The Iterator Design Pattern

Iterator Solutions

nAbstract traversal interface

narrayIterator.next()

ArrayIterator iterator(array); // C++

for (iterator.first();!iterator.atEnd();iterator.next())

sum+=iterator.current();

nlinkedListIterator.next()

LinkedListIterator iterator(linkedList); // C++

for (iterator.first();!iterator.atEnd();iterator.next())

sum+=iterator.current();

ntreeIterator.next()

nqueueIterator.next()

nor just iterator.next()


	Let’s look at how some of the problematic examples of iteration might look if we used an iterator instead. Here we have different iterators to traverse different kinds of structures: array, linked list, tree, and queue. Since they all use the same method, next(), we can define an interface or abstract class and use that for traversal.

	In C++ we can override operator++ and use it instead of next() so that we stay compatible with the old procedural code.