如何使用Mongoose查询虚拟字段？

Question

如何查询虚拟字段,以便它在JSON响应中

const ItemSchema = mongoose.Schema({
  name: String,
  time: { type: Date, default: Date.now }
});

ItemSchema.virtual('timeleft').get(function() {
  this.timeleft = 24

  var currentTime = moment(); 
  var timeStored = moment.utc(this.time).local().format(); 
  this.timeleft -= currentTime.diff(timeStored, 'h');


});

API调用

app.get('/getAllItems', function(req, res, next) {
   Item.find({}, function(err, items) {
     res.json(items);
   });
});

因此从技术上讲,响应将不包括虚拟时间段.我错过了什么吗？

[
 {
   name: "nike",
   time: "21/2/22"

  },

  {
   name: "adidas",
   time: "21/2/22"

  },
]

Answer 1

根据 Mongoose 文档，Mongoose 虚拟数据不存储在 MongoDB 中，这意味着您无法基于 Mongoose 虚拟数据进行查询。

// Will **not** find any results, because `domain` is not stored in
// MongoDB.
const doc = await User.findOne({ domain: 'gmail.com' });
doc; // undefined

如果您想通过计算属性进行查询，则应使用自定义设置器或预保存中间件来设置该属性。

Answer 2

// use Schema like this        
const ItemSchema = new Schema({
    name: String,
    time: { type: Date, default: Date.now }
}, {
    toObject: { virtuals: true },
    toJSON: { virtuals: true }
});

ItemSchema.virtual('timeleft').get(function() {
    // this.timeleft = 24
    var currentTime = moment();
    var timeStored = moment.utc(this.time).local().format();
    console.log(" ====== 000 ======== ", currentTime.diff(timeStored, 'h'))
    return this.timeleft = currentTime.diff(timeStored, 'h');
});

const Item = mongoose.model('Item', ItemSchema);

new Item({
    name: 'Axl'
}).save((err, result) => { 
    console.log("=== err ", err, "=== result ", result)
});

Item.find({}, function(err, items) {
    console.log("=========", items)
});

Answer 3

修改您的架构，如下所示：

const ItemSchema = mongoose.Schema({
    name: String,
    time: { type: Date, default: Date.now },
    toObject: { virtuals: true },  // <-- These properties will configure
    toJSON: { virtuals: true }     //     model to include virtuals
});

按如下方式修改您的 API 调用：

app.get('/getAllItems', function(req, res, next) {
    Item.find({}, function(err, items) {
        res.json(items.toObject());  // <-- use .toObject() or .toJSON()
    });
});