computed<T> function

ReadonlySignal<T> computed<T>(ComputedCallback<T> compute, { String? debugLabel, })

Data is often derived from other pieces of existing data. The computed function lets you combine the values of multiple signals into a new signal that can be reacted to, or even used by additional computeds. When the signals accessed from within a computed callback change, the computed callback is re-executed and its new return value becomes the computed signal's value.

import 'package:preact_signals/preact_signals.dart';

final name = signal("Jane");
final surname = signal("Doe");

final fullName = computed(() => name.value + " " + surname.value);

// Logs: "Jane Doe"
print(fullName.value);

// Updates flow through computed, but only if someone
// subscribes to it. More on that later.
name.value = "John";
// Logs: "John Doe"
print(fullName.value);

Any signal that is accessed inside the computed's callback function will be automatically subscribed to and tracked as a dependency of the computed signal.

Implementation

ReadonlySignal<T> computed<T>(
  ComputedCallback<T> compute, {
  String? debugLabel,
}) {
  final instance = Computed<T>(compute, debugLabel: debugLabel);
  _onComputedCreated(instance);
  return instance;
}