Tree::DAG_Node::XPath - Add XPath support to Tree::DAG_Node
use Tree::DAG_Node::XPath;
# create a tree
my $root = Tree::DAG_Node::XPath->new()->name( "root_node");
$root->new_daughter->name("daugther$_") foreach (1..5);
# now use XPath to find nodes
my $roots= $root->find( '/root_node');
foreach (@$roots) { print "found root: ", $_->name, "\n"; }
my $daughters= $root->find( '/root_node/daugther2 | /root_node/daugther4');
foreach (@$daughters) { print "found daughter: ", $_->name, "\n"; }This package extends Tree::DAG_Node to add XPath queries to it
It adds the findnodes, matches and find methods to the base Tree::DAG_Node class.
With a little customization it can also add the findnodes_as_string and findvalue methods.
Returns a list of nodes found by $path, optionally in context $context. In scalar context returns an Tree::XPathEngine::NodeSet object.
Returns either a Tree::XPathEngine::Literal, a Tree::XPathEngine::Boolean or a Tree::XPathEngine::Number object. If the path returns a NodeSet, $nodeset->xpath_to_literal is called automatically for you (and thus a Tree::XPathEngine::Literal is returned). Note that for each of the objects stringification is overloaded, so you can just print the value found, or manipulate it in the ways you would a normal perl value (e.g. using regular expressions).
The find function takes an XPath expression (a string) and returns either an Tree::XPathEngine::NodeSet object containing the nodes it found (or empty if no nodes matched the path), or one of Tree::XPathEngine::Literal (a string), Tree::XPathEngine::Number, or Tree::XPathEngine::Boolean. It should always return something - and you can use isa() to find out what it returned. If you need to check how many nodes it found you should check $nodeset->size. See Tree::XPathEngine::NodeSet.
Returns true if the node matches the path (optionally in context $context).
You probably don't need to use those.
returns an array of attributes of the node (an arrayref in scalar context)
returns
returns an array of children of the node (an arrayref in scalar context)
returns the parent node
returns the root node of the tree
returns 1
returns 0
returns 0
compares 2 nodes and returns their order in the tree
alias for name
alias for right_sister
alias for left_sister
XPath is an XML standard, which is designed to work on a DOM (http://www.w3.org/DOM/DOMTR) tree. So the closer the tree you are working on mimics a DOM tree, the more of XPath you will be able to use.
In order for a generic tree to work better with XPath here are the main features that can be addressed:
In XPath, tokens in the query (node names and attribute names) must follow the rules for XML tokens (see the definition at http://xml.com/axml/target.html#NT-Nmtoken).
The definition of the tokens can be changed, within reasons: in order not to confuse the interpreter XPath delimiters cannot be used in tokens. '/', '[', '|', '!'.
Test carefully your expressions, so they don't confuse the XPath engine. For example qr/\w+/ is _not_ recommended, as numbers are then matched by the expression, making the XPath engine consider them as names.
None known at this time
better docs, especially on customizing derived classes to use more of XPath power
more tests (current coverage according to Devel::Cover: 96.2%)
if needed performance improvements (using address to sort the node sets is convenient but probably real slow, grabing the code to sort nodesfrom XML::Twig::XPath would likely be faster in most cases)
Tree::DAG_Node the base package that Tree::DAG_Node::XPath extends
Tree::XPathEngine the XPath engine for Tree::DAG_Node::XPath
http://www.w3.org/TR/xpath.html the XPath recommendations
examples are in the examples directory
Michel Rodriguez, <mirod@cpan.org>
Copyright (C) 2004 by Michel Rodriguez
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.4 or, at your option, any later version of Perl 5 you may have available.