DESCRIPTION

The Web::XPath::VariableBindings module is a set of variable bindings used to parse and evaluate XPath 1.0 expressions. This class, its subclass, or any class that implements the required methods as described in later section can be used as the variable bindings for the Web::XPath::Parser and Web::XPath::Evaluator modules.

In many cases the Web::XPath::VariableBindings module is useful enough. However, it sometimes desired to implement a custom variable bindings module, e.g. for sharing XSLT variable bindings among XPath and XSLT implementations.

METHODS

The Web::XPath::VariableBindings module has the new class method, which returns a new instance of the empty variable bindings.

The module that can be used as the set of variable bindings in parsing or evaluating of expressions must implement the following instance methods:

$boolean = $vars->has_variable ($nsurl, $ln)

Return whether the specified variable is defined or not. It is invoked with two Perl character string arguments: namespace URL and local name. If the namespace URL is undef, it represents the null namespace. Note that the empty string is different from undef. It must return whether the variable identified by the namespace URL and local name is defined or not, as a Perl boolean value. It must not throw an exception. It must return consistent result.

$value = $vars->get_variable ($nsurl, $ln)

Return the value bound to the specified variable, if any. It is invoked with two Perl character string arguments: namespace URL and local name. If the namespace URL is undef, it represents the null namespace. Note that the empty string is different from undef. It must return the XPath value bound to the variable identified by the namespace URL and local name, if any. If the variable is not bound to any value, it must return undef. It must not throw an exception. It must return consistent result.

$vars->set_variable ($nsurl, $ln, $value)

Add a variable binding. The first and second arguments must be a Perl character string representing the namespace URL and the local name of the variable. If the namespace URL is undef, it represents the null namespace. The third argument must be an XPath value. It must not throw an exception. It must return consistent result.

If the variable is already bound to another value, the old binding is removed.

SEE ALSO

Web::XPath::Parser, Web::XPath::Evaluator.

See Web::XPath::Evaluator for XPath value data structures.

SPECIFICATION

XPATH

XML Path Language (XPath) Version 1.0 <http://www.w3.org/TR/xpath/>.

AUTHOR

Wakaba <wakaba@suikawiki.org>.

LICENSE

Copyright 2013 Wakaba <wakaba@suikawiki.org>.

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