Package com.inductiveautomation.perspective.gateway.driven

Interface DrivenValue<T>

Type Parameters:
T - The type of the driven value
All Known Implementing Classes:
AbstractStaticDrivenValue, ExpressionDrivenQualifiedValue, ExpressionDrivenStringValue, ExpressionDrivenValue, LockGuardedDrivenValue, LockGuardedDrivenValueCollection
public interface DrivenValue<T>
A DrivenValue contains a value which can change (driven by some source). It has startup() and shutdown() hooks to allow the implementation to prepare / tear down its instance. The value may be fetched by calling getAndClear() which will fetch the current value and reset its dirty state to false. Clients should always startup() before using the instance. Before fetching the latest value, isReady() must be checked and must return true. If isDirty() returns false, the last value fetched is the latest value which will be returned on the next call to getAndClear(). When finished with the instance, shutdown() must be called to clean up.

  • Method Summary

    Modifier and Type
    Method
    Description
    Optional<T>
    getAndClear()
    Fetch the current driven value
    boolean
    isDirty()
     
    boolean
    isReady()
     
    default Collection<PropertyReference>
    resolveReferences()
    Call before startup() to resolve and collect any references this value might depend on.
    void
    shutdown()
    Lifecycle hook to shut down the driven value
    void
    startup()
    Lifecycle hook to start up the driven value

  • Method Details

    • startup

      void startup()
      Lifecycle hook to start up the driven value

    • shutdown

      void shutdown()
      Lifecycle hook to shut down the driven value

    • resolveReferences

      default Collection<PropertyReference> resolveReferences()
      Call before startup() to resolve and collect any references this value might depend on.

    • isReady

      boolean isReady()
      Returns:
      true if the driven value is ready to fetch

    • isDirty

      boolean isDirty()
      Returns:
      true if the driven value has changed since the last time it was fetched

    • getAndClear

      @Nonnull Optional<T> getAndClear()
      Fetch the current driven value
      Returns:
      An Optional containing the current driven value, if present, or an empty Optional if the driven value is null / not present.