Data::Grove::Visitor(3) User Contributed Perl Documentation
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 v5.34.0 2003-10-21 Data::Grove::Visitor(3)
libxml-perl 0.80.0 - Generated Sat Aug 20 11:08:32 CDT 2022