[vtk-developers] Smart pointer declaration macro?

[David Gobbi]

On Fri, Jan 8, 2010 at 2:08 PM, Marcus D. Hanwell
<marcus.hanwell at kitware.com> wrote:
> On Friday 08 January 2010 15:52:40 David Cole wrote:
>> On Fri, Jan 8, 2010 at 3:41 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>> > On Fri, Jan 8, 2010 at 1:38 PM, David Doria
>> > <daviddoria+vtk at gmail.com<daviddoria%2Bvtk at gmail.com>>
>> > >> On Fri, Jan 8, 2010 at 3:26 PM, David Gobbi <david.gobbi at gmail.com>
>> >
>> > wrote:
>> > >>> On Fri, Jan 8, 2010 at 1:15 PM, David Doria
>> > >>> <daviddoria+vtk at gmail.com<daviddoria%2Bvtk at gmail.com>>
>> >
>> > wrote:
>> > >>>> I've seen the use of something like this:
>> > >>>>
>> > >>>> #define SPNEW(instance, type) \
>> > >>>> vtkSmartPointer<type> instance = vtkSmartPointer<type>::New();
>> > >>>>
>> > >>>> in many of the tests and elsewhere. It seems like a reasonable
>> > >>>> savings of a whole bunch of characters that appears many many times
>> > >>>> in most functions. Could we standardize something like this so it
>> > >>>> can be used universally without having to see this little #define in
>> > >>>> every file it is used in?
>> > >>>
>> > >>> Doesn't VTK have enough macros already? ;)
>> > >>>
>> > >>> There are other ways to reduce the repetition, without using macros:
>> > >>>
>> > >>> 1) Add a new constructor argument for smart pointers:
>> > >>>
>> > >>> vtkSmartPointer<type> instance(1); // create an smart pointer and
>> > >>> allocate an object at the same time
>> > >>> vtkSmartPointer<type> instance(0); // create a smart pointer with
>> > >>> "null" as the initial pointer
>> > >>>
>> > >>> 2) Add a non-static "New" method for smart pointers:
>> > >>>
>> > >>> vtkSmartPointer<type> instance;
>> > >>> instance.InstantiateNew();
>> > >>>
>> > > Sure, I hate macros :)
>> > >
>> > > So how do we turn these good suggestions into a final conclusion and
>> > > course of action?
>> > >
>> > > My choice/thought after seeing these initial comments is that it would
>> > > be nice if ITK and VTK shared a similar style (the ::SmartPointer).
>> > >
>> > > Bill - there is plenty of mystery even with the additional typing :)
>> >
>> > Actually, I'll give a "+1" to Bill's comment because I do like code to
>> > be as explicit as possible.
>>
>> Me too. +1.
>>
>> Which sort of means eliminating all the existing SPNEW macros from test
>> files, doesn't it...? :-)
>>
> I would like to add my -1, I think needing to split lines in order to declare
> a new local variable is a little much. I came from a C++ background where any
> object could be declared on the stack though. For things like the examples it
> seems to hurt readability to me.
>
> Pointer:
> vtkFloatArray *myTable = vtkFloatArray::New();
> myTable->Delete();
> myTable = NULL;
>
> Smart pointer:
> vtkSmartPointer<vtkFloatArray> myTable =
>     vtkSmartPointer<vtkFloatArray>::New();
>
> Smart pointer with macro:
> VTK_CREATE(vtkFloatArray, myTable);
>
> Stack:
> vtkFloatArray myTable;
>
> I would prefer to be able to use something like the first or the last. In
> classes etc it is often a different story. It seems like there should be some
> macro or template function to generate variables with less repetition.
>
> Just my $0.02...
>
> Marcus

But there already is a way to allocate VTK objects on the stack...
it's called a smart pointer. :)

And it's a lot less complex than a most of the STL.

  David