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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .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$obj\fR\->\fImethod()\fR and \f(CW$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