Javascript 返回未定义的响应值
我试图在上下文中映射数据,并呈现出一个汽车列表。但我总是遇到一些错误。我想能够选择其中一辆车,并让它导航到另一个页面,显示更多的汽车细节我。当前错误为(TypeError:value.state.car未定义)。任何帮助都会很好!现行代码Javascript 返回未定义的响应值,javascript,reactjs,react-context,Javascript,Reactjs,React Context,我试图在上下文中映射数据,并呈现出一个汽车列表。但我总是遇到一些错误。我想能够选择其中一辆车,并让它导航到另一个页面,显示更多的汽车细节我。当前错误为(TypeError:value.state.car未定义)。任何帮助都会很好!现行代码 Context.js import React, {Component } from 'react'; import { carInventory } from './data'; export const MyContext = React.createC
Context.js
import React, {Component } from 'react';
import { carInventory } from './data';
export const MyContext = React.createContext();
export class MyProvider extends Component {
state = {
cars: []
};
componentDidMount() {
this.setCars();
}
setCars = () => {
let tempProducts = [];
carInventory.forEach(item =>{
const singleItem = {...item};
tempProducts = [...tempProducts,singleItem];
})
this.setState(()=>{
return {cars:tempProducts}
})
}
getItem = (id) => {
const car = this.state.cars.find(item => item.id === id);
return car;
}
handleDetail = (id) =>{
const car = this.getItem(id);
this.setState(()=>{
return {detailProduct:car}
})
}
render() {
return (
<MyContext.Provider value={{
state: this.state,
handleDetail: this.handleDetail}}>
{this.props.children}
</MyContext.Provider>
)
}
}
VehicleList.js
import React, { Component } from "react"
import './App.css';
import Vehicles from "./Vehicles"
import { MyProvider, MyContext } from "./Context";
export default class VehicleList extends Component {
render() {
return (
<div className="vehicles">
<div className="showcase">
<MyContext.Consumer>
{(value) => (
<React.Fragment>
{value.state.car.map(car => {
return (
<Vehicles key={car.id} car=
{car} />
);
})}
</React.Fragment>
)}
</MyContext.Consumer>
</div>
</div>
)
}
}
import React, { Component } from 'react';
import './App.css';
import { MyProvider, MyContext } from "./Context";
import { Link } from 'react-router-dom';
class Vehicles extends Component {
render() {
const { make, model, id, info, img } = this.props.cars
return (
<div className="col-9 mx-auto col-md-6 col-lg-3 my-3">
<div className="card">
<MyContext.Consumer>
{(value) => (<div className="img-container p-5"
onClick={() =>{
value.handleDetail(id)
}}>
<Link to="/VehicleOverview">
<img src={img} alt="product" className="card-img-top"/>
</Link>
</div>)}
</MyContext.Consumer>
</div>
</div>
)
}
}
export default Vehicles;
Context.js
从“React”导入React,{Component};
从“./data”导入{carInventory};
export const MyContext=React.createContext();
导出类MyProvider扩展组件{
状态={
汽车:[]
};
componentDidMount(){
这个。setCars();
}
setCars=()=>{
设tempProducts=[];
carInventory.forEach(项=>{
常量singleItem={…item};
tempProducts=[…tempProducts,singleItem];
})
此.setState(()=>{
返回{cars:tempProducts}
})
}
getItem=(id)=>{
const car=this.state.cars.find(item=>item.id==id);
返回车;
}
handleDetail=(id)=>{
const car=this.getItem(id);
此.setState(()=>{
返回{detailProduct:car}
})
}
render(){
返回(
{this.props.children}
)
}
}
VehicleList.js
从“React”导入React,{Component}
导入“/App.css”;
从“/车辆”进口车辆
从“/Context”导入{MyProvider,MyContext};
导出默认类车辆列表扩展组件{
render(){
返回(
{(值)=>(
{value.state.car.map(car=>{
返回(
);
})}
)}
)
}
}
从“React”导入React,{Component};
导入“/App.css”;
从“/Context”导入{MyProvider,MyContext};
从'react router dom'导入{Link};
类车辆扩展组件{
render(){
const{make,model,id,info,img}=this.props.cars
返回(
{(值)=>({
值。handleDetail(id)
}}>
)}
)
}
}
出口默认车辆;
在这种情况下,静态类型检查器可以真正为您节省一些白发
您的上下文确实没有任何属性car
但是,它确实有一个属性cars
因此,您应该映射汽车,即value.state.cars.map(car=>…)
:)您的状态变量是
car
还是cars
?啊,谢谢!但是现在我似乎得到了另一个类型错误,因为这个$props$cars在我的车辆组件中没有定义。好吧,再次看看你传递到车辆组件中的道具
所以它应该是const{make,model,id,info,img}=this.props.car
。