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6 Catalyst::DispatchType::Chained - Path Part DispatchType
7
9 Path part matching, allowing several actions to sequentially take care
10 of processing a request:
11 # root action - captures one argument after it
13 sub foo_setup : Chained('/') PathPart('foo') CaptureArgs(1) {
14 my ( $self, $c, $foo_arg ) = @_;
15 ...
16 }
17 # child action endpoint - takes one argument
19 sub bar : Chained('foo_setup') Args(1) {
20 my ( $self, $c, $bar_arg ) = @_;
21 ...
22 }
23
25 Dispatch type managing default behaviour. For more information on
26 dispatch types, see:
27 • Catalyst::Manual::Intro for how they affect application authors
29 • Catalyst::DispatchType for implementation information.
31
33 $self->list($c)
34 Debug output for Path Part dispatch points
35 $self->match( $c, $path )
37 Calls "recurse_match" to see if a chain matches the $path.
38 $self->recurse_match( $c, $parent, \@path_parts )
40 Recursive search for a matching chain.
41 $self->register( $c, $action )
43 Calls register_path for every Path attribute for the given $action.
44 $self->uri_for_action($action, $captures)
46 Get the URI part for the action, using $captures to fill the capturing
47 parts.
48 $c->expand_action($action)
50 Return a list of actions that represents a chained action. See
51 Catalyst::Dispatcher for more info. You probably want to use the
52 expand_action it provides rather than this directly.
53
55 Introduction
56 The "Chained" attribute allows you to chain public path parts together
57 by their private names. A chain part's path can be specified with
58 "PathPart" and can be declared to expect an arbitrary number of
59 arguments. The endpoint of the chain specifies how many arguments it
60 gets through the "Args" attribute. :Args(0) would be none at all,
61 ":Args" without an integer would be unlimited. The path parts that
62 aren't endpoints are using "CaptureArgs" to specify how many parameters
63 they expect to receive. As an example setup:
64 package MyApp::Controller::Greeting;
66 use base qw/ Catalyst::Controller /;
67 # this is the beginning of our chain
69 sub hello : PathPart('hello') Chained('/') CaptureArgs(1) {
70 my ( $self, $c, $integer ) = @_;
71 $c->stash->{ message } = "Hello ";
72 $c->stash->{ arg_sum } = $integer;
73 }
74 # this is our endpoint, because it has no :CaptureArgs
76 sub world : PathPart('world') Chained('hello') Args(1) {
77 my ( $self, $c, $integer ) = @_;
78 $c->stash->{ message } .= "World!";
79 $c->stash->{ arg_sum } += $integer;
80 $c->response->body( join "<br/>\n" =>
82 $c->stash->{ message }, $c->stash->{ arg_sum } );
83 }
84 The debug output provides a separate table for chained actions, showing
86 the whole chain as it would match and the actions it contains. Here's
87 an example of the startup output with our actions above:
88 ...
90 [debug] Loaded Path Part actions:
91 .-----------------------+------------------------------.
92 | Path Spec | Private |
93 +-----------------------+------------------------------+
94 | /hello/*/world/* | /greeting/hello (1) |
95 | | => /greeting/world |
96 '-----------------------+------------------------------'
97 ...
98 As you can see, Catalyst only deals with chains as whole paths and
100 builds one for each endpoint, which are the actions with ":Chained" but
101 without ":CaptureArgs".
102 Let's assume this application gets a request at the path
104 "/hello/23/world/12". What happens then? First, Catalyst will dispatch
105 to the "hello" action and pass the value 23 as an argument to it after
106 the context. It does so because we have previously used :CaptureArgs(1)
107 to declare that it has one path part after itself as its argument. We
108 told Catalyst that this is the beginning of the chain by specifying
109 :Chained('/'). Also note that instead of saying :PathPart('hello') we
110 could also just have said ":PathPart", as it defaults to the name of
111 the action.
112 After "hello" has run, Catalyst goes on to dispatch to the "world"
114 action. This is the last action to be called: Catalyst knows this is an
115 endpoint because we did not specify a ":CaptureArgs" attribute.
116 Nevertheless we specify that this action expects an argument, but at
117 this point we're using :Args(1) to do that. We could also have said
118 ":Args" or left it out altogether, which would mean this action would
119 get all arguments that are there. This action's ":Chained" attribute
120 says "hello" and tells Catalyst that the "hello" action in the current
121 controller is its parent.
122 With this we have built a chain consisting of two public path parts.
124 "hello" captures one part of the path as its argument, and also
125 specifies the path root as its parent. So this part is "/hello/$arg".
126 The next part is the endpoint "world", expecting one argument. It sums
127 up to the path part "world/$arg". This leads to a complete chain of
128 "/hello/$arg/world/$arg" which is matched against the requested paths.
129 This example application would, if run and called by e.g.
131 "/hello/23/world/12", set the stash value "message" to "Hello" and the
132 value "arg_sum" to "23". The "world" action would then append "World!"
133 to "message" and add 12 to the stash's "arg_sum" value. For the sake
134 of simplicity no view is shown. Instead we just put the values of the
135 stash into our body. So the output would look like:
136 Hello World!
138 35
139 And our test server would have given us this debugging output for the
141 request:
142 ...
144 [debug] "GET" request for "hello/23/world/12" from "127.0.0.1"
145 [debug] Path is "/greeting/world"
146 [debug] Arguments are "12"
147 [info] Request took 0.164113s (6.093/s)
148 .------------------------------------------+-----------.
149 | Action | Time |
150 +------------------------------------------+-----------+
151 | /greeting/hello | 0.000029s |
152 | /greeting/world | 0.000024s |
153 '------------------------------------------+-----------'
154 ...
155 What would be common uses of this dispatch technique? It gives the
157 possibility to split up logic that contains steps that each depend on
158 each other. An example would be, for example, a wiki path like
159 "/wiki/FooBarPage/rev/23/view". This chain can be easily built with
160 these actions:
161 sub wiki : PathPart('wiki') Chained('/') CaptureArgs(1) {
163 my ( $self, $c, $page_name ) = @_;
164 # load the page named $page_name and put the object
165 # into the stash
166 }
167 sub rev : PathPart('rev') Chained('wiki') CaptureArgs(1) {
169 my ( $self, $c, $revision_id ) = @_;
170 # use the page object in the stash to get at its
171 # revision with number $revision_id
172 }
173 sub view : PathPart Chained('rev') Args(0) {
175 my ( $self, $c ) = @_;
176 # display the revision in our stash. Another option
177 # would be to forward a compatible object to the action
178 # that displays the default wiki pages, unless we want
179 # a different interface here, for example restore
180 # functionality.
181 }
182 It would now be possible to add other endpoints, for example "restore"
184 to restore this specific revision as the current state.
185 You don't have to put all the chained actions in one controller. The
187 specification of the parent through ":Chained" also takes an absolute
188 action path as its argument. Just specify it with a leading "/".
189 If you want, for example, to have actions for the public paths
191 "/foo/12/edit" and "/foo/12", just specify two actions with
192 :PathPart('foo') and :Chained('/'). The handler for the former path
193 needs a :CaptureArgs(1) attribute and a endpoint with :PathPart('edit')
194 and :Chained('foo'). For the latter path give the action just a
195 :Args(1) to mark it as endpoint. This sums up to this debugging output:
196 ...
198 [debug] Loaded Path Part actions:
199 .-----------------------+------------------------------.
200 | Path Spec | Private |
201 +-----------------------+------------------------------+
202 | /foo/* | /controller/foo_view |
203 | /foo/*/edit | /controller/foo_load (1) |
204 | | => /controller/edit |
205 '-----------------------+------------------------------'
206 ...
207 Here's a more detailed specification of the attributes belonging to
209 ":Chained":
210 Attributes
212 PathPart
213 Sets the name of this part of the chain. If it is specified
214 without arguments, it takes the name of the action as default.
215 So basically "sub foo :PathPart" and "sub foo :PathPart('foo')"
216 are identical. This can also contain slashes to bind to a
217 deeper level. An action with "sub bar :PathPart('foo/bar')
218 :Chained('/')" would bind to "/foo/bar/...". If you don't
219 specify ":PathPart" it has the same effect as using
220 ":PathPart", it would default to the action name.
221 PathPrefix
223 Sets PathPart to the path_prefix of the current controller.
224 Chained Has to be specified for every child in the chain. Possible
226 values are absolute and relative private action paths or a
227 single slash "/" to tell Catalyst that this is the root of a
228 chain. The attribute ":Chained" without arguments also defaults
229 to the "/" behavior. Relative action paths may use "../" to
230 refer to actions in parent controllers.
231 Because you can specify an absolute path to the parent action,
233 it doesn't matter to Catalyst where that parent is located. So,
234 if your design requests it, you can redispatch a chain through
235 any controller or namespace you want.
236 Another interesting possibility gives :Chained('.'), which
238 chains itself to an action with the path of the current
239 controller's namespace. For example:
240 # in MyApp::Controller::Foo
242 sub bar : Chained CaptureArgs(1) { ... }
243 # in MyApp::Controller::Foo::Bar
245 sub baz : Chained('.') Args(1) { ... }
246 This builds up a chain like "/bar/*/baz/*". The specification
248 of "." as the argument to Chained here chains the "baz" action
249 to an action with the path of the current controller namespace,
250 namely "/foo/bar". That action chains directly to "/", so the
251 "/bar/*/baz/*" chain comes out as the end product.
252 ChainedParent
254 Chains an action to another action with the same name in the
255 parent controller. For Example:
256 # in MyApp::Controller::Foo
258 sub bar : Chained CaptureArgs(1) { ... }
259 # in MyApp::Controller::Foo::Bar
261 sub bar : ChainedParent Args(1) { ... }
262 This builds a chain like "/bar/*/bar/*".
264 CaptureArgs
266 Must be specified for every part of the chain that is not an
267 endpoint. With this attribute Catalyst knows how many of the
268 following parts of the path (separated by "/") this action
269 wants to capture as its arguments. If it doesn't expect any,
270 just specify :CaptureArgs(0). The captures get passed to the
271 action's @_ right after the context, but you can also find them
272 as array references in "$c->request->captures->[$level]". The
273 $level is the level of the action in the chain that captured
274 the parts of the path.
275 An action that is part of a chain (that is, one that has a
277 ":Chained" attribute) but has no ":CaptureArgs" attribute is
278 treated by Catalyst as a chain end.
279 Allowed values for CaptureArgs is a single integer
281 (CaptureArgs(2), meaning two allowed) or you can declare a
282 Moose, MooseX::Types or Type::Tiny named constraint such as
283 CaptureArgs(Int,Str) would require two args with the first
284 being a Integer and the second a string. You may declare your
285 own custom type constraints and import them into the controller
286 namespace:
287 package MyApp::Controller::Root;
289 use Moose;
291 use MooseX::MethodAttributes;
292 use MyApp::Types qw/Int/;
293 extends 'Catalyst::Controller';
295 sub chain_base :Chained(/) CaptureArgs(1) { }
297 sub any_priority_chain :Chained(chain_base) PathPart('') Args(1) { }
299 sub int_priority_chain :Chained(chain_base) PathPart('') Args(Int) { }
301 If you use a reference type constraint in CaptureArgs, it must
303 be a type like Tuple in Types::Standard that allows us to
304 determine the number of args to match. Otherwise this will
305 raise an error during startup.
306 See Catalyst::RouteMatching for more.
308 Args By default, endpoints receive the rest of the arguments in the
310 path. You can tell Catalyst through ":Args" explicitly how many
311 arguments your endpoint expects, just like you can with
312 ":CaptureArgs". Note that this also affects whether this chain
313 is invoked on a request. A chain with an endpoint specifying
314 one argument will only match if exactly one argument exists in
315 the path.
316 You can specify an exact number of arguments like :Args(3),
318 including 0. If you just say ":Args" without any arguments, it
319 is the same as leaving it out altogether: The chain is matched
320 regardless of the number of path parts after the endpoint.
321 Just as with ":CaptureArgs", the arguments get passed to the
323 action in @_ after the context object. They can also be reached
324 through "$c->request->arguments".
325 You should see 'Args' in Catalyst::Controller for more details
327 on using type constraints in your Args declarations.
328 Auto actions, dispatching and forwarding
330 Note that the list of "auto" actions called depends on the private path
331 of the endpoint of the chain, not on the chained actions way. The
332 "auto" actions will be run before the chain dispatching begins. In
333 every other aspect, "auto" actions behave as documented.
334 The "forward"ing to other actions does just what you would expect. i.e.
336 only the target action is run. The actions that that action is chained
337 to are not run. If you "detach" out of a chain, the rest of the chain
338 will not get called after the "detach".
339 match_captures
341 A method which can optionally be implemented by actions to stop chain
342 matching.
343 See Catalyst::Action for further details.
345
347 Catalyst Contributors, see Catalyst.pm
348
350 This library is free software. You can redistribute it and/or modify it
351 under the same terms as Perl itself.
352perl v5.38.0 2023-07-24Catalyst::DispatchType::Chained(3)