 | =back |
302 | |
303 | |
304 | =item * |
305 | |
306 | End |
307 | |
308 | =over 4 |
309 | |
310 | =item * |
311 | |
312 | Link to previous part of the chain with C<:Chained('_name_')> |
313 | |
314 | =item * |
315 | |
316 | B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain> |
317 | |
318 | =item * |
319 | |
320 | Specify the path to match with C<PathPart()> |
321 | |
322 | =back |
323 | |
324 | |
325 | =back |
326 | |
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327 | In our C<url_create> method above, we have combined all three parts into |
328 | a single method: C<:Chained('/')> to start the chain, |
329 | C<:PathPart('books/url_create')> to specify the base URL to match, and |
330 | C<:Args(3)> to capture exactly three arguments and to end the chain. |
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331 | |
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332 | As we will see shortly, a chain can consist of as many "links" as you |
333 | wish, with each part capturing some arguments and doing some work |
334 | along the way. We will continue to use the Chained action type in this |
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335 | chapter of the tutorial and explore slightly more advanced capabilities |
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336 | with the base method and delete feature below. But Chained dispatch |
337 | is capable of far more. For additional information, see |
338 | L<Catalyst::Manual::Intro/Action types>, |
339 | L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>, |
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340 | and the 2006 Advent calendar entry on the subject: |
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341 | L<http://www.catalystframework.org/calendar/2006/10>. |
342 | |
343 | |
344 | =head2 Try the Chained Action |
345 | |
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346 | If you look back at the development server startup logs from your |
347 | initial version of the C<url_create> method (the one using the |
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348 | C<:Local> attribute), you will notice that it produced output similar |
349 | to the following: |
350 | |
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351 | [debug] Loaded Path actions: |
352 | .-------------------------------------+--------------------------------------. |
353 | | Path | Private | |
354 | +-------------------------------------+--------------------------------------+ |
355 | | / | /default | |
356 | | / | /index | |
357 | | /books | /books/index | |
358 | | /books/list | /books/list | |
359 | | /books/url_create | /books/url_create | |
360 | '-------------------------------------+--------------------------------------' |
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361 | |
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362 | Now start the development server with our basic chained method in |
363 | place and the startup debug output should change to something along |
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364 | the lines of the following: |
365 | |
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366 | [debug] Loaded Path actions: |
367 | .-------------------------------------+--------------------------------------. |
368 | | Path | Private | |
369 | +-------------------------------------+--------------------------------------+ |
370 | | / | /default | |
371 | | / | /index | |
372 | | /books | /books/index | |
373 | | /books/list | /books/list | |
374 | '-------------------------------------+--------------------------------------' |
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375 | |
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376 | [debug] Loaded Chained actions: |
377 | .-------------------------------------+--------------------------------------. |
378 | | Path Spec | Private | |
379 | +-------------------------------------+--------------------------------------+ |
380 | | /books/url_create/*/*/* | /books/url_create | |
381 | '-------------------------------------+--------------------------------------' |
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382 | |
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383 | C<url_create> has disappeared form the "Loaded Path actions" section |
384 | but it now shows up under the newly created "Loaded Chained actions" |
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385 | section. And the "/*/*/*" portion clearly shows our requirement for |
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386 | three arguments. |
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387 | |
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388 | As with our non-chained version of C<url_create>, use your browser to |
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389 | enter the following URL: |
390 | |
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391 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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392 | |
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393 | You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by |
394 | 'Stevens' with a rating of 5." along with a dump of the new book model |
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395 | object. Click the "Return to list" link, and you should find that there |
396 | are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>). |
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397 | |
398 | |
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399 | =head2 Refactor to Use a 'base' Method to Start the Chains |
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400 | |
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401 | Let's make a quick update to our initial Chained action to show a |
402 | little more of the power of chaining. First, open |
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403 | C<lib/MyApp/Controller/Books.pm> in your editor and add the following |
404 | method: |
405 | |
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406 | =head2 base |
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407 | |
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408 | Can place common logic to start chained dispatch here |
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409 | |
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410 | =cut |
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411 | |
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412 | sub base :Chained('/') :PathPart('books') :CaptureArgs(0) { |
413 | my ($self, $c) = @_; |
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414 | |
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415 | # Store the ResultSet in stash so it's available for other methods |
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416 | $c->stash->{resultset} = $c->model('DB::Book'); |
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417 | |
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418 | # Print a message to the debug log |
419 | $c->log->debug('*** INSIDE BASE METHOD ***'); |
420 | } |
421 | |
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422 | Here we print a log message and store the DBIC ResultSet in |
423 | C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available |
424 | for other actions that chain off C<base>. If your controller always |
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425 | needs a book ID as its first argument, you could have the base method |
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426 | capture that argument (with C<:CaptureArgs(1)>) and use it to pull the |
427 | book object with C<-E<gt>find($id)> and leave it in the stash for |
428 | later parts of your chains to then act upon. Because we have several |
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429 | actions that don't need to retrieve a book (such as the C<url_create> |
430 | we are working with now), we will instead add that functionality |
431 | to a common C<object> action shortly. |
432 | |
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433 | As for C<url_create>, let's modify it to first dispatch to C<base>. |
434 | Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for |
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435 | C<url_create> to match the following: |
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436 | |
437 | sub url_create :Chained('base') :PathPart('url_create') :Args(3) { |
438 | |
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439 | Once you save C<lib/MyApp/Controller/Books.pm>, notice that the |
440 | development server will restart and our "Loaded Chained actions" section |
441 | will changed slightly: |
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442 | |
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443 | [debug] Loaded Chained actions: |
444 | .-------------------------------------+--------------------------------------. |
445 | | Path Spec | Private | |
446 | +-------------------------------------+--------------------------------------+ |
447 | | /books/url_create/*/*/* | /books/base (0) | |
448 | | | => /books/url_create | |
449 | '-------------------------------------+--------------------------------------' |
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450 | |
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451 | The "Path Spec" is the same, but now it maps to two Private actions as |
452 | we would expect. The C<base> method is being triggered by the |
453 | C</books> part of the URL. However, the processing then continues to |
454 | the C<url_create> method because this method "chained" off C<base> and |
455 | specified C<:PathPart('url_create')> (note that we could have omitted |
456 | the "PathPart" here because it matches the name of the method, but we |
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457 | will include it to make the logic as explicit as possible). |
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458 | |
459 | Once again, enter the following URL into your browser: |
460 | |
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461 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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462 | |
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463 | The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a |
464 | rating of 5." message and a dump of the new book object should appear. |
465 | Also notice the extra "INSIDE BASE METHOD" debug message in the |
466 | development server output from the C<base> method. Click the "Return |
467 | to list" link, and you should find that there are now eight books |
468 | shown. (You may have a larger number of books if you repeated any of |
469 | the "create" actions more than once. Don't worry about it as long as |
470 | the number of books is appropriate for the number of times you added |
471 | new books... there should be the original five books added via |
472 | C<myapp01.sql> plus one additional book for each time you ran one |
473 | of the url_create variations above.) |
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474 | |
475 | |
476 | =head1 MANUALLY BUILDING A CREATE FORM |
477 | |
478 | Although the C<url_create> action in the previous step does begin to |
479 | reveal the power and flexibility of both Catalyst and DBIC, it's |
480 | obviously not a very realistic example of how users should be expected |
481 | to enter data. This section begins to address that concern. |
482 | |
483 | |
484 | =head2 Add Method to Display The Form |
485 | |
486 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method: |
487 | |
488 | =head2 form_create |
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489 | |
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490 | Display form to collect information for book to create |
fce83e5f |
491 | |
d442cc9f |
492 | =cut |
fce83e5f |
493 | |
89d3dae9 |
494 | sub form_create :Chained('base') :PathPart('form_create') :Args(0) { |
d442cc9f |
495 | my ($self, $c) = @_; |
fce83e5f |
496 | |
d442cc9f |
497 | # Set the TT template to use |
498 | $c->stash->{template} = 'books/form_create.tt2'; |
499 | } |
500 | |
72609296 |
501 | This action simply invokes a view containing a form to create a book. |
d442cc9f |
502 | |
1390ef0e |
503 | |
d442cc9f |
504 | =head2 Add a Template for the Form |
505 | |
506 | Open C<root/src/books/form_create.tt2> in your editor and enter: |
507 | |
508 | [% META title = 'Manual Form Book Create' -%] |
444d6b27 |
509 | |
8a7c5151 |
510 | <form method="post" action="[% c.uri_for('form_create_do') %]"> |
d442cc9f |
511 | <table> |
512 | <tr><td>Title:</td><td><input type="text" name="title"></td></tr> |
513 | <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr> |
514 | <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr> |
515 | </table> |
516 | <input type="submit" name="Submit" value="Submit"> |
517 | </form> |
518 | |
519 | Note that we have specified the target of the form data as |
520 | C<form_create_do>, the method created in the section that follows. |
521 | |
1390ef0e |
522 | |
d442cc9f |
523 | =head2 Add a Method to Process Form Values and Update Database |
524 | |
525 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method to |
526 | save the form information to the database: |
527 | |
528 | =head2 form_create_do |
fce83e5f |
529 | |
d442cc9f |
530 | Take information from form and add to database |
fce83e5f |
531 | |
d442cc9f |
532 | =cut |
fce83e5f |
533 | |
89d3dae9 |
534 | sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) { |
d442cc9f |
535 | my ($self, $c) = @_; |
fce83e5f |
536 | |
d442cc9f |
537 | # Retrieve the values from the form |
538 | my $title = $c->request->params->{title} || 'N/A'; |
539 | my $rating = $c->request->params->{rating} || 'N/A'; |
540 | my $author_id = $c->request->params->{author_id} || '1'; |
fce83e5f |
541 | |
d442cc9f |
542 | # Create the book |
3b1fa91b |
543 | my $book = $c->model('DB::Book')->create({ |
d442cc9f |
544 | title => $title, |
545 | rating => $rating, |
546 | }); |
547 | # Handle relationship with author |
fce83e5f |
548 | $book->add_to_book_authors({author_id => $author_id}); |
549 | # Note: Above is a shortcut for this: |
550 | # $book->create_related('book_authors', {author_id => $author_id}); |
551 | |
d442cc9f |
552 | # Store new model object in stash |
553 | $c->stash->{book} = $book; |
fce83e5f |
554 | |
d442cc9f |
555 | # Avoid Data::Dumper issue mentioned earlier |
55490817 |
556 | # You can probably omit this |
d442cc9f |
557 | $Data::Dumper::Useperl = 1; |
fce83e5f |
558 | |
d442cc9f |
559 | # Set the TT template to use |
560 | $c->stash->{template} = 'books/create_done.tt2'; |
561 | } |
562 | |
563 | |
564 | =head2 Test Out The Form |
565 | |
55490817 |
566 | Notice that the server startup log reflects the two new chained |
89d3dae9 |
567 | methods that we added: |
568 | |
fbbb9084 |
569 | [debug] Loaded Chained actions: |
570 | .-------------------------------------+--------------------------------------. |
571 | | Path Spec | Private | |
572 | +-------------------------------------+--------------------------------------+ |
573 | | /books/form_create | /books/base (0) | |
574 | | | => /books/form_create | |
575 | | /books/form_create_do | /books/base (0) | |
576 | | | => /books/form_create_do | |
577 | | /books/url_create/*/*/* | /books/base (0) | |
578 | | | => /books/url_create | |
579 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
580 | |
d442cc9f |
581 | Point your browser to L<http://localhost:3000/books/form_create> and |
582 | enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an |
1390ef0e |
583 | author ID of 4. You should then see the output of the same |
d442cc9f |
584 | C<create_done.tt2> template seen in earlier examples. Finally, click |
585 | "Return to list" to view the full list of books. |
586 | |
587 | B<Note:> Having the user enter the primary key ID for the author is |
fce83e5f |
588 | obviously crude; we will address this concern with a drop-down list and |
589 | add validation to our forms in Chapter 9. |
d442cc9f |
590 | |
591 | |
592 | =head1 A SIMPLE DELETE FEATURE |
593 | |
72609296 |
594 | Turning our attention to the Delete portion of CRUD, this section |
d442cc9f |
595 | illustrates some basic techniques that can be used to remove information |
596 | from the database. |
597 | |
598 | |
599 | =head2 Include a Delete Link in the List |
600 | |
1cde0fd6 |
601 | Edit C<root/src/books/list.tt2> and update it to match the following (two |
d442cc9f |
602 | sections have changed: 1) the additional '<th>Links</th>' table header, |
72609296 |
603 | and 2) the four lines for the Delete link near the bottom): |
d442cc9f |
604 | |
605 | [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%] |
606 | [% # see this "chomping" in your browser because HTML ignores blank lines, but -%] |
607 | [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%] |
608 | [%- # optional, but both the beginning and the ending TT tags support chomping. -%] |
fce83e5f |
609 | |
28c32bc6 |
610 | [% # Provide a title -%] |
d442cc9f |
611 | [% META title = 'Book List' -%] |
fce83e5f |
612 | |
d442cc9f |
613 | <table> |
614 | <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr> |
615 | [% # Display each book in a table row %] |
616 | [% FOREACH book IN books -%] |
617 | <tr> |
618 | <td>[% book.title %]</td> |
619 | <td>[% book.rating %]</td> |
620 | <td> |
fce83e5f |
621 | [% # NOTE: See "Exploring The Power of DBIC" for a better way to do this! -%] |
d442cc9f |
622 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
623 | [% # loop in 'side effect notation' to load just the last names of the -%] |
55490817 |
624 | [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%] |
d442cc9f |
625 | [% # a value, so nothing will be printed here. But, if you have something -%] |
55490817 |
626 | [% # in TT that does return a value and you don't want it printed, you can -%] |
6d97b973 |
627 | [% # 1) assign it to a bogus value, or -%] |
628 | [% # 2) use the CALL keyword to call it and discard the return value. -%] |
d442cc9f |
629 | [% tt_authors = [ ]; |
fce83e5f |
630 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
d442cc9f |
631 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
3b1fa91b |
632 | [% # Note the use of the TT filter "| html" to escape dangerous characters -%] |
633 | ([% tt_authors.size | html %]) |
d442cc9f |
634 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
3b1fa91b |
635 | [% tt_authors.join(', ') | html %] |
d442cc9f |
636 | </td> |
637 | <td> |
638 | [% # Add a link to delete a book %] |
e075db0c |
639 | <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a> |
d442cc9f |
640 | </td> |
641 | </tr> |
642 | [% END -%] |
643 | </table> |
644 | |
55490817 |
645 | The additional code is obviously designed to add a new column to the |
72609296 |
646 | right side of the table with a C<Delete> "button" (for simplicity, links |
647 | will be used instead of full HTML buttons; in practice, anything that |
fce83e5f |
648 | modifies data should be handled with a form sending a POST request). |
fe01b24f |
649 | |
55490817 |
650 | Also notice that we are using a more advanced form of C<uri_for> than |
651 | we have seen before. Here we use |
652 | C<$c-E<gt>controller-E<gt>action_for> to automatically generate a URI |
653 | appropriate for that action based on the method we want to link to |
654 | while inserting the C<book.id> value into the appropriate place. Now, |
655 | if you ever change C<:PathPart('delete')> in your controller method to |
656 | C<:PathPart('kill')>, then your links will automatically update |
657 | without any changes to your .tt2 template file. As long as the name |
72609296 |
658 | of your method does not change (here, "delete"), then your links will |
55490817 |
659 | still be correct. There are a few shortcuts and options when using |
0416017e |
660 | C<action_for()>: |
661 | |
662 | =over 4 |
663 | |
664 | =item * |
665 | |
666 | If you are referring to a method in the current controller, you can |
667 | use C<$self-E<gt>action_for('_method_name_')>. |
668 | |
669 | =item * |
670 | |
671 | If you are referring to a method in a different controller, you need |
fbbb9084 |
672 | to include that controller's name as an argument to C<controller()>, as in |
0416017e |
673 | C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>. |
674 | |
675 | =back |
b2ad8bbd |
676 | |
55490817 |
677 | B<Note:> In practice you should B<never> use a GET request to delete a |
678 | record -- always use POST for actions that will modify data. We are |
c5d94181 |
679 | doing it here for illustrative and simplicity purposes only. |
d442cc9f |
680 | |
1390ef0e |
681 | |
994b66ad |
682 | =head2 Add a Common Method to Retrieve a Book for the Chain |
683 | |
55490817 |
684 | As mentioned earlier, since we have a mixture of actions that operate |
685 | on a single book ID and others that do not, we should not have C<base> |
686 | capture the book ID, find the corresponding book in the database and |
687 | save it in the stash for later links in the chain. However, just |
688 | because that logic does not belong in C<base> doesn't mean that we |
689 | can't create another location to centralize the book lookup code. In |
690 | our case, we will create a method called C<object> that will store the |
691 | specific book in the stash. Chains that always operate on a single |
692 | existing book can chain off this method, but methods such as |
693 | C<url_create> that don't operate on an existing book can chain |
fbbb9084 |
694 | directly off base. |
994b66ad |
695 | |
696 | To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm> |
697 | and add the following code: |
698 | |
e075db0c |
699 | =head2 object |
fce83e5f |
700 | |
e075db0c |
701 | Fetch the specified book object based on the book ID and store |
702 | it in the stash |
fce83e5f |
703 | |
e075db0c |
704 | =cut |
fce83e5f |
705 | |
994b66ad |
706 | sub object :Chained('base') :PathPart('id') :CaptureArgs(1) { |
fbbb9084 |
707 | # $id = primary key of book to delete |
994b66ad |
708 | my ($self, $c, $id) = @_; |
fce83e5f |
709 | |
994b66ad |
710 | # Find the book object and store it in the stash |
711 | $c->stash(object => $c->stash->{resultset}->find($id)); |
fce83e5f |
712 | |
994b66ad |
713 | # Make sure the lookup was successful. You would probably |
714 | # want to do something like this in a real app: |
715 | # $c->detach('/error_404') if !$c->stash->{object}; |
716 | die "Book $id not found!" if !$c->stash->{object}; |
fce83e5f |
717 | |
718 | # Print a message to the debug log |
719 | $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***"); |
994b66ad |
720 | } |
721 | |
722 | Now, any other method that chains off C<object> will automatically |
55490817 |
723 | have the appropriate book waiting for it in |
acbd7bdd |
724 | C<$c-E<gt>stash-E<gt>{object}>. |
994b66ad |
725 | |
994b66ad |
726 | |
d442cc9f |
727 | =head2 Add a Delete Action to the Controller |
728 | |
729 | Open C<lib/MyApp/Controller/Books.pm> in your editor and add the |
730 | following method: |
731 | |
1390ef0e |
732 | =head2 delete |
fce83e5f |
733 | |
d442cc9f |
734 | Delete a book |
fce83e5f |
735 | |
d442cc9f |
736 | =cut |
fce83e5f |
737 | |
994b66ad |
738 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
994b66ad |
739 | my ($self, $c) = @_; |
fce83e5f |
740 | |
994b66ad |
741 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
742 | # with related 'book_author' entries |
994b66ad |
743 | $c->stash->{object}->delete; |
fce83e5f |
744 | |
d442cc9f |
745 | # Set a status message to be displayed at the top of the view |
746 | $c->stash->{status_msg} = "Book deleted."; |
fce83e5f |
747 | |
d442cc9f |
748 | # Forward to the list action/method in this controller |
749 | $c->forward('list'); |
750 | } |
751 | |
55490817 |
752 | This method first deletes the book object saved by the C<object> method. |
753 | However, it also removes the corresponding entry from the |
3b1fa91b |
754 | C<book_author> table with a cascading delete. |
d442cc9f |
755 | |
756 | Then, rather than forwarding to a "delete done" page as we did with the |
757 | earlier create example, it simply sets the C<status_msg> to display a |
758 | notification to the user as the normal list view is rendered. |
759 | |
760 | The C<delete> action uses the context C<forward> method to return the |
761 | user to the book list. The C<detach> method could have also been used. |
762 | Whereas C<forward> I<returns> to the original action once it is |
763 | completed, C<detach> does I<not> return. Other than that, the two are |
764 | equivalent. |
765 | |
766 | |
767 | =head2 Try the Delete Feature |
768 | |
f2bbfc36 |
769 | One you save the Books controller, the server should automatically restart. |
770 | The C<delete> method should now appear in the "Loaded Chained actions" section |
89d3dae9 |
771 | of the startup debug output: |
772 | |
fbbb9084 |
773 | [debug] Loaded Chained actions: |
994b66ad |
774 | .-------------------------------------+--------------------------------------. |
775 | | Path Spec | Private | |
776 | +-------------------------------------+--------------------------------------+ |
777 | | /books/id/*/delete | /books/base (0) | |
778 | | | -> /books/object (1) | |
779 | | | => /books/delete | |
780 | | /books/form_create | /books/base (0) | |
781 | | | => /books/form_create | |
782 | | /books/form_create_do | /books/base (0) | |
783 | | | => /books/form_create_do | |
784 | | /books/url_create/*/*/* | /books/base (0) | |
785 | | | => /books/url_create | |
786 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
787 | |
d442cc9f |
788 | Then point your browser to L<http://localhost:3000/books/list> and click |
55490817 |
789 | the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green |
790 | "Book deleted" status message should display at the top of the page, |
994b66ad |
791 | along with a list of the eight remaining books. You will also see the |
792 | cascading delete operation via the DBIC_TRACE output: |
793 | |
3b1fa91b |
794 | SELECT me.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6' |
795 | DELETE FROM book WHERE ( id = ? ): '6' |
796 | SELECT me.book_id, me.author_id FROM book_author me WHERE ( me.book_id = ? ): '6' |
797 | DELETE FROM book_author WHERE ( author_id = ? AND book_id = ? ): '4', '6' |
d442cc9f |
798 | |
799 | |
800 | =head2 Fixing a Dangerous URL |
801 | |
55490817 |
802 | Note the URL in your browser once you have performed the deletion in the |
d442cc9f |
803 | prior step -- it is still referencing the delete action: |
804 | |
acbd7bdd |
805 | http://localhost:3000/books/id/6/delete |
d442cc9f |
806 | |
55490817 |
807 | What if the user were to press reload with this URL still active? In |
808 | this case the redundant delete is harmless (although it does generate |
809 | an exception screen, it doesn't perform any undesirable actions on the |
810 | application or database), but in other cases this could clearly be |
fbbb9084 |
811 | extremely dangerous. |
d442cc9f |
812 | |
813 | We can improve the logic by converting to a redirect. Unlike |
814 | C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform |
815 | a server-side alteration in the flow of processing, a redirect is a |
3533daff |
816 | client-side mechanism that causes the browser to issue an entirely |
d442cc9f |
817 | new request. As a result, the URL in the browser is updated to match |
818 | the destination of the redirection URL. |
819 | |
820 | To convert the forward used in the previous section to a redirect, |
55490817 |
821 | open C<lib/MyApp/Controller/Books.pm> and edit the existing |
d442cc9f |
822 | C<sub delete> method to match: |
823 | |
994b66ad |
824 | =head2 delete |
fce83e5f |
825 | |
d442cc9f |
826 | Delete a book |
fce83e5f |
827 | |
d442cc9f |
828 | =cut |
fce83e5f |
829 | |
994b66ad |
830 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
831 | my ($self, $c) = @_; |
fce83e5f |
832 | |
994b66ad |
833 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
834 | # with related 'book_author' entries |
994b66ad |
835 | $c->stash->{object}->delete; |
fce83e5f |
836 | |
d442cc9f |
837 | # Set a status message to be displayed at the top of the view |
838 | $c->stash->{status_msg} = "Book deleted."; |
fce83e5f |
839 | |
0416017e |
840 | # Redirect the user back to the list page. Note the use |
841 | # of $self->action_for as earlier in this section (BasicCRUD) |
fbbb9084 |
842 | $c->response->redirect($c->uri_for($self->action_for('list'))); |
d442cc9f |
843 | } |
844 | |
845 | |
846 | =head2 Try the Delete and Redirect Logic |
847 | |
f2bbfc36 |
848 | Point your browser to L<http://localhost:3000/books/list> (don't just |
849 | hit "Refresh" in your browser since we left the URL in an invalid state |
850 | in the previous section!) and delete the first copy of the remaining two |
851 | "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return |
852 | to the L<http://localhost:3000/books/list> URL, so that is an |
853 | improvement, but notice that I<no green "Book deleted" status message is |
854 | displayed>. Because the stash is reset on every request (and a redirect |
855 | involves a second request), the C<status_msg> is cleared before it can |
856 | be displayed. |
d442cc9f |
857 | |
858 | |
8a472b34 |
859 | =head2 Using 'uri_for' to Pass Query Parameters |
d442cc9f |
860 | |
4b4d3884 |
861 | There are several ways to pass information across a redirect. One |
862 | option is to use the C<flash> technique that we will see in Chapter 5 |
72609296 |
863 | of this tutorial; however, here we will pass the information via query |
4b4d3884 |
864 | parameters on the redirect itself. Open |
865 | C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete> |
89d3dae9 |
866 | method to match the following: |
d442cc9f |
867 | |
55490817 |
868 | =head2 delete |
fce83e5f |
869 | |
d442cc9f |
870 | Delete a book |
fce83e5f |
871 | |
d442cc9f |
872 | =cut |
fce83e5f |
873 | |
994b66ad |
874 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
875 | my ($self, $c) = @_; |
fce83e5f |
876 | |
994b66ad |
877 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
878 | # with related 'book_author' entries |
994b66ad |
879 | $c->stash->{object}->delete; |
fce83e5f |
880 | |
d442cc9f |
881 | # Redirect the user back to the list page with status msg as an arg |
55490817 |
882 | $c->response->redirect($c->uri_for($self->action_for('list'), |
d442cc9f |
883 | {status_msg => "Book deleted."})); |
884 | } |
885 | |
886 | This modification simply leverages the ability of C<uri_for> to include |
55490817 |
887 | an arbitrary number of name/value pairs in a hash reference. Next, we |
888 | need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a |
d442cc9f |
889 | query parameter: |
890 | |
1390ef0e |
891 | ... |
d442cc9f |
892 | <div id="content"> |
1390ef0e |
893 | [%# Status and error messages %] |
894 | <span class="message">[% status_msg || c.request.params.status_msg %]</span> |
895 | <span class="error">[% error_msg %]</span> |
896 | [%# This is where TT will stick all of your template's contents. -%] |
897 | [% content %] |
898 | </div><!-- end content --> |
899 | ... |
900 | |
55490817 |
901 | Although the sample above only shows the C<content> div, leave the |
1390ef0e |
902 | rest of the file intact -- the only change we made to the C<wrapper.tt2> |
55490817 |
903 | was to add "C<|| c.request.params.status_msg>" to the |
1390ef0e |
904 | C<E<lt>span class="message"E<gt>> line. |
d442cc9f |
905 | |
906 | |
907 | =head2 Try the Delete and Redirect With Query Param Logic |
908 | |
f2bbfc36 |
909 | Point your browser to L<http://localhost:3000/books/list> (you should |
910 | now be able to safely hit "refresh" in your browser). Then delete the |
911 | remaining copy of "TCPIP_Illustrated_Vol-2". The green "Book deleted" |
912 | status message should return. |
d442cc9f |
913 | |
55490817 |
914 | B<NOTE:> Another popular method for maintaining server-side |
915 | information across a redirect is to use the C<flash> technique we |
4b4d3884 |
916 | discuss in the next chapter of the tutorial, |
3ab6187c |
917 | L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>. While |
55490817 |
918 | C<flash> is a "slicker" mechanism in that it's all handled by the |
919 | server and doesn't "pollute" your URLs, B<it is important to note that |
920 | C<flash> can lead to situations where the wrong information shows up |
921 | in the wrong browser window if the user has multiple windows or |
72609296 |
922 | browser tabs open>. For example, Window A causes something to be |
55490817 |
923 | placed in the stash, but before that window performs a redirect, |
924 | Window B makes a request to the server and gets the status information |
994b66ad |
925 | that should really go to Window A. For this reason, you may wish |
89d3dae9 |
926 | to use the "query param" technique shown here in your applications. |
d442cc9f |
927 | |
928 | |
1cde0fd6 |
929 | =head1 EXPLORING THE POWER OF DBIC |
930 | |
55490817 |
931 | In this section we will explore some additional capabilities offered |
932 | by DBIx::Class. Although these features have relatively little to do |
933 | with Catalyst per se, you will almost certainly want to take advantage |
1cde0fd6 |
934 | of them in your applications. |
935 | |
936 | |
1cde0fd6 |
937 | =head2 Add Datetime Columns to Our Existing Books Table |
938 | |
55490817 |
939 | Let's add two columns to our existing C<books> table to track when |
1cde0fd6 |
940 | each book was added and when each book is updated: |
941 | |
942 | $ sqlite3 myapp.db |
3b1fa91b |
943 | sqlite> ALTER TABLE book ADD created INTEGER; |
944 | sqlite> ALTER TABLE book ADD updated INTEGER; |
945 | sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW'); |
946 | sqlite> SELECT * FROM book; |
f2bbfc36 |
947 | 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
948 | 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
949 | 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45 |
950 | 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
951 | 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
952 | 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1cde0fd6 |
953 | sqlite> .quit |
954 | $ |
955 | |
956 | This will modify the C<books> table to include the two new fields |
957 | and populate those fields with the current time. |
958 | |
acbd7bdd |
959 | |
a46b474e |
960 | =head2 Update DBIx::Class to Automatically Handle the Datetime Columns |
1cde0fd6 |
961 | |
962 | Next, we should re-run the DBIC helper to update the Result Classes |
963 | with the new fields: |
964 | |
965 | $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \ |
b66dd084 |
966 | create=static components=TimeStamp dbi:SQLite:myapp.db \ |
967 | on_connect_do="PRAGMA foreign_keys = ON" |
1cde0fd6 |
968 | exists "/root/dev/MyApp/script/../lib/MyApp/Model" |
969 | exists "/root/dev/MyApp/script/../t" |
970 | Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ... |
971 | Schema dump completed. |
972 | exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm" |
973 | |
974 | Notice that we modified our use of the helper slightly: we told |
d05dbc42 |
975 | it to include the L<DBIx::Class::TimeStamp|DBIx::Class::TimeStamp> |
1cde0fd6 |
976 | in the C<load_components> line of the Result Classes. |
977 | |
f2bbfc36 |
978 | If you open C<lib/MyApp/Schema/Result/Book.pm> in your editor you should |
979 | see that the C<created> and C<updated> fields are now included in the |
980 | call to C<add_columns()>. However, also notice that the C<many_to_many> |
981 | relationships we manually added below the "C<# DO NOT MODIFY...>" line |
982 | were automatically preserved. |
1cde0fd6 |
983 | |
55490817 |
984 | While we have this file open, let's update it with some additional |
985 | information to have DBIC automatically handle the updating of these |
986 | two fields for us. Insert the following code at the bottom of the |
987 | file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and |
1cde0fd6 |
988 | B<above> the C<1;> on the last line): |
989 | |
990 | # |
991 | # Enable automatic date handling |
992 | # |
993 | __PACKAGE__->add_columns( |
994 | "created", |
995 | { data_type => 'datetime', set_on_create => 1 }, |
996 | "updated", |
997 | { data_type => 'datetime', set_on_create => 1, set_on_update => 1 }, |
55490817 |
998 | ); |
1cde0fd6 |
999 | |
a46b474e |
1000 | This will override the definition for these fields that Schema::Loader |
1001 | placed at the top of the file. The C<set_on_create> and |
1002 | C<set_on_update> options will cause DBIx::Class to automatically |
1003 | update the timestamps in these columns whenever a row is created or |
1004 | modified. |
1cde0fd6 |
1005 | |
1cde0fd6 |
1006 | Then enter the following URL into your web browser: |
1007 | |
1008 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
1009 | |
1010 | You should get the same "Book Created" screen we saw above. However, |
1011 | if you now use the sqlite3 command-line tool to dump the C<books> table, |
1012 | you will see that the new book we added has an appropriate date and |
1013 | time entered for it (see the last line in the listing below): |
1014 | |
444d6b27 |
1015 | $ sqlite3 myapp.db "select * from book" |
f2bbfc36 |
1016 | 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1017 | 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1018 | 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1019 | 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1020 | 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1021 | 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1022 | 10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42 |
1cde0fd6 |
1023 | |
55490817 |
1024 | Notice in the debug log that the SQL DBIC generated has changed to |
1cde0fd6 |
1025 | incorporate the datetime logic: |
1026 | |
2a6eb5f9 |
1027 | INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ): |
f2bbfc36 |
1028 | '2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42' |
2a6eb5f9 |
1029 | INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10' |
1cde0fd6 |
1030 | |
1031 | |
1032 | =head2 Create a ResultSet Class |
1033 | |
444d6b27 |
1034 | An often overlooked but extremely powerful features of DBIC is that it |
55490817 |
1035 | allows you to supply your own subclasses of C<DBIx::Class::ResultSet>. |
1036 | It allows you to pull complex and unsightly "query code" out of your |
1cde0fd6 |
1037 | controllers and encapsulate it in a method of your ResultSet Class. |
1038 | These "canned queries" in your ResultSet Class can then be invoked |
1039 | via a single call, resulting in much cleaner and easier to read |
1040 | controller code. |
1041 | |
55490817 |
1042 | To illustrate the concept with a fairly simple example, let's create a |
1cde0fd6 |
1043 | method that returns books added in the last 10 minutes. Start by |
a46b474e |
1044 | making a directory where DBIx::Class will look for our ResultSet Class: |
1cde0fd6 |
1045 | |
444d6b27 |
1046 | $ mkdir lib/MyApp/Schema/ResultSet |
1cde0fd6 |
1047 | |
3b1fa91b |
1048 | Then open C<lib/MyApp/Schema/ResultSet/Book.pm> and enter the following: |
1cde0fd6 |
1049 | |
3b1fa91b |
1050 | package MyApp::Schema::ResultSet::Book; |
fce83e5f |
1051 | |
1cde0fd6 |
1052 | use strict; |
1053 | use warnings; |
1054 | use base 'DBIx::Class::ResultSet'; |
fce83e5f |
1055 | |
1cde0fd6 |
1056 | =head2 created_after |
fce83e5f |
1057 | |
1cde0fd6 |
1058 | A predefined search for recently added books |
fce83e5f |
1059 | |
1cde0fd6 |
1060 | =cut |
fce83e5f |
1061 | |
1cde0fd6 |
1062 | sub created_after { |
fadc4ae7 |
1063 | my ($self, $datetime) = @_; |
fce83e5f |
1064 | |
b66dd084 |
1065 | my $date_str = $self->result_source->schema->storage |
fadc4ae7 |
1066 | ->datetime_parser->format_datetime($datetime); |
fce83e5f |
1067 | |
fadc4ae7 |
1068 | return $self->search({ |
1069 | created => { '>' => $date_str } |
1070 | }); |
1cde0fd6 |
1071 | } |
fce83e5f |
1072 | |
1cde0fd6 |
1073 | 1; |
1074 | |
1cde0fd6 |
1075 | Then add the following method to the C<lib/MyApp/Controller/Books.pm>: |
1076 | |
1077 | =head2 list_recent |
fce83e5f |
1078 | |
1cde0fd6 |
1079 | List recently created books |
fce83e5f |
1080 | |
1cde0fd6 |
1081 | =cut |
fce83e5f |
1082 | |
1cde0fd6 |
1083 | sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) { |
1084 | my ($self, $c, $mins) = @_; |
fce83e5f |
1085 | |
1cde0fd6 |
1086 | # Retrieve all of the book records as book model objects and store in the |
1087 | # stash where they can be accessed by the TT template, but only |
1088 | # retrieve books created within the last $min number of minutes |
3b1fa91b |
1089 | $c->stash->{books} = [$c->model('DB::Book') |
1cde0fd6 |
1090 | ->created_after(DateTime->now->subtract(minutes => $mins))]; |
fce83e5f |
1091 | |
1cde0fd6 |
1092 | # Set the TT template to use. You will almost always want to do this |
1093 | # in your action methods (action methods respond to user input in |
1094 | # your controllers). |
1095 | $c->stash->{template} = 'books/list.tt2'; |
1096 | } |
1097 | |
f2bbfc36 |
1098 | Now try different values for the "minutes" argument (the final number |
1099 | value) using the URL C<http://localhost:3000/books/list_recent/_#_> in |
1100 | your browser. For example, this would list all books added in the last |
1101 | fifteen minutes: |
1cde0fd6 |
1102 | |
1103 | http://localhost:3000/books/list_recent/15 |
1104 | |
1105 | Depending on how recently you added books, you might want to |
1106 | try a higher or lower value. |
1107 | |
1108 | |
1109 | =head2 Chaining ResultSets |
1110 | |
a46b474e |
1111 | One of the most helpful and powerful features in DBIx::Class is that |
1112 | it allows you to "chain together" a series of queries (note that this |
1113 | has nothing to do with the "Chained Dispatch" for Catalyst that we |
1114 | were discussing above). Because each ResultSet returns another |
1115 | ResultSet, you can take an initial query and immediately feed that |
1116 | into a second query (and so on for as many queries you need). Note |
1117 | that no matter how many ResultSets you chain together, the database |
1118 | itself will not be hit until you use a method that attempts to access |
1119 | the data. And, because this technique carries over to the ResultSet |
1120 | Class feature we implemented in the previous section for our "canned |
1121 | search", we can combine the two capabilities. For example, let's add |
1122 | an action to our C<Books> controller that lists books that are both |
1123 | recent I<and> have "TCP" in the title. Open up |
1124 | C<lib/MyApp/Controller/Books.pm> and add the following method: |
1cde0fd6 |
1125 | |
acbd7bdd |
1126 | =head2 list_recent_tcp |
fce83e5f |
1127 | |
1cde0fd6 |
1128 | List recently created books |
fce83e5f |
1129 | |
1cde0fd6 |
1130 | =cut |
fce83e5f |
1131 | |
1cde0fd6 |
1132 | sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) { |
1133 | my ($self, $c, $mins) = @_; |
fce83e5f |
1134 | |
1cde0fd6 |
1135 | # Retrieve all of the book records as book model objects and store in the |
1136 | # stash where they can be accessed by the TT template, but only |
1137 | # retrieve books created within the last $min number of minutes |
1138 | # AND that have 'TCP' in the title |
3b1fa91b |
1139 | $c->stash->{books} = [$c->model('DB::Book') |
1cde0fd6 |
1140 | ->created_after(DateTime->now->subtract(minutes => $mins)) |
1141 | ->search({title => {'like', '%TCP%'}}) |
1142 | ]; |
fce83e5f |
1143 | |
1cde0fd6 |
1144 | # Set the TT template to use. You will almost always want to do this |
1145 | # in your action methods (action methods respond to user input in |
1146 | # your controllers). |
1147 | $c->stash->{template} = 'books/list.tt2'; |
1148 | } |
1149 | |
f2bbfc36 |
1150 | To try this out, enter the following URL into your browser: |
1cde0fd6 |
1151 | |
1152 | http://localhost:3000/books/list_recent_tcp/100 |
1153 | |
55490817 |
1154 | And you should get a list of books added in the last 100 minutes that |
1155 | contain the string "TCP" in the title. However, if you look at all |
1156 | books within the last 100 minutes, you should get a longer list |
1157 | (again, you might have to adjust the number of minutes depending on |
1cde0fd6 |
1158 | how recently you added books to your database): |
1159 | |
1160 | http://localhost:3000/books/list_recent/100 |
1161 | |
55490817 |
1162 | Take a look at the DBIC_TRACE output in the development server log for |
1cde0fd6 |
1163 | the first URL and you should see something similar to the following: |
1164 | |
fce83e5f |
1165 | SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me |
f2bbfc36 |
1166 | WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32' |
1cde0fd6 |
1167 | |
55490817 |
1168 | However, let's not pollute our controller code with this raw "TCP" |
1169 | query -- it would be cleaner to encapsulate that code in a method on |
1170 | our ResultSet Class. To do this, open |
3b1fa91b |
1171 | C<lib/MyApp/Schema/ResultSet/Book.pm> and add the following method: |
1cde0fd6 |
1172 | |
1173 | =head2 title_like |
fce83e5f |
1174 | |
1cde0fd6 |
1175 | A predefined search for books with a 'LIKE' search in the string |
fce83e5f |
1176 | |
1cde0fd6 |
1177 | =cut |
fce83e5f |
1178 | |
1cde0fd6 |
1179 | sub title_like { |
fadc4ae7 |
1180 | my ($self, $title_str) = @_; |
fce83e5f |
1181 | |
fadc4ae7 |
1182 | return $self->search({ |
1183 | title => { 'like' => "%$title_str%" } |
1184 | }); |
1cde0fd6 |
1185 | } |
1186 | |
55490817 |
1187 | We defined the search string as C<$title_str> to make the method more |
1188 | flexible. Now update the C<list_recent_tcp> method in |
1189 | C<lib/MyApp/Controller/Books.pm> to match the following (we have |
1190 | replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line |
1cde0fd6 |
1191 | shown here -- the rest of the method should be the same): |
1192 | |
1193 | =head2 list_recent_tcp |
fce83e5f |
1194 | |
1cde0fd6 |
1195 | List recently created books |
fce83e5f |
1196 | |
1cde0fd6 |
1197 | =cut |
fce83e5f |
1198 | |
1cde0fd6 |
1199 | sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) { |
1200 | my ($self, $c, $mins) = @_; |
fce83e5f |
1201 | |
1cde0fd6 |
1202 | # Retrieve all of the book records as book model objects and store in the |
1203 | # stash where they can be accessed by the TT template, but only |
1204 | # retrieve books created within the last $min number of minutes |
1205 | # AND that have 'TCP' in the title |
3b1fa91b |
1206 | $c->stash->{books} = [$c->model('DB::Book') |
1cde0fd6 |
1207 | ->created_after(DateTime->now->subtract(minutes => $mins)) |
1208 | ->title_like('TCP') |
1209 | ]; |
fce83e5f |
1210 | |
1cde0fd6 |
1211 | # Set the TT template to use. You will almost always want to do this |
1212 | # in your action methods (action methods respond to user input in |
1213 | # your controllers). |
1214 | $c->stash->{template} = 'books/list.tt2'; |
1215 | } |
1216 | |
f2bbfc36 |
1217 | Try out the C<list_recent_tcp> and C<list_recent> URLs as we did above. |
1218 | They should work just the same, but our code is obviously cleaner and |
1219 | more modular, while also being more flexible at the same time. |
1cde0fd6 |
1220 | |
1221 | |
1222 | =head2 Adding Methods to Result Classes |
1223 | |
a46b474e |
1224 | In the previous two sections we saw a good example of how we could use |
1225 | DBIx::Class ResultSet Classes to clean up our code for an entire query |
1226 | (for example, our "canned searches" that filtered the entire query). |
1227 | We can do a similar improvement when working with individual rows as |
1228 | well. Whereas the ResultSet construct is used in DBIC to correspond |
1229 | to an entire query, the Result Class construct is used to represent a |
1230 | row. Therefore, we can add row-specific "helper methods" to our Result |
1231 | Classes stored in C<lib/MyApp/Schema/Result/>. For example, open |
3b1fa91b |
1232 | C<lib/MyApp/Schema/Result/Author.pm> and add the following method (as |
a46b474e |
1233 | always, it must be above the closing "C<1;>"): |
1cde0fd6 |
1234 | |
1235 | # |
1236 | # Helper methods |
1237 | # |
1238 | sub full_name { |
1239 | my ($self) = @_; |
fce83e5f |
1240 | |
1cde0fd6 |
1241 | return $self->first_name . ' ' . $self->last_name; |
1242 | } |
1243 | |
55490817 |
1244 | This will allow us to conveniently retrieve both the first and last |
1245 | name for an author in one shot. Now open C<root/src/books/list.tt2> |
1cde0fd6 |
1246 | and change the definition of C<tt_authors> from this: |
1247 | |
acbd7bdd |
1248 | ... |
1cde0fd6 |
1249 | [% tt_authors = [ ]; |
fce83e5f |
1250 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
acbd7bdd |
1251 | ... |
1cde0fd6 |
1252 | |
1253 | to: |
1254 | |
acbd7bdd |
1255 | ... |
1cde0fd6 |
1256 | [% tt_authors = [ ]; |
fce83e5f |
1257 | tt_authors.push(author.full_name) FOREACH author = book.authors %] |
acbd7bdd |
1258 | ... |
1cde0fd6 |
1259 | |
55490817 |
1260 | (Only C<author.last_name> was changed to C<author.full_name> -- the |
1cde0fd6 |
1261 | rest of the file should remain the same.) |
1262 | |
f2bbfc36 |
1263 | Now go to the standard book list URL: |
1cde0fd6 |
1264 | |
1265 | http://localhost:3000/books/list |
1266 | |
55490817 |
1267 | The "Author(s)" column will now contain both the first and last name. |
1268 | And, because the concatenation logic was encapsulated inside our |
444d6b27 |
1269 | Result Class, it keeps the code inside our TT template nice and clean |
55490817 |
1270 | (remember, we want the templates to be as close to pure HTML markup as |
1271 | possible). Obviously, this capability becomes even more useful as you |
444d6b27 |
1272 | use to to remove even more complicated row-specific logic from your |
1cde0fd6 |
1273 | templates! |
1274 | |
1275 | |
fce83e5f |
1276 | =head2 Moving Complicated View Code to the Model |
1277 | |
1278 | The previous section illustrated how we could use a Result Class |
1279 | method to print the full names of the authors without adding any extra |
1280 | code to our view, but it still left us with a fairly ugly mess (see |
1281 | C<root/src/books/list.tt2>): |
1282 | |
1283 | ... |
1284 | <td> |
1285 | [% # NOTE: See Chapter 4 for a better way to do this! -%] |
1286 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
1287 | [% # loop in 'side effect notation' to load just the last names of the -%] |
1288 | [% # authors into the list. Note that the 'push' TT vmethod does not print -%] |
1289 | [% # a value, so nothing will be printed here. But, if you have something -%] |
1290 | [% # in TT that does return a method and you don't want it printed, you -%] |
1291 | [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%] |
1292 | [% # call it and discard the return value. -%] |
1293 | [% tt_authors = [ ]; |
1294 | tt_authors.push(author.full_name) FOREACH author = book.authors %] |
1295 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
1296 | [% # Note the use of the TT filter "| html" to escape dangerous characters -%] |
1297 | ([% tt_authors.size | html %]) |
1298 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
1299 | [% tt_authors.join(', ') | html %] |
1300 | </td> |
1301 | ... |
1302 | |
1303 | Let's combine some of the techniques used earlier in this section to |
1304 | clean this up. First, let's add a method to our Book Result Class to |
1305 | return the number of authors for a book. Open |
1306 | C<lib/MyApp/Schema/Result/Book.pm> and add the following method: |
1307 | |
444d6b27 |
1308 | =head2 author_count |
1309 | |
1310 | Return the number of authors for the current book |
1311 | |
fce83e5f |
1312 | =cut |
1313 | |
1314 | sub author_count { |
1315 | my ($self) = @_; |
1316 | |
1317 | # Use the 'many_to_many' relationship to fetch all of the authors for the current |
1318 | # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT |
1319 | return $self->authors->count; |
1320 | } |
1321 | |
1322 | Next, let's add a method to return a list of authors for a book to the |
1323 | same C<lib/MyApp/Schema/Result/Book.pm> file: |
1324 | |
1325 | =head2 author_list |
1326 | |
1327 | Return a comma-separated list of authors for the current book |
1328 | |
1329 | =cut |
1330 | |
1331 | sub author_list { |
1332 | my ($self) = @_; |
1333 | |
1334 | # Loop through all authors for the current book, calling all the 'full_name' |
1335 | # Result Class method for each |
1336 | my @names; |
1337 | foreach my $author ($self->authors) { |
1338 | push(@names, $author->full_name); |
1339 | } |
1340 | |
1341 | return join(', ', @names); |
1342 | } |
1343 | |
1344 | This method loops through each author, using the C<full_name> Result |
1345 | Class method we added to C<lib/MyApp/Schema/Result/Author.pm> in the |
1346 | prior section. |
1347 | |
1348 | Using these two methods, we can simplify our TT code. Open |
1349 | C<root/src/books/list.tt2> and update the "Author(s)" table cell to |
1350 | match the following: |
1351 | |
1352 | ... |
1353 | <td> |
1354 | [% # Print count and author list using Result Class methods -%] |
1355 | ([% book.author_count | html %]) [% book.author_list | html %] |
1356 | </td> |
1357 | ... |
1358 | |
1359 | Although most of the code we removed comprised comments, the overall |
f2bbfc36 |
1360 | effect is dramatic... because our view code is so simple, we don't need |
1361 | huge comments to clue people in to the gist of our code. The view code |
1362 | is now self-documenting and readable enough that you could probably get |
1363 | by with no comments at all. All of the "complex" work is being done in |
1364 | our Result Class methods (and, because we have broken the code into |
1365 | nice, modular chucks, the Result Class code is hardly something you |
1366 | would call complex). |
fce83e5f |
1367 | |
1368 | As we saw in this section, always strive to keep your view AND |
1369 | controller code as simple as possible by pulling code out into your |
1370 | model objects. Because DBIx::Class can be easily extended in so many |
1371 | ways, it's an excellent to way accomplish this objective. It will |
1372 | make your code cleaner, easier to write, less error-prone, and easier |
1373 | to debug and maintain. |
1374 | |
f2bbfc36 |
1375 | Before you conclude this section, hit Refresh in your browser... the |
1376 | output should be the same even though the backend code has been trimmed |
1377 | down. |
444d6b27 |
1378 | |
fce83e5f |
1379 | |
d442cc9f |
1380 | =head1 AUTHOR |
1381 | |
1382 | Kennedy Clark, C<hkclark@gmail.com> |
1383 | |
1384 | Please report any errors, issues or suggestions to the author. The |
1385 | most recent version of the Catalyst Tutorial can be found at |
59884771 |
1386 | L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>. |
d442cc9f |
1387 | |
45c7830f |
1388 | Copyright 2006-2008, Kennedy Clark, under Creative Commons License |
95674086 |
1389 | (L<http://creativecommons.org/licenses/by-sa/3.0/us/>). |