Question

所以，我正在运行这段代码：

this.db.getDocumentClient()
      .then(client => client.query(params).promise())
      .then(data => { this.items = data.Items; })
      .catch(err => logger.debug('error in refresh tasks', err))
      .then(() => { this.refresher && this.refresher.complete() });

并收到此错误：

 typescript: D:/Developer/scrum/myApp123/src/pages/tasks/tasks.ts, line: 51
        Property 'query' does not exist on type 'void | DocumentClient'. Property 'query' does not exist on type
        'void'.

世界上有什么类型'无效| DocumentClient“？ getDocumentClient看起来像这样：

    getDocumentClient() {
    return Auth.currentCredentials()
      .then(credentials => new AWS.DynamoDB.DocumentClient({ credentials: credentials }))
      .catch(err => logger.debug('error getting document client', err));
  }

Answer 1

Promise<void | DocumentClient>是getDocumentClient()函数的返回类型。问题是在.catch中你没有重新抛出错误，函数解析为Promise<void>。要解决此问题，请将方法更改为：

getDocumentClient() {
    return Auth.currentCredentials()
      .then(credentials => new AWS.DynamoDB.DocumentClient({ credentials: credentials }))
      .catch(err => { logger.debug('error getting document client', err); throw err; });
  }

这将导致主代码中的promise失败并进入catch部分，而不是解析为void然后获取运行时错误。

Javascript / typescript promise有两种类型？

1 个答案: