async.map 未按预期工作

Question

我正在尝试遍历一个集合并从相关集合中附加一个对象数组。我得到的结果不包含该数组。谁能帮我找出问题所在？

模特关系佩奇有很多问题

问题架构：

var mongoose = require('mongoose'),
    Schema = mongoose.Schema;

    var questionSchema = new Schema({
        _poll                  : { type: Schema.Types.ObjectId, ref: 'Poll' },
        _page                   : { type: Schema.Types.ObjectId, ref: 'Page' },  
        type                    : { type : String, required: true },  
        title                   : { type : String, required: true },  
        required                : { type : Boolean },  
        help_text               : { type : String },   
    },
    { timestamps: { createdAt: 'created_at', updatedAt: 'updated_at' } 
    });

    mongoose.model('Question', questionSchema);

页面架构：

var mongoose = require('mongoose'),
Schema = mongoose.Schema;

var pageSchema = new Schema({
    _poll              : { type: Schema.Types.ObjectId, ref: 'Poll' },
    title              : { type : String, required: true },  
    intro              : { type : String },  
    list_style_type    : { type : String },  
},
{ timestamps: { createdAt: 'created_at', updatedAt: 'updated_at' } 
});

mongoose.model('Page', pageSchema);

路线

索引：函数（请求、资源、下一个）{

Poll.findOne({_id: req.params.poll_id}, function(err, poll){
  if(err) return next(err);

  Page.find({_poll: poll.id}, function(err, pages){
    if(err) return next(err);

    async.map(pages, function(p, done) {
      Question.find({_page: p._id}, function(err, q){
        if(err) return next(err);
        p.questions = q;   //  <-- SHOULDN'T THIS WORK? //
        done(null, pages);
      });
    }, function(err, result) {
      if(err) return next(err);
      res.status(200).json(pages);
    })

  });
});

},

我得到的结果：

[
    {
    _id: "57d960fb569dc4101a83525e",
    updated_at: "2016-09-14T14:38:51.113Z",
    created_at: "2016-09-14T14:38:51.113Z",
    _poll: "57c88775992af4c84f99c5d0",
    title: "test section",
    list_style_type: "lower-roman",
    __v: 0
    },
    {
    _id: "57d9691e22eb81583e20a1c1",
    updated_at: "2016-09-14T15:13:34.244Z",
    created_at: "2016-09-14T15:13:34.244Z",
    _poll: "57c88775992af4c84f99c5d0",
    title: "this is a new page",
    list_style_type: "lower-roman",
    intro: "jkc hcsad",
    __v: 0
    },
    {
    _id: "57d9a97d1e7863b81f9e4d0e",
    updated_at: "2016-09-14T19:48:13.816Z",
    created_at: "2016-09-14T19:48:13.816Z",
    _poll: "57c88775992af4c84f99c5d0",
    title: "Consequatur Vero necessitatibus consequatur hic",
    list_style_type: "upper-latin",
    intro: "Rem laboris est omnis ducimus, minim autem itaque minim dolore ea odio aliqua. Autem qui id, sit nulla id.",
    __v: 0
    },
    {
    _id: "57dab7d7f54387d41d976614",
    updated_at: "2016-09-15T15:01:44.001Z",
    created_at: "2016-09-15T15:01:44.001Z",
    _poll: "57c88775992af4c84f99c5d0",
    title: "This is a new page",
    list_style_type: "lower-roman",
    intro: "cjksahc dsa",
    __v: 0
    }
]

我希望返回的对象包含数组 "questions" 但不知何故它不存在。

提前致谢！！

Answer 1

可能在您的 "Route" 代码中，传递给回调的变量有误。我认为 done(null, pages) 应该是 done(null, p) 而 res.status(200).json(pages) 应该是 res.status(200).json(result).

并且由于 mongoose 会忽略架构中不存在的字段，因此 questions 不会出现在您的结果中。在您的 "Route" 代码中，p 是一个猫鼬文档，您可以通过 .toObject().

将其转换为普通的 javascript 对象

所以也许您可以通过将您的代码替换为

来获得 questions 的结果：

async.map(pages, function(p, done) {
  Question.find({_page: p._id}, function(err, q){
    if(err) return next(err);
    p = p.toObject();  // convert a mongoose document into a javascript object
    p.questions = q;
    done(null, p);  // modified 'pages' -> 'p'
  });
}, function(err, result) {
  if(err) return next(err);
  res.status(200).json(result);  // modified 'pages' -> 'result'
})

async.map 未按预期工作

async.map not working as expected

node.js

express

mongoose

mean-stack

async.js