Rails has_many :through creating new and linking in controller

Question

I have a website I am making that tracks a users companies through employments. I need to know what I am doing wrong because when I make a new user company the user doesn't know about it.

companies_controller.rb

class CompaniesController < ApplicationController
  # GET /companies
  # GET /companies.json
  def index
    @companies = current_user.companies
    respond_to do |format|
      format.html # index.html.erb
      format.json { render json: @companies }
    end
  end

  # GET /companies/1
  # GET /companies/1.json
  def show
    @company = Company.find(params[:id])

    respond_to do |format|
      format.html # show.html.erb
      format.json { render json: @company }
    end
  end

  # GET /companies/new
  # GET /companies/new.json
  def new
    @company = Company.new

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @company }
    end
  end

  # GET /companies/1/edit
  def edit
    @company = Company.find(params[:id])
  end

  # POST /companies
  # POST /companies.json
  def create
    @company = Company.new(params[:company])

    current_user.employments.create!(company_id: @company.id)

    respond_to do |format|
      if @company.save
        format.html { redirect_to @company, notice: 'Company was successfully created.' }
        format.json { render json: @company, status: :created, location: @company }
      else
        format.html { render action: "new" }
        format.json { render json: @company.errors, status: :unprocessable_entity }
      end
    end
  end

  # PUT /companies/1
  # PUT /companies/1.json
  def update
    @company = Company.find(params[:id])

    respond_to do |format|
      if @company.update_attributes(params[:company])
        format.html { redirect_to @company, notice: 'Company was successfully updated.' }
        format.json { head :no_content }
      else
        format.html { render action: "edit" }
        format.json { render json: @company.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /companies/1
  # DELETE /companies/1.json
  def destroy
    @company = Company.find(params[:id])
    @company.destroy

    respond_to do |format|
      format.html { redirect_to companies_url }
      format.json { head :no_content }
    end
  end
end

Answer 1

The problem is within your create action, specifically the line

current_user.employments.create!(company_id: @company.id)

this is executed before the company record is saved so it doesn't have an id (== nil). Just move that line after

if @company.save

and it should attach it to the current_user via the :through relationship.