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 v5.10.0 2006-11-04 Hierarchy(3)
Mac OS X 10.6 - Generated Thu Sep 17 20:11:33 CDT 2009