ReactiveCompositeCollections

A .Net library for composing reactive collections providing monadic types to support LINQ.

Motivation

We often have heirachical components that maintain collections of things. Imagine a collection of 3D objects that all produce lines. The 3D objects could be arranged in nested components. What we want is to be able to collect all the lines in the heirarchy as a flat reactive object

CompositeSourceList<ICompositeSourceList<Line>> nestedLines = new CompositeSourceList<ICompositeSourceList<Line>>();

Widget wa = new Widget();
Widget wb = new Widget();

nestedLines.Add(wa.Lines);
nestedLines.Add(wa.Lines);

ICompositeList<Line> allLines = 
               from lines in nestedLines
               from line in lines
               select line;
               
// Subscribe the the stream of flattened lines               
allLines.Items.Subscribe((ImmutableList<Line> lines)=>RenderLines(lines));

// or create an INPC object with a property Items
using(var s = allLines.Subscribe()){
   RenderLines(s.Items);
}

Using ICompositeCollection with WPF.

To use the ICompositeCollectin you need to convert it to a ReadOnlyObservableCollection via the following method.

    [Fact]
    public void ShouldWorkWithRangeOperators()
    {
        var source0 = new CompositeSourceList<int>();
        var source1 = new CompositeSourceList<int>();

        var target = source0.Concat(source1);

        using (var observableCollection = target.CreateObservableCollection(EqualityComparer<int>.Default))
        {

            observableCollection.Count.Should().Be(0);

            source0.AddRange(new [] {0,1,2});

            observableCollection.Should().Equal(0, 1,2);

            source0.Add(1);
            source1.Add(6);

            observableCollection.Should().Equal(0, 1, 2, 1, 6);

            source1.AddRange(new [] {3,4,5});

            observableCollection.Should().Equal(0, 1, 2, 1, 6, 3, 4, 5);

            source0.InsertRangeAt(1, new [] {6,7});

            observableCollection.Should().Equal(0, 6, 7, 1, 2, 1, 6, 3, 4, 5);

            source1.InsertRangeAt(1, new [] {6,7});
            observableCollection.Should().Equal(0, 6, 7, 1, 2, 1, 6, 6, 7, 3, 4, 5);

            source0.Source.Should().Equal(0, 6, 7, 1, 2,1);
            source0.Replace(1,99);
            observableCollection.Should().Equal(0, 6, 7, 99, 2, 1, 6, 6, 7, 3, 4, 5);


        }
    }

Note that the ReadOnlyObservableCollection is IDisposable so you should get rid of it when you don't need it anymore.