ACTIONSCRIPT 3.0

Chapter 3: Working with arrays
Flash Player 9 and later, Adobe AIR 1.0 and later
Arrays allow you to store multiple values in a single data structure. You can use simple indexed arrays that store values
using fixed ordinal integer indexes or complex associative arrays that store values using arbitrary keys. Arrays can also
be multidimensional, containing elements that are themselves arrays. Finally, you can use a Vector for an array whose
elements are all instances of the same data type.
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Array
Vector
Basics of arrays
Flash Player 9 and later, Adobe AIR 1.0 and later
Often in programming you’ll need to work with a set of items rather than a single object. For example, in a music player
application, you might want to have a list of songs waiting to be played. You wouldn’t want to have to create a separate
variable for each song on that list. It would be preferable to have all the Song objects together in a bundle, and be able
to work with them as a group.
An array is a programming element that acts as a container for a set of items, such as a list of songs. Most commonly
all the items in an array are instances of the same class, but that is not a requirement in ActionScript. The individual
items in an array are known as the array’s elements. You can think of an array as a file drawer for variables. Variables
can be added as elements in the array, which is like placing a folder into the file drawer. You can work with the array
as a single variable (like carrying the whole drawer to a different location). You can work with the variables as a group
(like flipping through the folders one by one searching for a piece of information). You can also access them
individually (like opening the drawer and selecting a single folder).
For example, imagine you’re creating a music player application where a user can select multiple songs and add them
to a playlist. In your ActionScript code, you have a method named addSongsToPlaylist(), which accepts a single
array as a parameter. No matter how many songs you want to add to the list (a few, a lot, or even only one), you call
the addSongsToPlaylist() method only one time, passing it the array containing the Song objects. Inside the
addSongsToPlaylist() method, you can use a loop to go through the array’s elements (the songs) one by one and
actually add them to the playlist.
The most common type of ActionScript array is an indexed array. In an indexed array each item is stored in a
numbered slot (known as an index). Items are accessed using the number, like an address. Indexed arrays work well
for most programming needs. The Array class is one common class that’s used to represent an indexed array.
Often, an indexed array is used to store multiple items of the same type (objects that are instances of the same class).
The Array class doesn’t have any means for restricting the type of items it contains. The Vector class is a type of indexed
array in which all the items in a single array are the same type. Using a Vector instance instead of an Array instance
can also provide performance improvements and other benefits. The Vector class is available starting with Flash Player
10 and Adobe AIR 1.5.
Last updated 4/22/2013
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