[Interest] Best practice for properties, QAbstractListModel with a QList<QObject*> and a Quick2 view

Jan Kundr√°t jkt at flaska.net
Wed Dec 18 17:19:04 CET 2013


(No need to Cc me, I read the list.)

> The delegate is alive for a short period after this, it seems. I guess
> maybe just another event loop cycle? I didn't investigate it further yet
> though.

Interesting. If that is indeed the case, perhaps you could use distinct 
delegates based on the value of myObject, but I suspect one cannot do this 
after the delegate was already instantiated.

Anyway, what is rather interesting is to find out how exactly the delegate 
learns that the actual value of "myObject" has changed. Perhaps it does not 
actually learns this via the usual MVC channels and this only happens by 
chance due to the fact that you are using property bindings on top of the 
returned object. I.e. the delegate previously set up a binding to a 
property of myObject, the referenced QObject ceases to exist, the binding 
gets invalidated (?) and the delegate reacts to that by re-evaluating the 
expression, only to find out that the myObject is now null.

What happens if you change the deleteLater() to an immediate delete (and 
move it between the beginRemoveRows and endRemoveRows)? Are you deleting 
your items in the middle of the list, or always at the end?

Cheers,
Jan

-- 
Trojit√°, a fast Qt IMAP e-mail client -- http://trojita.flaska.net/



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