66. Visitor, cont.

• One possible solution is to

  1. derive all objects from a common base class

  2. add required operations to existing classes.

• However, many distinct and unrelated operations will be performed on the nodes of the three-dimensional scene structure...

  • ...and sometimes it is best to avoid "polluting" existing classes with new operations.

• Better solution: use Visitor design pattern, which allows to

  1. traverse objects inside complex structures

  2. keep related operations together by defining them inside the Visitor class.