Factory Pattern

• Resource: http://www.patterndepot.com/put/8/factory.pdf
• The factory pattern returns an instance of an object based on the parameters passed to it.
• It can return any one of a number of objects, as long as all objects it can return either implement or extend the return type of the factory method itself.
• If this were not the case, the method simply would not work, because it can only return objects of the same type of the declared return type.
• We know that, with polymorphism, you can actually return a subclass when the superclass is the declared return type.
• What you need...
• Classes that the factory method can instantiate.
• A superclass that the classes (above) extend.  Or, an interface that they implement.
• A factory class with a method that takes a parameter and has the logic necessary to determine which class to return.
• A slight variation of the Factory Pattern - class NumberFormat.
• How could this be redesigned to be a factory pattern, according to the patterndepot definition?
• What are advantages/disadvantages of this method?
 Factory Example... it's a toughy!

 Singleton Pattern

Created by:  Brandan Jones December 17, 2001