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.\"
.IX Title "AptPkg::hash 3pm"
.TH AptPkg::hash 3pm "2021-02-15" "perl v5.32.1" "User Contributed Perl Documentation"
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.SH "NAME"
AptPkg::hash \- a helper class for implementing tied hashes
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
use AptPkg::hash;
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The AptPkg::hash class provides hash-like access for objects which
have an underlying \s-1XS\s0 implementation.
.PP
Such objects need to add AptPkg::hash to \f(CW@ISA\fR, provide get, set and
exists methods, and an iterator class.
.SS "AptPkg::hash"
.IX Subsection "AptPkg::hash"
.IP "new([\fI\s-1XS_OBJECT\s0\fR])" 4
.IX Item "new([XS_OBJECT])"
Create a object as a tied hash.  The object is implemented as a hash
reference blessed into the class, which in turn is tied to
AptPkg::hash.
.Sp
This means that both \f(CW$obj\fR\->\fBmethod()\fR and \f(CW$obj\fR\->{key} valid, the latter
invoking get/set (through \s-1FETCH/STORE\s0).
.Sp
The tie associates an array reference with the hash, which initially
contains a reference to the hash, the \s-1XS\s0 object and an anon hash
which may be used by subclasses to store state information.
.Sp
If no \s-1XS\s0 object is passed, one is created via new in the \s-1XS\s0 class.
The name of that class is constructed from the class name, by
lower-casing the last component and prefixing it with an underscore
(eg. AptPkg::Config becomes AptPkg::_config).
.Sp
If the module contains a \f(CW@KEYS\fR array, then the private hash will be
populated with those entries as keys (see the description below of the
AptPkg::hash::method class).
.IP "_self, _xs, _priv" 4
.IX Item "_self, _xs, _priv"
Accessors which may be used in subclass methods to fetch the three
array elements associated with the hash reference.
.IP "keys(\fI\s-1ARGS\s0\fR)" 4
.IX Item "keys(ARGS)"
In a scalar context, creates and returns a new iterator object (the
class name with the suffix ::Iter appended).
.Sp
The \s-1XS\s0 object, the private hash and any arguments are passed to the
constructor.
.Sp
In an array context, the iterator is used to generate a list of keys
which are then returned.
.Sp
The iterator class must implement a next method, which returns the
current key and advances to the next.
.SS "AptPkg::hash::method"
.IX Subsection "AptPkg::hash::method"
The AptPkg::hash::method class extends AptPkg::hash, providing a
simple way to map a fixed set of keys (defined by the \f(CW@KEYS\fR array)
into method calls on either the object, or the internal \s-1XS\s0 object.
.PP
Classes inheriting from AptPkg::hash::method should provide an
iterator class which inherits from AptPkg::hash::method::iter.
.SH "AUTHOR"
.IX Header "AUTHOR"
Brendan O'Dea <bod@debian.org>