ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working with arrays
You can also create arrays with Array literals. An Array literal can be assigned directly to an array variable, as shown
in the following example:
var names:Array = ["John", "Jane", "David"];
Creating a Vector instance
Flash Player 10 and later, Adobe AIR 1.5 and later
You create a Vector instance by calling the Vector.() constructor. You can also create a Vector by calling the
Vector.() global function. That function converts a specified object to a Vector instance. In Flash
Professional CS5 and later, Flash Builder 4 and later, and Flex 4 and later, you can also create a vector instance by using
Vector literal syntax.
Any time you declare a Vector variable (or similarly, a Vector method parameter or method return type) you specify
the base type of the Vector variable. You also specify the base type when you create a Vector instance by calling the
Vector.() constructor. Put another way, any time you use the term Vector in ActionScript, it is accompanied by
a base type.
You specify the Vector’s base type using type parameter syntax. The type parameter immediately follows the word
Vector in the code. It consists of a dot (.), then the base class name surrounded by angle brackets (), as shown in
this example:
var v:Vector.;
v = new Vector.();
In the first line of the example, the variable v is declared as a Vector. instance. In other words, it represents
an indexed array that can only hold String instances. The second line calls the Vector() constructor to create an
instance of the same Vector type (that is, a Vector whose elements are all String objects). It assigns that object to v.
Using the Vector.() constructor
If you use the Vector.() constructor without any arguments, it creates an empty Vector instance. You can test
that a Vector is empty by checking its length property. For example, the following code calls the Vector.()
constructor with no arguments:
var names:Vector. = new Vector.();
trace(names.length); // output: 0
If you know ahead of time how many elements a Vector initially needs, you can pre-define the number of elements in
the Vector. To create a Vector with a certain number of elements, pass the number of elements as the first parameter
(the length parameter). Because Vector elements can’t be empty, the elements are filled with instances of the base
type. If the base type is a reference type that allows null values, the elements all contain null. Otherwise, the elements
all contain the default value for the class. For example, a uint variable can’t be null. Consequently, in the following
code listing the Vector named ages is created with seven elements, each containing the value 0:
var ages:Vector. = new Vector.(7);
trace(ages); // output: 0,0,0,0,0,0,0
Finally, using the Vector.() constructor you can also create a fixed-length Vector by passing true for the second
parameter (the fixed parameter). In that case the Vector is created with the specified number of elements and the
number of elements can’t be changed. Note, however, that you can still change the values of the elements of a fixedlength
Vector.
Last updated 6/6/2012
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