Ah, fantastic! I was going to post the same issue here, but have been
just swamped at work. My work-around was to add all found shapes
temporarily to a *TopTools_SequenceOfShape*, but the *ReInit()* way is
much less of a hack.
By the way, the same issue happens when using *TopoDS_Iterator*, but it
does not seem to have a ReInit method? E.g. here is how I currently work
around this issue:
def GetShapeChildren(s):
children = {}
it = TopoDS_Iterator(s)
totChildren = 0
aSeq = TopTools_SequenceOfShape()
while it.More():
totChildren += 1
ss = it.Value()
aSeq.Append(ss)
ss = aSeq.Value(aSeq.Length())
stChildren = children.setdefault(subType, [])
if ss not in stChildren:
stChildren.append(ss)
it.Next()
return children
Any ideas?
- Frank
At the end of the iteration, e.g. when ex.More() is False, the
TopExp_Explorer instance is cleared (with the Clear() method). Then all
the references to subshapes are lost and your list contains NULL elements.
What's the correct way to store a references to sub-Shapes? I guess I
need a shallow copy of the shape-object returned by Explorer.Current()
but I can't figure how to achieve this.
You just have to ReInit() the TopExp_Explorer instance at the end of the
loop.
Here is the corrected code:
from OCC import TopExp, BRepPrimAPI, TopAbs, TopoDS
box = BRepPrimAPI.BRepPrimAPI_MakeBox(10., 20., 30.)
ex = TopExp.TopExp_Explorer(box.Shape(), TopAbs.TopAbs_EDGE)
results = []
while ex.More():
edge = TopoDS.TopoDS().Edge(ex.Current())
print "is null?", bool(edge.IsNull())
results.append(edge)
ex.Next()
ex.ReInit() #to avoid loosing reference to objects found in the loop
for edge in results:
print "null now?", bool(edge.IsNull())
cheers,
Cheers,
Bryan
Thomas
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