Incorporate Observable Values Into Nestings

[nipafx]

Description

If the inner observable of a nesting hierarchy is no Property but only an ObservableValue, currently only listeners can be attached. The possibility to also create a NestedObservableValue could be implemented.

It is currently not clear, though, exactly how useful they would be. JavaFX only provides the following implementations of ObservableValue:

• ...Binding
• ...Expression
• ...Property

Properties are already covered and bindings will soon be, too (see #2). Up to now no thoughts were put into expressions.

This implies that nested observable values only seems to be useful when code using LibFX typically contains user implementations of ObservableValue. If that is the case, this ticket should gain some +1s.

Implementation

Nested observable values would be implemented analogue to nested properties:

• the builders in the package nesting would have to be extended to accommodate the different kinds of Observable...Value interfaces
• a package nesting.observablevalue would contain the NestedObservable...Value classes as well as their builders.

Tests and docs go without saying...