Sequelize define association on Array - express

Question

I have two models in Sequelize as below:
export const User = db.define('user', {
id: {
type: Sequelize.UUID,
primaryKey: true,
},
});
export const Class = db.define('class', {
id: {
type: Sequelize.UUID,
primaryKey: true,
},
students: Sequelize.ARRAY({
type: Sequelize.UUID,
references: { model: 'users', key: 'id' },
})
});
How can I define an association between my Class model and the user model?
I have tried the below but it gives me an error.
Class.hasMany(User, { foreignKey: 'students' });
User.belongsTo(Class);
DatabaseError [SequelizeDatabaseError]: column "class_id" does not exist

Answer 1

I think you are missing the syntax
students: Sequelize.ARRAY({
type: Sequelize.UUID,
references: { model: 'users', key: 'id' }, // this has no effect
})
Should be
students: {
type: DataTypes.ARRAY({ type: DataTypes.UUID }),
references: { model: 'users', key: 'id' }
}
This won't work either, because the data type of students (ARRAY) and id (UUID) of User does not match.
Also, with these associations, you are adding two columns on User referencing id of Class but you only need one
Class.hasMany(User, { foreignKey: 'students' }); //will add students attribute to User
User.belongsTo(Class); //will add classId attribute to User
if you want to name the foreign key column passe the same name to both associations, by default Sequelize will add classId, however if you configured underscored: true on the models it will be class_id
Here is a working solution
const User = sequelize.define('user', {
id: { type: DataTypes.UUID, primaryKey: true },
});
const Class = sequelize.define('class', {
id: { type: DataTypes.UUID, primaryKey: true },
students: DataTypes.ARRAY({ type: DataTypes.UUID }),
});
Class.hasMany(User, { foreignKey: 'class_id' });
User.belongsTo(Class, { foreignKey: 'class_id' });