Events: Introductory Example
The following simple example shows the principle of events within ABAP Objects. It is based on the Simple Introduction to Classes . An event critical_value is declared and triggered in class counter.
REPORT demo_class_counter_event.
CLASS counter DEFINITION.PUBLIC SECTION. METHODS increment_counter. EVENTS critical_value EXPORTING value(excess) TYPE i. PRIVATE SECTION. DATA: count TYPE i, threshold TYPE i VALUE 10.ENDCLASS.
CLASS counter IMPLEMENTATION. METHODS increment_counter. DATA diff TYPE i. ADD 1 TO count. IF count > threshold. diff = count - threshold. RAISE EVENT critical_value EXPORTING excess = diff. ENDIF.ENDMETHOD.ENDCLASS.
CLASS handler DEFINITION.PUBLIC SECTION. METHODS handle_excess FOR EVENT critical_value OF counter IMPORTING excess.ENDCLASS.
CLASS handler IMPLEMENTATION. METHOD handle_excess. WRITE: / 'Excess is', excess.ENDMETHOD.ENDCLASS.
DATA: r1 TYPE REF TO counter, h1 TYPE REF TO handler.
START-OF-SELECTION.
CREATE OBJECT: r1, h1.
SET HANDLER h1->handle_excess FOR ALL INSTANCES.
DO 20 TIMES. CALL METHOD r1->increment_counter.ENDDO.
The class counter implements a counter. It triggers the event critical_value when a threshold value is exceeded, and displays the difference. handlercan handle the exception in counter. During runtime, the handler is registered for all reference variables that point to the object.