signals

What problem does it solve?

Vaadin Signals removes the need for manual listener management and brittle update code by providing a reactive, transactional, and thread-safe approach to UI state in Vaadin 25 Flow. It makes it simple to keep component views, element properties, and cross-user shared state consistent and automatically updated while handling lifecycle attach/detach and concurrency concerns.

Core Features & Use Cases

• Reactive primitive signals (ValueSignal, NumberSignal) and collections (ListSignal, MapSignal, NodeSignal) for representing application state.
• SignalFactory scoping for IN_MEMORY_SHARED (cross-user, JVM-scoped) and IN_MEMORY_EXCLUSIVE (per-instance) usages, with guidance on when to enable Push.
• ComponentEffect bindings and computed signals to derive values and bind state to component properties, text, classes, attributes, and styles with automatic lifecycle management.
• Transactions and atomic update patterns to group changes, use peek() for non-tracking reads, and avoid modifying objects in place.
• Use cases: shared counters and collaborative widgets, signal-backed form editors, computed derived displays, and element-level bindings for dynamic styling and visibility.

Quick Start

Create a ValueSignal or NumberSignal with SignalFactory (choose IN_MEMORY_SHARED for shared state or IN_MEMORY_EXCLUSIVE for local state), bind it to your components with ComponentEffect.bind or ComponentEffect.effect, and use Signal.runInTransaction for atomic multi-signal updates.