Redux:调用 action-creator 返回“无法读取未定义的属性‘道具’" [英] Redux: Call to action-creator returns 'Cannot read property 'props' of undefined'
问题描述
我能够获取给定城市的天气,但之后不知道如何删除它.作为 Redux 的新手,我试图弄清楚我在这个难题中遗漏了哪些部分.
I'm able to fetch the weather by a given city but can't figure how to delete it afterwards. Being still new to Redux I'm trying to figure which pieces am I missing on this puzzle.
我将保留 FETCH_WEATHER 代码仅用于上下文建议.我的问题与 DELETE_CITY 实现有关.
I'm leaving the FETCH_WEATHER code in just for context proposes. My issues is with the DELETE_CITY implementation.
错误:
步骤:
在每一行中添加一个调用动作创建者的按钮.
动作创建者采用城市"的名称并返回一个类型为DELETE_CITY"的动作.
Action creator takes the name of the 'city' and return an action of type 'DELETE_CITY'.
Reducer,监视该类型并遍历城市数组并删除具有给定城市名称的对象.
Reducer, watches for that type and iterates through the array of cities and deletes the object with the given city name.
动作创建者
import axios from 'axios';
const API_KEY = '1111111111111111111111';
const ROOT_URL = `http://api.openweathermap.org/data/2.5/forecast?appid=${API_KEY}`;
export const FETCH_WEATHER = 'FETCH_WEATHER';
export const DELETE_CITY = 'DELETE_CITY';
//fetch cities
export function fetchWeather(city){
const url = `${ROOT_URL}&q=${city},&units=imperial`;
const request = axios.get(url);
console.log('Request:', request);
return {
type: FETCH_WEATHER,
payload: request
}
}
//Delete Cities
export function deleteCity(city) {
return {
type: DELETE_CITY,
payload: city
}
}
减速器:index.js
import { combineReducers } from 'redux';
import WeatherReducer from './reducer_weather';
const rootReducer = combineReducers({
weather: WeatherReducer
});
export default rootReducer;
weather_reducer.js
DELETE_CITY 的情况是否准确实施?
import { FETCH_WEATHER } from '../actions/index';
import { DELETE_CITY } from '../actions/index';
export default function (state = [], action) {
console.log('Action received', action);
//only fetch weather data type
switch (action.type) {
case FETCH_WEATHER:
//concat to prevent state mutation
return state.concat([action.payload.data]);
case DELETE_CITY:
return state
.slice(0, action.payload.data)
.concat([action.payload.data].slice([action.payload.data] + 1));
}
return state;
}
- 在每一行中添加一个调用操作创建者的按钮.
Ps:mapStateToProps 和 mapDispatchToProps 是否正确?
weather_container.js
import React, { Component } from 'react';
import { connect } from 'react-redux';
import Chart from '../components/chart';
import GoogleMap from '../components/google_map';
import { bindActionCreators } from 'redux';
import { deleteCity } from '../actions/index';
class WeatherList extends Component {
renderWeather(cityData) {
const name = cityData.city.name;
return (
<tr key={name}>
<td><button onClick={() => this.props.deleteCity(cityData)} className="btn btn-danger">x</button></td>
</tr>
)
}
render() {
return (
<table>
<thead>
<tr>
<th>City</th>
</tr>
</thead>
<tbody>
{this.props.weather.map(this.renderWeather)}
</tbody>
</table>
)
}
}
function mapStateToProps(state) {
return {
weather: state.weather
}
}
function mapDispatchToProps(dispatch, weather) {
return bindActionCreators({deleteCity},{weather}, dispatch)
}
export default connect(mapStateToProps, mapDispatchToProps)(WeatherList);
我需要将动作创建者绑定到 onClick 事件.我尝试了两种方法:粗箭头函数和/或将方法绑定到构造函数()内".
I need to bind the action creator to the onClick event. I tried both methods: fat arrow functions and/or 'binding the method inside of a constructor()'.
它们都返回未定义的 props.
They both return with props undefined.
推荐答案
尝试替换:
{this.props.weather.map(this.renderWeather)}
与
{this.props.weather.map(this.renderWeather, this)}
map<的第二个参数/code>
是 thisArg
- 执行 callback
时用作 this
的值.
The second argument of map
is the thisArg
- value to use as this
when executing callback
.
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