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# KnownLengthArray

VTKEx/Cxx/Utilities/KnownLengthArray

### Description

This example creates a VTK style float array. This can be easily interchanged with vtkIntArray, vtkDoubleArray, etc.

The terminology is as follows:

- `SetNumberOfComponents()`: sets the number of elements that a tuple in the array will have. See VectorArrayKnownLength for an example with tuples with more than one element.

- `SetNumberOfValues()`: sets the number of tuples the array will have. See UnknownLengthArray for an example where the number of values is not known in advance.

Other languages

See (Java)

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

KnownLengthArray.cxx

    #include <vtkSmartPointer.h>
    #include <vtkFloatArray.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkFloatArray> distances =
        vtkSmartPointer<vtkFloatArray>::New();
      distances->SetName("Distances");
      distances->SetNumberOfComponents(1);
      distances->SetNumberOfValues(5);

      //set values
      for(vtkIdType i = 0; i < distances->GetNumberOfTuples(); i++)
      {
        float f = (float)i + 0.1;
        distances->SetValue(i, f);
      }

      //get values
      for(vtkIdType i = 0; i < distances->GetNumberOfTuples(); i++)
      {
        float f = distances->GetValue(i);
        std::cout << f << std::endl;
      }

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(KnownLengthArray)

    find_package(VTK COMPONENTS
      vtkCommonCore QUIET)
    if (NOT VTK_FOUND)
      message("Skipping KnownLengthArray: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(KnownLengthArray MACOSX_BUNDLE KnownLengthArray.cxx )
      target_link_libraries(KnownLengthArray PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(KnownLengthArray MACOSX_BUNDLE KnownLengthArray.cxx )
      target_link_libraries(KnownLengthArray PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS KnownLengthArray
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build KnownLengthArray

Click here to download KnownLengthArray and its CMakeLists.txt file. Once the tarball KnownLengthArray.tar has been downloaded and extracted,

    cd KnownLengthArray/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

    cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

    make

and run it:

    ./KnownLengthArray

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.