AS3 Iterator Pattern Implementation

Monday, October 16th, 2006

The greatest thing about design patterns is that they are typically not much more than an efficient, structured way of doing things that most of us have already been doing for a long time. Design Patterns allow us to simplify common design problems into standard, common named solutions. By implementing common design patterns and best practices we can keep our applications consistant without re-inventing the wheel everytime. They allow us to solve the same problems over and over again in the same way. Design patterns also allow us to write code that is common amongst other developers. This is helpful as it allows other developers who are familiar with these patterns to easily and intuitively work with our code, and vice-versa.

Every Software Developer iterates over objects on a regular basis. That is, every software developer has the need to loop thru an array or traverse an object at some point during the development of an application. This is obviously a basic part of programming so we usually don’t give it much thought. However, once in while it is good to reflect upon the things that have become routine to determine if there is a common solution out there. We often run into situations where we create an API that consists of a collection of objects that a client may want to iterate over. In order to provide the required functionality we have to define an interface in which the client can iterate over our collection without exposing the collections underlying implementation. This is where the Iterator Pattern comes in handy. Iterators are used to access the elements of an aggregate object sequentially without exposing its underlying representation. Iterators are intended to remove traversal responsibility out of the aggregate object.

I have created an AS3 Iterator API which consists of an interface (IIterator) that defines the methods which implement the Iterator Pattern. The IIterator interface is implemented by an internal base class (Iterator) which is sub classed by concrete iterator implementations (ArrayIterator, ArrayCollectionIterator and ObjectIterator). I have also provided an IteratorFactory which handles instantiating Iterator sub-classes so that they may be referenced by the same iterator instance.

You can view the example and ASDoc as well as download the swc for the AS3 Iterator API.

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