我正在设置一个带有Rails后端的React应用程序。我得到的错误“对象是无效的React子(发现:对象与键{id，名称，信息，created_at, updated_at})。如果你想呈现一组子元素，请使用数组。”
这是我的数据:
[
{
"id": 1,
"name": "Home Page",
"info": "This little bit of info is being loaded from a Rails
API.",
"created_at": "2018-09-18T16:39:22.184Z",
"updated_at": "2018-09-18T16:39:22.184Z"
}
]
我的代码如下:
import React from 'react';
class Home extends React.Component {
constructor(props) {
super(props);
this.state = {
error: null,
isLoaded: false,
homes: []
};
}
componentDidMount() {
fetch('http://localhost:3000/api/homes')
.then(res => res.json())
.then(
(result) => {
this.setState({
isLoaded: true,
homes: result
});
},
// error handler
(error) => {
this.setState({
isLoaded: true,
error
});
}
)
}
render() {
const { error, isLoaded, homes } = this.state;
if (error) {
return (
<div className="col">
Error: {error.message}
</div>
);
} else if (!isLoaded) {
return (
<div className="col">
Loading...
</div>
);
} else {
return (
<div className="col">
<h1>Mi Casa</h1>
<p>This is my house y'all!</p>
<p>Stuff: {homes}</p>
</div>
);
}
}
}
export default Home;
我做错了什么?
这个问题是因为您试图显示整个对象，而不是对象内部的键。
例如:数据是
[
{
"status": "success",
"count": 20511
},
{
"status": "failure",
"count": 1776
}
]
现在，在如下所示的组件中，这将工作。
import React, { Component } from 'react';
export default class Display extends Component {
render() {
const { data } = this.props;
return (
<>
{
data.map((value,key)=>
<div>{value.status}</div>
<div>{value.count}</div>
)
}
</>
)
}
}
我今天得到了同样的错误，但与这个问题中发布的场景相比，情况有所不同。希望下面的解决方案能帮助到一些人。
下面的渲染函数足以理解我的场景和解决方案:
render() {
let orderDetails = null;
if(this.props.loading){
orderDetails = <Spinner />;
}
if(this.props.orders.length == 0){
orderDetails = null;
}
orderDetails = (
<div>
{
this.props.orders &&
this.props.orders.length > 0 &&
this.props.orders.map(order => (
<Order
key={order.id}
ingredient={order.ingredients}
price={order.price} />
))
}
</div>
);
return orderDetails;
}
在上面的代码片段中:如果return orderDetails作为return {orderDetails}发送，那么尽管'orderDetails'的值(值为<Spinner/>或null或与<Order />组件相关的JSX)，这个问题中发布的错误仍然会弹出。
错误描述:React -dom.development.js:57未捕获的不变性违规:对象作为React子对象无效(发现:带有键{orderDetails}的对象)。如果要呈现子元素的集合，请使用数组。
我们不能从render()方法内部的返回调用中返回JavaScript对象。原因是React期望一些JSX, false, null, undefined, true在UI中呈现，而不是一些JavaScript对象，当我使用返回{orderDetails}时，我试图呈现，因此得到如上所述的错误。
有效:
<div />
<div></div>
<div>{false}</div>
<div>{null}</div>
<div>{undefined}</div>
<div>{true}</div>
无效:
<div>{orderDetails}</div> // This is WRONG, orderDetails is an object and NOT a valid return value that React expects.
Edit: I also got this error on my company's test server used by QA's for their testing. I pointed my local code to that test server and tested the scenario in which this error was reported by QA team and found NO ERROR in my local machine. I got surprised. I re-checked multiple number of times, re-checked the scenario with QA team and I was doing right but still I was not able to replicate the issue. I consulted my fellow devs but still were not able to figure out the root cause. So keeping with the information in the error message I started scanning all the code I had deployed in my last deployment commit ( to be more specific last 4-5 commits because I suspected it could be there from last few deployments but was caught in the current deployment), especially all the components I had developed and found that there was a component - inside which there was no specified condition being met so it was returning NOTHING from it. So see below sample pseudo code. I hope it helps.
render () {
return (
{this.props.condition1 && (
return some jsx 1
)}
{this.props.condition1 && (
return some jsx 2
)})
}
如果你在上面的伪代码中看到，如果条件1和条件2不满足，那么这个组件将从它呈现NOTHING，理想情况下，react组件必须从它返回一些JSX, false, null, undefined, true。
我有一个类似的错误，而我正在创建一个自定义模式。
const CustomModal = (visible, modalText, modalHeader) => {}
问题是我忘记了功能组件只能有一个道具传递给他们，根据REACT文档:
这个函数是一个有效的React组件，因为它只接受一个
“props”(代表属性)对象参数与数据和
返回一个React元素。我们称这种组件为“功能组件”
因为它们是JavaScript函数。反应文档
Therefore when we want to pass several variables we need to wrap them into an object or an Array and pass the pointer to that array or object. And destructure it on the component side before invoking the component. Alternatively we can use curly braces to indicate that we are sending an object with identical property names and variables that contain the value of those properties, like in the example here. And then define the function also to destructure upon arrival of the properties contained in the object.
const CustomModal = ({visible, modalText, modalHeader}) => {}
如果你有多个值要传递给组件，你应该传递一个对象，在它的属性/变量周围用花括号括起来(假设它们有相同的名字)。
