And join table

app/assets/javascripts/contents.coffee

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+# Place all the behaviors and hooks related to the matching controller here.
+# All this logic will automatically be available in application.js.
+# You can use CoffeeScript in this file: http://coffeescript.org/

app/assets/javascripts/courses.coffee

@@ -0,0 +1,3 @@
+# Place all the behaviors and hooks related to the matching controller here.
+# All this logic will automatically be available in application.js.
+# You can use CoffeeScript in this file: http://coffeescript.org/

app/assets/javascripts/users.coffee

@@ -0,0 +1,3 @@
+# Place all the behaviors and hooks related to the matching controller here.
+# All this logic will automatically be available in application.js.
+# You can use CoffeeScript in this file: http://coffeescript.org/

app/assets/stylesheets/contents.scss

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+// Place all the styles related to the Contents controller here.
+// They will automatically be included in application.css.
+// You can use Sass (SCSS) here: http://sass-lang.com/

app/assets/stylesheets/courses.scss

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+// Place all the styles related to the Courses controller here.
+// They will automatically be included in application.css.
+// You can use Sass (SCSS) here: http://sass-lang.com/

app/assets/stylesheets/scaffolds.scss

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+body {
+  background-color: #fff;
+  color: #333;
+  font-family: verdana, arial, helvetica, sans-serif;
+  font-size: 13px;
+  line-height: 18px;
+  margin: 33px;
+}
+
+p, ol, ul, td {
+  font-family: verdana, arial, helvetica, sans-serif;
+  font-size: 13px;
+  line-height: 18px;
+  margin: 33px;
+}
+
+pre {
+  background-color: #eee;
+  padding: 10px;
+  font-size: 11px;
+}
+
+a {
+  color: #000;
+
+  &:visited {
+    color: #666;
+  }
+
+  &:hover {
+    color: #fff;
+    background-color: #000;
+  }
+}
+
+th {
+  padding-bottom: 5px;
+}
+
+td {
+  padding-bottom: 7px;
+  padding-left: 5px;
+  padding-right: 5px;
+}
+
+div {
+  &.field, &.actions {
+    margin-bottom: 10px;
+  }
+}
+
+#notice {
+  color: green;
+}
+
+.field_with_errors {
+  padding: 2px;
+  background-color: red;
+  display: table;
+}
+
+#error_explanation {
+  width: 450px;
+  border: 2px solid red;
+  padding: 7px;
+  padding-bottom: 0;
+  margin-bottom: 20px;
+  background-color: #f0f0f0;
+
+  h2 {
+    text-align: left;
+    font-weight: bold;
+    padding: 5px 5px 5px 15px;
+    font-size: 12px;
+    margin: -7px;
+    margin-bottom: 0;
+    background-color: #c00;
+    color: #fff;
+  }
+
+  ul li {
+    font-size: 12px;
+    list-style: square;
+  }
+}
+
+label {
+  display: block;
+}

app/assets/stylesheets/users.scss

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+// Place all the styles related to the Users controller here.
+// They will automatically be included in application.css.
+// You can use Sass (SCSS) here: http://sass-lang.com/

app/controllers/contents_controller.rb

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+class ContentsController < ApplicationController
+  before_action :set_content, only: [:show, :edit, :update, :destroy]
+
+  # GET /contents
+  # GET /contents.json
+  def index
+    @contents = Content.all
+  end
+
+  # GET /contents/1
+  # GET /contents/1.json
+  def show
+  end
+
+  # GET /contents/new
+  def new
+    @content = Content.new
+  end
+
+  # GET /contents/1/edit
+  def edit
+  end
+
+  # POST /contents
+  # POST /contents.json
+  def create
+    @content = Content.new(content_params)
+
+    respond_to do |format|
+      if @content.save
+        format.html { redirect_to @content, notice: 'Content was successfully created.' }
+        format.json { render :show, status: :created, location: @content }
+      else
+        format.html { render :new }
+        format.json { render json: @content.errors, status: :unprocessable_entity }
+      end
+    end
+  end
+
+  # PATCH/PUT /contents/1
+  # PATCH/PUT /contents/1.json
+  def update
+    respond_to do |format|
+      if @content.update(content_params)
+        format.html { redirect_to @content, notice: 'Content was successfully updated.' }
+        format.json { render :show, status: :ok, location: @content }
+      else
+        format.html { render :edit }
+        format.json { render json: @content.errors, status: :unprocessable_entity }
+      end
+    end
+  end
+
+  # DELETE /contents/1
+  # DELETE /contents/1.json
+  def destroy
+    @content.destroy
+    respond_to do |format|
+      format.html { redirect_to contents_url, notice: 'Content was successfully destroyed.' }
+      format.json { head :no_content }
+    end
+  end
+
+  private
+    # Use callbacks to share common setup or constraints between actions.
+    def set_content
+      @content = Content.find(params[:id])
+    end
+
+    # Never trust parameters from the scary internet, only allow the white list through.
+    def content_params
+      params.require(:content).permit(:name)
+    end
+end

app/controllers/courses_controller.rb

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+class CoursesController < ApplicationController
+  before_action :set_course, only: [:show, :edit, :update, :destroy]
+
+  # GET /courses
+  # GET /courses.json
+  def index
+    @courses = Course.all
+  end
+
+  # GET /courses/1
+  # GET /courses/1.json
+  def show
+  end
+
+  # GET /courses/new
+  def new
+    @course = Course.new
+  end
+
+  # GET /courses/1/edit
+  def edit
+  end
+
+  # POST /courses
+  # POST /courses.json
+  def create
+    @course = Course.new(course_params)
+
+    respond_to do |format|
+      if @course.save
+        format.html { redirect_to @course, notice: 'Course was successfully created.' }
+        format.json { render :show, status: :created, location: @course }
+      else
+        format.html { render :new }
+        format.json { render json: @course.errors, status: :unprocessable_entity }
+      end
+    end
+  end
+
+  # PATCH/PUT /courses/1
+  # PATCH/PUT /courses/1.json
+  def update
+    respond_to do |format|
+      if @course.update(course_params)
+        format.html { redirect_to @course, notice: 'Course was successfully updated.' }
+        format.json { render :show, status: :ok, location: @course }
+      else
+        format.html { render :edit }
+        format.json { render json: @course.errors, status: :unprocessable_entity }
+      end
+    end
+  end
+
+  # DELETE /courses/1
+  # DELETE /courses/1.json
+  def destroy
+    @course.destroy
+    respond_to do |format|
+      format.html { redirect_to courses_url, notice: 'Course was successfully destroyed.' }
+      format.json { head :no_content }
+    end
+  end
+
+  private
+    # Use callbacks to share common setup or constraints between actions.
+    def set_course
+      @course = Course.find(params[:id])
+    end
+
+    # Never trust parameters from the scary internet, only allow the white list through.
+    def course_params
+      params.require(:course).permit(:name)
+    end
+end

app/controllers/users_controller.rb

@@ -0,0 +1,74 @@
+class UsersController < ApplicationController
+  before_action :set_user, only: [:show, :edit, :update, :destroy]
+
+  # GET /users
+  # GET /users.json
+  def index
+    @users = User.all
+  end
+
+  # GET /users/1
+  # GET /users/1.json
+  def show
+  end
+
+  # GET /users/new
+  def new
+    @user = User.new
+  end
+
+  # GET /users/1/edit
+  def edit
+  end
+
+  # POST /users
+  # POST /users.json
+  def create
+    @user = User.new(user_params)
+
+    respond_to do |format|
+      if @user.save
+        format.html { redirect_to @user, notice: 'User was successfully created.' }
+        format.json { render :show, status: :created, location: @user }
+      else
+        format.html { render :new }
+        format.json { render json: @user.errors, status: :unprocessable_entity }
+      end
+    end
+  end
+
+  # PATCH/PUT /users/1
+  # PATCH/PUT /users/1.json
+  def update
+    respond_to do |format|
+      if @user.update(user_params)
+        format.html { redirect_to @user, notice: 'User was successfully updated.' }
+        format.json { render :show, status: :ok, location: @user }
+      else
+        format.html { render :edit }
+        format.json { render json: @user.errors, status: :unprocessable_entity }
+      end
+    end
+  end
+
+  # DELETE /users/1
+  # DELETE /users/1.json
+  def destroy
+    @user.destroy
+    respond_to do |format|
+      format.html { redirect_to users_url, notice: 'User was successfully destroyed.' }
+      format.json { head :no_content }
+    end
+  end
+
+  private
+    # Use callbacks to share common setup or constraints between actions.
+    def set_user
+      @user = User.find(params[:id])
+    end
+
+    # Never trust parameters from the scary internet, only allow the white list through.
+    def user_params
+      params.require(:user).permit(:name)
+    end
+end

app/helpers/contents_helper.rb

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+module ContentsHelper
+end

app/helpers/courses_helper.rb

@@ -0,0 +1,2 @@
+module CoursesHelper
+end

app/helpers/users_helper.rb

@@ -0,0 +1,2 @@
+module UsersHelper
+end

app/models/content.rb

@@ -0,0 +1,3 @@
+class Content < ApplicationRecord
+	  has_and_belongs_to_many :courses
+end

app/models/course.rb

@@ -0,0 +1,4 @@
+class Course < ApplicationRecord
+	has_and_belongs_to_many :users
+  has_and_belongs_to_many :contents
+end

app/models/user.rb

@@ -0,0 +1,3 @@
+class User < ApplicationRecord
+	has_and_belongs_to_many :courses
+end

app/views/contents/_content.json.jbuilder

@@ -0,0 +1,2 @@
+json.extract! content, :id, :name, :created_at, :updated_at
+json.url content_url(content, format: :json)

app/views/contents/_form.html.erb

@@ -0,0 +1,22 @@
+<%= form_for(content) do |f| %>
+  <% if content.errors.any? %>
+    <div id="error_explanation">
+      <h2><%= pluralize(content.errors.count, "error") %> prohibited this content from being saved:</h2>
+
+      <ul>
+      <% content.errors.full_messages.each do |message| %>
+        <li><%= message %></li>
+      <% end %>
+      </ul>
+    </div>
+  <% end %>
+
+  <div class="field">
+    <%= f.label :name %>
+    <%= f.text_field :name %>
+  </div>
+
+  <div class="actions">
+    <%= f.submit %>
+  </div>
+<% end %>

app/views/contents/edit.html.erb

@@ -0,0 +1,6 @@
+<h1>Editing Content</h1>
+
+<%= render 'form', content: @content %>
+
+<%= link_to 'Show', @content %> |
+<%= link_to 'Back', contents_path %>