Simple bound properties with lambda expressions

As I am climbing the learning curve, I find myself to write code such as

      more.disableProperty().bind(model.temperatureProperty()
         .greaterThanOrEqualTo(100));
      gauge.widthProperty().bind(model.temperatureProperty()
         .multiply(4));

I can see why he must accumulate these trees of expression with methods such as greaterThanOrEqualTo and multiply , but it seems a bit tedious. So, I thought: why not let the lambdas at work? Feed properties and a lambda that says how they should be evaluated when they change. Like this:

      more.disableProperty().bind(observe(model.temperatureProperty(),
            t -> t >= 100));
      gauge.widthProperty().bind(observe(model.temperatureProperty(),
            t -> 4 * t));

It's maybe just me, but I find it easier on the eyes. The implementation of observe is trivial:

   static class Binding1<T, R> extends ObservableValueBase {
      private ObservableValue<T> obs;
      private Function<T, R> fun;
      
      public Binding1(ObservableValue<T> obs, Function<T, R> fun) {
         this.obs = obs;
         this.fun = fun;
         obs.addListener(o -> fireValueChangedEvent());         
      }

      public R getValue() {
         return fun.apply(obs.getValue());
      }
   }

   public static <T, R> ObservableValue<R> observe(ObservableValue<T> obs, Function<T, R> fun) {
      return new Binding1<T, R>(obs, fun);
   }

We could use a couple more of these functions to handle the lambdas with 2 and maybe 3 to 4 parameters.

With this approach, there is no real need to use such things as DoubleProperty because you can do assessments in the lambda and don't need a bunch of methods to replicate the arithmetic operations.

Someone has already thought along those lines, or am I innovate here? Or I forgot something that would condemn this approach?

The class of links has a bunch of useful methods to create links, including createObjectBinding (...), which I think is more or less what you are looking for here:

import javafx.beans.binding.Bindings;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.DoubleProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.property.SimpleDoubleProperty;

public class BindingsWithLambdaTest {

  public static void main(String[] args) {
    final DoubleProperty temp = new SimpleDoubleProperty();
    final BooleanProperty more = new SimpleBooleanProperty();
    final DoubleProperty gauge = new SimpleDoubleProperty();

    more.bind(Bindings.createObjectBinding(
        () -> temp.doubleValue() >= 100,
        temp)
    );
    gauge.bind(Bindings.createObjectBinding(
        () -> 4*temp.doubleValue(),
        temp)
    ); 

    more.addListener(
        (observable, oldValue, newValue) -> System.out.printf("more changed from %s to %s%n", oldValue, newValue)
    );
    gauge.addListener(
        (observable, oldValue, newValue) -> System.out.printf("gauge changed from %.1f to %.1f%n", oldValue.doubleValue(), newValue.doubleValue())
    );

    temp.set(10);
    temp.set(40);
    temp.set(110);
  }

}

Post edited by: James_D (additional code example)

Tags: Java

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