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.IX Title "Plack::Middleware::Conditional 3pm"
.TH Plack::Middleware::Conditional 3pm 2024-01-20 "perl v5.38.2" "User Contributed Perl Documentation"
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.nh
.SH NAME
Plack::Middleware::Conditional \- Conditional wrapper for Plack middleware
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\&  use Plack::Builder;
\&
\&  builder {
\&      enable_if { $_[0]\->{REMOTE_ADDR} eq \*(Aq127.0.0.1\*(Aq } \*(AqStackTrace\*(Aq, force => 1;
\&      $app;
\&  };
\&
\&  # or using the OO interface:
\&  $app = Plack::Middleware::Conditional\->wrap(
\&      $app,
\&      condition  => sub { $_[0]\->{REMOTE_ADDR} eq \*(Aq127.0.0.1\*(Aq },
\&      builder => sub { Plack::Middleware::StackTrace\->wrap($_[0], force => 1) },
\&  );
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Plack::Middleware::Conditional is a piece of meta-middleware, to run a
specific middleware component under runtime conditions. The goal of
this middleware is to avoid baking runtime configuration options in
individual middleware components, and rather share them as another
middleware component.
.SH EXAMPLES
.IX Header "EXAMPLES"
Note that some of the middleware component names are just made up for
the explanation and might not exist.
.PP
.Vb 2
\&  # Minify JavaScript if the browser is Firefox
\&  enable_if { $_[0]\->{HTTP_USER_AGENT} =~ /Firefox/ } \*(AqJavaScriptMinifier\*(Aq;
\&
\&  # Enable Stacktrace when being accessed from the local network
\&  enable_if { $_[0]\->{REMOTE_ADDR} =~ /^10\e.0\e.1\e.*/ } \*(AqStackTrace\*(Aq;
\&
\&  # Work with other conditional setter middleware:
\&  # Transcode Jpeg on the fly for mobile clients
\&  builder {
\&      enable \*(AqMobileDetector\*(Aq;
\&      enable_if { $_[0]\->{\*(Aqplack.mobile_detected\*(Aq} }
\&        \*(AqTranscodeJpeg\*(Aq, max_size => 30_000;
\&      $app;
\&  };
.Ve
.PP
Note that in the last example \fIMobileDetector\fR should come first
because the conditional check runs in \fIpre-run\fR conditions, which is
from outer to inner: that is, from the top to the bottom in the
Builder DSL code.
.SH AUTHOR
.IX Header "AUTHOR"
Tatsuhiko Miyagawa
.PP
Steve Cook
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Plack::Builder