如何在 sequelize node.js 中的现有模型中添加多对多关联？

Question

I want to add many to many association in my node app using sequelize. I am new in sequelize ORM.

I have a eixsting model user.js. I want to create new model project and add want to many to many association

For that I run sequelize create table and migration created Now in association part what I do that many to many association created

I find multiple these to do that

Project.belongsToMany(User, {through: 'UserProject'});

But Where I write User.belongsToMany(Project, {through: 'UserProject'}); because user model is alreaady existing

Second thing I want to know either UserProject automatically created by this or need to manually create it?

Answer 1

It is a good practice to use sequelize-cli and use the sequelize init tool, which creates a file which gathers together all your models and creates associations between them. The association is done via class method associate , which should be implemented in all of your models (having association to other ones).

This method could look like this (in case of User model):

classMethods: {
    associate: function(models){
        this.belongsToMany(models.Project, { through: 'UserProject' });
    }
}

And equivalent in the Project model:

classMethods: {
    associate: function(models){
        this.belongsToMany(models.User, { through: 'UserProject' });
    }
}

If you do not want to add any other extra fields to the UserProject table, it will be created automatically with fields UserId and ProjectId (if you use the sequelize.sync() method - otherwise you have to create the table in migration file). In other case, when you want to add other fields, you would have to create such a model itself.