如果 FOR EACH 循环中没有任何记录匹配，如何给出错误消息？答案

【问题标题】：How to give an error message if none of the records are matching in FOR EACH loop?如果 FOR EACH 循环中没有任何记录匹配，如何给出错误消息？
【发布时间】：2020-01-16 17:15:15
【问题描述】：

我编写了一个程序，用于在 FOR Each 循环中将一条记录与另一条记录进行匹配，但如果没有一条记录匹配，我不知道如何给出错误消息。让我分享我的代码

DEFINE VARIABLE cPos AS INTEGER NO-UNDO.
DEFINE TEMP-TABLE tt_data NO-UNDO
      FIELD cPosition AS CHARACTER FORMAT "X(60)"
      FIELD cEndCode  AS CHARACTER
      FIELD cShotCode AS CHARACTER.
/*so many records are stored in tt_data and below is one of the records for your understanding*/

CREATE tt_data.
ASSIGN
tt_data.cPosition ="S$$$^^^^^^^^^^$$$^^^MC^^^^^^^^^^^^R^^^^^^^^^^^^^^^^^^^^^^^^^"
tt_data.cEndCode =  10
tt_data.cShotCode = "S".

cPos = integer( tt_data.cEndCode / 10 ).

/* Consider 60 records available in tt_data */
FOR EACH tt_data.

     FIND FIRST tt_date WHERE tt_data.cShotCode =  
     SUBSTRING(tt_data.cPosition,cPos,1) NO-LOCK NO-ERROR. 

     DISPLAY tt_data.cShotCode. /* Displayed Value is S */

IF NOT AVAILABLE tt_date THEN
    MESSAGE "NONE OF THE RECORDS MATCHING WITH tt_data.cPosition "
    LEAVE.
END.

我可以在 tt_data 中获得至少一条记录匹配。这里的问题是，如果任何一条记录匹配，我不想离开，但如果没有记录匹配，我想用 LEAVE 语句收到错误消息。你能帮帮我吗？

【问题讨论】：

标签： openedge progress-4gl

【解决方案1】：

我认为这可能是你想要做的：

DEFINE VARIABLE cPos AS INTEGER NO-UNDO.
DEFINE TEMP-TABLE tt_data NO-UNDO
      FIELD cPosition AS CHARACTER FORMAT "X(60)"
      FIELD cEndCode  AS CHARACTER
      FIELD cShotCode AS CHARACTER.

/*so many records are stored in tt_data and below is one of the records for your understanding*/

CREATE tt_data.
ASSIGN
tt_data.cPosition ="S$$$^^^^^^^^^^$$$^^^MC^^^^^^^^^^^^R^^^^^^^^^^^^^^^^^^^^^^^^^"
tt_data.cEndCode =  10
tt_data.cShotCode = "S".

cPos = integer( tt_data.cEndCode / 10 ).

/* Consider 60 records available in tt_data */

FOR EACH tt_data:  /* although it 'works', "." is not appropriate, FOR EACH should end with a ":" */

    FIND FIRST tt_date WHERE tt_data.cShotCode = SUBSTRING(tt_data.cPosition,cPos,1) NO-LOCK NO-ERROR. 

    /* changes start here */

    IF AVAILABLE tt_date THEN
      do:
        DISPLAY tt_data.cShotCode. /* Displayed Value is S */ /* only display this when it is available! */
      end.
     else
      do:
        MESSAGE "NONE OF THE RECORDS MATCHING WITH tt_data.cPosition ".  /* a "." was missing */
        /* LEAVE. */ 
      end.

END.

【讨论】：

【解决方案2】：

我会亲自尝试在您进入 FOR EACH 块之前进行错误检查。有时您不能，但根据您的示例代码，我认为您可以先检查临时表并提供错误消息。但是根据示例，我不完全确定您要做什么。

DEFINE VARIABLE cPos AS INTEGER NO-UNDO.
DEFINE TEMP-TABLE tt_data NO-UNDO
      FIELD cPosition AS CHARACTER FORMAT "X(60)"
      FIELD cEndCode  AS CHARACTER
      FIELD cShotCode AS CHARACTER.
/*so many records are stored in tt_data and below is one of the records for your understanding*/

CREATE tt_data.
ASSIGN
tt_data.cPosition ="S$$$^^^^^^^^^^$$$^^^MC^^^^^^^^^^^^R^^^^^^^^^^^^^^^^^^^^^^^^^"
tt_data.cEndCode =  10
tt_data.cShotCode = "S".

cPos = integer( tt_data.cEndCode / 10 ).


/* Add check here */
IF can-find( FIRST tt_date WHERE 
                   tt_data.cShotCode = SUBSTRING(tt_data.cPosition,cPos,1 ) )
THEN
  message "ERROR message".

ELSE DO:
  /* Consider 60 records available in tt_data */
  FOR EACH tt_data.
    /* DO thing */
  END.
END.

【讨论】：