Question

我当前正在尝试创建一个useRadioList()挂钩，以跟踪给定组件中所有子项上的isExpanded道具（当一个子项切换为isExpanded时，另一个子项-toggle）

我这样做的方式一直是：

通过创建与子项相同长度的假值列表来设置初始状态
将此状态映射到每个孩子的isExpanded道具
声明并返回用于操纵初始列表状态的切换功能

// useRadioList.jsx
import React, { Children, isValidElement, cloneElement, useState, useEffect } from "react"

export default (children, allowMultiple = true) => {


// 1) Setup initial list 

  const [radioList, setRadioList] = useState(Array(children.length).fill(false))

// 2) Map radioList values to component children on initial render, and do so again if radioList changes

  useEffect(() => {

    Children.map(children, (child, idx) => {
      if (!isValidElement(child)) {return}

      return cloneElement(child, {isExpanded: radioList[idx]})
    })
  }, [radioList])



// 3) Declare "toggle()" to modify the list that keeps track of what indexes are active

  const toggle = (targetIndex) => {

    let newList = radioList.map((item, idx) => {
      if (allowMultiple) {
        return targetIndex == idx ? !item : item
      } else {
        return targetIndex == idx ? !item : false
      }
    })
    setRadioList(newList)
  }

  return toggle
}

// expected:  const toggle = useRadioList(children)

当我调用切换按钮时，出现以下错误：

警告：通过useState（）和useReducer（）挂钩进行状态更新不支持第二个回调参数。产生副作用渲染后，使用useEffect（）在组件主体中声明它。

编辑：

setRadioList(...newList) ----> setRadioList(newList)

不再出现callback错误，现在看来我无法有效地将状态映射到子级，因为isExpanded道具在初始渲染后并未显示在每个子级中。

Answer 1

setRadioList必须这样使用：

setRadioList(newList)

Spread运算符拆分数组并将每个值作为单独的参数发送，例如setRadioList(...[1,2,3])会变成setRadioList(1, 2, 3)，这当然是不正确的。

请参见https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax#Spread_in_array_literals

Answer 2

操纵子代的代码不会突变原始子代，而是创建新子代，因此以下代码无效：

   Children.map(children, (child, idx) => {
      if (!isValidElement(child)) {return}

      return cloneElement(child, {isExpanded: radioList[idx]})
    });

尝试返回新的孩子，像这样：

export default (originalChildren, allowMultiple = true) => {


  // 1) Setup initial list 

    const [radioList, setRadioList] = useState(Array(originalChildren.length).fill(false))
    const [children, setChildren] = useState(originalChildren);

  // 2) Map radioList values to component children on initial render, and do so again if radioList changes

    useEffect(() => {
      setChildren(children => Children.map(children, (child, idx) => {
        if (!isValidElement(child)) {return}

        return cloneElement(child, {isExpanded: radioList[idx]})
      }));

    }, [radioList])



  // 3) Declare "toggle()" to modify the list that keeps track of what indexes are active

    const toggle = useCallback((targetIndex) => {
      setRadioList(radioList => radioList.map((item, idx) => {
        if (allowMultiple) {
          return targetIndex == idx ? !item : item
        } else {
          return targetIndex == idx ? !item : false
        }
      }))
    }, [allowMultiple])

    return { toggle, children }
  }

  // use like this:  const { toggle, children } = useRadioList(children)

在自定义React挂钩中无法返回函数

2 个答案: