Saturday, June 23
Introduction to Object Orientation
Software systems are defined by data
and functionality. In a non object oriented system, functionality and data and
treated separately. The focus in such a system remains on functionality. On the
other hand, object oriented systems data and functionality are combined
together using objects. Objects are concrete representation of real world
things. So in a object oriented systems, developer need to map real world
things with software objects and they need to define functions a of each object
in such a manner that it reflects its behavior in the real world.
Typical objects in a SAP software
system can be Invoice, Customer, order etc. It is not possible to introduce
Object orientation with this small article.
Objects
Objects are formed out of classes.
Class is the structure of object. For example, cuckoo belongs to the bird
class, Amazon belongs to the river class. Objects have attributes (also called
its characteristics) and functions or services. The services of an object work
upon the attributes of the object to change the value of attributes. Attributes
and services can be private, public or protected.
Classes
As already described, classes are
structure of objects. Any number of objects can be formed out of a class. Each object has its own values of
its attributes.
Object
References
Object references are not the real
objects but their references. So you can very well access data and services of
object using its reference.
Abstraction
The implementation of objects is not
visible to the users. Users see only the data and services of the object. But
how the services manipulate the data is unknown to the user of the object, such
feature is called encapsulation. For example : Tata innova and Maruti are
objects of the car class and Average is a service of car class. Average returns
different value for both these objects. But how it calculates the average of
the car if unknown. User only knows the name of the service, the data it takes
and the result it gives.
Inheritance
New classes can be formed from
existing classes. This feature of object orientation is called inheritance. The
new class thus formed is called derived class. Derived class has data and
functions of the parent class. But it can overwrite data and functions of the
parent class.
Polymorphism
In ABAP Objects, polymorphism is
implemented by redefining methods during inheritance and by using
constructs called interfaces. Identical methods behave differently in
different classes. Polymorphism means same method behaves differently in different classes.
Polymorphism is a great feature of Object oriented technology. Code written using polymorphism is easy to maintain. With polymorphism, the developer writes a general interface and not a concrete implementation. Change in the requirement of the client can be handled very easily if the program developed has polymorphism feature in it.
Polymorphism is a great feature of Object oriented technology. Code written using polymorphism is easy to maintain. With polymorphism, the developer writes a general interface and not a concrete implementation. Change in the requirement of the client can be handled very easily if the program developed has polymorphism feature in it.
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