Object Oriented ABAP Tutorial with Examples-3

Object Oriented ABAP Tutorials with Examples - 3, welcome to SAP ABAP Interview Questions. 





Here we sapabapiq.com presenting third post in the series of OOABAP Tutorials with examples. Before going to read this article please refer previous posts in this series of Object Oriented ABAP programming tutorials with examples.

Read

Object Oriented ABAP Turorial with Examples - 1

Read

OOABAP Programming Tutorial with Examples - 2

Object Oriented ABAP Tutorial with Examples - 3 

Place to put non-declarative statements
Theme	For a class, the IMPLEMENTATION section can immediately follow the class DEFINITION section.  If this is so, then all the non-declarative statements ( viz., processing statements outside any class definition/ implementation ) should be placed under a processing block, such as START-OF-SELECTION.
Program description	This program contains a class C1 with a method M1. In version 1, the IMPLEMENTATION part of the class follows the class definition section.  But, the non-declarative statements are not placed under any block. This creates a compilation error. In version 2, the non-declarative statements are not placed under the block START-OF-SELECTION. It gets correctly compiled. This demonstrates the theme.
Source Code of the OOABAP Program	REPORT YSUBDEL . class c1 definition. public section.  methods : m1 .  endclass.  class c1 implementation.   method : m1 .    write:/5 'I am method m1'.   endmethod.  endclass.  START-OF-SELECTION.  data : obj1 type ref to c1 .  create object obj1.   call method obj1->m1. ---------------------------------------- REPORT YSUBDEL . class c1 definition. public section.  methods : m1 .  endclass.  class c1 implementation.   method : m1 .    write:/5 'I am method m1'.   endmethod.  endclass.  data : obj1 type ref to c1 .  create object obj1.   call method obj1->m1. Version 1: Incorrect                                                            Version 2 : Correct
Output of the program	Version 1 creates compilation error. Version 2 gets correctly compiled.

Use of  Field Symbols in Class
Theme	Field Symbols can be used to contain value of any variable in a class.
Program Description	The program uses a field symbol, <FS>. It handles the values of instance attribute, inum and static attribute , onum.
Dump of the Program	REPORT YSUB_ASSIGN_FS. FIELD-SYMBOLS : <FS> TYPE ANY . class c1 definition .  public section . * Instance attribute : inum declared below   data : inum type i value 5 . * static attribute onum declared below    class-data : onum type i value 10 . endclass. class c1 implementation. endclass.  start-of-selection.   data : oref1 type ref to c1 .   create object oref1. * Assigning instance attribute to field symbol <fs>    assign oref1->inum to <fs> .   write:/5 <fs> . * Assigning static attribute to field symbol    assign oref1->onum to <fs> .   write:/5 <fs> .   assign c1=>onum to <fs> .   write:/5 <fs> .
Output	5 10 10

Use of Static Attributes
Theme	This program will demonstrate that : Static sttributes of a class are retained throughout the entire runtime. All the objects within a class can access its static attributes.
Program Description	The program contains a class C1 with static attribute : NUM . The method : M1 increments the static attribute by 1 and displays the value each time it is called. In the main START-OF-SELECTION  portion, two objects : OBJ1 and OBJ2 are created from class C1. First, static attribute : NUM is changed and accessed outside the class using the class component selector , ‘=>’. Then, both objects OBJ1 and OBJ2 are used to call method : M1 which shows the new value of static attribute : NUM . That the value of the static attribute gets incremented each time when the method M1 of different objects is called shows that this variable is able to retain its value through the entire runtime.
Dump of the program	report ysubdel. CLASS c1 DEFINITION .  PUBLIC SECTION.   CLASS-DATA : NUM TYPE I .   METHODS : M1. ENDCLASS. CLASS c1 IMPLEMENTATION.  METHOD m1 .    num = num + 1.    write:/5 num .  ENDMETHOD. ENDCLASS.  START-OF-SELECTION.    c1=>num = 3.    write:/5 c1=>num .   DATA : OREF1 TYPE REF TO C1 ,          OREF2 TYPE REF TO C1 .   CREATE OBJECT : OREF1 ,                   OREF2 .   CALL METHOD OREF1->M1 .   CALL METHOD OREF2->M1.
Output	3 4 5

We'll update next post in coming days on OOABAP Tutorials with Examples, keep visiting www.sapabapiq.com.

Object Oriented ABAP Turorial with Examples - 1

OOABAP Programming Tutorial with Examples - 2

"You found the information helpful and want to say thanks? Your donation is enough to inspire us to do more. Thanks a bunch!"

Posted in: ABAP Interview Questions, ABAP-Interview-Questions, Data-Dictionary, Module-Pool-Programming, Object Oriented ABAP, Object Oriented ABAP Interview Questions, Object-Oriented-ABAP-Interview-Questions, OOABAP, SAP ABAP Interview Questions, SAP ABAP Introduction, SAP Basics, SAP-Enhancements, SAP-Exits