[Insight-developers] Modes versus Objects

[Luis Ibanez]

Bill,

Yeap,

We need more of these guiding principles,

and
we need to capture them somewhere in the Wiki,
so they are available for quick reference when
we are making code changes.

Something along the lines of what we have in:

http://www.itk.org/Wiki/ITK_Coding_Style_Guide
http://www.itk.org/Wiki/ITK_Code_Review_Check_List

Otherwise,
it is easy to settle for the quickest solution
that let the Dashboard go back to green.

Here is a first cut at that new Wiki
page on Design Principles:

http://www.itk.org/Wiki/ITK_Design_Principles


and it is now linked from:
http://www.itk.org/Wiki/ITK_Policies_and_Procedures


     Luis


------------------
On Thu, Jun 2, 2011 at 11:32 AM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> Folks,
>
> This discussion is motivated by recent activity...
>
> Back in the early days of OO programming, I recall having discussions
> about the use of modes versus objects. When I taught OO courses I
> always discouraged modes if they changed the "identity" of the object.
>
> Should a mode be used to change the behaviour of an object or should a
> new object be created?
>
> A case where a mode is better than an object:
> Controlling the visibility of an actor in VTK:
>  1) Mode: vtkActor VisibilityOn/Off
> or
>  2) Object: two classes vtkActor and vtkVisibleActor
>
>  1) is the appropriate solution since, at run time, an application
> may want to change the visibility of an actor.
>
> A case where an object may be better than a mode:
>  1) Mode: itkShiftScaleImageFilter
> SetOperationOrderToShiftScale()/SetOperationOrderToScaleShift()
> or
>  2) Object: two classes itkShiftScaleImageFilter and itkScaleShiftImageFilter
>
>  A VTK approach versus an ITK approach
>  1) mode: vtkImageMathematics 21 different modes (ADD,SUBTRACT,MULTIPLY,...)
>  2) object: itkAddImageFilter, itkSubtractImageFilter,
> itkMultipleImageFilter...
>
> It is not always obvious as to the best choice. But, I think the
> question should be asked anytimne we introduce a new "mode".
>
> Bill
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