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Data::Grove -- support for deeply nested structures |
Data::Grove -- support for deeply nested structures
use Data::Grove;
$object = MyPackage->new;
package MyPackage;
@ISA = qw{Data::Grove};
Data::Grove provides support for deeply nested tree or graph
structures. Data::Grove is intended primarily for Perl module
authors writing modules with many types or classes of objects that
need to be manipulated and extended in a consistent and flexible way.
Data::Grove is best used by creating a core set of ``data'' classes
and then incrementally adding functionality to the core data classes
by using ``extension'' modules. One reason for this design is so that
the data classes can be swapped out and the extension modules can work
with new data sources. For example, these other data sources could be
disk-based, network-based or built on top of a relational database.
Two extension modules that come with Data::Grove are
Data::Grove::Parent and Data::Grove::Visitor.
Data::Grove::Parent adds a `Parent' property to grove objects
and implements a `root' method to grove objects to return the root
node of the tree from anywhere in the tree and a `rootpath' method
to return a list of nodes between the root node and ``this'' node.
Data::Grove::Visitor adds callback methods `accept' and
`accept_name' that call your handler or receiver module back by
object type name or the object's name.
Data::Grove objects do not contain parent references, Perl garbage
collection will delete them when no longer referenced and
sub-structures can be shared among several structures.
Data::Grove::Parent is used to create temporary objects with parent
pointers.
Properties of data classes are accessed directly using Perl's hash
functions (i.e. `$object->{Property}'). Extension modules may
also define properties that they support or use, for example
Data::Grove::Parent adds `Parent' and `Raw' properties and
Visitor depends on `Name' and `Content' properties.
See the module XML::Grove for an example implementation of
Data::Grove.
Data::Grove
object. If an existing Data::Grove is passed to `new()', a
shallow copy of that object will be returned. A shallow copy means
that you are returned a new object, but all of the objects underneath
still refer to the original objects.
Ken MacLeod, ken@bitsko.slc.ut.us
perl(1)
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Data::Grove -- support for deeply nested structures |