TypeError：无法在 React js 中读取未定义的属性（读取“参数”）

Question

我想通过传递员工 ID 来查看员工详细信息。 这是我的员工列表页面。

import React, { Component } from 'react'
import EmployeeService from '../employeeServices'
import { useNavigate } from 'react-router-dom'


class EmployeeList extends Component {
    constructor(props) {
        super(props)

        this.state = {
                employees: []
        }
        this.addEmployee = this.addEmployee.bind(this);
        this.editEmployee = this.editEmployee.bind(this);
        this.deleteEmployee = this.deleteEmployee.bind(this);
    }

    deleteEmployee(id){
        EmployeeService.deleteEmployee(id).then( res => {
            this.setState({employees: this.state.employees.filter(employee => employee.id !== id)});
        });
    }
    viewEmployee(id){
        this.props.navigate(`/viewEmployee/${id}`);
    }
    editEmployee(id){
        this.props.navigate(`/addEmployee/${id}`);
    }

    componentDidMount(){
        EmployeeService.getEmployees().then((res) => {
            this.setState({ employees: res.data});
            console.log(res.data);
        });
    }

    addEmployee(){
        this.props.navigate('/addEmployee/_add');
    }

    render() {
        return (
            <div>
                 <h2 className="text-center">Employees List</h2>
                 <div className = "row">
                    <button className="btn btn-primary" onClick={this.addEmployee}> Add Employee</button>
                 </div>
                 <br></br>
                 <div className = "row">
                        <table className = "table table-striped table-bordered">

                            <thead>
                                <tr>
                                    <th> Employee First Name</th>
                                    <th> Employee Last Name</th>
                                    <th> Employee Email Id</th>
                                    <th> Actions</th>
                                </tr>
                            </thead>
                            <tbody>
                                {
                                    this.state.employees.map(
                                        employee => 
                                        <tr key = {employee._id}>
                                             <td> {employee.firstName} </td>   
                                             <td> {employee.lastName}</td>
                                             <td> {employee.emailId}</td>
                                             <td>
                                                 <button onClick={ () => this.editEmployee(employee._id)} className="btn btn-info">Update </button>
                                                 <button style={{marginLeft: "10px"}} onClick={ () => this.deleteEmployee(employee.id)} className="btn btn-danger">Delete </button>
                                                 <button style={{marginLeft: "10px"}} onClick={ () => this.viewEmployee(employee._id)} className="btn btn-info">View </button>
                                             </td>
                                        </tr>
                                    )
                                }
                            </tbody>
                        </table>

                 </div>

            </div>
        )
    }
}
function WithNavigate(props){
    const navigate = useNavigate();
    return <EmployeeList {...props} navigate={navigate}/>
}
export default WithNavigate;

在下面您可以看到我的员工详细信息查看页面。

import React, { Component } from 'react'
import EmployeeService from '../employeeServices'

class ViewEmployees extends Component {
    constructor(props) {
        super(props)

        this.state = {
            id: this.props.match.params.id,
            employee: {}
        }
    }

    componentDidMount(){
        EmployeeService.getEmployeeById(this.state.id).then( res => {
            this.setState({employee: res.data});
            console.log(this.state.id);
        })
    }

    render() {
        return (
            <div>
                <br></br>
                <div className = "card col-md-6 offset-md-3">
                    <h3 className = "text-center"> View Employee Details</h3>
                    <div className = "card-body">
                        <div className = "row">
                            <label> Employee First Name: </label>
                            <div> { this.state.employee.firstName }</div>
                        </div>
                        <div className = "row">
                            <label> Employee Last Name: </label>
                            <div> { this.state.employee.lastName }</div>
                        </div>
                        <div className = "row">
                            <label> Employee Email ID: </label>
                            <div> { this.state.employee.emailId }</div>
                        </div>
                    </div>

                </div>
            </div>
        )
    }
}

export default ViewEmployees;

我把<Route path = "/viewEmployee/:id" element={<ViewEmployees/>}></Route>放在我的 App.js 中。

当我单击employeeList 页面上的查看按钮时，它显示诸如TypeError 之类的错误：无法读取未定义的属性（读取“参数”）

我该如何克服呢？

Answer 1

尝试使用useParams挂钩检索参数：

import { useParams } from 'react';

...
    constructor(props) {
        super(props)

        this.state = {
            id: -1,
            employee: {}
        }
    }

    componentDidMount(){
        const { id } = useParams();
        this.setState({ id })
        EmployeeService.getEmployeeById(this.state.id).then( res => {
            this.setState({employee: res.data});
            console.log(this.state.id);
        })
    }