vtkWeakPointerを使った例

  vtkSmartPointer<vtkActor> actor1 = vtkSmartPointer<vtkActor>::New();
  std::cout << "actor1 reference count: " << actor1->GetReferenceCount() << std::endl;

  vtkSmartPointer<vtkActor> actor2 = actor1;
  std::cout << "actor2 reference count: " << actor2->GetReferenceCount() << std::endl;

  actor1 = nullptr;// actor1を無効化
  std::cout << "Delete" << std::endl;

  // ここは通らない
  if(actor1)
    std::cout << "actor1 reference count: " << actor1->GetReferenceCount() << std::endl;

  if(actor2)
    std::cout << "actor2 reference count: " << actor2->GetReferenceCount() << std::endl;

  vtkWeakPointer<vtkActor> weak_actor; // WeakPointerを定義

  {

    vtkSmartPointer<vtkActor> actor1 = vtkSmartPointer<vtkActor>::New();
    std::cout << "actor1 reference count: " << actor1->GetReferenceCount() << std::endl;

    weak_actor = actor1;// actor1 を弱参照　参照カウンタは増えない
    std::cout << "weak_actor reference count: " << weak_actor->GetReferenceCount() << std::endl;


    vtkSmartPointer<vtkActor> actor2 = actor1;
    std::cout << "actor2 reference count: " << actor2->GetReferenceCount() << std::endl;


    actor1 = nullptr;
    std::cout << "Delete" << std::endl;

    // ここは通らない
    if (actor1)
      std::cout << "actor1 reference count: " << actor1->GetReferenceCount() << std::endl;

    if (actor2)
      std::cout << "actor2 reference count: " << actor2->GetReferenceCount() << std::endl;

  }

  if (weak_actor) {
    // ここは通らない
    std::cout << "actor1 reference count: " << weak_actor->GetReferenceCount() << std::endl;
  }
  else {
    // こちらを通る
    std::cout << "actor is deleted" << std::endl;
  }