Static Class Structure

• Client
  • Refers to the Aggregate interface to create an Iterator object.
  • Refers to the Iterator interface to access and traverse an Aggregate object.
• Aggregate
  • Defines an interface for creating an Iterator object.
• Aggregate1,…
  • Implement createIterator() by returning an instance of the corresponding iterator class (Iterator1).
• Iterator
  • Defines an interface for accessing and traversing the elements of an Aggregate object.
• Iterator1,…
  • Implement the Iterator interface.
  • An iterator is usually implemented as inner class of an aggregate class so that it can access the internal (private) data structures of the aggregate.

Dynamic Object Collaboration

• In this sample scenario, a Client object uses an Iterator1 object to traverse an Aggregate1 object front-to-back.
• The interaction starts with the Client object that calls createIterator() on the Aggregate1 object.
• Aggregate1 creates an Iterator1 object and returns (a reference to) it to the Client.
• Thereafter, the Client uses the Iterator1 to traverse the elements of Aggregate1 front-to-back (while iterator.hasNext(): iterator.next()).
• See also Sample Code / Example 1.