How to update a ManyToMany relationship in Objection JS? - objection.js

Question

I am learning Objection JS. I have a manyToMany relationship on an accounts and roles table that are related through an accounts_roles table. I was wondering if there was a way to update account roles on the account model by doing something like:
AccountOne.addRoles([roleId])
AccountOne.removeRoles([roleId])
AccountOne.updateRoles([roleId])
AccountOne.deleteRoles([roleId])
I searched online and went through the official objection documentation. So far I can do a GraphInsert, on my account model with a role object "x", and that creates a new role "x" with a relationship correctly defined in accounts_roles. But that always creates a new role. I would like to add and remove relationships between existing accounts and roles. Any help would be much appreciated.

Answer 1

You can use relate and unrelate to connect two rows together in a many-to-many relationship. Obviously, for this to work, you have to have your Models' relationMappings set up correctly. I have put a pair of example models too. It's critical that you match your key of your relationMappings to what you put in your $relatedQuery method to call relate/unrelate on.
Example Models
//Person and Movie Models
const { Model } = require('objection');
class Person extends Model {
static tableName = 'persons';
static get relationMappings() {
return {
movies: {
relation: Model.ManyToManyRelation,
modelClass: Movie,
join: {
from: 'persons.id',
through: {
from: 'persons_movies.person_id',
to: 'persons_movies.movie_id'
},
to: 'movies.id'
}
}
};
}
}
class Movie extends Model {
static tableName = 'movies';
static get relationMappings() {
return {
persons: {
relation: Model.ManyToManyRelation,
modelClass: Person,
join: {
from: 'movies.id',
through: {
from: 'persons_movies.movie_id',
to: 'persons_movies.person_id'
},
to: 'persons.id'
}
}
};
}
}
Relate Example
In the case of a many-to-many relation, creates a join row to the join table.
const person = await Person
.query()
.findById(123);
const numRelatedRows = await person
.$relatedQuery('movies')
.relate(50);
// movie with ID 50 is now related to person with ID 123
// this happened by creating a new row in the linking table for Movies <--> Person
Unrelate Example
For ManyToMany relations this deletes the join row from the join table.
const person = await Person
.query()
.findById(123)
const numUnrelatedRows = await person
.$relatedQuery('movies')
.unrelate()
.where('id', 50);
// movie with ID 50 is now unrelated to person with ID 123
// this happened by delete an existing row in the linking table for Movies <--> Person