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1 | =encoding UTF-8 |
2 | |
3 | =head1 Name |
4 | |
5 | Catalyst::RouteMatching - How Catalyst maps an incoming URL to actions in controllers. |
6 | |
7 | =head1 Description |
8 | |
9 | This is a WIP document intended to help people understand the logic that L<Catalyst> |
10 | uses to determine how to match in incoming request to an action (or action chain) |
11 | in a controller. |
12 | |
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13 | =head2 Request to Controller/Action Matching |
14 | |
15 | L<Catalyst> maps requests to action using a 'longest path wins' approach. That means |
16 | that if the request is '/foo/bar/baz' That means the action 'baz' matches: |
17 | |
18 | package MyApp::Controller::Foo; |
19 | |
20 | use Moose; |
21 | use MooseX::MethodAttributes |
22 | |
23 | extends 'Catalyst::Controller'; |
24 | |
25 | sub bar :Path('bar') Args(1) { ...} |
26 | sub baz :Path('bar/baz') Args(0) { ... } |
27 | |
28 | Path length matches take precidence over all other types of matches (included HTTP |
29 | Method, Scheme, etc.). The same holds true for Chained actions. Generally the |
30 | chain that matches the most PathParts wins. |
31 | |
32 | =head2 Args(N) versus Args |
33 | |
34 | 'Args' matches any number of args. Because this functions as a sort of catchall, we |
35 | treat 'Args' as the lowest precedence of any Args(N) when N is 0 to infinity. An |
36 | action with 'Args' always get the last chance to match. |
37 | |
38 | =head2 When two or more actions match a given Path |
39 | |
40 | Sometimes two or more actions match the same path and all have the same pathpart |
41 | length. For example: |
42 | |
43 | package MyApp::Controller::Root; |
44 | |
45 | use Moose; |
46 | use MooseX::MethodAttributes |
47 | |
48 | extends 'Catalyst::Controller'; |
49 | |
50 | sub root :Chained(/) CaptureArgs(0) { } |
51 | |
52 | sub one :Chained(root) PathPart('') Args(0) { } |
53 | sub two :Chained(root) PathPart('') Args(0) { } |
54 | sub three :Chained(root) PathPart('') Args(0) { } |
55 | |
56 | __PACKAGE__->meta->make_immutable; |
57 | |
58 | In this case the last defined action wins (for the example that is action 'three'). |
59 | |
60 | This is most common to happen when you are using action matching beyond paths, such as |
61 | when using method matching: |
62 | |
63 | package MyApp::Controller::Root; |
64 | |
65 | use Moose; |
66 | use MooseX::MethodAttributes |
67 | |
68 | extends 'Catalyst::Controller'; |
69 | |
70 | sub root :Chained(/) CaptureArgs(0) { } |
71 | |
72 | sub any :Chained(root) PathPart('') Args(0) { } |
73 | sub get :GET Chained(root) PathPart('') Args(0) { } |
74 | |
75 | __PACKAGE__->meta->make_immutable; |
76 | |
77 | In the above example GET /root could match both actions. In this case you should define |
78 | your 'catchall' actions higher in the controller. |
79 | |
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80 | =head2 Type Constraints in Args and Capture Args |
81 | |
82 | Beginning in Version 5.90090+ you may use L<Moose>, L<MooseX::Types> or L<Type::Tiny> |
83 | type constraints to futher declare allowed matching for Args or CaptureArgs. Here |
84 | is a simple example: |
85 | |
86 | package MyApp::Controller::User; |
87 | |
88 | use Moose; |
89 | use MooseX::MethodAttributes; |
90 | |
91 | extends 'Catalyst::Controller'; |
92 | |
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93 | sub find :Path('') Args('Int') { |
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94 | my ($self, $c, $int) = @_; |
95 | } |
96 | |
97 | __PACKAGE__->meta->make_immutable; |
98 | |
99 | In this case the incoming request "http://localhost:/user/100" would match the action |
100 | C<find> but "http://localhost:/user/not_a_number" would not. You may find declaring |
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101 | constraints in this manner aids with debugging, automatic generation of documentation |
102 | and reducing the amount of manual checking you might need to do in your actions. For |
103 | example if the argument in the given action was going to be used to lookup a row |
104 | in a database, if the matching field expected an integer, a string might cause a database |
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105 | exception, prompting you to add additional checking of the argument prior to using it. |
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106 | In general it is hoped this feature can lead to reduced validation boilerplate and more |
107 | easily understood and declarative actions. |
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108 | |
109 | More than one argument may be added by comma separating your type constraint names, for |
110 | example: |
111 | |
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112 | use Types::Standard qw/Int Str/; |
113 | |
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114 | sub find :Path('') Args(Int,Int,Str) { |
115 | my ($self, $c, $int1, $int2, $str) = @_; |
116 | } |
117 | |
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118 | Would require three arguments, an integer, integer and a string. Note in this example we |
119 | constrained the args using imported types via L<Types::Standard>. Although you may use |
120 | stringy Moose types, we recommend imported types since this is less ambiguous to your readers. |
121 | If you want to use Moose stringy types. you must quote them (either "Int" or 'Int' is fine). |
122 | |
123 | Conversely, you should not quote types that are imported! |
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124 | |
125 | =head3 Using type constraints in a controller |
126 | |
127 | By default L<Catalyst> allows all the standard, built-in, named type constraints that come |
128 | bundled with L<Moose>. However it is trivial to create your own Type constraint libraries |
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129 | and export them to a controller that wishes to use them. We recommend using L<Type::Tiny> or |
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130 | L<MooseX::Types> for this. Here is an example using some extended type constraints via |
131 | the L<Types::Standard> library that is packaged with L<Type::Tiny>: |
132 | |
133 | package MyApp::Controller::User; |
134 | |
135 | use Moose; |
136 | use MooseX::MethodAttributes; |
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137 | use Types::Standard qw/StrMatch Int/; |
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138 | |
139 | extends 'Catalyst::Controller'; |
140 | |
141 | sub looks_like_a_date :Path('') Args(StrMatch[qr{\d\d-\d\d-\d\d}]) { |
142 | my ($self, $c, $int) = @_; |
143 | } |
144 | |
145 | __PACKAGE__->meta->make_immutable; |
146 | |
147 | This would match URLs like "http://localhost/user/11-11-2015" for example. If you've been |
148 | missing the old RegExp matching, this can emulate a good chunk of that ability, and more. |
149 | |
150 | A tutorial on how to make custom type libraries is outside the scope of this document. I'd |
151 | recommend looking at the copious documentation in L<Type::Tiny> or in L<MooseX::Types> if |
152 | you prefer that system. The author recommends L<Type::Tiny> if you are unsure which to use. |
153 | |
154 | =head3 Match order when more than one Action matches a path. |
155 | |
156 | As previously described, L<Catalyst> will match 'the longest path', which generally means |
157 | that named path / path_parts will take precidence over Args or CaptureArgs. However, what |
158 | will happen if two actions match the same path with equal args? For example: |
159 | |
160 | sub an_int :Path(user) Args(Int) { |
161 | } |
162 | |
163 | sub an_any :Path(user) Args(1) { |
164 | } |
165 | |
166 | In this case L<Catalyst> will check actions starting from the LAST one defined. Generally |
167 | this means you should put your most specific action rules LAST and your 'catch-alls' first. |
168 | In the above example, since Args(1) will match any argument, you will find that that 'an_int' |
169 | action NEVER gets hit. You would need to reverse the order: |
170 | |
171 | sub an_any :Path(user) Args(1) { |
172 | } |
173 | |
174 | sub an_int :Path(user) Args(Int) { |
175 | } |
176 | |
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177 | Now requests that match this path would first hit the 'an_int' action and will check to see if |
178 | the argument is an integer. If it is, then the action will execute, otherwise it will pass and |
179 | the dispatcher will check the next matching action (in this case we fall thru to the 'an_any' |
180 | action). |
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181 | |
182 | =head3 Type Constraints and Chained Actions |
183 | |
184 | Using type constraints in Chained actions works the same as it does for Path and Local or Global |
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185 | actions. The only difference is that you may declare type constraints on CaptureArgs as |
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186 | well as Args. For Example: |
187 | |
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188 | use Types::Standard qw/Int Tuple/; |
189 | |
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190 | sub chain_base :Chained(/) CaptureArgs(1) { } |
191 | |
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192 | sub any_priority_chain :GET Chained(chain_base) PathPart('') Args(1) { } |
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193 | |
194 | sub int_priority_chain :Chained(chain_base) PathPart('') Args(Int) { } |
195 | |
196 | sub link_any :Chained(chain_base) PathPart('') CaptureArgs(1) { } |
197 | |
198 | sub any_priority_link_any :Chained(link_any) PathPart('') Args(1) { } |
199 | |
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200 | sub int_priority_link_any :Chained(link_any) PathPart('') Args(Int) { } |
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201 | |
202 | sub link_int :Chained(chain_base) PathPart('') CaptureArgs(Int) { } |
203 | |
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204 | sub any_priority_link :Chained(link_int) PathPart('') Args(1) { } |
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205 | |
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206 | sub int_priority_link :Chained(link_int) PathPart('') Args(Int) { } |
207 | |
208 | sub link_int_int :Chained(chain_base) PathPart('') CaptureArgs(Int,Int) { } |
209 | |
210 | sub any_priority_link2 :Chained(link_int_int) PathPart('') Args(1) { } |
211 | |
212 | sub int_priority_link2 :Chained(link_int_int) PathPart('') Args(Int) { } |
213 | |
214 | sub link_tuple :Chained(chain_base) PathPart('') CaptureArgs(Tuple[Int,Int,Int]) { } |
215 | |
216 | sub any_priority_link3 :Chained(link_tuple) PathPart('') Args(1) { } |
217 | |
218 | sub int_priority_link3 :Chained(link_tuple) PathPart('') Args(Int) { } |
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219 | |
220 | These chained actions migth create match tables like the following: |
221 | |
222 | [debug] Loaded Chained actions: |
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223 | .-------------------------------------+--------------------------------------. |
224 | | Path Spec | Private | |
225 | +-------------------------------------+--------------------------------------+ |
226 | | /chain_base/*/* | /chain_base (1) | |
227 | | | => GET /any_priority_chain (1) | |
228 | | /chain_base/*/*/* | /chain_base (1) | |
229 | | | -> /link_int (Int) | |
230 | | | => /any_priority_link (1) | |
231 | | /chain_base/*/*/*/* | /chain_base (1) | |
232 | | | -> /link_int_int (Int,Int) | |
233 | | | => /any_priority_link2 (1) | |
234 | | /chain_base/*/*/*/*/* | /chain_base (1) | |
235 | | | -> /link_tuple (Tuple[Int,Int,Int]) | |
236 | | | => /any_priority_link3 (1) | |
237 | | /chain_base/*/*/* | /chain_base (1) | |
238 | | | -> /link_any (1) | |
239 | | | => /any_priority_link_any (1) | |
240 | | /chain_base/*/*/*/*/*/* | /chain_base (1) | |
241 | | | -> /link_tuple (Tuple[Int,Int,Int]) | |
242 | | | -> /link2_int (UserId) | |
243 | | | => GET /finally (Int) | |
244 | | /chain_base/*/*/*/*/*/... | /chain_base (1) | |
245 | | | -> /link_tuple (Tuple[Int,Int,Int]) | |
246 | | | -> /link2_int (UserId) | |
247 | | | => GET /finally2 (...) | |
248 | | /chain_base/*/* | /chain_base (1) | |
249 | | | => /int_priority_chain (Int) | |
250 | | /chain_base/*/*/* | /chain_base (1) | |
251 | | | -> /link_int (Int) | |
252 | | | => /int_priority_link (Int) | |
253 | | /chain_base/*/*/*/* | /chain_base (1) | |
254 | | | -> /link_int_int (Int,Int) | |
255 | | | => /int_priority_link2 (Int) | |
256 | | /chain_base/*/*/*/*/* | /chain_base (1) | |
257 | | | -> /link_tuple (Tuple[Int,Int,Int]) | |
258 | | | => /int_priority_link3 (Int) | |
259 | | /chain_base/*/*/* | /chain_base (1) | |
260 | | | -> /link_any (1) | |
261 | | | => /int_priority_link_any (Int) | |
262 | '-------------------------------------+--------------------------------------' |
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263 | |
264 | As you can see the same general path could be matched by various action chains. In this case |
265 | the rule described in the previous section should be followed, which is that L<Catalyst> |
266 | will start with the last defined action and work upward. For example the action C<int_priority_chain> |
267 | would be checked before C<any_priority_chain>. The same applies for actions that are midway links |
268 | in a longer chain. In this case C<link_int> would be checked before C<link_any>. So as always we |
269 | recommend that you place you priority or most constrainted actions last and you least or catch-all |
270 | actions first. |
271 | |
272 | Although this reverse order checking may seen counter intuitive it does have the added benefit that |
273 | when inheriting controllers any new actions added would take check precedence over those in your |
274 | parent controller or consumed role. |
275 | |
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276 | Please note that your declared type constraint names will now appear in the debug console. |
277 | |
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278 | =head1 Author |
279 | |
280 | John Napiorkowski L<jjnapiork@cpan.org|email:jjnapiork@cpan.org> |
281 | |
282 | =cut |
283 | |