Tie::Hash::Regex(3pm) User Contributed Perl Documentation Tie::Hash::Regex(3pm)NAME
Tie::Hash::Regex - Match hash keys using Regular Expressions
SYNOPSIS
use Tie::Hash::Regex;
my %h;
tie %h, 'Tie::Hash::Regex';
$h{key} = 'value';
$h{key2} = 'another value';
$h{stuff} = 'something else';
print $h{key}; # prints 'value'
print $h{2}; # prints 'another value'
print $h{'^s'}; # prints 'something else'
print tied(%h)->FETCH(k); # prints 'value' and 'another value'
delete $h{k}; # deletes $h{key} and $h{key2};
or (new! improved!)
my $h : Regex;
DESCRIPTION
Someone asked on Perlmonks if a hash could do fuzzy matches on keys - this is the result.
If there's no exact match on the key that you pass to the hash, then the key is treated as a regex and the first matching key is returned.
You can force it to leap straight into the regex checking by passing a qr'ed regex into the hash like this:
my $val = $h{qr/key/};
"exists" and "delete" also do regex matching. In the case of "delete" all vlaues matching your regex key will be deleted from the hash.
One slightly strange thing. Obviously if you give a hash a regex key, then it's possible that more than one key will match (consider
c<$h{qw/./}>). It might be nice to be able to do stuff like:
my @vals = $h{$pat};
to get all matching values back. Unfortuately, Perl knows that a given hash key can only ever return one value and so forces scalar context
on the "FETCH" call when using the tied interface. You can get round this using the slightly less readable:
my @vals = tied(%h)->FETCH($pat);
ATTRIBUTE INTERFACE
From version 0.06, you can use attributes to define your hash as being tied to Tie::Hash::Regex. You'll need to install the module
Attribute::Handlers.
METHODS
FETCH
Get a value from the hash. If there isn't an exact match try a regex match.
EXISTS
See if a key exists in the hash. If there isn't an exact match try a regex match.
DELETE
Delete a key from the hash. If there isn't an exact match try a regex match.
AUTHOR
Dave Cross <dave@mag-sol.com>
Thanks to the Perlmonks <http://www.perlmonks.org> for the original idea and to Jeff "japhy" Pinyan for some useful code suggestions.
COPYRIGHT
Copyright (C) 2001-8, Magnum Solutions Ltd. All Rights Reserved.
LICENSE
This script is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
SEE ALSO perl(1).
perltie(1).
Tie::RegexpHash(1)perl v5.10.0 2008-06-30 Tie::Hash::Regex(3pm)
Check Out this Related Man Page
Tie::Hash(3pm) Perl Programmers Reference Guide Tie::Hash(3pm)NAME
Tie::Hash, Tie::StdHash, Tie::ExtraHash - base class definitions for tied hashes
SYNOPSIS
package NewHash;
require Tie::Hash;
@ISA = qw(Tie::Hash);
sub DELETE { ... } # Provides needed method
sub CLEAR { ... } # Overrides inherited method
package NewStdHash;
require Tie::Hash;
@ISA = qw(Tie::StdHash);
# All methods provided by default, define only those needing overrides
# Accessors access the storage in %{$_[0]};
# TIEHASH should return a reference to the actual storage
sub DELETE { ... }
package NewExtraHash;
require Tie::Hash;
@ISA = qw(Tie::ExtraHash);
# All methods provided by default, define only those needing overrides
# Accessors access the storage in %{$_[0][0]};
# TIEHASH should return an array reference with the first element being
# the reference to the actual storage
sub DELETE {
$_[0][1]->('del', $_[0][0], $_[1]); # Call the report writer
delete $_[0][0]->{$_[1]}; # $_[0]->SUPER::DELETE($_[1])
}
package main;
tie %new_hash, 'NewHash';
tie %new_std_hash, 'NewStdHash';
tie %new_extra_hash, 'NewExtraHash',
sub {warn "Doing U$_[1]E of $_[2].
"};
DESCRIPTION
This module provides some skeletal methods for hash-tying classes. See perltie for a list of the functions required in order to tie a hash
to a package. The basic Tie::Hash package provides a "new" method, as well as methods "TIEHASH", "EXISTS" and "CLEAR". The Tie::StdHash and
Tie::ExtraHash packages provide most methods for hashes described in perltie (the exceptions are "UNTIE" and "DESTROY"). They cause tied
hashes to behave exactly like standard hashes, and allow for selective overwriting of methods. Tie::Hash grandfathers the "new" method: it
is used if "TIEHASH" is not defined in the case a class forgets to include a "TIEHASH" method.
For developers wishing to write their own tied hashes, the required methods are briefly defined below. See the perltie section for more
detailed descriptive, as well as example code:
TIEHASH classname, LIST
The method invoked by the command "tie %hash, classname". Associates a new hash instance with the specified class. "LIST" would
represent additional arguments (along the lines of AnyDBM_File and compatriots) needed to complete the association.
STORE this, key, value
Store datum value into key for the tied hash this.
FETCH this, key
Retrieve the datum in key for the tied hash this.
FIRSTKEY this
Return the first key in the hash.
NEXTKEY this, lastkey
Return the next key in the hash.
EXISTS this, key
Verify that key exists with the tied hash this.
The Tie::Hash implementation is a stub that simply croaks.
DELETE this, key
Delete the key key from the tied hash this.
CLEAR this
Clear all values from the tied hash this.
SCALAR this
Returns what evaluating the hash in scalar context yields.
Tie::Hash does not implement this method (but Tie::StdHash and Tie::ExtraHash do).
Inheriting from Tie::StdHash
The accessor methods assume that the actual storage for the data in the tied hash is in the hash referenced by "tied(%tiedhash)". Thus
overwritten "TIEHASH" method should return a hash reference, and the remaining methods should operate on the hash referenced by the first
argument:
package ReportHash;
our @ISA = 'Tie::StdHash';
sub TIEHASH {
my $storage = bless {}, shift;
warn "New ReportHash created, stored in $storage.
";
$storage
}
sub STORE {
warn "Storing data with key $_[1] at $_[0].
";
$_[0]{$_[1]} = $_[2]
}
Inheriting from Tie::ExtraHash
The accessor methods assume that the actual storage for the data in the tied hash is in the hash referenced by "(tied(%tiedhash))->[0]".
Thus overwritten "TIEHASH" method should return an array reference with the first element being a hash reference, and the remaining methods
should operate on the hash "%{ $_[0]->[0] }":
package ReportHash;
our @ISA = 'Tie::ExtraHash';
sub TIEHASH {
my $class = shift;
my $storage = bless [{}, @_], $class;
warn "New ReportHash created, stored in $storage.
";
$storage;
}
sub STORE {
warn "Storing data with key $_[1] at $_[0].
";
$_[0][0]{$_[1]} = $_[2]
}
The default "TIEHASH" method stores "extra" arguments to tie() starting from offset 1 in the array referenced by "tied(%tiedhash)"; this is
the same storage algorithm as in TIEHASH subroutine above. Hence, a typical package inheriting from Tie::ExtraHash does not need to
overwrite this method.
"SCALAR", "UNTIE" and "DESTROY"
The methods "UNTIE" and "DESTROY" are not defined in Tie::Hash, Tie::StdHash, or Tie::ExtraHash. Tied hashes do not require presence of
these methods, but if defined, the methods will be called in proper time, see perltie.
"SCALAR" is only defined in Tie::StdHash and Tie::ExtraHash.
If needed, these methods should be defined by the package inheriting from Tie::Hash, Tie::StdHash, or Tie::ExtraHash. See "SCALAR" in
perltie to find out what happens when "SCALAR" does not exist.
MORE INFORMATION
The packages relating to various DBM-related implementations (DB_File, NDBM_File, etc.) show examples of general tied hashes, as does the
Config module. While these do not utilize Tie::Hash, they serve as good working examples.
perl v5.16.2 2012-10-11 Tie::Hash(3pm)