Error Handling

[ticad02]

I have lisp routines that set a variable for the user osnap settings. Different routines set different osnap settings then at the end of the routine it sets the osmode variable back to the user settings prior to running the command.

When a user hits escape (or doesn't select anything during the routine and hits enter to end it) the routine does not get to the end to reset osmode to original user settings. I hear something about error handling in a lisp routinein which if a routine doesn't finish it puts the settings back to how the were prior to running the command.

Can someone guide in how to write this in the lisp files.


Thank you all.

[rkmcswain]

To get started, open the Developer Help, search for "error handling", then find the topic "Using the *error* Function". If this doesn't get you started towards solving your issue, post back.

[ticad02]

I'm still unable to figure this one out. I even found a site that shows how to handle this exact problem, and I can't get the lisp to work right.

(defun *error* (msg)
(setvar "osmode" *osnap)
(princ msg)
(princ)
)

That's the code it tells me to write, but the osnap settings do not restore after an ESC cancel. I have *osnap set to read the users setting prior to the lisp changing osmode, and my lisp resets at the end if the lisp runs through properly. This works fine, but it still doesn't recall the user osmode setting after a cancel

I'm adding my lisp routine. In the lisp I've posted I use "useros" in place of *osnap.

[ticad02]

Sorry, the above posted lisp is the original...here's the one with the error handling code I can't get to work.

[_gile]

Hi,

You have to nest and declare local your *error* function

(defun MyFunction (/ *error* osnap)
  (defun *error* (msg)
    (setvar "osmode" *osnap)
    (princ msg)
    (princ)
  )
  (setq osnap (getvar "OSMODE"))
  ;; do your stuff changing osmode here
  (setvar "OSMODE" osnap)
  (princ)
)

[RobertB]

You have to nest and declare local your *error* function

(defun MyFunction (/ *error* osnap)
  (defun *error* (msg)
    (setvar "osmode" *osnap)
    (princ msg)
    (princ)
  )
  (setq osnap (getvar "OSMODE"))
  ;; do your stuff changing osmode here
  (setvar "OSMODE" osnap)
  (princ)
)

If you are going to go thru that amount of work, why not make the error routine also handle clean exits and dispense with the needlessly duplicated code? See the post here.

[_gile]

Nice way Robert, you mean something like this ?

(defun c:test (/ *error* osmode)
  (defun *error* (msg)
    (if (and msg
             (null (member msg '("Function cancelled" "quit / exit abort")))
        )
      (princ (strcat "\nError: " msg))
    )
    (setvar "osmode" osmode)
    (princ)
  )
  (setq osmode (getvar "OSMODE"))
  ;; do your stuff changing osmode here
  (*error* msg)
)