com.vaadin.client.flow.reactive

Class Computation

java.lang.Object

com.vaadin.client.flow.reactive.Computation

All Implemented Interfaces:

ReactiveValueChangeListener

public abstract class Computation
extends Object
implements ReactiveValueChangeListener

Automatically reruns doRecompute() whenever any reactive value used by it changes. The recompute method is invoked by the next invocation of Reactive.flush(), unless it has been invoked manually before the global flush. A computation is also scheduled to for an initial "recomputation" when it is created.

Since:

1.0

Author:

Vaadin Ltd

Constructor Summary

Constructors

Constructor and Description
Computation() Creates a new computation.

Method Summary

Modifier and Type	Method and Description
void	addDependency(ReactiveValue dependency) Adds a dependency to a reactive value.
protected abstract void	doRecompute() Does the actual recomputation.
boolean	isInvalidated() Checks whether this computation is invalidated.
void	onNextInvalidate(InvalidateListener listener) Adds an invalidate listener that will be invoked the next time this computation is invalidated.
void	onValueChange(ReactiveValueChangeEvent changeEvent) Invoked when a reactive value has changed.
void	recompute() Recomputes this computation.
void	stop() Stops this computation, so that it will no longer be recomputed.

Methods inherited from class java.lang.Object

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

Constructor Detail

Computation

public Computation()

Creates a new computation.

Method Detail

addDependency

public void addDependency(ReactiveValue dependency)

Adds a dependency to a reactive value. This computation is scheduled for recomputation when any dependency fires a change event. All previous dependencies are cleared before recomputing.

This method is automatically called when a reactive value is used for recomputing this computation. The developer is not expected to call this method himself.

Parameters:

dependency - the reactive value to depend on

onValueChange

public void onValueChange(ReactiveValueChangeEvent changeEvent)

Description copied from interface: ReactiveValueChangeListener

Invoked when a reactive value has changed.

Specified by:

onValueChange in interface ReactiveValueChangeListener

Parameters:

changeEvent - the change event

stop

public void stop()

Stops this computation, so that it will no longer be recomputed.

isInvalidated

public boolean isInvalidated()

Checks whether this computation is invalidated. An invalidated computation will eventually be recomputed (unless it has also been stopped). Recomputation will happen the next time recompute() or Reactive.flush() is invoked.

Returns:

true if this computation is invalidated; otherwise false

recompute

public void recompute()

Recomputes this computation.

doRecompute

protected abstract void doRecompute()

Does the actual recomputation. This method is run in a way that automatically registers dependencies to any reactive value accessed.

onNextInvalidate

public void onNextInvalidate(InvalidateListener listener)

Adds an invalidate listener that will be invoked the next time this computation is invalidated.

Parameters:

listener - the listener to run on the next invalidation