topic Re: Hook methods in ABAP Objects in Application Development and Automation Discussions

Hook methods in ABAP Objects

Former Member — Wed, 09 Aug 2006 08:00:30 GMT

Hello,

i discovered that method calling in the class-inheritance of ABAP Objects doesn't work similar to other OO languages.

Example:

1 Superclass named "Z_CLASS"

1 Subclass of "Z_CLASS" named "Z_SUB"

Z_CLASS defines a method "initialize" and has a constructor which calls "initialize".

Z_SUB redefines the method "initialize" assigning some values to instance-attributes.

If i instantiate a new "Z_SUB"-object then the contructor of "Z_CLASS" is called which calls ITS OWN "initialize" not the one of the subclass. For comparison: Java would call the initialize of the subclass.

I have to implement a constructor in every subclass of "Z_CLASS" which calls the super constructor and the own "initialize" after that to solve this problem. This isn't the proper OO way!

Did i miss something or am i right?

Thanks in advance,

Stefan

Re: Hook methods in ABAP Objects

Former Member — Wed, 09 Aug 2006 09:56:59 GMT

Check out this, it might be helpfull...

----

INTERFACE I_COUNTER

----

INTERFACE i_counter.

METHODS: initialize.

ENDINTERFACE.

----

CLASS C_COUNTER1 DEFINITION

----

CLASS c_counter1 DEFINITION.

PUBLIC SECTION.

INTERFACES i_counter.

METHODS: constructor.

DATA count TYPE i.

ENDCLASS.

----

CLASS C_COUNTER1 IMPLEMENTATION

----

CLASS c_counter1 IMPLEMENTATION.

METHOD constructor.

CALL METHOD me->i_counter~initialize.

ENDMETHOD.

METHOD i_counter~initialize.

count = count + 10.

write:/ 'count from super', count.

ENDMETHOD.

ENDCLASS.

----

CLASS C_COUNTER2 DEFINITION

----

CLASS c_counter2 DEFINITION INHERITING FROM c_counter1.

PUBLIC SECTION.

METHODS: constructor,

initialize.

DATA count1 TYPE i.

ENDCLASS.

----

CLASS C_COUNTER2 IMPLEMENTATION

----

CLASS c_counter2 IMPLEMENTATION.

METHOD constructor.

CALL METHOD super->constructor.

CALL METHOD me->initialize.

ENDMETHOD.

METHOD initialize.

count = ( count / 10 ).

write:/ 'count from sub', count.

ENDMETHOD.

ENDCLASS.

DATA: count TYPE REF TO c_counter2.

START-OF-SELECTION.

CREATE OBJECT count TYPE c_counter2.

Re: Hook methods in ABAP Objects

Former Member — Wed, 09 Aug 2006 10:52:15 GMT

Thanks for your answer Kesava.

in your example the subclass "c_counter2" calls the initialize in its own constructor instead of being called by the superclass.

*---------------------------------------------------------------------*
* CLASS C_COUNTER2 IMPLEMENTATION
*---------------------------------------------------------------------*
CLASS c_counter2 IMPLEMENTATION.
METHOD constructor.
CALL METHOD super->constructor.
CALL METHOD me->initialize.
ENDMETHOD.

i want the superclass to call "initialize" and automatically delegate this to the subclass which implements the initialize on its own. this is a common behaviour in OO.

my example would be:


*---------------------------------------------------------------------*
* CLASS Z_CLASS DEFINITION
*---------------------------------------------------------------------*
CLASS Z_CLASS DEFINITION.
PUBLIC SECTION.
METHODS: constructor, initialize.
DATA inittest TYPE string.
ENDCLASS.

*---------------------------------------------------------------------*
* CLASS Z_CLASS IMPLEMENTATION
*---------------------------------------------------------------------*
CLASS Z_CLASS IMPLEMENTATION.
METHOD constructor.
	initialize( ).
ENDMETHOD.
METHOD initialize.
	inittest = 'Superclass'.
ENDMETHOD.
ENDCLASS.

*---------------------------------------------------------------------*
* CLASS Z_SUB DEFINITION
*---------------------------------------------------------------------*
CLASS Z_SUB DEFINITION INHERITING FROM Z_CLASS.
PUBLIC SECTION.
METHODS: initialize redefinition.
ENDCLASS.

*---------------------------------------------------------------------*
* CLASS Z_SUB IMPLEMENTATION
*---------------------------------------------------------------------*
CLASS Z_SUB IMPLEMENTATION.

METHOD initialize.
	inittest = 'Subclass'.
ENDMETHOD.
ENDCLASS.


DATA: test TYPE REF TO z_sub.
START-OF-SELECTION.

CREATE OBJECT test.
write test->inittest.

but this doesn't initialize the subclass with the string 'Subclass'

Re: Hook methods in ABAP Objects

Former Member — Wed, 09 Aug 2006 11:03:32 GMT

Hi Stefan,

What you say is right but there are so many things in OOABAP that are not so 'OOPS'ish..:).For now, the programmer should take the pains of making OOABAP work on the lines of JAVA like langueages..

Regards,

Ravi

Re: Hook methods in ABAP Objects

Former Member — Wed, 09 Aug 2006 11:09:34 GMT

OK, thanks,

i just wanted to know that i wasnt doing things wrong. This means i'll work around this.

So... now i should check out how the reward points work