A compact hash object with key alias and default value support
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Hash::Compact - A hash-based object implementation with key alias and default value support


package My::Memcached;

use strict; use warnings; use parent qw(Cache::Memcached::Fast);

use JSON; use Hash::Compact;

my $OPTIONS = { foo => { alias_for => 'f', }, bar => { alias_for => 'b', default => 'bar', }, };

sub get { my ($self, $key) = @_; my $value = $self->SUPER::get($key); Hash::Compact->new(decode_json $value, $OPTIONS); }

sub set { my ($self, $key, $value, $expire) = @_; my $hash = Hash::Compact->new($value, $OPTIONS); $self->SUPER::set($key, encode_json $hash->compact, $expire); }

package main;

use strict; use warnings; use Test::More;

my $key = 'key'; my $value = { foo => 'foo' }; my $memd = My::Memcached->new({servers => [qw(localhost:11211)]}); $memd->set($key, $value);

my $cached_value = $memd->get($key); is $cached_value->param('foo'), 'foo'; is $cached_value->param('bar'), 'bar'; is_deeply $cached_value->compact, +{ f => 'foo' };

$cached_value->param(bar => 'baz'); $memd->set($key, $cached_value->compact);

$cached_value = $memd->get($key); is $cached_value->param('foo'), 'foo'; is $cached_value->param('bar'), 'baz'; is_deeply $cached_value->compact, +{ f => 'foo', b => 'baz' };



When we store some structured value into a column of a relational database or some key/value storage, redundancy of long key names can be a problem for storage space.

This module is yet another hash-based object implementation which aims to be aware of both space efficiency and easiness to use for us.


new (I<\%hash> I<[, \%options]>)

my $hash = Hash::Compact->new({ foo => 'foo', }, { foo => { alias_for => 'f', }, bar => { alias_for => 'b', default => 'bar', }, }, );

Creates and returns a new Hash::Compact object. If \%options not passed, Hash::Compact object $hash will be just a plain hash-based object.

\%options is a hash-ref which key/value pairs are associated with ones of \%hash. It may contain the fields below:

  • * alias_for

Alias to an actual key. If it's passed, \%hash will be compacted into another hash which has aliased key. The original key of \%hash will be just an alias to an actual key.

  • * default

If this exists and the value associated with the key of \%hash is undefined, Hash::Compact object $hash returns just the value. It's for space efficiency; $hash doesn't need to have key/value pair when the value isn't defined or it's same as default value.

param (I<$key>)

param (I<%pairs>)

$hash->param('foo'); #=> 'foo' $hash->param('bar'); #=> 'bar' (returns the default value)

$hash->param( bar => 'baz', qux => 'quux', ); $hash->param('bar'); #=> 'baz'

Setter/getter method.

compact ()

my $compact_hash_ref = $hash->compact; #=> { f => 'foo', b => 'baz' qux => 'quux' } (returns a compacted hash)

Returns a compacted hash according to \%options passed into the constructor above;

to_hash ()

This method will be deprecated and removed at later version.

keys ()

@keys = $hash->keys; #=> (foo, bar, qux)

Returns the original key names. If default option is set for a key, the key will be returned even if the value associated with the key is not set.

original ()

my $original_hash_ref = $hash->original; #=> { foo => 'foo', bar => 'baz' qux => 'quux' } (returns an original hash)

Returns the original key-value pairs as HashRef, which includes key-value pairs if the key-values not set but default option is designated.


Kentaro Kuribayashi kentarok@gmail.com



Copyright (C) Kentaro Kuribayashi

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