On Tue, 22 Mar 2022 07:46:40 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 one additional > commit since the last revision: > > Fix wording I reviewed the public API changes, and this looks like a great addition to JavaFX bindings. I think there might be time to get this into JavaFX 19, presuming that there are no issues with the testing or implementation, so let's proceed down that path. I left one comment on the API docs as well as pointed out the public methods that will need an `@since 19` javadoc tag. Once that is updated you can propagate the javadoc changes to the CSR (including the `@since` tags) and move it to "Proposed". I'll formally review it later, once the code review is closer to being done. modules/javafx.base/src/main/java/javafx/beans/binding/ObjectBinding.java line 198: > 196: * @return {@code true} if this binding currently has one or more > 197: * listeners registered on it, otherwise {@code false} > 198: */ This needs an `@since` tag. Presuming that this makes JavaFX 19, that would be: * @since 19 modules/javafx.base/src/main/java/javafx/beans/binding/ObjectBinding.java line 213: > 211: * > 212: * @return {@code true} if this binding is allowed to become valid, > otherwise > 213: * {@code false} Needs an `@since` tag. modules/javafx.base/src/main/java/javafx/beans/value/ObservableValue.java line 166: > 164: * mapping function on this value, or {@code null} when it > 165: * is {@code null}; never returns {@code null} > 166: * @throws NullPointerException if the mapping function is {@code > null} Needs an `@since` tag. modules/javafx.base/src/main/java/javafx/beans/value/ObservableValue.java line 192: > 190: * holds {@code null}; can be {@code null} > 191: * @return an {@code ObservableValue} that holds this value, or the > given constant if > 192: * it is {@code null}; never returns {@code null} Needs an `@since` tag. modules/javafx.base/src/main/java/javafx/beans/value/ObservableValue.java line 205: > 203: * resulting value is {@code null}. If the mapping resulted in > {@code null}, then the > 204: * resulting value is also {@code null}. > 205: * <p> It might be worth borrowing some language from `Optional::flatMap`. Maybe something like this? This method is similar to {@link #map(Function)}, but the mapping function is one whose result is already an ObservableValue, and if invoked, flatMap does not wrap it within an additional ObservableValue. modules/javafx.base/src/main/java/javafx/beans/value/ObservableValue.java line 239: > 237: * {@code null} when the value is {@code null}; never returns > {@code null} > 238: * @throws NullPointerException if the mapping function is {@code > null} > 239: */ This also needs an `@since` tag. ------------- PR: https://git.openjdk.java.net/jfx/pull/675
