javascript - 使用带参数的重新选择选择器

Question

如何将附加参数传递给组合选择器？我在尝试着

• 获取数据

• 过滤数据

• 将自定义值添加到我的数据集/按 myValue 分组数据

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)返回undefined

score 13 · Accepted Answer

您的问题的答案在此处的常见问题解答中进行了详细说明：https ://github.com/reactjs/reselect#q-how-do-i-create-a-selector-that-takes-an-argument

简而言之，reselect 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。

score 12 · Accepted Answer

更新日期：2022 年 2 月 16 日

Reselector 4.1 的新解决方案： 查看详细信息

// selector.js
const selectItemsByCategory = createSelector(
  [
    // Usual first input - extract value from `state`
    state => state.items,
    // Take the second arg, `category`, and forward to the output selector
    (state, category) => category
  ],
  // Output selector gets (`items, category)` as args
  (items, category) => items.filter(item => item.category === category)
);

// App.js
const items = selectItemsByCategory(state, 'javascript');
// Another way if you're using redux:
const items = useSelector(state => selectItemsByCategory(state, 'javascript'));

更新日期：2021 年 3 月 6 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。创建一个带有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);

score 9 · Accepted Answer

这是一个最新的useSelector钩子。

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如何获取它。

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
)

下面是我们如何使用useSelector钩子提取值，

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

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

此外，尽可能将第二个参数 ( isDone) 保留为原始值（字符串、数字等）。因为，reselect，只有在输入选择器值改变时才运行输出选择器。这种变化是通过浅比较来检查的，对于像 Object 和 Array 这样的参考值，这总是错误的。

参考：

score 8 · Accepted Answer

what about returning a function from selector? getFilteredToDos is an example for that

// 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')
});

score 1 · Accepted Answer

这在Accessing React Props in Selectors下的重新选择文档中有所介绍：

import { createSelector } from 'reselect'

const getVisibilityFilter = (state, props) =>
  state.todoLists[props.listId].visibilityFilter

const getTodos = (state, props) =>
  state.todoLists[props.listId].todos

const makeGetVisibleTodos = () => {
  return createSelector(
    [ getVisibilityFilter, getTodos ],
    (visibilityFilter, todos) => {
      switch (visibilityFilter) {
        case 'SHOW_COMPLETED':
          return todos.filter(todo => todo.completed)
        case 'SHOW_ACTIVE':
          return todos.filter(todo => !todo.completed)
        default:
          return todos
      }
    }
  )
}

export default makeGetVisibleTodos

const makeMapStateToProps = () => {
  const getVisibleTodos = makeGetVisibleTodos()
  const mapStateToProps = (state, props) => {
    return {
      todos: getVisibleTodos(state, props)
    }
  }
  return mapStateToProps
}

在这种情况下，传递给选择器的 props 是传递给 React 组件的 props，但 props 可以来自任何地方：

const getVisibleTodos = makeGetVisibleTodos()

const todos = getVisibleTodos(state, {listId: 55})

查看以下类型以进行重新选择：

export type ParametricSelector<S, P, R> = (state: S, props: P, ...args: any[]) => R;
export function createSelector<S, P, R1, T>(
  selectors: [ParametricSelector<S, P, R1>],
  combiner: (res: R1) => T,
): OutputParametricSelector<S, P, T, (res: R1) => T>;

我们可以看到对 props 的类型（P类型 in ParametricSelect）没有限制，所以它不需要是object.

score -1 · Accepted Answer

另外的选择：

const parameterizedSelector = (state, someParam) => createSelector(
  [otherSelector],
  (otherSelectorResult) => someParam + otherSelectorResult
);

然后像这样使用

const mapStateToProps = state => ({
  parameterizedSelectorResult: parameterizedSelector(state, 'hello')
});

虽然我不确定在这种情况下的记忆/性能，但它确实有效。

javascript - 使用带参数的重新选择选择器

6 回答 6

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