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Tie::Hash::Method(3) User Contributed Perl Documentation Tie::Hash::Method(3)


Tie::Hash::Method - Tied hash with specific methods overriden by callbacks


Version 0.02


    tie my %hash, 'Tie::Hash::Method',
        FETCH => sub {
            exists $_[0]->base_hash->{$_[1]} ? $_[0]->base_hash->{$_[1]} : $_[1]


Tie::Hash::Method provides a way to create a tied hash with specific overriden behaviour without having to create a new class to do it. A tied hash with no methods overriden is functionally equivalent to a normal hash.

Each method in a standard tie can be overriden by providing a callback to the tie call. So for instance if you wanted a tied hash that changed 'foo' into 'bar' on store you could say:

    tie my %hash, 'Tie::Hash::Method',
        STORE => sub {
            (my $v=pop)=~s/foo/bar/g if defined $_[2];
            return $_[0]->base_hash->{$_[1]}=$v;

The callback is called with exactly the same arguments as the tie itself, in particular the tied object is always passed as the first argument.

The tied object is itself an array, which contains a second hash in the HASH slot (index 0) which is used to perform the default operations.

The callbacks available are in a hash keyed by name in the METHOD slot of the array (index 1).

If your code needs to store extra data in the object it should be stored in the PRIVATE slot of the object (index 2). No future release of this module will ever use or alter anything in that slot.

The arguments passed to the tie constructor will be seperated by the case of their keys. The ones with all capitals will be stored in the METHOD hash, and the rest will be stored in the PRIVATE hash.


Store datum value into key for the tied hash this.
Retrieve the datum in key for the tied hash this.
Return the first key in the hash.
Return the next key in the hash.
Verify that key exists with the tied hash this.
Delete the key key from the tied hash this.
Clear all values from the tied hash this.
Returns what evaluating the hash in scalar context yields.


return or sets the underlying hash for this tie.

    $_[0]->base_hash->{$key}= $value;
alias for base_hash.

    $_[0]->h->{$key}= $value;
Return or sets the hash of private data associated with this tie. This value will never be touched by any code in this class or its subclasses. It is purely object specific.

    $_[0]->p->{'something'}= 'cake!';
alias for private_hash
return or sets the hash of methods that are overriden for this tie. Exactly why you would want to use this is a little beyond my imagination, but for those who can think of a reason here is a nice way to do it. :-)
Returns a list of methods that are overriden for this tie. Why this would be useful escapes me, but here it is anyway for Completeness sake, whoever she is, but people are always coding for her so I might as well too.

Exportable Subs

The following subs are exportable on request:

Returns a reference to a hash tied with the specified callbacks overriden. Just a short cut.
Constant subroutine equivalent to 0
Constant subroutine equivalent to 1
Constant subroutine equivalent to 2


Yves Orton, "<yves at>"


Please report any bugs or feature requests to "bug-tie-hash-method at", or through the web interface at <>. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.


You can find documentation for this module with the perldoc command.

    perldoc Tie::Hash::Method

You can also look for information at:



Copyright 2008 Yves Orton, all rights reserved.

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

2017-11-27 perl v5.40.0