如何在React中访问孩子的状态？ （反应钩）

Question

使用react-hooks来访问孩子的状态的最佳解决方案是什么？

我尝试了各种方法。在我最终得到的答案下面。

表格（父母）

export const Form: FunctionComponent<IProps> = ({ onFinish, initState }) => {
  const formInputsStateRef = useRef({})

  const handleFinish = () => {
    const params = formInputsStateRef.current
    console.log(params)
    onFinish(params)
  }

  return (
    <div>
      <Inputs initState={initState} stateRef={formInputsStateRef}  />
      <S.Button onClick={handleFinish}>
        Finish
      </S.Button>
    </div>
  )
}

输入（子项）

export const Inputs: FunctionComponent<IProps> = ({ initState, stateRef }) => {
  const [pool, setPool] = useState(initState.pool)
  const [solarPanel, setSolarPanel] = useState(initState.solarPanel)

  useEffect(() => {
    stateRef.current = { pool, solarPanel }
  })

  const handlePoolInput = () => {
    setPool('new pool')
  }

  const handleSolarPanelInput = () => {
    setSolarPanel('new solar panel')
  }

  return (
    <div>
      <h2>{pool}</h2>
      <S.Button onClick={handlePoolInput}>Change pool</S.Button>
      <h2>{solarPanel}</h2>
      <S.Button onClick={handleSolarPanelInput}>Change solar panel</S.Button>
      <h2>-----</h2>
    </div>
  )
}

它以这种方式工作，但是我不喜欢它在每个渲染器上创建一个对象的事实。

---

Inputs（子级）

useEffect(() => {
    stateRef.current = { pool, solarPanel }
})

Answer 1

您可以将pool和solarPanel作为第二个参数传递给useEffect，以便将状态更新为仅在这些值更改时进行引用

export const Inputs: FunctionComponent<IProps> = ({ initState, stateRef }) => {
  const [pool, setPool] = useState(initState.pool)
  const [solarPanel, setSolarPanel] = useState(initState.solarPanel)

  useEffect(() => {
    stateRef.current = { pool, solarPanel }
  }, [pool, solarPanel])

  const handlePoolInput = () => {
    setPool('new pool')
  }

  const handleSolarPanelInput = () => {
    setSolarPanel('new solar panel')
  }

  return (
    <div>
      <h2>{pool}</h2>
      <S.Button onClick={handlePoolInput}>Change pool</S.Button>
      <h2>{solarPanel}</h2>
      <S.Button onClick={handleSolarPanelInput}>Change solar panel</S.Button>
      <h2>-----</h2>
    </div>
  )
}

但是，使用ref可以更有效地控制子值，您可以使用useImperativeHandle钩子。

孩子

const InputsChild: FunctionComponent<IProps> = ({ initState, ref }) => {
  const [pool, setPool] = useState(initState.pool)
  const [solarPanel, setSolarPanel] = useState(initState.solarPanel)

  useImperativeHandle(ref, () => ({
    pool,
    solarPanel
  }), [pool, solarPanel])

  const handlePoolInput = () => {
    setPool('new pool')
  }

  const handleSolarPanelInput = () => {
    setSolarPanel('new solar panel')
  }

  return (
    <div>
      <h2>{pool}</h2>
      <S.Button onClick={handlePoolInput}>Change pool</S.Button>
      <h2>{solarPanel}</h2>
      <S.Button onClick={handleSolarPanelInput}>Change solar panel</S.Button>
      <h2>-----</h2>
    </div>
  )
}

export const Inputs = forwarRef(InputsChild);

父母

export const Form: FunctionComponent<IProps> = ({ onFinish, initState }) => {
  const formInputsStateRef = useRef({})

  const handleFinish = () => {
    const params = formInputsStateRef.current
    console.log(params)
    onFinish(params)
  }

  return (
    <div>
      <Inputs initState={initState} ref={formInputsStateRef}  />
      <S.Button onClick={handleFinish}>
        Finish
      </S.Button>
    </div>
  )
}