Package com.inductiveautomation.perspective.gateway.driven

Class ExpressionDrivenValue<T>

java.lang.Object

com.inductiveautomation.perspective.gateway.driven.LockGuardedDrivenValue<T>

com.inductiveautomation.perspective.gateway.driven.ExpressionDrivenValue<T>

Type Parameters:

T - The type of the driven value

All Implemented Interfaces:

DrivenValue<T>

Direct Known Subclasses:

ExpressionDrivenQualifiedValue, ExpressionDrivenStringValue

public abstract class ExpressionDrivenValue<T>
extends LockGuardedDrivenValue<T>

An ExpressionDrivenValue is a LockGuardedDrivenValue driven by a PerspectiveExpression. The injected valueChangedCallback is called by a Thread holding the injected lock object when a new value is emitted from the expression and it passes validation. Derived classes get to decide what passing validation means.

Field Summary

Fields

Modifier and Type	Field	Description
protected boolean	dirty
protected QualifiedValue	value

Fields inherited from class com.inductiveautomation.perspective.gateway.driven.LockGuardedDrivenValue

lock

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ExpressionDrivenValue(Object lock, PerspectiveExpression expr, Runnable valueChangedCallback)

Method Summary

Modifier and Type	Method	Description
Optional<T>	getAndClear()	Fetch the current driven value
protected boolean	isDirtyInternal()	Called after asserting that the calling thread holds the injected lock.
protected boolean	isReadyInternal()	Called after asserting that the calling thread holds the injected lock.
protected abstract boolean	isValidValue(QualifiedValue value)	This method is called when a new value is emitted from the expression.
protected Collection<PropertyReference>	resolveReferencesInternal()
void	shutdown()	Lifecycle hook to shut down the driven value
void	startup()	Lifecycle hook to start up the driven value

Methods inherited from class com.inductiveautomation.perspective.gateway.driven.LockGuardedDrivenValue

getAndClearInternal, isDirty, isReady, resolveReferences

Methods inherited from class java.lang.Object

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

Field Details

value

protected QualifiedValue value

dirty

protected boolean dirty

Constructor Details

ExpressionDrivenValue

protected ExpressionDrivenValue(@Nonnull
 Object lock,
 @Nonnull
 PerspectiveExpression expr,
 @Nonnull
 Runnable valueChangedCallback)

Method Details

isValidValue

protected abstract boolean isValidValue(QualifiedValue value)

This method is called when a new value is emitted from the expression. If the value passes validation, the value is set, dirty bits are set, and the callback is notified. If the value does not pass validation, nothing happens and a debug message is logged.

Parameters:

value - the latest value emitted from the expression

Returns:

true if the value passes validation, false otherwise

isReadyInternal

protected boolean isReadyInternal()

Description copied from class: LockGuardedDrivenValue

Called after asserting that the calling thread holds the injected lock.

Specified by:

isReadyInternal in class LockGuardedDrivenValue<T>

See Also:

• LockGuardedDrivenValue.isReady()

isDirtyInternal

protected boolean isDirtyInternal()

Description copied from class: LockGuardedDrivenValue

Called after asserting that the calling thread holds the injected lock.

Specified by:

isDirtyInternal in class LockGuardedDrivenValue<T>

See Also:

• LockGuardedDrivenValue.isDirty()

startup

public void startup()

Description copied from interface: DrivenValue

Lifecycle hook to start up the driven value

shutdown

public void shutdown()

Description copied from interface: DrivenValue

Lifecycle hook to shut down the driven value

resolveReferencesInternal

protected Collection<PropertyReference> resolveReferencesInternal()

Specified by:

resolveReferencesInternal in class LockGuardedDrivenValue<T>

getAndClear

@Nonnull
public Optional<T> getAndClear()

Description copied from interface: DrivenValue

Fetch the current driven value

Specified by:

getAndClear in interface DrivenValue<T>

Overrides:

getAndClear in class LockGuardedDrivenValue<T>

Returns:

An Optional containing the current driven value, if present, or an empty Optional if the driven value is null / not present.