Question

I need to read more Ruby theory I have been told, which is fine but most literature I read is explained at a very high level and I don’t understand it. So this leads me to the question and my code

I have a module that deals with my api call

module Book::BookFinder

BOOK_URL = 'https://itunes.apple.com/lookup?isbn='

def book_search(search)
response = HTTParty.get(BOOK_URL + "#{search}", :headers => { 'Content-Type' => 'application/json', 'Accept' => 'application/json' })
results = JSON.parse(response.body)["results"]
end
end

and then my controller

class BookController < ApplicationController
before_filter :authenticate_admin_user!
include Book::BookFinder

def results
results = book_search(params[:search])
@results = results
@book = Book.new
@book.author = results[0]["artistName"]

end

def create
@book = Book.new(params[:book])
 if @book.save
redirect_to @book, notice: 'Book was successfully saved'
 else
render action:new
end
end
end

What I want to do is save the author value to my Book model. I get the error message

undefined method `new' for Book:Module

when conducting a search which in a previous post has been explained to me. A module cannot be instanced. The solution was to make a class? but maybe I am not understanding correctly as I am not sure where to put this class. The solution given to me was

 class Book
  def initialize
   # put constructor logic here
  end

 def some_method
 # methods that can be called on the instance
 # eg:
 # @book = Book.new
 # @book.some_method
 end

# defines a get/set property
  attr_accessor :author
# allows assignment of the author property
end

Now I am sure that this is a valid answer, but could anyone explain what is going on? Seeing an example with an explanation is more beneficial to me than reading lines and lines of text in a book.

Answer 1

module Finders

  ## Wrap BookFinder inside another module, Finders, to better organise related
  ## code and to help avoid name collisions
  ## lib/finders/book_finder.rb
  module BookFinder
    def bar
      puts "foo"
    end
  end  
end


## Another BookFinder module, but this one is not wrapped.
## lib/book_finder.rb
module BookFinder
  def foo
    puts 'bar'
  end
end


## Book is a standard Rails model inheriting from ActiveRecord
## app/models/book.rb
class Book < ActiveRecord::Base
  ## Mixin methods from both modules
  include BookFinder
  include HelperLibs::BookFinder
end

## app/controllers/books_controller.rb
class BookController
  def create
    book = Book.new
    book.foo
    book.bar

  end
end


BookController.new.create
 - bar
 - foo

In your code you are creating a module and a class with the same name – this is not allowed. The module overrides the class since it is loaded second.