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Hyderabad February 24-26th 2006
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