use

What it does

use is the low-level entry point behind every built-in hook. It registers an immutable Hook<R> at the current call position and returns the value built by its HookState.

Choose this API when composition cannot express a resource lifecycle. initHook initializes once, didUpdateHook receives new configuration, setState rebuilds the owner, and dispose releases resources. Most application hooks should instead compose primitives in a top-level use... function.

Signature and parameters

R use<R>(Hook<R> hook)

hook is immutable configuration for one call position. Its runtime type and ordered keys determine whether the existing HookState is preserved. The return value is the R produced by HookState.build.

Usage

class CounterHook extends Hook<int> {
  const CounterHook();

  @override
  CounterHookState createState() => CounterHookState();
}

class CounterHookState extends HookState<int, CounterHook> {
  var count = 0;

  void increment() => setState(() => count++);

  @override
  int build(BuildContext context) => count;
}

int useRawCounter() => use(const CounterHook());

Live demo

Interactive use demo

Custom HookState value: 0

Ownership and lifecycle

The runtime owns the created HookState and forwards initHook, didUpdateHook, deactivate, and reverse-order dispose. Custom state owns every resource it creates and must release it synchronously. Cleanup failures are isolated and reported through the Jaspr binding.

Server rendering

A custom hook runs wherever its owning hook component builds. Keep server initialization deterministic and guard browser-only resources with context.binding.isClient.

Common mistakes

Do not call use outside a hook host build or vary its position conditionally. Do not expose private element internals; Hook and HookState are the supported extension points. Prefer composition unless a resource needs a lifecycle primitive that built-in hooks cannot express.

Start with Writing custom hooks. See useEffect for disposable client work and useMemoized for keyed resource identity.

use