one-to-one binding

gistfile1.d

abstract class IProperty
{
	// called when value changes. 
	alias PropertyChangedSignal = Signal!(FlexibleObject, Variant);
	alias PropertyChangingSignal = Signal!(FlexibleObject, Variant*);

	Variant value() @property;
	Variant value(Variant) @property;

	ref PropertyChangedSignal valueChanged() @property;
	ref PropertyChangingSignal valueChanging() @property;
	
	alias value this;
}

static void pipeTo(IProperty source, IProperty dest, Variant delegate(Variant) converter)
{
	auto handler = (FlexibleObject obj, Variant value){
		dest.value = converter(value);
	};

	dest.value = converter(source.value);

	source.valueChanged.connect(handler);
}