Data::Grove::Visitor - add visitor/callback methods to Data::Grove objects
use Data::Grove::Visitor; @results = $object->accept ($visitor, ...); @results = $object->accept_name ($visitor, ...); @results = $object->children_accept ($visitor, ...); @results = $object->children_accept_name ($visitor, ...);
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($my_visitor)' on the top-most object you want to visit, that object will in turn call your visitor back with `visit_OBJECT', where OBJECT is the type of object.
accept($my_visitor)
visit_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'.
accept
accept_name
visit_name_NAME
All of the forms of `accept' return a concatenated list of the result of all `visit' methods.
visit
`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.
children_accept
children_accept_name
attr_accept
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.
element
document
The hash keys `Contents' and `Name' are used to indicate objects with children (for `children_accept') and named objects (for `accept_name').
Contents
Name
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.
visit_SGML_Element
visit_element
visit_PACKAGE
Ken MacLeod, ken@bitsko.slc.ut.us
perl(1), Data::Grove
Extensible Markup Language (XML) <http://www.w3c.org/XML>
To install Data::Grove, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Data::Grove
CPAN shell
perl -MCPAN -e shell install Data::Grove
For more information on module installation, please visit the detailed CPAN module installation guide.