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 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.
- 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.
- base_hash
-
return or sets the underlying hash for this tie.
$_[0]->base_hash->{$key}= $value;
- h
-
alias for base_hash.
$_[0]->h->{$key}= $value;
- private_hash
-
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!';
- p
-
alias for private_hash
- method_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. :-)
- methods
-
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.
The following subs are exportable on request:
- hash_overload(PAIRS)
-
Returns a reference to a hash tied with the specified
callbacks overriden. Just a short cut.
- HASH
-
Constant subroutine equivalent to 0
- METHOD
-
Constant subroutine equivalent to 1
- PRIVATE
-
Constant subroutine equivalent to 2
Yves Orton, <yves at cpan.org>
Please report any bugs or feature requests to bug-tie-hash-method at rt.cpan.org, or through
the web interface at http://rt.cpan.org/NoAuth/ReportBug.html. 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.
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