[OpenWalnut-Dev] WItemSelection & friends improvement

Wed May 16 16:25:57 CEST 2012

Hi

I have commited your patch! I made some minor improvements and added some example code to the template module. Thank you very much for this work!

Bye
Sebastian

On Tue, 15 May 2012, Christof Pieloth wrote:

> ;) There would be a way (if I don't forget sth.) if you could define
> a base class of the class template type T, like in generics of Java:
> public class WAbstractItem* <T extends WAbstractItem*> ...
> In this case you could write a new templatized base class of WItem*
> (WAbstractItem*) with the templatized code of the current WItem* and
> the current WItem* would be an implementation with a fixed type
> (WItem* <WItem*>) or just a typedef. So we do not have to write code
> twice, but could implement new WItem* without breaking old modules.
> Anyway, with this limitation we can not change this with less effort.
> 
> see ya!
> 
> Am 15.05.2012 16:09, schrieb Sebastian Eichelbaum:
> >Btw. backward compatibility is not the reason. Its a technical issue which arises from the fact that every instantiated template is its own type without any polymorphic relations. You always need a base class for classes which share some basic functionality as the WItem classes do. The current WItem* classes are these base classes. Replacing them with templatized classes will not resolve the issue.
> >
> >Bye
> >Sebastian
> >
> >On Tue, 15 May 2012, Christof Pieloth wrote:
> >
> >>Hello,
> >>
> >>I have created a ticket with the *.diff:
> >>http://www.openwalnut.org/issues/174
> >>I decided to extend WItemSelectionItem as a container. This solution
> >>allows us to use any types even those without a default constructor.
> >>Sadly we now have a dynamic cast, but due to "downward
> >>compatibility" we have to take this.
> >>
> >>Bye
> >>Christof
> >>
> >>
> >>Am 14.05.2012 18:28, schrieb Christof Pieloth:
> >>>Tomorrow I will have a try and can hopefully send you a patch in a
> >>>few days.
> >>>
> >>>Am 14.05.2012 15:56, schrieb Sebastian Eichelbaum:
> >>>>Hi
> >>>>
> >>>>This is a nice idea. But technically, there are several things
> >>>>to do to achieve this:
> >>>>
> >>>>You will need to derive a new templatized class from
> >>>>WItemSelectionItem AND simultanously derive from the template
> >>>>type T. With this, you can use a queried WItemSelectorItem as
> >>>>your own type directly:
> >>>>
> >>>>template<   typename T>
> >>>>class WIteSelectionItemTyped: public WItemSelectionItem,
> >>>>                               public T
> >>>>
> >>>>Luckily, these items are handled using pointers. If they would
> >>>>be handles as copies throughout the WItemSelection, your
> >>>>explicitly derived typing would be lost. Now, you can provide a
> >>>>method to WItemSelectionItem:
> >>>>
> >>>>const T&   getValue() const;
> >>>>and
> >>>>T&   getValue()
> >>>>{
> >>>>   return *dynamic_cast<   T*>( this );
> >>>>}
> >>>>
> >>>>.. Then you would be able to use the item you query with
> >>>>WItemSelector::at
> >>>>
> >>>>mySelector->at( someIndex )->getValue<   MyType>().MyFunction();
> >>>>
> >>>>Even nicer would be to also provide WItemSelector::at and atAll
> >>>>with some template type to directly return a pointer to the
> >>>>WItemSelectionItemTyped instance ... awesome :-)
> >>>>
> >>>>If you implement something like this, we would be very happy to
> >>>>get a patch from you. You can create such a patch via hg export:
> >>>>
> >>>>$ hg pull -u
> >>>>$ edit files
> >>>>$ hg commit -m "[ADD] our nice feature"
> >>>>$ hg export
> >>>>
> >>>>
> >>>>The exported patch can be added by us to the upstream code and
> >>>>next time you do a hg pull, you can merge the stuff in.
> >>>>
> >>>>Thank you for your idea!
> >>>>If you have any problems when doing this, just drop a mail to the list!
> >>>>Sebastian
> >>>>
> >>>>
> >>>>On Mon, 14 May 2012, Christof Pieloth wrote:
> >>>>
> >>>>>Hello everybody,
> >>>>>
> >>>>>we are using a "WItemSelection"&   friends very often in our project
> >>>>>and missing a feature.
> >>>>>In most of our cases we fill a "WItemSelection" with an enum and
> >>>>>have to code our own mapper to get the corresponding enum value for
> >>>>>the selected "WItemSelectionItem", which we get from
> >>>>>"WItemSelector.at()". We may can extend "WItemSelectionItem" to a
> >>>>>template to hold a value of a generic type and a method like "T
> >>>>>WItemSelectionItem.getValue()". So you can use a switch-case
> >>>>>straight away.
> >>>>>What are you thinking of this idea?
> >>>>>
> >>>>>Best regards
> >>>>>Christof
> >>>>>
> >>>>>-- 
> >>>>>HTWK Leipzig, University of Applied Sciences
> >>>>>Faculty of Electrical Engineering and Information Technology
> >>>>>Laboratory for Biosignal Processing (LaBP)
> >>>>>
> >>>>>fon:  +49 (0) 341 3076 3133
> >>>>>fax:  +49 (0) 341 3076 853133
> >>>>>mail: pieloth 'at' labp.htwk-leipzig.de
> >>>>>
> >>>>>
> >>>>>_______________________________________________
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> >>>>>
> >>>>>Archive:
> >>>>>http://lists.informatik.uni-leipzig.de/pipermail/openwalnut-dev/
> >>>>>
> >>-- 
> >>HTWK Leipzig, University of Applied Sciences
> >>Faculty of Electrical Engineering and Information Technology
> >>Laboratory for Biosignal Processing (LaBP)
> >>
> >>fon:  +49 (0) 341 3076 3133
> >>fax:  +49 (0) 341 3076 853133
> >>mail: pieloth 'at' labp.htwk-leipzig.de
> >>
> >>
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> >>
> >>Archive: http://lists.informatik.uni-leipzig.de/pipermail/openwalnut-dev/
> >>
> 
> -- 
> HTWK Leipzig, University of Applied Sciences
> Faculty of Electrical Engineering and Information Technology
> Laboratory for Biosignal Processing (LaBP)
> 
> fon:  +49 (0) 341 3076 3133
> fax:  +49 (0) 341 3076 853133
> mail: pieloth 'at' labp.htwk-leipzig.de
> 
> 
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-- 
Dipl.-Inf. Sebastian Eichelbaum
Universität Leipzig
Institut für Informatik
Abteilung Bild- und Signalverarbeitung
PF 100920
D-04009 Leipzig