[Qt-interest] tracking uniqueness

[Eirik Ulvik]

Den 24.04.2010 12:36, skrev Oliver Heins:
> Thiago Macieira <thiago at kde.org> writes:
> 
>> Em Sábado 24. Abril 2010, às 10.10.29, Oliver Heins escreveu:
>>> Andreas Pakulat <apaku at gmx.de> writes:
>>>> You seem to have a bit of misconception about this. There is no Editor
>>>> instance in your code. All you do is declare a class and a nested class,
>>>> both can be used without an instance of the other as far as your example
>>>> goes. In particular, this:
>>>>
>>>> class Editor
>>>> {
>>>>
>>>> public:
>>>>   class Token
>>>>   {
>>>>   };
>>>>
>>>> };
>>>>
>>>> Editor::Token t;
>>>>
>>>> is perfectly valid compiling code. And there's no instance of Editor
>>>> generated here, there's only a single instance of Token.
>>>
>>> So it's not possible in C++ to describe the idea: »Every instance of
>>> Token is held by an instance of Editor«?
>>
>> Of course it is.
>>
>> The counter is per editor, right? So it's a property of the editor.
> 
> Yes, but I have to hand over the id exlicitely.  I hoped to do something
> like this:
> 
> class Editor
> {
>         class Token
>         {
>         public:
>                 Token () : uniqId(++id_) { }
>         private:
>                 quint32 uniqId;
>         }
> 
>         quint32 id_;
> };
> 
> or to make id_ somehow static only to the instance of Editor.  
> 
> But both doesn't work.  Instead, I have to pass id_ explicitely in every
> constructor call:
> 
>          Token(quint32 &id_) : uniqId(++id_) { }
> 
> Best regards,
>  olli

I might be missing something here, but your problem seem related to
making the id unique ie. doing uniqId++ or something like that in a
consistent manner. What about just putting a QUuid
(http://doc.trolltech.com/4.6/quuid.html) member variable in your editor
class and instantiate it in the constructor? This would ensure that you
have a unique identifier for every editor in the simplest way IMO. The
only trouble I see is that QUuid's are not easy to work with if you need
the id to be human-readable.

Regards,
Eirik

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