phpman > perldoc > Data::Grove::Visitor(3pm)

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>