Package com.vaadin.flow.signals.impl

Class Effect

java.lang.Object
com.vaadin.flow.signals.impl.Effect
All Implemented Interfaces:
Serializable
public class Effect extends Object implements Serializable
Applies a side effect based on signal value changes. An effect is a callback that is initially run when the effect is created, and subsequently run again whenever any dependency changes. Dependencies are automatically registered for all signals that are read from the callback. The callback is run again whenever there's a change to any dependency. Dependencies are always updated based the signals read during the most recent invocation.
See Also:

  • Constructor Details

    • Effect

      public Effect(EffectAction action)
      Creates a signal effect with the given action and the default dispatcher. The action is run when the effect is created and is subsequently run again whenever there's a change to any signal value that was read during the last invocation.
      Parameters:
      action - the action to use, not null
      See Also:

    • Effect

      public Effect(EffectAction action, SerializableExecutor dispatcher)
      Creates a signal effect with the given action and a custom dispatcher. The action is run when the effect is created and is subsequently run again whenever there's a change to any signal value that was read during the last invocation. The dispatcher can be used to make sure changes are evaluated asynchronously or with some specific context available. The action itself needs to be synchronous to be able to track changes.
      Parameters:
      action - the action to use, not null
      dispatcher - the dispatcher to use when handling changes, not null

    • Effect

      public Effect(ContextualEffectAction action)
      Creates a context-aware signal effect with the given action and the default dispatcher. The action receives an EffectContext that provides information about why the effect is running (initial render, user request, or background change).
      Parameters:
      action - the context-aware action to use, not null
      See Also:

    • Effect

      public Effect(ContextualEffectAction action, SerializableExecutor dispatcher)
      Creates a context-aware signal effect with the given action and a custom dispatcher. The action receives an EffectContext that provides information about why the effect is running. The dispatcher can be used to make sure changes are evaluated asynchronously or with some specific context available. The action itself needs to be synchronous to be able to track changes.
      Parameters:
      action - the context-aware action to use, not null
      dispatcher - the dispatcher to use when handling changes, not null

  • Method Details

    • setOwnerUI

      public void setOwnerUI(@Nullable UI ui)
      Sets the owner UI for this effect. When set, background change detection compares UI.getCurrent() against this UI instead of only checking for the presence of a VaadinRequest. This allows effects to correctly detect changes triggered by another user's session on a shared signal.
      Parameters:
      ui - the owner UI, or null to fall back to VaadinRequest-based detection

    • setDispatcher

      public void setDispatcher(SerializableExecutor dispatcher)
      Sets the dispatcher to use for subsequent invalidation callbacks. This can be used to change the execution context before re-activating a passivated effect.
      Parameters:
      dispatcher - the new dispatcher to use, not null

    • passivate

      public void passivate()
      Passivates this effect by removing all dependency listeners while preserving the tracked usages. The effect can later be re-activated with activate(), which will check if any tracked values have changed and only re-run the callback if needed.

    • activate

      public void activate()
      Re-activates a previously passivated effect. If any tracked signal has changed since passivation, the effect callback is re-run with EffectContext.isInitialRun() returning true. If nothing has changed, the effect simply re-registers its dependency listeners without running the callback.

    • dispose

      public void dispose()
      Disposes this effect by unregistering all current dependencies and preventing the action from running again.