POE::Filter::Map(3pm)

💅 POE::Filter::Map — the manual page, but make it cute ✨

okay bestie, so POE::Filter::Map is a Perl thing from the User Contributed Perl Documentation squad, and it's basically the glow-up your data gets on the way through a filter stack. transforming input and/or output? yeah. that's the whole vibe. 🦋

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✨ SYNOPSIS ✨

like, here's the whole thing in action, no notes, iconic behaviour:

#!perl

use POE qw(
  Wheel::FollowTail
  Filter::Line Filter::Map Filter::Stackable
);

POE::Session->create(
  inline_states => {
    _start => sub {
      my $parse_input_as_lines = POE::Filter::Line->new();

      my $redact_some_lines = POE::Filter::Map->new(
        Code => sub {
          my $input = shift;
          $input = "[REDACTED]" unless $input =~ /sudo\[\d+\]/i;
          return $input;
        },
      );

      my $filter_stack = POE::Filter::Stackable->new(
        Filters => [
          $parse_input_as_lines, # first on get, last on put
          $redact_some_lines, # first on put, last on get
        ]
      );

      $_[HEAP]{tailor} = POE::Wheel::FollowTail->new(
        Filename => "/var/log/system.log",
        InputEvent => "got_log_line",
        Filter => $filter_stack,
      );
    },
    got_log_line => sub {
      print "Log: $_[ARG0]\n";
    }
  }
);

POE::Kernel->run();
exit;

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🌸 DESCRIPTION 🌸

so POE::Filter::Map transforms data inside the filter stack. it can do input, output, or both — depends on how you construct it, bestie. it's literally named and modeled after Perl's built-in map() function, which, slay. 💖

and the way it's designed to be combined with other filters through POE::Filter::Stackable? obsessed. in that "SYNOPSIS" example up there, a filter stack gets created to parse logs as lines and redact every entry that doesn't pertain to a sudo process. so all the not-sudo stuff gets the [REDACTED] treatment. privacy queen behaviour. 👑

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🎀 PUBLIC FILTER METHODS 🎀

on top of the usual POE::Filter methods, POE::Filter::Map also supports these:

💫 new

new() constructs a new POE::Filter::Map object. it must either be called with a single Code parameter, or both a Put and a Get parameter. no half-measures, pick a lane.

the values for Code, Put and Get are code references that, when invoked, return transformed versions of their sole parameters. a Code function gets used for both input and output, while Get and Put functions let input and output be filtered in different ways. very versatile of them honestly.

# Decrypt rot13.
sub decrypt_rot13 {
  my $encrypted = shift;
  $encrypted =~ tr[a-zA-Z][n-za-mN-ZA-M];
  return $encrypted;
}

# Encrypt rot13.
sub encrypt_rot13 {
  my $plaintext = shift;
  $plaintext =~ tr[a-zA-Z][n-za-mN-ZA-M];
  return $plaintext;
}

# Decrypt rot13 on input, and encrypt it on output.
my $rot13_transcrypter = POE::Filter::Map->new(
  Get => \&decrypt_rot13,
  Put => \&encrypt_rot13,
);

ngl rot13 is symmetric, so that whole example can be simplified down to a single Code function. less code, same energy:

my $rot13_transcrypter = POE::Filter::Map->new(
  Code => sub {
    local $_ = shift;
    tr[a-zA-Z][n-za-mN-ZA-M];
    return $_;
  }
);

💫 modify

modify() changes a POE::Filter::Map object's behavior at run-time. it accepts the same parameters as new(), and it replaces the existing transforms with new ones. glow-up mid-operation, we love to see it. 🦋

# Switch to "reverse" encryption for testing.
$rot13_transcrypter->modify(
  Code => sub { return scalar reverse shift }
);

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👀 SEE ALSO 👀

• POE::Filter for more information about filters in general.
• POE::Filter::Stackable for more details on stacking filters.

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💀 BUGS 💀

None known.

like, no known bugs?? we stan a flawless filter. 😭✨

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🫶 AUTHORS & COPYRIGHTS 🫶

The Map filter was contributed by Dieter Pearcey. Documentation is provided by Rocco Caputo. absolute icons, ty for your service. 💜

Please see the POE manpage for more information about authors and contributors.

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okay that's the whole thing, bestie!! you're now fully fluent in POE::Filter::Map. go transform some data, you main character. 💅🌈

this page came from perl v5.34.0, dated 2022-03-25, and it's page POE::Filter::Map(3pm) of the User Contributed Perl Documentation — mwah, bye!! 🎀