Macromedia flex 2 Manual

30

Using ActionScript to Create Components

Defining properties as variables 

Properties let you define data storage within your class. You can define your properties as 
public, which means that they can be accessed by users of the class. You can also define 
properties as private, which means that they are used internally by the class, as the following 
example shows:

public class MyButton extends Button {

// Define private vars.
private var currentFontSize:Number;

// Define public vars. 
public var maxFontSize:Number = 15;
public var minFontSize:Number = 5;

}

Users of the class can access the public variables but not the private variables, as the following 
example shows:

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" 

xmlns:MyComp="myControls.*">

</mx:Application>

Although you can define your classes to use public properties, you may find it advantageous to 
define properties by using setter and getter methods. For more information, see 

Defining properties as getters and setters

You can define properties for your components by using setter and getter methods. The 
advantage of getters and setters is that they isolate the variable from direct public access so that 
you can perform the following actions:

■

Inspect and validate any data written to the property on a write

■

Trigger events that are associated with the property when the property changes

■

Calculate a return value on a read

■

Allow a child class to override

NO

T

E

You cannot override an inherited property defined by a variable, but you can override a 
property defined by setter and getter methods. You can reset the value of an inherited 
property defined by a variable. You typically reset it in the constructor of the subclass for 
an ActionScript component, or in an event handler for an MXML component because 
MXML components cannot define a constructor.