Creating Clearer Method Names & Concepts (original) (raw)

Richard Bair richard.bair at oracle.com
Fri Nov 2 14:24:41 PDT 2012

Binding in JavaFX is certainly another source of confusion. You have "binding" and you have "Binding":

A Property has a method "bind", of which the doc says: "Create a unidirection binding for this Property." While there is also the interface Binding, of which the doc says: "A Binding calculates a value that depends on one or more sources."

I guess I didn't see these as different, as the "bind" method uses a Binding (or just listens to it if it is of the right type):

public void bind(final ObservableValue<? extends Number> rawObservable) {
    if (rawObservable == null) {
        throw new NullPointerException("Cannot bind to null");
    }

    ObservableIntegerValue newObservable;
    if (rawObservable instanceof ObservableIntegerValue) {
        newObservable = (ObservableIntegerValue)rawObservable;
    } else if (rawObservable instanceof ObservableNumberValue) {
        final ObservableNumberValue numberValue = (ObservableNumberValue)rawObservable;
        newObservable = new IntegerBinding() {
            {
                super.bind(rawObservable);
            }

            @Override
            protected int computeValue() {
                return numberValue.intValue();
            }
        };
    } else {
        newObservable = new IntegerBinding() {
            {
                super.bind(rawObservable);
            }

            @Override
            protected int computeValue() {
                final Number value = rawObservable.getValue();
                return (value == null)? 0 : value.intValue();
            }
        };
    }

    if (!newObservable.equals(observable)) {
        unbind();
        observable = newObservable;
        if (listener == null) {
            listener = new Listener();
        }
        observable.addListener(listener);
        markInvalid();
    }
}

So the "bind" method is just shorthand, really, for using Bindings on that property.

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