Rails console output from 'Issue Generating Objects Indirectly from Patch Controller Method'

print.rb

class Print < ApplicationRecord
  has_many :project_print
  has_many :projects, :through => :project_print

  attr_accessor :title, :left_photo_id, :right_photo_id

end

project.rb

class Project < ApplicationRecord
  has_many :project_print
  has_many :prints, :through => :project_print

  accepts_nested_attributes_for :prints

  validates_presence_of :title


  def generate
    puts '>> generating the prints'

    photos = Photo.all

    photos.each_with_index do |photo, index|
      puts ">> #{index}"

      if index.odd?
        even = photos[index - 1]

        pprint = Print.new

        pprint.title = "the title"
        pprint.left_photo_id = even.id
        pprint.right_photo_id = photo.id
        
        puts ">> print.inspect #{pprint.inspect}"
        pprint.save!
      end

    end

  end

end

projects_controller.rb

class ProjectsController < ApplicationController
  before_action :set_project, only: [:generate, :show, :edit, :update, :destroy]

  # GET /projects
  # GET /projects.json
  def index
    @projects = Project.all
  end

  # GET /projects/1
  # GET /projects/1.json
  def show
  end

  # GET /projects/new
  def new
    @project = Project.new
  end

  # GET /projects/1/edit
  def edit
  end

  # POST /projects
  # POST /projects.json
  def create
    @project = Project.new(project_params)

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

  # PATCH/PUT /projects/1/generate
  def generate
    respond_to do |format|
      if @project.generate
        format.html { redirect_to @project, notice: 'Project successfully generated prints.' }
        format.json { render :show, status: :ok, location: @project }
      else
        format.html { render :edit }
        format.json { render json: @project.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /projects/1
  # PATCH/PUT /projects/1.json
  def update
    respond_to do |format|
      if @project.update(project_params)
        format.html { redirect_to @project, notice: 'Project was successfully updated.' }
        format.json { render :show, status: :ok, location: @project }
      else
        format.html { render :edit }
        format.json { render json: @project.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /projects/1
  # DELETE /projects/1.json
  def destroy
    @project.destroy
    respond_to do |format|
      format.html { redirect_to projects_url, notice: 'Project was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_project
      @project = Project.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def project_params
      params.require(:project).permit(:title, :project_print)
    end
end

rails-console-output.txt

Started PATCH "/projects/2/generate" for ::1 at 2017-05-20 10:17:40 -0400
Processing by ProjectsController#generate as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"uu0E0/6ysaJxYzGEQqMscDbmNbFWVSFgV7mKaFdRX4N48swlAUOW0cxuMjCg9SAa6+XiyflHXdZVsPxxym3vKw==", "id"=>"2"}
  User Load (0.7ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT ?  [["id", 1], ["LIMIT", 1]]
  Project Load (0.1ms)  SELECT  "projects".* FROM "projects" WHERE "projects"."id" = ? LIMIT ?  [["id", 2], ["LIMIT", 1]]
>> in generate
>> generating the prints
  Photo Load (0.1ms)  SELECT "photos".* FROM "photos"
>> 0
>> 1
>> print.inspect #<Print id: nil, title: nil, projectprint_id: nil, printphoto_id: nil, created_at: nil, updated_at: nil, left_photo_id: nil, right_photo_id: nil>
   (0.2ms)  begin transaction
  SQL (2.1ms)  INSERT INTO "prints" ("created_at", "updated_at") VALUES (?, ?)  [["created_at", 2017-05-20 14:17:40 UTC], ["updated_at", 2017-05-20 14:17:40 UTC]]
   (0.8ms)  commit transaction
>> 2
>> 3
>> print.inspect #<Print id: nil, title: nil, projectprint_id: nil, printphoto_id: nil, created_at: nil, updated_at: nil, left_photo_id: nil, right_photo_id: nil>
   (0.0ms)  begin transaction
  SQL (0.2ms)  INSERT INTO "prints" ("created_at", "updated_at") VALUES (?, ?)  [["created_at", 2017-05-20 14:17:40 UTC], ["updated_at", 2017-05-20 14:17:40 UTC]]
   (0.6ms)  commit transaction
>> 4
Redirected to http://localhost:3000/projects/2
Completed 302 Found in 41ms (ActiveRecord: 5.8ms)


Started GET "/projects/2" for ::1 at 2017-05-20 10:17:40 -0400
Processing by ProjectsController#show as HTML
  Parameters: {"id"=>"2"}
  User Load (0.3ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT ?  [["id", 1], ["LIMIT", 1]]
  Project Load (0.1ms)  SELECT  "projects".* FROM "projects" WHERE "projects"."id" = ? LIMIT ?  [["id", 2], ["LIMIT", 1]]
  Rendering projects/show.html.erb within layouts/application
   (0.2ms)  SELECT COUNT(*) FROM "prints" INNER JOIN "project_prints" ON "prints"."id" = "project_prints"."print_id" WHERE "project_prints"."project_id" = ?  [["project_id", 2]]
  CACHE (0.0ms)  SELECT COUNT(*) FROM "prints" INNER JOIN "project_prints" ON "prints"."id" = "project_prints"."print_id" WHERE "project_prints"."project_id" = ?  [["project_id", 2]]
  Rendered projects/show.html.erb within layouts/application (5.0ms)
Completed 200 OK in 51ms (Views: 46.7ms | ActiveRecord: 0.6ms)

routes.rb

Rails.application.routes.draw do
  resources :projects do
    resources :prints
  end

  resources :prints
  resources :photos

  get 'home/index'

  patch 'projects/:id/generate', to: 'projects#generate'
  put   'projects/:id/generate', to: 'projects#generate'

  devise_for :users
  # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
  root to: "home#index"
end