I also think this will be a useful feature to get into JavaFX.
As for the name of the method, the only one of them I don't like is
"conditionOn". That name doesn't suggest (to me anyway) what its purpose
is. I think any of the ones with "when" in the name would work. I have a
slight preference for "updateWhen", but could be talked into one of the
others.
-- Kevin
On 11/14/2022 6:52 AM, John Hendrikx wrote:
Hi,
I'm working on https://github.com/openjdk/jfx/pull/830 where I asked
for some opinions on the naming of a new method I'd like to introduce
in ObservableValue.
I wrote a (perhaps too large) comment about the possible names and
rationales:
https://github.com/openjdk/jfx/pull/830#issuecomment-1304846220
I'd like to ask what others think what would be a good name for this
new method (Observable#when in the PR) in order to move the PR
forward, as I think it offers a very compelling feature to JavaFX
(moving from weak reference to deterministic behavior when it comes to
listener management). My opinion has always been that using weak
listeners for listener management is a crutch that relies far too much
on the internal workings of the JVM and Garbage Collector which offer
no guarantees as to the timely clean up of these references and the
listeners related to them.
Leading contenders are (but not limited to these, if you have a better
name):
1) conditionOn
2) updateWhen
3) when
4) whenever
Usage in code is nearly always going to be something like these
constructs:
// keeps text property in sync with longLivedProperty when label
is shown:
label.textProperty().bind(longLivedProperty.**when**(label::isShownProperty));
// keeps text property in sync with longLivedProperty when
container is shown:
label.textProperty().bind(longLivedProperty.**when**(container::isShownProperty));
It can also be used to make a listener only actively listen when a
condition is met (the listener is added/removed immediately when the
condition changes, facilitating GC):
// listen to changes of longLivedProperty when container is shown:
longLivedProperty.when(container::isShownProperty)
.addListener((obs, old, current) -> { ... change listener
... });
Or it can be used to disable updates temporarily (or permanently):
BooleanProperty allowUpdates = new SimpleBooleanProperty(true)
// keeps text property in sync when updates are allowed:
name.textProperty().bind(model.title.when(allowUpdates));
detail.textProperty().bind(model.subtitle.when(allowUpdates));
asyncImageProperty.imageHandleProperty().bind(model.imageHandle.when(allowUpdates));
This last example can be useful in Skin#dispose, but has uses outside
of skins as well, for example when you want to prevent updates until
things have settled down.
Thanks for reading!
--John
