[求助]：[0211]如何判断交点计算模式?

xyz518mm

[求助]：[0211]如何判断交点计算模式?

想使用下面程式来完成交点计算,
若是两物件有相交,则不用使用延伸,
但若两物件无相交,则要延伸两物件.

问题:在于该怎样使用 IF 来判断执行
因为我在两物件无相交的情况下,执行结果回应了
_$ ; 错误: ActiveX 伺服器回覆一个错误讯息: 无效的索引。
我想可能是在判断 vlax-safearray->list 值时,出现问题.


(SETQ En1 (car (ENTSEL "\n 选取物件 A")))
(SETQ En2 (car (ENTSEL "\n 选取物件 B")))
(SETQ VEn1 (VLAX-ENAME->VLA-OBJECT En1 ))
(SETQ VEn2 (VLAX-ENAME->VLA-OBJECT En2 ))

(IF (= (vlax-safearray->list (VLAX-VARIANT-VALUE
        (VLA-INTERSECTWITH Ven1 Ven2 acExtendNone) ))
        T )
(SETQ INT (vlax-safearray->list (VLAX-VARIANT-VALUE
          (VLA-INTERSECTWITH Ven1 Ven2 acExtendNone) )) )
(SETQ INT (vlax-safearray->list (VLAX-VARIANT-VALUE
          (VLA-INTERSECTWITH Ven1 Ven2 acExtendBoth) )) )
)

烦请各位高手可以帮忙解答一下
谢谢...

Underway

请看前辈的忠告

Tony Tanzillo  Nov 25 1999, 4:00 pm  
Newsgroups: autodesk.autocad.customization
Subject: Re: line inters polyline

Well - I Agree that vla-intersectwith should not return
empty safearrays if there is no intersection, it should
return a variant of type :vlax-vbEmpty, because that's
how other ActiveX clients would expect a 'null' result
to be represented (I haven't checked what the VBA/ActiveX
counterpart returns, but it should be an emptpy variant).

Most would probably prefer (vla-intersectwith) to return
nil when there's no intersection, but this method is just
a 'wrapper' for the underlying ActiveX method, and there
is no translation between LISP and ActiveX types done, I
think for a good reason: because it would result in a lot
of inconsistency.


So, it's probably a good thing that all ActiveX functions
behave in a *consistent* way, and do not attempt to cast
their results or output to LISP types