OOABAP Training Presentation

Copyright © 2009 Accenture All Rights Reserved.

Object Oriented ABAP


Course Contents

Object Oriented ConceptsObject Oriented Programming.Advantages of the Object-Oriented ApproachConcept of Inheritance

Day - 1

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

Day - 2

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


Day - 2

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


Day - 2

Course Contents

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


• ABAP created with intention of improving reporting.• Developed as an in-house programming language influenced by

COBOL and Pascal• Extended to ABAP/4 for ABAP Objects• OOC proved their worth for enterprise application in other

languages were adopted

History of ABAP


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

DataMethodMethod

Method

DataMethodMethod

MethodData

MethodMethodMethod

Boat

DataMethodMethodMethod


Object Oriented Programming

• Encapsulation

• Inheritance

• Polymorphism

• Instantiation

• Interfacing

• Events

OOPS


• Complex software systems become easier to understand, since an object-oriented architecture resembles reality more closely than other programming techniques.

• Changes in object-oriented systems should be possible locally (at class level), without further changes being necessary in other parts of the system. This reduces the amount of maintenance required.

Advantages


• Polymorphism and inheritance enable many individual components to be reused.

• Object-oriented systems require less adjustment and maintenance, because the majority of problems can be discovered and corrected in the design and development phases.

Advantages


• 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


• Attributes * Data * Determines state of the object• Methods * Executable code * Determine behavior of the object

Components in a class


Defining Local Classes• A complete class definition consists of a declaration part and 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


• Declare a class Private : name type string planetype type saplane-planetype private static attribute : n_o_planetypes type I Public : set_attributes – setting private attributes display_attributes – displaying pvt attributes display_n_o_airplane – display static attributes

Exercise 1


Creating Objects


• Define references of the class• Define several instances of the class• Gather all the references into internal table

Exercise 2


Calling method

Calling a method with an instance

CREATE OBJECT plane TYPE lcl_airplane.

CALL METHOD plane->set.

CALL METHOD plane->get IMPORTING get_value = number.

CALL METHOD plane->get EXPORTING get_value = number.

CALL METHOD plane->get CHANGING get_value = number.


Calling a static method

CREATE OBJECT plane TYPE lcl_airplane.

CALL METHOD lcl_airplane=>get_n_o_display.

Calling Method


• Call set_attributes by passing valid values• Call display_attributes• Call static method display_n_o_airplanes

Exercise 3


Constructor


Constructor : Example


Static Constructor : Implementation


Static Constructor : Call Examples


• Use constructor to count the instances created• Display the count

Exercise 4


Reference Variables


Creating Objects : Syntax


Assigning References


• Global classes are individual Repository objects with all of the normal attributes

• Namespace conventions are Y* or Z* is the same as that used for the namespace of other Repository objects.

• Special maintenance tool is available in the Workbench : class builder ( SE 24 )

Global classes


Class Builder


• Create a global class with name and planetype as two private attributes

• Write constructor to assign values• Write a method display_attributes to display both the values• Create an instance of this class and call the method with the

created instance

Exercise 5


• 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


A use of Aliases


• In class lcl_airplane define subclass lcl_passenger_plane• Attribute of subclass• max_seats type sflight-setsmax• Define constructor which define and implement all instance

attributes• Redefine display_attributes so that all instance attributes are

displayed using write statement

Exercise 6


• Define subclass lcl_cargo_plane• Attributes• Private max_cargo type scplane-cargomax• Define and implement constructor that assigns all instance

attributes• Redefine display_attributes to display all attributes• Define get_cargo to return cargo value to calling program. ( use

parameter re_cargo )

Cont …


• In main program • Define suitable type reference variable for each of your new

classes• Call method display_n_o_airplanes ( before instantiating any

objects )• Instantiate reference for lcl_passenger_plane and

lcl_cargo_plane• Call display attributes for both instance• Call static method display_attributes

Cont …


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


To understand Polymorphism

• In main program define an internal table which should have type reference to lcl_airplane

• Insert references to your passenger and cargo airplanes into internal table

• Loop through content of internal table and call display_attributes method every time in loop

Exercise 7


• 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


Events Overview


• Instance events can be triggered by the instances of the class• While developing the class that triggers the event, one need not know about

class handling • At the time of development it is completely unclear what type of handlers there

will be and how many will be used.

Events


• 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


Triggering and handling Events : Overview


Defining and Triggering Events


Handling and Registering Events


Handling Events


Registering for an Event : Syntax


Event handling : Characteristics


Thank You

Happy Coding

OOABAP Training Presentation

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