NAME

Marlin::XAttribute::LocalWriter - Marlin attribute extension for localizing attribute values.

SYNOPSIS

package Local::Person {
  use Marlin::Util -all;
  use Types::Common -types;
  use Marlin
    name => {
      required       => true,
      isa            => Str,
      ':LocalWriter' => 'temp_name',
    };
}

my $bob = Local::Person->new( name => 'Bob' );
say $bob->name;  # "Bob"

{
  my $guard = $bob->temp_name( 'Robert' );
  say $bob->name;  # Robert
}

say $bob->name;  # "Bob"

IMPORTING THIS MODULE

The standard way to import Marlin attribute extensions is to include them in the attribute definition hashrefs passed to use Marlin

package Local::Person {
  use Marlin::Util -all;
  use Types::Common -types;
  use Marlin
    name => {
      required       => true,
      isa            => Str,
      ':LocalWriter' => 'temp_name',
    };
}

It is possible to additionally load it with use Marlin::XAttribute::LocalWriter, which won't do anything, but might be useful to automatic dependency analysis.

package Local::Person {
  use Marlin::Util -all;
  use Marlin::XAttribute::LocalWriter;
  use Types::Common -types;
  use Marlin
    name => {
      required       => true,
      isa            => Str,
      ':LocalWriter' => 'temp_name',
    };
}

DESCRIPTION

The following are spiritually similar:

{
  my $guard = $bob->temp_name( "Robert" );
  ...;
}

{
  local $bob->{name} = "Robert";
  ...;
}

However, the local writer method will honour type constraints, triggers, etc.

Calling $bob->temp_name() with no parameters is equivalent to doing delete local.

Note that the $guard which is returned by the method is where a lot of the magic happens. When it goes out of scope, it restores the original value.

If you set ':LocalWriter' => 1, this is a shortcut for ':LocalWriter' => "_local$attrname" if your attribute's name starts with an underscore, and ':LocalWriter' => "local_$attrname" otherwise.

This extension makes no changes to your constructor.

BUGS

Please report any bugs to https://github.com/tobyink/p5-marlin-xattribute-localwriter/issues.

SEE ALSO

Marlin.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2025-2026 by Toby Inkster.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

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