uk.co.strangeskies.observable

Interface ObservableValue<T>

Type Parameters:

T - the type of the value

All Superinterfaces:

Observable<T>

All Known Subinterfaces:

LocaleManager, LocaleProvider, Localized<T>, ObservableProperty<T>

All Known Implementing Classes:

ImmutableObservableValue, LocaleManagerService, ObservablePropertyImpl

public interface ObservableValue<T>
extends Observable<T>

A value which can be fetched and observed for updates and changes.

Observable value adheres to the contract of Observable, with a few extra restrictions on its behavior to conform to the semantics of a mutable value.

An instance may send a completion event to indicate that it will not mutate beyond that point, but it should only send this to an observer if it has already sent them a message event containing the current value.

The value may enter an error state, in which case observers will receive a failure event and subsequent calls to get() should throw a MissingValueException as per Observable.get() until a new valid value is available.

A common example of an error state may be NullPointerException when there is no value available.

The observable should always be primed with either a message event or a failure event immediately upon instantiation, and observers which subscribe to the observable should receive the last such event directly subsequent to observation. This means that the get() method inherited from observable should never have to block.

Observable values should never support backpressure.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	ObservableValue.Change<T> A value change event.

Method Summary

Modifier and Type	Method and Description
Observable<ObservableValue.Change<T>>	changes()
T	get() Immediately resolve the current value if one exists, otherwise throw a MissingValueException with a cause representing the current failure state.
default java.lang.Throwable	getProblem()
default boolean	isEqual(T value)
default boolean	isMatching(java.util.function.Predicate<? super T> value)
default boolean	isValid()
default java.util.Optional<T>	tryGet() Immediately resolve the current value, if one exists.
default java.util.Optional<java.lang.Throwable>	tryGetProblem()

Methods inherited from interface uk.co.strangeskies.observable.Observable

aggregateBackpressure, aggregateBackpressure, collect, collectBackpressure, compose, concat, concat, concatMap, dropWhile, empty, executeOn, failingValue, filter, flatMap, getNext, map, materialize, merge, merge, mergeMap, observe, observe, of, of, of, reduce, reduceBackpressure, reduceBackpressure, reduceBackpressure, repeating, requestNext, requestUnbounded, retrying, softReference, softReference, synchronize, synchronize, takeWhile, then, thenAfter, toObservable, toValue, toValue, toValue, upcast, value, weakReference, weakReference

Method Detail

get

T get()

Immediately resolve the current value if one exists, otherwise throw a MissingValueException with a cause representing the current failure state.

Specified by:

get in interface Observable<T>

Returns:

the current value

tryGet

default java.util.Optional<T> tryGet()

Immediately resolve the current value, if one exists.

Specified by:

tryGet in interface Observable<T>

Returns:

an optional containing the current value, or an empty option if no value is available

isValid

default boolean isValid()

isEqual

default boolean isEqual(T value)

isMatching

default boolean isMatching(java.util.function.Predicate<? super T> value)

getProblem

default java.lang.Throwable getProblem()

tryGetProblem

default java.util.Optional<java.lang.Throwable> tryGetProblem()

changes

Observable<ObservableValue.Change<T>> changes()

Returns:

an observable over changes to the value