Redux

Question

如果我说错了，请纠正我。

- 代表

declare export function connect<-P, -OP, -SP, -DP, S, D>(
  // ...
)

道具. 只是该组件最终应该得到的所有道具。

- 代表

• P自己的道具. 应该传递给连接组件的道具(即不从状态中派生)。 - 代表

• OPStateProps. 由状态衍生出来的道具，它 必须返回。

• SP - 代表 调度道具. 由调度派生出来的道具，这些道具： mapStateToProps 必须返回。

• DP - 代表 国家. 要通过的状态类型 mapDispatchToProps.

• S - 代表 调度. 要传递的调度类型 mapStateToProps.

• D如果上面的说法都是正确的，那么在我看来一切都很清楚，很合理。所以，当我试图传递这些属性的时候。我从flow中得到如下的输出，为什么？mapDispatchToProps先谢谢你。

/* @flow */

import React from 'react';
import { connect } from 'react-redux';
import * as ActionCreators from './actionCreators';
import type { Todo } from './types';
import type { State } from './reducers';

type OwnProps = {||};

type StateProps = {|
  +todos: Array<Todo>;
|};

type DispatchProps = $ReadOnly<typeof ActionCreators>

type Props = {|
  ...OwnProps;
  ...StateProps;
  ...DispatchProps;
|};

export const TodoList = (props: Props) => (
  <div>
    // ...
  </div>
);

const mapStateToProps = (state: State) => ({
  todos: state.visibleTodos,
});

const mapDispatchToProps = ActionCreators; // redux will automatically call `bindActionCreators`

export default connect<Props, OwnProps, StateProps, DispatchProps, State, _>(
  mapStateToProps,
  mapDispatchToProps
)(TodoList);

redux connect函数的flow声明如下：声明导出函数connect( / ... )它取自：https:/github.comflow-typedflow-typed...。

Cannot call connect because:
 - Either property todos is missing in object type [1] but exists in StateProps [2] in type argument SP.
 - Or property addTodo is missing in object type [3] but exists in DispatchProps [4] in type argument DP.
 - Or property todos is missing in object type [5] but exists in StateProps [2] in type argument SP.
 - Or property todos is missing in object type [6] but exists in StateProps [2] in type argument SP.

        src/components/TodoList/index.jsx
         72|
         73| const mapDispatchToProps = ActionCreators;
         74|
 [2][4]  75| export default connect<Props, OwnProps, StateProps, DispatchProps, State, _>(
         76|   mapStateToProps,
         77|   mapDispatchToProps,
         78| )(TodoList);

        flow-typed/npm/react-redux_v7.x.x.js
    [1] 148|   declare export function connect<-P, -OP, -SP: {||}, -DP: {||}, S, D>(
           :
    [3] 156|   declare export function connect<-P, -OP, -SP, -DP: {||}, S, D>(
           :
    [5] 166|   declare export function connect<-P, -OP, -SP: {||}, -DP, S, D>(
           :
    [6] 176|   declare export function connect<-P, -OP, -SP: {||}, -DP, S, D>(

Found 1 error

原来这就是类型推理的flow bug。我解决了这个问题，明确地添加了

返回类型

Answer 1

StateProps