Handling type conversion errors

By default, in case of type conversion error or overflow errors, the program continues, the target variable is set to NULL and the global STATUS variable is not set.

In order to detect data conversion and overflow errors, use the WHENEVER ANY ERROR statement.

The next code example:

MAIN  -- DBDATE set to Y4MD-
  DEFINE v VARCHAR(50), d DATE
  LET v = "2012-99-99"      -- invalid date string
  LET d = v
  DISPLAY status, "/", NVL(d,"NULL")  -- displays 0/NULL
  WHENEVER ANY ERROR CONTINUE
  LET d = v
  DISPLAY status, "/", NVL(d,"NULL")  -- displays -1205/NULL
  WHENEVER ANY ERROR STOP
  LET d = "2012-11-23"  -- valid date, ok
  DISPLAY status, "/", NVL(d,"NULL")  -- displays 0/2012-11-23
  LET d = v   -- program execution stopped with error -1205
END MAIN

Above code will produce the following output:

          0/NULL
      -1218/NULL
Program stopped at 'x.4gl', line number 10.
FORMS statement error number -1218.
String to date conversion error.

Conversion and overflow errors are implicitly trapped in TRY/CATCH blocks.

In the next example, the INTERVAL variable is not large enough to hold the result of d2 - d1:

MAIN
  DEFINE d1, d2 DATETIME YEAR TO FRACTION(5)
  DEFINE i INTERVAL SECOND(2) TO SECOND
  LET d1 = "2015-11-06 17:40:21.436"
  LET d2 = "2015-11-06 10:40:21.436"
  TRY
      LET i = d2 - d1
  CATCH
      DISPLAY STATUS, " / ", err_get(STATUS)
  END TRY
END MAIN

Above code will produce the following output:

      -1265 / Overflow occurred on a datetime or interval operation.