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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 | Also, if you think you really need a plugin, please instead consider |
60 | using a L<Moose::Role>. |
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61 | |
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62 | =item There's a community. Use it! |
63 | |
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64 | There are many experienced developers in the Catalyst community, |
65 | there's always the IRC channel and the mailing list to discuss things. |
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66 | |
67 | =item Add tests and documentation! |
68 | |
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69 | This gives a stable basis for contribution, and even more importantly, |
70 | builds trust. The easiest way is a test application. See |
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71 | L<Catalyst::Manual::Tutorial::Testing> for more information. |
72 | |
73 | =back |
74 | |
75 | =head2 Namespaces |
76 | |
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77 | While some core extensions (engines, plugins, etc.) have to be placed |
78 | in the C<Catalyst::*> namespace, the Catalyst core would like to ask |
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79 | developers to use the C<CatalystX::*> namespace if possible. |
80 | |
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81 | Please B<do not> invent components which are outside the well |
82 | known C<Model>, C<View>, C<Controller> or C<Plugin> namespaces! |
83 | |
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84 | When you try to put a base class for a C<Model>, C<View> or |
85 | C<Controller> directly under your C<MyApp> directory as, for example, |
86 | C<MyApp::Controller::Foo>, you will have the problem that Catalyst |
87 | will try to load that base class as a component of your |
88 | application. The solution is simple: Use another namespace. Common |
89 | ones are C<MyApp::Base::Controller::*> or C<MyApp::ControllerBase::*> |
90 | as examples. |
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91 | |
92 | =head2 Can it be a simple module? |
93 | |
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94 | Sometimes you want to use functionality in your application that |
95 | doesn't require the framework at all. Remember that Catalyst is just |
96 | Perl and you always can just C<use> a module. If you have application |
97 | specific code that doesn't need the framework, there is no problem in |
98 | putting it in your C<MyApp::*> namespace. Just don't put it in |
99 | C<Model>, C<Controller> or C<View>, because that would make Catalyst |
100 | try to load them as components. |
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101 | |
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102 | Writing a generic component that only works with Catalyst is wasteful |
103 | of your time. Try writing a plain perl module, and then a small bit |
104 | of glue that integrates it with Catalyst. See |
105 | L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> for a |
106 | module that takes the approach. The advantage here is that your |
107 | "Catalyst" DBIC schema works perfectly outside of Catalyst, making |
108 | testing (and command-line scripts) a breeze. The actual Catalyst |
109 | Model is just a few lines of glue that makes working with the schema |
110 | convenient. |
111 | |
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112 | If you want the thinnest interface possible, take a look at |
113 | L<Catalyst::Model::Adaptor|Catalyst::Model::Adaptor>. |
114 | |
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115 | =head2 Using Moose roles to apply method modifiers |
116 | |
117 | Rather than having a complex set of base classes which you have to mixin |
118 | via multiple inheritence, if your functionality is well structured, then |
119 | it's possible to use the composability of L<Moose> roles, and method modifiers |
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120 | to hook onto to provide functionality. |
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121 | |
122 | For a simple example of this, see L<CatalystX::REPL>. |
123 | |
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124 | =head2 Inheritance and overriding methods |
125 | |
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126 | When overriding a method, keep in mind that some day additionally |
127 | arguments may be provided to the method, if the last parameter is not |
128 | a flat list. It is thus better to override a method by shifting the |
129 | invocant off of C<@_> and assign the rest of the used arguments, so |
130 | you can pass your complete arguments to the original method via C<@_>: |
131 | |
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132 | use MRO::Compat; ... |
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133 | |
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134 | sub foo { |
135 | my $self = shift; |
136 | my ($bar, $baz) = @_; # ... return |
137 | $self->next::method(@_); |
138 | } |
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139 | |
140 | If you would do the common |
141 | |
142 | my ($self, $foo, $bar) = @_; |
143 | |
144 | you'd have to use a much uglier construct to ensure that all arguments |
145 | will be passed along and the method is future proof: |
146 | |
147 | $self->next::method(@_[ 1 .. $#_ ]); |
148 | |
149 | =head2 Tests and documentation |
150 | |
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151 | When you release your module to the CPAN, proper documentation and at |
152 | least a basic test suite (which means more than pod or even just |
153 | C<use_ok>, sorry) gives people a good base to contribute to the |
154 | module. It also shows that you care for your users. If you would like |
155 | your module to become a recommended addition, these things will prove |
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156 | invaluable. |
157 | |
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158 | If you're just getting started, try using |
159 | L<CatalystX::Starter|CatalystX::Starter> to generate some example |
160 | tests for your module. |
161 | |
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162 | =head2 Maintenance |
163 | |
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164 | In planning to release a module to the community (Catalyst or CPAN and |
165 | Perl), you should consider if you have the resources to keep it up to |
166 | date, including fixing bugs and accepting contributions. |
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167 | |
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168 | If you're not sure about this, you can always ask in the proper |
169 | Catalyst or Perl channels if someone else might be interested in the |
170 | project, and would jump in as co-maintainer. |
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171 | |
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172 | A public repository can further ease interaction with the |
173 | community. Even read only access enables people to provide you with |
174 | patches to your current development version. subversion, SVN and SVK, |
175 | are broadly preferred in the Catalyst community. |
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176 | |
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177 | If you're developing a Catalyst extension, please consider asking the |
178 | core team for space in Catalyst's own subversion repository. You can |
179 | get in touch about this via IRC or the Catalyst developers mailing |
180 | list. |
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181 | |
182 | =head2 The context object |
183 | |
184 | Sometimes you want to get a hold of the context object in a component |
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185 | that was created on startup time, where no context existed yet. Often |
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186 | this is about the model reading something out of the stash or other |
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187 | context information (current language, for example). |
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188 | |
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189 | If you use the context object in your component you have tied it to an |
190 | existing request. This means that you might get into problems when |
191 | you try to use the component (e.g. the model - the most common case) |
192 | outside of Catalyst, for example in cronjobs. |
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193 | |
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194 | A stable solution to this problem is to design the Catalyst model |
195 | separately from the underlying model logic. Let's take |
196 | L<Catalyst::Model::DBIC::Schema> as an example. You can create a |
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197 | schema outside of Catalyst that knows nothing about the web. This kind |
198 | of design ensures encapsulation and makes development and maintenance |
199 | a whole lot easier. The you use the aforementioned model to tie your |
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200 | schema to your application. This gives you a C<MyApp::DBIC> (the name |
201 | is of course just an example) model as well as |
202 | C<MyApp::DBIC::TableName> models to access your result sources |
203 | directly. |
204 | |
205 | By creating such a thin layer between the actual model and the |
206 | Catalyst application, the schema itself is not at all tied to any |
207 | application and the layer in-between can access the model's API using |
208 | information from the context object. |
209 | |
210 | A Catalyst component accesses the context object at request time with |
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211 | L<Catalyst::Component/"ACCEPT_CONTEXT($c, @args)">. |
212 | |
213 | =head1 CONFIGURATION |
214 | |
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215 | The application has to interact with the extension with some |
216 | configuration. There is of course again more than one way to do it. |
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217 | |
218 | =head2 Attributes |
219 | |
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220 | You can specify any valid Perl attribute on Catalyst actions you like. |
221 | (See L<attributes/"Syntax of Attribute Lists"> for a description of |
222 | what is valid.) These will be available on the C<Catalyst::Action> |
223 | instance via its C<attributes> accessor. To give an example, this |
224 | action: |
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225 | |
226 | sub foo : Local Bar('Baz') { |
227 | my ($self, $c) = @_; |
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228 | my $attributes = |
229 | $self->action_for('foo')->attributes; |
230 | $c->res->body($attributes->{Bar}[0] ); |
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231 | } |
232 | |
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233 | will set the response body to C<Baz>. The values always come in an |
234 | array reference. As you can see, you can use attributes to configure |
235 | your actions. You can specify or alter these attributes via |
236 | L</"Component Configuration">, or even react on them as soon as |
237 | Catalyst encounters them by providing your own L<component base |
238 | class|/"Component Base Classes">. |
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239 | |
240 | =head2 Creating custom accessors |
241 | |
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242 | L<Catalyst::Component> uses L<Class::Accessor::Fast> for accessor |
243 | creation. Please refer to the modules documentation for usage |
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244 | information. |
245 | |
246 | =head2 Component configuration |
247 | |
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248 | At creation time, the class configuration of your component (the one |
249 | available via C<$self-E<gt>config>) will be merged with possible |
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250 | configuration settings from the applications configuration (either |
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251 | directly or via config file). This is then stored in the controller |
252 | object's hash reference. So, if you read possible configurations like: |
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253 | |
254 | my $model_name = $controller->{model_name}; |
255 | |
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256 | you will get the right value. The C<config> accessor always only |
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257 | contains the original class configuration and must not be used for |
258 | component configuration. |
259 | |
260 | You are advised to create accessors on your component class for your |
261 | configuration values. This is good practice and makes it easier to |
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262 | capture configuration key typos. You can do this with the |
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263 | C<mk_ro_accessors> method provided to L<Catalyst::Component> via |
264 | L<Class::Accessor::Fast>: |
265 | |
266 | use base 'Catalyst::Controller'; |
267 | __PACKAGE__->mk_ro_accessors('model_name'); |
268 | ... |
269 | my $model_name = $controller->model_name; |
270 | |
271 | =head1 IMPLEMENTATION |
272 | |
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273 | This part contains the technical details of various implementation |
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274 | methods. Please read the L</"BEST PRACTICES"> before you start your |
275 | implementation, if you haven't already. |
276 | |
277 | =head2 Action classes |
278 | |
279 | Usually, your action objects are of the class L<Catalyst::Action>. |
280 | You can override this with the C<ActionClass> attribute to influence |
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281 | execution and/or dispatching of the action. A widely used example of |
282 | this is L<Catalyst::Action::RenderView>, which is used in every newly |
283 | created Catalyst application in your root controller: |
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284 | |
285 | sub end : ActionClass('RenderView') { } |
286 | |
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287 | Usually, you want to override the C<execute> and/or the C<match> |
288 | method. The execute method of the action will naturally call the |
289 | methods code. You can surround this by overriding the method in a |
290 | subclass: |
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291 | |
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292 | package Catalyst::Action::MyFoo; |
293 | use strict; |
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294 | |
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295 | use MRO::Compat; |
296 | use base 'Catalyst::Action'; |
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297 | |
298 | sub execute { |
299 | my $self = shift; |
300 | my ($controller, $c, @args) = @_; |
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301 | # put your 'before' code here |
302 | my $r = $self->next::method(@_); |
303 | # put your 'after' code here |
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304 | return $r; |
305 | } |
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306 | 1; |
307 | |
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308 | We are using L<MRO::Compat> to ensure that you have the next::method |
309 | call, from L<Class::C3> (in older perls), or natively (if you are using |
310 | perl 5.10) to re-dispatch to the original C<execute> method in the |
311 | L<Catalyst::Action> class. |
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312 | |
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313 | The Catalyst dispatcher handles an incoming request and, depending |
314 | upon the dispatch type, will call the appropriate target or chain. |
315 | From time to time it asks the actions themselves, or through the |
316 | controller, if they would match the current request. That's what the |
317 | C<match> method does. So by overriding this, you can change on what |
318 | the action will match and add new matching criteria. |
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319 | |
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320 | For example, the action class below will make the action only match on |
321 | Mondays: |
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322 | |
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323 | package Catalyst::Action::OnlyMondays; |
324 | use strict; |
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325 | |
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326 | use MRO::Compat; |
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327 | use base 'Catalyst::Action'; |
328 | |
329 | sub match { |
330 | my $self = shift; |
331 | return 0 if ( localtime(time) )[6] == 1; |
332 | return $self->next::method(@_); |
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333 | } |
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334 | 1; |
335 | |
336 | And this is how we'd use it: |
337 | |
338 | sub foo: Local ActionClass('OnlyMondays') { |
339 | my ($self, $c) = @_; |
340 | $c->res->body('I feel motivated!'); |
341 | } |
342 | |
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343 | If you are using action classes often or have some specific base |
344 | classes that you want to specify more conveniently, you can implement |
345 | a component base class providing an attribute handler. |
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346 | |
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347 | For further information on action classes, please refer to |
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348 | L<Catalyst::Action> and L<Catalyst::Manual::Actions>. |
349 | |
350 | =head2 Component base classes |
351 | |
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352 | Many L<Catalyst::Plugin> that were written in Catalyst's early days |
353 | should really have been just controller base classes. With such a |
354 | class, you could provide functionality scoped to a single controller, |
355 | not polluting the global namespace in the context object. |
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356 | |
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357 | You can provide regular Perl methods in a base class as well as |
358 | actions which will be inherited to the subclass. Please refer to |
359 | L</Controllers> for an example of this. |
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360 | |
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361 | You can introduce your own attributes by specifying a handler method |
362 | in the controller base. For example, to use a C<FullClass> attribute |
363 | to specify a fully qualified action class name, you could use the |
364 | following implementation. Note, however, that this functionality is |
365 | already provided via the C<+> prefix for action classes. A simple |
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366 | |
367 | sub foo : Local ActionClass('+MyApp::Action::Bar') { ... } |
368 | |
369 | will use C<MyApp::Action::Bar> as action class. |
370 | |
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371 | package MyApp::Base::Controller::FullClass; use strict; use base |
372 | 'Catalyst::Controller'; |
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373 | |
374 | sub _parse_FullClass_attr { |
375 | my ($self, $app_class, $action_name, $value, $attrs) = @_; |
376 | return( ActionClass => $value ); |
377 | } |
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378 | 1; |
379 | |
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380 | Note that the full line of arguments is only provided for completeness |
381 | sake. We could use this attribute in a subclass like any other |
382 | Catalyst attribute: |
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383 | |
384 | package MyApp::Controller::Foo; |
385 | use strict; |
386 | use base 'MyApp::Base::Controller::FullClass'; |
387 | |
388 | sub foo : Local FullClass('MyApp::Action::Bar') { ... } |
389 | |
390 | 1; |
391 | |
392 | =head2 Controllers |
393 | |
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394 | Many things can happen in controllers, and it often improves |
395 | maintainability to abstract some of the code out into reusable base |
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396 | classes. |
397 | |
398 | You can provide usual Perl methods that will be available via your |
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399 | controller object, or you can even define Catalyst actions which will |
400 | be inherited by the subclasses. Consider this controller base class: |
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401 | |
402 | package MyApp::Base::Controller::ModelBase; |
403 | use strict; |
404 | use base 'Catalyst::Controller'; |
405 | |
406 | sub list : Chained('base') PathPart('') Args(0) { |
407 | my ($self, $c) = @_; |
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408 | my $model = $c->model( $self->{model_name} ); |
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409 | my $condition = $self->{model_search_condition} || {}; |
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410 | my $attrs = $self->{model_search_attrs} || {}; |
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411 | $c->stash(rs => $model->search($condition, $attrs); |
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412 | } |
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413 | |
414 | sub load : Chained('base') PathPart('') CaptureArgs(1) { |
415 | my ($self, $c, $id) = @_; |
416 | my $model = $c->model( $self->{model_name} ); |
417 | $c->stash(row => $model->find($id)); |
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418 | } |
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419 | 1; |
420 | |
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421 | This example implements two simple actions. The C<list> action chains |
422 | to a (currently non-existent) C<base> action and puts a result-set |
423 | into the stash taking a configured C<model_name> as well as a search |
424 | condition and attributes. This action is a |
425 | L<chained|Catalyst::DispatchType::Chained> endpoint. The other action, |
426 | called C< load > is a chain midpoint that takes one argument. It takes |
427 | the value as an ID and loads the row from the configured model. Please |
428 | not that the above code is simplified for clarity. It misses error |
429 | handling, input validation, and probably other things. |
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430 | |
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431 | The class above is not very useful on its own, but we can combine it |
432 | with some custom actions by sub-classing it: |
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433 | |
434 | package MyApp::Controller::Foo; |
435 | use strict; |
436 | use base 'MyApp::Base::Controller::ModelBase'; |
437 | |
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438 | __PACKAGE__->config( model_name => 'DB::Foo', |
439 | model_search_condition=> { is_active => 1 }, |
440 | model_search_attrs => { order_by => 'name' }, |
441 | ); |
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442 | |
443 | sub base : Chained PathPart('foo') CaptureArgs(0) { } |
444 | |
445 | sub view : Chained('load') Args(0) { |
446 | my ($self, $c) = @_; |
447 | my $row = $c->stash->{row}; |
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448 | $c->res->body(join ': ', $row->name, |
449 | $row->description); } |
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450 | 1; |
451 | |
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452 | This class uses the formerly created controller as a base |
453 | class. First, we see the configurations that were used in the parent |
454 | class. Next comes the C<base> action, where everything chains off of. |
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455 | |
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456 | Note that inherited actions act like they were declared in your |
457 | controller itself. You can therefor call them just by their name in |
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458 | C<forward>s, C<detaches> and C<Chained(..)> specifications. This is an |
459 | important part of what makes this technique so useful. |
460 | |
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461 | The new C<view> action ties itself to the C<load> action specified in |
462 | the base class and outputs the loaded row's C<name> and C<description> |
463 | columns. The controller C<MyApp::Controller::Foo> now has these |
464 | publicly available paths: |
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465 | |
466 | =over |
467 | |
468 | =item /foo |
469 | |
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470 | Will call the controller's C<base>, then the base classes C<list> |
471 | action. |
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472 | |
473 | =item /foo/$id/view |
474 | |
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475 | First, the controller's C<base> will be called, then it will C<load> |
476 | the row with the corresponding C<$id>. After that, C<view> will |
477 | display some fields out of the object. |
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478 | |
479 | =back |
480 | |
481 | =head2 Models and Views |
482 | |
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483 | If the functionality you'd like to add is really a data-set that you |
484 | want to manipulate, for example internal document types, images, |
485 | files, it might be better suited as a model. |
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486 | |
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487 | The same applies for views. If your code handles representation or |
488 | deals with the applications interface and should be universally |
489 | available, it could be a perfect candidate for a view. |
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490 | |
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491 | Please implement a C<process> method in your views. This method will |
492 | be called by Catalyst if it is asked to forward to a component without |
493 | a specified action. Note that C<process> is B<not a Catalyst action> |
494 | but a simple Perl method. |
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495 | |
496 | You are also encouraged to implement a C<render> method corresponding |
497 | with the one in L<Catalyst::View::TT>. This has proven invaluable, |
498 | because people can use your view for much more fine-grained content |
499 | generation. |
500 | |
501 | Here is some example code for a fictional view: |
502 | |
503 | package CatalystX::View::MyView; |
504 | use strict; |
505 | use base 'Catalyst::View'; |
506 | |
507 | sub process { |
508 | my ($self, $c) = @_; |
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509 | my $template = $c->stash->{template}; |
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510 | my $content = $self->render($c, $template, $c->stash); |
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511 | $c->res->body( $content ); |
512 | } |
513 | |
514 | sub render { |
515 | my ($self, $c, $template, $args) = @_; |
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516 | # prepare content here |
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517 | return $content; |
518 | } |
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519 | 1; |
520 | |
521 | =head2 Plugins |
522 | |
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523 | The first thing to say about plugins is that if you're not sure if |
524 | your module should be a plugin, it probably shouldn't. It once was |
525 | common to add features to Catalyst by writing plugins that provide |
526 | accessors to said functionality. As Catalyst grew more popular, it |
527 | became obvious that this qualifies as bad practice. |
528 | |
529 | By designing your module as a Catalyst plugin, every method you |
530 | implement, import or inherit will be available via your applications |
531 | context object. A plugin pollutes the global namespace, and you |
532 | should be only doing that when you really need to. |
533 | |
534 | Often, developers design extensions as plugins because they need to |
535 | get hold of the context object. Either to get at the stash or |
536 | request/response objects are the widely spread reasons. It is, |
537 | however, perfectly possible to implement a regular Catalyst component |
538 | (read: model, view or controller) that receives the current context |
539 | object via L<Catalyst::Component/"ACCEPT_CONTEXT($c, @args)">. |
540 | |
541 | When is a plugin suited to your task? Your code needs to be a |
542 | plugin to act upon or alter specific parts of Catalyst's request |
78170776 |
543 | lifecycle. If your functionality needs to change some C<prepare_*> or |
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544 | C<finalize_*> stages, you won't get around a plugin. |
545 | |
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546 | Note, if you just want to hook into such a stage, and run code before, |
547 | or after it, then it is recommended that you use L<Moose>s method modifiers |
548 | to do this. |
549 | |
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550 | Another valid target for a plugin architecture are things that |
551 | B<really> have to be globally available, like sessions or |
552 | authentication. |
553 | |
554 | B<Please do not> release Catalyst extensions as plugins only to |
555 | provide some functionality application wide. Design it as a controller |
556 | base class or another suiting technique with a smaller scope, so that |
557 | your code only influences those parts of the application where it is |
558 | needed, and namespace clashes and conflicts are ruled out. |
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559 | |
560 | The implementation is pretty easy. Your plugin will be inserted in the |
561 | application's inheritance list, above Catalyst itself. You can by this |
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562 | alter Catalyst's request lifecycle behaviour. Every method you |
563 | declare, every import in your package will be available as method on |
564 | the application and the context object. As an example, let's say you |
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565 | want Catalyst to warn you every time uri_for was called without an action |
566 | object as the first parameter, for example to test that all your chained |
567 | uris are generated from actions (a recommended best practice). |
568 | You could do this with this simple |
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569 | implementation (excuse the lame class name, it's just an example): |
570 | |
571 | package Catalyst::Plugin::UriforUndefWarning; |
572 | use strict; |
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573 | use Scalar::Util qw/blessed/; |
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574 | use MRO::Compat; |
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575 | |
576 | sub uri_for { |
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577 | my $c = shift; |
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578 | my $uri = $c->next::method(@_); |
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579 | $c->log->warn( 'uri_for with non action: ', join(', ', @_), ) |
580 | if (!blessed($_[0]) || !$_[0]->isa('Catalyst::Action')); |
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581 | return $uri; |
582 | } |
583 | |
584 | 1; |
585 | |
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586 | This would override Catalyst's C<uri_for> method and emit a C<warn> |
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587 | log entry containing the arguments to uri_for. |
588 | |
589 | Please note this is not a practical example, as string URLs are fine for |
590 | static content etc. |
591 | |
592 | A simple example like this is actually better as a L<Moose> role, for example: |
593 | |
594 | package CatalystX::UriforUndefWarning; |
595 | use Moose::Role; |
596 | use namespace::clean -except => 'meta'; |
597 | |
598 | after 'uri_for' => sub { |
599 | my ($c, $arg) = @_; |
600 | $c->log->warn( 'uri_for with non action: ', join(', ', @_), ) |
601 | if (!blessed($_[0]) || !$_[0]->isa('Catalyst::Action')); |
602 | return $uri; |
fa025310 |
603 | }; |
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604 | |
605 | =head2 Factory components with COMPONENT() |
606 | |
b7c570ac |
607 | Every component inheriting from L<Catalyst::Component> contains a |
608 | C<COMPONENT> method. It is used on application startup by |
609 | C<setup_components> to instantiate the component object for the |
610 | Catalyst application. By default, this will merge the components own |
611 | C<config>uration with the application wide overrides and call the |
612 | class' C<new> method to return the component object. |
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613 | |
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614 | You can override this method and do and return whatever you want. |
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615 | However, you should use L<Class::C3> (via L<MRO::Compat>) to forward |
616 | to the original C<COMPONENT> method to merge the configuration of |
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617 | your component. |
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618 | |
619 | Here is a stub C<COMPONENT> method: |
620 | |
621 | package CatalystX::Component::Foo; |
622 | use strict; |
623 | use base 'Catalyst::Component'; |
624 | |
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625 | use MRO::Compat; |
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626 | |
627 | sub COMPONENT { |
628 | my $class = shift; |
629 | my ($app_class, $config) = @_; |
630 | |
b7c570ac |
631 | # do things here before instantiation my |
632 | $obj = $self->next::method(@_); |
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633 | # do things to object after instantiation |
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634 | return $object; |
635 | } |
636 | |
637 | The arguments are the class name of the component, the class name of |
b7c570ac |
638 | the application instantiating the component, and a hash reference with |
639 | the controller's configuration. |
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640 | |
b7c570ac |
641 | You are free to re-bless the object, instantiate a whole other |
642 | component or really do anything compatible with Catalyst's |
643 | expectations on a component. |
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644 | |
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645 | For more information, please see |
646 | L<Catalyst::Component/"COMPONENT($c,$arguments)">. |
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647 | |
648 | =head1 SEE ALSO |
649 | |
b7c570ac |
650 | L<Catalyst>, L<Catalyst::Manual::Actions>, L<Catalyst::Component> |
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651 | |
652 | =head1 AUTHOR |
653 | |
1972ebdd |
654 | Robert Sedlacek C<< <rs@474.at> >> |
655 | |
656 | Jonathan Rockway C<< <jrockway@cpan.org> >> |
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657 | |
658 | =head1 LICENSE AND COPYRIGHT |
659 | |
b7c570ac |
660 | This document is free, you can redistribute it and/or modify it under |
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661 | the same terms as Perl itself. |
662 | |
663 | =cut |
664 | |