Plack::Component(3pm)

1Plack::Component(3)   User Contributed Perl Documentation  Plack::Component(3)
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NAME

6       Plack::Component - Base class for PSGI endpoints
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SYNOPSIS

9         package Plack::App::Foo;
10         use parent qw( Plack::Component );
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12         sub call {
13             my($self, $env) = @_;
14             # Do something with $env
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16             my $res = ...; # create a response ...
17
18             # return the response
19             return $res;
20         }
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DESCRIPTION

23       Plack::Component is the base class shared between Plack::Middleware and
24       "Plack::App::*" modules. If you are writing middleware, you should
25       inherit from Plack::Middleware, but if you are writing a Plack::App::*
26       you should inherit from this directly.
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REQUIRED METHOD

29       call ($env)
30           You are expected to implement a "call" method in your component.
31           This is where all the work gets done. It receives the PSGI $env
32           hash-ref as an argument and is expected to return a proper PSGI
33           response value.
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METHODS

36       new (%opts | \%opts)
37           The constructor accepts either a hash or a hashref and uses that to
38           create the instance. It will call no other methods and simply
39           return the instance that is created.
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41       prepare_app
42           This method is called by "to_app" and is meant as a hook to be used
43           to prepare your component before it is packaged as a PSGI $app.
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45       to_app
46           This is the method used in several parts of the Plack
47           infrastructure to convert your component into a PSGI $app. You
48           should not ever need to override this method; it is recommended to
49           use "prepare_app" and "call" instead.
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51       response_cb
52           This is a wrapper for "response_cb" in Plack::Util. See "RESPONSE
53           CALLBACK" in Plack::Middleware for details.
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OBJECT LIFECYCLE

56       Objects for the derived classes (Plack::App::* or Plack::Middleware::*)
57       are created at the PSGI application compile phase using "new",
58       "prepare_app" and "to_app", and the created object persists during the
59       web server lifecycle, unless it is running on the non-persistent
60       environment like CGI. "call" is invoked against the same object
61       whenever a new request comes in.
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63       You can check if it is running in a persistent environment by checking
64       "psgi.run_once" key in the $env being true (non-persistent) or false
65       (persistent), but it is best for you to write your middleware safely
66       for a persistent environment. To accomplish that, you should avoid
67       saving per-request data like $env in your object.
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BACKWARDS COMPATIBILITY

70       The Plack::Middleware module used to inherit from
71       Class::Accessor::Fast, which has been removed in favor of the
72       Plack::Util::Accessor module. When developing new components it is
73       recommended to use Plack::Util::Accessor like so:
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75         use Plack::Util::Accessor qw( foo bar baz );
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77       However, in order to keep backwards compatibility this module provides
78       a "mk_accessors" method similar to Class::Accessor::Fast. New code
79       should not use this and use Plack::Util::Accessor instead.
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