ActiveSupport::Concern

app/assets/javascripts/books.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/news_papers.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/stylesheets/books.scss

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

app/assets/stylesheets/news_papers.scss

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+// Place all the styles related to the NewsPapers 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;
+  margin: 33px;
+  font-family: verdana, arial, helvetica, sans-serif;
+  font-size: 13px;
+  line-height: 18px;
+}
+
+p, ol, ul, td {
+  font-family: verdana, arial, helvetica, sans-serif;
+  font-size: 13px;
+  line-height: 18px;
+}
+
+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: 0 5px 7px;
+}
+
+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 7px 0;
+  margin-bottom: 20px;
+  background-color: #f0f0f0;
+
+  h2 {
+    text-align: left;
+    font-weight: bold;
+    padding: 5px 5px 5px 15px;
+    font-size: 12px;
+    margin: -7px -7px 0;
+    background-color: #c00;
+    color: #fff;
+  }
+
+  ul li {
+    font-size: 12px;
+    list-style: square;
+  }
+}
+
+label {
+  display: block;
+}

app/controllers/books_controller.rb

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

app/controllers/news_papers_controller.rb

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

app/helpers/books_helper.rb

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+module BooksHelper
+end

app/helpers/news_papers_helper.rb

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+module NewsPapersHelper
+end

app/models/book.rb

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+class Book < ApplicationRecord
+  include Useful
+
+  validates :title, presence: true
+  validates :status, presence: true
+
+  enum status: { draft: 0, published: 1 }
+end

app/models/concerns/draftable.rb

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+module Draftable
+  extend ActiveSupport::Concern
+
+  included do
+    before_save { check_and_change_status }
+  end
+
+  def check_and_change_status
+    self.status = 'draft' if self.title.include?('::draft')
+  end
+end

app/models/concerns/findable.rb

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+module Findable
+  extend ActiveSupport::Concern
+
+  class_methods do
+    def in_any_status
+      where(status: statuses.keys)
+    end
+  end
+end

app/models/concerns/useful.rb

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+module Useful
+  extend ActiveSupport::Concern
+  include Findable
+  include Draftable
+end

app/models/news_paper.rb

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+class NewsPaper < ApplicationRecord
+  include Useful
+
+  validates :title, presence: true
+  validates :status, presence: true
+
+  enum status: { draft: 0, published: 1 }
+end

app/views/books/_book.json.jbuilder

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+json.extract! book, :id, :title, :status, :created_at, :updated_at
+json.url book_url(book, format: :json)

app/views/books/_form.html.erb

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+<%= form_with(model: book, local: true) do |form| %>
+  <% if book.errors.any? %>
+    <div id="error_explanation">
+      <h2><%= pluralize(book.errors.count, "error") %> prohibited this book from being saved:</h2>
+
+      <ul>
+      <% book.errors.full_messages.each do |message| %>
+        <li><%= message %></li>
+      <% end %>
+      </ul>
+    </div>
+  <% end %>
+
+  <div class="field">
+    <%= form.label :title %>
+    <%= form.text_field :title %>
+  </div>
+
+  <div class="field">
+    <%= form.label :status %>
+    <%= form.select :status, Book.statuses.keys %>
+  </div>
+
+  <div class="actions">
+    <%= form.submit %>
+  </div>
+<% end %>

app/views/books/edit.html.erb

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+<h1>Editing Book</h1>
+
+<%= render 'form', book: @book %>
+
+<%= link_to 'Show', @book %> |
+<%= link_to 'Back', books_path %>

app/views/books/index.html.erb

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+<p id="notice"><%= notice %></p>
+
+<h1>Books</h1>
+
+<table>
+  <thead>
+    <tr>
+      <th>Title</th>
+      <th>Status</th>
+      <th colspan="3"></th>
+    </tr>
+  </thead>
+
+  <tbody>
+    <% @books.each do |book| %>
+      <tr>
+        <td><%= book.title %></td>
+        <td><%= book.status %></td>
+        <td><%= link_to 'Show', book %></td>
+        <td><%= link_to 'Edit', edit_book_path(book) %></td>
+        <td><%= link_to 'Destroy', book, method: :delete, data: { confirm: 'Are you sure?' } %></td>
+      </tr>
+    <% end %>
+  </tbody>
+</table>
+
+<br>
+
+<%= link_to 'New Book', new_book_path %>

app/views/books/index.json.jbuilder

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+json.array! @books, partial: 'books/book', as: :book

app/views/books/new.html.erb

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+<h1>New Book</h1>
+
+<%= render 'form', book: @book %>
+
+<%= link_to 'Back', books_path %>

app/views/books/show.html.erb

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+<p id="notice"><%= notice %></p>
+
+<p>
+  <strong>Title:</strong>
+  <%= @book.title %>
+</p>
+
+<p>
+  <strong>Status:</strong>
+  <%= @book.status %>
+</p>
+
+<%= link_to 'Edit', edit_book_path(@book) %> |
+<%= link_to 'Back', books_path %>

app/views/books/show.json.jbuilder

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+json.partial! "books/book", book: @book