Collection update

[Georgy Levchenko]

Hello. A question about the work of collections.
I have previously used RX UI.

Every time the NavigationSearchText changes, I have to get a new collection, but in my case I get the old collection plus the new one (adding element). I used a crutch like (.Do (_ => NavigationSearchItems? .ClearOnScheduler ())).

            NavigationSearchItems = NavigationSearchText
                .Skip(1)
                .Throttle(TimeSpan.FromMilliseconds(500))
                .Select(term => term?.Trim())
                .DistinctUntilChanged()
                .Do(_ => NavigationSearchItems?.ClearOnScheduler())
                .SelectMany(x => nameMenuItems.Where(y => y.Contains(x, StringComparison.OrdinalIgnoreCase)))
                .ToReactiveCollection();

Please, tell me how to do it better.

[soi013]

Probably, change this.

.ToReactiveCollection();

👇

.ToReadOnlyReactivePropertySlim();

[Georgy Levchenko]

This change does not work. The logic of work is changing.
The last element is selected and broken down by letters.

For example, instead of the "Home" element, we get "H", "O", "M", "E".

[soi013]

OK, how about this.
NavigationSearchItems type is changed.

NavigationSearchItems = NavigationSearchText
                .Skip(1)
                .Throttle(TimeSpan.FromMilliseconds(500))
                .Select(term => term?.Trim())
                .DistinctUntilChanged()
                .Select(x => nameMenuItems
                   .Where(y => y.Contains(x, StringComparison.OrdinalIgnoreCase))
                   .ToArray())
                .ToReadOnlyReactivePropertySlim();

[Georgy Levchenko]

Yes. It works. Thanks for the help.

But still. Better why does the collection have this behavior? Is it better to use properties or a collection in this case?

[Kazuki Ota]

@FoxTes
I guess it works replacing to Clear() from ClearOnScheduler() and adding ObserveOnUIScheduler() after DistinctUntilChanged().

NavigationSearchItems = NavigationSearchText
                .Skip(1)
                .Throttle(TimeSpan.FromMilliseconds(500))
                .Select(term => term?.Trim())
                .DistinctUntilChanged()
                .ObserveOnUIDispatcher()
                .Do(_ => NavigationSearchItems?.Clear())
                .SelectMany(x => nameMenuItems.Where(y => y.Contains(x, StringComparison.OrdinalIgnoreCase)))
                .ToReactiveCollection();

However, I recommend @soi013 's approach. Because you said "Every time the NavigationSearchText changes, I have to get a new collection,", I guess it means ReadOnlyReactiveProperty<string[]>.

[Georgy Levchenko]

Thanks for the explanation. I will take this into account in the future.