Join not fire after filter when sencode source item add after the first source item fire.

[Snailya]

In my case, I have two source A and B. The item in B for most of time comes with a delay compared with A. Paried A and B are used to build up a viewmodel.
A filter here is to used to determine which A should be included in the transformation.Without this filter, everything works well. However, if I add this filter, when the A emit change, because of currently there is no match item in B, nothing is created. Then, the item in B borned, but now filter A will not emit anything, so that there is no VM too.

var filter = _visibleA.Connect()
            .AutoRefresh(x => x.IsExpanded)
            .Filter(x => x.IsExpanded)
            .Transform(x => x.Id)
            .StartWithEmpty()
            .ToCollection()
            .Select<IReadOnlyCollection<int>, Func<A, bool>>(x =>
                f => x.Contains(f.ParentId) || f.ParentId.IsNull());

        var observeB= B.Connect();
        A.Connect()
            .Filter(filter)
            .InnerJoin(observeB,
                x => x.Id,
                (A, B) => new VM(A,B))
            .ChangeKey(x=>x.Id)
            .Filter(x=>!string.IsNullOrEmpty(x.Name))
            .PopulateInto(_visibleA);
`

[JakenVeina]

If I'm reading you correctly, you're saying that...

• .Filter(filter) excludes items from A when they do not have a matching item in B
• When a matching item appears in B, the corresponding item from A has already been filtered out

If so, I would say that you need to rewrite your filter logic so that items from A that don't have a matching item in B don't get excluded. The .InnerJoin() effectively performs this exclusion for you. If this is not feasible, you need to adjust the filtering query to ensure that it refreshes when items get added to B, so that items from A that were previously filtered out get added back. You're already using .AutoRefresh() before .Filter() within your first query, to ensure that filtering gets re-evaluated when things that affect filtering (.IsExpanded) change. It looks like you just need to do that on the second query as well. I.E. you need either an .AutoRefresh() or .AutoRefreshOnObservable() before .Filter() that will identify when each item from A needs to be re-evaluated, based on changes in B.

[Snailya]

Thank you for you answer. After carefully check the logic I find that there is a logic error in the VM create part where I want to pass in an observable to see if there is any items that are children of the current item.
I need to set HasChildren property like this.

new VM(A,B){
    HasChildren = pivotedByParentId.WatchValue(x.Id).Any()
}

But I did it like this,

new VM(A,B){
    HasChildren = pivotedByParentId.Lookup(location.Id).HasValue?pivotedByParentId.WatchValue(x.Id).Any():null
}

[JakenVeina]

Glad to hear you got it sorted out.