NodeJS中require的顺序似乎会产生错误

Question

I am having a problem with the order that i require various models in my main server.js file in NodeJS. Here is my product.js Product model file:

var mongoose = require("mongoose");

var Dealer      = require("./dealer.js")
var productSchema = new mongoose.Schema({
    title: String,
    price: String,
    dealers: [
        {
            type: mongoose.Schema.Types.ObjectId,
            ref: "Dealer"
        }
    ]
});

var Product = mongoose.model("Product", productSchema);

Dealer.findOne({
    name: "Glaze"
}, function(err, dealer){
    Product.findOne({title: "Awesome Metal Towels"}, function(err, product){
        if(err){
            console.log(err);
        } else{
            product.dealers.push(dealer);
            product.save(function(err, data){
                if(err){
                    console.log(err);
                } else{
                    console.log(data);
                }
            })
        }
    });
});

module.exports = mongoose.model("Product", productSchema);

Here is my Dealer.js file that defines the Dealer model:

var mongoose = require("mongoose");
var Product = require("./product.js")
var dealerSchema = new mongoose.Schema({
    name: String,
    owner: String,
    estd: Number,
    description: String,
    legal: String,
    facilities: String,
    awards: String,
    hours: String,
    turnover: String,
    mode: String,
    employees: String,
    contact: String,
    address: String,
    email: String,
    notes: String,
    website: String,
    products: [
        {
            type: mongoose.Schema.Types.ObjectId,
            ref: "Product"
        }
    ]
});


var Dealer = mongoose.model("Dealer", dealerSchema);

Product.find(function(err, data){
    console.log(data);
});

Product.findOne({
    title: "Awesome Metal Towels"
}, function(err, product){
    Dealer.findOne({name: "Glaze"}, function(err, dealer){
        if(err){
            console.log(err);
        } else{
            dealer.products.push(product);
            dealer.save(function(err, data){
                if(err){
                    console.log(err);
                } else{
                    console.log(data);
                }
            })
        }
    });
});


module.exports = mongoose.model("Dealer", dealerSchema);

And here is the main server.js file :

var express     = require("express");
var app         = express();
var bodyParser  = require("body-parser");
// var seedDB      = require("./seeds.js")
var mongoose    = require("mongoose");

// Connecting the models ////////////////////
var Dealer      = require("./models/dealer.js");
var Product     = require("./models/product.js");
var Category    = require("./models/category.js");
var Brand       = require("./models/brand.js");
/////////////////////////////////////////////

app.use(express.static(__dirname + '/public')); 
//Connecting to the database
var uri = process.env.MONGOLAB_URI || '127.0.0.1/flapi';
mongoose.connect(uri);
//////////////////////////////////////////////
//
//Seeding the database 
// seedDB();
//////////////////////

//Body Parser
app.use(bodyParser.urlencoded({extended:true}));
app.use(bodyParser.json());
////////////////////////////////////////////////////

var port = process.env.PORT || 3000;

// CRUD Routes for Products ///////////////////////////////////////////////////////

..................

The error I get while running the code is :

/home/aayush/fl/models/product.js:16
Dealer.findOne({
       ^

TypeError: Dealer.findOne is not a function
    at Object.<anonymous> (/home/aayush/fl/models/product.js:16:8)
    at Module._compile (module.js:435:26)
    at Object.Module._extensions..js (module.js:442:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:311:12)
    at Module.require (module.js:366:17)
    at require (module.js:385:17)
    at Object.<anonymous> (/home/aayush/fl/models/dealer.js:29:15)
    at Module._compile (module.js:435:26)
    at Object.Module._extensions..js (module.js:442:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:311:12)
    at Module.require (module.js:366:17)
    at require (module.js:385:17)
    at Object.<anonymous> (/home/aayush/fl/server.js:8:19)

I am not able to figure out what I am doing wrong. When I reverse the order of var Dealer and var Product in the serve.js file, I get another error saying that Product.findOne is not defined.

Please help!

Answer 1

Define both of your schemas prior to using them to eliminate the cycle. The schemas do not need to require each other. You can remove the find/findOne calls from the models and call them after they are instantiated.

It looks like you may be combining the product schema with the findOne of the dealers to try to push dealer data to the products schema. The schema should not change based on the documents for another schema.

There is a good example at http://mongoosejs.com/docs/populate.html for how to use two schemas with references to documents in other collections. This shows it without requiring the schemas to require one another.

Update

I have hooked up a quick working example. This will run if mongod is running locally.

server.js

var express     = require("express");
var app         = express();
var bodyParser  = require("body-parser");
var mongoose    = require("mongoose");
var ObjectID = require('mongodb').ObjectID;
var Dealer      = require("./models/dealer.js");
var Product     = require("./models/product.js");
app.use(express.static(__dirname + '/public')); 
mongoose.connect('mongodb://localhost:27017/test');

var db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
  var glaze = new Dealer({
    _id: new ObjectID(),
    name: 'Glaze', 
    owner: 'owner',
    estd: 2010,
    description: 'description',
    legal: 'legal',
    facilities: 'facilities',
    awards: 'awards',
    hours: 'hours',
    turnover: 'turnover',
    mode: 'mode',
    employees: 'employees',
    contact: 'contact',
    address: 'address',
    email: 'email@email.com',
    notes: 'notes',
    website: 'website.com',
  });

    glaze.save(function (err) {
      if (err) {
        console.error('err: ' + err);
      }

      var product1 = new Product({
        title: 'Awesome Metal Towels',
        price: '$17.99',
        dealers: []
      });

      product1.dealers.push(glaze._id);

      product1.save(function (err) {
      if (err) {
            console.error('err: ' + err);
          }
      });

        Product.find(function(err, data){
            console.log('[FIRST]: ' + data);
        });

        Product.findOne({
            title: "Awesome Metal Towels"
        }, function(err, product){
            Dealer.findOne({name: "Glaze"}, function(err, dealer){
                if(err){
                    console.log(err);
                } else{
                    dealer.products.push(product);
                    dealer.save(function(err, data){
                        if(err){
                            console.log(err);
                        } else{
                            console.log('[SECOND]: ' + data);
                        }
                    });
                }
            });
        });

    });
});

product.js

var mongoose = require("mongoose");

var productSchema = new mongoose.Schema({
    title: String,
    price: String,
    dealers: [
        {
            type: mongoose.Schema.Types.ObjectId,
            ref: "Dealer"
        }
    ]
});

module.exports = mongoose.model("Product", productSchema);

dealer.js

var mongoose = require("mongoose");
var dealerSchema = new mongoose.Schema({
    name: String,
    owner: String,
    estd: Number,
    description: String,
    legal: String,
    facilities: String,
    awards: String,
    hours: String,
    turnover: String,
    mode: String,
    employees: String,
    contact: String,
    address: String,
    email: String,
    notes: String,
    website: String,
    products: [
        {
            type: mongoose.Schema.Types.ObjectId,
            ref: "Product"
        }
    ]
});

module.exports = mongoose.model("Dealer", dealerSchema);

Run the above and the console for node prints:

[FIRST]: { dealers: [ 5684f0b71e8265a43e3c9c27 ],
  __v: 0,
  price: '$17.99',
  title: 'Awesome Metal Towels',
  _id: 5684f0b71e8265a43e3c9c28 }
[SECOND]: { products: [ 5684f0b71e8265a43e3c9c28 ],
  __v: 1,
  website: 'website.com',
  notes: 'notes',
  email: 'email@email.com',
  address: 'address',
  contact: 'contact',
  employees: 'employees',
  mode: 'mode',
  turnover: 'turnover',
  hours: 'hours',
  awards: 'awards',
  facilities: 'facilities',
  legal: 'legal',
  description: 'description',
  estd: 2010,
  owner: 'owner',
  name: 'Glaze',
  _id: 5684f0b71e8265a43e3c9c27 }

Hopefully this will help get in the right direction. I nested everything here to keep it simple. You would probably be better off with promises, generators or separate function calls.

Answer 2

Try:

var Dealer      = require("./dealer")
// ...
var Product = require("./product")

Instead of:

var Dealer      = require("./dealer.js")
// ...
var Product = require("./product.js")