for 循环中的 ABAP 方法调用

Question

ABAP 新手。我有一个 class "Truck" ("vrachtwagen")，它有一个 table 属性 it_pakket（货车上的包裹）。我写了一个方法来将这个 table 的内容写入屏幕（DisplayLading）。我想为每辆卡车执行此操作，因此我在 for 循环中调用此方法。程序运行没有错误，但输出没有显示在屏幕上。

REPORT ZPR412_OO_OEF1.

CLASS CPakket DEFINITION.
    PUBLIC SECTION.
      DATA: Id TYPE I READ-ONLY,
            aantal TYPE I,
            bestemmeling TYPE STRING.
      METHODS: SetID IMPORTING ID TYPE I.
ENDCLASS.

CLASS CPakket IMPLEMENTATION.
  METHOD SetID.
    me->Id = ID.
  ENDMETHOD.
ENDCLASS.

CLASS CVrachtwagen DEFINITION.
  PUBLIC SECTION.
    DATA: Id TYPE I READ-ONLY.
    METHODS: SetID IMPORTING ID TYPE I,
             LaadPakket IMPORTING Pakket TYPE REF TO CPakket,
             LosPakket IMPORTING Pakket TYPE REF TO CPakket,
             DisplayLading.
  PRIVATE SECTION.
    DATA: it_pakket TYPE STANDARD TABLE OF REF TO CPakket,
          pakket TYPE REF TO CPakket.
ENDCLASS.

CLASS CVrachtwagen IMPLEMENTATION.
  METHOD SetID.
    me->Id = ID.
  ENDMETHOD.
  METHOD LaadPakket.
    APPEND Pakket TO it_pakket.
  ENDMETHOD.
  METHOD LosPakket.
  ENDMETHOD.
  METHOD DisplayLading.
    LOOP AT me->it_pakket into pakket.
      WRITE:/ pakket->Id, pakket->aantal, pakket->bestemmeling.
    ENDLOOP.
  ENDMETHOD.
ENDCLASS.

DATA:
  vrachtwagen TYPE REF TO CVrachtwagen,
  it_vrachtwagens TYPE STANDARD TABLE OF REF TO CVrachtwagen,
  pakket TYPE REF TO CPakket,
  it_pakket TYPE STANDARD TABLE OF REF TO CPakket,
  s TYPE string.

start-of-selection.
DO 2 TIMES.
  CREATE OBJECT vrachtwagen.
  CALL METHOD vrachtwagen->SetId EXPORTING Id = sy-index.
  APPEND vrachtwagen TO it_vrachtwagens.
ENDDO.

CREATE OBJECT pakket.
CALL METHOD pakket->SetId EXPORTING Id = 1.
pakket->aantal = 5.
pakket->bestemmeling = 'Bob'.
APPEND pakket TO it_pakket.

CREATE OBJECT pakket.
CALL METHOD pakket->SetId EXPORTING Id = 2.
pakket->aantal = 2.
pakket->bestemmeling = 'Jan'.
APPEND pakket TO it_pakket.

CREATE OBJECT pakket.
CALL METHOD pakket->SetId EXPORTING Id = 3.
pakket->aantal = 1.
pakket->bestemmeling = 'Piet'.
APPEND pakket TO it_pakket.

LOOP AT it_vrachtwagens INTO vrachtwagen.
  CASE sy-index.
    WHEN 1.
      loop at it_pakket into pakket.
        if sy-index lt 3.
          vrachtwagen->LaadPakket( pakket ).
        endif.
      endloop.
    WHEN 2.
      read table it_pakket into pakket index 3.
      vrachtwagen->LaadPakket( pakket ).
  ENDCASE.
ENDLOOP.
LOOP AT it_vrachtwagens INTO vrachtwagen.
  vrachtwagen->DisplayLading( ).
ENDLOOP.

我编写了代码来用包裹装满卡车，并将卡车添加到我循环的内部 table。我的猜测是CVrachtwagen class实现中的write方法无法写入屏幕，因为程序还在运行循环?

Answer 1

系统变量 SY-INDEX 未在 LOOP AT 循环内设置，您需要在 it_vrachtwagens 和 [=14= 的循环内将其替换为 SY-TABIX ].

来自 SAP's documentation（帮助不大）：

sy-index - 循环索引。在 DO 和 WHILE 循环中，包含先前循环次数，包括当前次数。

sy-tabix - 内部 table 的 table 索引中的行号。包含使用主索引或辅助索引 table 访问的最后一行。使用哈希算法访问时设置为 0。

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