| Catalyst::DispatchType::Chained - Path Part DispatchType |
list($c)
Catalyst::DispatchType::Chained - Path Part DispatchType
# root action - captures one argument after it
sub foo_setup : Chained('/') PathPart('foo') CaptureArgs(1) {
my ( $self, $c, $foo_arg ) = @_;
...
}
# child action endpoint - takes one argument
sub bar : Chained('foo_setup') Args(1) {
my ( $self, $c, $bar_arg ) = @_;
...
}
See USAGE.
list($c)Debug output for Path Part dispatch points
Calls recurse_match to see if a chain matches the $path.
Recursive search for a matching chain.
Calls register_path for every Path attribute for the given $action.
Get the URI part for the action, using $captures to fill
the capturing parts.
The Chained attribute allows you to chain public path parts together
by their private names. A chain part's path can be specified with
PathPart and can be declared to expect an arbitrary number of
arguments. The endpoint of the chain specifies how many arguments it
gets through the Args attribute. :Args(0) would be none at all,
:Args without an integer would be unlimited. The path parts that
aren't endpoints are using CaptureArgs to specify how many parameters
they expect to receive. As an example setup:
package MyApp::Controller::Greeting; use base qw/ Catalyst::Controller /;
# this is the beginning of our chain
sub hello : PathPart('hello') Chained('/') CaptureArgs(1) {
my ( $self, $c, $integer ) = @_;
$c->stash->{ message } = "Hello ";
$c->stash->{ arg_sum } = $integer;
}
# this is our endpoint, because it has no :CaptureArgs
sub world : PathPart('world') Chained('hello') Args(1) {
my ( $self, $c, $integer ) = @_;
$c->stash->{ message } .= "World!";
$c->stash->{ arg_sum } += $integer;
$c->response->body( join "<br/>\n" =>
$c->stash->{ message }, $c->stash->{ arg_sum } );
}
The debug output provides a separate table for chained actions, showing the whole chain as it would match and the actions it contains. Here's an example of the startup output with our actions above:
... [debug] Loaded Path Part actions: .-----------------------+------------------------------. | Path Spec | Private | +-----------------------+------------------------------+ | /hello/*/world/* | /greeting/hello (1) | | | => /greeting/world | '-----------------------+------------------------------' ...
As you can see, Catalyst only deals with chains as whole paths and
builds one for each endpoint, which are the actions with :Chained but
without :CaptureArgs.
Let's assume this application gets a request at the path
/hello/23/world/12. What happens then? First, Catalyst will dispatch
to the hello action and pass the value 23 as an argument to it
after the context. It does so because we have previously used
:CaptureArgs(1) to declare that it has one path part after itself as
its argument. We told Catalyst that this is the beginning of the chain
by specifying :Chained('/'). Also note that instead of saying
:PathPart('hello') we could also just have said :PathPart, as it
defaults to the name of the action.
After hello has run, Catalyst goes on to dispatch to the world
action. This is the last action to be called: Catalyst knows this is an
endpoint because we did not specify a :CaptureArgs
attribute. Nevertheless we specify that this action expects an argument,
but at this point we're using :Args(1) to do that. We could also have
said :Args or left it out altogether, which would mean this action
would get all arguments that are there. This action's :Chained
attribute says hello and tells Catalyst that the hello action in
the current controller is its parent.
With this we have built a chain consisting of two public path parts.
hello captures one part of the path as its argument, and also
specifies the path root as its parent. So this part is
/hello/$arg. The next part is the endpoint world, expecting one
argument. It sums up to the path part world/$arg. This leads to a
complete chain of /hello/$arg/world/$arg which is matched against the
requested paths.
This example application would, if run and called by e.g.
/hello/23/world/12, set the stash value message to ``Hello'' and the
value arg_sum to ``23''. The world action would then append ``World!''
to message and add 12 to the stash's arg_sum value. For the
sake of simplicity no view is shown. Instead we just put the values of
the stash into our body. So the output would look like:
Hello World! 35
And our test server would have given us this debugging output for the request:
... [debug] "GET" request for "hello/23/world/12" from "127.0.0.1" [debug] Path is "/greeting/world" [debug] Arguments are "12" [info] Request took 0.164113s (6.093/s) .------------------------------------------+-----------. | Action | Time | +------------------------------------------+-----------+ | /greeting/hello | 0.000029s | | /greeting/world | 0.000024s | '------------------------------------------+-----------' ...
What would be common uses of this dispatch technique? It gives the
possibility to split up logic that contains steps that each depend on
each other. An example would be, for example, a wiki path like
/wiki/FooBarPage/rev/23/view. This chain can be easily built with
these actions:
sub wiki : PathPart('wiki') Chained('/') CaptureArgs(1) {
my ( $self, $c, $page_name ) = @_;
# load the page named $page_name and put the object
# into the stash
}
sub rev : PathPart('rev') Chained('wiki') CaptureArgs(1) {
my ( $self, $c, $revision_id ) = @_;
# use the page object in the stash to get at its
# revision with number $revision_id
}
sub view : PathPart Chained('rev') Args(0) {
my ( $self, $c ) = @_;
# display the revision in our stash. Another option
# would be to forward a compatible object to the action
# that displays the default wiki pages, unless we want
# a different interface here, for example restore
# functionality.
}
It would now be possible to add other endpoints, for example restore
to restore this specific revision as the current state.
You don't have to put all the chained actions in one controller. The
specification of the parent through :Chained also takes an absolute
action path as its argument. Just specify it with a leading /.
If you want, for example, to have actions for the public paths
/foo/12/edit and /foo/12, just specify two actions with
:PathPart('foo') and :Chained('/'). The handler for the former
path needs a :CaptureArgs(1) attribute and a endpoint with
:PathPart('edit') and :Chained('foo'). For the latter path give
the action just a :Args(1) to mark it as endpoint. This sums up to
this debugging output:
... [debug] Loaded Path Part actions: .-----------------------+------------------------------. | Path Spec | Private | +-----------------------+------------------------------+ | /foo/* | /controller/foo_view | | /foo/*/edit | /controller/foo_load (1) | | | => /controller/edit | '-----------------------+------------------------------' ...
Here's a more detailed specification of the attributes belonging to
:Chained:
sub foo :PathPart and sub foo :PathPart('foo') are identical.
This can also contain slashes to bind to a deeper level. An action
with sub bar :PathPart('foo/bar') :Chained('/') would bind to
/foo/bar/.... If you don't specify :PathPart it has the same
effect as using :PathPart, it would default to the action name.
/ to tell Catalyst that
this is the root of a chain. The attribute :Chained without arguments
also defaults to the / behavior.
Because you can specify an absolute path to the parent action, it doesn't matter to Catalyst where that parent is located. So, if your design requests it, you can redispatch a chain through any controller or namespace you want.
Another interesting possibility gives :Chained('.'), which chains
itself to an action with the path of the current controller's namespace.
For example:
# in MyApp::Controller::Foo
sub bar : Chained CaptureArgs(1) { ... }
# in MyApp::Controller::Foo::Bar
sub baz : Chained('.') Args(1) { ... }
This builds up a chain like /bar/*/baz/*. The specification of .
as the argument to Chained here chains the baz action to an action
with the path of the current controller namespace, namely
/foo/bar. That action chains directly to /, so the /bar/*/baz/*
chain comes out as the end product.
/) this action wants to capture as
its arguments. If it doesn't expect any, just specify
:CaptureArgs(0). The captures get passed to the action's @_ right
after the context, but you can also find them as array references in
$c->request->captures->[$level]. The $level is the
level of the action in the chain that captured the parts of the path.
An action that is part of a chain (that is, one that has a :Chained
attribute) but has no :CaptureArgs attribute is treated by Catalyst
as a chain end.
:Args explicitly how many arguments your
endpoint expects, just like you can with :CaptureArgs. Note that this
also affects whether this chain is invoked on a request. A chain with an
endpoint specifying one argument will only match if exactly one argument
exists in the path.
You can specify an exact number of arguments like :Args(3), including
0. If you just say :Args without any arguments, it is the same as
leaving it out altogether: The chain is matched regardless of the number
of path parts after the endpoint.
Just as with :CaptureArgs, the arguments get passed to the action in
@_ after the context object. They can also be reached through
$c->request->arguments.
Note that the list of auto actions called depends on the private path
of the endpoint of the chain, not on the chained actions way. The
auto actions will be run before the chain dispatching begins. In
every other aspect, auto actions behave as documented.
The forwarding to other actions does just what you would expect. But if
you detach out of a chain, the rest of the chain will not get called
after the detach.
Matt S Trout <mst@shadowcatsystems.co.uk>
This program is free software, you can redistribute it and/or modify it under the same terms as Perl itself.
| Catalyst::DispatchType::Chained - Path Part DispatchType |