REXX Tips & Tricks, Version 2.80


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Check if an object exist



There's no REXX function to check if an object exists. But if you know the 
object ID of the object you can use the code below to test if an object 
already exists. (see also List all WPS known object IDs) 


 
/* sample code to check if an object exists. Note that this code      */
/* works for objects with object IDs only!                            */

                        /* load the SysCreateObject function          */
  call rxFuncAdd "SysCreateObject", "REXXUTIL", "SysCreateObject"
                        /* load the SysDestroyObject function         */
  call rxFuncAdd "SysDestroyObject", "REXXUTIL", "SysDestroyObject"

  do until myInput = ""
    say "Enter the ID of the object to check (RETURN to exit): "
    myInput = strip( lineIn() )
    if myInput <> "" then
    do
      objectExist = ObjectExist( myInput )

      select
        when objectExist = 0 then
          say "The object """ || myInput || """ does not exist."

        when objectExist = 1 then
          say "The object """ || myInput || """ exist."

        otherwise
          say "Error """ || objectExist || """ executing ObjectExist!"

      end /* select */

    end /* if myInput <> "" then */
  end /* do until myInput = "" */

exit 0

/* ------------------------------------------------------------------ */
/* function: Check if an object with a given object ID exists         */
/*                                                                    */
/* Usage:    ObjectExist objectID                                     */
/*                                                                    */
/* where:    objectID = object ID of the object to test               */
/*                                                                    */
/* returns:  1 - the object exist                                     */
/*           0 - the object does not exist                            */
/*           else                                                     */
/*             error code of the SysCreateObject function             */
/*                                                                    */
ObjectExist: PROCEDURE
  parse arg objectID

                        /* init the return code                       */
  rc = 43               /* error code 43 = routine not found          */

                        /* install a local error handler              */
  SIGNAL ON SYNTAX NAME ObjectExistError

                        /* check the parameter                        */
  if substr( objectID, 2, 1 ) <> ":" then
    if left( objectID,1 ) <> "<" & right( objectID,1 ) <> ">" then
      objectID = "<" || objectID || ">"

                        /* try to create an object with this ID       */
  tempRC = SysCreateObject( "WPFolder"                     ,,
                            "TestObject"                   ,,
                            "<WP_NOWHERE>"                 ,,
                            "OBJECTID=" || objectID || ";" ,,
                            "FAIL" )

  if tempRC = 1 then
  do
                        /* object created, delete it                  */
    call SysDestroyObject objectID
    rc = 0              /* set return code to "Object does not exist" */
  end /* if tempRC = 1 then */
  else
    rc = 1              /* set return code to "Object does exist"     */

ObjectExistError:

RETURN rc


  

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