useCallback

일반적인 함수처럼 사용됩니다. 아래와 같이 메서드를 인자로 받아 사용합니다.

useCallback(T callback, [List<Object?> keys = const <Object>[]])

예시

a와 b의 값을 각각 증가시켜 합을 반환하는 useCallback을 사용한 sumATOB 예시입니다.

class UsecallbackEx extends HookWidget {
  const UsecallbackEx({super.key});

  @override
  Widget build(BuildContext context) {
    var a = useState(0);
    var b = useState(0);

    var sumATOB = useCallback((a, b) {
      return a + b;
    }, [a, b]);

    return Scaffold(
      appBar: AppBar(),
      body: SafeArea(
          child: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(sumATOB(a.value, b.value).toString()),
            const SizedBox(height: 10),
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              crossAxisAlignment: CrossAxisAlignment.center,
              children: [
                ElevatedButton(
                    onPressed: () {
                      a.value++;
                    },
                    child: const Text('a')),
                ElevatedButton(
                    onPressed: () {
                      b.value++;
                    },
                    child: const Text('b')),
              ],
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                Text(a.value.toString()),
                const SizedBox(width: 60),
                Text(b.value.toString()),
              ],
            )
          ],
        ),
      )),
    );
  }
}