猫鼬错误：填充时尚未为模型注册架构

Question

我正在尝试加入两个集合并能够获取合并的数据。要使用Mongoose做到这一点，我应该使用填充语法来实现这一点。我收到未为“ User_Fb”注册架构模式的错误。从我的代码中，我已经导出了模型，并且在server.js中需要它，但是错误仍然出现。我做错了什么？

feed_post.model.js

var mongoose = require('mongoose');
var conn_new_app     = mongoose.createConnection('mongodb://localhost/new_app');
var User_fb = require('../models/fb_db.model');

var Schema = mongoose.Schema;
var feed_postSchema = new Schema({
    user_id:  { type: Schema.Types.ObjectId, ref: 'User_Fb' },
    content: String,
    location: String,
    image: [{ type : String }]
});

var Feed_Post = conn_new_app.model('Feed_Post', feed_postSchema);

module.exports = Feed_Post;

fb_db.model.js

var mongoose = require('mongoose');
var conn_new_app     = mongoose.createConnection('mongodb://localhost/new_app');
var Feed_Post = require('../models/feed_post.model');

var user_fb = new mongoose.Schema({
    name: String,
    location: String,
    fb_id: Number
});

var User_Fb = conn_new_app.model('User_Fb', user_fb);

module.exports = User_Fb;

server.js

var express = require('express'),

mongoose = require('mongoose'),
User = require('./app/models/user.model'),
Post = require('./app/models/post.model'),
Maptest = require('./app/models/maptest.model'),
Feed_Post = require('./app/models/feed_post.model'),
User_Fb = require('./app/models/fb_db.model'),

app = express();

app.get('/testget', function(req,res){
    Feed_Post.findOne().populate('user_id').exec(function(err, c) {
        if (err) { return console.log(err); }

        console.log(c.fk_user.userName);
    });
});

从Pier-Luc Gendreau Answer's更新

fb_db.model.js

module.exports = function (connection) {
    var mongoose = require('mongoose');
    var Schema = mongoose.Schema;

    var user_fb = new mongoose.Schema({
        name: String,
        location: String,
        fb_id: Number
    });

    return connection.model('User_FB', user_fb);;
}

feed_post.model.js

module.exports = function (connection) {
    var mongoose = require('mongoose');
    var Schema = mongoose.Schema;

    var feed_postSchema = new Schema({
        user_id:  { type: Schema.Types.ObjectId, ref: 'User_Fb' },
        content: String,
        location: String,
        image: [{ type : String }]
    });

    return connection.model('Feed_Post', feed_postSchema);;
}

server.js

var express = require('express'),
app = express(),

mongoose = require('mongoose'),
conn_new_app = mongoose.createConnection('mongodb://localhost/new_app'),
User_Fb = require('./app/models/fb_db.model')(conn_new_app),
Feed_Post = require('./app/models/feed_post.model')(conn_new_app);

app.get('/testget', function(req,res){
    Feed_Post.find().populate('user_id').exec(function(err, res) {
        if (err) { return console.log(err); }
        console.log(res);
    });
});

Answer 1

如果您（真的）使用多个 mongoDB 连接

我确实意识到这不是 OP 的情况，但是如果您真正使用多个连接，则必须在使用 .populate() 时提供模型，因为 mongoose 只会在同一连接上“找到”模型。即在哪里：

var db1 = mongoose.createConnection('mongodb://localhost:27017/gh3639');
var db2 = mongoose.createConnection('mongodb://localhost:27017/gh3639_2');
var userSchema = mongoose.Schema({
  "name": String,
  "email": String
});

var customerSchema = mongoose.Schema({
  "name" : { type: String },
  "email" : [ String ],
  "created_by" : { type: mongoose.Schema.Types.ObjectId, ref: 'users' },
});

var User = db1.model('users', userSchema);
var Customer = db2.model('customers', customerSchema);

正确的：

Customer.findOne({}).populate('created_by', 'name email', User)

或者

Customer.findOne({}).populate({ path: 'created_by', model: User })

不正确（产生“模式尚未为模型注册”错误）：

Customer.findOne({}).populate('created_by');

Answer 2

问题是您要在每个模型中创建一个新的连接，因此最终会遇到许多不同的连接对象。即使它们指向同一个数据库，猫鼬模型也不知道其他连接。您应该改为在主应用程序中创建连接对象，然后再传递它。

server.js

var express = require('express');
var mongoose = require('mongoose');

var app = express();
var conn_new_app = mongoose.createConnection('mongodb://localhost/new_app');
var Feed_Post = require('./app/models/feed_post.model')(conn_new_app);

app.get('/testget', function(req,res){
  Feed_Post.findOne().populate('user_id').exec(function(err, c) {
    if (err) { return console.log(err); }
    console.log(c.fk_user.userName);
  });
});

然后修改模型，使它们实际上是一个函数：

feed_post.model.js

module.exports = function (connection) {
  var mongoose = require('mongoose');
  var Schema = mongoose.Schema;

  var feed_postSchema = new Schema({
    user_id:  { type: Schema.Types.ObjectId, ref: 'User_Fb' },
    content: String,
    location: String,
    image: [{ type : String }]
  });

  return connection.model('Feed_Post', feed_postSchema);;
}

此外，就像Adrian提到的那样，您可以将猫鼬用作单身人士。但是，我建议createConnection您照常使用，因为如果您需要第二个连接，则不必将连接代码重构到第一个数据库。

Answer 3

这就是我要做的，Customer.findOne({}).populate({ path: 'created_by', model: User })而不是〜Category.findOne（{}）。populate（{'author'}）〜