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1 | =head1 NAME |
2 | |
3 | Catalyst::Manual::ExtendingCatalyst - Extending The Framework |
4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | This document will provide you with access points, techniques and best |
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8 | practices to extend the L<Catalyst> framework, or to find more elegant |
9 | ways to abstract and use your own code. |
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10 | |
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11 | The design of Catalyst is such that the framework itself should not |
12 | get in your way. There are many entry points to alter or extend |
13 | Catalyst's behaviour, and this can be confusing. This document is |
14 | written to help you understand the possibilities, current practices |
15 | and their consequences. |
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16 | |
17 | Please read the L<BEST PRACTICES> section before deciding on a design, |
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18 | especially if you plan to release your code to CPAN. The Catalyst |
19 | developer and user communities, which B<you are part of>, will benefit |
20 | most if we all work together and coordinate. |
21 | |
22 | If you are unsure on an implementation or have an idea you would like |
23 | to have RFC'ed, it surely is a good idea to send your questions and |
24 | suggestions to the Catalyst mailing list (See L<Catalyst/SUPPORT>) |
25 | and/or come to the C<#catalyst> channel on the C<irc.perl.org> |
26 | network. You might also want to refer to those places for research to |
27 | see if a module doing what you're trying to implement already |
28 | exists. This might give you a solution to your problem or a basis for |
29 | starting. |
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30 | |
31 | =head1 BEST PRACTICES |
32 | |
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33 | During Catalyst's early days, it was common to write plugins to |
34 | provide functionality application wide. Since then, Catalyst has |
35 | become a lot more flexible and powerful. It soon became a best |
36 | practice to use some other form of abstraction or interface, to keep |
37 | the scope of its influence as close as possible to where it belongs. |
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38 | |
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39 | For those in a hurry, here's a quick checklist of some fundamental |
40 | points. If you are going to read the whole thing anyway, you can jump |
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41 | forward to L</Namespaces>. |
42 | |
43 | =head2 Quick Checklist |
44 | |
45 | =over |
46 | |
47 | =item Use the C<CatalystX::*> namespace if you can! |
48 | |
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49 | If your extension isn't a Model, View, Controller, Plugin, Engine, |
50 | or Log, it's best to leave it out of the C<Catalyst::> namespace. |
51 | Use <CatalystX::> instead. |
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52 | |
53 | =item Don't make it a plugin unless you have to! |
54 | |
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55 | A plugin should be careful since it's overriding Catalyst internals. |
56 | If your plugin doesn't really need to muck with the internals, make it a |
57 | base Controller or Model. |
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58 | |
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59 | If you need to hook (but not alter) the internals, then make it a L<Moose::Role> |
60 | |
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61 | =item There's a community. Use it! |
62 | |
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63 | There are many experienced developers in the Catalyst community, |
64 | there's always the IRC channel and the mailing list to discuss things. |
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65 | |
66 | =item Add tests and documentation! |
67 | |
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68 | This gives a stable basis for contribution, and even more importantly, |
69 | builds trust. The easiest way is a test application. See |
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70 | L<Catalyst::Manual::Tutorial::Testing> for more information. |
71 | |
72 | =back |
73 | |
74 | =head2 Namespaces |
75 | |
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76 | While some core extensions (engines, plugins, etc.) have to be placed |
77 | in the C<Catalyst::*> namespace, the Catalyst core would like to ask |
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78 | developers to use the C<CatalystX::*> namespace if possible. |
79 | |
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80 | When you try to put a base class for a C<Model>, C<View> or |
81 | C<Controller> directly under your C<MyApp> directory as, for example, |
82 | C<MyApp::Controller::Foo>, you will have the problem that Catalyst |
83 | will try to load that base class as a component of your |
84 | application. The solution is simple: Use another namespace. Common |
85 | ones are C<MyApp::Base::Controller::*> or C<MyApp::ControllerBase::*> |
86 | as examples. |
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87 | |
88 | =head2 Can it be a simple module? |
89 | |
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90 | Sometimes you want to use functionality in your application that |
91 | doesn't require the framework at all. Remember that Catalyst is just |
92 | Perl and you always can just C<use> a module. If you have application |
93 | specific code that doesn't need the framework, there is no problem in |
94 | putting it in your C<MyApp::*> namespace. Just don't put it in |
95 | C<Model>, C<Controller> or C<View>, because that would make Catalyst |
96 | try to load them as components. |
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97 | |
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98 | Writing a generic component that only works with Catalyst is wasteful |
99 | of your time. Try writing a plain perl module, and then a small bit |
100 | of glue that integrates it with Catalyst. See |
101 | L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> for a |
102 | module that takes the approach. The advantage here is that your |
103 | "Catalyst" DBIC schema works perfectly outside of Catalyst, making |
104 | testing (and command-line scripts) a breeze. The actual Catalyst |
105 | Model is just a few lines of glue that makes working with the schema |
106 | convenient. |
107 | |
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108 | If you want the thinnest interface possible, take a look at |
109 | L<Catalyst::Model::Adaptor|Catalyst::Model::Adaptor>. |
110 | |
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111 | =head2 Using Moose roles to apply method modifiers |
112 | |
113 | Rather than having a complex set of base classes which you have to mixin |
114 | via multiple inheritence, if your functionality is well structured, then |
115 | it's possible to use the composability of L<Moose> roles, and method modifiers |
116 | to hook onto to provide functionality. |
117 | |
118 | For a simple example of this, see L<CatalystX::REPL>. |
119 | |
120 | B<Note:> Currently, controllers with attributes will not function correctly |
121 | in conjunction with Moose roles. |
122 | |
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123 | =head2 Inheritance and overriding methods |
124 | |
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125 | While Catalyst itself is still based on L<NEXT> (for multiple |
126 | inheritance), extension developers are encouraged to use L<Class::C3>, |
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127 | via L<MRO::Compat>, which is what Catalyst will be switching to in the |
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128 | 5.80 release. |
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129 | |
130 | When overriding a method, keep in mind that some day additionally |
131 | arguments may be provided to the method, if the last parameter is not |
132 | a flat list. It is thus better to override a method by shifting the |
133 | invocant off of C<@_> and assign the rest of the used arguments, so |
134 | you can pass your complete arguments to the original method via C<@_>: |
135 | |
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136 | use MRO::Compat; ... |
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137 | |
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138 | sub foo { my $self = shift; |
139 | my ($bar, $baz) = @_; # ... return |
140 | $self->next::method(@_); } |
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141 | |
142 | If you would do the common |
143 | |
144 | my ($self, $foo, $bar) = @_; |
145 | |
146 | you'd have to use a much uglier construct to ensure that all arguments |
147 | will be passed along and the method is future proof: |
148 | |
149 | $self->next::method(@_[ 1 .. $#_ ]); |
150 | |
151 | =head2 Tests and documentation |
152 | |
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153 | When you release your module to the CPAN, proper documentation and at |
154 | least a basic test suite (which means more than pod or even just |
155 | C<use_ok>, sorry) gives people a good base to contribute to the |
156 | module. It also shows that you care for your users. If you would like |
157 | your module to become a recommended addition, these things will prove |
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158 | invaluable. |
159 | |
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160 | If you're just getting started, try using |
161 | L<CatalystX::Starter|CatalystX::Starter> to generate some example |
162 | tests for your module. |
163 | |
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164 | =head2 Maintenance |
165 | |
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166 | In planning to release a module to the community (Catalyst or CPAN and |
167 | Perl), you should consider if you have the resources to keep it up to |
168 | date, including fixing bugs and accepting contributions. |
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169 | |
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170 | If you're not sure about this, you can always ask in the proper |
171 | Catalyst or Perl channels if someone else might be interested in the |
172 | project, and would jump in as co-maintainer. |
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173 | |
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174 | A public repository can further ease interaction with the |
175 | community. Even read only access enables people to provide you with |
176 | patches to your current development version. subversion, SVN and SVK, |
177 | are broadly preferred in the Catalyst community. |
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178 | |
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179 | If you're developing a Catalyst extension, please consider asking the |
180 | core team for space in Catalyst's own subversion repository. You can |
181 | get in touch about this via IRC or the Catalyst developers mailing |
182 | list. |
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183 | |
184 | =head2 The context object |
185 | |
186 | Sometimes you want to get a hold of the context object in a component |
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187 | that was created on startup time, where no context existed yet. Often |
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188 | this is about the model reading something out of the stash or other |
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189 | context information (current language, for example). |
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190 | |
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191 | If you use the context object in your component you have tied it to an |
192 | existing request. This means that you might get into problems when |
193 | you try to use the component (e.g. the model - the most common case) |
194 | outside of Catalyst, for example in cronjobs. |
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195 | |
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196 | A stable solution to this problem is to design the Catalyst model |
197 | separately from the underlying model logic. Let's take |
198 | L<Catalyst::Model::DBIC::Schema> as an example. You can create a |
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199 | schema outside of Catalyst that knows nothing about the web. This kind |
200 | of design ensures encapsulation and makes development and maintenance |
201 | a whole lot easier. The you use the aforementioned model to tie your |
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202 | schema to your application. This gives you a C<MyApp::DBIC> (the name |
203 | is of course just an example) model as well as |
204 | C<MyApp::DBIC::TableName> models to access your result sources |
205 | directly. |
206 | |
207 | By creating such a thin layer between the actual model and the |
208 | Catalyst application, the schema itself is not at all tied to any |
209 | application and the layer in-between can access the model's API using |
210 | information from the context object. |
211 | |
212 | A Catalyst component accesses the context object at request time with |
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213 | L<Catalyst::Component/"ACCEPT_CONTEXT($c, @args)">. |
214 | |
215 | =head1 CONFIGURATION |
216 | |
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217 | The application has to interact with the extension with some |
218 | configuration. There is of course again more than one way to do it. |
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219 | |
220 | =head2 Attributes |
221 | |
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222 | You can specify any valid Perl attribute on Catalyst actions you like. |
223 | (See L<attributes/"Syntax of Attribute Lists"> for a description of |
224 | what is valid.) These will be available on the C<Catalyst::Action> |
225 | instance via its C<attributes> accessor. To give an example, this |
226 | action: |
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227 | |
228 | sub foo : Local Bar('Baz') { |
229 | my ($self, $c) = @_; |
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230 | my $attributes = |
231 | $self->action_for('foo')->attributes; |
232 | $c->res->body($attributes->{Bar}[0] ); |
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233 | } |
234 | |
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235 | will set the response body to C<Baz>. The values always come in an |
236 | array reference. As you can see, you can use attributes to configure |
237 | your actions. You can specify or alter these attributes via |
238 | L</"Component Configuration">, or even react on them as soon as |
239 | Catalyst encounters them by providing your own L<component base |
240 | class|/"Component Base Classes">. |
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241 | |
242 | =head2 Creating custom accessors |
243 | |
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244 | L<Catalyst::Component> uses L<Class::Accessor::Fast> for accessor |
245 | creation. Please refer to the modules documentation for usage |
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246 | information. |
247 | |
248 | =head2 Component configuration |
249 | |
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250 | At creation time, the class configuration of your component (the one |
251 | available via C<$self-E<gt>config>) will be merged with possible |
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252 | configuration settings from the applications configuration (either |
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253 | directly or via config file). This is then stored in the controller |
254 | object's hash reference. So, if you read possible configurations like: |
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255 | |
256 | my $model_name = $controller->{model_name}; |
257 | |
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258 | you will get the right value. The C<config> accessor always only |
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259 | contains the original class configuration and must not be used for |
260 | component configuration. |
261 | |
262 | You are advised to create accessors on your component class for your |
263 | configuration values. This is good practice and makes it easier to |
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264 | capture configuration key typos. You can do this with the |
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265 | C<mk_ro_accessors> method provided to L<Catalyst::Component> via |
266 | L<Class::Accessor::Fast>: |
267 | |
268 | use base 'Catalyst::Controller'; |
269 | __PACKAGE__->mk_ro_accessors('model_name'); |
270 | ... |
271 | my $model_name = $controller->model_name; |
272 | |
273 | =head1 IMPLEMENTATION |
274 | |
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275 | This part contains the technical details of various implementation |
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276 | methods. Please read the L</"BEST PRACTICES"> before you start your |
277 | implementation, if you haven't already. |
278 | |
279 | =head2 Action classes |
280 | |
281 | Usually, your action objects are of the class L<Catalyst::Action>. |
282 | You can override this with the C<ActionClass> attribute to influence |
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283 | execution and/or dispatching of the action. A widely used example of |
284 | this is L<Catalyst::Action::RenderView>, which is used in every newly |
285 | created Catalyst application in your root controller: |
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286 | |
287 | sub end : ActionClass('RenderView') { } |
288 | |
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289 | Usually, you want to override the C<execute> and/or the C<match> |
290 | method. The execute method of the action will naturally call the |
291 | methods code. You can surround this by overriding the method in a |
292 | subclass: |
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293 | |
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294 | package Catalyst::Action::MyFoo; |
295 | use strict; |
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296 | |
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297 | use MRO::Compat; |
298 | use base 'Catalyst::Action'; |
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299 | |
300 | sub execute { |
301 | my $self = shift; |
302 | my ($controller, $c, @args) = @_; |
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303 | # put your 'before' code here |
304 | my $r = $self->next::method(@_); |
305 | # put your 'after' code here |
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306 | return $r; |
307 | } |
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308 | 1; |
309 | |
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310 | We are using L<MRO::Compat> to ensure that you have the next::method |
311 | call, from L<Class::C3> (in older perls), or natively (if you are using |
312 | perl 5.10) to re-dispatch to the original C<execute> method in the |
313 | L<Catalyst::Action> class. |
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314 | |
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315 | The Catalyst dispatcher handles an incoming request and, depending |
316 | upon the dispatch type, will call the appropriate target or chain. |
317 | From time to time it asks the actions themselves, or through the |
318 | controller, if they would match the current request. That's what the |
319 | C<match> method does. So by overriding this, you can change on what |
320 | the action will match and add new matching criteria. |
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321 | |
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322 | For example, the action class below will make the action only match on |
323 | Mondays: |
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324 | |
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325 | package Catalyst::Action::OnlyMondays; |
326 | use strict; |
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327 | |
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328 | use MRO::Compat; |
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329 | use base 'Catalyst::Action'; |
330 | |
331 | sub match { |
332 | my $self = shift; |
333 | return 0 if ( localtime(time) )[6] == 1; |
334 | return $self->next::method(@_); |
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335 | } |
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336 | 1; |
337 | |
338 | And this is how we'd use it: |
339 | |
340 | sub foo: Local ActionClass('OnlyMondays') { |
341 | my ($self, $c) = @_; |
342 | $c->res->body('I feel motivated!'); |
343 | } |
344 | |
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345 | If you are using action classes often or have some specific base |
346 | classes that you want to specify more conveniently, you can implement |
347 | a component base class providing an attribute handler. |
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348 | |
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349 | For further information on action classes, please refer to |
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350 | L<Catalyst::Action> and L<Catalyst::Manual::Actions>. |
351 | |
352 | =head2 Component base classes |
353 | |
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354 | Many L<Catalyst::Plugin> that were written in Catalyst's early days |
355 | should really have been just controller base classes. With such a |
356 | class, you could provide functionality scoped to a single controller, |
357 | not polluting the global namespace in the context object. |
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358 | |
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359 | You can provide regular Perl methods in a base class as well as |
360 | actions which will be inherited to the subclass. Please refer to |
361 | L</Controllers> for an example of this. |
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362 | |
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363 | You can introduce your own attributes by specifying a handler method |
364 | in the controller base. For example, to use a C<FullClass> attribute |
365 | to specify a fully qualified action class name, you could use the |
366 | following implementation. Note, however, that this functionality is |
367 | already provided via the C<+> prefix for action classes. A simple |
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368 | |
369 | sub foo : Local ActionClass('+MyApp::Action::Bar') { ... } |
370 | |
371 | will use C<MyApp::Action::Bar> as action class. |
372 | |
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373 | package MyApp::Base::Controller::FullClass; use strict; use base |
374 | 'Catalyst::Controller'; |
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375 | |
376 | sub _parse_FullClass_attr { |
377 | my ($self, $app_class, $action_name, $value, $attrs) = @_; |
378 | return( ActionClass => $value ); |
379 | } |
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380 | 1; |
381 | |
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382 | Note that the full line of arguments is only provided for completeness |
383 | sake. We could use this attribute in a subclass like any other |
384 | Catalyst attribute: |
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385 | |
386 | package MyApp::Controller::Foo; |
387 | use strict; |
388 | use base 'MyApp::Base::Controller::FullClass'; |
389 | |
390 | sub foo : Local FullClass('MyApp::Action::Bar') { ... } |
391 | |
392 | 1; |
393 | |
394 | =head2 Controllers |
395 | |
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396 | Many things can happen in controllers, and it often improves |
397 | maintainability to abstract some of the code out into reusable base |
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398 | classes. |
399 | |
400 | You can provide usual Perl methods that will be available via your |
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401 | controller object, or you can even define Catalyst actions which will |
402 | be inherited by the subclasses. Consider this controller base class: |
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403 | |
404 | package MyApp::Base::Controller::ModelBase; |
405 | use strict; |
406 | use base 'Catalyst::Controller'; |
407 | |
408 | sub list : Chained('base') PathPart('') Args(0) { |
409 | my ($self, $c) = @_; |
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410 | my $model = $c->model( $self->{model_name} ); |
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411 | my $condition = $self->{model_search_condition} || {}; |
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412 | my $attrs = $self->{model_search_attrs} || {}; |
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413 | $c->stash(rs => $model->search($condition, $attrs); |
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414 | } |
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415 | |
416 | sub load : Chained('base') PathPart('') CaptureArgs(1) { |
417 | my ($self, $c, $id) = @_; |
418 | my $model = $c->model( $self->{model_name} ); |
419 | $c->stash(row => $model->find($id)); |
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420 | } |
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421 | 1; |
422 | |
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423 | This example implements two simple actions. The C<list> action chains |
424 | to a (currently non-existent) C<base> action and puts a result-set |
425 | into the stash taking a configured C<model_name> as well as a search |
426 | condition and attributes. This action is a |
427 | L<chained|Catalyst::DispatchType::Chained> endpoint. The other action, |
428 | called C< load > is a chain midpoint that takes one argument. It takes |
429 | the value as an ID and loads the row from the configured model. Please |
430 | not that the above code is simplified for clarity. It misses error |
431 | handling, input validation, and probably other things. |
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432 | |
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433 | The class above is not very useful on its own, but we can combine it |
434 | with some custom actions by sub-classing it: |
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435 | |
436 | package MyApp::Controller::Foo; |
437 | use strict; |
438 | use base 'MyApp::Base::Controller::ModelBase'; |
439 | |
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440 | __PACKAGE__->config( model_name => 'DB::Foo', |
441 | model_search_condition=> { is_active => 1 }, |
442 | model_search_attrs => { order_by => 'name' }, |
443 | ); |
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444 | |
445 | sub base : Chained PathPart('foo') CaptureArgs(0) { } |
446 | |
447 | sub view : Chained('load') Args(0) { |
448 | my ($self, $c) = @_; |
449 | my $row = $c->stash->{row}; |
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450 | $c->res->body(join ': ', $row->name, |
451 | $row->description); } |
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452 | 1; |
453 | |
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454 | This class uses the formerly created controller as a base |
455 | class. First, we see the configurations that were used in the parent |
456 | class. Next comes the C<base> action, where everything chains off of. |
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457 | |
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458 | Note that inherited actions act like they were declared in your |
459 | controller itself. You can therefor call them just by their name in |
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460 | C<forward>s, C<detaches> and C<Chained(..)> specifications. This is an |
461 | important part of what makes this technique so useful. |
462 | |
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463 | The new C<view> action ties itself to the C<load> action specified in |
464 | the base class and outputs the loaded row's C<name> and C<description> |
465 | columns. The controller C<MyApp::Controller::Foo> now has these |
466 | publicly available paths: |
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467 | |
468 | =over |
469 | |
470 | =item /foo |
471 | |
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472 | Will call the controller's C<base>, then the base classes C<list> |
473 | action. |
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474 | |
475 | =item /foo/$id/view |
476 | |
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477 | First, the controller's C<base> will be called, then it will C<load> |
478 | the row with the corresponding C<$id>. After that, C<view> will |
479 | display some fields out of the object. |
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480 | |
481 | =back |
482 | |
483 | =head2 Models and Views |
484 | |
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485 | If the functionality you'd like to add is really a data-set that you |
486 | want to manipulate, for example internal document types, images, |
487 | files, it might be better suited as a model. |
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488 | |
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489 | The same applies for views. If your code handles representation or |
490 | deals with the applications interface and should be universally |
491 | available, it could be a perfect candidate for a view. |
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492 | |
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493 | Please implement a C<process> method in your views. This method will |
494 | be called by Catalyst if it is asked to forward to a component without |
495 | a specified action. Note that C<process> is B<not a Catalyst action> |
496 | but a simple Perl method. |
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497 | |
498 | You are also encouraged to implement a C<render> method corresponding |
499 | with the one in L<Catalyst::View::TT>. This has proven invaluable, |
500 | because people can use your view for much more fine-grained content |
501 | generation. |
502 | |
503 | Here is some example code for a fictional view: |
504 | |
505 | package CatalystX::View::MyView; |
506 | use strict; |
507 | use base 'Catalyst::View'; |
508 | |
509 | sub process { |
510 | my ($self, $c) = @_; |
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511 | my $template = $c->stash->{template}; |
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512 | my $content = $self->render($c, $template, $c->stash); |
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513 | $c->res->body( $content ); |
514 | } |
515 | |
516 | sub render { |
517 | my ($self, $c, $template, $args) = @_; |
b7c570ac |
518 | # prepare content here |
38017482 |
519 | return $content; |
520 | } |
38017482 |
521 | 1; |
522 | |
523 | =head2 Plugins |
524 | |
b7c570ac |
525 | The first thing to say about plugins is that if you're not sure if |
526 | your module should be a plugin, it probably shouldn't. It once was |
527 | common to add features to Catalyst by writing plugins that provide |
528 | accessors to said functionality. As Catalyst grew more popular, it |
529 | became obvious that this qualifies as bad practice. |
530 | |
531 | By designing your module as a Catalyst plugin, every method you |
532 | implement, import or inherit will be available via your applications |
533 | context object. A plugin pollutes the global namespace, and you |
534 | should be only doing that when you really need to. |
535 | |
536 | Often, developers design extensions as plugins because they need to |
537 | get hold of the context object. Either to get at the stash or |
538 | request/response objects are the widely spread reasons. It is, |
539 | however, perfectly possible to implement a regular Catalyst component |
540 | (read: model, view or controller) that receives the current context |
541 | object via L<Catalyst::Component/"ACCEPT_CONTEXT($c, @args)">. |
542 | |
543 | When is a plugin suited to your task? Your code needs to be a |
544 | plugin to act upon or alter specific parts of Catalyst's request |
78170776 |
545 | lifecycle. If your functionality needs to change some C<prepare_*> or |
b7c570ac |
546 | C<finalize_*> stages, you won't get around a plugin. |
547 | |
78170776 |
548 | Note, if you just want to hook into such a stage, and run code before, |
549 | or after it, then it is recommended that you use L<Moose>s method modifiers |
550 | to do this. |
551 | |
b7c570ac |
552 | Another valid target for a plugin architecture are things that |
553 | B<really> have to be globally available, like sessions or |
554 | authentication. |
555 | |
556 | B<Please do not> release Catalyst extensions as plugins only to |
557 | provide some functionality application wide. Design it as a controller |
558 | base class or another suiting technique with a smaller scope, so that |
559 | your code only influences those parts of the application where it is |
560 | needed, and namespace clashes and conflicts are ruled out. |
38017482 |
561 | |
562 | The implementation is pretty easy. Your plugin will be inserted in the |
563 | application's inheritance list, above Catalyst itself. You can by this |
b7c570ac |
564 | alter Catalyst's request lifecycle behaviour. Every method you |
565 | declare, every import in your package will be available as method on |
566 | the application and the context object. As an example, let's say you |
78170776 |
567 | want Catalyst to warn you every time uri_for was called without an action |
568 | object as the first parameter, for example to test that all your chained |
569 | uris are generated from actions (a recommended best practice). |
570 | You could do this with this simple |
38017482 |
571 | implementation (excuse the lame class name, it's just an example): |
572 | |
573 | package Catalyst::Plugin::UriforUndefWarning; |
574 | use strict; |
78170776 |
575 | use Scalar::Util qw/blessed/; |
20a4dd98 |
576 | use MRO::Compat; |
38017482 |
577 | |
578 | sub uri_for { |
b7c570ac |
579 | my $c = shift; |
38017482 |
580 | my $uri = $c->next::method(@_); |
78170776 |
581 | $c->log->warn( 'uri_for with non action: ', join(', ', @_), ) |
582 | if (!blessed($_[0]) || !$_[0]->isa('Catalyst::Action')); |
38017482 |
583 | return $uri; |
584 | } |
585 | |
586 | 1; |
587 | |
b7c570ac |
588 | This would override Catalyst's C<uri_for> method and emit a C<warn> |
78170776 |
589 | log entry containing the arguments to uri_for. |
590 | |
591 | Please note this is not a practical example, as string URLs are fine for |
592 | static content etc. |
593 | |
594 | A simple example like this is actually better as a L<Moose> role, for example: |
595 | |
596 | package CatalystX::UriforUndefWarning; |
597 | use Moose::Role; |
598 | use namespace::clean -except => 'meta'; |
599 | |
600 | after 'uri_for' => sub { |
601 | my ($c, $arg) = @_; |
602 | $c->log->warn( 'uri_for with non action: ', join(', ', @_), ) |
603 | if (!blessed($_[0]) || !$_[0]->isa('Catalyst::Action')); |
604 | return $uri; |
605 | }; |
38017482 |
606 | |
607 | =head2 Factory components with COMPONENT() |
608 | |
b7c570ac |
609 | Every component inheriting from L<Catalyst::Component> contains a |
610 | C<COMPONENT> method. It is used on application startup by |
611 | C<setup_components> to instantiate the component object for the |
612 | Catalyst application. By default, this will merge the components own |
613 | C<config>uration with the application wide overrides and call the |
614 | class' C<new> method to return the component object. |
38017482 |
615 | |
b7c570ac |
616 | You can override this method and do and return whatever you want. |
20a4dd98 |
617 | However, you should use L<Class::C3> (via L<MRO::Compat>) to forward |
618 | to the original C<COMPONENT> method to merge the configuration of |
619 | your component. |
38017482 |
620 | |
621 | Here is a stub C<COMPONENT> method: |
622 | |
623 | package CatalystX::Component::Foo; |
624 | use strict; |
625 | use base 'Catalyst::Component'; |
626 | |
20a4dd98 |
627 | use MRO::Compat; |
38017482 |
628 | |
629 | sub COMPONENT { |
630 | my $class = shift; |
631 | my ($app_class, $config) = @_; |
632 | |
b7c570ac |
633 | # do things here before instantiation my |
634 | $obj = $self->next::method(@_); |
38017482 |
635 | # do things to object after instantiation |
38017482 |
636 | return $object; |
637 | } |
638 | |
639 | The arguments are the class name of the component, the class name of |
b7c570ac |
640 | the application instantiating the component, and a hash reference with |
641 | the controller's configuration. |
38017482 |
642 | |
b7c570ac |
643 | You are free to re-bless the object, instantiate a whole other |
644 | component or really do anything compatible with Catalyst's |
645 | expectations on a component. |
38017482 |
646 | |
b7c570ac |
647 | For more information, please see L<Catalyst::Component/"COMPONENT($c,$arguments)">. |
38017482 |
648 | |
649 | =head1 SEE ALSO |
650 | |
b7c570ac |
651 | L<Catalyst>, L<Catalyst::Manual::Actions>, L<Catalyst::Component> |
38017482 |
652 | |
653 | =head1 AUTHOR |
654 | |
1972ebdd |
655 | Robert Sedlacek C<< <rs@474.at> >> |
656 | |
657 | Jonathan Rockway C<< <jrockway@cpan.org> >> |
38017482 |
658 | |
659 | =head1 LICENSE AND COPYRIGHT |
660 | |
b7c570ac |
661 | This document is free, you can redistribute it and/or modify it under |
38017482 |
662 | the same terms as Perl itself. |
663 | |
664 | =cut |
665 | |