Constructor in ABAP

DPM125 — Thu, 31 Jul 2025 20:15:51 +0000

A constructor is a special method automatically called when an object is created using CREATE OBJECT or NEW.

Types of Constructors in ABAP

Type	Method Name	Called On	Purpose
Instance Constructor	`CONSTRUCTOR`	When an object is created (`NEW` or `CREATE OBJECT`)	To initialize instance-specific data
Class Constructor	`CLASS_CONSTRUCTOR`	When the class is first used	To initialize class-level (static) data

REPORT zrep_lclclass.

CLASS zcl_demo DEFINITION.
  PUBLIC SECTION.
    METHODS: constructor,               " Instance constructor
             display_instance_value.

    CLASS-METHODS: class_constructor,  " Class constructor
                   display_class_value.

  PRIVATE SECTION.
    DATA: lv_instance_val TYPE string.
    CLASS-DATA: gv_class_val TYPE string.
ENDCLASS.

CLASS zcl_demo IMPLEMENTATION.

  " Instance Constructor
  METHOD constructor.
    lv_instance_val = 'Initialized in CONSTRUCTOR'.
    WRITE: / '>> Instance CONSTRUCTOR called'.
  ENDMETHOD.

  " Class Constructor
  METHOD class_constructor.
    gv_class_val = 'Initialized in CLASS_CONSTRUCTOR'.
    WRITE: / '>> CLASS_CONSTRUCTOR called (only once)'.
  ENDMETHOD.

  METHOD display_instance_value.
    WRITE: / 'Instance value:', lv_instance_val.
  ENDMETHOD.

  METHOD display_class_value.
    WRITE: / 'Class value:', gv_class_val.
  ENDMETHOD.

ENDCLASS.

START-OF-SELECTION.

* Access class method (triggers class constructor first time)
  zcl_demo=>display_class_value( ).

  SKIP.

* Create object (triggers instance constructor)
  DATA(lo_obj1) = NEW zcl_demo( ).
  lo_obj1->display_instance_value( ).

  SKIP.

* Create another object (instance constructor runs again, but not class constructor)
  DATA(lo_obj2) = NEW zcl_demo( ).
  lo_obj2->display_instance_value( ).

  SKIP.

* Access class method again (class constructor NOT triggered again)
  zcl_demo=>display_class_value( ).

Output:

What is the difference between static and instance Members in SAP OOABAP ?

DPM125 — Wed, 30 Jul 2025 17:30:46 +0000

Instance Members (Methods & Data)

Belong to individual objects (instances).
Created using DATA and METHODS.
Each object has its own copy of the data.
Accessed using the object reference: lo_obj->method_name.
Useful when each object should maintain its own state.
Destroyed when the object goes out of scope.

Static Members (Methods & Data)

Belong to the class itself, not any particular object.
Created using CLASS-DATA and CLASS-METHODS.
Only one copy exists for the entire class.
Accessed using the class name: zcl_class_name=>method_name.
Useful for shared data, like counters, configuration, or logging.
Exist as long as the class is loaded in memory.

*&---------------------------------------------------------------------*
*& Report  ZREP_LCLCLASS
*&
*&---------------------------------------------------------------------*
*&
*&
*&---------------------------------------------------------------------*

REPORT zrep_lclclass.

CLASS zcl_static_instance_demo DEFINITION.
  PUBLIC SECTION.
    " Instance attribute and method
    DATA: gv_instance_value TYPE i.
    METHODS: increase_instance_value.

    " Static attribute and method
    CLASS-DATA: gv_static_value TYPE i.
    CLASS-METHODS: increase_static_value.
ENDCLASS.

CLASS zcl_static_instance_demo IMPLEMENTATION.

  METHOD increase_instance_value.
    gv_instance_value = gv_instance_value + 1.
    WRITE: / 'Instance Value:', gv_instance_value.
  ENDMETHOD.

  METHOD increase_static_value.
    gv_static_value = gv_static_value + 1.
    WRITE: / 'Static Value:', gv_static_value.
  ENDMETHOD.

ENDCLASS.

START-OF-SELECTION.

  WRITE: / '--- Static Method Calls (No object needed) ---'.
  zcl_static_instance_demo=>increase_static_value( ). " 1
  zcl_static_instance_demo=>increase_static_value( ). " 2

  SKIP.

  WRITE: / '--- Instance Method Calls (Using object) ---'.
  DATA(lo_obj1) = NEW zcl_static_instance_demo( ).
  lo_obj1->increase_instance_value( ). " 1
  lo_obj1->increase_instance_value( ). " 2

  SKIP.

  WRITE: / '--- Another Object with Separate Instance ---'.
  DATA(lo_obj2) = NEW zcl_static_instance_demo( ).
  lo_obj2->increase_instance_value( ). " 1 (separate from lo_obj1)

  SKIP.

  WRITE: / '--- Static Again (Still shared) ---'.
  zcl_static_instance_demo=>increase_static_value( ). " 3

Output :

constructor – SAP EWM Help

Constructor in ABAP

What is the difference between static and instance Members in SAP OOABAP ?