The vl-catch-all-apply function allows you to intercept errors returned by ActiveX methods, and decide how the program should continue.
(defun init-motivate () (vl-load-com) (setq mspace (vla-get-modelspace (vla-get-activedocument (vlax-get-acad-object)) ) ) (vla-addray mspace (vlax-3d-point 0 0 0) (vlax-3d-point 1 1 0)) )
(defun bnddrop (/ bbox) (setq bbox (vla-getboundingbox (vla-item mspace (- 1 (vla-get-count mspace))) 'll 'ur ) ) (list "Do something with bounding box." bbox) )
Because a Ray object extends to infinity, it is not possible to enclose it with a box, and GetBoundingBox results in the following error:
; error: Automation Error. Invalid extents
If this code were part of your application program, execution would halt at this point.
(defun bndcatch (/ bbox) (setq bbox (vl-catch-all-apply 'vla-getboundingbox (list (vla-item mspace (- 1 (vla-get-count mspace))) 'll 'ur ) ) ) (if (vl-catch-all-error-p bbox) (list "Exception: " (vl-catch-all-error-message bbox)) (list "Do something with bounding box." bbox) ) )
This function uses vl-catch-all-apply to call vla-getboundingbox. It passes vl-catch-all-apply two arguments: the symbol naming the function being called ('vla-getboundingbox) and a list of arguments to be passed to vla-getboundingbox. If the GetBoundingBox method completes successfully, vl-catch-all-apply stores the return value in variable bbox. If the call is unsuccessful, vl-catch-all-apply stores an error object in bbox.
A call to vl-catch-all-error-p checks the return value from vl-catch-all-apply and returns T if it is an error object, nil otherwise. If the return value is an error object, as it would be in this example, the function issues vl-catch-all-error-message to obtain the message from the error object. Program execution continues from this point.