OOPS AT A GLANCE

Object orientation (OO), or to be more precise, object-oriented programming, is a problem-solving method in which the software solution reflects objects in the real world.

A comprehensive introduction to object orientation as a whole would go far beyond the limits of this introduction to ABAP Objects. This documentation introduces a selection of terms that are used universally in object orientation and also occur in ABAP Objects. In subsequent sections, it goes on to discuss in more detail how these terms are used in ABAP Objects. The end of this section contains a list of further reading, with a selection of titles about object orientation.

Objects

An object is a section of source code that contains data and provides services. The data forms the attributes of the object. The services are known as methods (also known as operations or functions). Typically, methods operate on private data (the attributes, or state of the object), which is only visible to the methods of the object. Thus the attributes of an object cannot be changed directly by the user, but only by the methods of the object. This guarantees the internal consistency of the object.

Classes

Classes describe objects. From a technical point of view, objects are runtime instances of a class. In theory, you can create any number of objects based on a single class. Each instance (object) of a class has a unique identity and its own set of values for its attributes.

Object References

In a program, you identify and address objects using unique object references. Object references allow you to access the attributes and methods of an object.

In object-oriented programming, objects usually have the following properties:

Encapsulation

Objects restrict the visibility of their resources (attributes and methods) to other users. Every object has an interface, which determines how other objects can interact with it. The implementation of the object is encapsulated, that is, invisible outside the object itself.

Polymorphism

Identical (identically-named) methods behave differently in different classes. Object-oriented programming contains constructions called interfaces. They enable you to address methods with the same name in different objects. Although the form of address is always the same, the implementation of the method is specific to a particular class.

Inheritance

You can use an existing class to derive a new class. Derived classes inherit the data and methods of the superclass. However, they can overwrite existing methods, and also add new ones.

Uses of Object Orientation

Below are some of the advantages of object-oriented programming:

Complex software systems become easier to understand, since object-oriented structuring provides a closer representation of reality than other programming techniques.
In a well-designed object-oriented system, it should be possible to implement changes at class level, without having to make alterations at other points in the system. This reduces the overall amount of maintenance required.
Through polymorphism and inheritance, object-oriented programming allows you to reuse individual components.
In an object-oriented system, the amount of work involved in revising and maintaining the system is reduced, since many problems can be detected and corrected in the design phase.