ObservableCollectionView does not remove items which do not match the filter

[DamianReeves]

I've been using the ObservableCollectionView's ability to filter items in the collection but I saw issues where items which were modified in order to no longer meet the filter criteria not being removed. It seems this issue is due to how the ObserveCollectionItemChanged() call is made:

source.ObserveCollectionItemChanged<T>()
    .Where(updateFilter)
    .Select(x => x.Sender)
    .Where(filter)
    .ObserveOn(RxApp.DeferredScheduler)
    .Subscribe(updateItem);

The above will never call updateItem to remove items which don't meet the filter criteria.
This can be fixed by adding the following code as well:

source.ObserveCollectionItemChanged<T>()
    .Where(updateFilter)
    .Select(x => x.Sender)
    .Where(x=> !filter(x))
    .ObserveOn(RxApp.DeferredScheduler)
    .Subscribe(removeItem);

[anaisbetts]

How about instead:

source.ObserveCollectionItemChanged<T>()
    .Where(updateFilter)
    .Select(x => new { Item = x.Sender, Match = filter(x.Sender) })
    .ObserveOn(RxApp.DeferredScheduler)
    .Subscribe(x => {
        if (x.Match) {
            updateItem(x);
        } else {
            removeItem(x);
        }
    });

[DamianReeves]

I tried this in my unit tests and it works also (much nicer by the way).

source.ObserveCollectionItemChanged<T>()
    .Where(updateFilter)
    .Select(x => new { Item = x.Sender, Match = filter(x.Sender) })
    .ObserveOn(RxApp.DeferredScheduler)
    .Subscribe(x => {
        if (x.Match) {
            updateItem(x.Item);
        } else {
            removeItem(x.Item);
        }
    });

Note: the x.Item change

[anaisbetts]

hwhoops. Looks good, send me a PR!

[DamianReeves]

This issues seems to have been reintroduced in the latest source code version. The code fix is gone.

[anaisbetts]

ObservableCollectionView is deprecated, you want to use CreateDerivedCollection.

On Fri, Mar 23, 2012 at 7:38 PM, DamianReeves
reply@reply.github.com
wrote:

This issues seems to have been reintroduced in the latest source code version. The code fix is gone.

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Reply to this email directly or view it on GitHub:
https://github.com/xpaulbettsx/ReactiveUI/issues/44#issuecomment-4671177