Keep getting NoMethodError in Chapters#create - ruby-on-rails

Question

I have books, with chapters nested underneath, with questions for each chapter nested within the chapters, and comments nested in the questions.
When I click on new chapter on the books page how do I get it to save to the book its associated with, and how do I get the books#show page to loop through all the chapter titles (with links to each chapters show page).
This is the error: undefined method `title' for nil:NilClass. Referring to this file: Users/bardiap/saasapp/app/views/books/show.html.erb
<div class="homepage">
<h1><%= #book.title %></h1>
<%= link_to 'New chapter', new_book_chapter_path(#book, #chapter) %>
<% #chapters.each do |chapter| %>
<h3><%= link_to chapter.title, chapter %></h3>
<% end %>
<p>
<%= link_to 'Edit', edit_book_path(#book) %> |
<%= link_to 'Destroy', book_path(#book),
method: :delete,
data: { confirm: 'Are you sure?' } %> |
<%= link_to 'Back', books_path %> |
</p>
</div>
Here is my books and chapters controllers:
class BooksController < ApplicationController
def show
#book = Book.find(params[:id])
#chapters = Chapter.where(book_id: #book.id).order("created_at ASC")
end
def index
#books = Book.all
end
def new
#book = Book.new
end
def edit
#book = Book.find(params[:id])
end
def create
#book = Book.new(book_params)
if #book.save
redirect_to #book
else
render 'new'
end
end
def update
#book = Book.find(params[:id])
if #book.update(book_params)
redirect_to #book
else
render 'edit'
end
end
def destroy
#book = Book.find(params[:id])
#book.destroy
redirect_to books_path
end
private
def book_params
params.require(:book).permit(:title,:text,:author)
end
end
Chapter
def show
#chapter = Chapter.find(params[:id])
#questions = question.where(chapter_id: #chapter.id).order("created_at ASC")
end
def index
#chapters = Chapter.all
end
def new
#chapter = Chapter.new
end
def edit
#chapter = Chapter.find(params[:id])
end
def create
#chapter = Chapter.new(chapter_params)
if #chapter.save
render 'books/show'
else
render 'books/show'
end
end
def update
#chapter = Chapter.find(params[:id])
if #chapter.update(chapter_params)
redirect_to #chapter
else
render 'edit'
end
end
def destroy
#chapter = Chapter.find(params[:id])
#chapter.destroy
redirect_to chapters_path
end
private
def chapter_params
params.require(:chapter).permit(:title, :text)
end
end
Here are the models and routes
class Book < ApplicationRecord
has_many :chapters
validates :title, presence: true,
length:{minimum: 5}
end
class Chapter < ApplicationRecord
has_many :questions
belongs_to :book
validates :title, presence: true,
length:{minimum: 5}
end
Routes
Rails.application.routes.draw do
devise_for :users
root to: 'pages#home'
get 'about', to: 'pages#about'
get 'terms', to: 'pages#terms'
get 'privacy', to: 'pages#privacy'
resources :contacts, only: :create
resources :podcasts
resources :books do
resources :chapters, shallow: true
end
resources :chapters do
resources :questions, shallow: true
end
resources :questions do
resources :comments, module: :questions, shallow: true
end
resources :users do
resource :profile
resources :comments
end
get 'contact-us', to: 'contacts#new', as: 'new_contact'
get 'podcast', to: 'pages#podcast'
resources :essays do
resources :comments, module: :essays, shallow: true
end
end
And views:
chapters/_form.html.erb
<%= form_for [#book, #chapter] do |form| %>
<p>
<%= form.label :title %><br>
<%= form.text_field :title %>
</p>
<p>
<%= form.label :text %><br>
<%= form.text_area :text %>
</p>
<p>
<%= form.submit "Submit" %>
</p>
<% end %>
chapters/index.html.erb
<div class="homepage">
<button class="mdl-button mdl-js-button mdl-button--fab mdl-button--mini-fab">
<i class="material-icons"><%= link_to "add", new_chapter_path%></i>
</button>
<div class="mdl-grid">
<% #chapters.each do |chapter| %>
<div class="mdl-cell mdl-cell--4-col">
<div class="demo-card-event mdl-card mdl-shadow--2dp">
<div class="mdl-card__title mdl-card--expand">
<h4>
<%=chapter.title%>
</h4>
</div>
<div class="mdl-card__actions mdl-card--border">
<%=link_to 'VIEW BOOK',chapter_path(chapter), class: "mdl-button mdl-button--colored mdl-js-button mdl-js-ripple-effect"%>
<div class="mdl-layout-spacer"></div>
<i class="material-icons">chapter</i>
</div>
</div>
</div>
<% end %>
</div>
<% #chapters.each do |chapter| %>
<%= link_to 'Edit', edit_chapter_path(chapter) %> |
<%= link_to 'Destroy', chapter_path(chapter),
method: :delete,
data: { confirm: 'Are you sure?' } %>
<% end %>
<br><br><br><br><br>
</div>
chapters/show.html.erb
<div class="homepage">
<h3><%= #chapter.title %></h3>
<h5><%= #chapter.text %></h5>
<p>
<%= link_to 'Edit', edit_book_path(#book) %> |
<%= link_to 'Destroy', book_path(#book),
method: :delete,
data: { confirm: 'Are you sure?' } %> |
<%= link_to 'Back', books_path %> |
</p>
</div>
Where am I going wrong, and is there other things I can do to make my code work better.

Answer 1

To create a new Chapter in a Book, in books/show:
<%= link_to 'New chapter', new_book_chapter_path(#book) %>
(No need to pass the chapter, as it will be created). Then, in ChaptersController#new:
def new
#book = Book.find_by(id: params[:book_id]
if #book
#chapter = #book.chapters.build
end
end
You can also change BooksController#show
def show
#book = Book.find_by(id: params[:id])
if #book
#chapters = #book.chapters.order("created_at ASC")
end
end