Sequelize Create/Import Dynamically Generated Models

Question

I have a Sequelize migration script (built off sequelize-cli's initial migration script generated from running sequelize-cli) that dynamically creates tables based on a list of ~100 hardcoded table names imported from a .json file. Thus, it will be tedious and error-prone to hardcode the Sequelize model definitions by hand.

Question: How can we dynamically generate the Sequelize models by reading from the same .json file? I am mainly stuck how we should return multiple Sequelize models using module.exports, based on the model definition file auto-generated from running sequelize-cli model:generate --name Base .... There appears to be a special script models/index.js for reading the model definition file models/base.js.

models/base.js

'use strict';
const universe = require('../config/universe.json');

const generateModel = (sequelize, DataTypes, tableName) => {
    const schema = {
        name: DataTypes.STRING,
        power: DataTypes.DOUBLE,
    };
    const options = {
        timestamps: false,
    };
    const Model = sequelize.define(tableName, schema, options);
    Model.associate = function(models) {
        // associations can be defined here
    }

    return Model;
}

module.exports = (sequelize, DataTypes) => {
    models = []
    for (let planet in universe) {
        for (const species of universe[planet]) {
            models.push(generateModel(species));
        }
    }

  return models;
};

app.js

Attempting to load the dynamically created model Human

const Human = require('./models').base.human;

Human.create({name: 'Tom', power: 1.23});

config/universe.json

Example hardcoded data file

{
    "earth": [
        'human', 
        'cat', 
        'dog'
    ]
}

models/index.js

This file is auto-generated after running sequelize-cli init

'use strict';

const fs = require('fs');
const path = require('path');
const Sequelize = require('sequelize');
const basename = path.basename(__filename);
const env = process.env.NODE_ENV || 'development';
const config = require(__dirname + '/../config/config.json')[env];
const db = {};

let sequelize;
if (config.use_env_variable) {
  sequelize = new Sequelize(process.env[config.use_env_variable], config);
} else {
  sequelize = new Sequelize(config.database, config.username, config.password, config);
}

fs
  .readdirSync(__dirname)
  .filter(file => {
    return (file.indexOf('.') !== 0) && (file !== basename) && (file.slice(-3) === '.js');
  })
  .forEach(file => {
    const model = sequelize['import'](path.join(__dirname, file));
    db[model.name] = model;
  });

Object.keys(db).forEach(modelName => {
  if (db[modelName].associate) {
    db[modelName].associate(db);
  }
});

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

module.exports = db;

Sequelize Create/Import Dynamically Generated Models

0 Answers0