创建后如何在 mongoose 中填充子文档? [英] How to populate a sub-document in mongoose after creating it?

问题描述

我正在向 item.comments 列表添加评论.在响应中输出之前，我需要获取 comment.created_by 用户数据.我该怎么做?

I am adding a comment to an item.comments list. I need to get the comment.created_by user data before I output it in the response. How should I do this?

    Item.findById(req.param('itemid'), function(err, item){
        var comment = item.comments.create({
            body: req.body.body
            , created_by: logged_in_user
        });

        item.comments.push(comment);

        item.save(function(err, item){
            res.json({
                status: 'success',
                message: "You have commented on this item",

//how do i populate comment.created_by here???

                comment: item.comments.id(comment._id)
            });
        }); //end item.save
    }); //end item.find

我需要在 res.json 输出中填充 comment.created_by 字段:

I need to populate the comment.created_by field here in my res.json output:

                comment: item.comments.id(comment._id)

comment.created_by 是我的猫鼬 CommentSchema 中的用户引用.它目前只给我一个用户 ID，我需要用所有用户数据填充它，密码和盐字段除外.

comment.created_by is a user reference in my mongoose CommentSchema. It currently is only giving me a user id, I need it populated with all the user data, except for password and salt fields.

这是人们询问的架构:

var CommentSchema = new Schema({
    body          : { type: String, required: true }
  , created_by    : { type: Schema.ObjectId, ref: 'User', index: true }
  , created_at    : { type: Date }
  , updated_at    : { type: Date }
});

var ItemSchema = new Schema({
    name    : { type: String, required: true, trim: true }
  , created_by  : { type: Schema.ObjectId, ref: 'User', index: true }
  , comments  : [CommentSchema]
});

推荐答案

为了填充引用的子文档，您需要明确定义 ID 引用的文档集合(例如 created_by: { type: Schema.Types.ObjectId, ref: 'User' }).

In order to populate referenced subdocuments, you need to explicitly define the document collection to which the ID references to (like created_by: { type: Schema.Types.ObjectId, ref: 'User' }).

鉴于此引用已定义并且您的架构也已定义良好，您现在可以像往常一样调用 populate(例如 populate('comments.created_by'))

Given this reference is defined and your schema is otherwise well defined as well, you can now just call populate as usual (e.g. populate('comments.created_by'))

概念验证代码:

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

var UserSchema = new Schema({
  name: String
});

var CommentSchema = new Schema({
  text: String,
  created_by: { type: Schema.Types.ObjectId, ref: 'User' }
});

var ItemSchema = new Schema({
   comments: [CommentSchema]
});

// Connect to DB and instantiate models    
var db = mongoose.connect('enter your database here');
var User = db.model('User', UserSchema);
var Comment = db.model('Comment', CommentSchema);
var Item = db.model('Item', ItemSchema);

// Find and populate
Item.find({}).populate('comments.created_by').exec(function(err, items) {
    console.log(items[0].comments[0].created_by.name);
});

最后注意 populate 仅适用于查询，因此您需要先将您的项目传递到查询中，然后再调用它:

Finally note that populate works only for queries so you need to first pass your item into a query and then call it:

item.save(function(err, item) {
    Item.findOne(item).populate('comments.created_by').exec(function (err, item) {
        res.json({
            status: 'success',
            message: "You have commented on this item",
            comment: item.comments.id(comment._id)
        });
    });
});

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