custom properties

[orange47631686]

I wish to add custom properties for pline called 'doublelength'=length*2 please tell me can it be done?

[ketxu]

oh, you must have knowing about Xdata to do it.You can find it's infomation with Google ^^
Or use that simple example not use vla :

;;;;;;;;This to get Xdata infor
(defun X_DATA_GET (EN APID / EL)
  (setq EL (entget EN (list APID)))
  (cdadr (assoc -3 EL)) ;;return only data items
)

; This  add extended data list DLST with
;;             application name APID to the entity list
;;             of entity name EN.
;;             Overwrites existing.
;;
(defun X_DATA_ADD (EN APID DLST / EL TMP1)
   (if (null (tblsearch "APPID" APID)) ;;registered?
      (regapp APID)) ;;register it
   (setq EL (entget EN) ;;get Entity list
         TMP1 (list -3 (cons APID DLST))
   )
   (if (< (xdsize TMP1) (xdroom EN)) ;;got enough room?
      (entmod (append EL (list TMP1)))) ;;modify database
)

;;;;;This to get Pline length
(defun Length1(e) (vlax-curve-getDistAtParam e (vlax-curve-getEndParam e)))

;;Now go to use :
;Add doublelength to Pline that you select
(X_data_add (setq en (car(entsel))) "Doublelength" (list (cons 1040 (* 2 (length1 en)) )))

;Read infor later :
(cdr(assoc 1040  (x_data_get (car(entsel)) "Doublelength")))

[dgorsman]

Not easily... it may be simpler to just get the length and multiply it by 2. Unless you are talking about adding it to the Properties palette?

[orange47631686]

@dgorsman well, I want more than that. for eg I'd like to have a property called 'signal_decrease'=length*attenuation, where 'attenuation' is another property
@thattinh thanks. but I need it to change instantly, the same way 'length' does.
meaning, if I extend the pline, it automatically updates, without the need to start lisp script manually.

[Tom Beauford]

@dgorsman well, I want more than that. for eg I'd like to have a property called 'signal_decrease'=length*attenuation, where 'attenuation' is another property
@thattinh thanks. but I need it to change instantly, the same way 'length' does.
meaning, if I extend the pline, it automatically updates, without the need to start lisp script manually.

Have you looked at the '= geometric constraint'? Only thing close to what you're asking for that I can think of.