猫鼬查找查询未执行

Question

I am trying to fetch some data from a mongodb. I am able to fetch the details from the model MyModel (defined in Server.js). But I can't execute the find method in the model Skill (defined in Skill.js).

Server.js

  let express = require('express');
  let app = express();
  var config = require('./config/config');
  let bodyParser = require('body-parser');
  var mongoose = require('mongoose');
  var cors = require('cors')
  var path = require("path");
  let Skill = require('./app/models/Skill');
  const dbURI = config.dbURI;
  app.use(cors());
  app.use(bodyParser.json(true));
  mongoose.connect(dbURI, {useNewUrlParser: true});
  mongoose.connection.on('connected', function () {
         console.log("Connected");
  }); 
  var MyModel = mongoose.model('Test', new Schema({ name: String 
  }));
  Skill.findOne(function(error, result) { 
           console.log("1",error,result);
  });
  MyModel.findOne(function(error, result) { 
           console.log("2",error,result); 
  });
  app.listen(config.appPort,function () {
          console.log('App running on port :: "' + config.appPort.toString() + '"');

  });

app/models/Skill.js

 var mongoose = require('mongoose');

 var skillSchema = new mongoose.Schema({
       name: String,
       length: String,
 });

 var Skill = mongoose.model('Skill', skillSchema,'Skill');
 module.exports = Skill; 

Output

   App running on port :: "8080"
   Conneccted
   2 null { _id: 5c6678215c50a65e59fc6a89, name: 'test', __v: 0 }

I haven't found any issues while creating the schema. Could someone help me to resolve the issue?

Answer 1

I can't test my suggestion at the moment, but one thing I noticed in your code is that you queries, as in

Skill.findOne(function(error, result) { 
       console.log("1",error,result);
});
MyModel.findOne(function(error, result) { 
        console.log("2",error,result); 
});

are not executed in the "connected" callback; may be it's not the main problem, but I would try to change the code as follows:

mongoose.connection.on('connected', function () {
    console.log("Connected");
    Skill.findOne(function(error, result) { 
       console.log("1",error,result);
    });
    MyModel.findOne(function(error, result) { 
        console.log("2",error,result); 
    });
});

The key thing is that each call ( .on , .findOne ) starts a promise , which encapsulates an asynchronous behaviour. I you place ,findOne invocation just after .on invocation, you can't be sure Mongoose's connection is ready when you starts .findOne ...