What are dyanmic classes in ActionScript

What are Dynamic classes in Actionscript?

Basically same idea as in perl where an object is a hash, where keys are the names of properties, and the values are the field values, or function pointers.

More memory overhead than sealed classes.

More info:

http://flexblog.faratasystems.com/2006/10/02/actionscript-3-dynamic-classes - you can dynamically add only public properties and methods. Of course, nothing comes for free and sealed classes are a bit more efficient in terms of memory consumption, because they do not need to create a hash table to store the properties and methods that are unknown during compilation. Another obvious restriction is that dynamically added functions can’t access private members of the dynamic class.

Examples:

dynamic class Person {
var name:String;
}

Now let’s add dynamically two variables name and age and the function printme() to the object of type Person:

Person p= new Person();
p.name=”Joe”;
p.age=25;
p.printMe = function () {
trace (p.name, p.age);
}
p.printMe(); // Joe 25

In AS3, any function can be attached to a dynamically created property of a dynamic object, for example

function calcTax():Number {…}

var myObject:SomeObject = new SomeObject();
myObject.tax=calcTax; //add the tax property and attach the function calcTax()
var myTax=myObject.tax();

The delete operator destroys the property of an object and makes it eligible for garbage collection:

delete calcTax();
myTax=myObject.tax() // generates an error

Adobe Help for AS 3.0 - Dynamic Classes

Example of adding function to a dynamic class

myProtean.traceProtean = function () 
{ 
    trace(myProtean.privateGreeting); // undefined 
    trace(myProtean.publicGreeting); // hello 
}; 
myProtean.traceProtean();