javascript - 如何从 MongoDB 返回数据

Question

我正在尝试使用 Mongoose 查询我的 MongoDB 数据库。我正在使用 findOne 按 object_id 进行搜索，目的是从相应的对象返回“开始”和“结束”字段。但是，我没有将两条消息之一记录到控制台，而是得到“未定义”。我的模式、我的事件集合中的示例对象和查询代码如下:

Mongoose 模式:

var mongoose = require('mongoose');

var Schema = mongoose.Schema;

var eventSchema = new Schema({
  event: String,
  city: String,
  state: String,
  date: String,
  start: String,
  end: Number,
  radius: String,
  team_1: String,
  team_2: String,
  object_id: String,
  photos: []
})

module.exports = mongoose.model('Event', eventSchema);

来自 MongoDB 事件集合的示例对象:

{
  "_id": {
    "$oid": "5495d1e2ac1e3caaeee84483"
  },
  "event": "Rockefeller Center",
  "city": "New York",
  "state": "New York",
  "date": "",
  "start": "December 18, 2014",
  "end": "January 2, 2015",
  "radius": "40",
  "team_1": "",
  "team_2": "",
  "object_id": "10881503",
  "photos": []
}

服务器代码:

//loop through incoming API POSTS. object_id is guaranteed to be in 'data'
req.body.forEach(function (data) {

  var result = Event.findOne(
    {object_id: data.object_id}, 
    { start: 1, end: 1 }
  );

  if (result) {
    var startDate = result.start;
    console.log(startDate);
  } else {
    console.log('object_id not found');
  }
});

Answer 1

Mongoose 为 MongoDB 提供异步接口(interface)，因此 findOne 不会返回找到的文档，而是将其传递给您作为另一个参数提供的回调函数。

req.body.forEach(function (data) {

  Event.findOne(
    {object_id: data.object_id}, 
    { start: 1, end: 1 },
    function(err, result) {
      if (result) {
        var startDate = result.start;
        console.log(startDate);
      } else {
        console.log('object_id not found');
      }
    }
  );

});