incremental loading without total count information

[user4592357]

i'm wondering whether it is possible to implement incremental data loading in views without knowing the total number of results in advance?

[JonB]

QAbstractbModel has fundamental fetchMore(), https://doc.qt.io/qt-5/qabstractitemmodel.html#fetchMore, and for example the QSql models implement this 256 rows at a time. So incremental loading is going on regardless of row count.

You can leverage that in your views. "Paging" can fetch the next block of rows.

[user4592357]

@JonB
for fetchMore() to work, i need to implement canFetchMore() which means i need to know whether there's more data available or not?
how will data() be called for model index, if rowCount() is not known?

[JonB]

@user4592357
You only have to know if there is more data to fetch, not how many total there is. But in any case I assume you can have canFetchMore() return true while you don't know, and only in fetchMore() do you do the next fetch and discover whether there was any more.

If a QModelIndex is for row not yet fetched, you can have data() fetch more to resolve the reference if necessary. You wouldn't have to know the final rowCount() up front.