User Guide

Variables 51

Variables

Variables allow you to store values that you use in your program. To declare a variable, you

must use the

var statement with the variable name. In ActionScript 2.0, use of the var

statement is only required if you use type annotations. In ActionScript 3.0, use of the

var

statement is always required. For example, the following line of ActionScript declares a

variable named

var i;

If you omit the var statement when declaring a variable, you will get a compiler error in strict

mode and run-time error in standard mode. For example, the following line of code will result

in an error if the variable

i has not been previously defined:

i; // error if i was not previously defined

To associate a variable with a data type, you must do so when you declare the variable.

Declaring a variable without designating the variable’s type is legal, but will generate a

compiler warning in strict mode. You designate a variable’s type by appending the variable

name with a colon (:), followed by the variable’s type. For example, the following code

declares a variable

i that is of type int:

var i:int;

You can assign a value to a variable using the assignment operator (=). For example, the

following code declares a variable

i and assigns the value 20 to it:

var i:int;

i = 20;

You may find it more convenient to assign a value to a variable at the same time that you

declare the variable, as in the following example:

var i:int = 20;

The technique of assigning a value to a variable at the time it is declared is commonly used

not only when assigning primitive values such as integers and strings, but also when creating

an array or instantiating an instance of a class. The following example shows an array that is

declared and assigned a value using one line of code.

var numArray:Array = ["zero", "one", "two"];

You can create an instance of a class by using the new operator. The following example creates

an instance of a named

CustomClass, and assigns a reference to the newly created class

instance to the variable named

customItem:

var customItem:CustomClass = new CustomClass();