ActionScript 3.0 Design Patterns

Chapter 2. Factory Method Pattern

As experimentation becomes more complex, the need for the cooperation in it of technical elements from outside becomes greater and the modern laboratory tends increasingly to resemble the factory and to employ in its service increasing numbers of purely routine workers.

—John Desmond Bernal

The medieval university looked backwards; it professed to be a storehouse of old knowledge. The modern university looks forward, and is a factory of new knowledge.

—Thomas Huxley

One cannot walk through an assembly factory and not feel that one is in Hell.

—W. H. Auden

What is the Factory Method Pattern?

One of the most common statements in object-oriented programming (OOP) uses the new keyword to instantiate objects from concrete classes. ActionScript applications that have multiple classes can have an abundance of code that looks like the following:

public class Client
{
    public function doSomething()
    {
        var object:Object = new Product();
        object.manipulate();
    }
}

The Client class creates a new instance of the Product class and assigns it to the variable object. There’s nothing wrong with this code, but it does create a coupling or dependency between the Client and Product classes. Simply put, the Client class depends on the Product class to function properly. Any changes to the Product class in terms of class name changes or change in the number of parameters passed to it will require changes in the Client class as well. This situation is exacerbated if multiple clients ...