#NAME

Plack::Middleware::Conditional - Conditional wrapper for Plack middleware

#SYNOPSIS

use Plack::Builder;

builder {
    enable_if { $_[0]->{REMOTE_ADDR} eq '127.0.0.1' } 'StackTrace', force => 1;
    $app;
};

# or using the OO interface:
$app = Plack::Middleware::Conditional->wrap(
    $app,
    condition  => sub { $_[0]->{REMOTE_ADDR} eq '127.0.0.1' },
    builder => sub { Plack::Middleware::StackTrace->wrap($_[0], force => 1) },
);

#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.

#EXAMPLES

Note that some of the middleware component names are just made up for the explanation and might not exist.

# Minify JavaScript if the browser is Firefox
enable_if { $_[0]->{HTTP_USER_AGENT} =~ /Firefox/ } 'JavaScriptMinifier';

# Enable Stacktrace when being accessed from the local network
enable_if { $_[0]->{REMOTE_ADDR} =~ /^10\.0\.1\.*/ } 'StackTrace';

# Work with other conditional setter middleware:
# Transcode Jpeg on the fly for mobile clients
builder {
    enable 'MobileDetector';
    enable_if { $_[0]->{'plack.mobile_detected'} }
      'TranscodeJpeg', max_size => 30_000;
    $app;
};

Note that in the last example MobileDetector should come first because the conditional check runs in pre-run conditions, which is from outer to inner: that is, from the top to the bottom in the Builder DSL code.

#AUTHOR

Tatsuhiko Miyagawa

Steve Cook

#SEE ALSO