RE:ABAP objects

[alex_georgek]

Hi,

Can any one explain with a simple example what you mean by

class,subclass,superclass...

Thanks & regards,

Alex.

[matt]

If A is a subclass of B, then B is the superclass of A.

A class is an encapsulation of a concept, perhaps some physical object like a vehicle, or a business object like a purchase order, or something more abstract like BW start routine. A subclass is more specific than its superclass. A superclass is more general than its subclasses. ( In ABAP a class can have up to one superclass, though type OBJECT can be considered a superclass of all classes, except itself ).

For example, you may have a class representing VEHICLES. It could have two subclasses CAR and BICYCLE. ( So VEHICLES would be the superclass of both CAR and BICYCLE ). The class VEHICLES would have all the attributes and methods that apply to all kinds of vehicles - e.g. "source of power". The CAR class would inherit all the VEHICLE attributes and methods, and have additional methods and attributes applicable only to cars - e.g. "number of doors". Similarly for the BICYCLE, you might have "pedal_type". Both CAR and BICYCLE would have "source of power", as they've inherited this from VEHICLES.

matt

[Former Member]

hi,

That is the concept called Inheritence in OO Programming.

INHERITANCE

Inheritance is an implementation relationship between classes that allows a class, called a subclass, to inherit all components of another class, called a superclass. In ABAP Objects, adding INHERITING FROM to the class definition statement enables inheritance .

In a subclass you define additional components or redefine instance methods that were inherited from the superclass, but you can't remove inherited components. Therefore, a subclass is strongly coupled to its superclass just by containing all of the superclass's components. While a subclass knows its superclass, a superclass has no knowledge of its subclasses. Nevertheless, the semantic coupling is strong in both directions because changing a superclass automatically changes or even invalidates all of its subclasses.

While a subclass specializes a superclass by adding components or redefining methods, a superclass is a generalization of its subclasses. In fact, inheritance should be used to implement relationships between classes that can be described in terms of generalization and specialization. For example, if you compare a passenger_airplane class to a cargo_airplane class, you will find that many common features can be put into a general superclass, airplane.

Hope you got something out of the explaination.

regards,

theja

[Former Member]

Hai.

check the links.

http://help.sap.com/saphelp_nw70/helpdata/en/dd/4049c40f4611d3b9380000e8353423/content.htm

http://help.sap.com/saphelp_nw70/helpdata/en/1d/df5f54127111d3b9390000e8353423/content.htm

http://java.sun.com/docs/books/jls/second_edition/html/classes.doc.html

http://abapprogramming.blogspot.com/2007/10/oops-abap-15.html

regards.

sowjanya.b

[Former Member]

Hi Alex,

just go through this link,

http://www.erpgenie.com/abap/OO/index.htm

Hope this helps.