Caching QAbstractProxyModel dilemma

[Alessandro]

Hi,

I have a model derived from QAbstractListModel and a list view derived from QListView. The models data(..) method needs to perform some calculation each time it returns a value. Since the view queries the data very often, I thought about some sort of cache in order to have that calculation only once per model index.

Instead of implementing the caching directly in the model, I thought to plug a proxy model (derived from QAbstractProxyModel) between my model and my view. The proxy should then somehow cache the passed data in its data(..) method.

Now, here is my problem: Since the data(..) method is const, it has no write access to the class members, so it cannot write anything into a cache.

Has somone here already implemented a cache proxy and solved that problem? Or is there a better way to cache something between model and view?

Thank you,
Alessandro

[jacek]

Now, here is my problem: Since the data(..) method is const, it has no write access to the class members, so it cannot write anything into a cache.

You could use the "mutable" keyword.

[Alessandro]

Thank you, Jacek.
Now, I finally learned what that mutable keyword is good for.

-Alessandro