reactjs - eslint:迭代器中元素缺少 "key"属性(react/jsx-key)

Question

我是 React 新手，我正在尝试输出一个包含用户信息的表。但 Eslint 一直给我以下错误:

[eslint] 迭代器 [react/jsx-key] 中元素缺少“key”属性

我不确定我是否正确执行了此操作，但我已为用户列表中的每个人分配了唯一的 ID 号，但不确定为什么错误持续存在。

因此，在我的 PeopleCard.js 中，我有以下内容:

import React from "react";
import {
  Card,
  CardImg,
  CardText,
  CardBody,
  CardTitle,
  CardSubtitle,
  Button
} from "reactstrap";
import PropTypes from "prop-types";

class PeopleCard extends React.Component {
  static propTypes = {
    person: PropTypes.object,
    id: PropTypes.number,
    name: PropTypes.string,
    company: PropTypes.string,
    description: PropTypes.string
  };
  render() {
    return (
      <div>
        <Card>
          <CardImg
            top
            width="100%"
            src="https://via.placeholder.com/318x180.png"
            alt="Card image cap"
          />
          <CardBody>
            <CardTitle>{this.props.person.name}</CardTitle>
            <CardSubtitle>{this.props.person.company}</CardSubtitle>
            <CardText>{this.props.person.description}</CardText>
            <Button>Button</Button>
          </CardBody>
        </Card>
      </div>
    );
  }
}

export default PeopleCard;

在我的 MainArea.js 中，我有以下内容:

import React from "react";
import { Container, Row, Col } from "reactstrap";
import PeopleCard from "./PeopleCard";

class MainArea extends React.Component {
  constructor() {
    super();
    this.state = {
      people: [
        {
          id: 1,
          name: "John",
          company: "Some Company, Inc",
          description: "Met at a party."
        },
        {
          id: 2,
          name: "Mary",
          company: "Some Company, Inc",
          description: "Met at a party."
        },
        {
          id: 3,
          name: "Jane",
          company: "Some Company, Inc",
          description: "Met at a party."
        }
      ]
    };
  }
  render() {
    let peopleCard = this.state.people.map(person => {
      return (
        <Col sm="4">
          <PeopleCard key={person.id} person={person} />
        </Col>
      );
    });
    return (
      <Container fluid>
        <Row>{peopleCard}</Row>
      </Container>
    );
  }
}

export default MainArea;

以下行抛出错误，我无法弄清楚原因:

<Col sm="4">
   <PeopleCard key={person.id} person={person} />
</Col>

如何防止出现此错误？

Answer 1

您应该将键放在循环内的外部元素上:

const peopleCard = this.state.people.map(person => (
  <Col key={person.id} sm="4">
    <PeopleCard person={person} />
  </Col>
));

如果在某些罕见的情况下你有两个元素，那么你可以将键放在 React.Fragment 上:

const peopleCard = this.state.people.map(person => (
  <React.Fragment key={person.id}>
    <Col key={person.id} sm="4">
      <PeopleCard person={person} />
    </Col>
    <SomeOtherElement />
  </React.Fragment>
));