Теория: Вложенные ресурсы

bin/rails g scaffold book title:string
bin/rails g scaffold page body:text book:references
bin/rails db:migrate

class Book < ApplicationRecord
  has_many :pages
end

class Page < ApplicationRecord
  belongs_to :book
end

Rails.application.routes.draw do
  root 'books#index'
  # родительский ID передаётся из пути
  # GET books/:book_id/pages
  # GET books/:book_id/pages/new
  # POST books/:book_id/pages
  resources :books, except: [:index] do
    resources :pages, only: [:index, :new, :create]
  end

  resources :books, except: [:index], shallow: true do
    resources :pages, only: [:show, :edit, :update, :destroy]
  end
end

class PagesController < ApplicationController
  before_action :set_book, only: %i[ index new create ]
  before_action :set_page, only: %i[ show edit update destroy ]

  # GET /book/1/pages
  def index
    @pages = @book.pages
  end

  # GET /pages/1
  def show
  end

  # GET book/1//pages/new
  def new
    @page = @book.pages.build
  end

  # GET /pages/1/edit
  def edit
  end

  # POST /book/1/pages
  def create
    @page = @book.pages.build(page_params)

    if @page.save
      redirect_to book_path(@book), notice: "Page was successfully created."
    else
      render :new, status: :unprocessable_entity
    end
  end

  # PATCH/PUT /pages/1
  def update
    if @page.update(page_params)
      redirect_to book_path(@page.book), notice: "Page was successfully updated."
    else
      render :edit, status: :unprocessable_entity
    end
  end

  # DELETE /pages/1
  def destroy
    @page.destroy
    format.html { redirect_to pages_url, notice: "Page was successfully destroyed." }
  end

  private

  def set_book
    @book = Book.find(params[:book_id])
  end

  def set_page
    @page = Page.find(params[:id])
  end

  def page_params
    params.require(:page).permit(:body, :book_id)
  end
end

<p id="notice"><%= notice %></p>

<p>
  <strong>Title:</strong>
  <%= @book.title %>
</p>

<%= link_to 'Add new page', new_book_page_path(@book) %> |
<%= link_to 'Edit', edit_book_path(@book) %> |
<%= link_to 'Back', root_path %>


<h1>Pages</h1>

<table>
  <thead>
    <tr>
      <th>Body</th>
      <th colspan="3"></th>
    </tr>
  </thead>

  <tbody>
    <% @book.pages.each do |page| %>
      <tr>
        <td><%= page.body %></td>
        <td><%= link_to 'Edit', edit_page_path(page) %></td>
        <td><%= link_to 'Destroy', page, data: { turbo_method: :delete, turbo_confirm: 'Are you sure?' } %></td>
      </tr>
    <% end %>
  </tbody>
</table>

<br>

# Контроллер модуля наследуется от базового контроллера
class Web::ApplicationController < ApplicationController
end

class Web::BooksController < Web::ApplicationController
  ...
end
# module Web
#   class BooksController < ApplicationController
#   ...
#   end
# end

class Web::PagesController < Web::ApplicationController
  ...
end
# module Web
#   class PagesController < ApplicationController
#   ...
#   end
# end

Rails.application.routes.draw do
  # Контроллеры и вьюхи должны находиться в модуле Web
  # Задаётся только модуль, имена роутов и пути не изменяются
  scope module: :web do
    root 'books#index'
    resources :books, except: [:index] do
      resources :pages, only: [:index, :new, :create]
    end

    resources :books, except: [:index], shallow: true do
      resources :pages, only: [:show, :edit, :update, :destroy]
    end
  end
end

Rails.application.routes.draw do
  scope module: :web do
    root 'books#index'
    resources :books, except: [:index] do
      resources :pages, only: [:index, :new, :create]
      # добавляется метод для каждого экземпляра ресурса
      post :publish
    end
  end
end

# bin/rails routes -g publish
#       Prefix Verb   URI Pattern                       Controller#Action
# book_publish POST   /books/:book_id/publish(.:format) web/books#publish


Rails.application.routes.draw do
  scope module: :web do
    root 'books#index'
    resources :books, except: [:index] do
      # добавляется метод для каждого экземпляра ресурса
      collection do
        # Метод один для всех данных ресурсов
        post :publish
      end
    end
  end
end

# bin/rails routes -g publish
# =>        Prefix Verb   URI Pattern               Controller#Action
# => publish_books POST   /books/publish(.:format)  web/books#publish

Rails.application.routes.draw do
  scope module: :web do
    root 'books#index'
    resources :books, except: [:index] do
      # добавляется метод для каждого экземпляра ресурса
      member do
        post :publish
      end
    end
  end
end

# bin/rails routes -g publish
# =>       Prefix Verb URI Pattern                  Controller#Action
# => publish_book POST /books/:id/publish(.:format) web/books#publish