Friday, 22 December 2006

OOP Classes and Inheritance

A Class is a user defined reference type that encapsulates data and is controlled through programming constructs called Properties, Constructors, Methods and Events. The Class encapsulates data such as Constants and Fields.

To work with a Class you create an *Instance* of a Class called an *Object*. An Object can be thought of as a ‘live’, ‘active’ version of a Class. A Class can effectively be thought of as the blueprint of an Object.

Generally you work with members of the Object, Methods, Events etc. you can however work with some members of the Class itself, these are called Static Members.

From the one Class many Objects can be created, each is totally self contained and has it’s own values. The members of an object are:

The members are stored on the *Heap* and a pointer within the Object contains a *Reference* ,the memory location of that particular piece of data.

Inheritance allows you to create a new Class using an existing Class as a template. The inherited Class is called the Derived Class and the original Class is called the Base Class. The Derived Class can then be extended to include additional functionality that was not available within the Base Class.

Inheritance is one of the cornerstones of Object Oriented Programming.

"The shoe that fits one person pinches another; there is no recipe for living that suits all cases." - Carl Jung

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