Adding Many to Many Data Sequelize - mysql

Question

Case: I have 2 tables; one for users and one for assignments. A user can have many assignments and an assignment can be assigned to many users. I have a form in the frontend to add assignment and assign the users for the assignment and I am really confused on how to add the assignment and user to the joint table 'user_assignment'. Can someone point where I am having the mistake? Also for this, I refer to Advanced M:N Associations.
I also attach my code for the Users and Assignments model, and other relevant code parts.
user.model.js
module.exports = (sequelize, DataTypes) => {
const User = sequelize.define("users", {
firstName: {
type: DataTypes.STRING,
allowNull: false,
},
lastName: {
type: DataTypes.STRING,
allowNull: false,
},
department: {
type: DataTypes.STRING,
allowNull: false,
},
email: {
type: DataTypes.STRING,
allowNull: false,
},
password: {
type: DataTypes.STRING,
allowNull: false,
},
role: {
type: DataTypes.STRING,
allowNull: false,
},
});
return User;
};
assignment.model.js
module.exports = (sequelize, DataTypes) => {
const Assignment = sequelize.define("assignments", {
title: {
type: DataTypes.STRING,
allowNull: false,
},
department: {
type: DataTypes.STRING,
allowNull: false,
},
urgency: {
type: DataTypes.STRING,
allowNull: false,
},
assignmentBegin: {
type: DataTypes.STRING,
allowNull: false,
},
assignmentEnd: {
type: DataTypes.STRING,
allowNull: false,
},
description: {
type: DataTypes.STRING,
allowNull: false,
},
});
return Assignment;
};
database/index.js
...
db.user = require("../models/user.model")(sequelize, Sequelize);
db.assignment = require("../models/assignment.model")(sequelize, Sequelize);
...
db.user.belongsToMany(db.assignment, {
through: "user_assignment",
as: "assignments",
foreignKey: "userId",
});
db.assignment.belongsToMany(db.user, {
through: "user_assignment",
as: "users",
foreginKey: "assignmentId",
});
...
assignment.controller.js
const db = require("../database");
const Assignment = db.assignment;
const User = db.user;
exports.create = async (req, res) => {
const {
participant,
title,
department,
urgency,
assignmentBegin,
assignmentEnd,
description,
} = req.body;
await Assignment.create({
title: title,
department: department,
urgency: urgency,
assignmentBegin: assignmentBegin,
assignmentEnd: assignmentEnd,
description: description
}).then(async result => {
for (i = 0; i < participant.length; i++) {
const user = await User.findByPk(participant[i])
// console.log(user.id)
await UserController.addAssignment(user.id, result.id);
// await UserController.addAssignment(2, 1)
}
}).catch(err => {
res.json({ message: "ERROR WHILE CREATING ASSIGNMENT!" });
console.log(">>> ERROR WHILE CREATING ASSIGNMENT!")
});
}
Any pointers on what I should do would be great!

Answer 1

I'd recommend you define the model associations inside each of the model files. Also you should hash/encrypt your passwords before saving them to the DB, you can use the .comparePassword() function outside of the model in a controller when logging in etc.
models/User.js
const Promise = require('bluebird')
const bcrypt = Promise.promisifyAll(require('bcrypt'))
function hashPassword (user) {
const SALT_FACTOR = 12
if (!user.changed('password')) {
return;
} else {
user.setDataValue('password', bcrypt.hashSync(user.password, SALT_FACTOR))
}
}
module.exports = User = (sequelize, DataTypes) => {
const User = sequelize.define('User', {
firstName: {
type: DataTypes.STRING,
allowNull: false,
},
lastName: {
type: DataTypes.STRING,
allowNull: false,
},
department: {
type: DataTypes.STRING,
allowNull: false,
},
email: {
type: DataTypes.STRING,
allowNull: false,
},
password: {
type: DataTypes.STRING,
allowNull: false,
},
role: {
type: DataTypes.STRING,
allowNull: false,
},
{
hooks: {
beforeCreate: hashPassword,
beforeUpdate: hashPassword
}
})
User.associate = models => {
User."Association type here"(models."Model to associate",
{Options (For many to many add your "through" table here)}
)
// Example:
User.belongsToMany(models.Assignment, {
through: "UserAssignment"
})
}
User.prototype.comparePassword = function (password) {
return bcrypt.compareSync(password, this.password)
}
return User
}
And in the associated Model (models/Assignment.js):
module.exports = Assignment = (sequelize, DataTypes) => {
const Assignment = sequelize.define('Assignment', {
title: {
type: DataTypes.STRING,
allowNull: false,
},
department: {
type: DataTypes.STRING,
allowNull: false,
},
urgency: {
type: DataTypes.STRING,
allowNull: false,
},
assignmentBegin: {
type: DataTypes.STRING,
allowNull: false,
},
assignmentEnd: {
type: DataTypes.STRING,
allowNull: false,
},
description: {
type: DataTypes.STRING,
allowNull: false,
},
},
{
timestamps: false
})
Assignment.associate = models => {
Assignment.belongsToMany(models.User, {
through: "UserAssignment"
})
}
return Role
}
The joint table (models/UserAssignment.js):
module.exports = UserAssignment = (sequelize, DataTypes) => {
const UserAssignment = sequelize.define('UserAssignment', {
id: {
type: DataTypes.UUID,
defaultValue: DataTypes.UUIDV4,
primaryKey: true
}
},
{
timestamps: false
})
return UserAssignment
}
And finally my index.js file (models/index.js), it programatically adds the models to the DB:
'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 = require(path.join(__dirname, file))(sequelize, Sequelize.DataTypes);
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;
As an extra note, you can shorten down your createAssignment function in your controller by doing this instead:
const {
participant,
title,
department,
urgency,
assignmentBegin,
assignmentEnd,
description,
} = req.body;
await Assignment.create({
title: title,
department: department,
urgency: urgency,
assignmentBegin: assignmentBegin,
assignmentEnd: assignmentEnd,
description: description
}).then(async result => {
result.addUsers(participant)
}).catch(err => {
res.json({ message: "ERROR WHILE CREATING ASSIGNMENT!" });
console.log(">>> ERROR WHILE CREATING ASSIGNMENT!")
});
Hope this helps, if not lmk ill try to help some more.