Sequelize with express

Question

Sequelize with express

I'm following a tutorial which uses sequelize with an express project. Here's the user.js model:

// in models/User.js
module.exports = function(sequelize, DataTypes) {
  return sequelize.define('User', {
    first_name: DataTypes.STRING,
    last_name: DataTypes.STRING,
  }, {
    instanceMethods: {
      countTasks: function() {
        // how to implement this method ?
      }
    }
  });
};

Then he uses User in various of ways, for example:

var user = User.build({ first_name: 'John', last_name: 'Doe' });

I understand the code in general, but I don't understand completely why module.exports gets a function with two parameters (sequelize, DataTypes). I haven't seen it initialized anywhere in the code. How is it working then?

javascript
node.js
express
sequelize.js

Answer 1

If you are following this guide you will see in models/index.js that all model definitions are looped through and passed to seqelize.import().

You will find that this line of code within sequelize.import calls the model's module function and passes a reference to sequelize and DataTypes to the model.

In the tutorial you referenced, the author uses a similar method within models/index.js

> Edit (7/14/2015)

Since the link does not work and I could not find it on their current site, I copied the code from their site using The Wayback Machine. I also updated the second link to point to the 2.0 docs instead of master.

models/index.js

"use strict";

var fs        = require("fs");
var path      = require("path");
var Sequelize = require("sequelize");
var env       = process.env.NODE_ENV || "development";
var config    = require(__dirname + '/../config/config.json')[env];
var sequelize = new Sequelize(config.database, config.username, config.password, config);
var 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 ("associate" in db[modelName]) {
    db[modelName].associate(db);
  }
});

db.sequelize = sequelize;
db.Sequelize = Sequelize;