/ 
Data-Enum-v0.2.4
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/ Data::Enum

NAME

Data::Enum - immutable enumeration classes

VERSION

version v0.2.4

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.

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.

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) 2021-2022 by Robert Rothenberg.

This is free software, licensed under:

The Artistic License 2.0 (GPL Compatible)