invalid use of incomplete type ‘class vtkPolyData’

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1

Hello everyone,

I would like to test whether an array is present in a polydata, but I am getting this error at compile time:

NicocoTest.cxx:10:39: error: invalid use of incomplete type ‘class vtkPolyData’
   if (reader.GetPointer()->GetOutput()->GetPointData()->HasArray("ARRAYNAME")) {
                                       ^~
In file included from NicocoTest.cxx:1: VTK-8.2.0/IO/Legacy/vtkPolyDataReader.h:37:7: note: forward declaration of ‘class vtkPolyData’
 class vtkPolyData;
       ^~~~~~~~~~~

Here is the source code leading to this hard-to-understand-for-c++-noob error:

#include "vtkPolyDataReader.h"
#include "vtkNew.h"

int main(int argc, char *argv[]) {
  std::cout << "Reading file" << std::endl;
  
  vtkNew<vtkPolyDataReader> reader;
  reader->SetFileName(argv[1]);

  if (reader.GetPointer()->GetOutput()->GetPointData()->HasArray("ARRAYNAME")) {
    std:cout << "An array named ARRAYNAME was found" << std::endl;
  }

  return EXIT_SUCCESS;
}

What am I doing wrong? What would be the correct way of avoid this error?

Thank you very much.

2

I think you’ll have to

#include “vtkPolyData.h”

3

Nicoco, after

reader->SetFileName(argv[1]);

insert the line

reader->Update();

This method is necessary to actually perform the reading and update correctly reader->GetOutput().

One question: what are you going to do with reader->GetOutput() ?
Maybe, you could do something like (this will copy your data):

vtkNew< vtkPolyData > polyData;
polyData->DeepCopy(reader->GetOutput());

Or simply

vtkSmartPointer< vtkPolyData > polyData = reader->GetOutput(); // No copy here

And then use the object ’ polyData’ for the rest of your processing / visualization pipeline.

Hope this help.

    Luca
4

Thank you for your help. Unfortunately, this does not solve the compile-time issue at all. I first tried just adding include. Here is what the code looks like now:

#include "vtkPolyDataReader.h"
#include "vtkNew.h"
#include "vtkPolyData.h"

int main(int argc, char *argv[]) {
  std::cout << "Reading file" << std::endl;
  
  vtkNew<vtkPolyDataReader> reader;
  reader->SetFileName(argv[1]);
  reader->Update();

  vtkSmartPointer< vtkPolyData > polyData = reader->GetOutput();

  int hasArray = polyData->GetPointData()->HasArray("ARRAYNAME");

  if (hasArray) {
    std:cout << "An array named ARRAYNAME was found" << std::endl;
  }

  return EXIT_SUCCESS;
}

and the error:

NicocoTest.cxx: In function ‘int main(int, char**)’:
NicocoTest.cxx:14:42: error: invalid use of incomplete type ‘class vtkPointData’
   int hasArray = polyData->GetPointData()->HasArray("ARRAYNAME");
                                          ^~
In file included from VTK-8.2.0/Common/DataModel/vtkPointSet.h:33,
                 from Common/DataModel/vtkPolyData.h:62,
                 from NicocoTest.cxx:3:
VTK-8.2.0/Common/DataModel/vtkDataSet.h:52:7: note: forward declaration of ‘class vtkPointData’
 class vtkPointData;
       ^~~~~~~~~~~~
make[2]: *** [nicoco/CMakeFiles/NicocoTest.dir/build.make:63: nicoco/CMakeFiles/NicocoTest.dir/NicocoTest.cxx.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:1233: nicoco/CMakeFiles/NicocoTest.dir/all] Error 2
make: *** [Makefile:95: all] Error 2

What I am trying to achieve seems so basic…

5

This error pretty much always means that header inclusions are missing. In VTK, the header name is (in the vast majority of cases) classname.h, so here, adding #include "vtkPointData.h" would make the class declaration available.

1 Like
6

Thank you very much @ben.boeckel

That was it!