ABAP 面向对象系列之七

这一节我们将参照一个例子，介绍事件（event）的使用方法。

1．定义event

2．Set handler

3．Raise event

REPORT zbobo_events_5.

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

*       CLASS lcl_dog DEFINITION

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

CLASS lcl_dog DEFINITION.

  PUBLIC SECTION.

*   Declare events

    EVENTS:

      dog_is_hungry

        EXPORTING value(ex_time_since_last_meal) TYPE i.

    METHODS:

      constructor

          IMPORTING im_name TYPE string,

      set_time_since_last_meal

          IMPORTING im_time TYPE i,

      on_dog_is_hungry FOR EVENT dog_is_hungry OF lcl_dog

          IMPORTING ex_time_since_last_meal.

ENDCLASS.

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

*       CLASS lcl_dog IMPLEMENTATION

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

CLASS lcl_dog IMPLEMENTATION.

  METHOD constructor.

    WRITE: / 'I am a dog and my name is', im_name.

  ENDMETHOD.

  METHOD set_time_since_last_meal.

    IF im_time < 4.

      SKIP 1.

      WRITE: / 'You fool, I am not hungry yet'.

    ELSE.

*    Subsrcribe for event:

*    set handler <Event handler method>

*    FOR <ref_sender>!FOR ALL INSTANCES [ACTIVATION <var>]

      SET HANDLER on_dog_is_hungry FOR ALL INSTANCES ACTIVATION 'X'.

*    Raise event

      RAISE EVENT dog_is_hungry

        EXPORTING ex_time_since_last_meal = im_time.

    ENDIF.

  ENDMETHOD.

  METHOD on_dog_is_hungry.

*   Event method, called when the event dog_is_hungry is raised

    SKIP 1.

    WRITE: /  'You son of a bitch. I have not eaten for more than',

              ex_time_since_last_meal, ' hours'.

    WRITE: / 'Give me something to eat NOW!'.

  ENDMETHOD.

ENDCLASS.

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

*       R E P O R T

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

DATA: o_dog1 TYPE REF TO lcl_dog.

START-OF-SELECTION.

  CREATE OBJECT o_dog1 EXPORTING im_name = 'Beefeater'.

  CALL METHOD o_dog1->set_time_since_last_meal

    EXPORTING im_time = 2.

* This method call will raise the event dog_is_hungy

* because time > 3

  CALL METHOD o_dog1->set_time_since_last_meal

    EXPORTING im_time = 5.