[vtk-developers] Multiple inheritance

[Paul Douglas Hahn]

revise "base classes" -> "interface classes"

On 07/02/2018 04:04 PM, Paul Douglas Hahn wrote:
> Just one caveat (you probably already know and agree with this). In my 
> experience using C++ multiple inheritance, I think you should try to 
> avoid situations where you have common base classes in the inheritance 
> pathways. Virtual base classes are the usual recommendation to resolve 
> certain problems that arise in such cases, but IMHO having experience 
> with that, I generally recommend against it.
>
> So I recommend your base classes should be of the "_mix-in_" interface 
> category, not relaying on any common base class. The approach works 
> fine for me in almost every situation.
>
> - Paul
>
> On 07/02/2018 12:44 AM, Todd Martin via vtk-developers wrote:
>> Single inheritance languages like Java and C# utilize /interfaces/ 
>> extensively. Python 2.7+ handles the same concept with abstract base 
>> classes, ABCs.
>>
>> Is there any interest in supporting/interfaces/ in VTK via multiple 
>> inheritance from abstract classes (which do not inherit from 
>> vtkObject) while retaining the single inheritance model?
>>
>> In my view there are good reasons to do so. For example vtkCell has 
>> methods like GetNumberOfEdges(), GetEdge(), GetNumberOfFaces(), 
>> GetFace() etc. which really only apply to multi-dimensional cells 
>> (both linear and non-linear); i.e. not points and lines. These 
>> methods are forced on the base class design by a single inheritance 
>> structure and the linear/non-linear cell sub-types. In my view it 
>> would be better if they were distributed across the sub-classes via 
>> the concept of interfaces. So I'm suggesting a limited use of 
>> multiple inheritance here, not a free-for-all approach. What do 
>> others think about this?
>>
>> For an example please see this merge request Add missing size hints 
>> and bug fix point arrays for non-linear cells (!4372) · Merge 
>> Requests · VTK / VTK 
>> <https://gitlab.kitware.com/vtk/vtk/merge_requests/4372>
>>
>>
>> 	
>>
>>
>> 	
>>
>>
>>     Add missing size hints and bug fix point arrays for non-linear
>>     cells (!4...
>>
>> I've added size hints for concrete public methods 
>> GetParametricCoords(), GetEdgePoints() and GetFacePoints() in ...
>>
>> <https://gitlab.kitware.com/vtk/vtk/merge_requests/4372>
>>
>>
>>
>> Todd Martin, PhD.
>> /Freelance Engineer/Software Architect./
>>
>>
>>
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>
>
> -- 
> Paul D. Hahn
> CompIntense HPC, LLC


-- 
Paul D. Hahn
CompIntense HPC, LLC

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