# Watchable

**Kind:** Class

Abstract superclass for watchable models. All watchable models expose `watch`
and `unwatch` methods that allow consumers to subscribe to changes to that model.

This class should not be used directly.

## Methods

### `unwatch(keys, callback, context?)`

Unwatch keys watched with `.watch`.

Should be called with the same arguments given to `.watch`.

Returns the array of keys that were unwatched.

**Parameters:**
- `keys` (`WatchableKey | ReadonlyArray<WatchableKey>`) — the keys to unwatch
- `callback` (`object`) — the function passed to `.watch` for these keys
- `context?` (`FlowAnyObject | null`) — the context that was passed to `.watch` for this `callback`

**Returns:** `Array<WatchableKey>`

### `watch(keys, callback, context?)`

Get notified of changes to the model.

Every call to `.watch` should have a matching call to `.unwatch`.

Returns the array of keys that were watched.

**Parameters:**
- `keys` (`WatchableKey | ReadonlyArray<WatchableKey>`) — the keys to watch
- `callback` (`object`) — a function to call when those keys change
- `context?` (`FlowAnyObject | null`) — an optional context for `this` in `callback`.

**Returns:** `Array<WatchableKey>`