Node.js Mongoose模式字段定义问题（关键字：nodejs、req.body、extend、field、type）

我花了半个小时才弄明白是什么问题，所以我需要发布这个问题，以节省您宝贵的时间

---

我有一个模式，它的定义如下：

var mongoose = require('mongoose');
var ItemSchema = new mongoose.Schema({

    title: String,
    desc: String,
    price: Number,

    owner: { // this field would be filled with req.session.user
        uid: {type: Number, index: true},
        nickname: String,
        contact: String
    }
});

module.exports = mongoose.model('ItemSchema', ItemSchema);

console.log( req.body );
/*
    {
        title: 'apple',
        desc: 'nice apple',
        price: 100
    }
*/

> db.item.findOne();
{
    _id: ObjectId('xxxxxxxxxxxxxxxxxxxxxxxx'),
    title: 'apple',
    desc: 'nice apple',
    price: 100
}

req.body.user = {
    uid: req.session.user.uid,
    nickname: req.session.user.nickname,
    contact: req.session.user.contact
}; // It works, but looks stupid

---

然后，如果前端发送post请求，如下所示：

var mongoose = require('mongoose');
var ItemSchema = new mongoose.Schema({

    title: String,
    desc: String,
    price: Number,

    owner: { // this field would be filled with req.session.user
        uid: {type: Number, index: true},
        nickname: String,
        contact: String
    }
});

module.exports = mongoose.model('ItemSchema', ItemSchema);

console.log( req.body );
/*
    {
        title: 'apple',
        desc: 'nice apple',
        price: 100
    }
*/

> db.item.findOne();
{
    _id: ObjectId('xxxxxxxxxxxxxxxxxxxxxxxx'),
    title: 'apple',
    desc: 'nice apple',
    price: 100
}

req.body.user = {
    uid: req.session.user.uid,
    nickname: req.session.user.nickname,
    contact: req.session.user.contact
}; // It works, but looks stupid

---

我的快速路由器代码，写在：

...
req.body.owner = req.session.user;

var newItem = new ItemSchema( req.body );

newItem.save(function(err, re) {
    if (err) throw err;
    res.json(re);
});

---

之后，我的ItemSchema添加了一条记录（文档）。但它不包含用户字段，如下所示：

var mongoose = require('mongoose');
var ItemSchema = new mongoose.Schema({

    title: String,
    desc: String,
    price: Number,

    owner: { // this field would be filled with req.session.user
        uid: {type: Number, index: true},
        nickname: String,
        contact: String
    }
});

module.exports = mongoose.model('ItemSchema', ItemSchema);

console.log( req.body );
/*
    {
        title: 'apple',
        desc: 'nice apple',
        price: 100
    }
*/

> db.item.findOne();
{
    _id: ObjectId('xxxxxxxxxxxxxxxxxxxxxxxx'),
    title: 'apple',
    desc: 'nice apple',
    price: 100
}

req.body.user = {
    uid: req.session.user.uid,
    nickname: req.session.user.nickname,
    contact: req.session.user.contact
}; // It works, but looks stupid

---

太奇怪了！！！用户字段在哪里

---

我必须强调，如果console.log（req.body）包含用户字段

---

首先，我创建了一个解决方案，如下所示：

var mongoose = require('mongoose');
var ItemSchema = new mongoose.Schema({

    title: String,
    desc: String,
    price: Number,

    owner: { // this field would be filled with req.session.user
        uid: {type: Number, index: true},
        nickname: String,
        contact: String
    }
});

module.exports = mongoose.model('ItemSchema', ItemSchema);

console.log( req.body );
/*
    {
        title: 'apple',
        desc: 'nice apple',
        price: 100
    }
*/

> db.item.findOne();
{
    _id: ObjectId('xxxxxxxxxxxxxxxxxxxxxxxx'),
    title: 'apple',
    desc: 'nice apple',
    price: 100
}

req.body.user = {
    uid: req.session.user.uid,
    nickname: req.session.user.nickname,
    contact: req.session.user.contact
}; // It works, but looks stupid

---

然后我使用下划线：

var newItem = new ItemSchema( _.extend(req.body, {user: req.session.user}) ); // It doesn't work, I don't know why

---

最后，我发现这一定是猫鼬模式定义的问题，所以我尝试：

var ItemSchema = new mongoose.Schema({

    title: String,
    desc: String,
    price: Number,

    owner: {type: { // here is the key!!!
        uid: {type: Number, index: true},
        nickname: String,
        contact: String
    }}
});

---

从那时起，再也没有问题了，我可以编写代码：

req.body.user = req.session.user; // ok

---

但我发现我之前的定义应该是正确的，如下所述：

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

var blogSchema = new Schema({
  title:  String,
  author: String,
  body:   String,
  comments: [{ body: String, date: Date }],
  date: { type: Date, default: Date.now },
  hidden: Boolean,
  meta: { // here, same data structure with my user field
    votes: Number,
    favs:  Number
  }
});

---

---

那么，问题出在哪里呢？

我发现有一种猫鼬：Schema.Types.Mixed。因此：

...
user: {type: Schema.Types.Mixed}, // ok, but no index set
...

你可以在猫鼬身上建立一个

var UserSchema = new mongoose.Schema({

    uid: {type: Number, index: true},
    nickname: String,
    contact: String
}, {_id: false})

var ItemSchema = new mongoose.Schema({

    title: String,
    desc: String,
    price: Number,

    owner: UserSchema
});

---

最终，我意识到问题是，req.session.user不是一个普通的对象，让我们看看它是如何产生的：

// UserSchema.js
...
UserSchema.statics.getSessionFields = function(uid, cb) {
    this.findById(uid).select('uid nickname contact').exec(cb);
};
...


// app.js
...
app.use(function(req, res, next) {
    var UserDB = require('path/to/UserSchema.js');

    UserDB.getSessionFields(12345, function(err, re) {
        req.session.user = re; // here is the problem
        next();
    });
});
...

---

此re是一个查询对象，而不是仅包含uid、昵称、联系人的对象

---

因此，最终的解决方案是：

UserDB.getSessionFields(12345, function(err, re) {
    req.session.user = re.toJSON(); // just the way as Backbone
    next();
});