Hierarchy(3)						User Contributed Perl Documentation					      Hierarchy(3)

NAME

       Data::Hierarchy - Handle data in a hierarchical structure

SYNOPSIS

	   my $tree = Data::Hierarchy->new();
	   $tree->store ('/', {access => 'all'});
	   $tree->store ('/private', {access => 'auth',
				      '.note' => 'this is private});

	   $info = $tree->get ('/private/somewhere/deep');

	   # return actual data points in list context
	   ($info, @fromwhere) = $tree->get ('/private/somewhere/deep');

	   my @items = $tree->find ('/', {access => qr/.*/});

	   # override all children
	   $tree->store ('/', {'.note' => undef}, {override_sticky_descendents => 1});

DESCRIPTION

       Data::Hierarchy provides a simple interface for manipulating inheritable data attached to a hierarchical environment (like a filesystem).

       One use of Data::Hierarchy is to allow an application to annotate paths in a real filesystem in a single compact data structure. However,
       the hierarchy does not actually need to correspond to an actual filesystem.

       Paths in a hierarchy are referred to in a Unix-like syntax; "/" is the root "directory". (You can specify a different separator character
       than the slash when you construct a Data::Hierarchy object.)  With the exception of the root path, paths should never contain trailing
       slashes. You can associate properties, which are arbitrary name/value pairs, with any path.  (Properties cannot contain the undefined
       value.)	By default, properties are inherited by child paths: thus, if you store some data at "/some/path":

	   $tree->store('/some/path', {color => 'red'});

       you can fetch it again at a "/some/path/below/that":

	   print $tree->get('/some/path/below/that')->{'color'};
	   # prints red

       On the other hand, properties whose names begin with dots are uninherited, or "sticky":

	   $tree->store('/some/path', {'.color' => 'blue'});
	   print $tree->get('/some/path')->{'.color'};		  # prints blue
	   print $tree->get('/some/path/below/that')->{'.color'}; # undefined

       Note that you do not need to (and in fact, cannot) explicitly add "files" or "directories" to the hierarchy; you simply add and delete
       properties to paths.

CONSTRUCTOR

       Creates a new hierarchy object.	Takes the following options:

       sep The string used as a separator between path levels. Defaults to '/'.

METHODS

   Instance Methods
       "store $path, $properties, {%options}"
	   Given a path and a hash reference of properties, stores the properties at the path.

	   Unless the "override_descendents" option is given with a false value, it eliminates any non-sticky property in a descendent of $path
	   with the same name.

	   If the "override_sticky_descendents" option is given with a true value, it eliminates any sticky property in a descendent of $path with
	   the same name.  override it.

	   A value of undef removes that value; note, though, that if an ancestor of $path defines that property, the ancestor's value will be
	   inherited there; that is, with:

	       $t->store('/a',	 {k => 'top'});
	       $t->store('/a/b', {k => 'bottom'});
	       $t->store('/a/b', {k => undef});
	       print $t->get('/a/b')->{'k'};

	   it will print 'top'.

       "get $path, [$dont_clone]"
	   Given a path, looks up all of the properteies (sticky and not) and returns them in a hash reference.  The values are clones, unless you
	   pass a true value for $dont_clone.

	   If called in list context, returns that hash reference followed by all of the ancestral paths of $path which contain non-sticky
	   properties (possibly including itself).

       "find $path, $property_regexps"
	   Given a path and a hash reference of name/regular expression pairs, returns a list of all paths which are descendents of $path
	   (including itself) and define at that path itself (not inherited) all of the properties in the hash with values matching the given
	   regular expressions.  (You may want to use "qr/.*/" to merely see if it has any value defined there.)  Properties can be sticky or not.

       "merge $other_hierarchy, $path"
	   Given a second Data::Hierarchy object and a path, copies all the properties from the other object at $path or below into the
	   corresponding paths in the object this method is invoked on.  All properties from the object this is invoked on at $path or below are
	   erased first.

       "to_relative $base_path"
	   Given a path which every element of the hierarchy must be contained in, returns a special Data::Hierarchy::Relative object which
	   represents the hierarchy relative that path. The only thing you can do with a Data::Hierarchy::Relative object is call
	   "to_absolute($new_base_path)" on it, which returns a new Data::Hierarchy object at that base path. For example, if everything in the
	   hierarchy is rooted at "/home/super_project" and it needs to be moved to "/home/awesome_project", you can do

	       $hierarchy = $hierarchy->to_relative('/home/super_project')->to_absolute('/home/awesome_project');

	   (Data::Hierarchy::Relative objects may be a more convenient serialization format than Data::Hierarchy objects, if they are tracking the
	   state of some relocatable resource.)

AUTHORS

       Chia-liang Kao <clkao@clkao.org> David Glasser <glasser@mit.edu>

COPYRIGHT

       Copyright 2003-2006 by Chia-liang Kao <clkao@clkao.org>.

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

       See <http://www.perl.com/perl/misc/Artistic.html>

perl v5.18.2							    2006-11-04							      Hierarchy(3)