Data::Grove::Visitor - phpMan

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:

    *   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 AT bitsko.us

SEE ALSO
    perl(1), Data::Grove

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