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From: Jeff Higgins <jeff@invalid.invalid>
Newsgroups: comp.lang.c,comp.lang.java.programmer
Subject: Re: Self-updating relationship
Date: Thu, 03 Sep 2015 13:03:47 -0400
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On 09/03/2015 12:16 PM, James Kuyper wrote:

> OK - I thought I was beginning to understand  what was going on, but now
> I'm thoroughly confused. You're saying that this behavior (Specifically,
> the behavior of re-calculating the subtraction each time
> spaces.getValue() is used) is a property of the
> javafx.beans.property.Property<T> interface, rather than a property of
> the javafx.beans.binding.Binding<T> interface, despite the fact that it
> happens when he uses javafx.beans.binding.NumberBinding, and doesn't
> happen when he uses javafx.beans.property.SimpleIntegerProperty?
>
> How does that work? Does javafx.beans.binding.NumberBinding use
> javafx.beans.property.Property<T> while
> javafx.beans.property.SimpleIntegerProperty uses
> javafx.beans.binding.Binding<T>? That's not at all what I would have
> expected, based solely upon the names.
>
>
Perhaps our discussion is going beside itself it the threads.
I would like to use the example code that I posted elsewhere
and neglect the javafx.beans.binding package, in particular
the NumberBinding interface if that is acceptable.

If so I will reproduce the example here.
You'll need access to the JavaFX documentation, located here:
With frames
<https://docs.oracle.com/javase/8/javafx/api/index.html?overview-summary.html>
No frames
<https://docs.oracle.com/javase/8/javafx/api/overview-summary.html>


import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;

public class Main
{ public static void main(String[] args)
   {

     final IntegerProperty height
     = new SimpleIntegerProperty();

     final IntegerProperty number
     = new SimpleIntegerProperty();

     final IntegerProperty spaces
     = new SimpleIntegerProperty();

     spaces.bind(height.subtract(number));

     height.set(10);
     number.set(2);
     System.out.print(spaces.get()); // 8

     spaces.unbind();
     height.set(20);
     System.out.print(spaces.get()); // 8

} }

Here spaces is a SimpleIntegerProperty, a subclass of
IntegerPropertyBase which is an implementation of the
Property<T> interface. IntegerPropertyBase is where the
Property.bind(ObservableValue<? extends T> observable) and
Property.unbind() are implemented.

The expression height.subtract(number) creates an
ObservableValue<Number>, through NumberExpression ( so much
for neglecting the javafx.beans.binding package) which
IntegerPropertyBase uses to bind height and number to spaces
as specified in his documentation.

As I stated elsewhere, the plethora of mixin interfaces
makes it difficult (for me) to discuss, but writing code
that uses it is simple.