[OpenWalnut-Dev] WItemSelection & friends improvement

[Christof Pieloth]

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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>

-- 
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