Progress ABL如何捕获UI事件触发错误并传递至主程序块

问题描述 #

在Progress ABL程序中存在如下场景：

• F6按键事件负责更新ttnom临时表数据
• fill_tt过程执行时如果检测到临时表为空，会抛出PROGRESS.lang.apperror('Temp-table is empty')异常
  需要确认是否可以让该异常从F6事件处理逻辑透传到程序主块，被主块的CATCH块捕获，而非在事件内部被拦截处理。

对应示例代码如下：

BLOCK-LEVEL ON ERROR UNDO, THROW.

DEFINE VARIABLE inomtr AS i NO-UNDO.
DEFINE VARIABLE lexit AS L NO-UNDO.

DEFINE TEMP-TABLE ttnom NO-UNDO 
  FIELD uid AS int64
INDEX idx1 IS unique uid.  

DEFINE FRAME fupd
SKIP(1)
inomtr FORMAT '>>>>>>>>>>>>9' NO-LABEL
SKIP(1)
WITH VIEW-AS DIALOG-BOX SIDE-LABELS.

 ON GO OF FRAME fupd
 DO:
   _t1:
   DO ON ERROR UNDO, RETURN NO-APPLY: 
     ASSIGN inomtr.
     IF CAN-FIND (FIRST ttnom NO-LOCK WHERE ttnom.uid = inomtr) THEN 
         LEAVE _t1.
     MESSAGE 'inomtr not found' VIEW-AS ALERT-BOX.
     RETURN NO-APPLY.    
   END.   
 END.
 
ON F3 OF inomtr IN FRAME fupd
DO:
  RUN choose_nom(OUTPUT inomtr).
END.

ON F6 of FRAME fupd ANYWHERE 
DO:
  DO ON ERROR UNDO, THROW  :
     RUN fill_tt.
     CATCH ERROR AS PROGRESS.lang.error:
        message error:GetMessage(1) + return-value VIEW-AS ALERT-BOX.
        lexit = YES.
        STOP.
     END CATCH.
  END.
  RETURN NO-APPLY.
END.

 
_tr:
DO ON ERROR UNDO, THROW
   ON STOP UNDO, LEAVE
   ON ENDKEY UNDO, LEAVE:

  RUN fill_tt.    
  DO WHILE TRUE ON ERROR UNDO, throw
                ON STOP UNDO , RETRY 
                ON ENDKEY UNDO , RETRY :
     IF RETRY OR lexit = yes THEN 
        DO:
          IF lexit = NO THEN 
             MESSAGE 'Exit?' VIEW-AS ALERT-BOX BUTTONS YES-NO UPDATE lexit.
          IF lexit = YES THEN 
             LEAVE _tr.    
        END.          
     DISPLAY  WITH FRAME fupd.
     ENABLE inomtr WITH FRAME fupd.

     WAIT-FOR GO OF FRAME fupd.

     RUN do_nomtr(inomtr).         
  END. 
  CATCH ERROR AS PROGRESS.lang.error:
     message ERROR:GetMessage(1) + RETURN-VALUE VIEW-AS ALERT-BOX.
  END CATCH.  
END.

PROCEDURE do_nomtr:
   DEFINE INPUT PARAM inomtr AS i NO-UNDO.

   MESSAGE inomtr VIEW-AS ALERT-BOX.
END PROCEDURE.

PROCEDURE fill_tt:
  DO ON ERROR UNDO, THROW:
     DISPLAY 'Loading temp-table' WITH FRAME ftt VIEW-AS DIALOG-BOX.
     EMPTY TEMP-TABLE ttnom.
     FOR EACH link NO-LOCK WHERE link.type = 3 AND link.class-code = '1B' AND 
                                 link.file-name = 'r-goods' AND link.arch = no ON ERROR UNDO, THROW:
                IF CAN-FIND(FIRST ttnom WHERE ttnom.uid = link.link-num) THEN 
                   NEXT.
                CREATE ttnom.
                ASSIGN ttnom.uid = link.link-num.                
     END.                                             

     HIDE  FRAME ftt NO-PAUSE.
     IF NOT TEMP-TABLE ttnom:HAS-RECORDS THEN 
        UNDO, THROW NEW PROGRESS.lang.apperror('Temp-table is empty').
  END.
END PROCEDURE.

核心结论 #

ABL的UI事件触发器运行在独立的UI消息循环调用栈上，原生不支持异常自动跨栈透传到WAIT-FOR所在的主块，但可以通过错误暂存+主动重抛的方式实现需求。原代码无法透传的原因有两个：

• F6事件块内部直接写了CATCH块拦截异常，且在块内执行STOP语句直接终止了错误传播流程
• 事件触发的调用栈和主块调用栈隔离，未捕获的事件异常默认会被UI运行时拦截，不会自动传到主块的CATCH

改造步骤 #

• 新增模块级错误变量，用于暂存事件处理过程中产生的异常

  DEFINE VARIABLE oEventError AS Progress.Lang.Error NO-UNDO.
  

• 改造F6事件块，移除内部直接弹框、STOP的处理逻辑，捕获异常后暂存到变量，标记退出状态即可

  ON F6 of FRAME fupd ANYWHERE 
  DO:
    DO ON ERROR UNDO, THROW  :
       RUN fill_tt.
       CATCH err AS PROGRESS.lang.error:
          oEventError = err.
          lexit = YES.
       END CATCH.
    END.
    RETURN NO-APPLY.
  END.
  

• 在主块WAIT-FOR语句执行完成后，立刻检查暂存的错误对象，如果存在有效错误则主动抛出，异常就会被主块的CATCH块统一捕获处理

  WAIT-FOR GO OF FRAME fupd.
  /* 主动重抛事件处理中产生的异常 */
  IF VALID-OBJECT(oEventError) THEN DO:
    UNDO, THROW oEventError.
  END.
  
  RUN do_nomtr(inomtr).
  

注意事项 #

• 不要在事件处理的CATCH块中使用STOP、RETURN ERROR这类会直接终止事件上下文的语句，否则异常会丢失
• 如果需要统一处理多个UI事件的错误，只需要让所有事件的CATCH块都把异常赋值给同一个oEventError变量即可
• 不要尝试给WAIT-FOR语句加ON ERROR UNDO, THROW来捕获事件异常，该配置仅能捕获WAIT-FOR语句本身的错误，无法捕获其派发的事件触发器内抛出的错误

内容的提问来源于stack exchange，提问作者Александр Овчинников