Save model with hasMany

Imagine a typical relationship between a User model and a Course model. A user can have many courses and a course can have many users. This is a normal many to many relationship. However, I also need some columns on the join table. Imagine that a discount associated with the user <-> course association.

I’m writing a web api, and I have an endpoint that accepts something like this JSON (POST /users/123):

{
  "firstName": "Miguel",
  "lastName": "Andrade",
  "courses": [
    {
      "course_id": 1,
      "discount": 0.23
    },
    {
      "course_id": 4,
      "discount": 0.33
    }
  ]
}

This is what the web app sends after the user submits a form where he/she can choose courses and their respective discounts.

The question is, what is the appropriate way to save this JSON in Bookshelf? I don’t mind transforming this many-to-many in two one-to-many. I could create a Model called CourseSubscription which could hold the relationships and the additional discount. Either way, I’d like to know how to best tackle this problem.

[rhys-vdw]

@miguelcobain See #831. Something like this, perhaps:

// CURRENTLY NOT SUPPORTED
Person.forge({
  name: 'miguel',
  friends: [{ name: 'rhys' }],
  skills: [{ skill: 'JavaScript' }, { skill: 'css' }]
}).save({ withRelated: ['friends', 'skills'] }).then(person =>

Could take withRelated: true to accept all. There’s a few things that need to happen before then though.

[miguelcobain]

@rhys-vdw Something came up that I think is somewhat related with this issue. So I thought to include it here for anyone that may need it.

The problem is related with orphans. Example:

• I save an object like:

{
  "firstName": "Miguel",
  "lastName": "Andrade",
  "courses": [
    {
      "course_id": 1,
      "discount": 0.23
    },
    {
      "course_id": 4,
      "discount": 0.33
    }
  ]
}

Both inner objects got ids 1 and 2 respectively.

• Then, the user removes one of the inner models and clicks save, so I’m now saving:

{
  "firstName": "Miguel",
  "lastName": "Andrade",
  "courses": [
    {
      "id": 1,
      "course_id": 1,
      "discount": 0.23
    }
  ]
}

This should issues an update, but it is intended to also generate a DELETE for the now orphan courses id 2. This is a similar feature as JPA orphanRemoval (more info).

How could I get a similar behavior? My first instinct is to use underlying knex to DELETE courses NOT IN the list of ids I’m saving. A code example would help a lot.

Also, I can create a separate issue for orphanRemoval, if you feel that it is within the scope of this project, and not just a help request. 😃

Thanks.