NAME

Data::Enum - immutable enumeration classes

VERSION

version v0.2.7

SYNOPSIS

  use Data::Enum;

  my $color = Data::Enum->new( qw[ red yellow blue green ] );

  my $red = $color->new("red");

  $red->is_red;    # "1"
  $red->is_yellow; # "" (false)
  $red->is_blue;   # "" (false)
  $red->is_green;  # "" (false)

  say $red;        # outputs "red"

  $red eq $color->new("red"); # true

  $red eq "red"; # true

DESCRIPTION

This module will create enumerated constant classes with the following properties:

• Any two classes with the same elements are equivalent.

  The following two classes are the same:

    my $one = Data::Enum->new( qw[ foo bar baz ] );
    my $two = Data::Enum->new( qw[ foo bar baz ] );

• All class instances are singletons.

    my $one = Data::Enum->new( qw[ foo bar baz ] );
  
    my $a = $one->new("foo")
    my $b = $one->new("foo");
  
    refaddr($a) == refaddr($b); # they are the same thing

• Methods for checking values are fast.

    $a->is_foo; # constant time
  
    $a eq $b;   # compares refaddr

• Values are immutable (read-only).

This is done by creating a unique internal class name based on the possible values. Each value is actually a subclass of that class, with the appropriate is_ method returning a constant.

METHODS

new

  my $class = Data::Enum->new( @values );

This creates a new anonymous class. Values can be instantiated with a constructor:

  my $instance = $class->new( $value );

Calling the constructor with an invalid value will throw an exception.

Each instance will have an is_ method for each value.

Each instance stringifies to its value.

values

  my @values = $class->values;

Returns a list of valid values, stringified and sorted with duplicates removed.

This was added in v0.2.0.

predicates

  my @predicates = $class->predicates;

Returns a list of predicate methods for each value.

A hash of predicates to values is roughly

  use List::Util 1.56 'mesh';

  my %handlers = mesh [ $class->values ], [ $class->predicates ];

This was added in v0.2.1.

MATCH

This method adds support for match::simple.

CAVEATS

The overheard of creating a new class instance and resolving methods may actually take more time than comparing simple strings. When using this in production code, you may want to benchmark performance.

SUPPORT FOR OLDER PERL VERSIONS

This module requires Perl v5.10 or later.

Future releases may only support Perl versions released in the last ten years.

SEE ALSO

Class::Enum

Object::Enum

MooX::Enumeration

MooseX::Enumeration

Type::Tiny::Enum

SOURCE

The development version is on github at https://github.com/robrwo/perl-Data-Enum and may be cloned from git://github.com/robrwo/perl-Data-Enum.git

BUGS

Please report any bugs or feature requests on the bugtracker website https://github.com/robrwo/perl-Data-Enum/issues

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

AUTHOR

Robert Rothenberg <rrwo@cpan.org>

COPYRIGHT AND LICENSE

This software is Copyright (c) 2021-2023 by Robert Rothenberg.

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)

cpanm Data::Enum

perl -MCPAN -e shell
install Data::Enum