Question

我查看了多个试图解决此问题的来源，但找不到任何答案。我有一个功能组件 <Dashboard />，它将显示来自 API 的一些信息。

我希望组件首先进入 useEffect，执行 getData 函数，然后在屏幕上显示 {devices}。但是，发生的情况是存储状态已更新，但组件未更新。 {devices} 变量始终未定义。我想我不明白如何使用 useSelector 从 reducers/all/dashboard.js 访问我的状态变量。

仪表板/index.js

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

import api from "../../services/api";

import * as DashboardActions from "../../store/actions/dashboard";

const Dashboard = (props) => {
  const dispatch = useDispatch();
  const devices = useSelector(state => state.device)

  useEffect(() => {
    async function getData() {
      const pathname = "/dashboard";

      await api
        .get(pathname)
        .then((res) => {
          dispatch(DashboardActions.setData(res.data));
        })
        .catch((res) => {
          console.log(res.response.data);
        });
    }
    getData();
    console.log("devices ue ", devices);

  }, [dispatch]);

  return (
    <div>
      <h1>Dashboard</h1>
      <span>{devices}</span>
    </div>
  );
};

export default Dashboard;

reducers/all/dashboard.js

const INITIAL_STATE = {
  devices: [],
};

function dashboard(state = INITIAL_STATE, action) {
  console.log("Action ", action)
  if ("DASHBOARD_SET_DATA" === action.type) {
    const data = action.data;
    console.log("Data: ", data.devices)
    state = { ...state, devices: data.devices };

    console.log("State ", state)
  }

  return state;
}

export default dashboard;

actions/dashboard.js

export function setData(data) {
  return {
    type: "DASHBOARD_SET_DATA",
    data,
  };
}

非常感谢您的帮助。

提前致谢！

Answer 1

react-redux useSelector 钩子正在从您的 redux 存储状态对象中选择状态。

如果您的 dashboard 减速器组合到您的根减速器中，则类似于

const rootReducer = combineReducers({
  ... other reducers
  dashboard,
  ... other reducers
});

然后应该从 state.dashboard.devices 访问设备状态值。

组件的更新：

const devices = useSelector(state => state.dashboard.devices)

如何使用 useSelector 在功能组件中访问 redux 的 store 状态变量？

1 个答案: