Associative arrays

The second way to create an associative array is to use the Array constructor (or the constructor of any dynamic class) and then use either the array access ( [] ) operator or the dot operator ( . ) to add key and value pairs to the array. If you declare your associative array to be of type Array, you cannot use an object literal to initialize the array. The following example creates an associative array named monitorInfo using the Array constructor and adds a key called type and a key called resolution , along with their values:

var monitorInfo:Array = new Array();
monitorInfo["type"] = "Flat Panel";
monitorInfo["resolution"] = "1600 x 1200";
trace(monitorInfo["type"], monitorInfo["resolution"]);
// output: Flat Panel 1600 x 1200

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After the array is created using either an object literal or the Object class constructor, you can add new values to the array using either the array access ( [] ) operator or the dot operator ( . ). The following example adds two new values to monitorArray :

monitorInfo["aspect ratio"] = "16:10"; // bad form, do not use spaces
monitorInfo.colors = "16.7 million";
trace(monitorInfo["aspect ratio"], monitorInfo.colors);
// output: 16:10 16.7 million

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The following code creates three instances of the Sprite class that serve as keys for the Dictionary object. Each key is assigned a value of either GroupA or GroupB . The values can be of any data type, but in this example both GroupA and GroupB are instances of the Object class. Subsequently, you can access the value associated with each key with the array access ( [] ) operator, as shown in the following code:

import flash.display.Sprite;
import flash.utils.Dictionary;

var groupMap:Dictionary = new Dictionary();

// objects to use as keys
var spr1:Sprite = new Sprite();
var spr2:Sprite = new Sprite();
var spr3:Sprite = new Sprite();

// objects to use as values
var groupA:Object = new Object();
var groupB:Object = new Object();

// Create new key-value pairs in dictionary.
groupMap[spr1] = groupA;
groupMap[spr2] = groupB;
groupMap[spr3] = groupB;

if (groupMap[spr1] == groupA)
{
    trace("spr1 is in groupA");
}
if (groupMap[spr2] == groupB)
{
    trace("spr2 is in groupB");
}
if (groupMap[spr3] == groupB)
{
    trace("spr3 is in groupB");
}

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If you use myObject as a key in a Dictionary object, you are creating another reference to the original object. For example, the following code creates two references to an objectthe myObject variable, and the key in the myMap object:

import flash.utils.Dictionary;

var myObject:Object = new Object();
var myMap:Dictionary = new Dictionary();
myMap[myObject] = "foo";

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Alternatively, you can use the useWeakReference parameter of the Dictionary constructor to make all of the dictionary keys weak references . The garbage collection system ignores weak references, which means that an object that has only weak references is eligible for garbage collection. For example, in the following code, you do not need to delete the myObject key from myMap in order to make the object eligible for garbage collection:

import flash.utils.Dictionary;

var myObject:Object = new Object();
var myMap:Dictionary = new Dictionary(true);
myMap[myObject] = "foo";
myObject = null; // Make object eligible for garbage collection.