Group Book Orders by Author - ruby

Question

I have created a functioning e-commerce platform where Members can buy books. Everything works fine, But I would like to group all of my Orders in my Index Page by Author.
Currently I am able to group each Author, but then every existing Book Order gets listed under each Author. As oppose to only listing the Book Orders corresponding to that Author.
EX. of what I'd like in my Orders Page
###Orders grouped by Authors
Author1
Book1 belongs_to Author1 ###BookOrders grouped by Author
Book2 belongs_to Author1
Book3 belongs_to Author1
Author2
Book1 belongs_to Author2
Book2 belongs_to Author2
Author3
Book1 belongs_to Author3
MODELS
class Order < ActiveRecord::Base
attr_accessible :author_id, :book_id, :user_id, :order_date
belongs_to :book
belongs_to :user
end
class Book < ActiveRecord::Base
attr_accessible : author_id, :title, :price
belongs_to : author
has_many :orders
end
class Author < ActiveRecord::Base
attr_accessible :name
has_many :books
end
CONTROLLER
def index
###How Can I combine this so it Groups Book Orders By Author
###Groups Orders by Author
#orders = Order.find(:all, :order => 'author_id, id', :limit => 50)
#author_orders = #orders.group_by { |order| order.book.author.name }
###Groups Orders by Book
#orders = Order.find(:all, :order => 'author_id, id', :limit => 50)
#book_orders = #orders.group_by { |order| order.book.title }
end
VIEWS
<% #author_orders.each do |author, orders| %>
<h2><%= author %> </h2>
<% #book_orders.each do |book, orders| %>
<h4><%= book %> </h4>
<% end %>
<% end %>

Answer 1

Why not instead:
Model:
class Author < ActiveRecord::Base
attr_accessible :name
has_many :books
has_many :orders, through: :books
end
Controller:
def index
#authors = Author.includes(:orders)
end
View
<% #authors.each do |author| %>
<h2><%= author.name %> </h2>
<% author.orders.each do |order| %>
<h4><%= order.book.title %> </h4>
<% end %>
<% end %>
Update:
To display only those authors who have an order you need unfortunately to do some gymnastics. Also previous includes will not save you completely from N+1 and needs to be improved.
#authors = Author.includes(orders: :books).where('orders.id IS NOT NULL')

Answer 2

You are really close I think.
You just need to get your books from the order that belongs to the author.
Like this...
<% #author_orders.each do |author, orders| %>
<h2><%= author %> </h2>
<% orders.each do |order| %>
<h4><%= order.book %> </h4>
<% end %>
<% end %>