类的多态与重载

*----------------------------------------------------------------------*
*       CLASS superclass DEFINITION  定义基类
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS superclass DEFINITION.
  PUBLIC SECTION.
    DATA:para(30) TYPE c VALUE 'The Super method'.
    METHODS write_first.
ENDCLASS.                    "superclass DEFINITION

*----------------------------------------------------------------------*
*       CLASS subclass DEFINITION  定义派生类
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS subclass DEFINITION INHERITING FROM superclass.
  PUBLIC SECTION.
    METHODS write_first REDEFINITION. "定义重载方法
    METHODS write_second.
ENDCLASS.                    "subclass DEFINITION

*----------------------------------------------------------------------*
*       CLASS superclass IMPLEMENTATION
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS superclass IMPLEMENTATION.
  METHOD write_first.
    WRITE: / para.
  ENDMETHOD.                    "write_first
ENDCLASS.                    "superclass IMPLEMENTATION

*----------------------------------------------------------------------*
*       CLASS subclass IMPLEMENTATION
*----------------------------------------------------------------------*
*
*----------------------------------------------------------------------*
CLASS subclass IMPLEMENTATION.
  METHOD write_first.
    CALL METHOD super->write_first."调用基类的方法
  ENDMETHOD.                    "write_first
  METHOD write_second.
    para = 'The Redefinition method'.
    CALL METHOD me->write_first."调用本身类的方法
  ENDMETHOD.                    "write_second
ENDCLASS.                    "subclass IMPLEMENTATION

DATA:inher_obj TYPE REF TO subclass.

START-OF-SELECTION.
  CREATE OBJECT inher_obj.
  CALL METHOD:inher_obj->write_first,"调用派生类的重载方法
              inher_obj->write_second.