1Catalyst::DispatchType:U:sCehraiCnoendt(r3i)buted Perl DCoactuamleynstta:t:iDoinspatchType::Chained(3)
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NAME

6       Catalyst::DispatchType::Chained - Path Part DispatchType
7

SYNOPSIS

9       Path part matching, allowing several actions to sequentially take care
10       of processing a request:
11
12         #   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
18         #   child action endpoint - takes one argument
19         sub bar : Chained('foo_setup') Args(1) {
20             my ( $self, $c, $bar_arg ) = @_;
21             ...
22         }
23

DESCRIPTION

25       Dispatch type managing default behaviour.  For more information on
26       dispatch types, see:
27
28       •   Catalyst::Manual::Intro for how they affect application authors
29
30       •   Catalyst::DispatchType for implementation information.
31

METHODS

33   $self->list($c)
34       Debug output for Path Part dispatch points
35
36   $self->match( $c, $path )
37       Calls "recurse_match" to see if a chain matches the $path.
38
39   $self->recurse_match( $c, $parent, \@path_parts )
40       Recursive search for a matching chain.
41
42   $self->register( $c, $action )
43       Calls register_path for every Path attribute for the given $action.
44
45   $self->uri_for_action($action, $captures)
46       Get the URI part for the action, using $captures to fill the capturing
47       parts.
48
49   $c->expand_action($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

USAGE

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
65         package MyApp::Controller::Greeting;
66         use base qw/ Catalyst::Controller /;
67
68         #   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
75         #   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
81             $c->response->body( join "<br/>\n" =>
82                 $c->stash->{ message }, $c->stash->{ arg_sum } );
83         }
84
85       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
89         ...
90         [debug] Loaded Path Part actions:
91         .-----------------------+------------------------------.
92         | Path Spec             | Private                      |
93         +-----------------------+------------------------------+
94         | /hello/*/world/*      | /greeting/hello (1)          |
95         |                       | => /greeting/world           |
96         '-----------------------+------------------------------'
97         ...
98
99       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
103       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')"
110       we could also just have said ":PathPart", as it defaults to the name of
111       the action.
112
113       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
123       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
130       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
137         Hello World!
138         35
139
140       And our test server would have given us this debugging output for the
141       request:
142
143         ...
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
156       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
162         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
168         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
174         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
183       It would now be possible to add other endpoints, for example "restore"
184       to restore this specific revision as the current state.
185
186       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
190       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
194       ":PathPart('edit')" and ":Chained('foo')". For the latter path give the
195       action just a :Args(1) to mark it as endpoint. This sums up to this
196       debugging output:
197
198         ...
199         [debug] Loaded Path Part actions:
200         .-----------------------+------------------------------.
201         | Path Spec             | Private                      |
202         +-----------------------+------------------------------+
203         | /foo/*                | /controller/foo_view         |
204         | /foo/*/edit           | /controller/foo_load (1)     |
205         |                       | => /controller/edit          |
206         '-----------------------+------------------------------'
207         ...
208
209       Here's a more detailed specification of the attributes belonging to
210       ":Chained":
211
212   Attributes
213       PathPart
214               Sets the name of this part of the chain. If it is specified
215               without arguments, it takes the name of the action as default.
216               So basically "sub foo :PathPart" and "sub foo :PathPart('foo')"
217               are identical.  This can also contain slashes to bind to a
218               deeper level. An action with "sub bar :PathPart('foo/bar')
219               :Chained('/')" would bind to "/foo/bar/...". If you don't
220               specify ":PathPart" it has the same effect as using
221               ":PathPart", it would default to the action name.
222
223       PathPrefix
224               Sets PathPart to the path_prefix of the current controller.
225
226       Chained Has to be specified for every child in the chain. Possible
227               values are absolute and relative private action paths or a
228               single slash "/" to tell Catalyst that this is the root of a
229               chain. The attribute ":Chained" without arguments also defaults
230               to the "/" behavior.  Relative action paths may use "../" to
231               refer to actions in parent controllers.
232
233               Because you can specify an absolute path to the parent action,
234               it doesn't matter to Catalyst where that parent is located. So,
235               if your design requests it, you can redispatch a chain through
236               any controller or namespace you want.
237
238               Another interesting possibility gives ":Chained('.')", which
239               chains itself to an action with the path of the current
240               controller's namespace.  For example:
241
242                 #   in MyApp::Controller::Foo
243                 sub bar : Chained CaptureArgs(1) { ... }
244
245                 #   in MyApp::Controller::Foo::Bar
246                 sub baz : Chained('.') Args(1) { ... }
247
248               This builds up a chain like "/bar/*/baz/*". The specification
249               of "."  as the argument to Chained here chains the "baz" action
250               to an action with the path of the current controller namespace,
251               namely "/foo/bar". That action chains directly to "/", so the
252               "/bar/*/baz/*" chain comes out as the end product.
253
254       ChainedParent
255               Chains an action to another action with the same name in the
256               parent controller. For Example:
257
258                 # in MyApp::Controller::Foo
259                 sub bar : Chained CaptureArgs(1) { ... }
260
261                 # in MyApp::Controller::Foo::Bar
262                 sub bar : ChainedParent Args(1) { ... }
263
264               This builds a chain like "/bar/*/bar/*".
265
266       CaptureArgs
267               Must be specified for every part of the chain that is not an
268               endpoint. With this attribute Catalyst knows how many of the
269               following parts of the path (separated by "/") this action
270               wants to capture as its arguments. If it doesn't expect any,
271               just specify :CaptureArgs(0).  The captures get passed to the
272               action's @_ right after the context, but you can also find them
273               as array references in "$c->request->captures->[$level]". The
274               $level is the level of the action in the chain that captured
275               the parts of the path.
276
277               An action that is part of a chain (that is, one that has a
278               ":Chained" attribute) but has no ":CaptureArgs" attribute is
279               treated by Catalyst as a chain end.
280
281               Allowed values for CaptureArgs is a single integer
282               (CaptureArgs(2), meaning two allowed) or you can declare a
283               Moose, MooseX::Types or Type::Tiny named constraint such as
284               CaptureArgs(Int,Str) would require two args with the first
285               being a Integer and the second a string.  You may declare your
286               own custom type constraints and import them into the controller
287               namespace:
288
289                   package MyApp::Controller::Root;
290
291                   use Moose;
292                   use MooseX::MethodAttributes;
293                   use MyApp::Types qw/Int/;
294
295                   extends 'Catalyst::Controller';
296
297                   sub chain_base :Chained(/) CaptureArgs(1) { }
298
299                     sub any_priority_chain :Chained(chain_base) PathPart('') Args(1) { }
300
301                     sub int_priority_chain :Chained(chain_base) PathPart('') Args(Int) { }
302
303               If you use a reference type constraint in CaptureArgs, it must
304               be a type like Tuple in Types::Standard that allows us to
305               determine the number of args to match.  Otherwise this will
306               raise an error during startup.
307
308               See Catalyst::RouteMatching for more.
309
310       Args    By default, endpoints receive the rest of the arguments in the
311               path. You can tell Catalyst through ":Args" explicitly how many
312               arguments your endpoint expects, just like you can with
313               ":CaptureArgs". Note that this also affects whether this chain
314               is invoked on a request. A chain with an endpoint specifying
315               one argument will only match if exactly one argument exists in
316               the path.
317
318               You can specify an exact number of arguments like :Args(3),
319               including 0. If you just say ":Args" without any arguments, it
320               is the same as leaving it out altogether: The chain is matched
321               regardless of the number of path parts after the endpoint.
322
323               Just as with ":CaptureArgs", the arguments get passed to the
324               action in @_ after the context object. They can also be reached
325               through "$c->request->arguments".
326
327               You should see 'Args' in Catalyst::Controller for more details
328               on using type constraints in your Args declarations.
329
330   Auto actions, dispatching and forwarding
331       Note that the list of "auto" actions called depends on the private path
332       of the endpoint of the chain, not on the chained actions way. The
333       "auto" actions will be run before the chain dispatching begins. In
334       every other aspect, "auto" actions behave as documented.
335
336       The "forward"ing to other actions does just what you would expect. i.e.
337       only the target action is run. The actions that that action is chained
338       to are not run.  If you "detach" out of a chain, the rest of the chain
339       will not get called after the "detach".
340
341   match_captures
342       A method which can optionally be implemented by actions to stop chain
343       matching.
344
345       See Catalyst::Action for further details.
346

AUTHORS

348       Catalyst Contributors, see Catalyst.pm
349
351       This library is free software. You can redistribute it and/or modify it
352       under the same terms as Perl itself.
353
354
355
356perl v5.32.1                      2021-01-26Catalyst::DispatchType::Chained(3)
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