MACROMEDIA FLASH MX 2004 - ACTIONSCRIPT Reference Manual page 164

If no constructor function is explicitly declared—that is, if you don't create a function whose
name matches that of the class—the compiler automatically creates an empty constructor
function for you.
A class can contain only one constructor function; overloaded constructor functions are not
allowed in ActionScript 2.0.
Controlling member access
By default, any property or method of a class can be accessed by any other class: all members of a
class are public by default. However, in some cases you may want to protect data or methods of a
class from access by other classes. You'll need to make those members private—available only to
the class that declares or defines them.
You specify public or private members using the
example, the following code declares a private variable (a property) and a private method
(a function).
For example, the following class (LoginClass) defines a private property named
private method named
class LoginClass {
private var userName:String;
private function getUserName() {
return userName;
}
// Constructor:
function LoginClass(user:String) {
this.userName = user;
}
}
Private members (properties and methods) are accessible only to the class that defines those
members and to subclasses of that original class. Instances of the original class, or instances of
subclasses of that class, cannot access privately declared properties and methods; that is, private
members are accessible only within class definitions; not at the instance level.
For example, you could create a subclass of LoginClass called NewLoginClass. This subclass can
access the private property (
class NewLoginClass extends LoginClass {
// can access userName and getUserName()
}
However, an instance of LoginClass or NewLoginClass cannot access those private members. For
example, the following code, added to a frame script in a FLA file, would result in a compiler
error indicating that
var loginObject:LoginClass = new LoginClass("Maxwell");
var user = loginObject.getUserName();
Also note that member access control is a compile-time only feature; at runtime, Flash Player does
not distinguish between private or public members.
164 Chapter 9: Creating Classes with ActionScript 2.0
.
getUserName()
) and method (
userName
is private and can't be accessed.
getUserName()
or member attribute. For
public private
) defined by LoginClass.
getUserName()
and a
userName