[vtkusers] Python wrapping a custom class

[Kit Chambers]

Hi David/VTK'ers, 

Following on from my previous email i am now having diffcultly using a more complicated data structure in a derived class. In this case i am trying:

#include "vtkImageData.h"
#include <boost/python.hpp>

class VTK_EXPORT vtkImageDataDict: public vtkImageData
{
public:

  vtkTypeMacro(vtkImageDataDict, vtkImageData);

  // New method
  static vtkImageDataDict *New();

  // Python dictionary
  boost::python::dict m_dict;

  // test function to set the dictionary
  void test_set_dict();

  // prints the dictionary
  void printImageDict();

  // Dictionary getter
  boost::python::dict getDict(){return this->m_dict;}

  // Dictionary setter
  void setDict(boost::python::object dd);
};


When I wrap the above class the test_set_dict and printImageDict work fine but the wrapper seems to ignore getDict()
and setDict(). I assume this is because vtkWrapperPython does not know what to do with boost::python objects. Maybe I am going about this the wrong way? I did try doing the wrapping through boost python rather than VTK but found I ran into compilation issues. 

Any help would be very much appreciated. 

Kit




> On 29 Jul 2016, at 17:07, David Gobbi <david.gobbi at gmail.com> wrote:
> 
> Hi Kit,
> 
> It's most likely because the class is missing vtkTypeMacro:
> 
> vtkTypeMacro(vtkNewData, vtkImageData);
> 
>  - David
> 
> 
> On Fri, Jul 29, 2016 at 9:02 AM, Kit Chambers <kit.chambers.kc at gmail.com <mailto:kit.chambers.kc at gmail.com>> wrote:
> Hi,
> 
> I am trying to wrap a custom class derived from vtkImageData in python. And it works except for when i try to access my custom methods. For example:
> 
> import vtkNewDataPython as idp
> 
> mydata = idp.vtkNewData()
> 
> print "\nvtkImageData functionality"
> mydata.SetDimensions(2,3,1)
> dims = mydata.GetDimensions()
> print "image dimensions =",dims
> print "Number of points: ",mydata.GetNumberOfPoints()
> print "Number of cells: ",mydata.GetNumberOfCells()
> 
> print "\ncustom functionality" 
> mydata.set_myvalue()
> print "Myvalue = ", mydata.get_myvalue()
> 
> 
> Produces:
> vtkImageData functionality
> image dimensions = (2, 3, 1)
> Number of points:  6
> Number of cells:  2
> 
> custom functionality
> Traceback (most recent call last):
>   File "./pytest.py", line 14, in <module>
>     mydata.set_myvalue()
> AttributeError: set_myvalue
> 
> 
> Basically it is doing just fine up until I try to call a custom method
> 
> The class looks like this:
> 
> #include "vtkImageData.h"
> 
> class VTK_EXPORT vtkNewData: public vtkImageData
> {
> public:
>   static vtkNewData *New();
>   void set_myvalue(){
> 	  this->myvalue=3;
>   }
>   int get_myvalue(){
> 	  return this->myvalue;
>   }
>   int myvalue;
> };
> 
> 
> The CmakeLists.txt is adapted mostly from https://github.com/paulmelis/vtk-wrapping-example <https://github.com/paulmelis/vtk-wrapping-example> and looks like this
> 
> 
> #######################################
> # Pre-requisites
> 
> # C++11 flags
> set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -std=c++11")
> 
> # VTK
> find_package(VTK REQUIRED
>                 vtkCommonCore
>                 vtkCommonDataModel
>                 vtkWrappingPythonCore                  
>             )
> include(${VTK_USE_FILE})
> 
> # Python and vtk wrapping
> find_package(PythonLibs 2.7 EXACT REQUIRED)
> include(vtkWrapPython)
> include_directories("${PYTHON_INCLUDE_PATH}")
> 
> #######################################
> # Building vtkNewData
> add_library(vtkNewData SHARED vtkNewData.cxx)
> TARGET_LINK_LIBRARIES(vtkNewData ${VTK_LIBRARIES} )
> if(APPLE) 
>     set_target_properties(vtkNewData PROPERTIES SUFFIX ".so")
> endif()
> 
> #######################################
> # Wrapping vtkNewData
> vtk_wrap_python3(vtkNewDataPython vtkNewDataPython_SRCS vtkNewData.cxx)
> 
> add_library(vtkNewDataPythonD ${vtkNewDataPython_SRCS} vtkNewData.cxx)
> target_link_libraries(vtkNewDataPythonD         
>         ${VTK_LIBRARIES}
>         vtkWrappingPythonCore 
>         ${VTK_PYTHON_LIBRARIES})
> 
> add_library(vtkNewDataPython MODULE vtkNewDataPythonInit.cxx)
> 
> set(VTK_MODULES_USED vtkCommonDataModel vtkCommonCore) 
> set(VTK_PYTHOND_LIBS)
> foreach(TMP_LIB ${VTK_MODULES_USED})
>    set(VTK_PYTHOND_LIBS ${VTK_PYTHOND_LIBS} ${TMP_LIB}PythonD)
> endforeach()  
> 
> target_link_libraries(vtkNewDataPython vtkNewDataPythonD ${VTK_PYTHOND_LIBS})
> 
> set_target_properties(vtkNewDataPython PROPERTIES PREFIX "")
> if(WIN32 AND NOT CYGWIN)
>     set_target_properties(vtkNewDataPython PROPERTIES SUFFIX ".pyd")
> endif(WIN32 AND NOT CYGWIN)
> 
> 
> I suspect there is something very simple I am missing here but cannot for the life of me think what. Any help would be appreciated.
> 
> 
> Cheers
> 
> Kit
> 

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