[vtk-developers] Casting vtkIntArray vs vtkIdTypeArray

[David Gobbi]

Also, don't forget that you can convert an array to a different type
via a DeepCopy.

vtkIdTypeArray *newArray = vtkIdTypeArray::New();
newArray->DeepCopy(array_of_unknown_type);

I get the feeling that this is what you wanted in the first place.

   David


On Fri, Sep 17, 2010 at 3:42 PM, pat marion <pat.marion at kitware.com> wrote:
> David,
>
> Instead of saving a file and opening it in paraview, you could try:
>
>       filter->GetOutput()->Print(cout);
>
> This will display all the point & cell arrays on the output and their names
> and data types.  Make sure you have updated the filter first.  Also, if you
> notice that SafeDownCast has failed, you can do a debug print to get the
> correct class type:
>
>        cout << filter->GetOutput()->GetArray("RegionId")->GetClassName() <<
> endl;
>
> this would print: vtkIdTypeArray
>
> GetClassName is great for debugging, but I wouldn't recommend it for
> comparisons.  For example, instead of:
>
>       if (array->GetClassName() == std::string("vtkIdTypeArray")) cout <<
> "It's an id type array";
>
> it is preferable to use:
>
>       if (vtkIdTypeArray::SafeDownCast(array)) cout << "It's an id type
> array";
>
> The compiler can error check a SafeDownCast statement, but can't catch a
> typo in a string comparison.
>
> Pat
>
>
> On Fri, Sep 17, 2010 at 4:03 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>
>> Hi David,
>>
>> I think you misunderstand what "SafeDownCast" does.
>> After every SafeDownCast(), you must check the result
>> to make sure that it isn't NULL.  That is what dynamic
>> casting is all about: it is an _attempt_ to do a cast when
>> you aren't sure if the object is of the correct type.
>>
>> You can write code that is robust to a large number of
>> array types by adding a "switch" statement.  If you combine
>> the switch with a templated function, then you will
>> end up with the same mechanism that VTK's image filters
>> use to deal with arrays of different types.
>>
>>  David
>>
>>
>> On Fri, Sep 17, 2010 at 1:53 PM, David Doria <daviddoria at gmail.com> wrote:
>> > On Fri, Sep 17, 2010 at 3:50 PM, David Cole <david.cole at kitware.com>
>> > wrote:
>> >>
>> >> That's not a C++ cast, that's a transformation operation....
>> >> All the array classes are siblings of each other, aren't they?
>> >>
>> >
>> > Maybe my terminology is off, but whatever it is called I feel that it
>> > should
>> > work and it currently doesn't :)
>> > Yes, they are all siblings. Are you recommending first SafeDownCasting
>> > to a
>> > vtkDataArray, checking the type, and then performing the appropriate
>> > SafeDownCast? That seems like a lot of trouble, no?
>> > David
>> > _______________________________________________
>> > Powered by www.kitware.com
>> >
>> > Visit other Kitware open-source projects at
>> > http://www.kitware.com/opensource/opensource.html
>> >
>> > Follow this link to subscribe/unsubscribe:
>> > http://www.vtk.org/mailman/listinfo/vtk-developers
>> >
>> >
>> >
>> _______________________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Follow this link to subscribe/unsubscribe:
>> http://www.vtk.org/mailman/listinfo/vtk-developers
>>
>
>