On Thu, 30 Jun 2022 06:57:03 GMT, John Hendrikx <jhendr...@openjdk.org> wrote:
>> This is an implementation of the proposal in >> https://bugs.openjdk.java.net/browse/JDK-8274771 that me and Nir Lisker >> (@nlisker) have been working on. It's a complete implementation including >> good test coverage. >> >> This was based on https://github.com/openjdk/jfx/pull/434 but with a smaller >> API footprint. Compared to the PoC this is lacking public API for >> subscriptions, and does not include `orElseGet` or the `conditionOn` >> conditional mapping. >> >> **Flexible Mappings** >> Map the contents of a property any way you like with `map`, or map nested >> properties with `flatMap`. >> >> **Lazy** >> The bindings created are lazy, which means they are always _invalid_ when >> not themselves observed. This allows for easier garbage collection (once the >> last observer is removed, a chain of bindings will stop observing their >> parents) and less listener management when dealing with nested properties. >> Furthermore, this allows inclusion of such bindings in classes such as >> `Node` without listeners being created when the binding itself is not used >> (this would allow for the inclusion of a `treeShowingProperty` in `Node` >> without creating excessive listeners, see this fix I did in an earlier PR: >> https://github.com/openjdk/jfx/pull/185) >> >> **Null Safe** >> The `map` and `flatMap` methods are skipped, similar to `java.util.Optional` >> when the value they would be mapping is `null`. This makes mapping nested >> properties with `flatMap` trivial as the `null` case does not need to be >> taken into account in a chain like this: >> `node.sceneProperty().flatMap(Scene::windowProperty).flatMap(Window::showingProperty)`. >> Instead a default can be provided with `orElse`. >> >> Some examples: >> >> void mapProperty() { >> // Standard JavaFX: >> label.textProperty().bind(Bindings.createStringBinding(() -> >> text.getValueSafe().toUpperCase(), text)); >> >> // Fluent: much more compact, no need to handle null >> label.textProperty().bind(text.map(String::toUpperCase)); >> } >> >> void calculateCharactersLeft() { >> // Standard JavaFX: >> >> label.textProperty().bind(text.length().negate().add(100).asString().concat(" >> characters left")); >> >> // Fluent: slightly more compact and more clear (no negate needed) >> label.textProperty().bind(text.orElse("").map(v -> 100 - v.length() + >> " characters left")); >> } >> >> void mapNestedValue() { >> // Standard JavaFX: >> label.textProperty().bind(Bindings.createStringBinding( >> () -> employee.get() == null ? "" >> : employee.get().getCompany() == null ? "" >> : employee.get().getCompany().getName(), >> employee >> )); >> >> // Standard JavaFX + Optional: >> label.textProperty().bind(Bindings.createStringBinding( >> () -> Optinal.ofNullable(employee.get()) >> .map(Employee::getCompany) >> .map(Company::getName) >> .orElse(""), >> employee >> )); >> >> // Fluent: no need to handle nulls everywhere >> label.textProperty().bind( >> employee.map(Employee::getCompany) >> .map(Company::getName) >> .orElse("") >> ); >> } >> >> void mapNestedProperty() { >> // Standard JavaFX: >> label.textProperty().bind( >> Bindings.when(Bindings.selectBoolean(label.sceneProperty(), >> "window", "showing")) >> .then("Visible") >> .otherwise("Not Visible") >> ); >> >> // Fluent: type safe >> label.textProperty().bind(label.sceneProperty() >> .flatMap(Scene::windowProperty) >> .flatMap(Window::showingProperty) >> .orElse(false) >> .map(showing -> showing ? "Visible" : "Not Visible") >> ); >> } >> >> Note that this is based on ideas in ReactFX and my own experiments in >> https://github.com/hjohn/hs.jfx.eventstream. I've come to the conclusion >> that this is much better directly integrated into JavaFX, and I'm hoping >> this proof of concept will be able to move such an effort forward. > > John Hendrikx has updated the pull request incrementally with five additional > commits since the last revision: > > - Move private binding classes to com.sun.javafx.binding package > - Add note to Bindings#select to consider ObservableValue#flatMap > - Fix bug invalidation bug in FlatMappedBinding > > Also fixed a secondary issue where the indirect source of the binding > was unsubscribed and resubscribed each time its value was recomputed. > > Add additional comments to clarify how FlatMappedBinding works. > > Added test cases for these newly discovered issues. > - Fix typos in LazyObjectBinding > - Rename observeInputs to observeSources This looks quite good now. I believe the API is ready to go. I did a little testing and want to do some more tomorrow, and then hope to finish my review. I left a couple comments / questions inline. Two overall comments: 1. The doc changes in Bindings.java should be added to the Specification section in the CSR. 2. The copyright line for each new file should be: * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved. with a comma after the year. modules/javafx.base/src/main/java/com/sun/javafx/binding/FlatMappedBinding.java line 2: > 1: /* > 2: * Copyright (c) 2021 Oracle and/or its affiliates. All rights reserved. That should be `2022,` with a comma after the year in addition to fixing the year. modules/javafx.base/src/main/java/com/sun/javafx/binding/Subscription.java line 90: > 88: */ > 89: static <T> Subscription subscribe(ObservableValue<T> observableValue, > Consumer<? super T> subscriber) { > 90: ChangeListener<T> listener = (obs, old, current) -> > subscriber.accept(current); Maybe call `Objects.requireNonNull()` on `observableValue` and `subscriber` before creating the listener? modules/javafx.base/src/main/java/com/sun/javafx/binding/Subscription.java line 110: > 108: */ > 109: static Subscription subscribeInvalidations(ObservableValue<?> > observableValue, Runnable runnable) { > 110: Objects.requireNonNull(runnable); Maybe also call `Objects.requireNonNull(observableValue)` here? modules/javafx.base/src/main/java/javafx/beans/binding/Bindings.java line 443: > 441: * Since 19, it is recommended to use {@link > ObservableValue#flatMap(java.util.function.Function)} > 442: * to select a nested member of an {@link ObservableValue}. > 443: * </p> This should be added to the CSR. ------------- PR: https://git.openjdk.org/jfx/pull/675
