网络请求后如何进行回调？

call() {
      this.getData().    then(res => {
        console.log(res)
  }).    catch((e: BusinessError) => {
        console.log(e.message)
  })

  this.getDataWithCallback((err, res) => {
        if (err) {
          console.log(err.message)
    }     else {
          console.log(res)
    }
  })
}

getData(): Promise<string> {
  return new Promise((resolve, reject) => {
    // 假设进行网络请求得到响应结果
    let code = 200
    // let code = 500
        if (code == 200) {
      resolve('hello world!')
    }     else {
      let e: BusinessError = {
        code: code,
        name: 'ServerInternalError',
        message: 'Sorry, something went wrong!'
      }
      reject(e)
    }
  })
}

getDataWithCallback(callback: (err: BusinessError | null, res?: string) => void): Promise<string> {
  return new Promise((_resolve, _reject) => {
    // 假设进行网络请求得到响应结果
    // let code = 200
    let code = 500
        if (code == 200) {
      callback(null, 'hello world!')
    }     else {
      let e: BusinessError = {
        code: code,
        name: 'ServerInternalError',
        message: 'Sorry, something went wrong!'
      }
      callback(e)
    }
  })
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