All Methods of Interface must be Implemented

A class which defines an Interface must implement all of its methods. If any method is missing in the implementation of that class then a compile error will come.

Below is a program where we have defined an Interface in which we declare attribute and methods meth1 and meth2. Now after defining the Interface in a class we implement only one method meth1. When we compile this program a syntax error comes with message implementation is missing for method meth2 as follows.

Here if we implement the second method then it successfully runs and produces the proper output.

*&---------------------------------------------------------------------*

*& Report  ZSR_TEST

*&

*&---------------------------------------------------------------------*

*&

*&

*&---------------------------------------------------------------------*

REPORT  zsr_test.

*----------------------------------------------------------------------*

*       INTERFACE it

*----------------------------------------------------------------------*

*

*----------------------------------------------------------------------*

INTERFACE it.

  DATA v_txt TYPE char50.

  METHODS: meth1, meth2.

ENDINTERFACE.                    "it

*----------------------------------------------------------------------*

*       CLASS cls DEFINITION

*----------------------------------------------------------------------*

*

*----------------------------------------------------------------------*

CLASS cls DEFINITION.

  PUBLIC SECTION.

    INTERFACES it.

ENDCLASS.                    "cls DEFINITION

*----------------------------------------------------------------------*

*       CLASS cls IMPLEMENTATION

*----------------------------------------------------------------------*

*

*----------------------------------------------------------------------*

CLASS cls IMPLEMENTATION.

  METHOD it~meth1.

    it~v_txt = 'First Interface Method'.

    WRITE / it~v_txt.

  ENDMETHOD.                                                "it~meth1

  METHOD it~meth2.

    it~v_txt = 'Second Interface Method'.

    WRITE / it~v_txt.

  ENDMETHOD.                                                "it~meth2

ENDCLASS.                    "cls IMPLEMENTATION

START-OF-SELECTION.

  DATA obj TYPE REF TO cls.

  CREATE OBJECT obj.

  CALL METHOD: obj->it~meth1,

               obj->it~meth2.

The output is following: