Reactive Marbles Property Changed

A framework for providing an observable with the latest value of a property expression.

Will use Expression trees on platforms that support it (no iOS based platforms). On iOS it will just use reflection. This provides a roughly 2x performance boost for those platforms that can use expression trees.

this.WhenPropertyChanges(x => x.Property1.Property2.Property3);

The above will generate a IObservable<T> where T is the type of Property3. It will signal each time a value has changed. It is aware of all property changes in the property chain.

Binding

There are several methods of binding.

First is two way binding. Two way binding will update either the host or the target whenever the target property has changed.

host.Bind(target, host => host.B.C, target => target.D.E);

One way binding will only update the target with changes the host's specified target property.

host.OneWayBind(target, host => host.B.C);

There are also overloads with lambdas that allow you to convert from the host to the target. These will allow you to convert at binding time to the specified formats.

host.OneWayBind(target, host => host.B.C, hostProp => ConvertToTargetPropType(hostProp));
host.Bind(target, host => host.B.C, target => target.D.E, hostProp => ConvertToTargetPropType(hostProp), targetProp => ConvertToHostPropType(targetProp));

Limitations compared to ReactiveUI

At the moment it only supports INotifyPropertyChanged properties. More property types to come such as WPF DependencyProperty.

Milestones

• Implement initial binding and property changes.
• Introduce AOP for allow removal of expressions.

Benchmark Comparisons

|                 Method |    N |         Mean |      Error |       StdDev |     Gen 0 | Gen 1 | Gen 2 |  Allocated |
|----------------------- |----- |-------------:|-----------:|-------------:|----------:|------:|------:|-----------:|
| ReactiveMarblesChanges |    1 |     80.61 us |   1.542 us |     1.515 us |    8.9111 |     - |     - |   13.82 KB |
|      ReactiveUIChanges |    1 |    246.01 us |  19.087 us |    55.069 us |         - |     - |     - |   20.38 KB |
| ReactiveMarblesChanges |   10 |    258.15 us |   2.114 us |     1.977 us |   27.3438 |     - |     - |   42.32 KB |
|      ReactiveUIChanges |   10 |    581.21 us |  10.042 us |     8.902 us |   36.1328 |     - |     - |   55.75 KB |
| ReactiveMarblesChanges |  100 |  1,968.07 us |  28.810 us |    25.539 us |  212.8906 |     - |     - |  328.04 KB |
|      ReactiveUIChanges |  100 |  4,754.17 us |  49.251 us |    43.659 us |  281.2500 |     - |     - |  437.24 KB |
| ReactiveMarblesChanges | 1000 | 19,262.79 us | 275.029 us |   257.262 us | 2062.5000 |     - |     - | 3180.23 KB |
|      ReactiveUIChanges | 1000 | 45,432.12 us | 902.420 us | 1,843.404 us | 2000.0000 |     - |     - | 4232.83 KB |

The above benchmarks for compares ReactiveUI WhenAnyValue to WhenPropertyChanges. On every platform apart from iOS/TVOS/WatchOS the new property changes out performs ReactiveUI versions.