oops abap ibm

7/18/2019 Oops Abap Ibm

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IBM Global Services

Copyright IBM Corporation 2003

April,2004


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Topics to cover

Different approaches to Programming

Class and objects

Methods

Constructor

Inheritance

Interface

Friendship between Classes

Events

Class-Based Eceptions


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Different approaches of Programming

!nstructured Programming"Procedural Programming"

#bject #riented Programming"


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Unstructured Programming

Consists of onl$ one main program"

%he program stands for a se&uence of

commands which modif$ data that isglobal throughout the whole program"

Characteristics

Difficult to manage once the programbecomes large"

'ame se&uence of statements arerepeated at multiple places( if the$ areneeded at multiple locations"

Disavantages

report ysubdel.DATA : sal type p decimals 2, itax type p decimals 2,

net_sal type p decimals 2 .

sal = 12000. IF sal lt 000 . itax = 0. !"#!. itax = sal $ %0.01%. !&DIF. net_sal = sal ' itax. (rite:) sal , itax ,net_sal.sal = *00.

IF sal lt 000 . itax = 0.!"#!. itax = sal $ %0.01%.!&DIF. net_sal = sal ' itax. (rite:) sal , itax ,net_sal.


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Procedural Programming

Programmer combines related se&uencesof statements into one single place( calledprocedure"

) procedure call is used to invo*e theprocedure"

)fter the se&uence is processed( flow ofcontrol proceeds right after the positionwhere the call was made"

report ysubdel.DATA : sal type p decimals 2 ,

itax type p decimals 2 ,

net_sal type p decimals 2.

sal = 12000.

PERFORMsub_calc_tax +#I&

sal itax net_sal. sal = *00.

PERFORMsub_calc_tax +#I&

sal itax net_sal.

FORMsub_calc_tax +#I&-_#A" -_ITA -_&!T_#A".

IF p_sal lt 000 .

p_itax = 0.

!"#!.

p_itax = sal $ %0.01%.

!&DIF.

p_net_sal = p_sal ' p_itax.

ENDFORM.


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Object Oriented Programming

Class e!ine an

i"ple"ente

#b$ect create !ro"

the class an %se

Classes and objects areused to model real worldentit$"

Methods inside the classesperform the functions"

Data used b$ the classesare protected between them"


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Comparison between Procedural and Object Oriented

Programming

&eat%res 'roce%re #rienteapproach

#b$ect #riente approach

("phasis Emphasis on tas*s Emphasis on things that does thosetas*s

Mo%lari)ation Programs are divided intosmaller programs *nown as

functions

Programs are organi+ed into classes

and objects and the functionalities

are embedded into methods of a

class"Data sec%rity Most of the functions share

global data

Data can be hidden and cannot be

accessed b$ eternal sources"

(*tensibility ,elativel$ more time consumingto modif$ for etending eisting

functionalit$"

ew data and functions can be easil$

added whenever necessar$


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Object Oriented Approach - ke features

." Better Programming 'tructure

/" ,eal world entit$ can be modeled ver$ well

0"'tress on data securit$ and access

1" Data encapsulation and abstraction

2" ,eduction in code redundanc$


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!e"uirement for learning OOP# in A$AP

)dopt the universal approach for modern programming"

3now the latest )B)P technologies-B)DI(wor*flow(4I( Custom controls etc

!se )B)P to integrate with Microsoft %echnologies (5ava etc

Eploit class resources and functionalities provided b$ ')P"


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Topics to cover


Class and objects

Methods

Constructor

Inheritance

Interface


Events



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Class and Object

Class is the te"plate o! an ob$ect+ It is an abstract concept, hich is reali)e by

creating an ob$ect !ro" it+

What is your idea about a Maruti-800 car? You will say that it is afour-wheel, ve seater vehicle with a 800 cc engine.

The idea you have in your ind is the classfor Maruti-800.!et us

call it as class Maruti-800.

"ow, you see a real Maruti-800 car in front of you. #o, this is theobjectof class Maruti-800. $n other words, the real car is reali%ation&instantiation of the class Maruti-800.

Still con!%se--- #+. ++see the e*a"ple belo


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Attributes of Object Oriented Programming

Abstraction / (verything is vis%ali)e in ter"s o! classes an ob$ects+

(ncaps%lation /ecessary ata are hien !ro" the %sers in class+

Inheritance / A class can be replicate into a s%bclass , hich can be "oi!ie+

'oly"orphis" /Methos o! sa"e na"e behave i!!erently in i!!erent classes+


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%ocal and &lobal Classes

Global Class 1ocal Class

)n$ program #nl$ the program where it is defined"

In the Class ,epositor$ #nl$ in the program where it is

defined"

Created using transaction 'E/1 Created using 'E06

Must begin with 7 or 8 Can begin with an$ character

Accessed b

#tored in

Created b

'amespace


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Defining %ocal Classes

/!-/T #+-#13 .

CLASSc1 DEFINITION.

-+"I4 #!4TI&.

data : (_num type i 5alue .

met6ods : m1.

ENDCLASS.

4"A## c1 I7-"!7!&TATI&.

7!T8D 71.

9/IT!:) %I am 71 in 41%.

!&D7!T8D.

!&D4"A##.#TA/T'F'#!"!4TI&.

DATA : ore1 T-! /!F T c1 .

4/!AT! ;!4T : ore1.

(rite:) ore1'


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(mplementing %ocal Classes

1ocal class in a progra" is i"ple"ente as

!ollos/

CLASS IMPLEMENTATION.

..

ENDCLASS.Methos %se by the class are escribe here+

A class can be i"ple"ente

At the en o! the progra" lie s%bro%tines5+

A!ter the class e!inition+

I! the latter is aopte, one "%st then assign

s%bse6%ent noneclarative state"ents e*plicitly to a

processing bloc, s%ch asSTART-OF-SELECTION( so that they can be accesse"

/!-/T #+-#13 .

CLASSc1 DEFINITION.

-+"I4 #!4TI&.

data : (_num type i 5alue .

met6ods : m1.

ENDCLASS.

CLASSc1 IMPLEMENTATION.

7!T8D 71.

9/IT!:) %I am 71 in 41%.

!&D7!T8D.

ENDCLASS.#TA/T'F'#!"!4TI&.

DATA : ore1 T-! /!F T c1 .

4/!AT! ;!4T : ore1.

(rite:) ore1'


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Different places of implementing class

Class implemented at the end of theprogram

Class implemented after Definition


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)ho can use a class*

class c2 e!inition inheriting !ro"c7+

p%blic section +

"ethos / "2+

enclass+

class c2 i"ple"entation+

"etho "2+

rite/89 :+rom subclass, w.num+

en"etho+

enclass+

;('#;< =S>B##'S7? +

C1ASS c7 D(&II


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#ections of a Class

CLASS C1 DEFINITION.

PUBLIC SECTION.

DATA:

METHODS:

EVENTS:

PROTECTED SECTION.

DATA:

METHODS:

EVENTS:

PRIVATE SECTION.

DATA:

METHODS:

EVENTS:

ENDCLASS.

A Class p%ts its co"ponents %ner three istinct

sections/

Public Sectin!-Co"ponents place here !or"the e*ternal inter!ace o! the class they are

visible to all %sers o! the class as ell as to

"ethos ithin the class an to "ethos o!s%bclasses

P"tecte# Sectin!-Co"ponents place inprotecte section are visible to the chilren o! the

classs%bclass5 as ell as ithin the class

P"i$ate Sectin9-Co"ponents place here areaccessible by the class itsel!+

%here is no default visibilit$ section in a class"

%his se&uence of visibilit$ must be maintainedin a class


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A #ill 23ample

7ou are an emplo$ee ;object of class9- emplo$ee


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Components of a Class

A Class basically contains the !olloing/

Att"ibutes9-Any ata,constants,types eclare ithin a class !or" the attrib%te o!the class+

Mets9-Bloc o! coe, proviing so"e !%nctionality o!!ere by the class+ Can beco"pare to !%nction "o%les"

E$ents9-A "echanis" set ithin a class hich can help a class to trigger "ethos o!

other class+

Inte"'aces9-Inter!aces are inepenent str%ct%res that yo% can i"ple"ent in a classto e*ten the scope o! that class"


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(nstance and #tatic Components

/!-/T #+-#13 .4"A## c1 D!FI&ITI&.-+"I4 #!4TI&. data :i_num type i 5alue . class-data :

s_num type i 5alue .

!&D4"A##.

4"A## c1 I7-"!7!&TATI&.!&D4"A##.

#TA/T'F'#!"!4TI&.DATA : ore1 T-! /!F T c1 .

4/!AT! ;!4T : ore1.(rite:) ore1->i_num.(rite:) c1=>s_num .(rite:) ore1->s_num.

Instance co"ponents e*ist

separately in each instance

ob$ect5 o! the class an are

re!erre %sing instance

co"ponent selector %sing :+

Static co"ponents only e*ist

once per class an are vali !or

all instances o! the class+


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Two Additions in %ocal Class Definition

A##itin ( ! CLASS class DEFINITION DEFERRED.

!sed to refer to a class at some point in a code and the class is notdefined before the line"

4"A## 42 DEFINITION DEFERRED.

4"A## 41 D!FI&ITI&.

-+"I4 #!4TI&.

DATA 2 TYPE REF TO C2.

!&D4"A##.

4"A## 42 D!FI&ITI&.

public section.

data : num type i 5alue .

!&D4"A##.

start'o'selection.

data : ob?1 type re to 41.

4/!AT! ;!4T ob?1.

create ob?ect ob?1'


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Two Additions in %ocal Class Definition

A##itin ) ! CLASS class DEFINITION LOAD

%he co'iler norally loads the descri'tion of a globalclass frothe class librarythe rst tie you use the class in your 'rogra .(owever, if the rst access to a global class in a 'rogra is to its

static componentsor in the denition of an event handlermethod, you ust load it e)'licitly using the stateent *!+## class$"$T$/" !/+. This variant has no corres'onding "*!+##stateent.

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Creating an Object

%o create an object ( the following stepsneed to be followed9-

'tep .9 Create a reference variable withreference to the class"

DATA !=object name> T*PE REF TO=class name>"

'tep / 9 Create an object from the referencevariable9-

C,E)%E #B5EC% =object name>"

report ysubdel.

4"A## c1 D!FI&ITI&.

-+"I4 #!4TI&.

DATA : pro@BC type c 5alue%AA-%.

!&D4"A##.

4"A## c1 I7-"!7!&TATI&.

!&D4"A##.

#TA/T'F'#!"!4TI&.

DATA : ob?1 type re to c1.

CREATE OBJECT: ;1.

(rite:) ob?1'


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C!2AT2 PU$%(C5P!OT2CT2D5P!(6AT2 ADD(T(O'#

#nta3 /C%A## 7classname1 D2+('(T(O' 8 9C!2AT2 PU$%(C5P!OT2CT2D5P!(6AT2:

C,E)%E P!B?ICaition is i"plicit in every class e!inition i! the other C;(A


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Attributes

)ttributes are internal data fields within a class that can have an$ )B)Pdata t$pe"

(nstance Attributes

(*ist separatel in each instanceob$ect5 o! the class +

Declare %sing theDATAstate"ent+

#ne cannot %se theTA+LESorNODESstate"ent in the eclaration part o! theclass+

#tatic Attributes

Available once for each class+

Declare %sing theCLASS-DATAstate"ent an are retaine thro%gho%t the entirer%nti"e+ All the ob$ects ithin a class can access its static attrib%tes+

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Attributes8continued

Tpes and Constants in Classes

T,%es

T*PESstate"ent is %se to e!ine any n%"ber o! yo%r on ABA' ata types ithin aclass+

Cnstants

Constants are special static attrib%tes, hose val%es are speci!ie hen they are eclare

an hich cannot be change later+


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Topics to cover


Class and objects

Methods

Constructor

Inheritance

Interface


Events


IBM Global Services


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;ethods

Methos are the internal proce%res o! a

class +

Eave a para"eter inter!ace, thro%gh

hich the syste" passes val%es to the"

hen they are calle, an thro%gh hich

they can ret%rn val%es to the caller+

Can access all the attrib%tes o! their class+


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#nta3 for defining methods

Declare in the e!inition part o! a class or in an inter!ace as !ollos/

METODS IMPORTIN.. /0AL1E23/43 T*PE t,%e /OPTIONAL3..E6PORTIN.. /0AL1E23/43 T*PE t,%e /OPTIONAL3..

CANIN.. /0AL1E23/43 T*PE t,%e /OPTIONAL3..

RET1RNIN 0AL1E2


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Tping Parameters

)ll parameters mustbe declared using the addition T*PEor the addition LI7E"

ith LI7E$ou can nl,refer to data t$pes of class attributes *nown at this point in A+APOb8ectsand not to data t$pes from the )B)P Dictionar$"

%he following entries in the table shown below are allowed after T*PEas parameter t$pes"

#nta3 !elevance

T*PE t stands for all data t$pes from the )B)P Dictionar$

and all A+APdata t$pes *nown at this point+ T*PE AN* stands eplicitl$ for a parameter declaration without

t$pe reference" %his means that the parameter

inherits all technical attributes of the parameter that

has been passed when the method is called" T*PE REF TO ci' stands for a class or interface reference"

T*PE LINE OF itab stands for the line t$pe of an internal table itab"

T*PE /AN*9INDE69STANDARD9SORTED9

ASED3 TA+LEstands for the internal table t$pe of the table t$pe

specified

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(mplementing ;ethods

All "ethos eclare in the e!inition part o! a class

sho%l be i"ple"ente in the i"ple"entation section o!

the class ithin the !olloing bloc/

ME%#D =meth>" """

EDME%#D"#ne sho%l not speci!y any inter!ace para"eters at the

ti"e o! i"ple"entation, since these are e!ine in the

"etho eclaration+


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#tatic ;ethod

o1ie any other class co"ponents , "ethos canbe static or instance+

o>>

oStatic "ethos can have i"port an e*port8changing para"eters 5 or ret%rning para"eters + It

can also raise e*ceptions+

oStatic "ethos can only or ith the static

attrib%tes o! yo%r class+ Instance "ethos can

or ith both static an instance attrib%tes+

o#ne can call a static "etho %sing an ob$ect o!

the class or irectly %sing the class by class

co"ponent selector+

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Calling ;ethods

CALL METOD

E6PORTIN... :....RECEI0IN " : &E6CEPTIONS... : "c

i...

All nonoptional inp%t para"eters "%st be

passe %sing the (F'#;B##'S7? +DA


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Calling ;ethods8continued

#nta3 !elevance

CALL METOD ... Methods of the same class;in the implementation part< can

be called directl$ using their name =meth>"CALL METOD ... " @isible static methods can be called from outside the class

using this s$nta where =class> is the name of the relevant

class"CALL METOD


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Calling ;ethods8continued

#nta3 !elevance

CALL METOD 2 '4. !sed to call a method where 9-

%he interface of a method consists onl$ of a single

IMP#,%IA parameter

%here is a single non-optional IMP#,%IA parameter and

several other optional IMP#,%IA parameters"

)ll the IMP#,%IA parameters are optional ( one being

declared as P,EFE,,ED P),)ME%E,"'(:


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Dnamic ;ethod Calls

Instance( self-referenced( and static methodscan all be called d$namicall$ the class namefor static methods can also be determinedd$namicall$9- oref->;method;method;methodIt is callea%to"atically !or the class before it is accessed for

the first time that is, be!ore one o! the !olloing

actions/

C!2AT2 O$?2CTobj !ro" the class+

Call a static "etho / 9CA%% ;2T=OD: class41meth+

;egistering a static event hanler "etho %sing

#2T =A'D%2! class41meth for obj>

;egistering an event hanler "etho !or a static event

o! the class class+

Aressing a static attrib%teith class41a+

/!-/T #+-#2.4"A## c1 D!FI&ITI& .-+"I4 #!4TI&.4"A##'DATA : &+7 T-! I A"+! .4"A##'7!T8D#:4"A##_4T/+4T/.

!&D4"A##.

4"A## c1 I7-"!7!&TATI&.

7!T8D 4"A##_4T/+4T/.9/IT!:) %I am classconstructor%.

!&D7!T8D.!&D4"A##.

#TA/T'F'#!"!4TI&.

9/IT!:) C1=>NUM.

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#tatic Constructor8>continued

Eception9-


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Comparison between Different ;ethods

Tpe of;ethod

Triggering mechanism (mportparameter*

23portParameter*

ChangingParameter*

!eturningParameter*

Can raise23ceptions*

(nstance Calle by %sing ob$ect = = = = =

#tatic Calle by %sing ob$ect

or re!erring to class

= = = = =

(nstanceConstructor

Calle a%to"atically,i""eiately a!ter theC;(A


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Pointer Tables

It is possible, in the sa"e progra", toinstantiate "any ob$ects o! the sa"eclass+ Eoever, in "any sit%ationsinternal tables are a "ore elegant ay o!creating a list o! the sa"e in o! ataob$ect

;e"e"ber, re!erence variables arehanle lie any other ata ob$ect ith anele"entary ata type

#%tp%t

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Topics to cover


Class and objects

Methods

Constructor

Inheritance

Interface


Events


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(nheritance

'arent Class S%b Class

) single class can give birth to itssubclasses b$ inheritance"

#ne parent class can have "%ltiple

s%bclasses, b%t one s%bclass can have only

one parent class+Eence,multi%le

in&e"itance is nt all@e# in A+AP.'ubclasses have full access to all thepublic and protected components of parentclass" %he$ can modif$ to re-implementthose components of their own")lso(subclasses can create new components inthem"

Private components of parent classes arenot *nown to subclasses" %here can becomponents with same name in privatesection in both the parent and subclasses (each one wor*ing and being identifiedseparatel$ in their respective classes"

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6isibilit of Components

Each class component has a visibility. In ABAP Objects the whole class definition is

separated into three visibility sections: PUBLIC, PROTECTED, and PRIVATE. One can

never change component visibility via inheritance.

P1+LIC!This section is made up of the subclass' own public components together with all

public components of all superclasses. There is unrestricted access to the public section of

the subclass.

PROTECTED!This section is made up of the subclass' own protected components togetherwith all protected components of all superclasses .

PRI0ATE!This section is made up of the subclass' own private components accessibleonly in that subclass. Each subclass works with its own private components and can't evenuse the private components of its superclasses. But as long as a method inherited from a

superclass is not redefined, it still uses the private attributes of the superclass, not those of

the subclass, even if the subclass has private attributes of the same name.

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Creating #ubclass

S%bclasses can be create !ro" its

s%perclass %sing the synta*/

C?)'' =subclass> DEFII%I#IE,I%IA F,#M =superclass>"

S%bclass inherits all the p%blic an protecte

co"ponents o! the s%perclass+

S%perclass sho%l not be eclare as a

&IA1 class+

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;odifing methods in subclass


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Abstract ;ethods and Classes

One cannot create an object from an abstract

class>#nly s%bclasses can be erive !ro"

the"+

C%A## 7classname1 D2+('(T(O' A$#T!ACT>

Abstract methods cannot be implemented in

the same class+ #nly the s%bclasses o! thatclass can i"ple"ent it+

;2T=OD# 7method.name1 8>A$#T!ACT

An class containing an abstract method has

to be an abstract class+ All s%bse6%ent

s%bclasses that o not i"ple"ent the "etho"%st also be abstract+


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+inal ;ethods and Classes

&inal classes cannot have s%bclasses+ #nly the

class can be instantiate+

CLASS DEFINITION FINAL.

A !inal "etho cannot be ree!ine ins%bclasses

METHODS .FINAL

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(nheritance and #tatic Attributes

Static attrib%tes only e*ist once in

each inheritance tree+ #ne can

change the" !ro" o%tsie the class

%sing the class co"ponent selector

ith any class na"e, or ithin any

class in hich they are share+


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(nheritance and (nstance Constructors

Case Description Necessity of calling

constructor of

superclass by subclass

. one of the superclass and subclass have

eplicit constructor"

ot re&uired

/ 'uperclass have eplicit constructor( but

subclass does not have an$ eplicit constructor"

ot re&uired

0 'uperclass does not have an eplicit

constructor( but subclass have one"

,e&uired

1 Both the superclass and subclass have eplicit

constructor

,e&uired

S%perclasses an8or s%bclasses can have e*plicit constr%ctors o! their on+

Constr%ctor o! a s%bclass so"eti"es have to call the constr%ctor o! the s%perclass

%sing9 CALL METOD ! S1PER->CONSTR1CTORepening on the !olloing/

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(nheritance and #tatic Constructors

Every class has a static constructor called CLASS_CONSTRUCTOR.

The first when a subclass in a program is accessed, its static constructor is executed. But,

before it can be executed, the static constructors of all of its superclasses must already

have been executed. A static constructor may only be called once per program. Therefore,

when one first address a subclass, the system looks for the next-highest superclass whosestatic constructor has not yet been executed. It executes the static constructor of that class,

followed by those of all classes between that class and the subclass that is addressed.

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(nheritance and (nstance Creation

&or eachin#i$i#ual class( theCREATE P1+LIC9PROTECTED9PRI0ATEaitions tothe C1ASSstate"ent control ho can create an instance o! the class or, in other ors,

can call its instance constr%ctor+


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(nheritance and (nstance Creation

(. Su%e"class @it& a##itin CREATE PROTECTED

Subclasses can have every CREATE addition. Without addition they inherit the attribute

CREATE PROTECTED. The superclass allows its subclasses unlimited instantiation and

therefore also the publishing of its protected instance constructor.

(. Su%e"class @it& a##itin CREATE PRI0ATE

If the subclass is not a friendof super class , the subclass cannot be instantiated. None of

the CREATEadditions is permitted with the subclass, because this would always lead to

the unauthorized publishing of the superclass constructor.

If the subclass is a friendof super class, all CREATEadditions are permitted with thesubclass. The default one is CREATE PRIVATE. As a friend, the subclass can publish the

superclass' private constructor in any form.

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#tatic Tpe and Dnamic Tpe of a 6ariable

The statictype is the type (class or interface) with which the reference variable has beentyped.

DATA : oref type ref to c1. Static type of oref is pointing to class c1

The dynamictype is the class of the object to which the reference in a reference variable

points .

CREATE OBJECT OREF. Dynamic type also points to c1

CREATE OBJECT OREF TYPE C2. Dynamic type points to subclass c2 of C1

If the static and dynamic types of a reference variable are different, the static type should

always be more general than the dynamic type.

.

S%perclass #B@(C< Any classIts s%bclass

#peciali@ation increases

&enerali@ation (ncreases

Class / C0

Class / C

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Assignment between !eference 6ariables

If you make assignments between reference variables, the static type of the target

variable must always be same or more generic than the dynamic type of the source

variable.

For example, a super class is always more generic than its subclass.

Syntax check for the program ensures that static type of target variable is more general than

static type of source variable.




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'arrowing Cast

NarroingO cast "eans that the assign"ent changes !ro" a "ore speciali)e vie ith

visibility to "ore co"ponents5 to a "ore generali)e vie ith visibility to !eer

co"ponents5+

N'arrowing castO is also re!erre to as N%p castO + N>p castO "eans that the static type o!the target variable can only change to higher noes !ro" the static type o! the so%rce

variable in the inheritance tree, b%t not vice versa+




%he static t$pe of the target variable mustalwa$s be more generic than the static t$pe ofthe source variable"

IBM Global Services


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23ample of 'arrowing Cast

!eference variable of a classassigned to reference variable of

class / object

!eference variable of a subclass

assigned to reference variable of its

superclass>

IBM Global Services


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)idening Cast

DATA: o_ref1 TYPE REF TO object,o_ref TYPE REF TO c!"##.

...

o_ref $% o_ref1.

...

CATH SYSTEM&E'CEPTIONS(o)e_c"#t_error % *.

o_ref $% o_ref1.

ENDCATCH.

In so"e cases, yo% "ay ish to "ae an assign"ent in

hich the static type o! the target variable is less general

than the static type o! the so%rce variable+


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Polmorphism via (nheritance

Kith inheritance, a re!erence variable

e!ine ith respect to a class "ay not only

point to instances o! that b%t also to

instances o! s%bclasses o! the sa"e+ #ne

can even create s%bclass ob$ects %sing a

re!erence variable type ith respect to a

s%per class+

'oly"orphis" thro%gh inheritance can be

achieve by playing ith static an yna"ic

type o! a re!erence variable+

Instances o! a s%bclass "ay be %se

thro%gh the s%per classPs inter!ace+ Khenthis is one, a client canPt access all

co"ponents e!ine in the s%bclass, only

those inherite !ro" the respective s%per

class+

classc1 d!"#"t"$#.. . . . . . .

#dclass.

classc1 "%&l%#tat"$#'

' ' ' ' ' '

#dclass'

classc2 deinition "#()"t"#* !)$%c1.. . . . . .

#dclass.

classc2 "%&l%#tat"$#.

. . . . . . .

#dclass.

sta)t-$!-slct"$#.

data : ore1 type re to c1,

ore11 type re to c1,

ore2 type re to c2.

create ob?ect ore1 type c2 .

create ob?ect ore2.

ore11 = ore2.

(rite:) ore1'


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(nheritance B Object !eferences

(*ternal Inter!ace

DATA: oref1 TYPE REF TO C1,oref+ TYPE REF TO C+.

...

CREATE O-ECT oref+.

oref1 % oref+.

a0

m0

a7

a2

a3

"7

"2

"3

;e!erence variables eclare ithre!erence to a s%perclass incl%ing an

abstract class5 can point to an ob$ect o!

a s%bclass o! this s%perclass, b%t only

access the co"ponents o! that ob$ect

that are non to the s%perclass+

C3 IE(;I


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(nheritance B Object !eferences E

(*ternal Inter!ace

DATA: oref1 TYPE REF TO C1....

CREATE O-ECT oref1 TYPE C+.

a0

m0


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Topics to cover


Class and objects

Methods

Constructor

Inheritance

Interface


Events


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(nterface

Independent structures containing definition of its own components"

Incorporated in the public section of a class definition and the methodsof the interface are implemented in the implementation section of thatclass"

Etends the scope of a class b$ adding their own components to itspublic section"

)llows users to address different classes via a universal point ofcontact"

Interfaces( along with inheritance( provide one of the pillars ofpol$morphism( since the$ allow a single method within an interface tobehave differentl$ in different classes"

IBM Global Services


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Defining (nterfaces

Can be eclare globally or locally ithin aprogra"+

1ocally eclare in the global portion o! a progra"

%sing/

('T2!+AC2 7intf1>

>>>

2'D('T2!+AC2>


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Defining (nterfaces8> A few additions

75 INTERFACE


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Defining (nterfaces8> Additions for (mplementation in Classes

Addition Efect

... A+STRACT METODSmet&( ... met&n

)ssigns the propert$ A+STRACTto the specifiedinstance methods of the interface"

... FINAL METODS met&( ...met&n

)ssigns the propert$ FINALto the specifiedinstance methods of the interface"

... ALL METODS A+STRACT )ssigns the propert$ A+STRACTto all instancemethods of the interface"

... ALL METODS FINAL )ssigns the propert$ FINALto all instancemethods of the interface"

... DATA 0AL1ES att"( :$al( ... att"n : $aln

Assigns initial val%es to the attrib%tes speci!ie DATA,

C%A##-DATA5+


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Component of (nterfaces

%he interface cm%nentsare declared in the I%E,F)CEEDI%E,F)CEbloc*"

Instance Cm%nents Static Cm%nents

DATA for instance attributes CLASS-DATA for static attributes

METODS for instance methods CLASS-METODS for static methods

E0ENTS for instance events CLASS-E0ENTS for static events

T*PES for internal class t$pes CONSTANTS For constants

Ot&e" Inte"'ace Cm%nents

I%E,F)CE'!or nesting inter!aces)?I)'E'!or aliases !or co"ponents o! inter!aces

#ne cannot %se the A1>( aition ith the DA


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(mplementing (nterfaces

Inter!aces o not have instances+ ;ather, they are i"ple"ente by classes+ &or that,

inter!aces are incl%e in the p%blic section o! a class e!inition %sing the !olloing

synta*/

I%E,F)CE' =intf>"


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(nterface !eference

1ie classes , re!erence variables can be create ith respect to an inter!ace


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Addressing Objects using (nterface !eference

I! a class Qclass i"ple"ents an inter!ace Qint!, the inter!ace re!erence variable Qire!

can be assigne the class re!erence variable Qcre! to "ae the inter!ace re!erence in

Qire! point to the sa"e ob$ect as the class re!erence in Qcre!+ G =cref>

IBM Global Services


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Assignment using (nterface !eferences

#ne can assign inter!ace re!erences to other inter!ace8class re!erence variables, %sing

M#( state"ent or the assign"ent operator 5 + Eoever, there are certain restrictions

hile oing so+ Khen one oes this in a progra", syste" "%st be able to recogni)e in the

synta* chec hether an assign"ent is possible+

S%ppose e have a class re!erence Qcre! an inter!ace re!erences Qire!, Qire!7, an

Qire!2+


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Assignment using (nterface !eferences8check at !untime

Besies static chec, yna"ic chec to ens%re consistency o! assign"ent o! inter!ace

re!erences+

&or that, the casting operator - or M#( -


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(nterfaces B Defining and (mplementing Compound (nterfaces

CLASS c1 DEFINITION.

PLIC SECTION.

INTERFACES: /*.

ENDCLASS.

CLASS c1 IMPLEMENTATION.

METHOD /10(et.

2

ENDMETHOD.

METHOD /0(et.

2

ENDMETHOD.

METHOD /+0(et.

2

ENDMETHOD.

ENDCLASS.

INTERFACE /1.

METHODS (et.

ENDINTERFACE.

INTERFACE /.

METHODS (et.

INTERFACES /1.

ENDINTERFACE.

INTERFACE /+.

METHODS (et.

INTERFACES: /1, /.

ENDINTERFACE.

INTERFACE /*.

INTERFACES /+.

ENDINTERFACE.

=o% can co"pose a ne inter!ace !ro" several e*isting

ones+ S%ch an inter!ace is calle a compound

interfaceL an inter!ace hich is containe in another

inter!ace is calle a component interface


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(nterfaces B Alias 'ames

CLASS c1 DEFINITION.

PLIC SECTION.

INTERFACES: /1.

ALIASES (1 for/10(et.

ENDCLASS.

CLASS c1 IMPLEMENTATION.

METHOD /10(et.2

ENDMETHOD.

ENDCLASS.

DATA: oref TYPE REF TO c1.

CREATE O-ECT oref.

CALL METHOD oref&3(1.

INTERFACE /1.

METHODS (et.

ENDINTERFACE.

INTERFACE /.

INTERFACES /1.

ALIASES (1 FOR /10(et.

ENDINTERFACE.

INTERFACE /+.

INTERFACES /1, /.

ALIASES (1 FOR /0(1.

ENDINTERFACE.


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Topics to cover


Class and objects

Methods

Constructor

Inheritance

Interface


Events


IBM Global Services


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+riends

In classes, there is nor"ally a strict ivision beteen o%tsie PU$%(C5 an

insie P!OT2CT2Dor P!(6AT25+ A %ser can only access the p%blic

co"ponents o! a class+ A s%bclass have access to p%blic an protecte sections

o! its s%perclass+

In rare cases, classes have to or together so closely that they nee access toone anothersP protecte or private co"ponents+ In orer to prevent these

co"ponents being available to all %sers, there is the concept o! !rienship

beteen classes+

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+riends8continued

A class can eclare other classes an inter!aces an hence all classes that i"ple"ent

this inter!ace5 as !riens by incl%ing +!(2'D#aitions to the C1ASS +++ D(&II


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6arious Additions to the +riends

%he CLASS ... DEFINITIONstatement has mainl$ two differentFRIENDSadditions to offer friendship to other classes:interfaces9

IBM Global Services


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+riends8continued

C7 C2&rants friendship to

C77 C22

(nherited to (nherited to

#tatement IesF'o

C2 can access all attrib%tes8"ethos o! C7 !ro" any section+ =

C2 can create instances o! C7, irrespective o! its C;(A


88/123


Topics to cover


Class and objects

Methods

Constructor

Inheritance

Interface


Events



89/123

IBM Global Services


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Declaring events

(vents are eclare in the eclaration part o! a class or in an inter!ace+


91/123


Triggering 2vents

An instance event in a class can be triggere by any "etho in the class+ Static events

can be triggere by any static "etho+ G =f i>"""&or each !or"al para"eter 7e i 1that is not e!ine as optional, one "%st pass a

corresponing act%al para"eter 7f i 1in the (F'#;


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IBM Global Services


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2vents B !egistering

START&OF&SELECTION.

8 c1 7ec!"re# "47 r"/#e# e)e4t e1

8 c "47!e# e)e4t e1

CREATE O-ECT ref_to_c1,ref_to_c.

SET HANDLER ref_to_c&3e)e4t_"47!er

FOR ref_to_c1.

CALL METHOD:

ref_to_c1&3tr/99er_e)e4t+

So !ar e have statically eclare an event an

i"ple"ente a trigger an a corresponing

hanler


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e7 hanlerHe7

e7 hanlerHe7

2vents B !untime 2nvironment

C7

'%blic, 'rotecte,'rivate

Methos/ triggerHe7

(vents/ e7

raises event e7

C4

'%blic, 'rotecte,'rivate

Methos/ hanlerHe7

hanlerHe2

C3'%blic, 'rotecte,

'rivate

Methos/ hanlerHe7register !or e7

CREATE O-ECT oref1

CREATE O-ECT oref+

CREATE O-ECT oref*

ore!7triggerHe7register !or e7

SET HANDLER oref+&

3"47!er_e1 FOR oref1

SET HANDLER oref*&

3"47!er_e1 FOR oref1

(ach ob$ect that can trigger events has an invisible hanler table, here the entries occ%r as a res%lt

o! S(< EAD1(; state"ents


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2vents with Parameters

(vents can have e*port para"eters, hich it passes to its event hanler

"etho+


96/123


Topics to cover


Class and objects

Methods

ConstructorInheritance

Interface


Events


IBM Global Services


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)hat is an 23ception*

)n eception is a situation that occurs during the eecution of an )B)Pprogram( which renders a normal program continuation pointless"

(*ceptions can be etecte at the ti"e o! progra" co"pilation or at

r%nti"e+I! the e*ception etecte at r%nti"e is not hanle properly by the

progra" itsel!, e get a short %"p an the e*ec%tion ter"inates+

IBM Global Services


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Classification of 23ceptions

(*ceptions o! vario%s ins can be broaly classi!ie as /

(*ceptions that can be hanle+

(*ceptions that cannot be hanle+

Eceptions that can be handledinicate error sit%ations in the r%nti"e

environ"ent or in the ABA' progra", in the case o! hich the progra" e*ec%tioncan be contin%e by hanling the e*ception in the ABA' progra" itho%t the

syste" reaching a critical conition+ (f such a situation is not handled a runtime

error will occur.

Eceptions that cannot be handledinicate critical error sit%ations in ther%nti"e environ"ent, hich cannot be hanle ith8by ABA' "eans an alays

ca%se a r%nti"e error+ Database space proble" can be an e*a"ple o! s%chcategory+

IBM Global Services


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Traditional )as of Catching !untime 23ceptions

Areas $rief Overview

In )B)P catch system-exceptions = . . . . . . .

Endcatch.

If sy-subrc= .

< exception handling statements>Endif.

In function module Creating exceptions for function module, raising them at appropriatepoints in the FM , assigning different sy-subrc values for each

exceptions at the time of the FM call and later dealing with them.

In Methods Creating different exceptions at the time of declaring methods,raising those exceptions within the method, assigning different sy-

subrc values at the time of method call and later dealing with those

values.

IBM Global Services


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)hat is Class-based e3ception handling*

In Classbase e*ceptions hanling approach, e*ceptions are generally

represente by ob$ects o! e*ception classes+ sers can also e!ine on e*ception classes globally8locally, i! re6%ire an can

raise the" %sing !A(#2 2


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T!I8CATC=82'DT!I

Classbase e*ceptions are hanle %sing


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Class-$ased 23ceptions B #AP 23ception Classes E

C


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#AP 23ception Classes

SA' provie e*ceptionclasses are erive !ro" the speci!ic class CFH;##m.;


111/123

IBM Global Services


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Class-$ased 23ceptions B Debug ;ode


113/123


Class-$ased 23ceptions B Debug ;ode

IBM Global Services


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Class-$ased 23ceptions B Creating a &lobal 23ception Class 0E

(nter class na"e Clic Create

ote S%perclass

an class type

S(24

IBM Global Services


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Class-$ased 23ceptions B Creating a &lobal 23ception Class E

ote the 2 attrib%tes inherite !ro" c*Hroot s%perclass

te3tid >se to e!ine i!!erent te*ts !or e*ceptions o! a partic%lar class+

A!!ects the res%lt o! "etho getHte*t

previous I! one e*ception is "appe to another, this attrib%te can store the

original e*ception+ I! a r%nti"e error occ%rs, the short %"p contains the te*ts

belonging to all the e*ceptions in the chain

Go to

Methos


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117/123


Class-$ased 23ceptions B Creating a &lobal 23ception Class KE

Call to t&e const'(cto' of s(pe'classes is a(to)aticall* +ene'ated

Clic on

previo%s

ob$ect b%tton

to ret%rn to"ethos tab


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IBM Global Services


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Class-$ased 23ceptions B Creating a &lobal 23ception Class LE

A line has been ae to the constr%ctor to initiali)e the ne attrib%te+


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Class-$ased 23ceptions B Creating a &lobal 23ception Class ME

,o to t&e ets tab and add a tet fo' t&eeception .

IBM Global Services

Class-$ased 23ceptions B Creating a &lobal 23ception Class


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p g p

NE


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Afte' pe'fo')in+ a s*nta c&ec and

addin+ t&e tets to t&e O23 'et('n to t&e

Att'ib(tes tab

IBM Global Services


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Class-$ased 23ceptions B Creating a &lobal 23ception Class 0E

on4t fo'+et to activate t&e object

ote t&at t&e tet 4s &ave been added to t&e att'ib(tes pa+e as

oops abap ibm

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