Rails协会Has_Many

Question

I am trying to fetch the information from books associated with a customer but seem that the middle association doesn't works

Here my model

Book
    has_one :book_manager
    has_one :customer, :through => :book_manager

Customer
    has_many :book_managers
    has_many :books, :through => :book_managers

Book_Manager
    belongs_to :customer
    belongs_to :book

The field are has follow

Book          Customer      book_manager
id            id            id
description   email         customer_id
              password      book_id
              first         visible
              last

When fetching the information in my def edit, the following is successfull

@book = Book.first
@book = Book.last

The following seem to fails

@customer = Customer.find(params[:id])
@book = @customer.books.first
@book = @customer.books.order("created_at DESC").first

Is there something i miss?

I also try to verify by creating an index for book_manager controller and view and nothing appears, its seems its empty. The way i created the books was as follow

BookController

def create
@book = current_customer.books.build(params[:book])
    if @book.save
        flash[:success] = "Book Created"
        redirect_to root_url
    else
        render 'customer/edit'
    end
end

I have updated my relationship but still doesn't to work

The idea is has follow

A customer update his status, which consist of many subsection such has

-Phone
-Book
-Interest

Under book I should see if there exist an empty book related to the customer, if so then showcase the last book. if not then customer see blank and can create a new one

The books managers is only there to maintain the relationship and also because i want to keep the data and i want to allow user to determine if we show this data to everyone else in the site or not.

Answer 1

Here's my suggestion. I'm doing this in sqlite3 (with in-memory database) just for demonstration purposes.

Connect (in rails, use the database.yml instead):

ActiveRecord::Base.establish_connection :adapter => 'sqlite3', :database => ':memory:'

Setup classes:

class Customer < ActiveRecord::Base
  has_many :book_managers
  has_many :books, :through => :book_managers
end

class BookManager < ActiveRecord::Base
  belongs_to :customer
  has_many :books
end

class Book < ActiveRecord::Base
  belongs_to :book_manager
  def customer
    book_manager.customer
  end
end

Create schema (This is here just to show the columns. In rails, use migrations):

Book.connection.create_table(Book.table_name) do |t|
  t.string :description
  t.integer :book_manager_id
end
BookManager.connection.create_table(BookManager.table_name) do |t|
   t.boolean :visible
  t.integer :customer_id
end
Customer.connection.create_table(Customer.table_name) do |t|
  t.string :email
  t.string :password
  t.string :first
  t.string :last
end

Create a record

cust = Customer.new :email => 'user@example.com'
cust.book_managers.build :visible => true
cust.book_managers.first.books.build :description => 'the odyssey'
cust.save!

Retrieve

cust = Customer.find 1
# test the has_many :through
cust.books
# test the Book#customer method
Book.first.customer