react-redux - 错误 : An error occured while selecting the store state: Cannot read property 'counter' of undefined

Question

App.js

import React from "react";

import { useSelector, useDispatch } from "react-redux";

export const App = () => {
  const x = useSelector(state => state.reduserDD.counter);
  const dispatch = useDispatch();

  console.log(x);

  return (
    <div>
      <div onClick={() => dispatch({ type: "increment" })}>+</div>
      <div onClick={() => dispatch({ type: "decrement" })}>-</div>
      <div>{x}</div>
    </div>
  );
};

index.js

import React from "react";
import ReactDOM from "react-dom";
import { Provider } from "react-redux";
import { createStore } from "redux";

import { App } from "./App";
import { reduserDD } from "./reduser";

const store = createStore(reduserDD);

ReactDOM.render(
  <Provider store={store}>
    <App />
  </Provider>,
  document.getElementById("root")
);

reducer

const initialState = {
  counter: 0
};

export const reduserDD = (state = initialState, { type }) => {
  switch (type) {
    case "increment":
      return { counter: state.counter + 1 };
    case "decrement":
      return { counter: state.counter - 1 };
    default:
      return state;
  }
};

我使用 Redux Hook 并收到此错误。

Error: An error occured while selecting the store state: Cannot read >property 'counter' of undefined.

问题是什么，我该如何解决？

Answer 1

您将 reduserDD 直接传递给 createStore。所以 state.reduserDD 不存在。 state 是您的 reduserDD。

你只需要获取state.counter而不是state.reduserDD.counter

const x = useSelector(state => state.counter);