[vtkusers] Reference counting in 6.3

[Dan Lipsa]

Hi Weiguang,
Take a look at
http://www.vtk.org/Wiki/VTK/Tutorials/SmartPointers
This might clarify some of your questions. You have to remember that the
reference count is stored in the objects themselves unlike the c++
shared_ptr where the reference count is stored in the shared pointer object.

For the first question: do you assign the object to a vtk smart pointer?
That would explain why the reference count is 2.
For the rest of the questions: when you set up the pipeline there are other
objects involved besides the filter themselves, so it is harder to
understand of the reference count.

Also you can set VTK_DEBUG_LEAKS when you build VTK if you are concerned
about leaks.

Dan


On Thu, Oct 15, 2015 at 4:13 PM, Weiguang guan <guanw at rhpcs.mcmaster.ca>
wrote:

> Hello,
>
> I find, in debug mode, that the ReferenceCount of a
> vtkImageEllipsoidSource object becomes 2 right after being initiated
> (vtkImageEllipsoidSourc::New()). It should be 1 not 2, right? How could
> this happen?
>
> My second question is --- when you make a connection
> A->SetInputConnection(B->GetOutputPort()); Whose reference count will be
> increased by 1, A or B? I think B's reference count should be increased
> because it is used by A. But what I find is just the opposite.
>
> My third question is about setting up more than 1 connection for a filter.
> Taking vtkImageMathematics as an example, I do
> vtkImageMathematics* A = vtkImageMathematics::New();
> A->SetInputConnection(0, B1->GetOutputPort();
> A->SetInputConnection(0, B2->GetOutputPort();
>
> I find that the reference count of A gets increased by the first
> SetInputConnection() call only.
>
> Can someone explain how reference counting works in VTK? Thanks.
>
> Best,
> Weiguang
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