com.vaadin.client.flow.reactive

Class Reactive

java.lang.Object

com.vaadin.client.flow.reactive.Reactive

public class Reactive
extends Object

Handles global features related to reactivity, such as keeping track of the current Computation, providing a lazy flush cycle and registering reactive event collectors.

With a reactive programming model, the dependencies needed for producing a result are automatically registered when the result is computed. When any dependency of a computation is changed, that computation is scheduled to be recomputed. To reduce the number of recomputations performed when many dependencies are updated, the recomputation is performed lazily the next time flush() is invoked.

Since:

1.0

Author:

Vaadin Ltd

See Also:

Computation

Method Summary

Modifier and Type	Method and Description
static elemental.events.EventRemover	addEventCollector(ReactiveValueChangeListener reactiveValueChangeListener) Adds a reactive change listener that will be invoked whenever a reactive change event is fired from any reactive event router.
static void	addFlushListener(FlushListener flushListener) Adds a listener that will be invoked the next time flush() is invoked.
static void	addPostFlushListener(FlushListener postFlushListener) Adds a listener that will be invoked during the next flush(), after all regular flush listeners have been invoked.
static void	flush() Flushes all flush listeners and post flush listeners.
static Computation	getCurrentComputation() Gets the currently active computation.
static void	notifyEventCollectors(ReactiveValueChangeEvent event) Fires a reactive change event to all registered event collectors.
static void	reset() Resets Reactive to the initial state.
static Computation	runWhenDependenciesChange(Command command) Evaluates the given command whenever there is a change in any ReactiveValue used in the command.
static void	runWithComputation(Computation computation, Command command) Runs a task with the given computation set as getCurrentComputation().

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

addFlushListener

public static void addFlushListener(FlushListener flushListener)

Adds a listener that will be invoked the next time flush() is invoked. A listener added during a flush will be invoked before that flush finishes.

Parameters:

flushListener - the flush listener to add

addPostFlushListener

public static void addPostFlushListener(FlushListener postFlushListener)

Adds a listener that will be invoked during the next flush(), after all regular flush listeners have been invoked. If a post flush listener adds new flush listeners, those flush listeners will be invoked before the next post flush listener is invoked.

Parameters:

postFlushListener - the listener to add

flush

public static void flush()

Flushes all flush listeners and post flush listeners. A listener is discarded after it has been invoked once. This means that there will be no listeners registered for the next flush at the time this method returns.

See Also:

addFlushListener(FlushListener), addPostFlushListener(FlushListener)

getCurrentComputation

public static Computation getCurrentComputation()

Gets the currently active computation. Any reactive value that is accessed when a computation is active should be added as a dependency to that computation so that the computation will be invalidated if the value changes.

Returns:

the current computation, or null if there is no current computation.

runWithComputation

public static void runWithComputation(Computation computation,
                                      Command command)

Runs a task with the given computation set as getCurrentComputation(). If another computation is set as the current computation, it is temporarily replaced by the provided computation, but restored again after the provided task has been run.

Parameters:

computation - the computation to set as current

command - the command to run while the computation is set as current

addEventCollector

public static elemental.events.EventRemover addEventCollector(ReactiveValueChangeListener reactiveValueChangeListener)

Adds a reactive change listener that will be invoked whenever a reactive change event is fired from any reactive event router.

Parameters:

reactiveValueChangeListener - the listener to add

Returns:

an event remover that can be used to remove the listener

notifyEventCollectors

public static void notifyEventCollectors(ReactiveValueChangeEvent event)

Fires a reactive change event to all registered event collectors.

Parameters:

event - the fired event

See Also:

addEventCollector(ReactiveValueChangeListener)

runWhenDependenciesChange

public static Computation runWhenDependenciesChange(Command command)

Evaluates the given command whenever there is a change in any ReactiveValue used in the command.

Parameters:

command - the command to run

Returns:

A Computation object which can be used to control the evaluation

reset

public static void reset()

Resets Reactive to the initial state.

Intended for test cases to call in setup to avoid having tests affect each other as Reactive state is static and shared.

Should never be called from non-test code!