====== Trapping Message Calls=====

^Published By^Date^Version^Knowledge Level^Keywords^
|Sprezzatura Ltd|01 JAN 1990|1.15+|EXPERT|MESSAGE, MSG|

Sean Leyne from Michael D. Atkin & Associates Ltd wrote to us recently,
commenting as follows

"I was very interested/impressed with your solution to the message B234
problem. However, I thought that a more general solution could be created to
handle trapping of all unwanted messages."

"The code (MSG) that follows can accomplish this goal without modifying
object code. Another benefit of this routine is for the handling of
multi-lingual applications by allowing for multiple versions of a message to
be stored in the messages file, displayed depending on the language
preferred. The enclosed routine could be modified, keeping the following in
mind

  - Labelled Common Variables\\ - Language Prefix (ie F - French)\\ - Message File Variable (for READ statement)
  - A Pre-Display check for message existing where 

<code>
                TEMP.ID = PARM1:PREFIX

                READ TEMP FROM MESSAGE.FILE,TEMP.ID THEN
                     PARM1 := PREFIX
                END
</code>

"The benefit of such a routine is that it prevents the messages from being
overwritten by RTI upgrades." With Sean's permission I reproduce below his
code listing.

<code>
     0001 SUBROUTINE MSG(PARM1,PARM2,PARM3,PARM4)
     0002 *
     0003 * Copyright Michael D Atkin & Associates Ltd 1989, permission
     0004 *           granted for REVMEDIA subscribers to use this program
     0005 *           for any purpose.
     0006 *
     0007 *           No liability is accepted for use
     0008 *
     0009 * Author    Sean J. Leyne
     0010 *
     0011 * Purpose   This subroutine traps all calls to the system MSG
     0012 *           (renamed MSG.RTI). The routine compares the message
     0013 *           number against a list to be excluded, if found a
     0014 *           defined label is assigned to PARM3 (IMAGE) for later
     0015 *           evaluation and the call to MSG.RTI is ignored.
     0016 *
     0017 *           Remember, with each upgrade there is a possibility of
     0018 *           $MSG being overwritten. Therefore care must be taken
     0019 *           to check after each upgrade
     0020 *
     0021 *           Finally, for speed and code overhead purposes, compile
     0022 *           the code using the (CL) option
     0023 *
     0024
     0025 DECLARE FUNCTION UNASSIGNED
     0026
     0027 * Check if parameters assigned, important for later evaluation
     0028
     0029 IF UNASSIGNED(PARM1) THEN PARM1 = ""
     0030 IF UNASSIGNED(PARM2) THEN PARM2 = ""
     0031
     0032 EXCLUDE.LIST = "B234"
     0033 FOUND = 0
     0034
     0035 IF PARM1 THEN
     0036   LOCATE PARM1 IN EXCLUDE.LIST USING "," SETTING POS THEN
     0037      FOUND = 1
     0038   END ELSE
     0039      FOUND = 0
     0040   END
     0041 END
     0042
     0043 BEGIN CASE
     0044   CASE FOUND
     0045      * Message was found in exclude list, load PARM3, ignore call
     0046      PARM3 = "NO SHOW"
     0047   CASE PARM3 = "NO SHOW"
     0048      * Being asked to remove message never displayed. Ignore call
     0049      PARM3 = ""
     0050   CASE 1
     0051      CALL MSG.RTI(PARM1,PARM2,PARM3,PARM4)
     0052 END CASE
     0053
     0054 RETURN
</code>

(Volume 1, Issue 8, Pages 10,11)