OOPS-ABAP

Hyderabad February 24-26th 2009

Instructor: Subhas Katikala.

Object Oriented ABAP

Workshop Goals

This workshop will enable you to:

• Learn object – oriented concepts.

• Learn the principle of object - oriented programming.

• Learn the application of object

- oriented ABAP.

Course Contents

Object Oriented ConceptsObject Oriented Programming.Advantages of the Object-Oriented Approach

Methods• Syntax and Visibility• Instance Methods and Static Methods• Constructor

Reference Variables• Creating References• Assigning References

ClassesComponents of a Class

Attributes• Syntax and Visibility• Instance Attributes and Static Attributes

Course Contents

Inheritance Super classes and Subclasses Visibility Inheritance and the (Instance) Constructor Parameters Redefining Methods in OOABAP Compatibility Principles of the Narrowing Cast Static and Dynamic Components Final Classes and Methods

Course Contents

Polymorphism Advantages Compared to Procedural Programming Abstract Classes and Methods Component Namespaces in Classes

Interfaces Defining and Implementing an Interface Working with Interface Components Interface References

• Narrowing Cast• Widening Cast

Using Several Interfaces Polymorphism and Interfaces Polymorphism and Inheritance Compound Interfaces

Course Contents

Events Define and Trigger Events Handle Events Register and deregister Events Receive a reference from Sender

Object – Oriented Concepts

What are Objects ?

SAP AG 1999

What Are Objects?

Tree

House

Crane

Objects are an abstraction of the real world

Objects are units made up of data and of the functions belonging to that data

Real worldModel

DataMethodMethodMethod

DataMethodMethodMethod

DataMethodMethodMethod

Boat

DataMethodMethodMethod

Object Oriented Programming

• Encapsulation

• Inheritance

• Polymorphism

• Instantiation

• Interfacing

• Events

OOPS

Advantages

• Simplicity

• Explicitness

• Maintainability

• Future Orientation

• Classes are the central element of object-orientation.

• A Class is an abstract description of an object.

• Classes are templates for objects.

• The attributes of objects are defined by the components of the class, which describe the state and behavior of objects.

Classes

• You define global classes and interfaces in the Class Builder (Transaction SE24) in the ABAP Workbench.

• They are stored centrally in class pools in the class library in the R/3 Repository.

• All of the ABAP programs in an R/3 System can access the global classes.

Classes

Components in a class

Defining Local Classes

• A complete class definition consists of a declaration part and, if required, an implementation part.

• The declaration part of a class <class> is a statement block: CLASS c1 DEFINITION.   ….  ENDCLASS.

• If you declare methods in the declaration part of a class, you must also write an implementation part for it.

CLASS c1 IMPLEMENTATION. ….   ENDCLASS. 

Classes

Attributes

Defining Local Classes

Classes

Attributes, Types, Constants - Syntax

Attributes and Visibility

Instance attributes and Static attributes

Methods

Methods : Syntax

Methods and Visibility

Instance methods and Static methods

Instance methods and Static methods : Example

Constructor

Constructor : Example

Static Constructor : Implementation

Static Constructor : Call Examples

Creating Objects

Reference Variables

Creating Objects : Syntax

Assigning References

• Inheritance allows you to derive a new class from an existing class. • You do this using the INHERITING FROM addition in the

CLASS <subclass> DEFINITION INHERITING FROM <superclass>

statement.• The new class <subclass> inherits all of the components of the existing

class <superclass>. • The new class is called the subclass of the class from which it is

derived. • The original class is called the superclass of the new class.

Inheritance

Inheritance

Inheritance : Syntax

Relationships between super classes and subclasses

Relationships between super classes and subclasses

Inheritance and Visibility

Inheritance and (Instance) constructor

Parameters and CREATE OBJECT

Redefining Methods in ABAP Objects

Redefining Methods : Example

Compatibility and Narrowing Cast

Principles of the Narrowing Cast

Static and Dynamic Types: Example

Static and Dynamic Types for References

Widening the Cast

Static and Dynamic Types for References

Widening the cast

Polymorphism

Polymorphism

Polymorphism

• Interfaces exclusively describe the external point of contact of a class, but they do not contain their own implementation part.

Interface

Defining and Implementing Interface

Working with Interface components

Interface References Narrowing casting

• The assignment of an object reference to an interface reference is known as a narrowing cast since, as with inheritance, only a part of the object interface is visible once you have assigned the reference.

• With an interface reference, you can no longer address all components in the class carrying out the implementation, but

only the components defined in the interface.

Interface

Interface references widening cast

• The widening cast is, as with inheritance, the opposite of the narrowing cast: here it is used to retrieve an object reference from an interface reference. Obviously it cannot be statically checked, since an interface can be implemented by more than one class.

• An object reference cannot be assigned to an interface reference if it has itself not implemented the corresponding interface.

Interface

• In the above example, one class is implementing several interfaces. Even if these interfaces contain components with the same name, they are differentiated in the class carrying out the

implementation by the prefix “<interfacename>~”.

Using several Interface

Polymorphism and Interface

• Objects or Classes use events to trigger Event Handler methods in other objects or classes.

• When an event is triggered any number of Event Handler Methods can be called.

• The events of a class can be raised in the same class using the RAISE EVENT Statement.

• Events have only output parameters which are accepted by the Event Handler Methods as input parameters.

• The link between the trigger and the handler is established dynamically at runtime using the statement SET HANDLER.

Events

Events Overview

Triggering and handling Events : Overview

Defining and Triggering Events

Handling and Registering Events

Handling Events

Registering for an Event : Syntax

Deregistration

Registration/Deregistration : Handler Table

Event handling : Characteristics

Events and Visibility