chapter 02_abap objects - advanced

8/3/2019 Chapter 02_ABAP Objects - Advanced

http://slidepdf.com/reader/full/chapter-02abap-objects-advanced 1/55

© Copyright IBM Corporation 2007

IBM Global Business Services

ABAP Objects - Advanced



IBM Global Services

© 2007 IBM Corporation2 Jan-2007ABAP Objects - Advanced

Objectives

The participants will be able to : Define Inheritance

Interpret Interfaces

Interpret Friends

Define and trigger Events

Handle Events

Register Events

Describe the runtime environment for Event processing

Define Global classes and interfaces



IBM Global Services


ABAP Objects Advanced : Inheritance Topics

Concept

Syntax and Visibility

Abstract Classes and Methods

Final Classes and Methods

Static Components in Inheritance

Method Redefinition

Constructor in Inheritance

Object References in Inheritance

Polymorphism through Inheritance



IBM Global Services


Inheritance : Concept

Inheritance is one of the most powerful feature of object oriented programming.

Inheritance is the process of creating new classes, called derived classes or SubClasses or child classes from existing classes called base classes or SuperClasses or parent classes.

The derived class inherits all the capabilities of the base class but can add

embellishments and refinements of its own. The base class is unchanged by thisprocess.

Grand Parent Class

Parent Class

Child Class

Single Inheritance supported

by ABAP Objects

Parent Class Parent Class

Child Class

Multiple Inheritance not

supported by ABAP

Objects



IBM Global Services


Inheritance : Concept (Contd.)

The relationship between thebase classes and the derivedclasses can be represented in anInheritance tree. Where baseclasses of each derived class can

be retraced along an unique pathto a single root node of the tree.

A Super Class is a Generalizationof its Sub Classes and on theother hand a Sub Class is aSpecialization of its Super Class.

Super Class

Public:

Protected:

Private:

Class C1

Public:

Protected:

Private:

Class C2

Public:

Protected:

Private:

Class C3

Root node

Generalized

Class

Specialized

Class

More specialized class

G e n e r a l i z a t i o n

S p e c i a l i z a t

i o n “IS A”

Relationship



IBM Global Services


Inheritance: Advantages

Inheritance permits code Reusability. Reusing existing code removes coderedundancy and saves time & money.

Common components exist only in the Super Class and maintained Centrally.

Once a base class is written and tested, it need not be touched again. Thisincreases program Reliability.



IBM Global Services


Inheritance : Syntax and Visibility

CLASS super_class DEFINITION.

PUBLIC SECTION.

Public components

PROTECTED SECTION.

Protected components

PRIVATE SECTION.

Private components

ENDCLASS.

CLASS sub_class DEFINITION INHERITING FROMsuper_class.

PUBLIC SECTION.

Public components

Public components(super_class)

PROTECTED SECTION.

Protected components

Protected components(super_class)

PRIVATE SECTION.

Private section

ENDCLASS.

The public and protectedcomponents of the Super Class arevisible in the Sub Class.

Private section of the Super Class isnot visible in the Sub Classes.

Private components of the SubClass can have same name as theprivate component of the SuperClass.

Public and Protected components of

the Sub Class can not have thesame name as that have been usedin Super Class.



IBM Global Services


Inheritance : Abstract classes and methods

CLASS cl_super DEFINITION.

PUBLIC SECTION.

METHODS: demo1 ABSTRACT,

demo2.ENDCLASS.

CLASS cl_sub DEFINITIONINHERITING FROM cl_super.

PUBLIC SECTION.

METHODS demo1 REDEFINITION.

ENDCLASS.

A class defined as ABSTRACT cannot beinstantiated , that is one cannot use CREATEOBJECT with reference to the class.

Abstract class can only be accessed using itsstatic components or its Sub Classes.

Abstract class serves as a template for SubClasses

If a class contains any abstract method thewhole class becomes abstract.

A method, which is abstract, should be

redefined in derived class. An Abstract class can declare and implement

non abstract methods which its Sub Classescan use with or without redefining them.

Redefining the Abstract method of

Super class in the Sub class

Abstract method



IBM Global Services


Inheritance : Final classes and methods

A final class can not be inherited further.

All Methods of a final class areinherently final and must not bedeclared as final in the class

definition. A final method can not be redefined

further.

If a method of a non-final class is finalthen that class can be inherited but

that method cannot be redefined.

CLASS final_class DEFINITION FINAL.. . . . . . . .

ENDCLASS.

CLASS derived_class DEFINITION INHERITINGFROM final_class .

. .. . . . . . . .

ENDCLASS.

CLASS super_class DEFINITION .

. . . . . . . .

METHODS final_method FINAL.

ENDCLASS.

CLASS sub_class DEFINITION INHERITINGFROM super_class .

. .. . . . . . . .

METHODS final_method redefinition.

ENDCLASS.



IBM Global Services


Inheritance : Static components

The public and protected staticcomponents (methods + attributes) ofthe Super Class are visible in the SubClass.

Public static components can be

accessed through the classcomponent selector used with anyclass in the respective path ofinheritance tree.

CLASS base_class DEFINITION.PUBLIC SECTION.

CLASS-DATA : name TYPE STRING

VALUE „ABAP‟.

………..

ENDCLASS.CLASS derived_class DEFINITIONINHERITING FROM base_class.

. .. . . . . . . .

ENDCLASS.

START-OF-SELECTION.

base_class=>name.

derived_class=>name.

Static component

Static component is accessedthrough class component

selector from the derived class

as well as from the base class



IBM Global Services


Inheritance : Method Redefinition

Redefinition is when theimplementation of an inheritedinstance method is changed for thesub class without changing itssignature.

Static methods cant be redefined.

The parameters remain same in thederived class as it was in base class.

In the redefined method use theSUPER pseudo reference to accessthe original method of the base class.

CLASS base_class DEFINITION.PUBLIC SECTION.

METHODS: meth.

. . . . . . . .

ENDCLASS.

CLASS derived_class DEFINITION INHERITING

FROM base_class .PUBLIC SECTION.

METHODS: meth REDEFINITION.

. .. . . . . . . .

ENDCLASS.

CLASS derived_class IMPLEMENTATION .

METHODS meth.

CLASS METHOD SUPER->meth.

………

ENDMETHOD.

ENDCLASS.

Redefining the base class method in the

derived class

Calling the Super Class method using

SUPER keyword



IBM Global Services


Inheritance : Instance Constructors

As all public and protectedcomponents, Sub Class inherits theconstructor method if it is present inthe inheritance tree.

If an object of Sub Class is createdat this time the inherited instanceattributes and private attributes ofthe Super Classes must also beinitialized.

As the private attributes of theSuper Class is not visible to Sub

Class, Sub Class cannot fullyinitialize its Super Class. Thereforeto ensure complete initialization ofSub Class and its Super Classes,constructor is redefined.

CLASS base_class DEFINITION.

PUBLIC SECTION.

METHODS: constructor IMPORTING arg1 TYPE STRING.

PRIVATE SECTION.

DATA: fld TYPE STRING.

. . . . . . . .

ENDCLASS.

CLASS derived_class DEFINITION INHERITING FROMbase_class .

PUBLIC SECTION.METHODS: constructor IMPORTING arg1 TYPE STRING

arg2 TYPE STRING.

PRIVATE SECTION.


. . . . . . . .

ENDCLASS.

CLASS derived_class IMPLEMENTATION .METHODS constructor.

CALL METHOD SUPER->constructor

EXPORTING arg1 = arg1.

fld = arg2 .

………

ENDMETHOD.

ENDCLASS.

Super class constructor

Sub class constructor

Calling Super Class

constructor



IBM Global Services


Inheritance : Instance Constructors (Contd.)

Whether explicit call is required for the instance constructor of the Super Class ornot , when we instantiate an object of Sub Class is depends on the followingconditions:

Explicit constructor isdefined in Superclass?

Explicit constructor isdefined in Sub class?

Explicit call required?

No No No

Yes No No

No Yes Yes

Yes Yes Yes



IBM Global Services


Inheritance : Static Constructors

The redefinition of static constructorworks similarly to instanceconstructor.

When an static constructor isredefined then REDEFINITION

addition is not required. No parameter interface is possible for

static constructor ( with or withoutinheritance)

The runtime environmentautomatically ensures that the staticconstructors are called in the rightorder, so it is not required to call thestatic constructor of the Super Classexplicitly.

CLASS base_class DEFINITION.

PUBLIC SECTION.METHODS: class_constructor.

PRIVATE SECTION.


. . . . . . . .

ENDCLASS.

CLASS derived_class DEFINITION

INHERITING FROM base_class .PUBLIC SECTION.

METHODS: class_constructor .

PRIVATE SECTION.


. . . . . . . .

ENDCLASS.

CLASS derived_class IMPLEMENTATION .

METHODS class_constructor.

fld = „ I am sub‟ .

………

ENDMETHOD.

ENDCLASS.

Super class constructor

Sub class constructor

No call for Super Class

constructor



IBM Global Services


Inheritance : Object References

Pub: a1, a2

Prot: b1, b2

Priv:c1,c2

Class C1

Pub: a1, a2,a3,a4

Prot: b1,b2,b3,b4

Priv: c3,c4

Class C2 Inheriting from C1

Pub: a1, a2,a3,a4,a5,a6

Prot: b1, b2,b3,b4,b5,b6

Priv:c5,c6

DATA oref TYPE REF TO C1.

CREATE OBJECT oref.


CREATE OBJECT oref.


CREATE OBJECT oref.




IBM Global Services


Inheritance : Object References (Contd.)

DATA : oref1 TYPE REF TO C1,oref3 TYPE REF TO C3.

CREATE OBJECT oref3.

oref1 = oref3.

oref1 ->a1.

oref1 ->a5.

OK

Error

Pub: a1, a2

Prot: b1, b2

Priv:c1,c2

Class C1

Pub: a1, a2,a3,a4

Prot: b1,b2,b3,b4

Priv: c3,c4


Pub: a1, a2,a3,a4,a5,a6


Priv:c5,c6




IBM Global Services



DATA : oref1 TYPE REF TO C1,oref3 TYPE REF TO C3.

CREATE OBJECT oref1 TYPE C3.

CREATE OBJECT oref3.

oref1 = oref3.

oref1 ->a1.

oref1 ->a5.

OK

OK

Pub: a1, a2

Prot: b1, b2

Priv:c1,c2

Class C1

Pub: a1, a2,a3,a4

Prot: b1,b2,b3,b4

Priv: c3,c4


Pub: a1, a2,a3,a4,a5,a6


Priv:c5,c6




IBM Global Services



DATA : oref1 TYPE REF TO object,oref2 TYPE REF TO class.

…

oref1 = oref2.

oref2 = oref1.

oref2 ?= oref1.

CATCH SYSTEM-EXCEPTIONS

MOVE_CAST_ERROR = 4.oref2 = oref1.

ENDCATCH.

In assignments of reference variables ,static type of a reference variable isalways more general than the dynamictype.

When static type of the target variable

is more general than the static type ofthe source variable, since the dynamictype of the source variable at run timecan only be more specialized than itsstatic type, this can be checked duringthe syntax check. This is known as

narrowing cast. When static type of the target variable

is more specialized than the static typeof the source variable. This is knownas widening cast.

Narrowing Cast

Syntax error

occurred

Widening Cast

IBM Gl b l S i



IBM Global Services


Inheritance : Polymorphism

CLASS super_class DEFINITION.

. . . . . . . . . .METHODS test_method.

ENDCLASS.

CLASS sub_class_one DEFINITION INHERITINGFROM super_class.

. . . . . . . . .

METHODS test_method REDEFINTION.

ENDCLASS.

CLASS sub_class_two DEFINITION INHERITINGFROM super_class.

. . . . . . . . .

METHODS test_method REDEFINTION.

ENDCLASS.

DATA: supr_obj type ref to super_class,

sub1_obj type ref to sub_class_one,

sub2_obj type ref to sub_class_two.

START-OF-SELECTION.

CREATE OBJECT sub1_obj.

CREATE OBJECT sub2_obj.

supr_obj = sub1_obj.

CALL METHOD supr_obj->test_method.

supr_obj = sub2_obj.

CALL METHOD supr_obj->test_method.

Reference variables declared with staticreference to a Super Class candynamically point to an object of a SubClass of this Super Class and access thecomponents known to the Super Class.

Methods inherited from Super Class maybe redefined in one or more of the SubClasses. This is the basis ofpolymorphism using inheritance.

Polymorphism here means using thesame name via same interface to

address differently implementedmethods, belonging to different objectsof different classes in the inheritancetree.

IBM Gl b l S i



IBM Global Services


Demonstration

Showing how Inheritance works with ABAP object.

IBM Gl b l S i



IBM Global Services


Practice

Showing how Inheritance works with ABAP object.

IBM Gl b l S i



IBM Global Services


ABAP Objects Advanced : Interface Topics

Concept Defining Interfaces

Implementing Interface in Classes

Compound Interfaces

Alias Names

Interface References

Polymorphism through interfaces

Interface and Inheritance

IBM Global Ser ices



IBM Global Services


Interfaces : Concepts

Like Java, ABAP Objects does notpermit multiple inheritance, but usinginterfaces with inheritance we canachieve the same.

Interface is similar to abstract classbut it has only definitions part.

The interface can be implementedonly in the class that uses it.

Interface, which is an independentstructure, is used to implement in aclass to extend the scope of a class.

Interface allows users to addressdifferent classes via a universalpoint of contact.

Public:

Interfaces I1

Class C1

Public:

Interfaces I1

Class C2

DATA:

CLASS-DATA:

METHODS:

CLASS-METHODS:

EVENTS:

CLASS-EVENTS:

Interface I1

Public:

Interfaces I1

Class C3

IBM Global Services



IBM Global Services


Interfaces : Defining Interfaces

INTERFACE I1

DATA:

CLASS-DATA:

METHODS:

CLASS-METHODS:

EVENTS:

CLASS-EVENTS:

ENDINTERFACE

INTERFACE I2.

DATA : name(20).

METHODS: I_method1,

I_method2.

ENDINTERFACE.

Interfaces are defines as independentconstruct, in an INTERFACE….

ENDINTERFACE block similar to thedeclaration block of classes.

An interface can declare instance aswell as static components like

classes.

Interface components are alwaysPUBLIC, so visibility is not explicitlydefined.

Interface define the methods but do

not Implement them. Similarly howSub Classes implement the methodsof an abstract class, all classes thatwish to use an interface mustimplement all of its methods.

IBM Global Services



IBM Global Services


Interfaces : Implementing Interface in Classes

INTERFACE my_interface .

METHODS my_interface_method.ENDINTERFACE.

CLASS interface_class DEFINITION.

PUBLIC SECTION.

INTERFACES my_interface.

ENDCLASS.

CLASS interface_classIMPLEMENTATION.

METHOD

my_interface~my_interface_method.DATA: num TYPE I VALUE 10.

Write:/ num.

ENDMETHOD.

ENDCLASS.

Each class can implement one ormore interfaces.

Interfaces expand public visibilitysection of the class definition.

The class must implement all themethods of each incorporatedinterface.

Multiple classes can implement thesame interface.

With in the class each component ofthe interface is identified by the name

intf~comp.so identically namecomponets of different interface do noconflict when implemented in thesame class. “~” is called interface

component selector.

IBM Global Services



IBM Global Services


Interfaces : Defining and Implementing Compound Interfaces

INTERFACE I1 .

METHODS meth.ENDINTERFACE.

INTERFACE I2 .

METHODS meth.

INTERFACES I1.

ENDINTERFACE.

CLASS interface_class DEFINITION.

PUBLIC SECTION.

INTERFACES: I2.

ENDCLASS.

CLASS interface_class IMPLEMENTATION.

METHOD I1~meth.

….

ENDMETHOD.METHOD I2~meth.

….

ENDMETHOD.

ENDCLASS.

A new interface can be created fromseveral existing interface. Such aninterface is called a compoundinterface. An interface which iscontained in another interface iscalled component interface.

In a compound interface there is nocomponent hierarchy. All componentinterfaces are on the same level. So itis not possible to chain names suchas I2~I1.

A compound interface contains eachcomponent interface only once.

When a class implements interfaces,each component interface isimplemented only once.

IBM Global Services



IBM Global Services


Interfaces : Alias names

INTERFACE I1 .

METHODS m1.ENDINTERFACE.

INTERFACE I2.

METHODS : m2.

INTERFACES I1.

ALIASES meth1 FOR I1~m1.

ENDINTERFACE.

CLASS c1 DEFINITION.

PUBLIC SECTION.

INTERFACES : I2.

ALIASES meth2 FOR I2~m2.

ENDCLASS.

CLASS C1 IMPLEMENTATION.

METHOD I1~m1.

...

ENDMETHOD.

METHOD : I2~m2.

...

ENDMETHOD.

ENDCLASS.

Full name of a component in theinterface when added in class oranother interface is intf~comp, Aliasnames can be used to replaced thisnames when defining compoundinterface or declaring interfaces in a

class. The class implementation must still

refer to the full name.

START-OF-SELECTION.

DATA : oref TYPE REF TO c1

CREATE OBJECT oref.

CALL METHOD : oref->I2~meth1.

CALL METHOD : oref->meth2 .

IBM Global Services



IBM Global Services


Interfaces : Interface References

INTERFACE I1.

METHODS : m1.ENDINTERFACE.

CLASS c1 DEFINITION.

PUBLIC SECTION.

INTERFACES : I1.

ENDCLASS.


METHOD I1~m1.

...

ENDMETHOD.

ENDCLASS.

START-OF-SELECTION.

DATA : oref TYPE REF TO C1,iref TYPE REF TO I1.

CREATE OBJECT oref.

CALL METHOD : oref->I1~meth1.

Iref = oref.

CALL METHOD : iref->meth1.

As class reference variables aredeclared with the static type of aclass (oref TYPE REF TO C1),interface reference variables aredeclared with the static type of ainterface (iref TYPE REF TO I1).

Interface reference variables likeclass reference variables can containobject references, which determinetheir dynamic type (Iref = oref. orCREATE OBJECT iref TYPE C1.)

When Interface reference variablesis dynamic and contain objectreferences, at this time it can onlyaccess the interface componentsimplemented in the class of thatobject.

IBM Global Services



IBM Global Services


Interfaces : Polymorphism

INTERFACE I1.

METHODS : M1 .

ENDINTERFACE.CLASS C1 DEFINITION.

PUBLIC SECTION.

INTERFACES : I1.

ENDCLASS.


METHOD I1~M1.

….

ENDMETHOD.

ENDCLASS.CLASS C2 DEFINITION.

PUBLIC SECTION.

INTERFACES : I1.

ENDCLASS.


METHOD I1~M1.

….

ENDMETHOD.

ENDCLASS.

START-OF-SELECTION.

DATA : OREF1 TYPE REF TO C1 ,

OREF2 TYPE REF TO C2 ,

IREF TYPE REF TO I1 .

CREATE OBJECT : OREF1 ,

OREF2 .

IREF = OREF1.

CALL METHOD IREF->M1.

IREF = OREF2.

CALL METHOD IREF->M1.

Interfaces allow to use differentclasses in a uniform way usinginterface references. Any no of classcan implement the interfacedifferently.

The identical interface reference

variable, statically typed to thisinterface, operates on multipleobjects that implement the interface.

IBM Global Services



IBM Global Services


Interfaces : Interfaces and Inheritance

Interfaces can be implemented inthe classes of an inheritance tree,each interface only once ( eachinterface component should have aunique name through out theinheritance tree).

The interface method componentscan be redefined in the SubClasses.

Public:

Interfaces I1

Class C1

Public:

Interfaces I1

Class C2

DATA:

CLASS-DATA:

METHODS:

CLASS-METHODS:

EVENTS:

CLASS-EVENTS:

Public:

Interfaces I1

Class C3

Interface I1

IBM Global Services



IBM Global Services


Demonstration

Working with interfaces in ABAP objects

IBM Global Services



IBM Global Services


Practice

Working with interfaces in ABAP objects



IBM Global Services



IBM Global Services


Demonstration

Using Friend class in ABAP objects

IBM Global Services




Practice

Using Friend class in ABAP objects

IBM Global Services




Events : Concept

In ABAP object events use the publish and subscribe approach.

A class declares an event and implements a method to raise (publish) the event.

The same and/ or other classes implement a method to respond (subscribe) to the event.

At runtime interested classes and objects register their wish and availability to respond.

Mehtods:trigger_e1

Events: e1

Methods:

handler_e1

Class C1 Class C2

Raises

event e1

P u b l i sh

an d

S u b s cr i b e

Handles

event e1

IBM Global Services




Events : Defining and triggering Events

CLASS testing_event DEFINITION.

PUBLIC SECTION.EVENTS my_event.METHODS

event_raising_method.ENDCLASS.

CLASS testing_event IMPLEMENTATION.METHOD event_raising_method.

RAISE EVENT my_event.ENDMETHOD.

ENDCLASS.

Events can be delcared as PUBLIC, PROTECTED, PRIVATE components of any class orinterface.

Events can be static or instance

Events can be triggered by anymethod in the class using the RAISEEVENT statement.

The parameter interface for events islimited to EXPORTING parameters,passed by VALUE.

Events don’t have implementationpart.

Event declaration

Triggering the event

IBM Global Services




Events : Handling Events

CLASS test DEFINITION.

PUBLIC SECTION.

METHODS: event_method FOR EVENTmy_event OF testing_event.

ENDCLASS.

CLASS test IMPLEMENTATION.

METHOD event_method.

….. ENDMETHOD.

ENDCLASS.

Any class can define event handlermethods for the events of the classitself or for those of other classes.

Event handler methods use the FOREVENT (event name) OF {CLASS(class name) | INTERFACE

(interface name)} addition. Methods are only executed when the

event associated with these methodsare triggered.

An event can have multiple event

handler method associate with it.

Declaration for event handler method

IBM Global Services




Events : Registering events

START-OF-SELECTION.

DATA: object1 TYPE REF TO test,

object2 TYPE REF TO

testing_event.

CREATE OBJECT: object1,

object2.

SET HANDLER object1->event_method

FOR object2.

CALL METHOD :

object2-> event_raising_method.

To automatically execute the eventhandler method when the event israised, the handler method has tobe registered.

The registration process is dynamic

i.e. the link is established atruntime. The key statement “SET

HANDLER” can register the

handler method.

Handler methods can be registeredor de-registered dynamically by

the optional key word“ACTIVATION” . “ACTIVATION”

can register new method or de-register existing method.

Registering the event

handler method

Calling the triggeringmethod

IBM Global Services




Events : Runtime Environment

Mehtods:trigger_e1

Events: e1

Methods:

handler_e1

Class C1Class C3Raises

event e1Register for

event e1

Class C2

Register forevent e1

Methods:handler_e1

e1 handler_e1

e1 handler_e1

CREATE OBJECT oref1

Oref1->trigger_e1

CREATE OBJECT oref3

CREATE OBJECT oref2SET HANDLER oref2->

handler_e1 FOR oref1

SET HANDLER oref3->

handler_e1 FOR oref1

Each object or class that can trigger instance or static events has an invisiblehandler table, where entries occur as a result of SET HANDLER statement.

The RAISE EVENT statement in the triggering method interrupts theexecution of the method until the run time finishes cascading through eachhandler registered in the handler table . The initial triggering method thenresume execution.

To delete single entries from the handler table use the ACTIVATION additionof the SET HANDLER statement.

IBM Global Services




Demonstration

Creating an Event in a class, triggering that event and handling that event fromanother class.

IBM Global Services




Practice

Creating an Event in a class, triggering that event and handling that event fromanother class.

IBM Global Services




ABAP Objects Advanced : Global classes and interfaces

Concept

Demonstrating How to create Global class.

IBM Global Services




Global classes and interfaces : Concept

Global classes and interfaces are created and stored in class pool and interfacepool like function pool (function group).

Global classes and interfaces are managed centrally and available to everyprogram.

Custom Global classes and interfaces must begin with Y* or Z*.

Global and local classes and interfaces have the same components, and there isno difference in how they are used within programs.

IBM Global Services




Global classes and interfaces : Concept (Contd.)

Global classes and interfaces aremaintained via transaction SE24 orthrough transaction SE80.

Use Class Browser to view globalclasses and interfaces in therepository.

IBM Global Services




Global classes and interfaces : Concept (Contd.)

Set Class Browser filters to select byobject type, by relation ship etc.

Results are displayed in a hierarchytree.

IBM Global Services




Global classes and interfaces : Creating Global class

1. Go to transaction SE80 and chooseClass/Interface and enter the nameof your custom class or interface(name must start with Z* or Y*) andpress enter.

2. In the Popup window choose yes.

3. Choose the Object type. Here Classis selected as object type.

1

2

3

IBM Global Services




Global classes and interfaces : Creating Global class (Contd.)

4. In the next popup enter descriptionand press SAVE button. Also checkUsual ABAP class radio button is setand Final check box is checked.

5. In the next popup enter packagename and press save button. In our

example $TMP is selected as apackage.

4

5

IBM Global Services





6. Now double click on the class, itwill then display the class builder,define attributes and methods forthe class.

7. Double click on the method nameto implement the method. It will

invoke the code editor where youhave to enter code for the method.

6

7

IBM Global Services





8. Activate the class.9. Test the class.

10. Class components can include localclasses, methods, internal types,macros which are not visible outside the class pool.

8

99

10

Types

Local class

Macros

IBM Global Services




Demonstration

Creating a Global Class using transaction SE24

IBM Global Services




Practice

Creating a Global Class using transaction SE24

IBM Global Services




Summary

In ABAP object, events use the publish and subscribe approach. A class declares an event and implements a method to raise (publish) the event.

The same and/or other classes implement a method to respond (subscribe) to theevent.

At runtime interested classes and objects register their wish and availability to

respond. Inheritance can be single inheritance ( Sub Class is inherited from a single Super

Class) or multiple inheritance (Sub Class is inherited from multiple SuperClasses). But ABAP Objects supports only single inheritance.

Like Java, ABAP Objects does not permit multiple inheritance, but using

interfaces with inheritance we can achieve the same. Interface is similar to abstract class but it has only definitions part.

The interface can be implemented only in the class that uses it.

IBM Global Services




Summary (Contd.)

With FRIEND relationship one class can grant another class/interface (and allclasses that implemented the interface) access to its PROTECTED and PRIVATEcomponents.

IBM Global Services



Questions

What is an Event? What statement we have to use to register an event handler for a specific Event?

What is Inheritance?

How can we achieve multiple Inheritance in ABAP?

How can we access nested interface?

What is a Friend class?

Which transaction we use to create Global class?

chapter 02_abap objects - advanced

Documents