Unpermitted parameter for join table via multiple select in Rails

Question

I'm running into an error when nesting parameters in Rails 5: Unpermitted parameter: specialties

I have an Expertise model:

class Expertise < ApplicationRecord
    has_many :buckets, through: :specialties
    has_many :specialties   
end

A Bucket model:

class Bucket < ApplicationRecord
    has_many :expertises, through: :specialties
    has_many :specialties
end

And a Specialty model:

class Specialty < ApplicationRecord
    belongs_to :expertise
    belongs_to :bucket
end

I'm trying to allow the User to edit his or her Expertises and adjust the Specialties associated with them. The @buckets are passed in from the controller, and the form currently looks like this:

<%= form_for(expertise) do |f| %>
    <%= f.fields_for :specialties do |s| %>
        <%= s.collection_select :bucket_ids, @buckets, :id, :name, {}, { multiple: true, class: "input" } %>
    <% end %>
<% end %>

I based the form on this answer.

Here's the relevant snippet from the ExpertisesController:

def expertise_params
    params.require(:expertise).permit(:user_id, :name, :rating, :description, specialties_attributes: [:id, :expertise_id, :bucket_id, :_destroy, bucket_ids: []])
end

And here are the parameters that are being passed in:

Parameters: {"expertise"=>{"specialties"=>{"bucket_ids"=>["", "1"]}, "description"=>""}, "id"=>"97"}

Specialties should be an array, right? I'm not sure how to do that.

The aim is to easily enable the User to select from the available Buckets (@buckets) to toggle his or her Expertise Specialties on or off. So let's say there are 5 Buckets available, the User would only be able to toggle on/off 5 possible Specialties for that Expertise.

Answer 1

Unpermitted parameter: specialties

You didn't set up accept_nested_attributes_for which spits out with that error

class Expertise < ApplicationRecord
  has_many :specialties
  has_many :buckets, through: :specialties
  accepts_nested_attributes_for :specialties
end

When I try that, the nested fields_for form doesn't return any specialties and so the HTML element is empty. Then, when I try to use @expertise.specialties.build, I get undefined method bucket_ids for Specialty because bucket_ids isn't actually an attribute, but bucket_id is. Worth keeping in mind that the User needs to be able to toggle multiple Specialties, each of which is tied to a Bucket (via a bucket_id), and from what I've ready I'm supposed to use bucket_ids (the plural) there

You don't need to have plural form(_ids) just because to accept multiple values. Just keep bucket_id to accept multiple values. And don't forget to build the associated model in the controller

def new @expertise = Expertise.new @expertise.specialties.build end Change bucket_ids to bucket_id in the form

<%= s.collection_select :bucket_id, @buckets, :id, :name, {}, { multiple: true, class: "input" } %>

And finally, expertise_params should be

def expertise_params
  params.require(:expertise).permit(:user_id, :name, :rating, :description, specialties_attributes: [:id, :expertise_id, :_destroy, bucket_id: []])
end

Update:

Ok after some research, it looks like it should be bucket_ids, but the bucket_ids should be allowed as attribute for expertise. Check this post and tweak your form and expertise_params accordingly. You won't be needing accept_nested_attributes_for too!

Answer 2

The situation: Expertise has_many Buckets through Specialties and you want to update some bucket status of a specific expertise. So you can do this:

class ExpertisesController < ApplicationController
  def your_action
    @expertise = Expertise.find params[:id]
    bucket_ids = params[:expertise][:specialties][:bucket_ids]
    @expertise.specialties.where(id: bucket_ids).update(status: :on)
  end
end