In simple terms, polymorphism is the ability of one type, A, to appear as and be used like another type, B. In strongly typed languages, this usually means that type A somehow derives from type B, or type A implements an interface that represents type B. In non-strongly typed languages (dynamically typed languages) types are implicitly polymorphic to the extent they have similar features (fields, methods, operators). In fact, this is one of the principal benefits of dynamic typing. – Wikipedia
Polymorphism is tightly coupled to the inheritance and is often considered to be one of the most powerful feature of the object oriented programming. It can be defined as a term according to which a name (variable declaration) may denote objects of many different classes that are related by some common suprclass; thus, any object denoted by this name is able to respond to some common set of operations in different ways. – Grady Booch

Lets consider an example:
There are two array of shapes called Rectangle and Circle. Even though we treat both these as a Shape but their implementation is quite different. In nutshell, each class is able to respond differently to the same method getArea(). This is called Polymorphism.

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This is my first attempt to try to understand and implement patterns and practices. It is necessary to understand and implement these design patterns in order to make code flexible, re-usable, highly cohesive and less coupled.

In software engineering, a design pattern is a general reusable solution to a commonly occurring problem in software design. A design pattern is not a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations. Object-oriented design patterns typically show relationships and interactions between classes or objects, without specifying the final application classes or objects that are involved. Algorithms are not thought of as design patterns, since they solve computational problems rather than design problems. – Wikipedia

http://en.wikipedia.org/wiki/Design_pattern_(computer_science)

As this is my first post regarding patterns and practices, I want to express something that I have learnt about Factory Method Pattern. It is a part of Gang-of-Four (GoF) design patterns.

The Factory Method pattern is a way of creating objects, but letting subclasses decide exactly which class to instantiate. Various subclasses might implement the interface; the Factory Method instantiates the appropriate subclass based on information supplied by the client or extracted from the current state. This pattern enables to make decision about which concrete class to be instantiatedin the run-time.

Lets go thru an example:

There is an interface called IPerson and two implemented class named Student and Programmer. The class called PersonFactory is created to make run-time decision about the selection of Student or Programmer thru a static method named GetWorkDone.

UML Diagram


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