03 ABAP Objects -Inheritance

(1)

ABAP Objects Advanced -Inheritance

(2)

ABAP Objects Advanced : Inheritance Topics



 ConceptConcept



 Snta! and "isibilitSnta! and "isibilit



 Abstract Classes and Met#ods Abstract Classes and Met#ods



 $inal Classes and Met#ods$inal Classes and Met#ods



 Static Co%ponents in In#eritanceStatic Co%ponents in In#eritance



 Met#od &ede'initionMet#od &ede'inition



 Constructor in In#eritanceConstructor in In#eritance



 Object &e'erences in In#eritanceObject &e'erences in In#eritance



(3)

Inheritance : Concept



 In#eritance is one o' tIn#eritance is one o' t#e %ost po)er'ul 'eature o' object #e %ost po)er'ul 'eature o' object oriented pro(ra%%in(*oriented pro(ra%%in(*



 In#eritance is t#e process o' creatin( ne) classes+ called derived classes or SubIn#eritance is t#e process o' creatin( ne) classes+ called derived classes or Sub Classes or c#ild classes 'ro% e!istin( classes c

Classes or c#ild classes 'ro% e!istin( classes called base classes or Superalled base classes or Super Classes or parent classes*

Classes or parent classes*



 ,#e derived class in#erits all t#e capabilities o' t#e base class but ,#e derived class in#erits all t#e capabilities o' t#e base class but can addcan add e%bellis#%ents and re'ine%ents o' its

e%bellis#%ents and re'ine%ents o' its o)n* ,#e base class is unc#an(ed b to)n* ,#e base class is unc#an(ed b t#is#is process*

process*

Grand Parent Class Grand Parent Class

Parent Class Parent Class

C#ild Class C#ild Class

Sin(le In#eritance supported Sin(le In#eritance supported

b ABAP Objects b ABAP Objects

Parent Class

Parent Class Parent ClassParent Class

C#ild Class C#ild Class

Multiple In#eritance not

supported b ABAP

Objects

(4)

Inheritance : Concept !Contd"#



 ,#e relations#ip bet)een t#e,#e relations#ip bet)een t#e base classes and t#e derived base classes and t#e derived classes can be

classes can be represented in anrepresented in an In#eritance tree* #ere base

In#eritance tree* #ere base

classes o' eac# derived class can classes o' eac# derived class can be retraced alon( an uni.ue pat# be retraced alon( an uni.ue pat# to a sin(le root node o' t#e tree* to a sin(le root node o' t#e tree*



 A Sup A Super Class is a Generali/ationer Class is a Generali/ation o' its Sub Classes

o' its Sub Classes and on t#eand on t#e ot#er #and a Sub Class is a ot#er #and a Sub Class is a

Speciali/ation o' its Super Class* Speciali/ation o' its Super Class*

$%per C&ass $%per C&ass P%b&ic: P%b&ic: Protected: Protected: Private: Private: C&ass C1 C&ass C1 P%b&ic: P%b&ic: Protected: Protected: Private: Private: C&ass C2 C&ass C2 P%b&ic: P%b&ic: Protected: Protected: Private: Private: C&ass C3 C&ass C3 &oot node &oot node Generali/ed Generali/ed Class Class Speciali/ed Speciali/ed Class Class

More speciali/ed class More speciali/ed class ' ' e e n n e e r r a a & & i i ( ( a a t t i i o o n n

$ $ p p e e c c i i a a & & i i ( ( a a t t i

(5)

Inheritance:

Adva

ntaes



 In#eritance per%its codeIn#eritance per%its code +e%sabi&it.+e%sabi&it.* &eusin( e!istin( code re%oves code* &eusin( e!istin( code re%oves code redundanc and saves ti%e  %one*

redundanc and saves ti%e  %one*



 Co%%on co%ponents e!ist onl in Co%%on co%ponents e!ist onl in t#e Super Class and t#e Super Class and %aintained%aintained Centra&&.Centra&&.**



 Once a base class is )ritten and tested+ it Once a base class is )ritten and tested+ it need not be touc#ed a(ain* ,#isneed not be touc#ed a(ain* ,#is increases pro(ra%

(6)

Inheritance : $.nta and isibi&it.

CA$$ s%perc&ass 456I7ITIO7"

P8BIC $5CTIO7" P8BIC $5CTIO7" P%b&ic co9ponents P%b&ic co9ponents P+OT5CT54 $5CTIO7" P+OT5CT54 $5CTIO7" Protected co9ponents Protected co9ponents P+IAT5 $5CTIO7" P+IAT5 $5CTIO7" Private co9ponents Private co9ponents 574CA$$" 574CA$$"

CA$$ s%bc&ass 456I7ITIO7 I75+ITI7' 6+OM

s%perc&ass" s%perc&ass" P8BIC $5CTIO7" P8BIC $5CTIO7" P%b&ic co9ponents P%b&ic co9ponents P%b&ic co9ponents P%b&ic co9ponents !s%perc&ass# !s%perc&ass# P+OT5CT54 $5CTIO7" P+OT5CT54 $5CTIO7" Protected co9ponents Protected co9ponents Protected co9ponents Protected co9ponents !s%perc&ass# !s%perc&ass# P+IAT5 $5CTIO7" P+IAT5 $5CTIO7" Private section Private section 

 ,#e public and protected,#e public and protected

co%ponents o' t#e Super Class are co%ponents o' t#e Super Class are visible in t#e Sub Class*

visible in t#e Sub Class*



 Private section o' t#e Super Class isPrivate section o' t#e Super Class is not visible in t#e Sub Classes*

not visible in t#e Sub Classes*



 Private co%ponents o' t#e SubPrivate co%ponents o' t#e Sub Class can #ave sa%e na%e as t#e Class can #ave sa%e na%e as t#e private co%ponent o' t#e Super private co%ponent o' t#e Super Class*

Class*



 Public and Protected co%ponents o'Public and Protected co%ponents o' t#e Sub Class can not #ave t#e

t#e Sub Class can not #ave t#e

sa%e na%e as t#at #ave been used sa%e na%e as t#at #ave been used in Super Class*

(7)

Inheritance : Abstract c&asses and 9ethods

CA$$ c&s%per 456I7ITIO7"

P8BIC

P8BIC $5CTIO7"$5CTIO7"

M5TO4$:

M5TO4$: de9o1 de9o1 AB$T+AAB$T+ACT<CT<

de9o2"

574CA$$"

CA$$ c&s%b 456I7ITIO7

I75+ITI7' 6+OM c&s%per"

P8BIC

M5TO4$

M5TO4$ de9o1 de9o1 +5456I7ITIO7"+5456I7ITIO7"

574CA$$"



 A class de'in A class de'ined ased as AB$T+ACTAB$T+ACT cannot be cannot be instantiated + t#at is one cannot use

instantiated + t#at is one cannot use C+5AT5C+5AT5 OB=5CT

OB=5CT )it# re'erence to t#e class* )it# re'erence to t#e class*



 Abstract class can onl be accessed usin( its Abstract class can onl be accessed usin( its Static Co%ponents or its Sub Classes*

Static Co%ponents or its Sub Classes*



 Abstract class serves as a te%plate 'or Sub Abstract class serves as a te%plate 'or Sub Classes

Classes



 I' a class I' a class contains an abstract %et#od t#econtains an abstract %et#od t#e )#ole class beco%es abstract*

)#ole class beco%es abstract*



 A %et#o A %et#od+ )#ic# is abstract+ s#ould bed+ )#ic# is abstract+ s#ould be rede'ined in derived class*

rede'ined in derived class*



 An Ab An Abstract class can declare and i%ple%entstract class can declare and i%ple%ent non abstract %et#ods )#ic# its Sub Classes non abstract %et#ods )#ic# its Sub Classes can use )it# or )it#out rede'inin( t#e%*

can use )it# or )it#out rede'inin( t#e%*

+ede>inin the Abstract 9ethod o> +ede>inin the Abstract 9ethod o> $%per C&ass in the $%b C&ass

$%per C&ass in the $%b C&ass Abstract 9ethod

(8)

Inheritance : 6ina& c&asses and 9ethods



 A A >ina&>ina& class can not be class can not be inheritedinherited 'urt#er*

'urt#er*



 All Met#ods o' a All Met#ods o' a >ina&>ina& class areclass are in#erentl 'inal and %ust not be in#erentl 'inal and %ust not be declared as

declared as >ina&>ina& in t#e class in t#e class de'inition*

de'inition*



 A A >ina&>ina& %et#od can not be%et#od can not be rede>inedrede>ined 'urt#er*

'urt#er*



 I' a %et#od o' a non-'inal class is I' a %et#od o' a non-'inal class is 'inal'inal t#en t#at class can be in#erited but t#en t#at class can be in#erited but t#at %et#od cannot be rede'ined* t#at %et#od cannot be rede'ined*

CA$$

CA$$ >ina&c&ass 456>ina&c&ass 456I7ITIO7 I7ITIO7 6I7A"6I7A"

" " " " " " " "

574CA$$"

CA$$

CA$$ derivedc&ass derivedc&ass 456I7ITIO7456I7ITIO7

I75+ITI7' 6+OM >ina&c&ass "

"

" "" "" " " " " " " " " " " " " ""

574CA$$"

CA$$ s%perc&ass 456I7ITIO7 "

" " " " " " " "

M5TO4$

M5TO4$ >ina&9ethod >ina&9ethod 6I7A"6I7A"

574CA$$"

CA$$

CA$$ s%bc&ass s%bc&ass 456I7ITIO7 456I7ITIO7 I75+ITI7'I75+ITI7'

6+OM s%perc&ass "

"

" "" "" " " " " " " " " " " " " ""

M5TO4$

M5TO4$ >ina&9ethod >ina&9ethod rede>inition"rede>inition"

574CA$$"

(9)

Inheritance : $tatic co9ponents



 ,#e,#e p%b&icp%b&ic and and protectedprotected static static

co%ponents 1%et#ods  attributes3 o' co%ponents 1%et#ods  attributes3 o' t#e Super Class are visible in t#e Sub t#e Super Class are visible in t#e Sub Class*

Class*



 Public static co%ponents can bePublic static co%ponents can be accessed t#rou(# t#e class

accessed t#rou(# t#e class

co%ponent selector used )it# an co%ponent selector used )it# an class in t#e respective pat# o'

class in t#e respective pat# o' in#eritance tree*

in#eritance tree*

CA$$ basec&ass 456I7ITIO7"

P8BIC $5CTIO7"

CA$$-4

CA$$-4AATTA A : : na9e na9e TP5 $T+I7'TP5 $T+I7'

A

A85 85 ABAP"ABAP"

DDD""

574CA$$"

CA$$

I75+ITI7' 6+OM basec&ass"

" " "" "" " " " " " " " " " " " " "" 574CA$$" 574CA$$" $TA+T-O6-$55CTIO7" $TA+T-O6-$55CTIO7" basec&assEFna9e" basec&assEFna9e" derivedc&assEFna9e" derivedc&assEFna9e" $tatic co9ponent $tatic co9ponent

$tatic co9ponent is accessed $tatic co9ponent is accessed thro%h c&ass co9ponent

thro%h c&ass co9ponent

se&ector >ro9 the derived c&ass se&ector >ro9 the derived c&ass as Ge&& as >ro9 the base c&ass as Ge&& as >ro9 the base c&ass

(10)

Inheritance : Method +ede>inition



 +ede>inition+ede>inition is )#en t#e is )#en t#e

i%ple%entation o' an in#erited i%ple%entation o' an in#erited instance

instance %et#od is c#an(ed 'or t#e %et#od is c#an(ed 'or t#e Sub Class )it#out c#an(in( its

Sub Class )it#out c#an(in( its si(nature*

si(nature*



 $tatic 9ethods cant be rede>ined$tatic 9ethods cant be rede>ined**



 ,#e para%eters re%ain sa%e in t#e,#e para%eters re%ain sa%e in t#e derived class as it )as in base class* derived class as it )as in base class*



 In t#e rede'ined %et#od use tIn t#e rede'ined %et#od use t#e#e $8P5+

$8P5+ pseudo re'erence to access pseudo re'erence to access t#e ori(inal %et#od o' t#e base class* t#e ori(inal %et#od o' t#e base class*

P8BIC $5CTIO7"

M5TO4$:

M5TO4$: 9eth"9eth"

" " " " " " " "

574CA$$"

CA$$

CA$$ derivedc&ass derivedc&ass 456I7ITIO7 456I7ITIO7 I75+ITI7'I75+ITI7'

6+OM basec&ass "

P8BIC

M5TO4$:

M5TO4$: 9eth 9eth +5456I7ITIO7"+5456I7ITIO7"

"

" "" "" " " " " " " " " " " " " ""

574CA$$"

CA$$ derivedc&ass IMP5M57TATIO7 "

M5TO4$ 9eth"

CA$$

CA$$ M5TO4 M5TO4 $8P5+-F9eth"$8P5+-F9eth"

DDD DDD 574M5TO4" 574M5TO4" 574CA$$" 574CA$$"

+ede>inin the base c&ass 9ethod in the +ede>inin the base c&ass 9ethod in the

derived c&ass derived c&ass

Ca&&in the $%per C&ass 9ethod %sin Ca&&in the $%per C&ass 9ethod %sin

$8P5+ He.Gord $8P5+ He.Gord

(11)

Inheritance : Instance Constr%ctors



 As all public and protected As all public and protected

co%ponents+ Sub Class in#erits t#e co%ponents+ Sub Class in#erits t#e constructor %et#od i' it is present in constructor %et#od i' it is present in t#e in#eritance tree*

t#e in#eritance tree*



 I' an object o' Sub Class I' an object o' Sub Class is createdis created at t#is ti%e t#e in#erited instance at t#is ti%e t#e in#erited instance attributes and private attributes o' attributes and private attributes o' t#e Super Classes %ust also be t#e Super Classes %ust also be initiali/ed*

initiali/ed*



 As t#e private attributes o' t#e As t#e private attributes o' t#e Super Class is not visible to Sub Super Class is not visible to Sub Class+ Sub Class cannot 'ull Class+ Sub Class cannot 'ull

initiali/e its Super Class* ,#ere'ore initiali/e its Super Class* ,#ere'ore to ensure co%plete initiali/ation o' to ensure co%plete initiali/ation o' Sub Class and its Super Classes+ Sub Class and its Super Classes+ constructor is called*

constructor is called*

P8BIC $5CTIO7"

M5TO4$: constr%ctor

M5TO4$: constr%ctor IMPO+TI7' IMPO+TI7' ar1 ar1 TP5 TP5 $T+I7'"$T+I7'"

P+IA

P+IAT5 T5 $5CTIO$5CTIO7"7"

4AT

4ATA: A: >&d >&d TP5 TP5 $T+I7$T+I7'"'"

" "

" " " " " " " " " " " "" "

574CA$$"

CA$$

CA$$ derivedc&ass 456I7ITIO7 derivedc&ass 456I7ITIO7 I75+ITI7' 6+OMI75+ITI7' 6+OM

basec&ass "

P8BIC

M5TO4$:

M5TO4$: constr%ctor constr%ctor IMPO+TI7' IMPO+TI7' ar1 ar1 TP5 TP5 $T+I7'$T+I7'

ar2

ar2 TP5 TP5 $T+I7'"$T+I7'"

P+IA

P+IAT5 T5 $5CTIO$5CTIO7"7"

4AT

4ATA: A: >&d >&d TP5 TP5 $T+I7$T+I7'"'"

" "

" " " " " " " " " " " "" "

574CA$$"

CA$$ derivedc&ass

CA$$ derivedc&ass IMP5M57TAIMP5M57TATIO7 "TIO7 "

M5TO4$ constr%ctor"

CA

CA M5TO4 $8P5+-Fconstr%ctor M5TO4 $8P5+-Fconstr%ctor

5PO+TI7'

5PO+TI7' ar1 ar1 E E ar1"ar1"

>&d E

>&d E ar2 "ar2 "

DDD DDD 574M5TO4" 574M5TO4" 574CA$$" 574CA$$"

$%per C&ass constr%ctor $%per C&ass constr%ctor

$%b C&ass constr%ctor $%b C&ass constr%ctor

Ca&&in $%per C&ass Ca&&in $%per C&ass

constr%ctor constr%ctor

(12)

Inheritance : Instance Constr%ctors !Contd"#



 #et#er e!pli#et#er e!plicit call is re.uired cit call is re.uired 'or t#e instance constructor 'or t#e instance constructor o' t#e Super Class o' t#e Super Class oror not + )#en )e instantiate an object o' Sub Class is depends on t#e 'ollo)in(

not + )#en )e instantiate an object o' Sub Class is depends on t#e 'ollo)in( conditions4 conditions4 5p&icit constr%ctor is 5p&icit constr%ctor is de>ined in $%per de>ined in $%per C&assJ C&assJ 5p&icit constr%ctor is 5p&icit constr%ctor is de>ined in $%b C&assJ de>ined in $%b C&assJ

5p&icit ca&& reK%iredJ

5 5oo 55oo 5o5o 6 6eess 55oo 5o5o 5 5oo 66eess 6e6ess 6 6eess 66eess 6e6ess

(13)

Inheritance : $tatic Constr%ctors



 ,#e rede'inition o' static constructor,#e rede'inition o' static constructor )ors si%ilarl to instance

)ors si%ilarl to instance constructor*

constructor*



 #en an static constructor is#en an static constructor is rede'ined t#en &898$I5I,IO5 rede'ined t#en &898$I5I,IO5 addition is not re.uired*

addition is not re.uired*



 5o para%eter inter'ace is possible '5o para%eter inter'ace is possible 'oror static constructor 1 )it# or )it#out

static constructor 1 )it# or )it#out in#eritance3

in#eritance3



 ,#e runti%e environ%ent,#e runti%e environ%ent

auto%aticall ensures t#at t#e static auto%aticall ensures t#at t#e static constructors are called in t#e ri(#t constructors are called in t#e ri(#t order+

order+ so it is so it is not re.uired to call t#enot re.uired to call t#e static constructor o' t#e Super Class static constructor o' t#e Super Class e!plicitl*

e!plicitl*

CA$$ basec&ass

CA$$ basec&ass 456I7ITI456I7ITIO7"O7"

P8BIC $5CTIO7"

M5TO4$:

M5TO4$: c&assconsc&assconstr%ctor"tr%ctor"

P+IAT

P+IAT5 5 $5C$5CTIO7"TIO7"

4AT

4ATA: A: >&d >&d TP5 TP5 $T+I7$T+I7'"'"

"

" " " " " " " " " " " " " ""

574CA$$"

CA$$

I75+ITI

I75+ITI7' 6+OM 7' 6+OM basec&ass "basec&ass "

P8BIC

M5TO4$:

M5TO4$: c&assconstr%cc&assconstr%ctor tor ""

P+IAT

P+IAT5 5 $5CTI$5CTIO7"O7"

4AT

4ATA: A: >&d >&d TP5 TP5 $T+I7$T+I7'"'"

"

" " " " " " " " " " " " " ""

574CA$$"

CA$$ derivedc

CA$$ derivedc&ass IMP&ass IMP5M57TA5M57TATIO7 "TIO7 "

M5TO4$ c&assconstr%ctor" M5TO4$ c&assconstr%ctor" >&d E >&d E   I I a9 s%b a9 s%b "" DDD DDD 574M5TO4" 574M5TO4" 574CA$$" 574CA$$"

$%per C&ass constr%ctor $%per C&ass constr%ctor

$%b C&ass constr%ctor $%b C&ass constr%ctor

7o ca&& >or $%per C&ass 7o ca&& >or $%per C&ass constr%ctor

(14)

Inheritance : Object +e>erences

P%b: a1< a2 P%b: a1< a2 Prot: Prot: b1< b1< b2b2 Priv:c1<c2 Priv:c1<c2 C&ass C1 C&ass C1 P%b: a1< a2<a3<a P%b: a1< a2<a3<a Prot: Prot: b1<b2<b3<bb1<b2<b3<b Priv: c3<c Priv: c3<c

C&ass C2 Inheritin >ro9 C1

P%b: a1<

P%b: a1< a2<a3<a<a,<a/a2<a3<a<a,<a/

Prot: Prot: b1< b1< b2<b3<b<b,<b/b2<b3<b<b,<b/ Priv:c,<c/ Priv:c,<c/ 4ATA ore>1 TP5 +56 TO C1" 4ATA ore>1 TP5 +56 TO C1" C+5AT

C+5AT5 OB=5C5 OB=5CT ore>1"T ore>1"

4ATA ore>2 TP5 +56 TO C2" 4ATA ore>2 TP5 +56 TO C2"

C+5AT5 OB=5CT ore>2" C+5AT5 OB=5CT ore>2"

4ATA ore>3 TP5 +56 TO C3" 4ATA ore>3 TP5 +56 TO C3"

C+5AT

C+5AT5 OB=5C5 OB=5CT ore>3"T ore>3" C&ass C3 Inheritin >ro9 C2

(15)

Inheritance : Object +e>erences !Contd"#

9A,A 4 ore': ,6P8 &8$ ,O C:+ 9A,A 4 ore': ,6P8 &8$ ,O C:+

ore';

ore'; ,6P8 ,6P8 &8$ &8$ ,O ,O C;*C;*

C&8A,8 OBJ8C, ore';* C&8A,8 OBJ8C, ore';* ore': < ore';* ore': < ore';* ore': -=a:* ore': -=a:* ore': -=a>* ore': -=a>* OL OL 5rror 5rror P%b: a1< a2 P%b: a1< a2 Prot: Prot: b1< b1< b2b2 Priv:c1<c2 Priv:c1<c2 C&ass C1 C&ass C1 P%b: a1< a2<a3<a P%b: a1< a2<a3<a Prot: Prot: b1<b2<b3<bb1<b2<b3<b Priv: c3<c Priv: c3<c

P%b: a1<

P%b: a1< a2<a3<a<a,<a/a2<a3<a<a,<a/

Prot:

Prot: b1< b1< b2<b3<b<b,<b/b2<b3<b<b,<b/

Priv:c,<c/

C&ass C3 Inheritin >ro9 C2  &e'erence variables declared )it# re'erence to&e'erence variables declared )it# re'erence to a Super Class 1includin( a abstract class 3 can a Super Class 1includin( a abstract class 3 can point to an object o' a Sub Class

point to an object o' a Sub Class but canbut can on&.on&. access the co9ponents o> the object that access the co9ponents o> the object that is HnoGn to the

(16)

Inheritance : Object +e>erences !Contd"#

9A,A 4 ore': ,6P8 &8$ ,O C:+ 9A,A 4 ore': ,6P8 &8$ ,O C:+

ore';

ore'; ,6P8 ,6P8 &8$ &8$ ,O ,O C;*C;* C&8A,

C&8A,8 OBJ8C, ore': ,6P8 8 OBJ8C, ore': ,6P8 C;*C;* C&8A,

C&8A,8 OB8 OBJ8C, ore';*J8C, ore';*

ore': < ore';* ore': < ore';* ore': -=a:* ore': -=a:* ore': -=a>* ore': -=a>* OL OL OL OL P%b: a1< a2 P%b: a1< a2 Prot: Prot: b1< b1< b2b2 Priv:c1<c2 Priv:c1<c2 C&ass C1 C&ass C1 P%b: a1< a2<a3<a P%b: a1< a2<a3<a Prot: Prot: b1<b2<b3<bb1<b2<b3<b Priv: c3<c Priv: c3<c

P%b: a1<

P%b: a1< a2<a3<a<a,<a/a2<a3<a<a,<a/

Prot:

Prot: b1< b1< b2<b3<b<b,<b/b2<b3<b<b,<b/

Priv:c,<c/

4.na9ic T.pe 4.na9ic T.pe $tatic T.pe $tatic T.pe

(17)

$tatic  d.na9ic T.pe >or +e>erence



 ,#e Static tpe o' ,#e Static tpe o' a re'erence variable4a re'erence variable4



 Is deter%ined usin( ,6P8 &8$ ,OIs deter%ined usin( ,6P8 &8$ ,O 

 &e%ains constant t#rou(# t#e pro(ra% &e%ains constant t#rou(# t#e pro(ra% runrun



 ,#e 9na%ic tpe o' a re'erence variable4,#e 9na%ic tpe o' a re'erence variable4



 Is deter%ined b assi(n%entIs deter%ined b assi(n%ent 

 Can c#an(e durin( pro(ra% runCan c#an(e durin( pro(ra% run

4ATA : ore>1 TP5 +56 TO C1< 4ATA : ore>1 TP5 +56 TO C1< ore>2 ore>2 TP5 TP5 +56 +56 TO TO C2<C2< ore>3 ore>3 TP5 TP5 +56 +56 TO TO C3"C3"

C+5AT5 OB=5CT ore>1 TP5 C2"

C+5A

C+5AT5 OB=5CT orT5 OB=5CT ore>3"e>3"

ore>1 E ore>3"

$tatic T.pe >or ore>1 is C1 $tatic T.pe >or ore>1 is C1

4.na9ic t.pe >or ore>1 is noG C2 4.na9ic t.pe >or ore>1 is noG C2

4.na9ic t.pe >or ore>1 is noG C3 4.na9ic t.pe >or ore>1 is noG C3



 In assi(n%ents o' re'erenceIn assi(n%ents o' re'erence variables +

variables + static t.pestatic t.pe o' a o' a re'erence variable is al)as re'erence variable is al)as 9ore enera& than the

9ore enera& than the d.na9ic t.pe

(18)

Inheritance : 7arroGin Cast

4ATA : ore>1 TP5 +56 TO $%per C&ass<

ore>2

ore>2 TP5 TP5 +56 +56 TO TO $%b $%b C&ass"C&ass"

ore>1 E ore>2"



 #en static tpe o' t#e tar(et variable#en static tpe o' t#e tar(et variable is %ore (eneral t#an t#e static tpe o' is %ore (eneral t#an t#e static tpe o' t#e source variable+ since t

t#e source variable+ since t#e dna%ic#e dna%ic tpe o' t#e source variable at run ti%e tpe o' t#e source variable at run ti%e can onl be %ore speciali/ed t#an its can onl be %ore speciali/ed t#an its static tpe+ t#is can be c

static tpe+ t#is can be c#eced durin(#eced durin( t#e snta! c#ec* ,#is is no)n as t#e snta! c#ec* ,#is is no)n as narroGin cast or %p cast"

narroGin cast or %p cast"



 A tp A tpical use o' narro)inical use o' narro)in( cast is to( cast is to prepare 'or

prepare 'or eneric accesseneric access* A user* A user )#o is not at all interested in t#e 'iner )#o is not at all interested in t#e 'iner points o' t#e instances o' t#e

points o' t#e instances o' t#e SubSub Classes+ but )ants to access t#e Classes+ but )ants to access t#e (eneric co%ponents 'or all o' t#e%+ (eneric co%ponents 'or all o' t#e%+ could use t#e Super Class re'erence to could use t#e Super Class re'erence to access all o' t#e% in t#e sa%e )a* access all o' t#e% in t#e sa%e )a*

7arroGin Cast 7arroGin Cast

(19)

Inheritance : Nidenin Cast

4ATA : ore>1 TP5 +56 TO $%per C&ass<

ore>2

ore>2 TP5 TP5 +56 +56 TO TO $%b $%b C&ass<C&ass<

ore>3

ore>3 TP5 TP5 +56 +56 TO TO $%b $%b C&ass"C&ass"

ore>2 E ore>1" ore>2 E ore>1" ore>1 E ore>2" ore>1 E ore>2" T+" T+" ore>3 JE ore>1" ore>3 JE ore>1" CA

CATC C$MOTC C$MO5CA$T5++O+"5CA$T5++O+"

 +eact on the Cast 5rror

574T+"



 #en static tpe o' t#e tar(et variable#en static tpe o' t#e tar(et variable is %ore speciali/ed t#an t#e static tpe is %ore speciali/ed t#an t#e static tpe o' t#e source

o' t#e source variable* ,#is is no)nvariable* ,#is is no)n as

as Gidenin cast or doGn cast"Gidenin cast or doGn cast"



 ,#e )idenin( cast in t#e later case,#e )idenin( cast in t#e later case does not cause an error because t#e does not cause an error because t#e re'erence ore': actuall points to an re'erence ore': actuall points to an instance in t#e Sub Class* 1ore': < instance in t#e Sub Class* 1ore': < ore';3

ore';3



 A tp A tpical use 'or )idenin( ical use 'or )idenin( cast is )#encast is )#en speci>ic

speci>ic co%ponents o' instancesco%ponents o' instances need to be addressed and t#eir need to be addressed and t#eir

re'erences are ept in variables t#at re'erences are ept in variables t#at are tped on t#e Super Class*

are tped on t#e Super Class*

$.nta $.nta 5rror Occ%rs 5rror Occ%rs Nidenin Cast Nidenin Cast

(20)

Inheritance : Po&.9orphis9

CA$$ s%perc&ass 456I7ITIO7"

" " " " " " " " " " " " " " " " " " " " M5TO4$ test9ethod" M5TO4$ test9ethod" 574CA$$" 574CA$$"

CA$$ s%bc&assone 456I7ITIO7 I75+ITI7'

6+OM s%perc&ass"

" " " " " " " " "

M5TO4$ test9ethod +5456I7TIO7"

574CA$$"

CA$$ s%bc&asstGo 456I7ITIO7 I75+ITI7'

6+OM s%perc&ass"

" " " " " " " " "

M5TO4$ test9ethod +5456I7TIO7"

574CA$$"

4ATA: s%probj t.pe re> to s%perc&ass<

s%b1obj t.pe re> to s%bc&assone<

s%b2obj t.pe re> to s%bc&asstGo"

$TA+T-O6-$55CTIO7"

C+5AT

C+5AT5 OB=5CT 5 OB=5CT s%b1obj"s%b1obj"

C+5AT

C+5AT5 OB=5CT 5 OB=5CT s%b2obj"s%b2obj"

s%probj E s%b1obj"

CA

CA M5TO4 M5TO4 s%probj-Ftest9ethod"s%probj-Ftest9ethod"

s%probj E s%b2obj"



 &e'erence variables declared )it# static&e'erence variables declared )it# static re'erence to a Super Class can

re'erence to a Super Class can dna%icall point to an object o' a

dna%icall point to an object o' a SubSub Class o' t#is Super Class and access Class o' t#is Super Class and access t#et#e co%ponents no)n to t#e Super Class* co%ponents no)n to t#e Super Class* Met#ods in#erited 'ro% Super Class %a Met#ods in#erited 'ro% Super Class %a be rede'ined in one or %ore o'

be rede'ined in one or %ore o' t#e Subt#e Sub Classes* ,#is is t#e basis o'

Classes* ,#is is t#e basis o' pol%orp#i

pol%orp#is% s% usin( in#eritance*usin( in#eritance*



 Pol%orp#is% #ere %eans usin( t#ePol%orp#is% #ere %eans usin( t#e sa%e na%e via sa%e inter'ace to sa%e na%e via sa%e inter'ace to uni'or%l address

uni'or%l address di''erentldi''erentl

i%ple%ented %et#ods+ belon(in( to i%ple%ented %et#ods+ belon(in( to di''erent objects o' di''erent classes in di''erent objects o' di''erent classes in t#e in#eritance tree*

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4e9onstration

5ercise ,: 5ercise ,:



S#o)in( #o) In#eritance )ors )it# ABAP object*S#o)in( #o) In#eritance )ors )it# ABAP object*



Objectives:Objectives: 

9e'ine Sub Classes9e'ine Sub Classes 

(22)

4e9onstration

5ercise /: 5ercise /:

