Apa iku state machine lan kapan ngewandake dhéwé?

Question

Accepted Answer

Sawijining **state machine** modélan sistem minangka saperangan cacahing **state** plus **transisi** sing diidini antarane. Tinimbang juggling flag boolean sing mandiri, sampeyan nemtokake kanthi sakumrawat dene state apa wae sing ana lan transisi apa sing legal — nggawe state sing ora bisa kawakili.

## Masalah: boolean soup

```js
// ❌ multiple booleans → 2^n combinations, many of them invalid
const [isLoading, setLoading] = useState(false);
const [isError, setError] = useState(false);
const [isSuccess, setSuccess] = useState(false);
// { isLoading: true, isError: true, isSuccess: true } — nonsense, but POSSIBLE
```

Karo flag mandiri, ora ana sing nutup kombinasi kontradiktif, lan sampeyan kudu ngandal-andal njaga konsistensi saben transisi — magnet bug.

## Model state-machine

```text
States:      idle → loading → success
                       ↓
                     error → (retry) → loading

Only defined transitions are allowed; you can't be in two states at once.
```

```js
const machine = {
  idle:    { FETCH: "loading" },
  loading: { SUCCESS: "success", ERROR: "error" },
  success: { FETCH: "loading" },
  error:   { RETRY: "loading" },
};
function transition(current, event) {
  return machine[current][event] ?? current; // only legal transitions happen
}
```

Variabel `state` tunggal nampung state saiki; `event` ngaktifake transisi sing *ditemtokake*. Transisi ilegal (ex: SUCCESS nalika idle) ora bisa uga kedadeyan — state sing ora bisa kasil wis ilang kanthi desain.

## Tooling nyata: XState

```js
// libraries like XState formalize this with guards, actions, nested/parallel states
const toggleMachine = createMachine({
  initial: "inactive",
  states: {
    inactive: { on: { TOGGLE: "active" } },
    active:   { on: { TOGGLE: "inactive" } },
  },
});
```

## Kapan state machine ngewandake dhéwé

```text
✓ Complex flows with many states: checkout, multi-step forms/wizards, media players
✓ Authentication flows (logged out → logging in → logged in → refreshing)
✓ Anything where invalid state combinations cause bugs
✗ Overkill for simple toggles or trivial state
```

## Mengapa iku penting

State machine ndadekake rigor marang logika stateful kompleks kanthi nggawe **state sing ora valid iku mustahil** lan transisi **eksplisit** — nggantos kombinasi boolean sing rapuh karo model sing jelas lan gampang.

Partikular bisa digunakake kanggo alur sing rumit (wizard, bayaran, otentikasi, media) ing ngendi boolean soup ndudut menapa sing halus lan angel dipundhut maneh.

Sanajan informal (enum `status`) gagasan nambah-nambah state asinkron; formal (XState) ndadekake logika sing bisa dipingeni, bisa diuji, lan kuwat.

Ngerti kapan bakal ngambil mau punika tandha saka desain state dewasa.