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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 |
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60 | created in |
61 | L<Chapter 3|Catalyst::Manual::Tutorial::03_MoreCatalystBasics> to add |
62 | basic support for Create, Read, Update, and Delete (CRUD) of C<Book> |
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63 | objects. Note that the 'list' function in |
64 | L<Chapter 3|Catalyst::Manual::Tutorial::03_MoreCatalystBasics> already |
65 | implements the Read portion of CRUD (although Read normally refers to |
66 | reading a single object; you could implement full Read functionality |
67 | using the techniques introduced below). This section will focus on the |
68 | Create and Delete aspects of CRUD. More advanced capabilities, |
69 | including full Update functionality, will be addressed in |
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70 | L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>. |
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71 | |
72 | Although this chapter of the tutorial will show you how to build CRUD |
73 | functionality yourself, another option is to use a "CRUD builder" type |
74 | of tool to automate the process. You get less control, but it can be |
75 | quick and easy. For example, see L<Catalyst::Plugin::AutoCRUD>, |
76 | L<CatalystX::CRUD>, and L<CatalystX::CRUD::YUI>. |
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77 | |
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78 | Source code for the tutorial in included in the F</root/Final> directory |
79 | of the Tutorial Virtual machine (one subdirectory per chapter). There |
80 | are also instructions for downloading the code in |
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81 | L<Catalyst::Manual::Tutorial::01_Intro>. |
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82 | |
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83 | |
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84 | =head1 FORMLESS SUBMISSION |
85 | |
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86 | Our initial attempt at object creation will utilize the "URL arguments" |
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87 | feature of Catalyst (we will employ the more common form-based |
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88 | submission in the sections that follow). |
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89 | |
90 | |
91 | =head2 Include a Create Action in the Books Controller |
92 | |
93 | Edit C<lib/MyApp/Controller/Books.pm> and enter the following method: |
94 | |
95 | =head2 url_create |
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96 | |
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97 | Create a book with the supplied title, rating, and author |
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98 | |
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99 | =cut |
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100 | |
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101 | sub url_create :Local { |
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102 | # In addition to self & context, get the title, rating, & |
103 | # author_id args from the URL. Note that Catalyst automatically |
104 | # puts extra information after the "/<controller_name>/<action_name/" |
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105 | # into @_. The args are separated by the '/' char on the URL. |
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106 | my ($self, $c, $title, $rating, $author_id) = @_; |
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107 | |
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108 | # Call create() on the book model object. Pass the table |
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109 | # columns/field values we want to set as hash values |
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110 | my $book = $c->model('DB::Book')->create({ |
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111 | title => $title, |
112 | rating => $rating |
113 | }); |
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114 | |
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115 | # Add a record to the join table for this book, mapping to |
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116 | # appropriate author |
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117 | $book->add_to_book_authors({author_id => $author_id}); |
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118 | # Note: Above is a shortcut for this: |
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119 | # $book->create_related('book_authors', {author_id => $author_id}); |
120 | |
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121 | # Assign the Book object to the stash for display and set template |
122 | $c->stash(book => $book, |
123 | template => 'books/create_done.tt2'); |
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124 | |
125 | # Disable caching for this page |
126 | $c->response->header('Cache-Control' => 'no-cache'); |
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127 | } |
128 | |
129 | Notice that Catalyst takes "extra slash-separated information" from the |
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130 | URL and passes it as arguments in C<@_> (as long as the number of |
131 | arguments is not "fixed" using an attribute like C<:Args(0)>). The |
132 | C<url_create> action then uses a simple call to the DBIC C<create> |
133 | method to add the requested information to the database (with a separate |
134 | call to C<add_to_book_authors> to update the join table). As do |
135 | virtually all controller methods (at least the ones that directly handle |
136 | user input), it then sets the template that should handle this request. |
137 | |
138 | Also note that we are explicitly setting a C<no-cache> "Cache-Control" |
139 | header to force browsers using the page to get a fresh copy every time. |
140 | You could even move this to a C<auto> method in |
141 | C<lib/MyApp/Controller/Root.pm> and it would automatically get applied |
142 | to every page in the whole application via a single line of code |
143 | (remember from Chapter 3, that every C<auto> method gets run in the |
144 | Controller hierarchy). |
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145 | |
146 | |
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147 | =head2 Include a Template for the 'url_create' Action: |
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148 | |
149 | Edit C<root/src/books/create_done.tt2> and then enter: |
150 | |
151 | [% # Use the TT Dumper plugin to Data::Dumper variables to the browser -%] |
152 | [% # Not a good idea for production use, though. :-) 'Indent=1' is -%] |
153 | [% # optional, but prevents "massive indenting" of deeply nested objects -%] |
154 | [% USE Dumper(Indent=1) -%] |
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155 | |
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156 | [% # Set the page title. META can 'go back' and set values in templates -%] |
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157 | [% # that have been processed 'before' this template (here it's updating -%] |
158 | [% # the title in the root/src/wrapper.tt2 wrapper template). Note that -%] |
159 | [% # META only works on simple/static strings (i.e. there is no variable -%] |
160 | [% # interpolation -- if you need dynamic/interpolated content in your -%] |
161 | [% # title, set "$c->stash(title => $something)" in the controller). -%] |
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162 | [% META title = 'Book Created' %] |
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163 | |
164 | [% # Output information about the record that was added. First title. -%] |
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165 | <p>Added book '[% book.title %]' |
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166 | |
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167 | [% # Then, output the last name of the first author -%] |
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168 | by '[% book.authors.first.last_name %]' |
169 | |
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170 | [% # Then, output the rating for the book that was added -%] |
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171 | with a rating of [% book.rating %].</p> |
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172 | |
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173 | [% # Provide a link back to the list page. 'c.uri_for' builds -%] |
174 | [% # a full URI; e.g., 'http://localhost:3000/books/list' -%] |
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175 | <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p> |
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176 | |
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177 | [% # Try out the TT Dumper (for development only!) -%] |
178 | <pre> |
179 | Dump of the 'book' variable: |
180 | [% Dumper.dump(book) %] |
181 | </pre> |
182 | |
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183 | The TT C<USE> directive allows access to a variety of plugin modules (TT |
184 | plugins, that is, not Catalyst plugins) to add extra functionality to |
185 | the base TT capabilities. Here, the plugin allows L<Data::Dumper> |
186 | "pretty printing" of objects and variables. Other than that, the rest |
187 | of the code should be familiar from the examples in Chapter 3. |
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188 | |
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189 | |
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190 | =head2 Try the 'url_create' Feature |
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191 | |
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192 | Make sure the development server is running with the "-r" restart |
193 | option: |
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194 | |
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195 | $ DBIC_TRACE=1 script/myapp_server.pl -r |
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196 | |
197 | Note that new path for C</books/url_create> appears in the startup debug |
198 | output. |
199 | |
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200 | Next, use your browser to enter the following URL: |
201 | |
202 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
203 | |
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204 | Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by |
205 | 'Stevens' with a rating of 5." along with a dump of the new book model |
206 | object as it was returned by DBIC. You should also see the following |
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207 | DBIC debug messages displayed in the development server log messages if |
208 | you have DBIC_TRACE set: |
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209 | |
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210 | INSERT INTO book (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2' |
211 | INSERT INTO book_author (author_id, book_id) VALUES (?, ?): `4', `6' |
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212 | |
213 | The C<INSERT> statements are obviously adding the book and linking it to |
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214 | the existing record for Richard Stevens. The C<SELECT> statement |
215 | results from DBIC automatically fetching the book for the |
216 | C<Dumper.dump(book)>. |
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217 | |
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218 | If you then click the "Return to list" link, you should find that there |
219 | are now six books shown (if necessary, Shift+Reload or Ctrl+Reload your |
220 | browser at the C</books/list> page). You should now see the six DBIC |
221 | debug messages similar to the following (where N=1-6): |
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222 | |
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223 | SELECT author.id, author.first_name, author.last_name |
224 | FROM book_author me JOIN author author |
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225 | ON author.id = me.author_id WHERE ( me.book_id = ? ): 'N' |
226 | |
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227 | |
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228 | =head1 CONVERT TO A CHAINED ACTION |
229 | |
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230 | Although the example above uses the same C<Local> action type for the |
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231 | method that we saw in the previous chapter of the tutorial, there is an |
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232 | alternate approach that allows us to be more specific while also paving |
233 | the way for more advanced capabilities. Change the method declaration |
234 | for C<url_create> in C<lib/MyApp/Controller/Books.pm> you entered above |
235 | to match the following: |
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236 | |
237 | sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) { |
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238 | # In addition to self & context, get the title, rating, & |
239 | # author_id args from the URL. Note that Catalyst automatically |
240 | # puts the first 3 arguments worth of extra information after the |
241 | # "/<controller_name>/<action_name/" into @_ because we specified |
242 | # "Args(3)". The args are separated by the '/' char on the URL. |
243 | my ($self, $c, $title, $rating, $author_id) = @_; |
244 | |
245 | ... |
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246 | |
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247 | This converts the method to take advantage of the Chained |
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248 | action/dispatch type. Chaining lets you have a single URL automatically |
249 | dispatch to several controller methods, each of which can have precise |
250 | control over the number of arguments that it will receive. A chain can |
251 | essentially be thought of having three parts -- a beginning, a middle, |
252 | and an end. The bullets below summarize the key points behind each of |
253 | these parts of a chain: |
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254 | |
255 | |
256 | =over 4 |
257 | |
258 | |
259 | =item * |
260 | |
261 | Beginning |
262 | |
263 | =over 4 |
264 | |
265 | =item * |
266 | |
267 | B<Use "C<:Chained('/')>" to start a chain> |
268 | |
269 | =item * |
270 | |
271 | Get arguments through C<CaptureArgs()> |
272 | |
273 | =item * |
274 | |
275 | Specify the path to match with C<PathPart()> |
276 | |
277 | =back |
278 | |
279 | |
280 | =item * |
281 | |
282 | Middle |
283 | |
284 | =over 4 |
285 | |
286 | =item * |
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287 | |
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288 | Link to previous part of the chain with C<:Chained('_name_')> |
289 | |
290 | =item * |
291 | |
292 | Get arguments through C<CaptureArgs()> |
293 | |
294 | =item * |
295 | |
296 | Specify the path to match with C<PathPart()> |
297 | |
298 | =back |
299 | |
300 | |
301 | =item * |
302 | |
303 | End |
304 | |
305 | =over 4 |
306 | |
307 | =item * |
308 | |
309 | Link to previous part of the chain with C<:Chained('_name_')> |
310 | |
311 | =item * |
312 | |
313 | B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain> |
314 | |
315 | =item * |
316 | |
317 | Specify the path to match with C<PathPart()> |
318 | |
319 | =back |
320 | |
321 | |
322 | =back |
323 | |
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324 | In our C<url_create> method above, we have combined all three parts into |
325 | a single method: C<:Chained('/')> to start the chain, |
326 | C<:PathPart('books/url_create')> to specify the base URL to match, and |
327 | C<:Args(3)> to capture exactly three arguments and to end the chain. |
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328 | |
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329 | As we will see shortly, a chain can consist of as many "links" as you |
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330 | wish, with each part capturing some arguments and doing some work along |
331 | the way. We will continue to use the Chained action type in this |
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332 | chapter of the tutorial and explore slightly more advanced capabilities |
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333 | with the base method and delete feature below. But Chained dispatch is |
334 | capable of far more. For additional information, see |
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335 | L<Catalyst::Manual::Intro/Action types>, |
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336 | L<Catalyst::DispatchType::Chained>, and the 2006 Advent calendar entry |
337 | on the subject: L<http://www.catalystframework.org/calendar/2006/10>. |
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338 | |
339 | |
340 | =head2 Try the Chained Action |
341 | |
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342 | If you look back at the development server startup logs from your |
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343 | initial version of the C<url_create> method (the one using the C<:Local> |
344 | attribute), you will notice that it produced output similar to the |
345 | following: |
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346 | |
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347 | [debug] Loaded Path actions: |
348 | .-------------------------------------+--------------------------------------. |
349 | | Path | Private | |
350 | +-------------------------------------+--------------------------------------+ |
351 | | / | /default | |
352 | | / | /index | |
353 | | /books | /books/index | |
354 | | /books/list | /books/list | |
355 | | /books/url_create | /books/url_create | |
356 | '-------------------------------------+--------------------------------------' |
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357 | |
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358 | When the development server restarts after our conversion to Chained |
359 | dispatch, the debug output should change to something along the lines of |
360 | the following: |
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361 | |
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362 | [debug] Loaded Path actions: |
363 | .-------------------------------------+--------------------------------------. |
364 | | Path | Private | |
365 | +-------------------------------------+--------------------------------------+ |
366 | | / | /default | |
367 | | / | /index | |
368 | | /books | /books/index | |
369 | | /books/list | /books/list | |
370 | '-------------------------------------+--------------------------------------' |
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371 | |
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372 | [debug] Loaded Chained actions: |
373 | .-------------------------------------+--------------------------------------. |
374 | | Path Spec | Private | |
375 | +-------------------------------------+--------------------------------------+ |
376 | | /books/url_create/*/*/* | /books/url_create | |
377 | '-------------------------------------+--------------------------------------' |
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378 | |
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379 | C<url_create> has disappeared from the "Loaded Path actions" section but |
380 | it now shows up under the newly created "Loaded Chained actions" |
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381 | section. And the "/*/*/*" portion clearly shows our requirement for |
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382 | three arguments. |
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383 | |
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384 | As with our non-chained version of C<url_create>, use your browser to |
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385 | enter the following URL: |
386 | |
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387 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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388 | |
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389 | You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by |
390 | 'Stevens' with a rating of 5." along with a dump of the new book model |
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391 | object. Click the "Return to list" link, and you should find that there |
392 | are now seven books shown (two copies of I<TCPIP_Illustrated_Vol-2>). |
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393 | |
394 | |
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395 | =head2 Refactor to Use a 'base' Method to Start the Chains |
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396 | |
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397 | Let's make a quick update to our initial Chained action to show a little |
398 | more of the power of chaining. First, open |
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399 | C<lib/MyApp/Controller/Books.pm> in your editor and add the following |
400 | method: |
401 | |
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402 | =head2 base |
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403 | |
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404 | Can place common logic to start chained dispatch here |
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405 | |
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406 | =cut |
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407 | |
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408 | sub base :Chained('/') :PathPart('books') :CaptureArgs(0) { |
409 | my ($self, $c) = @_; |
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410 | |
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411 | # Store the ResultSet in stash so it's available for other methods |
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412 | $c->stash(resultset => $c->model('DB::Book')); |
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413 | |
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414 | # Print a message to the debug log |
415 | $c->log->debug('*** INSIDE BASE METHOD ***'); |
416 | } |
417 | |
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418 | Here we print a log message and store the DBIC ResultSet in |
419 | C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available |
420 | for other actions that chain off C<base>. If your controller always |
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421 | needs a book ID as its first argument, you could have the base method |
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422 | capture that argument (with C<:CaptureArgs(1)>) and use it to pull the |
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423 | book object with C<-E<gt>find($id)> and leave it in the stash for later |
424 | parts of your chains to then act upon. Because we have several actions |
425 | that don't need to retrieve a book (such as the C<url_create> we are |
426 | working with now), we will instead add that functionality to a common |
427 | C<object> action shortly. |
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428 | |
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429 | As for C<url_create>, let's modify it to first dispatch to C<base>. |
430 | Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for |
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431 | C<url_create> to match the following: |
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432 | |
433 | sub url_create :Chained('base') :PathPart('url_create') :Args(3) { |
434 | |
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435 | Once you save C<lib/MyApp/Controller/Books.pm>, notice that the |
436 | development server will restart and our "Loaded Chained actions" section |
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437 | will changed slightly: |
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438 | |
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439 | [debug] Loaded Chained actions: |
440 | .-------------------------------------+--------------------------------------. |
441 | | Path Spec | Private | |
442 | +-------------------------------------+--------------------------------------+ |
443 | | /books/url_create/*/*/* | /books/base (0) | |
444 | | | => /books/url_create | |
445 | '-------------------------------------+--------------------------------------' |
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446 | |
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447 | The "Path Spec" is the same, but now it maps to two Private actions as |
448 | we would expect. The C<base> method is being triggered by the C</books> |
449 | part of the URL. However, the processing then continues to the |
450 | C<url_create> method because this method "chained" off C<base> and |
451 | specified C<:PathPart('url_create')> (note that we could have omitted |
452 | the "PathPart" here because it matches the name of the method, but we |
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453 | will include it to make the logic as explicit as possible). |
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454 | |
455 | Once again, enter the following URL into your browser: |
456 | |
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457 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
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458 | |
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459 | The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a |
460 | rating of 5." message and a dump of the new book object should appear. |
461 | Also notice the extra "INSIDE BASE METHOD" debug message in the |
462 | development server output from the C<base> method. Click the "Return to |
463 | list" link, and you should find that there are now eight books shown. |
464 | (You may have a larger number of books if you repeated any of the |
465 | "create" actions more than once. Don't worry about it as long as the |
466 | number of books is appropriate for the number of times you added new |
467 | books... there should be the original five books added via |
468 | C<myapp01.sql> plus one additional book for each time you ran one of the |
469 | url_create variations above.) |
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470 | |
471 | |
472 | =head1 MANUALLY BUILDING A CREATE FORM |
473 | |
474 | Although the C<url_create> action in the previous step does begin to |
475 | reveal the power and flexibility of both Catalyst and DBIC, it's |
476 | obviously not a very realistic example of how users should be expected |
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477 | to enter data. This section begins to address that concern (but just |
478 | barely, see L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD> |
479 | for better options for handling web-based forms). |
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480 | |
481 | |
482 | =head2 Add Method to Display The Form |
483 | |
484 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method: |
485 | |
486 | =head2 form_create |
fce83e5f |
487 | |
d442cc9f |
488 | Display form to collect information for book to create |
fce83e5f |
489 | |
d442cc9f |
490 | =cut |
fce83e5f |
491 | |
89d3dae9 |
492 | sub form_create :Chained('base') :PathPart('form_create') :Args(0) { |
d442cc9f |
493 | my ($self, $c) = @_; |
fce83e5f |
494 | |
d442cc9f |
495 | # Set the TT template to use |
0ed3df53 |
496 | $c->stash(template => 'books/form_create.tt2'); |
d442cc9f |
497 | } |
498 | |
72609296 |
499 | This action simply invokes a view containing a form to create a book. |
d442cc9f |
500 | |
1390ef0e |
501 | |
d442cc9f |
502 | =head2 Add a Template for the Form |
503 | |
504 | Open C<root/src/books/form_create.tt2> in your editor and enter: |
505 | |
506 | [% META title = 'Manual Form Book Create' -%] |
444d6b27 |
507 | |
8a7c5151 |
508 | <form method="post" action="[% c.uri_for('form_create_do') %]"> |
d442cc9f |
509 | <table> |
510 | <tr><td>Title:</td><td><input type="text" name="title"></td></tr> |
511 | <tr><td>Rating:</td><td><input type="text" name="rating"></td></tr> |
512 | <tr><td>Author ID:</td><td><input type="text" name="author_id"></td></tr> |
513 | </table> |
514 | <input type="submit" name="Submit" value="Submit"> |
515 | </form> |
516 | |
517 | Note that we have specified the target of the form data as |
518 | C<form_create_do>, the method created in the section that follows. |
519 | |
1390ef0e |
520 | |
d442cc9f |
521 | =head2 Add a Method to Process Form Values and Update Database |
522 | |
523 | Edit C<lib/MyApp/Controller/Books.pm> and add the following method to |
524 | save the form information to the database: |
525 | |
526 | =head2 form_create_do |
fce83e5f |
527 | |
d442cc9f |
528 | Take information from form and add to database |
fce83e5f |
529 | |
d442cc9f |
530 | =cut |
fce83e5f |
531 | |
89d3dae9 |
532 | sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) { |
d442cc9f |
533 | my ($self, $c) = @_; |
fce83e5f |
534 | |
d442cc9f |
535 | # Retrieve the values from the form |
536 | my $title = $c->request->params->{title} || 'N/A'; |
537 | my $rating = $c->request->params->{rating} || 'N/A'; |
538 | my $author_id = $c->request->params->{author_id} || '1'; |
fce83e5f |
539 | |
d442cc9f |
540 | # Create the book |
3b1fa91b |
541 | my $book = $c->model('DB::Book')->create({ |
d442cc9f |
542 | title => $title, |
543 | rating => $rating, |
544 | }); |
545 | # Handle relationship with author |
fce83e5f |
546 | $book->add_to_book_authors({author_id => $author_id}); |
547 | # Note: Above is a shortcut for this: |
548 | # $book->create_related('book_authors', {author_id => $author_id}); |
549 | |
0ed3df53 |
550 | # Store new model object in stash and set template |
551 | $c->stash(book => $book, |
552 | template => 'books/create_done.tt2'); |
d442cc9f |
553 | } |
554 | |
555 | |
556 | =head2 Test Out The Form |
557 | |
ee53cc71 |
558 | Notice that the server startup log reflects the two new chained methods |
559 | that we added: |
89d3dae9 |
560 | |
fbbb9084 |
561 | [debug] Loaded Chained actions: |
562 | .-------------------------------------+--------------------------------------. |
563 | | Path Spec | Private | |
564 | +-------------------------------------+--------------------------------------+ |
565 | | /books/form_create | /books/base (0) | |
566 | | | => /books/form_create | |
567 | | /books/form_create_do | /books/base (0) | |
568 | | | => /books/form_create_do | |
569 | | /books/url_create/*/*/* | /books/base (0) | |
570 | | | => /books/url_create | |
571 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
572 | |
d442cc9f |
573 | Point your browser to L<http://localhost:3000/books/form_create> and |
574 | enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an |
1390ef0e |
575 | author ID of 4. You should then see the output of the same |
d442cc9f |
576 | C<create_done.tt2> template seen in earlier examples. Finally, click |
577 | "Return to list" to view the full list of books. |
578 | |
579 | B<Note:> Having the user enter the primary key ID for the author is |
fce83e5f |
580 | obviously crude; we will address this concern with a drop-down list and |
22fe0f18 |
581 | add validation to our forms in |
582 | L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>. |
d442cc9f |
583 | |
584 | |
585 | =head1 A SIMPLE DELETE FEATURE |
586 | |
72609296 |
587 | Turning our attention to the Delete portion of CRUD, this section |
d442cc9f |
588 | illustrates some basic techniques that can be used to remove information |
589 | from the database. |
590 | |
591 | |
592 | =head2 Include a Delete Link in the List |
593 | |
ee53cc71 |
594 | Edit C<root/src/books/list.tt2> and update it to match the following |
595 | (two sections have changed: 1) the additional '<th>Links</th>' table |
22fe0f18 |
596 | header, and 2) the five lines for the Delete link near the bottom): |
d442cc9f |
597 | |
22fe0f18 |
598 | [% # This is a TT comment. -%] |
3dba69ab |
599 | |
22fe0f18 |
600 | [%- # Provide a title -%] |
d442cc9f |
601 | [% META title = 'Book List' -%] |
3dba69ab |
602 | |
22fe0f18 |
603 | [% # Note That the '-' at the beginning or end of TT code -%] |
604 | [% # "chomps" the whitespace/newline at that end of the -%] |
605 | [% # output (use View Source in browser to see the effect) -%] |
3dba69ab |
606 | |
22fe0f18 |
607 | [% # Some basic HTML with a loop to display books -%] |
d442cc9f |
608 | <table> |
609 | <tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr> |
610 | [% # Display each book in a table row %] |
611 | [% FOREACH book IN books -%] |
612 | <tr> |
613 | <td>[% book.title %]</td> |
614 | <td>[% book.rating %]</td> |
615 | <td> |
22fe0f18 |
616 | [% # NOTE: See Chapter 4 for a better way to do this! -%] |
d442cc9f |
617 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
618 | [% # loop in 'side effect notation' to load just the last names of the -%] |
55490817 |
619 | [% # authors into the list. Note that the 'push' TT vmethod doesn't return -%] |
d442cc9f |
620 | [% # a value, so nothing will be printed here. But, if you have something -%] |
22fe0f18 |
621 | [% # in TT that does return a value and you don't want it printed, you -%] |
6d97b973 |
622 | [% # 1) assign it to a bogus value, or -%] |
623 | [% # 2) use the CALL keyword to call it and discard the return value. -%] |
d442cc9f |
624 | [% tt_authors = [ ]; |
fce83e5f |
625 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
d442cc9f |
626 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
3b1fa91b |
627 | [% # Note the use of the TT filter "| html" to escape dangerous characters -%] |
628 | ([% tt_authors.size | html %]) |
d442cc9f |
629 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
3b1fa91b |
630 | [% tt_authors.join(', ') | html %] |
d442cc9f |
631 | </td> |
632 | <td> |
633 | [% # Add a link to delete a book %] |
22fe0f18 |
634 | <a href="[% |
635 | c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a> |
d442cc9f |
636 | </td> |
637 | </tr> |
638 | [% END -%] |
639 | </table> |
640 | |
55490817 |
641 | The additional code is obviously designed to add a new column to the |
72609296 |
642 | right side of the table with a C<Delete> "button" (for simplicity, links |
22fe0f18 |
643 | will be used instead of full HTML buttons; but, in practice, anything |
644 | that modifies data should be handled with a form sending a POST |
645 | request). |
fe01b24f |
646 | |
ee53cc71 |
647 | Also notice that we are using a more advanced form of C<uri_for> than we |
648 | have seen before. Here we use C<$c-E<gt>controller-E<gt>action_for> to |
649 | automatically generate a URI appropriate for that action based on the |
650 | method we want to link to while inserting the C<book.id> value into the |
651 | appropriate place. Now, if you ever change C<:PathPart('delete')> in |
22fe0f18 |
652 | your controller method to something like C<:PathPart('kill')>, then your |
653 | links will automatically update without any changes to your .tt2 |
654 | template file. As long as the name of your method does not change |
655 | (here, "delete"), then your links will still be correct. There are a |
656 | few shortcuts and options when using C<action_for()>: |
0416017e |
657 | |
658 | =over 4 |
659 | |
660 | =item * |
661 | |
ee53cc71 |
662 | If you are referring to a method in the current controller, you can use |
663 | C<$self-E<gt>action_for('_method_name_')>. |
0416017e |
664 | |
665 | =item * |
666 | |
ee53cc71 |
667 | If you are referring to a method in a different controller, you need to |
668 | include that controller's name as an argument to C<controller()>, as in |
0416017e |
669 | C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>. |
670 | |
671 | =back |
b2ad8bbd |
672 | |
55490817 |
673 | B<Note:> In practice you should B<never> use a GET request to delete a |
674 | record -- always use POST for actions that will modify data. We are |
c5d94181 |
675 | doing it here for illustrative and simplicity purposes only. |
d442cc9f |
676 | |
1390ef0e |
677 | |
994b66ad |
678 | =head2 Add a Common Method to Retrieve a Book for the Chain |
679 | |
ee53cc71 |
680 | As mentioned earlier, since we have a mixture of actions that operate on |
681 | a single book ID and others that do not, we should not have C<base> |
55490817 |
682 | capture the book ID, find the corresponding book in the database and |
683 | save it in the stash for later links in the chain. However, just |
ee53cc71 |
684 | because that logic does not belong in C<base> doesn't mean that we can't |
685 | create another location to centralize the book lookup code. In our |
686 | case, we will create a method called C<object> that will store the |
55490817 |
687 | specific book in the stash. Chains that always operate on a single |
688 | existing book can chain off this method, but methods such as |
ee53cc71 |
689 | C<url_create> that don't operate on an existing book can chain directly |
690 | off base. |
994b66ad |
691 | |
ee53cc71 |
692 | To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm> and |
693 | add the following code: |
994b66ad |
694 | |
e075db0c |
695 | =head2 object |
fce83e5f |
696 | |
e075db0c |
697 | Fetch the specified book object based on the book ID and store |
698 | it in the stash |
fce83e5f |
699 | |
e075db0c |
700 | =cut |
fce83e5f |
701 | |
994b66ad |
702 | sub object :Chained('base') :PathPart('id') :CaptureArgs(1) { |
fbbb9084 |
703 | # $id = primary key of book to delete |
994b66ad |
704 | my ($self, $c, $id) = @_; |
fce83e5f |
705 | |
994b66ad |
706 | # Find the book object and store it in the stash |
707 | $c->stash(object => $c->stash->{resultset}->find($id)); |
fce83e5f |
708 | |
994b66ad |
709 | # Make sure the lookup was successful. You would probably |
710 | # want to do something like this in a real app: |
711 | # $c->detach('/error_404') if !$c->stash->{object}; |
712 | die "Book $id not found!" if !$c->stash->{object}; |
fce83e5f |
713 | |
714 | # Print a message to the debug log |
715 | $c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***"); |
994b66ad |
716 | } |
717 | |
ee53cc71 |
718 | Now, any other method that chains off C<object> will automatically have |
719 | the appropriate book waiting for it in C<$c-E<gt>stash-E<gt>{object}>. |
994b66ad |
720 | |
994b66ad |
721 | |
d442cc9f |
722 | =head2 Add a Delete Action to the Controller |
723 | |
724 | Open C<lib/MyApp/Controller/Books.pm> in your editor and add the |
725 | following method: |
726 | |
1390ef0e |
727 | =head2 delete |
fce83e5f |
728 | |
d442cc9f |
729 | Delete a book |
fce83e5f |
730 | |
d442cc9f |
731 | =cut |
fce83e5f |
732 | |
994b66ad |
733 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
994b66ad |
734 | my ($self, $c) = @_; |
fce83e5f |
735 | |
994b66ad |
736 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
737 | # with related 'book_author' entries |
994b66ad |
738 | $c->stash->{object}->delete; |
fce83e5f |
739 | |
d442cc9f |
740 | # Set a status message to be displayed at the top of the view |
741 | $c->stash->{status_msg} = "Book deleted."; |
fce83e5f |
742 | |
d442cc9f |
743 | # Forward to the list action/method in this controller |
744 | $c->forward('list'); |
745 | } |
746 | |
55490817 |
747 | This method first deletes the book object saved by the C<object> method. |
ee53cc71 |
748 | However, it also removes the corresponding entry from the C<book_author> |
749 | table with a cascading delete. |
d442cc9f |
750 | |
751 | Then, rather than forwarding to a "delete done" page as we did with the |
752 | earlier create example, it simply sets the C<status_msg> to display a |
753 | notification to the user as the normal list view is rendered. |
754 | |
755 | The C<delete> action uses the context C<forward> method to return the |
756 | user to the book list. The C<detach> method could have also been used. |
757 | Whereas C<forward> I<returns> to the original action once it is |
758 | completed, C<detach> does I<not> return. Other than that, the two are |
759 | equivalent. |
760 | |
761 | |
762 | =head2 Try the Delete Feature |
763 | |
ee53cc71 |
764 | Once you save the Books controller, the server should automatically |
765 | restart. The C<delete> method should now appear in the "Loaded Chained |
766 | actions" section of the startup debug output: |
89d3dae9 |
767 | |
fbbb9084 |
768 | [debug] Loaded Chained actions: |
994b66ad |
769 | .-------------------------------------+--------------------------------------. |
770 | | Path Spec | Private | |
771 | +-------------------------------------+--------------------------------------+ |
772 | | /books/id/*/delete | /books/base (0) | |
773 | | | -> /books/object (1) | |
774 | | | => /books/delete | |
775 | | /books/form_create | /books/base (0) | |
776 | | | => /books/form_create | |
777 | | /books/form_create_do | /books/base (0) | |
778 | | | => /books/form_create_do | |
779 | | /books/url_create/*/*/* | /books/base (0) | |
780 | | | => /books/url_create | |
781 | '-------------------------------------+--------------------------------------' |
89d3dae9 |
782 | |
d442cc9f |
783 | Then point your browser to L<http://localhost:3000/books/list> and click |
55490817 |
784 | the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green |
785 | "Book deleted" status message should display at the top of the page, |
994b66ad |
786 | along with a list of the eight remaining books. You will also see the |
787 | cascading delete operation via the DBIC_TRACE output: |
788 | |
3b1fa91b |
789 | SELECT me.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6' |
790 | DELETE FROM book WHERE ( id = ? ): '6' |
d442cc9f |
791 | |
792 | |
793 | =head2 Fixing a Dangerous URL |
794 | |
55490817 |
795 | Note the URL in your browser once you have performed the deletion in the |
d442cc9f |
796 | prior step -- it is still referencing the delete action: |
797 | |
acbd7bdd |
798 | http://localhost:3000/books/id/6/delete |
d442cc9f |
799 | |
55490817 |
800 | What if the user were to press reload with this URL still active? In |
ee53cc71 |
801 | this case the redundant delete is harmless (although it does generate an |
802 | exception screen, it doesn't perform any undesirable actions on the |
22fe0f18 |
803 | application or database), but in other cases this could clearly lead to |
804 | trouble. |
d442cc9f |
805 | |
806 | We can improve the logic by converting to a redirect. Unlike |
ee53cc71 |
807 | C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform a |
808 | server-side alteration in the flow of processing, a redirect is a |
809 | client-side mechanism that causes the browser to issue an entirely new |
810 | request. As a result, the URL in the browser is updated to match the |
811 | destination of the redirection URL. |
d442cc9f |
812 | |
ee53cc71 |
813 | To convert the forward used in the previous section to a redirect, open |
814 | C<lib/MyApp/Controller/Books.pm> and edit the existing C<sub delete> |
815 | method to match: |
d442cc9f |
816 | |
994b66ad |
817 | =head2 delete |
fce83e5f |
818 | |
d442cc9f |
819 | Delete a book |
fce83e5f |
820 | |
d442cc9f |
821 | =cut |
fce83e5f |
822 | |
994b66ad |
823 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
824 | my ($self, $c) = @_; |
fce83e5f |
825 | |
994b66ad |
826 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
827 | # with related 'book_author' entries |
994b66ad |
828 | $c->stash->{object}->delete; |
fce83e5f |
829 | |
d442cc9f |
830 | # Set a status message to be displayed at the top of the view |
831 | $c->stash->{status_msg} = "Book deleted."; |
fce83e5f |
832 | |
0416017e |
833 | # Redirect the user back to the list page. Note the use |
834 | # of $self->action_for as earlier in this section (BasicCRUD) |
fbbb9084 |
835 | $c->response->redirect($c->uri_for($self->action_for('list'))); |
d442cc9f |
836 | } |
837 | |
838 | |
839 | =head2 Try the Delete and Redirect Logic |
840 | |
ee53cc71 |
841 | Point your browser to L<http://localhost:3000/books/list> (don't just |
842 | hit "Refresh" in your browser since we left the URL in an invalid state |
843 | in the previous section!) and delete the first copy of the remaining two |
844 | "TCPIP_Illustrated_Vol-2" books. The URL in your browser should return |
845 | to the L<http://localhost:3000/books/list> URL, so that is an |
846 | improvement, but notice that I<no green "Book deleted" status message is |
847 | displayed>. Because the stash is reset on every request (and a redirect |
848 | involves a second request), the C<status_msg> is cleared before it can |
22fe0f18 |
849 | be displayed. |
d442cc9f |
850 | |
851 | |
8a472b34 |
852 | =head2 Using 'uri_for' to Pass Query Parameters |
d442cc9f |
853 | |
ee53cc71 |
854 | There are several ways to pass information across a redirect. One option |
22fe0f18 |
855 | is to use the C<flash> technique that we will see in |
856 | L<Chapter 5|Catalyst::Manual::Tutorial::05_Authentication> of this |
ee53cc71 |
857 | tutorial; however, here we will pass the information via query |
858 | parameters on the redirect itself. Open |
859 | C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete> |
89d3dae9 |
860 | method to match the following: |
d442cc9f |
861 | |
55490817 |
862 | =head2 delete |
fce83e5f |
863 | |
d442cc9f |
864 | Delete a book |
fce83e5f |
865 | |
d442cc9f |
866 | =cut |
fce83e5f |
867 | |
994b66ad |
868 | sub delete :Chained('object') :PathPart('delete') :Args(0) { |
fbbb9084 |
869 | my ($self, $c) = @_; |
fce83e5f |
870 | |
994b66ad |
871 | # Use the book object saved by 'object' and delete it along |
3b1fa91b |
872 | # with related 'book_author' entries |
994b66ad |
873 | $c->stash->{object}->delete; |
fce83e5f |
874 | |
d442cc9f |
875 | # Redirect the user back to the list page with status msg as an arg |
55490817 |
876 | $c->response->redirect($c->uri_for($self->action_for('list'), |
d442cc9f |
877 | {status_msg => "Book deleted."})); |
878 | } |
879 | |
880 | This modification simply leverages the ability of C<uri_for> to include |
55490817 |
881 | an arbitrary number of name/value pairs in a hash reference. Next, we |
882 | need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a |
d442cc9f |
883 | query parameter: |
884 | |
1390ef0e |
885 | ... |
d442cc9f |
886 | <div id="content"> |
1390ef0e |
887 | [%# Status and error messages %] |
ee53cc71 |
888 | <span class="message">[% |
889 | status_msg || c.request.params.status_msg | html %]</span> |
1390ef0e |
890 | <span class="error">[% error_msg %]</span> |
891 | [%# This is where TT will stick all of your template's contents. -%] |
892 | [% content %] |
893 | </div><!-- end content --> |
894 | ... |
895 | |
ee53cc71 |
896 | Although the sample above only shows the C<content> div, leave the rest |
897 | of the file intact -- the only change we made to the C<wrapper.tt2> was |
22fe0f18 |
898 | to add "C<|| c.request.params.status_msg>" to the |
b3876d9e |
899 | C<E<lt>span class="message"E<gt>> line. Note that we definitely want |
900 | the "C<| html>" TT filter here since it would be easy for users to |
901 | modify the message on the URL and possibly inject harmful code into the |
902 | application if we left that off. |
d442cc9f |
903 | |
904 | |
905 | =head2 Try the Delete and Redirect With Query Param Logic |
906 | |
ee53cc71 |
907 | Point your browser to L<http://localhost:3000/books/list> (you should |
908 | now be able to safely hit "refresh" in your browser). Then delete the |
909 | remaining copy of "TCPIP_Illustrated_Vol-2". The green "Book deleted" |
a608d8ce |
910 | status message should return. But notice that you can now hit the |
ee53cc71 |
911 | "Reload" button in your browser and it just redisplays the book list |
912 | (and it correctly shows it without the "Book deleted" message on |
913 | redisplay). |
d442cc9f |
914 | |
22fe0f18 |
915 | B<NOTE:> Be sure to check out |
916 | L<Authentication|Catalyst::Manual::Tutorial::05_Authentication> where we |
917 | use an improved technique that is better suited to your real world |
918 | applications. |
d442cc9f |
919 | |
920 | |
1cde0fd6 |
921 | =head1 EXPLORING THE POWER OF DBIC |
922 | |
ee53cc71 |
923 | In this section we will explore some additional capabilities offered by |
22fe0f18 |
924 | L<DBIx::Class>. Although these features have relatively little to do |
925 | with Catalyst per se, you will almost certainly want to take advantage |
926 | of them in your applications. |
1cde0fd6 |
927 | |
928 | |
1cde0fd6 |
929 | =head2 Add Datetime Columns to Our Existing Books Table |
930 | |
ee53cc71 |
931 | Let's add two columns to our existing C<books> table to track when each |
932 | book was added and when each book is updated: |
1cde0fd6 |
933 | |
934 | $ sqlite3 myapp.db |
33f1d5d0 |
935 | sqlite> ALTER TABLE book ADD created TIMESTAMP; |
936 | sqlite> ALTER TABLE book ADD updated TIMESTAMP; |
3b1fa91b |
937 | sqlite> UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW'); |
938 | sqlite> SELECT * FROM book; |
f2bbfc36 |
939 | 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
940 | 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
941 | 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45 |
942 | 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
943 | 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
944 | 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1cde0fd6 |
945 | sqlite> .quit |
946 | $ |
947 | |
d5d7ee98 |
948 | Here are the commands without the surrounding sqlite3 prompt and output |
949 | in case you want to cut and paste them as a single block (but still |
950 | start sqlite3 before you paste these in): |
951 | |
952 | ALTER TABLE book ADD created TIMESTAMP; |
953 | ALTER TABLE book ADD updated TIMESTAMP; |
954 | UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW'); |
955 | SELECT * FROM book; |
956 | |
ee53cc71 |
957 | This will modify the C<books> table to include the two new fields and |
958 | populate those fields with the current time. |
1cde0fd6 |
959 | |
acbd7bdd |
960 | |
a46b474e |
961 | =head2 Update DBIx::Class to Automatically Handle the Datetime Columns |
1cde0fd6 |
962 | |
ee53cc71 |
963 | Next, we should re-run the DBIC helper to update the Result Classes with |
964 | the new fields: |
1cde0fd6 |
965 | |
966 | $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \ |
b66dd084 |
967 | create=static components=TimeStamp dbi:SQLite:myapp.db \ |
968 | on_connect_do="PRAGMA foreign_keys = ON" |
1cde0fd6 |
969 | exists "/root/dev/MyApp/script/../lib/MyApp/Model" |
970 | exists "/root/dev/MyApp/script/../t" |
971 | Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ... |
972 | Schema dump completed. |
973 | exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm" |
974 | |
ee53cc71 |
975 | Notice that we modified our use of the helper slightly: we told it to |
976 | include the L<DBIx::Class::TimeStamp> in the C<load_components> line of |
977 | the Result Classes. |
1cde0fd6 |
978 | |
ee53cc71 |
979 | If you open C<lib/MyApp/Schema/Result/Book.pm> in your editor you should |
980 | see that the C<created> and C<updated> fields are now included in the |
981 | call to C<add_columns()>. However, also notice that the C<many_to_many> |
982 | relationships we manually added below the "C<# DO NOT MODIFY...>" line |
983 | were automatically preserved. |
1cde0fd6 |
984 | |
d5d7ee98 |
985 | While we C<lib/MyApp/Schema/Result/Book.pm> open, let's update it with |
986 | some additional information to have DBIC automatically handle the |
987 | updating of these two fields for us. Insert the following code at the |
988 | bottom of the file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" |
989 | line and B<above> the C<1;> on the last line): |
1cde0fd6 |
990 | |
991 | # |
992 | # Enable automatic date handling |
993 | # |
994 | __PACKAGE__->add_columns( |
995 | "created", |
33f1d5d0 |
996 | { data_type => 'timestamp', set_on_create => 1 }, |
1cde0fd6 |
997 | "updated", |
33f1d5d0 |
998 | { data_type => 'timestamp', set_on_create => 1, set_on_update => 1 }, |
55490817 |
999 | ); |
1cde0fd6 |
1000 | |
ee53cc71 |
1001 | This will override the definition for these fields that Schema::Loader |
1002 | placed at the top of the file. The C<set_on_create> and |
1003 | C<set_on_update> options will cause DBIx::Class to automatically update |
1004 | the timestamps in these columns whenever a row is created or modified. |
1cde0fd6 |
1005 | |
22fe0f18 |
1006 | B<Note> that adding the lines above will cause the development server to |
1007 | automatically restart if you are running it with the "-r" option. In |
1008 | other words, the development server is smart enough to restart not only |
1009 | for code under the C<MyApp/Controller/>, C<MyApp/Model/>, and |
1010 | C<MyApp/View/> directories, but also under other directions such as our |
1011 | "external DBIC model" in C<MyApp/Schema/>. However, also note that it's |
1012 | smart enough to B<not> restart when you edit your C<.tt2> files under |
1013 | C<root/>. |
1014 | |
1cde0fd6 |
1015 | Then enter the following URL into your web browser: |
1016 | |
1017 | http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 |
1018 | |
22fe0f18 |
1019 | You should get the same "Book Created" screen we saw earlier. However, if |
ee53cc71 |
1020 | you now use the sqlite3 command-line tool to dump the C<books> table, |
1021 | you will see that the new book we added has an appropriate date and time |
1022 | entered for it (see the last line in the listing below): |
1cde0fd6 |
1023 | |
444d6b27 |
1024 | $ sqlite3 myapp.db "select * from book" |
f2bbfc36 |
1025 | 1|CCSP SNRS Exam Certification Guide|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1026 | 2|TCP/IP Illustrated, Volume 1|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1027 | 3|Internetworking with TCP/IP Vol.1|4|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1028 | 4|Perl Cookbook|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1029 | 5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1030 | 9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45 |
1031 | 10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42 |
1cde0fd6 |
1032 | |
55490817 |
1033 | Notice in the debug log that the SQL DBIC generated has changed to |
1cde0fd6 |
1034 | incorporate the datetime logic: |
1035 | |
2a6eb5f9 |
1036 | INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ): |
f2bbfc36 |
1037 | '2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42' |
2a6eb5f9 |
1038 | INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10' |
1cde0fd6 |
1039 | |
1040 | |
1041 | =head2 Create a ResultSet Class |
1042 | |
444d6b27 |
1043 | An often overlooked but extremely powerful features of DBIC is that it |
55490817 |
1044 | allows you to supply your own subclasses of C<DBIx::Class::ResultSet>. |
22fe0f18 |
1045 | This can be used to pull complex and unsightly "query code" out of your |
1cde0fd6 |
1046 | controllers and encapsulate it in a method of your ResultSet Class. |
ee53cc71 |
1047 | These "canned queries" in your ResultSet Class can then be invoked via a |
1048 | single call, resulting in much cleaner and easier to read controller |
22fe0f18 |
1049 | code (or View code, if that's where you want to call it). |
1cde0fd6 |
1050 | |
55490817 |
1051 | To illustrate the concept with a fairly simple example, let's create a |
ee53cc71 |
1052 | method that returns books added in the last 10 minutes. Start by making |
1053 | a directory where DBIx::Class will look for our ResultSet Class: |
1cde0fd6 |
1054 | |
444d6b27 |
1055 | $ mkdir lib/MyApp/Schema/ResultSet |
1cde0fd6 |
1056 | |
3b1fa91b |
1057 | Then open C<lib/MyApp/Schema/ResultSet/Book.pm> and enter the following: |
1cde0fd6 |
1058 | |
3b1fa91b |
1059 | package MyApp::Schema::ResultSet::Book; |
fce83e5f |
1060 | |
1cde0fd6 |
1061 | use strict; |
1062 | use warnings; |
1063 | use base 'DBIx::Class::ResultSet'; |
fce83e5f |
1064 | |
1cde0fd6 |
1065 | =head2 created_after |
fce83e5f |
1066 | |
1cde0fd6 |
1067 | A predefined search for recently added books |
fce83e5f |
1068 | |
1cde0fd6 |
1069 | =cut |
fce83e5f |
1070 | |
1cde0fd6 |
1071 | sub created_after { |
fadc4ae7 |
1072 | my ($self, $datetime) = @_; |
fce83e5f |
1073 | |
b66dd084 |
1074 | my $date_str = $self->result_source->schema->storage |
fadc4ae7 |
1075 | ->datetime_parser->format_datetime($datetime); |
fce83e5f |
1076 | |
fadc4ae7 |
1077 | return $self->search({ |
1078 | created => { '>' => $date_str } |
1079 | }); |
1cde0fd6 |
1080 | } |
fce83e5f |
1081 | |
1cde0fd6 |
1082 | 1; |
1083 | |
1cde0fd6 |
1084 | Then add the following method to the C<lib/MyApp/Controller/Books.pm>: |
1085 | |
1086 | =head2 list_recent |
fce83e5f |
1087 | |
1cde0fd6 |
1088 | List recently created books |
fce83e5f |
1089 | |
1cde0fd6 |
1090 | =cut |
fce83e5f |
1091 | |
1cde0fd6 |
1092 | sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) { |
1093 | my ($self, $c, $mins) = @_; |
fce83e5f |
1094 | |
1cde0fd6 |
1095 | # Retrieve all of the book records as book model objects and store in the |
1096 | # stash where they can be accessed by the TT template, but only |
1097 | # retrieve books created within the last $min number of minutes |
0ed3df53 |
1098 | $c->stash(books => [$c->model('DB::Book') |
1099 | ->created_after(DateTime->now->subtract(minutes => $mins))]); |
fce83e5f |
1100 | |
1cde0fd6 |
1101 | # Set the TT template to use. You will almost always want to do this |
1102 | # in your action methods (action methods respond to user input in |
1103 | # your controllers). |
0ed3df53 |
1104 | $c->stash(template => 'books/list.tt2'); |
1cde0fd6 |
1105 | } |
1106 | |
ee53cc71 |
1107 | Now try different values for the "minutes" argument (the final number |
1108 | value) using the URL C<http://localhost:3000/books/list_recent/_#_> in |
1109 | your browser. For example, this would list all books added in the last |
1110 | fifteen minutes: |
1cde0fd6 |
1111 | |
1112 | http://localhost:3000/books/list_recent/15 |
1113 | |
ee53cc71 |
1114 | Depending on how recently you added books, you might want to try a |
1115 | higher or lower value for the minutes. |
1cde0fd6 |
1116 | |
1117 | |
1118 | =head2 Chaining ResultSets |
1119 | |
22fe0f18 |
1120 | One of the most helpful and powerful features in C<DBIx::Class> is that |
1121 | it allows you to "chain together" a series of queries (note that this |
1122 | has nothing to do with the "Chained Dispatch" for Catalyst that we were |
1123 | discussing earlier). Because each ResultSet method returns another |
1124 | ResultSet, you can take an initial query and immediately feed that into |
1125 | a second query (and so on for as many queries you need). Note that no |
1126 | matter how many ResultSets you chain together, the database itself will |
1127 | not be hit until you use a method that attempts to access the data. And, |
1128 | because this technique carries over to the ResultSet Class feature we |
ee53cc71 |
1129 | implemented in the previous section for our "canned search", we can |
1130 | combine the two capabilities. For example, let's add an action to our |
1131 | C<Books> controller that lists books that are both recent I<and> have |
1132 | "TCP" in the title. Open up C<lib/MyApp/Controller/Books.pm> and add |
1133 | the following method: |
1cde0fd6 |
1134 | |
acbd7bdd |
1135 | =head2 list_recent_tcp |
fce83e5f |
1136 | |
1cde0fd6 |
1137 | List recently created books |
fce83e5f |
1138 | |
1cde0fd6 |
1139 | =cut |
fce83e5f |
1140 | |
1cde0fd6 |
1141 | sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) { |
1142 | my ($self, $c, $mins) = @_; |
fce83e5f |
1143 | |
1cde0fd6 |
1144 | # Retrieve all of the book records as book model objects and store in the |
1145 | # stash where they can be accessed by the TT template, but only |
1146 | # retrieve books created within the last $min number of minutes |
1147 | # AND that have 'TCP' in the title |
22fe0f18 |
1148 | $c->stash(books => [ |
1149 | $c->model('DB::Book') |
1150 | ->created_after(DateTime->now->subtract(minutes => $mins)) |
1151 | ->search({title => {'like', '%TCP%'}}) |
1152 | ]); |
fce83e5f |
1153 | |
1cde0fd6 |
1154 | # Set the TT template to use. You will almost always want to do this |
1155 | # in your action methods (action methods respond to user input in |
1156 | # your controllers). |
0ed3df53 |
1157 | $c->stash(template => 'books/list.tt2'); |
1cde0fd6 |
1158 | } |
1159 | |
f2bbfc36 |
1160 | To try this out, enter the following URL into your browser: |
1cde0fd6 |
1161 | |
1162 | http://localhost:3000/books/list_recent_tcp/100 |
1163 | |
55490817 |
1164 | And you should get a list of books added in the last 100 minutes that |
1165 | contain the string "TCP" in the title. However, if you look at all |
ee53cc71 |
1166 | books within the last 100 minutes, you should get a longer list (again, |
1167 | you might have to adjust the number of minutes depending on how recently |
1168 | you added books to your database): |
1cde0fd6 |
1169 | |
1170 | http://localhost:3000/books/list_recent/100 |
1171 | |
55490817 |
1172 | Take a look at the DBIC_TRACE output in the development server log for |
1cde0fd6 |
1173 | the first URL and you should see something similar to the following: |
1174 | |
fce83e5f |
1175 | SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me |
f2bbfc36 |
1176 | WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32' |
1cde0fd6 |
1177 | |
ee53cc71 |
1178 | However, let's not pollute our controller code with this raw "TCP" query |
1179 | -- it would be cleaner to encapsulate that code in a method on our |
1180 | ResultSet Class. To do this, open C<lib/MyApp/Schema/ResultSet/Book.pm> |
1181 | and add the following method: |
1cde0fd6 |
1182 | |
1183 | =head2 title_like |
fce83e5f |
1184 | |
1cde0fd6 |
1185 | A predefined search for books with a 'LIKE' search in the string |
fce83e5f |
1186 | |
1cde0fd6 |
1187 | =cut |
fce83e5f |
1188 | |
1cde0fd6 |
1189 | sub title_like { |
fadc4ae7 |
1190 | my ($self, $title_str) = @_; |
fce83e5f |
1191 | |
fadc4ae7 |
1192 | return $self->search({ |
1193 | title => { 'like' => "%$title_str%" } |
1194 | }); |
1cde0fd6 |
1195 | } |
1196 | |
55490817 |
1197 | We defined the search string as C<$title_str> to make the method more |
1198 | flexible. Now update the C<list_recent_tcp> method in |
1199 | C<lib/MyApp/Controller/Books.pm> to match the following (we have |
1200 | replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line |
1cde0fd6 |
1201 | shown here -- the rest of the method should be the same): |
1202 | |
1203 | =head2 list_recent_tcp |
fce83e5f |
1204 | |
1cde0fd6 |
1205 | List recently created books |
fce83e5f |
1206 | |
1cde0fd6 |
1207 | =cut |
fce83e5f |
1208 | |
1cde0fd6 |
1209 | sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) { |
1210 | my ($self, $c, $mins) = @_; |
fce83e5f |
1211 | |
1cde0fd6 |
1212 | # Retrieve all of the book records as book model objects and store in the |
1213 | # stash where they can be accessed by the TT template, but only |
1214 | # retrieve books created within the last $min number of minutes |
1215 | # AND that have 'TCP' in the title |
22fe0f18 |
1216 | $c->stash(books => [ |
1217 | $c->model('DB::Book') |
1218 | ->created_after(DateTime->now->subtract(minutes => $mins)) |
1219 | ->title_like('TCP') |
1220 | ]); |
fce83e5f |
1221 | |
1cde0fd6 |
1222 | # Set the TT template to use. You will almost always want to do this |
1223 | # in your action methods (action methods respond to user input in |
1224 | # your controllers). |
0ed3df53 |
1225 | $c->stash(template => 'books/list.tt2'); |
1cde0fd6 |
1226 | } |
1227 | |
ee53cc71 |
1228 | Try out the C<list_recent_tcp> and C<list_recent> URLs as we did above. |
1229 | They should work just the same, but our code is obviously cleaner and |
1230 | more modular, while also being more flexible at the same time. |
1cde0fd6 |
1231 | |
1232 | |
1233 | =head2 Adding Methods to Result Classes |
1234 | |
ee53cc71 |
1235 | In the previous two sections we saw a good example of how we could use |
1236 | DBIx::Class ResultSet Classes to clean up our code for an entire query |
1237 | (for example, our "canned searches" that filtered the entire query). We |
1238 | can do a similar improvement when working with individual rows as well. |
1239 | Whereas the ResultSet construct is used in DBIC to correspond to an |
1240 | entire query, the Result Class construct is used to represent a row. |
1241 | Therefore, we can add row-specific "helper methods" to our Result |
1242 | Classes stored in C<lib/MyApp/Schema/Result/>. For example, open |
1243 | C<lib/MyApp/Schema/Result/Author.pm> and add the following method (as |
a46b474e |
1244 | always, it must be above the closing "C<1;>"): |
1cde0fd6 |
1245 | |
1246 | # |
a608d8ce |
1247 | # Row-level helper methods |
1cde0fd6 |
1248 | # |
1249 | sub full_name { |
1250 | my ($self) = @_; |
fce83e5f |
1251 | |
1cde0fd6 |
1252 | return $self->first_name . ' ' . $self->last_name; |
1253 | } |
1254 | |
ee53cc71 |
1255 | This will allow us to conveniently retrieve both the first and last name |
1256 | for an author in one shot. Now open C<root/src/books/list.tt2> and |
1257 | change the definition of C<tt_authors> from this: |
1cde0fd6 |
1258 | |
acbd7bdd |
1259 | ... |
1cde0fd6 |
1260 | [% tt_authors = [ ]; |
fce83e5f |
1261 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
acbd7bdd |
1262 | ... |
1cde0fd6 |
1263 | |
1264 | to: |
1265 | |
acbd7bdd |
1266 | ... |
1cde0fd6 |
1267 | [% tt_authors = [ ]; |
fce83e5f |
1268 | tt_authors.push(author.full_name) FOREACH author = book.authors %] |
acbd7bdd |
1269 | ... |
1cde0fd6 |
1270 | |
ee53cc71 |
1271 | (Only C<author.last_name> was changed to C<author.full_name> -- the rest |
1272 | of the file should remain the same.) |
1cde0fd6 |
1273 | |
f2bbfc36 |
1274 | Now go to the standard book list URL: |
1cde0fd6 |
1275 | |
1276 | http://localhost:3000/books/list |
1277 | |
55490817 |
1278 | The "Author(s)" column will now contain both the first and last name. |
ee53cc71 |
1279 | And, because the concatenation logic was encapsulated inside our Result |
1280 | Class, it keeps the code inside our TT template nice and clean |
55490817 |
1281 | (remember, we want the templates to be as close to pure HTML markup as |
1282 | possible). Obviously, this capability becomes even more useful as you |
0ed0d69a |
1283 | use it to remove even more complicated row-specific logic from your |
1cde0fd6 |
1284 | templates! |
1285 | |
1286 | |
fce83e5f |
1287 | =head2 Moving Complicated View Code to the Model |
1288 | |
ee53cc71 |
1289 | The previous section illustrated how we could use a Result Class method |
1290 | to print the full names of the authors without adding any extra code to |
1291 | our view, but it still left us with a fairly ugly mess (see |
fce83e5f |
1292 | C<root/src/books/list.tt2>): |
1293 | |
1294 | ... |
1295 | <td> |
1296 | [% # NOTE: See Chapter 4 for a better way to do this! -%] |
1297 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
1298 | [% # loop in 'side effect notation' to load just the last names of the -%] |
1299 | [% # authors into the list. Note that the 'push' TT vmethod does not print -%] |
1300 | [% # a value, so nothing will be printed here. But, if you have something -%] |
1301 | [% # in TT that does return a method and you don't want it printed, you -%] |
1302 | [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%] |
1303 | [% # call it and discard the return value. -%] |
1304 | [% tt_authors = [ ]; |
1305 | tt_authors.push(author.full_name) FOREACH author = book.authors %] |
1306 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
1307 | [% # Note the use of the TT filter "| html" to escape dangerous characters -%] |
1308 | ([% tt_authors.size | html %]) |
1309 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
1310 | [% tt_authors.join(', ') | html %] |
1311 | </td> |
1312 | ... |
1313 | |
ee53cc71 |
1314 | Let's combine some of the techniques used earlier in this section to |
1315 | clean this up. First, let's add a method to our Book Result Class to |
1316 | return the number of authors for a book. Open |
fce83e5f |
1317 | C<lib/MyApp/Schema/Result/Book.pm> and add the following method: |
1318 | |
444d6b27 |
1319 | =head2 author_count |
1320 | |
1321 | Return the number of authors for the current book |
1322 | |
fce83e5f |
1323 | =cut |
1324 | |
1325 | sub author_count { |
1326 | my ($self) = @_; |
1327 | |
1328 | # Use the 'many_to_many' relationship to fetch all of the authors for the current |
1329 | # and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT |
1330 | return $self->authors->count; |
1331 | } |
1332 | |
1333 | Next, let's add a method to return a list of authors for a book to the |
1334 | same C<lib/MyApp/Schema/Result/Book.pm> file: |
1335 | |
1336 | =head2 author_list |
1337 | |
1338 | Return a comma-separated list of authors for the current book |
1339 | |
1340 | =cut |
1341 | |
1342 | sub author_list { |
1343 | my ($self) = @_; |
1344 | |
1345 | # Loop through all authors for the current book, calling all the 'full_name' |
1346 | # Result Class method for each |
1347 | my @names; |
1348 | foreach my $author ($self->authors) { |
1349 | push(@names, $author->full_name); |
1350 | } |
1351 | |
1352 | return join(', ', @names); |
1353 | } |
1354 | |
ee53cc71 |
1355 | This method loops through each author, using the C<full_name> Result |
1356 | Class method we added to C<lib/MyApp/Schema/Result/Author.pm> in the |
fce83e5f |
1357 | prior section. |
1358 | |
1359 | Using these two methods, we can simplify our TT code. Open |
1360 | C<root/src/books/list.tt2> and update the "Author(s)" table cell to |
1361 | match the following: |
1362 | |
1363 | ... |
1364 | <td> |
1365 | [% # Print count and author list using Result Class methods -%] |
1366 | ([% book.author_count | html %]) [% book.author_list | html %] |
1367 | </td> |
1368 | ... |
1369 | |
ee53cc71 |
1370 | Although most of the code we removed comprised comments, the overall |
1371 | effect is dramatic... because our view code is so simple, we don't need |
22fe0f18 |
1372 | huge comments to clue people in to the gist of our code. The view code |
ee53cc71 |
1373 | is now self-documenting and readable enough that you could probably get |
22fe0f18 |
1374 | by with no comments at all. All of the "complex" work is being done in |
ee53cc71 |
1375 | our Result Class methods (and, because we have broken the code into |
1376 | nice, modular chunks, the Result Class code is hardly something you |
f2bbfc36 |
1377 | would call complex). |
fce83e5f |
1378 | |
ee53cc71 |
1379 | As we saw in this section, always strive to keep your view AND |
1380 | controller code as simple as possible by pulling code out into your |
22fe0f18 |
1381 | model objects. Because L<DBIx::Class> can be easily extended in so many |
ee53cc71 |
1382 | ways, it's an excellent to way accomplish this objective. It will make |
1383 | your code cleaner, easier to write, less error-prone, and easier to |
1384 | debug and maintain. |
fce83e5f |
1385 | |
ee53cc71 |
1386 | Before you conclude this section, hit Refresh in your browser... the |
1387 | output should be the same even though the backend code has been trimmed |
1388 | down. |
444d6b27 |
1389 | |
fce83e5f |
1390 | |
24acc5d7 |
1391 | You can jump to the next chapter of the tutorial here: |
1392 | L<Authentication|Catalyst::Manual::Tutorial::05_Authentication> |
1393 | |
1394 | |
d442cc9f |
1395 | =head1 AUTHOR |
1396 | |
1397 | Kennedy Clark, C<hkclark@gmail.com> |
1398 | |
53243324 |
1399 | Feel free to contact the author for any errors or suggestions, but the |
1400 | best way to report issues is via the CPAN RT Bug system at |
1401 | <https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>. |
1402 | |
1403 | The most recent version of the Catalyst Tutorial can be found at |
59884771 |
1404 | L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>. |
d442cc9f |
1405 | |
ec3ef4ad |
1406 | Copyright 2006-2010, Kennedy Clark, under the |
1407 | Creative Commons Attribution Share-Alike License Version 3.0 |
95674086 |
1408 | (L<http://creativecommons.org/licenses/by-sa/3.0/us/>). |