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.\" ========================================================================
.\"
.IX Title "Tie::Hash::MultiValueOrdered 3pm"
.TH Tie::Hash::MultiValueOrdered 3pm "2022-11-20" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Tie::Hash::MultiValueOrdered \- hash with multiple values per key, and ordered keys
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&   use Test::More;
\&   use Tie::Hash::MultiValueOrdered;
\&   
\&   my $tied = tie my %hash, "Tie::Hash::MultiValueOrdered";
\&   
\&   $hash{a} = 1;
\&   $hash{b} = 2;
\&   $hash{a} = 3;
\&   $hash{b} = 4;
\&   
\&   # Order of keys is predictable
\&   is_deeply(
\&      [ keys %hash ],
\&      [ qw( a b ) ],
\&   );
\&   
\&   # Order of values is predictable
\&   # Note that the last values of \*(Aqa\*(Aq and \*(Aqb\*(Aq are returned.
\&   is_deeply(
\&      [ values %hash ],
\&      [ qw( 3 4 ) ],
\&   );
\&   
\&   # Can retrieve list of all key\-value pairs
\&   is_deeply(
\&      [ $tied\->pairs ],
\&      [ qw( a 1 b 2 a 3 b 4 ) ],
\&   );
\&   
\&   # Switch the retrieval mode for the hash.
\&   $tied\->fetch_first;
\&   
\&   # Now the first values of \*(Aqa\*(Aq and \*(Aqb\*(Aq are returned.
\&   is_deeply(
\&      [ values %hash ],
\&      [ qw( 1 2 ) ],
\&   );
\&   
\&   # Switch the retrieval mode for the hash.
\&   $tied\->fetch_list;
\&   
\&   # Now arrayrefs are returned.
\&   is_deeply(
\&      [ values %hash ],
\&      [ [1,3], [2,4] ],
\&   );
\&   
\&   # Restore the default retrieval mode for the hash.
\&   $tied\->fetch_last;
\&   
\&   done_testing;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
A hash tied to this class acts more or less like a standard hash, except that
when you assign a new value to an existing key, the old value is retained
underneath. An explicit \f(CW\*(C`delete\*(C'\fR deletes all values associated with a key.
.PP
By default, the old values are inaccessible through the hash interface, but
can be retrieved via the tied object:
.PP
.Vb 1
\&   my @values = tied(%hash)\->get($key);
.Ve
.PP
However, the \f(CW\*(C`fetch_*\*(C'\fR methods provide a means to alter the behaviour of
the hash.
.SS "Tied Object Methods"
.IX Subsection "Tied Object Methods"
.ie n .IP """pairs""" 4
.el .IP "\f(CWpairs\fR" 4
.IX Item "pairs"
Returns all the hash's key-value pairs (including duplicates) as a flattened
list.
.ie n .IP """pair_refs""" 4
.el .IP "\f(CWpair_refs\fR" 4
.IX Item "pair_refs"
Returns all the hash's key-value pairs (including duplicates) as a list of two
item arrayrefs.
.ie n .IP """get($key)""" 4
.el .IP "\f(CWget($key)\fR" 4
.IX Item "get($key)"
Returns the list of all values associated with a key.
.ie n .IP """keys""" 4
.el .IP "\f(CWkeys\fR" 4
.IX Item "keys"
The list of all hash keys in their original order. Where a key is duplicated,
only the first occurrence is returned.
.ie n .IP """rr_keys""" 4
.el .IP "\f(CWrr_keys\fR" 4
.IX Item "rr_keys"
The list of all hash keys in their original order. Where a key is duplicated,
only the last occurrence is returned.
.ie n .IP """all_keys""" 4
.el .IP "\f(CWall_keys\fR" 4
.IX Item "all_keys"
The list of all hash keys in their original order, including duplicates.
.ie n .IP """values""" 4
.el .IP "\f(CWvalues\fR" 4
.IX Item "values"
The values corresponding to \f(CW\*(C`keys\*(C'\fR.
.ie n .IP """rr_values""" 4
.el .IP "\f(CWrr_values\fR" 4
.IX Item "rr_values"
The values corresponding to \f(CW\*(C`rr_keys\*(C'\fR.
.ie n .IP """all_values""" 4
.el .IP "\f(CWall_values\fR" 4
.IX Item "all_values"
The values corresponding to \f(CW\*(C`all_keys\*(C'\fR.
.SS "Fetch Styles"
.IX Subsection "Fetch Styles"
.ie n .IP """fetch_last""" 4
.el .IP "\f(CWfetch_last\fR" 4
.IX Item "fetch_last"
This is the default style of fetching.
.Sp
.Vb 1
\&   tie my %hash, "Tie::Hash::MultiValueOrdered";
\&   
\&   $hash{a} = 1;
\&   $hash{b} = 2;
\&   $hash{b} = 3;
\&   
\&   tied(%hash)\->fetch_last;
\&   
\&   is($hash{a}, 1);
\&   is($hash{b}, 3);
.Ve
.ie n .IP """fetch_first""" 4
.el .IP "\f(CWfetch_first\fR" 4
.IX Item "fetch_first"
.Vb 1
\&   tie my %hash, "Tie::Hash::MultiValueOrdered";
\&   
\&   $hash{a} = 1;
\&   $hash{b} = 2;
\&   $hash{b} = 3;
\&   
\&   tied(%hash)\->fetch_first;
\&   
\&   is($hash{a}, 1);
\&   is($hash{b}, 2);
.Ve
.ie n .IP """fetch_list""" 4
.el .IP "\f(CWfetch_list\fR" 4
.IX Item "fetch_list"
.Vb 1
\&   tie my %hash, "Tie::Hash::MultiValueOrdered";
\&   
\&   $hash{a} = 1;
\&   $hash{b} = 2;
\&   $hash{b} = 3;
\&   
\&   tied(%hash)\->fetch_first;
\&   
\&   is_deeply($hash{a}, [1]);
\&   is_deeply($hash{b}, [2, 3]);
.Ve
.ie n .IP """fetch_iterator""" 4
.el .IP "\f(CWfetch_iterator\fR" 4
.IX Item "fetch_iterator"
This fetch style is experimental and subject to change.
.Sp
.Vb 1
\&   tie my %hash, "Tie::Hash::MultiValueOrdered";
\&   
\&   $hash{a} = 1;
\&   $hash{b} = 2;
\&   $hash{b} = 3;
\&   
\&   tied(%hash)\->fetch_iterator;
\&   
\&   my $A = $hash{a};
\&   my $B = $hash{b};
\&   
\&   is($A\->(), 1);
\&   is($B\->(), 2);
\&   is($B\->(), 3);
.Ve
.SH "BUGS"
.IX Header "BUGS"
Please report any bugs to
<http://rt.cpan.org/Dist/Display.html?Queue=JSON\-MultiValueOrdered>.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
JSON::Tiny::Subclassable,
JSON::Tiny,
Mojo::JSON.
.SH "AUTHOR"
.IX Header "AUTHOR"
Toby Inkster <tobyink@cpan.org>.
.SH "COPYRIGHT AND LICENCE"
.IX Header "COPYRIGHT AND LICENCE"
This software is copyright (c) 2012\-2013 by Toby Inkster.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
.SH "DISCLAIMER OF WARRANTIES"
.IX Header "DISCLAIMER OF WARRANTIES"
\&\s-1THIS PACKAGE IS PROVIDED \*(L"AS IS\*(R" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.\s0