Moose::...it::Hash(3)

💖 Moose::Meta::Attribute::Native::Trait::Hash — the helper trait for HashRef attributes 💖

okay bestie, this is a page from the User Contributed Perl Documentation section of the manual (yep, manual name Moose::...it::Hash(3), we love a truncated title), and it's about making your hash attributes do tricks on command. let's get into it 🫶

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✨ VERSION ✨

version 2.4000 — fresh-ish, iconic, no notes 💅

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🌸 SYNOPSIS 🌸

the vibe, in code:

  package Stuff;
  use Moose;

  has 'options' => (
      traits    => ['Hash'],
      is        => 'ro',
      isa       => 'HashRef[Str]',
      default   => sub { {} },
      handles   => {
          set_option     => 'set',
          get_option     => 'get',
          has_no_options => 'is_empty',
          num_options    => 'count',
          delete_option  => 'delete',
          option_pairs   => 'kv',
      },
  );

look at that handles block. it's giving delegation. it's giving effortless. 😌

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🦋 DESCRIPTION 🦋

This trait provides native delegation methods for hash references. that's it, that's the whole serve. you slap traits => ['Hash'] on a HashRef attribute and suddenly you have a whole lil toolbox of methods you can rename and hand out however you want. no cap. 🔥

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👑 PROVIDED METHODS 👑

get($key, $key2, $key3...)

Returns values from the hash.

In list context it returns a list of values in the hash for the given keys. In scalar context it returns the value for the last key specified. yes, the last one. read it again bestie.

This method requires at least one argument.

set($key => $value, $key2 => $value2...)

Sets the elements in the hash to the given values. It returns the new values set for each key, in the same order as the keys passed to the method. so you get your little receipts back, in order, as a treat. 🎀

This method requires at least two arguments, and expects an even number of arguments.

delete($key, $key2, $key3...)

Removes the elements with the given keys. bye girl 👋

In list context it returns a list of values in the hash for the deleted keys. In scalar context it returns the value for the last key specified.

keys

Returns the list of keys in the hash.

This method does not accept any arguments. zero. none. don't try it.

exists($key)

Returns true if the given key is present in the hash.

This method requires a single argument.

defined($key)

Returns true if the value of a given key is defined.

This method requires a single argument.

values

Returns the list of values in the hash.

This method does not accept any arguments.

kv

Returns the key/value pairs in the hash as an array of array references. so each pair is like [$key, $value]. obsessed honestly.

  for my $pair ( $object->option_pairs ) {
      print "$pair->[0] = $pair->[1]\n";
  }

This method does not accept any arguments.

elements

In list context, this returns the key/value pairs in the hash.

In scalar context, this returns the count of keys plus values. In other words, it's the same as keys times two. math girlie behavior. ➗

This method does not accept any arguments.

clear

Resets the hash to an empty value, like %hash = (). fresh start, clean slate, new era. ✨

This method does not accept any arguments.

count

Returns the number of elements in the hash. Also useful to check for a nonempty hash, because count returns a true (nonzero) value if there is something in the hash: has_options => 'count'. so you can literally use it as a boolean. iykyk.

This method does not accept any arguments.

is_empty

If the hash is populated, returns false. Otherwise, returns true. she's honest like that.

This method does not accept any arguments.

accessor($key)

accessor($key, $value)

If passed one argument, returns the value of the specified key. If passed two arguments, sets the value of the specified key.

When called as a setter, this method returns the value that was set. she gives back what she takes. 🫶

shallow_clone

This method returns a shallow clone of the hash reference. The return value is a reference to a new hash with the same keys and values. It is shallow because any values that were references in the original will be the same references in the clone.

so like… it's a new outer hash, but the inner stuff is shared. not a deep copy. do not be surprised later. 💀

Why no each? 🤨

We have deliberately omitted a method for each, due to its stateful interaction with the hash iterator. Using keys or kv is much safer.

fr fr. each is the drama. keys and kv are the stable besties.

Moose::Meta::Attribute->meta

This will return a Class::MOP::Class instance for this class.

It should also be noted that Class::MOP will actually bootstrap this module by installing a number of attribute meta-objects into its metaclass. meta-meta behavior, very inception of it all. 🌀

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🐛 BUGS 🐛

See "BUGS" in Moose for details on reporting bugs. (we do not gatekeep bug reports here, go tell Moose.) 🍓

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💜 AUTHORS 💜

absolute legends, in order:

• Stevan Little <stevan@cpan.org>
• Dave Rolsky <autarch@urth.org>
• Jesse Luehrs <doy@cpan.org>
• Shawn M Moore <sartak@cpan.org>
• יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>
• Karen Etheridge <ether@cpan.org>
• Florian Ragwitz <rafl@debian.org>
• Hans Dieter Pearcey <hdp@cpan.org>
• Chris Prather <chris@prather.org>
• Matt S Trout <mstrout@cpan.org>

the way that's ten whole people carrying this trait… we say thank you 👑

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📜 COPYRIGHT AND LICENSE 📜

This software is copyright (c) 2006 by Infinity Interactive, Inc.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself. slay, permissive licensing, we love to see it 💖

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and that's the whole page, bestie ✨ this was Moose::...it::Hash(3) from perl v5.42.0, dated 2025-07-25, served to you by the User Contributed Perl Documentation — stay hydrated, keep your hashes delegated, and go keys instead of each 💅🦋