Data::Grove::Visitor(3) 				User Contributed Perl Documentation				   Data::Grove::Visitor(3)

NAME

       Data::Grove::Visitor - add visitor/callback methods to Data::Grove objects

SYNOPSIS

	use Data::Grove::Visitor;

	@results = $object->accept ($visitor, ...);
	@results = $object->accept_name ($visitor, ...);
	@results = $object->children_accept ($visitor, ...);
	@results = $object->children_accept_name ($visitor, ...);

DESCRIPTION

       Data::Grove::Visitor adds visitor methods (callbacks) to Data::Grove objects.  A ``visitor'' is a class (a package) you write that has
       methods (subs) corresponding to the objects in the classes being visited.  You use the visitor methods by creating an instance of your
       visitor class, and then calling `"accept($my_visitor)"' on the top-most object you want to visit, that object will in turn call your
       visitor back with `"visit_OBJECT"', where OBJECT is the type of object.

       There are several forms of `"accept"'.  Simply calling `"accept"' calls your package back using the object type of the object you are
       visiting.  Calling `"accept_name"' on an element object calls you back with `"visit_name_NAME"' where NAME is the tag name of the element,
       on all other objects it's as if you called `"accept"'.

       All of the forms of `"accept"' return a concatenated list of the result of all `"visit"' methods.

       `"children_accept"' calls `"accept"' on each of the children of the element.  This is generally used in element callbacks to recurse down
       into the element's children, you don't need to get the element's contents and call `"accept"' on each item.  `"children_accept_name"' does
       the same but calling `"accept_name"' on each of the children.  `"attr_accept"' calls `"accept"' on each of the objects in the named
       attribute.

       Refer to the documentation of the classes you are visiting (XML::Grove, etc.) for the type names (`"element"', `"document"', etc.) of the
       objects it implements.

RESERVED NAMES

       The hash keys `"Contents"' and `"Name"' are used to indicate objects with children (for `"children_accept"') and named objects (for
       `"accept_name"').

NOTES

       These are random ideas that haven't been implemented yet:

       o   Several objects fall into subclasses, or you may want to be able to subclass a visited object and still be able to tell the difference.
	   In SGML::Grove I had used the package name in the callback (`"visit_SGML_Element"') instead of a generic name (`"visit_element"').  The
	   idea here would be to try calling `"visit_PACKAGE"' with the most specific class first, then try superclasses, and lastly to try the
	   generic.

AUTHOR

       Ken MacLeod, ken@bitsko.slc.ut.us

SEE ALSO

       perl(1), Data::Grove

       Extensible Markup Language (XML) <http://www.w3c.org/XML>

perl v5.16.3							    2003-10-21						   Data::Grove::Visitor(3)