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1 | =head1 NAME |
2 | |
3 | Catalyst::Manual::Tutorial::MoreCatalystBasics - Catalyst Tutorial - Part 3: More Catalyst Application Development Basics |
4 | |
5 | |
6 | =head1 OVERVIEW |
7 | |
8 | This is B<Part 3 of 10> for the Catalyst tutorial. |
9 | |
10 | L<Tutorial Overview|Catalyst::Manual::Tutorial> |
11 | |
12 | =over 4 |
13 | |
14 | =item 1 |
15 | |
16 | L<Introduction|Catalyst::Manual::Tutorial::Intro> |
17 | |
18 | =item 2 |
19 | |
20 | L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics> |
21 | |
22 | =item 3 |
23 | |
24 | B<More Catalyst Basics> |
25 | |
26 | =item 4 |
27 | |
28 | L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD> |
29 | |
30 | =item 5 |
31 | |
32 | L<Authentication|Catalyst::Manual::Tutorial::Authentication> |
33 | |
34 | =item 6 |
35 | |
36 | L<Authorization|Catalyst::Manual::Tutorial::Authorization> |
37 | |
38 | =item 7 |
39 | |
40 | L<Debugging|Catalyst::Manual::Tutorial::Debugging> |
41 | |
42 | =item 8 |
43 | |
44 | L<Testing|Catalyst::Manual::Tutorial::Testing> |
45 | |
46 | =item 9 |
47 | |
48 | L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD> |
49 | |
50 | =item 10 |
51 | |
52 | L<Appendices|Catalyst::Manual::Tutorial::Appendices> |
53 | |
54 | =back |
55 | |
56 | |
57 | =head1 DESCRIPTION |
58 | |
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59 | This part of the tutorial builds on the work done in Part 2 to explore |
60 | some features that are more typical of "real world" web applications. |
61 | From this part of the tutorial onward, we will be building a simple |
62 | book database application. Although the application will be too |
63 | limited to be of use to anyone, it should provide a basic environment |
64 | where we can explore a variety of features used in virtually all web |
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65 | applications. |
66 | |
67 | You can checkout the source code for this example from the catalyst |
68 | subversion repository as per the instructions in |
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69 | L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>. |
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70 | |
71 | |
72 | =head1 CREATE A NEW APPLICATION |
73 | |
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74 | The remainder of the tutorial will build an application called C<MyApp>. |
75 | First use the Catalyst C<catalyst.pl> script to initialize the framework |
76 | for the C<MyApp> application (make sure you aren't still inside the |
77 | directory of the C<Hello> application from the previous part of the |
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78 | tutorial): |
79 | |
80 | $ catalyst.pl MyApp |
81 | created "MyApp" |
82 | created "MyApp/script" |
83 | created "MyApp/lib" |
84 | created "MyApp/root" |
85 | ... |
86 | created "MyApp/script/myapp_create.pl" |
87 | $ cd MyApp |
88 | |
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89 | This creates a similar skeletal structure to what we saw in Part 2 of |
90 | the tutorial, except with C<MyApp> and C<myapp> substituted for |
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91 | C<Hello> and C<hello>. |
92 | |
93 | |
94 | =head1 EDIT THE LIST OF CATALYST PLUGINS |
95 | |
96 | One of the greatest benefits of Catalyst is that it has such a large |
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97 | library of plugins and base classes available. Plugins are used to |
98 | seamlessly integrate existing Perl modules into the overall Catalyst |
99 | framework. In general, they do this by adding additional methods to the |
100 | C<context> object (generally written as C<$c>) that Catalyst passes to |
101 | every component throughout the framework. |
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102 | |
103 | By default, Catalyst enables three plugins/flags: |
104 | |
105 | =over 4 |
106 | |
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107 | =item * |
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108 | |
109 | C<-Debug> Flag |
110 | |
111 | Enables the Catalyst debug output you saw when we started the |
112 | C<script/myapp_server.pl> development server earlier. You can remove |
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113 | this item when you place your application into production. |
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114 | |
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115 | As you may have noticed, C<-Debug> is not a plugin, but a I<flag>. |
116 | Although most of the items specified on the C<__PACKAGE__-E<gt>setup> |
117 | line of your application class will be plugins, Catalyst supports a |
118 | limited number of flag options (of these, C<-Debug> is the most |
119 | common). See the documentation for C<Catalyst.pm> to get details on |
120 | other flags (currently C<-Engine>, C<-Home>, and C<-Log>). |
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121 | |
122 | If you prefer, you can use the C<$c-E<gt>debug> method to enable debug |
123 | messages. |
124 | |
125 | B<TIP>: Depending on your needs, it can be helpful to permanently |
126 | remove C<-Debug> from C<lib/MyApp.pm> and then use the C<-d> option |
127 | to C<script/myapp_server.pl> to re-enable it just for the development |
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128 | server. We will not be using that approach in the tutorial, but feel |
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129 | free to make use of it in your own projects. |
130 | |
131 | =item * |
132 | |
133 | L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> |
134 | |
135 | C<ConfigLoader> provides an automatic way to load configurable |
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136 | parameters for your application from a central |
137 | L<Config::General|Config::General> file (versus having the values |
138 | hard-coded inside your Perl modules). Config::General uses syntax |
139 | very similar to Apache configuration files. We will see how to use |
140 | this feature of Catalyst during the authentication and authorization |
141 | sections (Part 5 and Part 6). |
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142 | |
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143 | B<IMPORTANT NOTE:> If you are using a version of |
144 | L<Catalyst::Devel|Catalyst::Devel> prior to version 1.06, you need to |
145 | be aware that Catalyst changed from a default format of YAML to the |
146 | more straightforward C<Config::General> format. This tutorial use the |
147 | newer C<myapp.conf> configuration file for C<Config::General> instead |
148 | of C<myapp.yml> for YAML. However, Catalyst has long supported both |
149 | formats and Catalyst will automatically use either C<myapp.conf> or |
150 | C<myapp.yml> (or any other format supported by |
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151 | L<Catalyst::Plugin::ConfigLoader|Catalyst::Plugin::ConfigLoader> and |
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152 | L<Config::Any|Config::Any>). If you are using a versions of |
153 | Catalyst::Devel prior to 1.06, you can convert to the newer format by |
154 | simply creating the C<myapp.yml> file manually and deleting |
155 | C<myapp.yml>. The default contents of C<myapp.conf> should only |
156 | consist of one line: C<name MyApp>. |
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157 | |
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158 | B<TIP>: This script can be useful for converting between configuration |
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159 | formats: |
160 | |
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161 | perl -Ilib -e 'use MyApp; use Config::General; |
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162 | Config::General->new->save_file("myapp.conf", MyApp->config);' |
163 | |
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164 | B<NOTE:> The default C<myapp.conf> should look like: |
165 | |
166 | name MyApp |
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167 | |
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168 | =item * |
169 | |
170 | L<Catalyst::Plugin::Static::Simple|Catalyst::Plugin::Static::Simple> |
171 | |
172 | C<Static::Simple> provides an easy method of serving static content such |
173 | as images and CSS files under the development server. |
174 | |
175 | =back |
176 | |
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177 | For out application, we want to add one new plugin into the mix. To |
178 | do this, edit C<lib/MyApp.pm> (this file is generally referred to as |
179 | your I<application class>) and delete the line with: |
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180 | |
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181 | __PACKAGE__->setup(qw/-Debug ConfigLoader Static::Simple/); |
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182 | |
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183 | Then replace it with: |
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184 | |
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185 | __PACKAGE__->setup(qw/ |
186 | -Debug |
187 | ConfigLoader |
188 | Static::Simple |
189 | |
190 | StackTrace |
191 | /); |
192 | |
193 | This tells Catalyst to start using one new plugin, |
194 | L<Catalyst::Plugin::StackTrace|Catalyst::Plugin::StackTrace>, to add a |
195 | stack trace to the standard Catalyst "debug screen" (the screen |
196 | Catalyst sends to your browser when an error occurs). Be aware that |
197 | L<StackTrace|Catalyst::Plugin::StackTrace> output appears in your |
198 | browser, not in the console window from which you're running your |
199 | application, which is where logging output usually goes. |
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200 | |
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201 | B<Notes:> |
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202 | |
203 | =over 4 |
204 | |
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205 | =item * |
206 | |
207 | C<__PACKAGE__> is just a shorthand way of referencing the name of the |
208 | package where it is used. Therefore, in C<MyApp.pm>, C<__PACKAGE__> |
209 | is equivalent to C<MyApp>. |
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210 | |
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211 | =item * |
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212 | |
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213 | You will want to disable L<StackTrace|Catalyst::Plugin::StackTrace> |
214 | before you put your application into production, but it can be helpful |
215 | during development. |
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216 | |
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217 | =item * |
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218 | |
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219 | When specifying plugins on the C<__PACKAGE__-E<gt>setup> line, you can |
220 | omit C<Catalyst::Plugin::> from the name. Additionally, you can |
221 | spread the plugin names across multiple lines as shown here, or place |
222 | them all on one (or more) lines as with the default configuration. |
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223 | |
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224 | =back |
225 | |
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226 | |
227 | =head1 CREATE A CATALYST CONTROLLER |
228 | |
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229 | As discussed earlier, controllers are where you write methods that |
230 | interact with user input. Typically, controller methods respond to |
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231 | C<GET> and C<POST> messages from the user's web browser. |
232 | |
233 | Use the Catalyst C<create> script to add a controller for book-related |
234 | actions: |
235 | |
236 | $ script/myapp_create.pl controller Books |
237 | exists "/home/me/MyApp/script/../lib/MyApp/Controller" |
238 | exists "/home/me/MyApp/script/../t" |
239 | created "/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm" |
240 | created "/home/me/MyApp/script/../t/controller_Books.t" |
241 | |
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242 | Then edit C<lib/MyApp/Controller/Books.pm> (as discussed in Part 2 of |
243 | the Tutorial, Catalyst has a separate directory under C<lib/MyApp> for |
244 | each of the three parts of MVC: C<Model>, C<View>, and C<Controller>) |
245 | and add the following method to the controller: |
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246 | |
247 | =head2 list |
248 | |
249 | Fetch all book objects and pass to books/list.tt2 in stash to be displayed |
250 | |
251 | =cut |
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252 | |
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253 | sub list : Local { |
254 | # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst |
255 | # 'Context' that's used to 'glue together' the various components |
256 | # that make up the application |
257 | my ($self, $c) = @_; |
258 | |
259 | # Retrieve all of the book records as book model objects and store in the |
260 | # stash where they can be accessed by the TT template |
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261 | # $c->stash->{books} = [$c->model('DB::Books')->all]; |
262 | # But, for now, use this code until we create the model later |
263 | $c->stash->{books} = ''; |
264 | |
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265 | # Set the TT template to use. You will almost always want to do this |
266 | # in your action methods (action methods respond to user input in |
267 | # your controllers). |
268 | $c->stash->{template} = 'books/list.tt2'; |
269 | } |
270 | |
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271 | B<TIP>: See Appendix 1 for tips on removing the leading spaces when |
272 | cutting and pasting example code from POD-based documents. |
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273 | |
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274 | Programmers experienced with object-oriented Perl should recognize |
275 | C<$self> as a reference to the object where this method was called. |
276 | On the other hand, C<$c> will be new to many Perl programmers who have |
277 | not used Catalyst before (it's sometimes written as C<$context>). The |
278 | Context object is automatically passed to all Catalyst components. It |
279 | is used to pass information between components and provide access to |
280 | Catalyst and plugin functionality. |
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281 | |
282 | B<Note:> Catalyst actions are regular Perl methods, but they make use |
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283 | of Nicholas Clark's C<attributes> module (that's the "C<: Local>" next |
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284 | to the C<sub list> in the code above) to provide additional |
285 | information to the Catalyst dispatcher logic. Many newer Catalyst |
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286 | applications are switching to the use of "Literal" C<:Path> actions |
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287 | and C<Args> attribute in lieu of C<: Local> and C<: Private>. For |
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288 | example, C<sub any_method :Path :Args(0)> can be used instead of C<sub |
289 | index :Private> (because no path was supplied to C<Path> it matches |
290 | the "empty" URL in the namespace of that module... the same thing |
291 | C<sub index> would do) or C<sub list :Path('list') :Args(0)> could be |
292 | used instead of the C<sub list : Local> above (the C<list> argument to |
293 | C<Path> would make it match on the URL C<list> under C<books>, the |
294 | namespace of the current module). See "Action Types" in |
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295 | L<Catalyst::Manual::Intro|Catalyst::Manual::Intro> as well as Part 5 |
296 | of this tutorial (Authentication) for additional information. Another |
297 | popular but more advanced feature is C<Chained> actions that allow a |
298 | single URL to "chain together" multiple action method calls, each with |
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299 | an appropriate number of arguments (see |
300 | L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained> for |
301 | details). |
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302 | |
303 | |
304 | =head1 CATALYST VIEWS |
305 | |
306 | As mentioned in Part 2 of the tutorial, views are where you render |
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307 | output, typically for display in the user's web browser (but also |
308 | possibly using other display output-generation systems). The code in |
309 | C<lib/MyApp/View> selects the I<type> of view to use, with the actual |
310 | rendering template found in the C<root> directory. As with virtually |
311 | every aspect of Catalyst, options abound when it comes to the specific |
312 | view technology you adopt inside your application. However, most |
313 | Catalyst applications use the Template Toolkit, known as TT (for more |
314 | information on TT, see L<http://www.template-toolkit.org>). Other |
315 | somewhat popular view technologies include Mason |
316 | (L<http://www.masonhq.com> and L<http://www.masonbook.com>) and |
317 | L<HTML::Template> (L<http://html-template.sourceforge.net>). |
318 | |
319 | |
320 | =head2 Create a Catalyst View |
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321 | |
322 | When using TT for the Catalyst view, there are two main helper scripts: |
323 | |
324 | =over 4 |
325 | |
326 | =item * |
327 | |
328 | L<Catalyst::Helper::View::TT|Catalyst::Helper::View::TT> |
329 | |
330 | =item * |
331 | |
332 | L<Catalyst::Helper::View::TTSite|Catalyst::Helper::View::TTSite> |
333 | |
334 | =back |
335 | |
336 | Both are similar, but C<TT> merely creates the C<lib/MyApp/View/TT.pm> |
337 | file and leaves the creation of any hierarchical template organization |
338 | entirely up to you. (It also creates a C<t/view_TT.t> file for testing; |
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339 | test cases will be discussed in Part 8.) On the other hand, the |
340 | C<TTSite> helper creates a modular and hierarchical view layout with |
341 | separate Template Toolkit (TT) files for common header and footer |
342 | information, configuration values, a CSS stylesheet, and more. |
343 | |
344 | While TTSite is useful to bootstrap a project, most in the Catalyst |
345 | community recommend that it's easier to learn both Catalyst and |
346 | Tempalte Toolkit if you use the more basic TT approach. Consequently, |
347 | this tutorial will use "plain old TT." |
348 | |
349 | Enter the following command to enable the C<TT> style of view |
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350 | rendering for this tutorial: |
351 | |
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352 | $ script/myapp_create.pl view TT TT |
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353 | exists "/home/me/MyApp/script/../lib/MyApp/View" |
354 | exists "/home/me/MyApp/script/../t" |
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355 | created "/home/me/MyApp/script/../lib/MyApp/View/TT.pm" |
356 | created "/home/me/MyApp/script/../t/view_TT.t" |
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357 | |
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358 | This simply creates a view called C<TT> (the second 'TT' argument) in |
359 | a file called C<TT.pm> (the first 'TT' argument). It is now up to you |
360 | to decide how you want to structure your view layout. For the |
361 | tutorial, we will start with a very simple TT template to initially |
362 | demonstrate the concepts, but quickly migrate to a more typical |
363 | "wrapper page" type of configuration (where the "wrapper" controls the |
364 | overall "look and feel" of your site from a single file or set of |
365 | files). |
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366 | |
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367 | Edit C<lib/MyApp/View/TT.pm> and you should see that the default |
368 | contents contains something similar to the following: |
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369 | |
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370 | __PACKAGE__->config(TEMPLATE_EXTENSION => '.tt'); |
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371 | |
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372 | And update it to match: |
373 | |
374 | __PACKAGE__->config( |
375 | # Change default TT extension |
376 | TEMPLATE_EXTENSION => '.tt2', |
377 | # Set the location for TT files |
378 | INCLUDE_PATH => [ |
379 | MyApp->path_to( 'root/src' ), |
380 | ], |
381 | ); |
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382 | |
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383 | B<NOTE:> Make sure to add a comma after '.tt2' outside the single |
384 | quote. |
385 | |
386 | This changes the default extenstion for Template Toolkit from '.tt' to |
387 | '.tt2' and changes the base directory for your template files from |
388 | C<root> to C<root/src>. |
389 | |
390 | |
391 | =head2 Create a TT Template Page |
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392 | |
393 | First create a directory for book-related TT templates: |
394 | |
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395 | $ mkdir -p root/src/books |
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396 | |
397 | Then create C<root/src/books/list.tt2> in your editor and enter: |
398 | |
399 | [% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%] |
400 | [% # see this "chomping" in your browser because HTML ignores blank lines, but -%] |
401 | [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%] |
402 | [%- # optional, but both the beginning and the ending TT tags support chomping. -%] |
403 | |
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404 | [% # Provide a title -%] |
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405 | [% META title = 'Book List' -%] |
406 | |
407 | <table> |
408 | <tr><th>Title</th><th>Rating</th><th>Author(s)</th></tr> |
409 | [% # Display each book in a table row %] |
410 | [% FOREACH book IN books -%] |
411 | <tr> |
412 | <td>[% book.title %]</td> |
413 | <td>[% book.rating %]</td> |
414 | </tr> |
415 | [% END -%] |
416 | </table> |
417 | |
418 | As indicated by the inline comments above, the C<META title> line uses |
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419 | TT's META feature to provide a title to the "wrapper" that we will |
420 | create later. Meanwhile, the C<FOREACH> loop iterates through each |
421 | C<book> model object and prints the C<title> and C<rating> fields. |
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422 | |
423 | If you are new to TT, the C<[%> and C<%]> tags are used to delimit TT |
424 | code. TT supports a wide variety of directives for "calling" other |
425 | files, looping, conditional logic, etc. In general, TT simplifies the |
426 | usual range of Perl operators down to the single dot (C<.>) operator. |
427 | This applies to operations as diverse as method calls, hash lookups, and |
428 | list index values (see |
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429 | L<http://search.cpan.org/perldoc?Template::Manual::Variables> |
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430 | for details and examples). In addition to the usual C<Template> module |
431 | Pod documentation, you can access the TT manual at |
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432 | L<http://search.cpan.org/perldoc?Template::Manual>. |
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433 | |
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434 | B<TIP:> While you can build all sorts of complex logic into your TT |
435 | templates, you should in general keep the "code" part of your templates |
436 | as simple as possible. If you need more complex logic, create helper |
437 | methods in your model that abstract out a set of code into a single call |
438 | from your TT template. (Note that the same is true of your controller |
439 | logic as well -- complex sections of code in your controllers should |
440 | often be pulled out and placed into your model objects.) |
441 | |
442 | |
443 | =head2 Test Run The Application |
444 | |
445 | To test your work so far, first start the development server: |
446 | |
447 | $ script/myapp_server.pl |
448 | |
449 | Then point your browser to L<http://localhost:3000> and you should |
450 | still get the Catalyst welcome page. Next, change the URL in your |
451 | browser to L<http://localhost:3000/books/list>. If you have |
452 | everything working so far, you should see a web page that displays |
453 | nothing other than our column headers for "Title", "Rating", and |
454 | "Author(s)" -- we will not see any books until we get the database and |
455 | model working below. |
456 | |
457 | If you run into problems getting your application to run correctly, it |
458 | might be helpful to refer to some of the debugging techniques covered in |
459 | the L<Debugging|Catalyst::Manual::Tutorial::Debugging> part of the |
460 | tutorial. |
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461 | |
462 | |
463 | =head1 CREATE A SQLITE DATABASE |
464 | |
465 | In this step, we make a text file with the required SQL commands to |
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466 | create a database table and load some sample data. We will use SQLite, |
467 | a popular database that is lightweight and easy to use. Open |
468 | C<myapp01.sql> in your editor and enter: |
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469 | |
470 | -- |
471 | -- Create a very simple database to hold book and author information |
472 | -- |
473 | CREATE TABLE books ( |
474 | id INTEGER PRIMARY KEY, |
475 | title TEXT , |
476 | rating INTEGER |
477 | ); |
478 | -- 'book_authors' is a many-to-many join table between books & authors |
479 | CREATE TABLE book_authors ( |
480 | book_id INTEGER, |
481 | author_id INTEGER, |
482 | PRIMARY KEY (book_id, author_id) |
483 | ); |
484 | CREATE TABLE authors ( |
485 | id INTEGER PRIMARY KEY, |
486 | first_name TEXT, |
487 | last_name TEXT |
488 | ); |
489 | --- |
490 | --- Load some sample data |
491 | --- |
492 | INSERT INTO books VALUES (1, 'CCSP SNRS Exam Certification Guide', 5); |
493 | INSERT INTO books VALUES (2, 'TCP/IP Illustrated, Volume 1', 5); |
494 | INSERT INTO books VALUES (3, 'Internetworking with TCP/IP Vol.1', 4); |
495 | INSERT INTO books VALUES (4, 'Perl Cookbook', 5); |
496 | INSERT INTO books VALUES (5, 'Designing with Web Standards', 5); |
497 | INSERT INTO authors VALUES (1, 'Greg', 'Bastien'); |
498 | INSERT INTO authors VALUES (2, 'Sara', 'Nasseh'); |
499 | INSERT INTO authors VALUES (3, 'Christian', 'Degu'); |
500 | INSERT INTO authors VALUES (4, 'Richard', 'Stevens'); |
501 | INSERT INTO authors VALUES (5, 'Douglas', 'Comer'); |
502 | INSERT INTO authors VALUES (6, 'Tom', 'Christiansen'); |
503 | INSERT INTO authors VALUES (7, 'Nathan', 'Torkington'); |
504 | INSERT INTO authors VALUES (8, 'Jeffrey', 'Zeldman'); |
505 | INSERT INTO book_authors VALUES (1, 1); |
506 | INSERT INTO book_authors VALUES (1, 2); |
507 | INSERT INTO book_authors VALUES (1, 3); |
508 | INSERT INTO book_authors VALUES (2, 4); |
509 | INSERT INTO book_authors VALUES (3, 5); |
510 | INSERT INTO book_authors VALUES (4, 6); |
511 | INSERT INTO book_authors VALUES (4, 7); |
512 | INSERT INTO book_authors VALUES (5, 8); |
513 | |
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514 | Then use the following command to build a C<myapp.db> SQLite database: |
515 | |
516 | $ sqlite3 myapp.db < myapp01.sql |
517 | |
518 | If you need to create the database more than once, you probably want to |
519 | issue the C<rm myapp.db> command to delete the database before you use |
1390ef0e |
520 | the C<sqlite3 myapp.db E<lt> myapp01.sql> command. |
3533daff |
521 | |
522 | Once the C<myapp.db> database file has been created and initialized, you |
523 | can use the SQLite command line environment to do a quick dump of the |
524 | database contents: |
525 | |
526 | $ sqlite3 myapp.db |
527 | SQLite version 3.4.2 |
528 | Enter ".help" for instructions |
529 | sqlite> select * from books; |
530 | 1|CCSP SNRS Exam Certification Guide|5 |
531 | 2|TCP/IP Illustrated, Volume 1|5 |
532 | 3|Internetworking with TCP/IP Vol.1|4 |
533 | 4|Perl Cookbook|5 |
534 | 5|Designing with Web Standards|5 |
535 | sqlite> .q |
536 | $ |
537 | |
538 | Or: |
539 | |
540 | $ sqlite3 myapp.db "select * from books" |
541 | 1|CCSP SNRS Exam Certification Guide|5 |
542 | 2|TCP/IP Illustrated, Volume 1|5 |
543 | 3|Internetworking with TCP/IP Vol.1|4 |
544 | 4|Perl Cookbook|5 |
545 | 5|Designing with Web Standards|5 |
546 | |
547 | As with most other SQL tools, if you are using the full "interactive" |
548 | environment you need to terminate your SQL commands with a ";" (it's not |
549 | required if you do a single SQL statement on the command line). Use |
550 | ".q" to exit from SQLite from the SQLite interactive mode and return to |
551 | your OS command prompt. |
552 | |
553 | |
554 | =head1 DATABASE ACCESS WITH C<DBIx::Class> |
555 | |
556 | Catalyst can be used with virtually any form of persistent datastore |
1390ef0e |
557 | available via Perl. For example, |
3533daff |
558 | L<Catalyst::Model::DBI|Catalyst::Model::DBI> can be used to |
559 | easily access databases through the traditional Perl C<DBI> interface. |
560 | However, most Catalyst applications use some form of ORM technology to |
561 | automatically create and save model objects as they are used. Although |
1390ef0e |
562 | Tony Bowden's L<Class::DBI|Class::DBI> has been a popular choice |
563 | in the past, Matt Trout's L<DBIx::Class|DBIx::Class> (abbreviated |
564 | as "DBIC") has rapidly emerged as the Perl-based ORM technology of choice. |
3533daff |
565 | Most new Catalyst applications rely on DBIC, as will this tutorial. |
566 | |
3533daff |
567 | |
1390ef0e |
568 | =head2 Create a Dynamic DBIC Model |
569 | |
570 | Use the C<create=dynamic> model helper option to build a model that |
3533daff |
571 | dynamically reads your database structure every time the application |
572 | starts: |
573 | |
d0496197 |
574 | $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=dynamic dbi:SQLite:myapp.db |
1390ef0e |
575 | exists "/home/me/MyApp/script/../lib/MyApp/Model" |
576 | exists "/home/me/MyApp/script/../t" |
577 | exists "/home/me/MyApp/script/../lib/MyApp" |
578 | created "/home/me/MyApp/script/../lib/MyApp/Schema.pm" |
579 | created "/home/me/MyApp/script/../lib/MyApp/Model/DB.pm" |
580 | created "/home/me/MyApp/script/../t/model_DB.t" |
3533daff |
581 | |
582 | |
d0496197 |
583 | C<DB> is the name of the model class to be created by the helper in |
1390ef0e |
584 | C<lib/MyApp/Model>. C<DBIC::Schema> is the type of the model to |
585 | create. C<MyApp::Schema> is the name of the DBIC schema file written |
586 | to C<lib/MyApp/Schema.pm>. Because we specified C<create=dynamic> to |
587 | the helper, it use |
588 | L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to |
589 | dynamically load the schema information from the database every time |
590 | the application starts. And finally, C<dbi:SQLite:myapp.db> is the |
591 | standard DBI connect string for use with SQLite. |
3533daff |
592 | |
d0496197 |
593 | B<NOTE:> Although the C<create=dynamic> option to the DBIC helper |
19c49089 |
594 | makes for a nifty demonstration, is only really suitable for very |
595 | small applications. After this demonstration, you should almost always |
596 | use the C<create=static> option that we switch to below. |
dc9a0503 |
597 | |
598 | |
1390ef0e |
599 | =head1 ENABLE THE MODEL IN THE CONTROLLER |
600 | |
601 | Open C<lib/MyApp/Controller/Books.pm> and uncomment the model code we |
602 | left disabled earlier (uncomment the line containing |
603 | C<[$c-E<gt>model('DB::Books')-E<gt>all]> and delete the next 2 lines): |
604 | |
605 | =head2 list |
606 | |
607 | Fetch all book objects and pass to books/list.tt2 in stash to be displayed |
608 | |
609 | =cut |
610 | |
611 | sub list : Local { |
612 | # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst |
613 | # 'Context' that's used to 'glue together' the various components |
614 | # that make up the application |
615 | my ($self, $c) = @_; |
616 | |
617 | # Retrieve all of the book records as book model objects and store in the |
618 | # stash where they can be accessed by the TT template |
619 | $c->stash->{books} = [$c->model('DB::Books')->all]; |
620 | |
621 | # Set the TT template to use. You will almost always want to do this |
622 | # in your action methods (action methods respond to user input in |
623 | # your controllers). |
624 | $c->stash->{template} = 'books/list.tt2'; |
625 | } |
626 | |
627 | B<TIP>: You may see the C<$c-E<gt>model('DB::Book')> uncommented above |
628 | written as C<$c-E<gt>model('DB')-E<gt>resultset('Book')>. The two |
629 | are equivalent. |
630 | |
631 | |
632 | =head2 Test Run The Application |
3533daff |
633 | |
634 | First, let's enable an environment variable option that causes |
635 | DBIx::Class to dump the SQL statements it's using to access the database |
636 | (this option can provide extremely helpful troubleshooting information): |
637 | |
638 | $ export DBIC_TRACE=1 |
639 | |
640 | This assumes you are using BASH as your shell -- adjust accordingly if |
641 | you are using a different shell (for example, under tcsh, use |
642 | C<setenv DBIC_TRACE 1>). |
643 | |
d0496197 |
644 | B<NOTE:> You can also set this in your code using |
3533daff |
645 | C<$class-E<gt>storage-E<gt>debug(1);>. See |
646 | L<DBIx::Class::Manual::Troubleshooting> for details (including options |
647 | to log to file instead of displaying to the Catalyst development server |
648 | log). |
649 | |
1390ef0e |
650 | Then launch the Catalyst development server. The log output should |
651 | display something like: |
3533daff |
652 | |
653 | $script/myapp_server.pl |
654 | [debug] Debug messages enabled |
1390ef0e |
655 | [debug] Statistics enabled |
3533daff |
656 | [debug] Loaded plugins: |
657 | .----------------------------------------------------------------------------. |
1390ef0e |
658 | | Catalyst::Plugin::ConfigLoader 0.20 | |
659 | | Catalyst::Plugin::StackTrace 0.08 | |
3533daff |
660 | | Catalyst::Plugin::Static::Simple 0.20 | |
661 | '----------------------------------------------------------------------------' |
662 | |
663 | [debug] Loaded dispatcher "Catalyst::Dispatcher" |
664 | [debug] Loaded engine "Catalyst::Engine::HTTP" |
665 | [debug] Found home "/home/me/MyApp" |
45d511e0 |
666 | [debug] Loaded Config "/home/me/MyApp/myapp.conf" |
3533daff |
667 | [debug] Loaded components: |
668 | .-----------------------------------------------------------------+----------. |
669 | | Class | Type | |
670 | +-----------------------------------------------------------------+----------+ |
671 | | MyApp::Controller::Books | instance | |
672 | | MyApp::Controller::Root | instance | |
d0496197 |
673 | | MyApp::Model::DB | instance | |
674 | | MyApp::Model::DB::Authors | class | |
675 | | MyApp::Model::DB::BookAuthors | class | |
676 | | MyApp::Model::DB::Books | class | |
3533daff |
677 | | MyApp::View::TT | instance | |
678 | '-----------------------------------------------------------------+----------' |
679 | |
680 | [debug] Loaded Private actions: |
681 | .----------------------+--------------------------------------+--------------. |
682 | | Private | Class | Method | |
683 | +----------------------+--------------------------------------+--------------+ |
684 | | /default | MyApp::Controller::Root | default | |
685 | | /end | MyApp::Controller::Root | end | |
1390ef0e |
686 | | /index | MyApp::Controller::Root | index | |
3533daff |
687 | | /books/index | MyApp::Controller::Books | index | |
688 | | /books/list | MyApp::Controller::Books | list | |
689 | '----------------------+--------------------------------------+--------------' |
690 | |
691 | [debug] Loaded Path actions: |
692 | .-------------------------------------+--------------------------------------. |
693 | | Path | Private | |
694 | +-------------------------------------+--------------------------------------+ |
1390ef0e |
695 | | / | /default | |
696 | | / | /index | |
697 | | /books | /books/index | |
3533daff |
698 | | /books/list | /books/list | |
699 | '-------------------------------------+--------------------------------------' |
700 | |
1390ef0e |
701 | [info] MyApp powered by Catalyst 5.7014 |
3533daff |
702 | You can connect to your server at http://localhost:3000 |
703 | |
1390ef0e |
704 | B<NOTE:> Be sure you run the C<script/myapp_server.pl> command from |
705 | the 'base' directory of your application, not inside the C<script> |
706 | directory itself or it will not be able to locate the C<myapp.db> |
707 | database file. You can use a fully qualified or a relative path to |
708 | locate the database file, but we did not specify that when we ran the |
3533daff |
709 | model helper earlier. |
710 | |
711 | Some things you should note in the output above: |
712 | |
713 | =over 4 |
714 | |
1390ef0e |
715 | =item * |
3533daff |
716 | |
1390ef0e |
717 | Catalyst::Model::DBIC::Schema dynamically created three model classes, |
718 | one to represent each of the three tables in our database |
d0496197 |
719 | (C<MyApp::Model::DB::Authors>, C<MyApp::Model::DB::BookAuthors>, |
720 | and C<MyApp::Model::DB::Books>). |
3533daff |
721 | |
1390ef0e |
722 | =item * |
3533daff |
723 | |
724 | The "list" action in our Books controller showed up with a path of |
725 | C</books/list>. |
726 | |
727 | =back |
728 | |
729 | Point your browser to L<http://localhost:3000> and you should still get |
730 | the Catalyst welcome page. |
731 | |
732 | Next, to view the book list, change the URL in your browser to |
733 | L<http://localhost:3000/books/list>. You should get a list of the five |
1390ef0e |
734 | books loaded by the C<myapp01.sql> script above without any formatting. |
735 | The rating for each book should appear on each row, but the "Author(s)" |
736 | column will sitll be blank (we will fill that in later). |
3533daff |
737 | |
738 | Also notice in the output of the C<script/myapp_server.pl> that DBIC |
739 | used the following SQL to retrieve the data: |
740 | |
741 | SELECT me.id, me.title, me.rating FROM books me |
742 | |
743 | because we enabled DBIC_TRACE. |
744 | |
0c51850e |
745 | You now have the beginnings of a simple but workable web application. |
3533daff |
746 | Continue on to future sections and we will develop the application |
747 | more fully. |
748 | |
749 | |
1390ef0e |
750 | =head1 CREATE A WRAPPER FOR THE VIEW |
751 | |
752 | When using TT, you can (and should!) create a wrapper that will |
753 | literally wrap content around each of your templates. This is |
754 | certainly useful as you have one main source for changing things that |
755 | will appear across your entire site/application instead of having to |
756 | edit many individual files. |
757 | |
758 | |
759 | =head2 Configure TT.pm For The Wrapper |
760 | |
761 | In order to create a wrapper, you must first edit your TT view and |
762 | tell it where to find your wrapper file. Your TT view is located in |
763 | C<lib/MyApp/View/TT.pm>. |
764 | |
765 | Edit C<lib/MyApp/View/TT.pm> and change it to match the following: |
766 | |
767 | __PACKAGE__->config( |
768 | # Change default TT extension |
769 | TEMPLATE_EXTENSION => '.tt2', |
770 | # Set the location for TT files |
771 | INCLUDE_PATH => [ |
772 | MyApp->path_to( 'root/src' ), |
773 | ], |
774 | # Set to 1 for detailed timer stats in your HTML as comments |
775 | TIMER => 0, |
776 | # This is your wrapper template located in the 'root/src' |
777 | WRAPPER => 'wrapper.tt2', |
778 | ); |
779 | |
780 | |
781 | =head2 Create the Wrapper Template File and Stylesheet |
782 | |
783 | Next you need to set up your wrapper template. Basically, you'll want |
784 | to take the overall layout of your site and put it into this file. |
785 | For the tutorial, open C<root/src/wrapper.tt2> and input the following: |
786 | |
787 | <?xml version="1.0" encoding="UTF-8"?> |
788 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> |
789 | <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> |
790 | <head> |
791 | <title>[% template.title or "My Catalyst App!" %]</title> |
792 | <link rel="stylesheet" href="[% c.uri_for('/static/css/main.css') %]" /> |
793 | </head> |
794 | |
795 | <body> |
796 | <div id="outer"> |
797 | <div id="header"> |
798 | [%# Your logo could go here -%] |
799 | <img src="[% c.uri_for('/static/images/btn_88x31_powered.png') %]" /> |
800 | [%# Insert the page title -%] |
801 | <h1>[% template.title or site.title %]</h1> |
802 | </div> |
803 | |
804 | <div id="bodyblock"> |
805 | <div id="menu"> |
806 | Navigation: |
807 | <ul> |
808 | <li><a href="[% c.uri_for('/books/list') %]">Home</a></li> |
809 | <li><a href="[% c.uri_for('/') %]" title="Catalyst Welcome Page">Welcome</a></li> |
810 | <li><a href="mailto:nobody@nowhere.com" title="Contact Us">Contact Us</a></li> |
811 | </ul> |
812 | </div><!-- end menu --> |
813 | |
814 | <div id="content"> |
815 | [%# Status and error messages %] |
816 | <span class="message">[% status_msg %]</span> |
817 | <span class="error">[% error_msg %]</span> |
818 | [%# This is where TT will stick all of your template's contents. -%] |
819 | [% content %] |
820 | </div><!-- end content --> |
821 | </div><!-- end bodyblock --> |
822 | |
823 | <div id="footer">Copyright (c) your name goes here</div> |
824 | </div><!-- end outter --> |
825 | |
826 | </body> |
827 | </html> |
828 | |
829 | Notice the status and error message sections in the code above: |
830 | |
831 | <span class="status">[% status_msg %]</span> |
832 | <span class="error">[% error_msg %]</span> |
833 | |
834 | If we set either message in the Catalyst stash (e.g., |
835 | C<$c-E<gt>stash-E<gt>{status_msg} = 'Request was successful!'>) it |
836 | will be displayed whenever any view used by that request is rendered. |
837 | The C<message> and C<error> CSS styles can be customized to suit your |
838 | needs in the C<root/static/css/main.css> file we create below. |
839 | |
840 | B<Notes:> |
841 | |
842 | =over 4 |
843 | |
844 | =item * |
845 | |
846 | The Catalyst stash only lasts for a single HTTP request. If |
847 | you need to retain information across requests you can use |
848 | L<Catalyst::Plugin::Session|Catalyst::Plugin::Session> (we will use |
849 | Catalyst sessions in the Authentication part of the tutorial). |
850 | |
851 | =item * |
852 | |
853 | Although it is beyond the scope of this tutorial, you may wish to use |
854 | a JavaScript or AJAX tool such as jQuery (L<http://www.jquery.com>) or |
855 | Dojo (L<http://www.dojotoolkit.org>). |
856 | |
857 | =back |
858 | |
859 | |
860 | =head3 Create A Basic Stylesheet |
861 | |
862 | First create a central location for stylesheets under the static |
863 | directory: |
864 | |
865 | $ mkdir root/static/css |
866 | |
867 | Then open the file C<root/static/css/main.css> (the file referenced in |
868 | the stylesheet href link of our wrapper above) and add the following |
869 | content: |
870 | |
871 | #header { |
872 | text-align: center; |
873 | } |
874 | #header h1 { |
875 | margin: 0; |
876 | } |
877 | #header img { |
878 | float: right; |
879 | } |
880 | #footer { |
881 | text-align: center; |
882 | font-style: italic; |
883 | padding-top: 20px; |
884 | } |
885 | #menu { |
886 | font-weight: bold; |
887 | background-color: #ddd; |
888 | } |
889 | #menu ul { |
890 | list-style: none; |
891 | float: left; |
892 | margin: 0; |
893 | padding: 0 0 50% 5px; |
894 | font-weight: normal; |
895 | background-color: #ddd; |
896 | width: 100px; |
897 | } |
898 | #content { |
899 | margin-left: 120px; |
900 | } |
901 | .message { |
902 | color: #390; |
903 | } |
904 | .error { |
905 | color: #f00; |
906 | } |
907 | |
908 | You may wish to check out a "CSS Framework" like Emastic |
909 | (L<http://code.google.com/p/emastic/>) as a way to quickly |
910 | provide lots of high-quality CSS functionality. |
911 | |
912 | |
913 | =head2 Test Run The Application |
914 | |
915 | Restart the development server and hit "Reload" in your web browser |
916 | and you should now see a formatted version of our basic book list. |
917 | Although our wrapper and stylesheet are obviously very simple, you |
918 | should see how it allows us to control the overall look of an entire |
919 | website from two central files. To add new pages to the site, just |
920 | provide a template that fills in the C<content> section of our wrapper |
921 | template -- the wrapper will provide the overall feel of the page. |
922 | |
923 | |
3533daff |
924 | =head1 A STATIC DATABASE MODEL WITH C<DBIx::Class> |
925 | |
926 | =head2 Create Static DBIC Schema Files |
927 | |
1390ef0e |
928 | Unlike the previous DBIC section where we had C<create=dynamic> |
929 | automatically discover the structure of the database every time the |
930 | application started, here we will use static schema files for more |
931 | control. This is typical of most "real world" applications. |
3533daff |
932 | |
1390ef0e |
933 | One option would be to manually create a separate schema file for each |
934 | table in the database, however, lets use the same |
935 | L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> used |
936 | earlier with C<create=dynamic> to build the static files for us. |
9ad715b3 |
937 | First, lets remove the schema file created earlier: |
3533daff |
938 | |
1390ef0e |
939 | $ rm lib/MyApp/Schema.pm |
3533daff |
940 | |
941 | Now regenerate the schema using the C<create=static> option: |
942 | |
d0496197 |
943 | $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema create=static dbi:SQLite:myapp.db |
944 | exists "/home/kclark/dev/MyApp/script/../lib/MyApp/Model" |
945 | exists "/home/kclark/dev/MyApp/script/../t" |
946 | Dumping manual schema for MyApp::Schema to directory /home/kclark/dev/MyApp/script/../lib ... |
3533daff |
947 | Schema dump completed. |
d0496197 |
948 | exists "/home/kclark/dev/MyApp/script/../lib/MyApp/Model/DB.pm" |
3533daff |
949 | |
1390ef0e |
950 | We could have also deleted C<lib/MyApp/Model/DB.pm>, but it would |
3533daff |
951 | have regenerated the same file (note the C<exists> in the output above). |
d0496197 |
952 | If you take a look at C<lib/MyApp/Model/DB.pm>, it simply contains |
953 | a reference to the actual schema file in C<lib/MyApp/Schema.pm> |
3533daff |
954 | along with the database connect string. |
955 | |
1390ef0e |
956 | If you look in the C<lib/MyApp/Schema.pm> file, you will find that it |
957 | is no longer using |
958 | L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> as its base |
959 | class (L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> is |
960 | only being used by the helper to load the schema once and then create |
961 | the static files for us) and C<Schema.pm> only contains a call to the |
962 | C<load_classes> method. You will also find that C<lib/MyApp/Schema> |
963 | contains a C<Schema> subdirectory, with one file inside this directory |
964 | for each of the tables in our simple database (C<Authors.pm>, |
965 | C<BookAuthors.pm>, and C<Books.pm>). These three files were created |
966 | based on the information found by |
967 | L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> as the |
968 | helper ran. |
969 | |
970 | The idea with all of the files created under C<lib/MyApp/Schema> by |
971 | the C<create=static> option is to only edit the files below the C<# DO |
972 | NOT MODIFY THIS OR ANYTHING ABOVE!> warning. If you place all of your |
3533daff |
973 | changes below that point in the file, you can regenerate the |
1390ef0e |
974 | automatically created information at the top of each file should your |
975 | database structure get updated. |
3533daff |
976 | |
1390ef0e |
977 | Also note the "flow" of the model information across the various files |
978 | and directories. Catalyst will initially load the model from |
d0496197 |
979 | C<lib/MyApp/Model/DB.pm>. This file contains a reference to |
980 | C<lib/MyApp/Schema.pm>, so that file is loaded next. Finally, |
1390ef0e |
981 | the call to C<load_classes> in C<Schema.pm> will load each of the |
d0496197 |
982 | table-specific "results source" files from the C<lib/MyApp/Schema> |
1390ef0e |
983 | subdirectory. These three table-specific DBIC schema files will then be |
984 | used to create three table-specific Catalyst models every time the |
3533daff |
985 | application starts (you can see these three model files listed in |
986 | the debug output generated when you launch the application). |
987 | |
988 | |
989 | =head2 Updating the Generated DBIC Schema Files |
990 | |
3533daff |
991 | Let's manually add some relationship information to the auto-generated |
d0496197 |
992 | schema files. First edit C<lib/MyApp/Schema/Books.pm> and |
1390ef0e |
993 | add the following text below the C<# You can replace this text...> |
3533daff |
994 | comment: |
995 | |
996 | # |
997 | # Set relationships: |
1390ef0e |
998 | # |
3533daff |
999 | |
1000 | # has_many(): |
1001 | # args: |
1002 | # 1) Name of relationship, DBIC will create accessor with this name |
1003 | # 2) Name of the model class referenced by this relationship |
1004 | # 3) Column name in *foreign* table |
d0496197 |
1005 | __PACKAGE__->has_many(book_authors => 'MyApp::Schema::BookAuthors', 'book_id'); |
3533daff |
1006 | |
1007 | # many_to_many(): |
1008 | # args: |
1009 | # 1) Name of relationship, DBIC will create accessor with this name |
1390ef0e |
1010 | # 2) Name of has_many() relationship this many_to_many() is shortcut for |
1011 | # 3) Name of belongs_to() relationship in model class of has_many() above |
3533daff |
1012 | # You must already have the has_many() defined to use a many_to_many(). |
1013 | __PACKAGE__->many_to_many(authors => 'book_authors', 'author'); |
1014 | |
1015 | |
1016 | B<Note:> Be careful to put this code I<above> the C<1;> at the end of the |
1017 | file. As with any Perl package, we need to end the last line with |
1018 | a statement that evaluates to C<true>. This is customarily done with |
1019 | C<1;> on a line by itself. |
1020 | |
1390ef0e |
1021 | This code defines both a C<has_many> and a C<many_to_many> relationship. |
1022 | The C<many_to_many> relationship is optional, but it makes it easier to |
1023 | map a book to its collection of authors. Without it, we would have to |
1024 | "walk" though the C<book_authors> table as in |
1025 | C<$book-E<gt>book_authors-E<gt>first-E<gt>author-E<gt>last_name> |
1026 | (we will see examples on how to use DBIC objects in your code soon, |
1027 | but note that because C<$book-E<gt>book_authors> can return multiple |
1028 | authors, we have to use C<first> to display a single author). |
1029 | C<many_to_many> allows us to use the shorter |
1030 | C<$book-E<gt>authors-E<gt>first-E<gt>last_name>. |
1031 | Note that you cannot define a C<many_to_many> relationship without |
1032 | also having the C<has_many> relationship in place. |
3533daff |
1033 | |
d0496197 |
1034 | Then edit C<lib/MyApp/Schema/Authors.pm> and add relationship |
3533daff |
1035 | information as follows (again, be careful to put in above the C<1;> but |
1036 | below the C<# DO NOT MODIFY THIS OR ANYTHING ABOVE!> comment): |
1037 | |
1038 | # |
1039 | # Set relationships: |
1040 | # |
1041 | |
1042 | # has_many(): |
1043 | # args: |
1044 | # 1) Name of relationship, DBIC will create accessor with this name |
1045 | # 2) Name of the model class referenced by this relationship |
1046 | # 3) Column name in *foreign* table |
d0496197 |
1047 | __PACKAGE__->has_many(book_author => 'MyApp::Schema::BookAuthors', 'author_id'); |
3533daff |
1048 | |
1049 | # many_to_many(): |
1050 | # args: |
1051 | # 1) Name of relationship, DBIC will create accessor with this name |
1052 | # 2) Name of has_many() relationship this many_to_many() is shortcut for |
1390ef0e |
1053 | # 3) Name of belongs_to() relationship in model class of has_many() above |
3533daff |
1054 | # You must already have the has_many() defined to use a many_to_many(). |
1055 | __PACKAGE__->many_to_many(books => 'book_author', 'book'); |
1056 | |
1390ef0e |
1057 | Finally, do the same for the "join table," |
d0496197 |
1058 | C<lib/MyApp/Schema/BookAuthors.pm>: |
3533daff |
1059 | |
1060 | # |
1061 | # Set relationships: |
1062 | # |
1063 | |
1064 | # belongs_to(): |
1065 | # args: |
1066 | # 1) Name of relationship, DBIC will create accessor with this name |
1067 | # 2) Name of the model class referenced by this relationship |
1068 | # 3) Column name in *this* table |
d0496197 |
1069 | __PACKAGE__->belongs_to(book => 'MyApp::Schema::Books', 'book_id'); |
3533daff |
1070 | |
1071 | # belongs_to(): |
1072 | # args: |
1073 | # 1) Name of relationship, DBIC will create accessor with this name |
1074 | # 2) Name of the model class referenced by this relationship |
1075 | # 3) Column name in *this* table |
d0496197 |
1076 | __PACKAGE__->belongs_to(author => 'MyApp::Schema::Authors', 'author_id'); |
3533daff |
1077 | |
1078 | |
1390ef0e |
1079 | =head2 Run The Application |
3533daff |
1080 | |
1081 | Run the Catalyst "demo server" script with the C<DBIC_TRACE> option |
1082 | (it might still be enabled from earlier in the tutorial, but here |
1083 | is an alternate way to specify the option just in case): |
1084 | |
1085 | $ DBIC_TRACE=1 script/myapp_server.pl |
1086 | |
1390ef0e |
1087 | Make sure that the application loads correctly and that you see the |
1088 | three dynamically created model class (one for each of the |
3533daff |
1089 | table-specific schema classes we created). |
1090 | |
1091 | Then hit the URL L<http://localhost:3000/books/list> and be sure that |
1092 | the book list is displayed. |
1093 | |
1390ef0e |
1094 | You can leave the development server running for the next step if you |
1095 | wish. |
3533daff |
1096 | |
1097 | |
1098 | =head1 UPDATING THE VIEW |
1099 | |
1100 | Let's add a new column to our book list page that takes advantage of |
1101 | the relationship information we manually added to our schema files |
1102 | in the previous section. Edit C<root/src/books/list.tt2> add add the |
1103 | following code below the existing table cell that contains |
1390ef0e |
1104 | C<book.rating> (IOW, add a new table cell below the existing two |
3533daff |
1105 | C<td> cells): |
1106 | |
1107 | <td> |
1108 | [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%] |
1109 | [% # loop in 'side effect notation' to load just the last names of the -%] |
a0c5188a |
1110 | [% # authors into the list. Note that the 'push' TT vmethod does not print -%] |
3533daff |
1111 | [% # a value, so nothing will be printed here. But, if you have something -%] |
1112 | [% # in TT that does return a method and you don't want it printed, you -%] |
1113 | [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%] |
1114 | [% # call it and discard the return value. -%] |
1115 | [% tt_authors = [ ]; |
1116 | tt_authors.push(author.last_name) FOREACH author = book.authors %] |
1117 | [% # Now use a TT 'virtual method' to display the author count in parens -%] |
1118 | [% # Note the use of the TT filter "| html" to escape dangerous characters -%] |
1119 | ([% tt_authors.size | html %]) |
1120 | [% # Use another TT vmethod to join & print the names & comma separators -%] |
1121 | [% tt_authors.join(', ') | html %] |
1122 | </td> |
1123 | |
1390ef0e |
1124 | Then hit "Reload" in your browser (note that you don't need to reload |
3533daff |
1125 | the development server or use the C<-r> option when updating TT |
1390ef0e |
1126 | templates) and you should now see the number of authors each book has |
1127 | along with a comma-separated list of the authors' last names. (If you |
1128 | didn't leave the development server running from the previous step, |
1129 | you will obviously need to start it before you can refresh your |
1130 | browser window.) |
1131 | |
1132 | If you are still running the development server with C<DBIC_TRACE> |
1133 | enabled, you should also now see five more C<SELECT> statements in the |
1134 | debug output (one for each book as the authors are being retrieved by |
3533daff |
1135 | DBIC). |
1136 | |
1390ef0e |
1137 | Also note that we are using "| html", a type of TT filter, to escape |
3533daff |
1138 | characters such as E<lt> and E<gt> to < and > and avoid various |
1390ef0e |
1139 | types of dangerous hacks against your application. In a real |
1140 | application, you would probably want to put "| html" at the end of |
1141 | every field where a user has control over the information that can |
3533daff |
1142 | appear in that field (and can therefore inject markup or code if you |
1143 | don't "neutralize" those fields). In addition to "| html", Template |
1144 | Toolkit has a variety of other useful filters that can found in the |
1145 | documentation for L<Template::Filters|Template::Filters>. |
1146 | |
1147 | |
1390ef0e |
1148 | =head1 RUNNING THE APPLICATION FROM THE COMMAND LINE |
1149 | |
1150 | In some situations, it can be useful to run your application and |
1151 | display a page without using a browser. Catalyst lets you do this |
1152 | using the C<scripts/myapp_test.pl> script. Just supply the URL you |
1153 | wish to display and it will run that request through the normal |
1154 | controller dispatch logic and use the appropriate view to render the |
1155 | output (obviously, complex pages may dump a lot of text to your |
1156 | terminal window). For example, if you type: |
1157 | |
1158 | $ script/myapp_test.pl "/books/list" |
1159 | |
1160 | You should get the same text as if you visited |
1161 | L<http://localhost:3000/books/list> with the normal development server |
1162 | and asked your browser to view the page source. |
3533daff |
1163 | |
1390ef0e |
1164 | |
1165 | =head1 OPTIONAL INFORMATION |
1166 | |
1167 | B<NOTE: The rest of this part of the tutorial is optional. You can |
1168 | skip to Part 4, L<Basic CRUD|Catalyst::Manual::Tutorial::BasicCRUD>, |
3533daff |
1169 | if you wish.> |
1170 | |
1390ef0e |
1171 | =head2 Using C<RenderView> for the Default View |
1172 | |
1173 | Once your controller logic has processed the request from a user, it |
1174 | forwards processing to your view in order to generate the appropriate |
3533daff |
1175 | response output. Catalyst uses |
1390ef0e |
1176 | L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> by |
1177 | default to automatically performs this operation. If you look in |
1178 | C<lib/MyApp/Controller/Root.pm>, you should see the empty |
3533daff |
1179 | definition for the C<sub end> method: |
1180 | |
1181 | sub end : ActionClass('RenderView') {} |
1182 | |
1390ef0e |
1183 | The following bullet points provide a quick overview of the |
3533daff |
1184 | C<RenderView> process: |
1185 | |
1186 | =over 4 |
1187 | |
1188 | =item * |
1189 | |
1190 | C<Root.pm> is designed to hold application-wide logic. |
1191 | |
1192 | =item * |
1193 | |
1390ef0e |
1194 | At the end of a given user request, Catalyst will call the most specific |
1195 | C<end> method that's appropriate. For example, if the controller for a |
1196 | request has an C<end> method defined, it will be called. However, if |
1197 | the controller does not define a controller-specific C<end> method, the |
3533daff |
1198 | "global" C<end> method in C<Root.pm> will be called. |
1199 | |
1200 | =item * |
1201 | |
1202 | Because the definition includes an C<ActionClass> attribute, the |
1203 | L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> logic |
1204 | will be executed B<after> any code inside the definition of C<sub end> |
1205 | is run. See L<Catalyst::Manual::Actions|Catalyst::Manual::Actions> |
1206 | for more information on C<ActionClass>. |
1207 | |
1208 | =item * |
1209 | |
1390ef0e |
1210 | Because C<sub end> is empty, this effectively just runs the default |
1211 | logic in C<RenderView>. However, you can easily extend the |
1212 | C<RenderView> logic by adding your own code inside the empty method body |
1213 | (C<{}>) created by the Catalyst Helpers when we first ran the |
1214 | C<catalyst.pl> to initialize our application. See |
1215 | L<Catalyst::Action::RenderView|Catalyst::Action::RenderView> for more |
3533daff |
1216 | detailed information on how to extended C<RenderView> in C<sub end>. |
1217 | |
1218 | =back |
1219 | |
1220 | |
1221 | =head2 Using The Default Template Name |
1222 | |
1390ef0e |
1223 | By default, C<Catalyst::View::TT> will look for a template that uses the |
1224 | same name as your controller action, allowing you to save the step of |
1225 | manually specifying the template name in each action. For example, this |
1226 | would allow us to remove the |
1227 | C<$c-E<gt>stash-E<gt>{template} = 'books/list.tt2';> line of our |
1228 | C<list> action in the Books controller. Open |
3533daff |
1229 | C<lib/MyApp/Controller/Books.pm> in your editor and comment out this line |
1230 | to match the following (only the C<$c-E<gt>stash-E<gt>{template}> line |
1231 | has changed): |
1232 | |
1233 | =head2 list |
1234 | |
1235 | Fetch all book objects and pass to books/list.tt2 in stash to be displayed |
1236 | |
1237 | =cut |
1238 | |
1239 | sub list : Local { |
1240 | # Retrieve the usual Perl OO '$self' for this object. $c is the Catalyst |
1241 | # 'Context' that's used to 'glue together' the various components |
1242 | # that make up the application |
1243 | my ($self, $c) = @_; |
1244 | |
1245 | # Retrieve all of the book records as book model objects and store in the |
1246 | # stash where they can be accessed by the TT template |
d0496197 |
1247 | $c->stash->{books} = [$c->model('DB::Books')->all]; |
3533daff |
1248 | |
1249 | # Set the TT template to use. You will almost always want to do this |
1250 | # in your action methods (actions methods respond to user input in |
1251 | # your controllers). |
1252 | #$c->stash->{template} = 'books/list.tt2'; |
1253 | } |
1254 | |
3533daff |
1255 | |
1390ef0e |
1256 | You should now be able to restart the development server as per the |
3533daff |
1257 | previous section and access the L<http://localhost:3000/books/list> |
1258 | as before. |
1259 | |
1260 | B<NOTE:> Please note that if you use the default template technique, |
1261 | you will B<not> be able to use either the C<$c-E<gt>forward> or |
1390ef0e |
1262 | the C<$c-E<gt>detach> mechanisms (these are discussed in Part 2 and |
3533daff |
1263 | Part 9 of the Tutorial). |
1264 | |
1265 | |
1266 | =head2 Return To A Manually-Specified Template |
1267 | |
1268 | In order to be able to use C<$c-E<gt>forward> and C<$c-E<gt>detach> |
1269 | later in the tutorial, you should remove the comment from the |
1270 | statement in C<sub list> in C<lib/MyApp/Controller/Books.pm>: |
1271 | |
1272 | $c->stash->{template} = 'books/list.tt2'; |
1273 | |
1390ef0e |
1274 | Then delete the C<TEMPLATE_EXTENSION> line in |
3533daff |
1275 | C<lib/MyApp/View/TT.pm>. |
1276 | |
1390ef0e |
1277 | You should then be able to restart the development server and |
3533daff |
1278 | access L<http://localhost:3000/books/list> in the same manner as |
1279 | with earlier sections. |
1280 | |
1281 | |
1282 | =head1 AUTHOR |
1283 | |
1284 | Kennedy Clark, C<hkclark@gmail.com> |
1285 | |
1286 | Please report any errors, issues or suggestions to the author. The |
1287 | most recent version of the Catalyst Tutorial can be found at |
1288 | L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/Catalyst-Manual/lib/Catalyst/Manual/Tutorial/>. |
1289 | |
45c7830f |
1290 | Copyright 2006-2008, Kennedy Clark, under Creative Commons License |
8482d557 |
1291 | (L<http://creativecommons.org/licenses/by-sa/3.0/us/>). |