@efesto-cloud/observable

A minimal observable value container — holds state, lets consumers read it, and notifies subscribers when it changes.

Use Observable when you need current value + updates. Use @efesto-cloud/publisher for fire-and-forget events without stored state.

Installation

pnpm add @efesto-cloud/observable @efesto-cloud/publisher

Quick Start

import { Observable } from "@efesto-cloud/observable";

const count = new Observable(0);

const off = count.subscribe((value) => {
    console.log("count changed:", value);
});

count.set(1); // logs: count changed: 1
count.get();  // 1

off();
count.dispose(); // removes all subscribers

API

interface IObservable<T> {
    get(): T;
    set(value: T): void;
    subscribe(callback: (value: T) => void): Unsubscribe;
    dispose(): void;
}

• new Observable(initialState) — seeded with a starting value.
• get() — current value.
• set(value) — replace the value and notify subscribers.
• subscribe(cb) — returns an Unsubscribe function.
• dispose() — unsubscribe every listener.

Rules

• If you only need events (no stored value), use Publisher instead.
• Always call the returned unsubscribe function, or dispose() when tearing down the owning object.
• set(value) always notifies — even if the new value is identical to the previous one. If you need deduped updates, layer Computed or check before calling set.

Example: shared state between components

const theme = new Observable<"light" | "dark">("light");

// Component A
const off = theme.subscribe((t) => applyTheme(t));

// Component B
theme.set("dark");

// On unmount
off();

Related

• @efesto-cloud/publisher — pub/sub without state.
• @efesto-cloud/compute — derive a value from one or more observables.