ActiveModelSerializer / EmberJS. Many-to-many relationship. Do I need a join model in Rails back-end?

Question

Posts have many tags and Tags have many posts. In Rails, I'll typically need to make a Post_Tags model and migration to join the two models.

Using an EmberJS front-end, I'm not sure how to do the serializers and if a Post_Tags model is necessary.

The models in Ember:

// app/models/post.js
export default DS.Model.extend({
  heading: DS.attr('string'),
  content: DS.attr(''),
  fullImageUrl: DS.string('author'),
  thumbnailUrl: DS.attr('string'),
  pageId: DS.belongsTo('page'),
  tagIds: DS.hasMany('tag')
});

// app/models/tag.js
export default DS.Model.extend({
  name: DS.attr('string'),
  postIds: DS.hasMany('post')
});

The expected JSON with an ActiveModelAdapter should be:

"posts": [{
  "id": 1,
  "heading": "foo",
  "content": ,
  "full_image_url": "foo",
  "thumbnail_url": "foo",
  "page_id": <page id>,
  "tag_ids": [<tag ids>] }],
"tags": [{
  "id": 1,
  "name": "foo",
  "post_ids": [<post ids>] 
}]

Do I still need a Post_Tags model that belongs_to :post and belongs_to :tag? Do I need a Post_Tags serializer? Or will just saying has_many :posts in the Tag serializer and vice versa be enough?

GJK GJK · Accepted Answer · 2014-09-07T00:47:39

I have never used ActiveModel, so speaking solely from the Ember-Data point of view, you do not need a join model. Using the models you've posted, Ember-Data should be able to format the JSON the way you want. You can see some example on the ActiveModelSerializer API page.

EDIT: From the Rails side, it doesn't look like you need a join model. As I said, I've never used ActiveModel, but this article seems to say that a join model would be unnecessary in this situation.

ActiveModelSerializer / EmberJS. Many-to-many relationship. Do I need a join model in Rails back-end?

1 Answers