View source for Deriving from vtkAlgorithm

This example demonstrates how to derive from vtkAlgorithm to set a custom output type for a filter. vtkTest is a class that simply stores a double named Value. vtkTestReader is a class whose GetOutput() function returns a vtkTest.

This example is currently broken - vtkDataObject has a function DATA_TYPE_NAME () which is used when calling 
info->Set(vtkDataObject::DATA_TYPE_NAME(), "vtkTest" );
However, since test is derived from vtkObject, DATA_TYPE_NAME() is not available. How do you call info->Set() with a vtkObject?

==Example.cxx==
<source lang="cpp">
#include <vtkSmartPointer.h>

#include "vtkTestReader.h"
#include "vtkTest.h"

int main (int argc, char *argv[])
{
  if(argc != 2)
    {
    vtkstd::cout << "Required arguments: Filename" << vtkstd::endl;
    exit(-1);
    }
    
  vtkstd::string InputFilename = argv[1];
  
  vtkSmartPointer<vtkTestReader> reader = vtkSmartPointer<vtkTestReader>::New();
  reader->Update();
  
  vtkTest* test = reader->GetOutput();
  vtkstd::cout << "Value: " << test->GetValue() << vtkstd::endl;
  
  return 0;
}

</source>

==vtkTest.h==
<source lang="cpp">

#ifndef __vtkTest_h
#define __vtkTest_h

#include "vtkObject.h"

class vtkInformation;
class vtkInformationVector;

class vtkTest : public vtkObject
{
public:
  vtkTypeRevisionMacro(vtkTest,vtkObject);
  void PrintSelf(ostream& os, vtkIndent indent);

  static vtkTest *New();
  	
  vtkSetMacro(Value,double);
  vtkGetMacro(Value,double);
protected:
  vtkTest();
  ~vtkTest();
  
  int RequestData(vtkInformation *, vtkInformationVector **, vtkInformationVector *);

private:
  vtkTest(const vtkTest&);  // Not implemented.
  void operator=(const vtkTest&);  // Not implemented.
  
  double Value;
};

#endif

</source>

==vtkTestReader.h==
<source lang="cpp">
#ifndef __vtkTestReader_h
#define __vtkTestReader_h

#include "vtkAlgorithm.h"

class vtkTestReader : public vtkAlgorithm 
{
public:
  vtkTypeRevisionMacro(vtkTestReader,vtkAlgorithm);
  void PrintSelf(ostream& os, vtkIndent indent);

  static vtkTestReader *New();
	
protected:
  vtkTestReader();
  ~vtkTestReader();
  
  int FillOutputPortInformation( int port, vtkInformation* info );
  int RequestData(vtkInformation *, vtkInformationVector **, vtkInformationVector *);

private:
  vtkTestReader(const vtkTestReader&);  // Not implemented.
  void operator=(const vtkTestReader&);  // Not implemented.

};

#endif

</source>

==vtkTest.cxx==
<source lang="cpp">
#include "vtkTest.h"

#include "vtkObjectFactory.h"
#include "vtkStreamingDemandDrivenPipeline.h"
#include "vtkInformationVector.h"
#include "vtkInformation.h"

vtkCxxRevisionMacro(vtkTest, "$Revision: 1.70 $");
vtkStandardNewMacro(vtkTest);

vtkTest::vtkTest()
{
  
}

vtkTest::~vtkTest()
{

}

int vtkTest::RequestData(
  vtkInformation *vtkNotUsed(request),
  vtkInformationVector **vtkNotUsed(inputVector),
  vtkInformationVector *outputVector)
{
  
  // get the info object
  vtkInformation *outInfo = outputVector->GetInformationObject(0);
  
  // get the ouptut
//  vtkPolyData *output = vtkPolyData::SafeDownCast(
//		  outInfo->Get(vtkDataObject::DATA_OBJECT()));
  
  //output->ShallowCopy(polydata);
  
  return 1;
}


//----------------------------------------------------------------------------
void vtkTest::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os,indent);

  os << indent << "Value: " << this->Value << "\n";	
}


</source>

==vtkTestReader.cxx==
<source lang="cpp">
#include "vtkTestReader.h"
#include "vtkTest.h"

#include "vtkObjectFactory.h"
#include "vtkStreamingDemandDrivenPipeline.h"
#include "vtkInformationVector.h"
#include "vtkInformation.h"
#include "vtkDataObject.h"
#include "vtkSmartPointer.h"

vtkCxxRevisionMacro(vtkTestReader, "$Revision: 1.70 $");
vtkStandardNewMacro(vtkTestReader);

vtkTestReader::vtkTestReader()
{
  this->FileName = NULL;
  this->SetNumberOfInputPorts(0);
  this->SetNumberOfOutputPorts(1);
}

vtkTestReader::~vtkTestReader()
{

}

int vtkTestReader::FillOutputPortInformation( int port, vtkInformation* info )
{
  if ( port == 0 )
  {
    //info->Set(vtkDataObject::DATA_TYPE_NAME(), "vtkTest" );
    info->Set(vtkObject::DATA_TYPE_NAME(), "vtkTest" );
    return 1;
  }

  return 0;
}

int vtkTestReader::RequestData(
  vtkInformation *vtkNotUsed(request),
  vtkInformationVector **vtkNotUsed(inputVector),
  vtkInformationVector *outputVector)
{
  
  // get the info object
  vtkInformation *outInfo = outputVector->GetInformationObject(0);
  
  // get the ouptut
   vtkTest *output = vtkTest::SafeDownCast(
                    outInfo->Get(vtkObject::DATA_OBJECT()));
	  //outInfo->Get(vtkDataObject::DATA_OBJECT()));
  
  vtkSmartPointer<vtkTest> test = vtkSmartPointer<vtkTest>::New();
  test->SetValue(5.1) ;
  
  output = test;
    
  return 1;
}


//----------------------------------------------------------------------------
void vtkTestReader::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os,indent);

  os << indent << "File Name: " 
      << (this->FileName ? this->FileName : "(none)") << "\n";	
}


</source>

==CMakeLists.txt==
<source lang="text">
cmake_minimum_required(VERSION 2.6)
PROJECT(vtkAlgorithmDemo)

FIND_PACKAGE(VTK REQUIRED)
INCLUDE(${VTK_USE_FILE})

ADD_EXECUTABLE(vtkAlgorithmDemo Example.cxx vtkTest.cxx vtkTestReader.cxx)
TARGET_LINK_LIBRARIES(vtkAlgorithmDemo vtkHybrid)


</source>