User Guide

240 Working with Arrays

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 object—the

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";

To make the object referenced by myObject eligible for garbage collection, you must remove

all references to it. In this case, you must change the value of

myObject and delete the

myObject key from myMap, as shown in the following code:

myObject = null;

delete myMap[myObject];

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.

Multidimensional arrays

Multidimensional arrays contain other arrays as elements. For example, consider a list of tasks

that is stored as an indexed array of strings:

var tasks:Array = ["wash dishes", "take out trash"];

If you want to store a separate list of tasks for each day of the week, you can create a

multidimensional array with one element for each day of the week. Each element contains an

indexed array, similar to the

tasks array, that stores the list of tasks. You can use any

combination of indexed or associative arrays in multidimensional arrays. The examples in the

following sections use either two indexed arrays or an associative array of indexed arrays. You

might want to try the other combinations as exercises.