使用异步库汇编数据库中的所有标记

I am using sails.js to create a tag system that has many-to-many relations with an entity called Post. The way I am doing the association is to use a database table to correlate each tagId with the postId. Each Post can have multiple tags.

我正在使用sails.js创建一个标签系统,该系统与名为Post的实体具有多对多关系。我正在进行关联的方式是使用数据库表将每个tagId与postId相关联。每个帖子可以有多个标签。

After I retrieve an array of {tagId : 'tagId, postId: 'postId'} objects, I need to retrieve the tag names for each tagId. I am using the async library, but the array of tag names (String) returns an empty one, from the logging info, I can see that the return happens before the completion of the iterator function. My code is following:

在检索{tagId:'tagId,postId:'postId'}对象的数组后,我需要检索每个tagId的标记名称。我正在使用异步库,但标记名称(String)数组返回一个空的,从日志信息中,我可以看到返回发生在迭代器函数完成之前。我的代码如下:

var tagIdPostIds = [
{tagId : 'abcx', postId: 1},
{tagId : 'abce', postId: 1},
{tagId : 'abcd', postId: 1},
];

if (tagIdPostIds) {
        var tagsArr = []; //container of tag names

        var findTagById = function(tagIdPostIdObj, cb) {
          var tagId = tagIdPostIdObj.tagId;

          Tag.findOneById(tagId, function (err, foundTag) {
            if (err) return sendErrorMsgCode(res, "error in retrieving a tag", 401);

            if (foundTag) {
              sails.log.info('pushing in tag: ' + foundTag.tagName);
              tagsArr.push(foundTag.tagName);
            }
          });

          cb(); //without this, the program just hangs, but why??

        }; //findTagById


        var retTagNames = function(err) {
          if (err) return sendErrorMsgCode(res, "error in assembling tag names", 401);
          sails.log.info('returning tagsArr: ' + JSON.stringify(tagsArr));
          return res.json(tagsArr);
        }; //retTagNames

        async.eachSeries(tagIdPostIds, findTagById, retTagNames);
      }

After reading the documentation of async, I think async.map() may be what I need to assemble all tags for a given postId. Or my way of using async.eachSeries() is wrong?

在阅读了异步文档之后,我认为async.map()可能是我需要为给定的postId汇编所有标签。或者我使用async.eachSeries()的方式是错误的?

Thanks for your help

谢谢你的帮助

1 个解决方案

#1

Just wanted to post this correct answer by incorporating @Ben's answer in his comments from above so others can easily find what worked for me:

只是想通过在上面的评论中加入@Ben的答案来发布这个正确答案,以便其他人可以轻松找到对我有用的内容:

var tagIdPostIds = [
{tagId : 'abcx', postId: 1},
{tagId : 'abce', postId: 1},
{tagId : 'abcd', postId: 1},
];

if (tagIdPostIds) {
        var tagsArr = []; //container of tag names

        var findTagById = function(tagIdPostIdObj, cb) {
          var tagId = tagIdPostIdObj.tagId;

          Tag.findOneById(tagId, function (err, foundTag) {
            if (err) return sendErrorMsgCode(res, "error in retrieving a tag", 401);

            if (foundTag) {
              sails.log.info('pushing in tag: ' + foundTag.tagName);
              tagsArr.push(foundTag.tagName);
            }
            cb(); //this must be placed inside an async call to make it work!
          });



        }; //findTagById


        var retTagNames = function(err) {
          if (err) return sendErrorMsgCode(res, "error in assembling tag names", 401);
          sails.log.info('returning tagsArr: ' + JSON.stringify(tagsArr));
          return res.json(tagsArr);
        }; //retTagNames

        async.eachSeries(tagIdPostIds, findTagById, retTagNames);
      }

1 个解决方案

#1

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