我正在使用 React、React-redux、Redux、Express 和 Sequelize 为学校项目构建一个应用程序。
在我的其他 View 中,我取回了数据,以相应地插入和更新我的 View ,但在这种情况下,我得到未定义。
我刚刚从 redux 切换到react-redux,所以我提前道歉!
这是我的控制台的屏幕截图:
这是我的 SingleCountry reducer ,还有我的 Action 创建者和 thunk...
'use strict';
import axios from 'axios';
// ACTION TYPES
const GET_COUNTRY = 'GET_COUNTRY';
// ACTION CREATORS
export function getCountry(oneCountry) {
const action = {
type: GET_COUNTRY,
oneCountry,
};
return action;
}
//THUNK CREATORS
export function fetchCountry(countryId) {
return function thunk(dispatch) {
return axios
.get('/api/countries/' + `${countryId}`)
.then(res => res.data)
.then(country => {
const action = getCountry(country);
dispatch(action);
});
};
}
// REDUCER
const reducer = function(state = [], action) {
switch (action.type) {
case GET_COUNTRY:
return action.oneCountry;
default:
return state;
}
};
export default reducer;
这是国家/地区的 reducer :
'use strict';
import axios from 'axios';
// ACTION TYPES
const GET_COUNTRIES = 'GET_COUNTRIES';
// ACTION CREATORS
export function getCountries(countries) {
const action = {
type: GET_COUNTRIES,
countries,
};
return action;
}
//THUNK CREATORS
export function fetchCountries() {
return function thunk(dispatch) {
return axios
.get('/api/countries')
.then(res => res.data)
.then(countries => dispatch(getCountries(countries)))
.catch(console.error);
};
}
// REDUCER
const reducer = function(state = [], action) {
switch (action.type) {
case GET_COUNTRIES:
return action.countries;
// return { ...state, countries: action.countries };
default:
return state;
}
};
export default reducer;
这是 TopFiveCountries 的 reducer :
'use strict';
import axios from 'axios';
// ACTION TYPES
const GET_TOP_COUNTRIES_BY_GFI = 'GET_TOP_COUNTRIES_BY_GFI';
// ACTION CREATORS
export function getTopFiveCountriesByGFI(topFiveCountries) {
const action = {
type: GET_TOP_COUNTRIES_BY_GFI,
topFiveCountries,
};
return action;
}
//THUNK CREATORS
export function fetchTopFiveCountriesByGFI() {
return function thunk(dispatch) {
return axios
.get('/api/countries/top-five-countries')
.then(res => res.data)
.then(countries => {
const action = getTopFiveCountriesByGFI(countries);
dispatch(action);
})
.catch(console.error);
};
}
// REDUCER
const reducer = function(state = [], action) {
switch (action.type) {
case GET_TOP_COUNTRIES_BY_GFI:
return action.topFiveCountries;
// return { ...state, topFiveCountries: action.topFiveCountries };
default:
return state;
}
};
export default reducer;
这是 SingleCountry 问题的 View :
import React, { Component } from 'react';
import { fetchCountry } from '../reducers/oneCountry';
import { connect } from 'react-redux';
import store from '../store';
class SingleCountry extends Component {
constructor(props) {
super(props);
}
render() {
const flagStyle = {
height: '50px',
width: '100px',
};
const oneCountry = this.props.oneCountry;
return (
<div className="row">
<div className="twelve columns">
<h2> - Single Country -</h2>
<table className="u-full-width">
<thead>
<tr>
<th>Name</th>
<th>GFI</th>
<th>Flag </th>
</tr>
</thead>
<tbody>
<tr>
<td>{oneCountry.name}</td>
<td>{oneCountry.GFI}</td>
<td>
<img style={flagStyle} src={oneCountry.flagUrl} />
</td>
</tr>
</tbody>
</table>
</div>
</div>
);
}
}
const mapDispatch = dispatch => ({
fetchCountry: countryId => {
dispatch(fetchCountry(countryId));
},
});
const mapState = state => ({
oneCountry: state.oneCountry,
});
export default connect(mapState, mapDispatch)(SingleCountry);
我的直觉告诉我它要么在我的 axios 请求中,要么在映射和调度的一些语法中。
顺便说一句,我至少得到了部分渲染(见下文)......并且没有错误。是否可以采取任何预防措施来更好地进行诊断?
任何帮助将不胜感激!
更新
这就是我的 store.js
文件的样子...
import { createStore, applyMiddleware, combineReducers } from 'redux';
import loggingMiddleware from 'redux-logger'; // https://github.com/evgenyrodionov/redux-logger
import thunkMiddleware from 'redux-thunk'; // https://github.com/gaearon/redux-thunk
import { composeWithDevTools } from 'redux-devtools-extension';
import topFiveCountriesByGFIReducer from './reducers/topFiveCountriesByGFI';
import countriesReducer from './reducers/countries';
import oneCountryReducer from './reducers/oneCountry';
const middleware = [loggingMiddleware, thunkMiddleware];
const rootReducer = combineReducers({
topFiveCountries: topFiveCountriesByGFIReducer,
countries: countriesReducer,
oneCountry: oneCountryReducer,
});
export default createStore(rootReducer, composeWithDevTools(applyMiddleware(...middleware)));
更新
我最近遇到的错误:
最佳答案
所以你没有 dispatch 你的行动。您必须分派(dispatch)该操作,并且由于它是异步的,因此最好显示某种 UI 来指示您正在从某种 API 中获取数据。这是一个精简版:
class SingleCountry extends Component {
constructor(props) {
super(props)
this.state = {
loading: true
}
}
componentDidMount() {
const countryId = this.props.match.params.id;
dispatch(this.props.fetchCountry(countryId))
.then(() => {
this.setState({
loading: false
});
});
}
render() {
const oneCountry = this.props.oneCountry;
const loading = this.state.loading;
return (
<div className="row">
<div className="twelve columns">
<h2> - Single Country -</h2>
{
!loading ?
<table className="u-full-width">
<thead>
<tr>
<th>Name</th>
<th>GFI</th>
<th>Flag </th>
</tr>
</thead>
<tbody>
<tr>
<td>{oneCountry.name}</td>
<td>{oneCountry.GFI}</td>
<td>
<img style={flagStyle} src={oneCountry.flagUrl} />
</td>
</tr>
</tbody>
</table>
:
<img src={LOADING ICON HERE} />
}
</div>
</div>
);
}
}
const mapState = (state, ownProps) => ({
oneCountry: state.oneCountry,
...ownProps
});
它的作用是最初将 loading
的状态设置为 true。然后,当组件安装时,您的请求将发送到 API。同时,当请求正在运行时,将显示一个加载图标。请求完成后,调度的 then
将执行并将 loading
的状态设置为 false。这将依次重新渲染您的组件并显示带有适当数据的表格。
此外,请注意 mapState
现在使用第二个参数 - ownProps
。问题是,当您将组件连接
到 Redux 存储时,您会丢失传递给该组件的所有 props。在这种情况下,React Router 将匹配的参数传递给 SingleCountry
,但由于 connect
而丢失。这可以通过使用 mapState
或 mapDispatch
的第二个参数来解决。第二个参数包含允许传递给连接的组件的 Prop ,您可以将它们传播到返回的对象中以在组件中访问它们。
关于javascript - 使用react-redux而不是有效负载时,操作中的值未定义,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/47745024/