vtkNew and vtkSmartPointer

Development
13

That will still work. The check is for rvalue references only:

void ok()
{ 
  vtkNew<vtkPolyData> pd;
  // argument is an lvalue, implicit cast to T* allowed
  filter->SetInputData(pd);
}

void not_ok()
{
  // argument is rvalue, implicit cast to T* disallowed
  filter->SetInputData(vtkNew<PolyData>{}); // <-- compile error
}

void ok_again()
{
  // Argument is raw pointer, no implicit cast needed.
  // The explicit Get() call implies that the author has thought
  // about reference counting in the callee and is aware that this is a
  // boundary between automatic and manual reference counting.
  filter->SetInputData(vtkNew<vtkPolyData>{}.Get());
}

So basically, the implicit cast only works when the vtkNew object is not a temporary rvalue that would be destroyed at the end of the statement. If someone really wants to get the pointer out of the temporary, they can use Get(), but that’s a “here be dragons” operation and requiring the extra call prevents mistakes.

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