[Interest] Subclassing QTreeWidgetItem together with QObject

[André Somers]

Op 27/11/2015 om 15:01 schreef Andrej Kacian:
> On Fri, 27 Nov 2015 10:39:19 +0100
> André Somers <andre at familiesomers.nl> wrote:
>
>>> Or is there a better way to do what I described?
>>>   
>> Perhaps, depending on what you really want to achieve. Instantiating
>> QObjects everywhere is quite expensive. If you have a lot of items in
>> your tree, it may cause performance issues.
> Hm, performance is a good point, I did not think of that.
>
> Basically, until now I have subclassed QTreeWidgetItem just to overload
> its operator<(), because I need custom sorting in this particular tree
> widget.
>
> In the Qt::UserRole column, I hold a pointer to an object, and I need
> to update displayed columns when this object changes.
>
> At the moment, I am handling this via a custom slot on QTreeWidget
> (the objects emit a signal when they change), which looks up the correct
> item to update and updates its columns. It works fine, but I thought
> that it would be more elegant to have each item "listen" for changes in
> its object directly. Hence the idea to add the QObject inheritance to my
> QTreeWidgetItem subclass.
>
Would it not be worth consideration to move to a custom model instead 
then? The custom model could just access the real items directly as well 
as listen for relevant changes to notify the views via the proper API 
for that.

How best to implement that depends on the actual structure of the data 
you already have in your application of course, and on the kinds of 
operations you need to support (it makes a difference if the tree 
structure is static or may change, for instance).

However, note that getting tree models right is not trivial. Still, it 
is usually the best solution. I am not a big fan of the "standard" 
models, let alone the *Widget variants.

André