How to organize a node app that uses sequelize?

Question

The short story

The trick in this case is not to initialize the model in the file but just to provide the necesary information for its initialization and let a centralized module take care of the models setup and instantiation.

So the steps are:

• Have several Model files with data about the model, like fields, relationships and options.
• Have a singleton module which loads all those files and setup all the model classes and relationships.
• Setup your singleton module at the app.js file.
• Get the model classes from the singleton module do not use require on your model files, load the models from the singleton instead.

The longer story

Here is a more detailed description of this solution with the corresponding source code:

http://jeydotc.github.io/blog/2012/10/30/EXPRESS-WITH-SEQUELIZE.html

EDIT: This is a very old answer! (read down for info)

It's old and limited in many ways!

• First, as @jinglesthula mentioned in comments (and I experienced it too) - there are problems with requiring those files. It's because require doesn't work the same way as readdirSync!

• Second - you are very limited in relations - the code doesn't provide options to those associations so you are UNABLE to create belongsToMany as it needs through property. You can make the most basic assocs.

• Third - you are very limited in model relations! If you read closely the code, you will see that relations is an Object instead of an Array, so if you want to make more than one associations of the same type (like having two times belongsTo) - you cannot!

• Fourth - You don't need that singleton thingy. Every module in nodejs is singleton by itself, so all this makes is pretty complex for no reason.

You should see Farm's answer! (The link to the article is broken, but I'll fix it with this official sample from sequelize: https://github.com/sequelize/express-example/blob/master/models/index.js - you can browse the whole project to get an idea of what's going on).

p.s. I'm editing this post as it's so upvoted that people won't even see any new answers (as I did).

Edit: Just changed the link to a copy of the same post, but in a Github Page

SequelizeJS has a article on their website which solves this problem.

Link is broken, but you can find the working sample project here and browse it. See edited answer above to see why this is a better solution.

Extract from article:

• models/index.js

  The idea of this file is to configure a connection to the database and to collect all Model definitions. Once everything is in place, we will call the method associated on each of the Models. This method can be used to associate the Model with others.

        var fs        = require('fs')
          , path      = require('path')
          , Sequelize = require('sequelize')
          , lodash    = require('lodash')
          , sequelize = new Sequelize('sequelize_test', 'root', null)
          , db        = {} 
  
        fs.readdirSync(__dirname)
          .filter(function(file) {
            return (file.indexOf('.') !== 0) && (file !== 'index.js')
          })
          .forEach(function(file) {
            var model = sequelize.import(path.join(__dirname, file))
            db[model.name] = model
          })
  
        Object.keys(db).forEach(function(modelName) {
          if (db[modelName].options.hasOwnProperty('associate')) {
            db[modelName].options.associate(db)
          }
        })
  
        module.exports = lodash.extend({
          sequelize: sequelize,
          Sequelize: Sequelize
        }, db)
  

I've create a package sequelize-connect to help people deal with this issue. It follows the Sequelize suggested convention here: http://sequelize.readthedocs.org/en/1.7.0/articles/express/

Additionally it also functions a bit more like Mongoose in terms of its interface. It allows you to specify a set of locations where your models are located and also allows you to define a custom matching function to match your model files.

The usage is basically like this:

var orm = require('sequelize-connect');

orm.discover = ["/my/model/path/1", "/path/to/models/2"];      // 1 to n paths can be specified here
orm.connect(db, user, passwd, options);                        // initialize the sequelize connection and models

Then you can access the models and sequelize like so:

var orm       = require('sequelize-connect');
var sequelize = orm.sequelize;
var Sequelize = orm.Sequelize;
var models    = orm.models;
var User      = models.User;

Hopefully this helps someone out.

I started using Sequelize in Express.js app. Soon enough ran into issues of the nature you're describing. Maybe I did not quite understand Sequelize, but to me doing things more than just selecting from one table wasn't really convenient. And where ordinarily you would use select from two or more tables, or a union in pure SQL, you would have to run separate queries, and with the async nature of Node it's just added complexity.

Therefore I moved away from using Sequelize. Moreover I am switching from using ANY data fetching from DB in the models. In my opinion it is better to abstract getting data completely. And reasons are - imagine that you don't just use MySQL (in my case, I use MySQL and MongoDB side by side), but you can get your data from any data provider and any transport method, e.g. SQL, no-SQL, filesystem, external API, FTP, SSH etc. If you tried to do all of it in the models, you would eventually create complex and hard to understand code that would be hard to upgrade and debug.

Now what you want to do is to have models get data from a layer that knows where and how to get it, but your models only use API methods, e.g. fetch, save, delete etc. And inside this layer you have specific implementations for specific data providers. E.g. you can request certain data from a PHP file on a local machine or from Facebook API or from Amazon AWS or from remote HTML document, etc.

PS some of these ideas were borrowed from Architect by Cloud9: http://events.yandex.ru/talks/300/

I set it up as Farm and the documentation describe.

But I was having the additonal problem that in my instance methods and class methods that I would attach to the models in each function I would need to require the index file to get a hold of other database objects.

Solved it by making them accessible to all models.

var Config = require('../config/config');

 var fs = require('fs');
var path = require('path');
var Sequelize = require('sequelize');
var _ = require('lodash');
var sequelize;
var db = {};

var dbName, dbUsername, dbPassword, dbPort, dbHost;
// set above vars

var sequelize = new Sequelize(dbName, dbUsername, dbPassword, {
dialect: 'postgres', protocol: 'postgres', port: dbPort, logging: false, host: dbHost,
  define: {
    classMethods: {
        db: function () {
                    return db;
        },
        Sequelize: function () {
                    return Sequelize;
        }

    }
  }
});


fs.readdirSync(__dirname).filter(function(file) {
   return (file.indexOf('.') !== 0) && (file !== 'index.js');
}).forEach(function(file) {
  var model = sequelize.import(path.join(__dirname, file));
  db[model.name] = model;
});

Object.keys(db).forEach(function(modelName) {
  if ('associate' in db[modelName]) {
      db[modelName].associate(db);
  }
});

module.exports = _.extend({
  sequelize: sequelize,
  Sequelize: Sequelize
}, db);

And in the model file

var classMethods = {
  createFromParams: function (userParams) {
    var user = this.build(userParams);

    return this.db().PromoCode.find({where: {name: user.promoCode}}).then(function (code) {
        user.credits += code.credits;
                return user.save();
    });
  }

};

module.exports = function(sequelize, DataTypes) {
  return sequelize.define("User", {
  userId: DataTypes.STRING,
}, {  tableName: 'users',
    classMethods: classMethods
 });
};

I only did this for the class methods but you could also do the same thing for instance methods.

I am following the official guide: http://sequelizejs.com/heroku, which has a models folder, set up each module in separate files, and have a index file to import them and set the relationship among them.

Sample model sequelize

'use strict';
const getRole   = require('../helpers/getRole')
const library   = require('../helpers/library')
const Op        = require('sequelize').Op

module.exports = (sequelize, DataTypes) => {
  var User = sequelize.define('User', {
    AdminId: DataTypes.INTEGER,
    name: {
      type: DataTypes.STRING,
      validate: {
        notEmpty: {
          args: true,
          msg: 'Name must be filled !!'
        },
      }
    },
    email: {
      type: DataTypes.STRING,
      validate: {
        notEmpty: {
          args: true,
          msg: 'Email must be filled !!'
        },
        isUnique: function(value, next) {
          User.findAll({
            where:{
              email: value,
              id: { [Op.ne]: this.id, }
            }
          })
          .then(function(user) {
            if (user.length == 0) {
              next()
            } else {
              next('Email already used !!')
            }
          })
          .catch(function(err) {
            next(err)
          })
        }
      }
    },
    password: {
      type: DataTypes.STRING,
      validate: {
        notEmpty: {
          args: true,
          msg: 'Password must be filled !!'
        },
        len: {
          args: [6, 255],
          msg: 'Password at least 6 characters !!'
        }
      }
    },
    role: {
      type: DataTypes.INTEGER,
      validate: {
        customValidation: function(value, next) {
          if (value == '') {
            next('Please choose a role !!')
          } else {
            next()
          }
        }
      }
    },
    gender: {
      type: DataTypes.INTEGER,
      validate: {
        notEmpty: {
          args: true,
          msg: 'Gender must be filled !!'
        },
      }
    },
    handphone: {
      type: DataTypes.STRING,
      validate: {
        notEmpty: {
          args: true,
          msg: 'Mobile no. must be filled !!'
        },
      }
    },
    address: DataTypes.TEXT,
    photo: DataTypes.STRING,
    reset_token: DataTypes.STRING,
    reset_expired: DataTypes.DATE,
    status: DataTypes.INTEGER
  }, {
    hooks: {
      beforeCreate: (user, options) => {
        user.password = library.encrypt(user.password)
      },
      beforeUpdate: (user, options) => {
        user.password = library.encrypt(user.password)
      }
    }
  });

  User.prototype.check_password = function (userPassword, callback) {
    if (library.comparePassword(userPassword, this.password)) {
      callback(true)
    }else{
      callback(false)
    }
  }

  User.prototype.getRole = function() {
    return getRole(this.role)
  }

  User.associate = function(models) {
    User.hasMany(models.Request)
  }

  return User;
};

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