Promise.all 正在返回一个未定义的数组

Question

函数返回未定义数组时遇到问题。

代码如下：

classMethods.getQueries = function(models, dbId, dateStart, dateEnd) {
  return new Promise(function(resolve, reject) {

    /* Fetch database .... */
    .then(extractQueries, reject)
    .then(sortQueries, reject)
    .then(onlyTen, reject)
    .then(addText, reject)
    .then(function(queries) {
      console.log('getQueries finished', queries) ;  //array of 10 undefined! 
      resolve(queries);
    }, reject);

    /* Functions here .... */

  });
};

在 addText 函数之前一切都很好：

function addText(queries) {
  return Promise.all(queries.map(function(query) {

    models.queries.findById(query.queryId, { raw: true, attributes: ['query'] })
    .then(function(queryFetched) {
      query.text = queryFetched.query;
      console.log(query);
      return Promise.resolve(query);
    }, function(error) {
       return Promise.reject(error);
    });

  }));
};

这给了我一个类似的输出：

getQueries finished [undedfined 10x]

10x  
[query database]
{queryId: ***, text: ********}

我不知道为什么在循环未完成时返回承诺。

感谢您的帮助。

Answer 1

所以这里是我的问题的解决方案：

function addText(queries) {
  return Promise.all(queries.map(function(query) {
    return new Promise(function(resolve, reject) {

      models.queries.findById(query.queryId, { raw: true, attributes: ['query'] })
      .then(function(queryFetched) {
         query.text = queryFetched.query;
         resolve(query);
      }, reject);

    });
  }));
};

Answer 2

这是因为您没有在地图的回调中返回任何承诺：

function addText(queries) {
  return Promise.all(queries.map(function(query) {
    // add return here or the map returns an array of undefined
    return models.queries
      .findById(query.queryId, {
        raw: true,
        attributes: ['query']
      })
      .then(function(queryFetched) {
        query.text = queryFetched.query;
        console.log(query);
        return Promise.resolve(query);
      }, function(error) {
        return Promise.reject(error);
      });

  }));
};