How to check whether entity's handle is valid?

Hi all,

I am getting error: bad argument type: lentityp by running following code:

(defun ATR ( handSTR)
 
 (if (HANDENT handSTR)
   (progn
     (setq ss1 (ssadd handSTR))
     (command ".attedit" "y" "*" "*" "*" ss1 "color" "t" "255,0,0" "n")
     (ssdel handSTR ss1)
   )
 )
 (princ)
)
(ATR "543B")

What am I doing wrong here?

_$ (handent nil)

Error: bad argument type: stringp nil
_1$ 

So use:

(and (eq 'STR (type handent)) (handent handSTR))

instead of:

(HANDENT handSTR)

EDIT: Oh, and the actual reason for the error:

Change:

 (setq ss1 (ssadd handSTR))

To:

(setq ss1 (ssadd (handent handSTR)))

I would also suggest testing whether (entget (handent )) returns a non-nil value (i.e. testing whether the entity is erased), as handent can return the entity name for entities for which the erase flag is set.

... Or use vlax-erased-p (faster than entget).

I also think that it would be good to include this part to the checklist (wrapped within and function):

(setq ss1 (ssadd (handent handSTR)))

And use progn for the command call and ssdel.

To account non-graphical entity's handles:

_$ (ssadd (handent (cdr (assoc 5 (entget (namedobjdict))))))
nil 

@Grrr:

(equal (namedobjdict) (handent (cdr (assoc 5 (entget (namedobjdict)))))) => T

I can't think of a scenario where I would want to add a non-graphical entity to a selection set.

@Grrr:

(equal (namedobjdict) (handent (cdr (assoc 5 (entget (namedobjdict)))))) => T

Overthinking.

I can't think of a scenario where I would want to add a non-graphical entity to a selection set.

We don't know how the OP collects the handles - so thats just small additional check, not a big deal and will evaluate anyways (with or without checking).

Thanks all for your kind help.

Problem resolved.