Always in motion, is the future.

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At the MAX 2010 conference, Adobe announced the launch of the cross-platform AIR runtime environment. What this means is that the now apps created for the Adobe’s AIR runtime will now have a larger audience in the form of televisions (Samsung has announced the support for the new AIR 2.5 runtime in its SmartTVs), tablets and smartphones based on BlackBerry Tablet OS, Android and iOS, along with the already supported, desktop operating systems including Windows, Macintosh and Linux.

In addition to AIR 2.5, Adobe has also unveiled Adobe InMarket, a new service that allows developers to distribute and sell their applications across different device types on app stores from Acer, Intel, and others.

The new AIR runtime includes new features such as support for SQLite databases, accelerometer, camera, video, microphone, multi-touch, gestures and geo-location along with the ability to support native browser controls within the application.

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ActionScript allows defining dynamic classes which facilitate adding public properties and methods to them at run time. Internally these classes maintain a hash table for storing the properties and methods added at run-time.

Since ActionScript 3, a Dictionary class is available which allows for creating <key, value> mappings but it lacks the interface that, for example, C++’s std::map provides.

Adding properties at run-time can be leveraged to implement a very simple hashmap which, unfortunately, is not available in ActionScript.

Below is a class which can be used as a hashmap.

//HashMap.as
 
import mx.collections.ArrayCollection;
 
public dynamic class HashMap
{
	private var size_:Number = 0;
	public function get size():Number
	{
		return size_;
	}
 
	/**
	 * Inserts a new  pair to the map
	 */
	public function insert(key:String, value:Object):void
	{
		// Only increment counter if the
		// item is not already in the map.
		if (!this.hasOwnProperty(key))
		{
			size_++;
		}
		this[key] = value;
	}
 
	/**
	 * Removes an element from the map
	 */
	public function erase(key:String):void
	{
		// Only decrement counter if the item is in the map.
		if (this[key])
		{
			size_--;
		}
		delete this[key];
	}
 
	/**
	 * Removes all elements from the map
	 */
	public function clear():void
	{
		for (var key:String in this)
		{
			delete this[key];
		}
		size_ == 0;
	}
 
	/**
	 * Returns the element identified by key `key`
	 */
	public function getItem(key:String):Object
	{
		return this[key];
	}
 
	/**
	 * Returns the element at index `index`
	 */
	public function getIemAt(index:int):*
	{
		var i:int = 0;
		for (var key:String in this)
		{
			if (i == index)
			{
				return this[key];
			}
			++i;
		}
		return null;
	}
 
	/**
	 * Check if the map contains any elements
	 */
	public function empty():Boolean
	{
		return size == 0;
	}
}

UPDATE (11/01/2010):

Thanks to a suggestion by Craig W, I have updated the code of HashMap class. The `size()` method has been replaced by property `size`. Also the `erase()` and `clear()` methods have been updated. They now use the `delete` operator to remove properties instead of setting the properties to `null` which was causing the `size()` method to return incorrect result.