CSC/ECE 517 Fall 2012/ch2b 2w60 ns
Factory Method
General Resources
Overview of the Pattern
Factory method pattern is an Object Oriented Programming concept in which objects can be created without specifying the class to which they belong.Factory method pattern implement the concept of using an object to generate other objects.<ref name="web">http://www.oodesign.com/factory-pattern.html
</ref>Factory method is thus a type of creational pattern. An interface is defined for object creation. However the subclasses decide which class they want to instantiate. Factory methods thus abstract object instantiation from the client.<ref name="userpagesfactory">http://userpages.umbc.edu/~tarr/dp/lectures/Factory.pdf
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Wikipedia<ref name="wikipedia">http://en.wikipedia.org/wiki/Factory_method_pattern</ref> and dofactory<ref name="dofactory">http://www.dofactory.com/Patterns/PatternFactory.aspx#UML</ref> provide good explanations of the Factory Method Pattern. dofactory<ref name="dofactory"/> is much more concise than Wikipedia<ref name="wikipedia"/>. It is a good resource for quickly viewing the definition and participants of the pattern. Wikipedia<ref name="wikipedia"/>, on the other hand, is much more verbose, but goes into the motivation for the pattern and discusses use of the patterns in several languages at a high level.
If you understand Java (or a Java like language), javapapers<ref name="javapapers">http://javapapers.com/design-patterns/decorator-pattern/ - 2011</ref> is a good page that gives a basic overview of the pattern through the presentation of a concrete example. There are other Java resources and resources for other languages that are similar below.
UML
Understand the UML diagram for the Decorator pattern can help you understand the purpose of the Decorator pattern, the classes involved and how they interact with each other. UML is not programming language specific, so you should be able look at the UML diagram in any of the resources that have them on this page, regardless of what languages you know.