Programming Flex 3

Variables and Properties

A variable is a named element you can use to store data or a reference to data. You can assign values to and read values from a variable.

When you want to work with a variable, the first thing you’ll need to do is declare it. Declaring a variable allocates memory for it and tells the application that the variable exists. You can declare a variable using the var keyword as follows:

var variableName;

The var keyword is followed by the name of the variable. Variable names in ActionScript are arbitrary, but they must follow a few simple rules:

• The variable name can consist only of letters, numbers, dollar signs, and underscores.

• The variable name must not start with a number.

By convention, all ActionScript variables use initial lowercase letters rather than initial uppercase letters. The following declares a variable called userName:

var userName;

Although you can declare a variable without a data type, it’s always recommended that you declare a variable with a data type. You can add a data type to the variable declaration using post-colon syntax as follows:

var variableName:DataType;

Note

If you declare a variable without a data type, Flash Player allows any data to be assigned to the variable regardless of the type. The result is that there is no runtime type-checking for the variable, and there is no compile-time or runtime optimization because the type is not known ahead of time.

The data type determines the kind of data you can store in the variable. There are many ...