The random utterances of David Arno

As part of writing a preprocessor for generating AS3 enums, I hit upon the need for a means of passing around a set of enums in a way that couldn’t corrupt the original data. After a bit of thought and digging around the core Flash/ Flex classes, I realised that:

1. There are no immutable collections in Flash or Flex.
2. Immutable collections are  fairly easy to create using standard AS3 and the magical Proxy class.

Lets take a step back and consider what I mean by an immutable collection. To demonstrate this, consider an arbitrary class Wibble:

class Wibble
{
  public var wobble:Boolean = true;
}

If we have an array of Wibble objects:

var array:Array = [new Wibble(), new Wibble(), new Wibble()]

we are free to manipulate that array as we wish:

array[1].wobble = false;
array[0] = 0;
array = null;
array = [];

The last three actions change the array. The first one changes the state of one of the values of the array. This distinction is important, for if Array were immutable collection, only the first action would be valid. The values of an immutable collection cannot be changed, but the state of those values can be.

With that in mind, I have created a small suite of immutable collection classes:

The API documentation is available online here. Don’t forget you can use “Doc? AIR” to create an offline version if that suits you better.

The SWC library and source can be downloaded here.

Tutorial posts on each of the classes will appear here soon.