strange error when deleting objects

[Jan Stifter]

hi vtk users,
in an object called ViewItemObject, i have the following pipeline:

vtkSTLReader
   ¦
vtkPolyData *myData (needed for filters, ...)
   ¦
vtkNormalsFilter
   ¦
vtkPolyDataMapper
   ¦
vtkActor
   ¦

the object ViewItemObject has many instances. i connect the actors together
in a vtkAssembly. Everything works fine, until I want to delete all objects.
sometimes it works, sometimes not.

in the destructor of this object, i delete first the vtkActor, then
vtkPolyDataMapper, vtkNormalsFilter, vtkPolyData and then the program
crashes:

   if (myActor)         { myActor->Delete ();         }
   if (myMapper)        { myMapper->Delete ();        }
   if (myNormalsFilter) { myNormalsFilter->Delete (); }
   if (myData)          { myData->Delete();           }
   if (mySTLReader)     { mySTLReader->Delete ();     }  // here we crash

the program crashes, when i call "mySTLReader->Delete();"

any hints are greatly appreciated

jan




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