On Sun, 9 Jul 2023 18:48:16 GMT, Jose Pereda <jper...@openjdk.org> wrote:
>> John Hendrikx has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> Add newline at end of ConditionalBinding file
>
> modules/javafx.base/src/main/java/javafx/beans/Observable.java line 110:
>
>> 108: default Subscription subscribe(Runnable subscriber) {
>> 109: Objects.requireNonNull(subscriber, "subscriber cannot be null");
>> 110: InvalidationListener listener = obs -> subscriber.run();
>
> InvalidationListeners are widely used in this pattern:
>
>
> javaFXProperty.addListener(new InvalidationListener() {
> @Override
> public void invalidated(Observable observable) {
> if (value.get() != null) {
> // do something
> javaFXProperty.removeListener(this);
> }
> }
> });
>
>
> Does subscribe/unsubscribe allows something like this?
The new `subscribe` methods don't support this usage, but they're also not
intended to replace the old methods. Cases like the one you show above, but
also cases where a single listener is registered on many properties still are
best handled using the `addListener`/`removeListener` methods. I consider them
more advanced usage which you are more likely to encounter in the internals of
JavaFX or libraries.
I don't see this pattern that often though, but I know it exists as removing
listeners during notification is something that `ExpressionHelper` specifically
needs to deal with (also see https://github.com/openjdk/jfx/pull/1081 where I'm
advocating for a better `ExpressionHelper` that provides correct old values
when dealing with nested notifications and listener list changes).
I suppose you could still do this in a hacky way:
private Subscription subscription;
{
subscription = property.subscribe(() -> {
if (condition) {
this.subscription.unsubscribe();
}
});
}
-------------
PR Review Comment: https://git.openjdk.org/jfx/pull/1069#discussion_r1257538675
