使用带参数的重选选择器

Question

如何将其他参数传递给组合选择器？我在尝试着

•获取数据

•过滤数据

•通过myValue向我的数据集/组数据添加自定义值

export const allData = state => state.dataTable
export const filterText = state => state.filter.get('text')

export const selectAllData = createSelector(
  allData,
  (data) => data
)

export const selectAllDataFiltered = createSelector(
  [ selectAllData, filterText ],
  (data, text) => {
    return data.filter(item => {
      return item.name === text
    })
  }
)

export const selectWithValue = createSelector(
  [ selectAllDataFiltered ],
  (data, myValue) => {
    console.log(myValue)
    return data
  }
)

let data = selectWithValue(state, 'myValue')

console.log(myValue) 回报 undefined

Answer 1

从选择器返回一个函数怎么样？getFilteredToDos是一个例子

// redux part
const state = {
  todos: [
    { state: 'done',     text: 'foo' },
    { state: 'time out', text: 'bar' },
  ],
};

// selector for todos
const getToDos = createSelector(
  getState,
  (state) => state.todos,
);

// selector for filtered todos
const getFilteredToDos = createSelector(
  getToDos,
  (todos) => (todoState) => todos.filter((toDo) => toDo.state === todoState);
);

// and in component
const mapStateToProps = (state, ownProps) => ({
  ...ownProps,
  doneToDos: getFilteredToDos()('done')
});

Answer 2

更新时间：2021 年 3 月 36 日

Reselector的解决方案： 查看详细信息

// selector.js
import { createSelector } from 'reselect'
import memoize from 'lodash.memoize'

const expensiveSelector = createSelector(
  state => state.items,
  items => memoize(
    minValue => items.filter(item => item.value > minValue)
  )
)

// App.js
const expensiveFilter = expensiveSelector(state)
// Another way if you're using redux:
// const expensiveFilter = useSelector(expensiveSelector)

const slightlyExpensive = expensiveFilter(100)
const veryExpensive = expensiveFilter(1000000)

老的：

这是我的方法。创建一个带参数和返回函数的函数reselect。

export const selectWithValue = (CUSTOM_PARAMETER) => createSelector(
  selectAllDataFiltered,
  (data) => {
    console.log(CUSTOM_PARAMETER)
    return data[CUSTOM_PARAMETER]
  }
)

const data = selectWithValue('myValue')(myState);

Answer 3

您的问题的答案在FAQ中有详细说明：https：//github.com/reactjs/reselect#q-how-do-i-create-a-selector-that-takes-an-argument

简而言之，重新选择不支持传递给选择器的任意参数。推荐的方法是，将相同的数据存储在Redux状态中，而不是传递参数。

Answer 4

这是最新的 useSelector钩子的。

重要的是从输入选择器中获取参数。输入选择器的第二个参数是我们获取它的方式。

这是选择器的外观，

const selectNumOfTodosWithIsDoneValue = createSelector(
  (state) => state.todos,
  (_, isDone) => isDone, // this is the parameter we need
  (todos, isDone) => todos.filter((todo) => todo.isDone === isDone).length
)

这是我们如何使用useSelector钩子提取值，

export const TodoCounterForIsDoneValue = ({ isDone }) => {
  const NumOfTodosWithIsDoneValue = useSelector((state) =>
    selectNumOfTodosWithIsDoneValue(state, isDone)
  )

  return <div>{NumOfTodosWithIsDoneValue}</div>
}

另外，保留第二个参数 ( isDone) 作为原始值（字符串、数字等）。因为，reselect 仅在输入选择器值更改时运行输出选择器。这种变化是通过浅比较来检查的，对于对象和数组等参考值，这种比较总是错误的。

参考：

1. https://react-redux.js.org/next/api/hooks#using-memoizing-selectors
2. https://flufd.github.io/reselect-with-multiple-parameters/
3. https://blog.isquaredsoftware.com/2017/12/idiomatic-redux-using-reselect-selectors/