Adding single item to rails has_many :through - ruby-on-rails

Question

I have a has_many :thorugh relationship between customers and software products they own.
# company.rb
class Company < ActiveRecord::Base
has_many :company_sources
has_many :sources, :through => :company_sources
end
# source.rb
class Source < ActiveRecord::Base
has_many :company_sources
has_many :companies, :through => :company_sources
end
# company_source.rb
class CompanySource < ActiveRecord::Base
belongs_to :company
belongs_to :source
end
The controllers are the default rails g scaffold <name> files
I need a selection form on the company edit page that will allow the addition of a single source to the company_source table.
The closest I can get is using the selection form helper, however that will overwrite the previous addition when I go to add a new item.
I've been playing with this for quite a few hours now and I can't seem to get the form/routes/controller right.
This is the form I'm playing with at the time of writing
<table>
<% #company.sources.each do |source| %>
<tr><%= source.name %></tr>
<% end %>
<tr>
<%= form_for #company do |f| %>
<td>
<%= select("source", "id", Source.all.collect {|p| [ p.name, p.id ]}, { include_blank: true })%>
</td>
<td>
<%= f.submit "Add Source" %>
</td>
<% end %>
</tr>
</table>
Full controller (again, at time of writing)
class CompaniesController < ApplicationController
before_action :set_company, only: [:show, :edit, :update, :destroy]
# GET /companies
# GET /companies.json
def index
#companies = Company.all
end
# GET /companies/1
# GET /companies/1.json
def show
end
# GET /companies/new
def new
#company = Company.new
end
# GET /companies/1/edit
def edit
end
# POST /companies
# POST /companies.json
def create
#company = Company.new(company_params)
respond_to do |format|
if #company.save
format.html { redirect_to #company, notice: 'Company was successfully created.' }
format.json { render :show, status: :created, location: #company }
else
format.html { render :new }
format.json { render json: #company.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /companies/1
# PATCH/PUT /companies/1.json
def update
respond_to do |format|
if #company.update(company_params)
format.html { redirect_to #company, notice: 'Company was successfully updated.' }
format.json { render :show, status: :ok, location: #company }
else
format.html { render :edit }
format.json { render json: #company.errors, status: :unprocessable_entity }
end
if (params[:source_id])
#company.source << Source.find(params[:source_id])
end
end
end
# DELETE /companies/1
# DELETE /companies/1.json
def destroy
#company.destroy
respond_to do |format|
format.html { redirect_to companies_url, notice: 'Company was successfully destroyed.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_company
#company = Company.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def company_params
params.require(:company).permit(:name, :description, :source_id)
end
end

Answer 1

In the update action, I propose not doing #company.update, and instead doing:
company_source = CompanySource.create!(company: #company, source: Source.find(source_id)
(Warning: There might be errors in the code, which you should be able to correct fairly easily)
So, the update action would look like:
def update
respond_to do |format|
company_source = CompanySource.new(company: #company, source_id: params[:source_id])
if company_source.save
format.html { redirect_to #company, notice: 'Company was successfully updated.' }
format.json { render :show, status: :ok, location: #company }
else
format.html { render :edit }
format.json { render json: company_source.errors, status: :unprocessable_entity }
end
end
end
Although this shifts the perspective to that of the CompanySource despite being inside the CompaniesController, what you are really wanting to do is create a new CompanySource. I think this is the most straightforward way of looking at it.
This will ensure correct updates of the Compnay-Source relationship.