ruby-on-rails – Many to Many JSON POST – Rails 5 – Only API

Question:

Hi, I'm developing an Engine on Rails 5 which will be just a blog API. It will be a simple system. Post has lots of Passions and Passions has lots of Posts. I made the relationship N <->

The problem is that when I send the post's JSON with the IDs of the Passions I want to associate with it, I can't save them.

Post.rb

module Feed
  class Post < ApplicationRecord
    has_many :post_passions,  dependent: :destroy 
    has_many :passions, :through => :post_passions
  end
end

Passion.rb

module Feed
  class Passion < ApplicationRecord
    has_many :post_passions
    has_many :post, :through => :post_passions
  end
end

PostPassion.rb (Join Table)

module Feed
  class PostPassion < ApplicationRecord
     belongs_to :passion
     belongs_to :post
  end
end

My goal is through a POST request in the api '/feed/posts' to be able to create a post specifying several Passions. The JSON I am sending is as follows.

{
  "title": "Titulo da postagem",
  "description":"Decrição do post",
  "passion_ids":[1,2]
}

Sending this post when looking at the rails log that receives the request the 'passion_ids' attribute is not sending inside the post so I can allow it.

Log when sending the request

Started POST "/feed/posts" for 127.0.0.1 at 2017-03-29 08:20:00 -0300
Processing by Feed::PostsController#create as */*
Parameters: {"title"=>"Titulo da postagem", "description"=>"Decrição do post", "passion_ids"=>[1, 2], "post"=>{"title"=>"Titulo da postagem", "description"=>"Decrição do post"}}

As the 'passion_ids' is not received inside Post the permit below does not work.

params.require(:post).permit(:title,
                             :passion_ids,
                             :description)

I have a system that works that way but it's on rails 4.2 and entries are made by forms and not by REST.

Answer:

I think there are some questions there. First, I think your JSON request should have a root, in this case:

{
    "post": {
        "title": "Titulo da postagem",
        "description":"Decrição do post",
        "passion_ids":[1,2]
    }
}

Second, if you want to pass an array as an attribute, you must allow it differently, like this:

params.require(:post).permit(:title,
                             :description,
                             passion_ids: [])

So rails knows you're going to pass an array. Hope this helps.