NAME
Tie::Hash::MultiKey - multiple keys per value
SYNOPSIS
use Tie::Hash::MultiKey;
$accessor = tie %hash, qw(Tie::Hash::MultiValue);
$accessor = tied %hash;
untie %hash;
$hash{'foo'} = 'baz';
or
$hash{'foo', 'bar'} = 'baz';
or
$array_ref = ['foo', 'bar'];
$hash{ $array_ref } = 'baz';
print $hash{foo}; # prints 'baz'
print $hash{bar}; # prints 'baz'
$array_ref = ['fuz','zup'];
$val = tied(%hash)->addkey('fuz' => 'bar');
$val = tied(%hash)->addkey('fuz','zup' => 'bar');
$val = tied(%hash)->addkey( $array_ref => 'bar');
print $hash{fuz} # prints 'baz'
$array_ref = ['foo', 'bar'];
$val = tied(%hash)->remove('foo');
$val = tied(%hash)->remove('foo', 'bar');
$val = tied(%hash)->remove( $array_ref );
@list = tied(%hash)->keylist('foo')
$num_vals = tied(%hash)->consolidate;
All of the above methods can be accessed as:
i.e. $accessor->consolidate;DESCRIPTION
Tie::Hash::MultiKey creates hashes that can have multiple keys for a single value. As shown in the SYNOPSIS, multiple keys share a common value.
Additional keys can be added that share the same value and keys can be removed without deleting other keys that share that value.
STORE..ing a value for one or more keys that already exist will overwrite the existing value and add any missing keys to the key group for that value.
WARNING: multiple key values supplied as an ARRAY to STORE and DELETE operations are passed by Perl as a single string separated by the $; multidimensional array seperator. i.e.
$hash{'a','b','c'} = $something;
or
@keys = ('a','b','c');
$hash{@keys} = $something'This really means $hash{join($;, 'a','b','c')};
Tie::Hash::MultiKey will do the right thing as long as your keys DO NOT contain binary data the may include the $; separator character.
It is recommended that you use the ARRAY_REF construct to supply multiple keys for binary data. i.e.
$hash{['a','b','c']} = $something;
or
$keys = ['a','b','c'];
$hash{$keys} = $something;This construct is ALWAYS safe.
$acc = tie %hash,'Tie::Hash::MultiValue';
Ties a %hash to this package for enhanced capability and returns a method pointer.
my %hash; my $accessor = tie %hash,'Tie::Hash::MultiValue';$acc = tied %hash;
Returns a method pointer for this package.
untie %hash;
Breaks the binding between a variable and this package. There is no affect if the variable is not tied.
$val = ->addkey('new_key' => 'existing_key');
Add one or more keys to the shared key group for a particular value.
input: array or array_ref, existing_key returns: hash value or dies with stack traceDies with stack trace if existing_key does not exist OR if new key belongs to another key set.
Arguments may be a single SCALAR, ARRAY, or ARRAY_REF
$val = ->remove('key');
Remove one or more keys from the shared key group for a particular value If this operation removes the LAST key, then it performs a DELETE which is the same as:
delete $hash{key};remove returns a reverse list of the removed value's by key
i.e. @val = remove(something); or $val = remove(something);Arguments may be a single SCALAR, ARRAY or ARRAY_REF
@list = ->keylist('foo');
Returns all the shared keys for KEY 'foo', including 'foo'
input: key returns: @shared_keys->consolidate;
USE WITH CAUTION
This method consolidates all keys with a common values.
returns: number of consolidated key groups
COMMON OPERATIONS
A tied multikey %hash behave like a regular %hash for most operations;
B<$value = $hash{$key}> returns the key group value
B<$hash{$key} = $value> sets the value for the key group
i.e. all keys in the group will return that value
B<$hash{$key1,$key2} = $value assigns $value to the key
key group consisting of $key1, $key2 if they do not.
If at least one of the keys already exists, the remaining
keys are assigned to the key group and the value is set
for the entire group.
B<Better> syntax $hash{[$key,$key]} = $value;
B<delete $hash{$key}> deletes the ENTIRE key group
to which B<$key> belongs.
B<delete $hash($key1,$key2> deletes ALL groups
to which $key1 and $key2 belong.
B<Better> syntax delete $hash{[$key1,$key2]};
B<keys %hash> returns all keys.
B<values %hash> returns all values
NOTE: that this will not be the same number of
items as returned by B<keys> unless there are no
key groups containing more than one key.
B<($k,$v) = each %hash> behaves as expected.References to tied %hash behave in the same manner as regular %hash's except as noted for multiple key values above.
LIMITATIONS
SLICE operations may produce unusual results. Tie::Hash::MultiKey hashs only accept SCALAR or ARRAY_REF arguments for SLICE and direct assigment.
i.e.
%WRONG = (
one => 1,
two => 2,
(3,4,5) => 12 # expands to 3 => 4, 5 => 12
);
%hash = ( # OK
one => 1,
two => 2,
[3,4,5] => 12
);will produce a psuedo hash of the form:
%hash = (
one => 1,
two => 2,
3 => 12, --|
4 => 12, --|
5 => 12 --|
);where the operation $hash{4} = 99 will change the hash to:
%hash = (
one => 1,
two => 2,
3 => 99, --|
4 => 99, --|
5 => 99 --|
);Example: $hp = \%hash;
@{$hp}{'one','two','[3,4,5]} = (1,2,12);produces the same result as above. If the hash already contains a KEY of the same name, the value will be changed for all other shared keys.
--------------------------If you are using ARRAY_REF's as keys (not as pointers to keys as above) they must be blessed into some other package so that
ref $key ne 'ARRAY'i.e. bless $key, 'KEY'; # or anything other than 'ARRAY'
--------------------------Example SLICE assignments
TO tied hash
@tiedhash{@keys} = @values;
$hp = \%tiedhash;
@{$hp}{@keys} = @values;FROM tied hash
@values = @tiedhash{@keys};
$hp = \%tiedhash;
@values = @{$hp}{@keys};NOTE: when assigning TO the hash, keys may be ARRAY_REF's as described above.
AUTHOR
Michael Robinton, <miker@cpan.org>
COPYRIGHT
Copyright 2014, Michael Robinton
This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.