About "IntersectWith" Method

Dim ckIntersect As Boolean
ckIntersect = cktest(objSS.Item(0), objSS.Item(1))
---------------------------------------------------------------------
Function cktest(objEnt1 As AcadEntity, objEnt2 As AcadEntity) As Boolean
Dim iPt As Variant
Dim intersect As Boolean
On Error Resume Next
With ThisDrawing.Utility

intersect = False

If Not IsNull(objEnt1.IntersectWith(objEnt2, acExtendNone)) Then intersect = True

If intersect = True Then
iPt = objEnt1.IntersectWith(objEnt2, acExtendNone)
.Prompt vbCrLf & "intersect point = " & iPt(0) & "," & iPt(1)
Else: .promt vbCrLf & "No intersect!"
End If

If Err Then .Prompt vbCrLf & "Error as " & Err.Description

cktest = intersect

End With
End Function
--------------------------------------------------------------------------
* When there is intersect.......
the intersect point can shown and cktest = True

* When there is no intersect....
no intersect point is shown but cktest = True
"Command: Error as Subscript out of range" is shown

 

From what I understand, you have to check for a UBound of less than 0. I
don't at all understand why this works this way, but that's what I've
gathered, so far. (I only recently tried this out, and do not have it in
production, yet, so I could certainly be mistaken.)

 

Hi~ TomD
Thanks for help, but how to check for a UBound?
Can you show me by examples?
Thanks a lot!

 

There is a bug in AutoCAD VBA Help's sample code for IntersectWith() method:

From sample code:

' Find the intersection points between the line and the circle
Dim intPoints As Variant
intPoints = lineObj.IntersectWith(circleObj, acExtendNone)

' Print all the intersection points
Dim I As Integer, j As Integer, k As Integer
Dim str As String
If VarType(intPoints) <> vbEmpty Then '' ========HERE IS THE
BUG===========
For I = LBound(intPoints) To UBound(intPoints)
str = "Intersection Point[" & k & "] is: " & intPoints(j) & ","
& intPoints(j + 1) & "," & intPoints(j + 2)
MsgBox str, , "IntersectWith Example"
str = ""
I = I + 2
j = j + 3
k = k + 1
Next
End If

The bug is that: IntersectWith() never returns a Variant of vbEmpty, it
returns an empty array of Double (that is UBound(returnVariant)=-1) if there
is no intersection, and returns an array of Double
(UBound(returnVariant)>=2), if there is 1 or more intersections.

So you need to check UBound() of returned variant to tell whether there is
intersection or not, as the other post suggested.

 

If Norman's post doesn't explain it enough, repost and I'll post a piece of
code I was using.

 

Norman

Thank you again~

anttam @w@

 

Hi! TomD

It's Ok, thanks!

anttam