TypeScript NodeJS TypeError：无法读取未定义的属性“地址”

Question

我是 TS 新手，所以我不知道为什么会吐出那个错误

VanillaJS 版本运行良好。 将其转移到 TypeScript。 错误在我的 index.ts 中。 使用 tsc 命令编译 TS 代码还是一样的。 如果我在constructor() 中使用console.log(this.server) 正常输出对象 但是当我在 theListening() 上使用 console.log(this.server) 时，它说 undefined 它很奇怪。

app.ts 文件

import * as express from 'express'
import * as http from 'http'
import * as bodyParser from 'body-parser'
import * as cookieParser from 'cookie-parser'
import * as path from 'path'
import indexRoutes from './routes/index'
import userRoutes from './routes/users'

class App {

  public express

  constructor () {
    this.express = express()
    this.middleware()
    this.mountRoutes()
    this.errorHandler()
  }

  private middleware(): void {
    this.express.use(bodyParser.json())
    this.express.use(bodyParser.urlencoded({ extended: false }))

    this.express.use(cookieParser())
    this.express.use(express.static(path.join(__dirname, 'public')))
  }

  private mountRoutes(): void {
    this.express.use('/', indexRoutes)
    this.express.use('/users', userRoutes)
  }

  private errorHandler(): void {
    this.express.use((req, res, next) => {
      let err:any = new Error('Not Found') // I don't know why the err var needs the :any type to work with err.status below it. Without the :any type err.status is spitting errors hahaha
      err.status = 404
      next(err)
    });

    this.express.use((err, req, res, next) => {
      res.locals.message = err.message
      res.locals.error = req.app.get('env') === 'development' ? err : {}

      res.status(err.status || 500)
      res.json({
        message: 'Error'
      })
    })
  }
}

export default new App().express

index.ts 文件

import app from './app'
import * as debug from 'debug'
import * as http from 'http'

class Server {

 public server

 public port

 public debug

constructor () {
  this.debug = debug('myexpress:server')
  this.port = this.normalizePort(process.env.PORT || '3000')
  app.set('port', this.port)
  this.server = http.createServer(app)
  this.server.listen(this.port)
  this.server.on('error', this.onError)
  this.server.on('listening', this.onListening)
}

private normalizePort(val): any {
  let port = parseInt(val, 10)

  if (isNaN(port)) {
    return val
  }

  if (port >= 0) {
    return port
  }

  return false
}

private onError(error): void {
  if (error.syscall !== 'listen') {
    throw error
  }

  let bind = typeof this.port === 'string' ? 'Pipe ' + this.port : 'Port' + 
     this.port

  switch (error.code) {
    case 'EACCES':
      console.error(bind + ' requires elevated privileges')
      process.exit(1)
      break

    case 'EADDRINUSE':
      console.error(bind + ' is already in use')
      process.exit(1)
      break

    default:
      throw error
  }
}

public onListening(): void {
    let addr = this.server.address() << THIS RIGHT HERE

    let bind = typeof addr === 'string' ? 'pipe ' + addr : 'port ' + 
    addr.port

    debug('Listening on ' + bind)
  }
}

new Server()

Answer 1

首先，在使用 .on（监听器）时，将您的方法绑定到正确的范围。

this.server.on('listening', this.onListening.bind(this))

或

this.server.on('listening', (e) => this.onListening(e))