Question

Using Mongoid 2.4.5 on Rails 3.2.1

I have a Model Book that has_many :pages.

class Book
  include Mongoid::Document

  has_many :pages
end

class Page
  include Mongoid::Document

  field :page_number
  belongs_to :book
  validates_uniqueness_of :page_number, scope: :book
end

I’m using nested resources so that I can get urls like /books/4f450e7a84b93e2b44000001/pages/4f4bba1384b93ea750000003/

What I would like to be able to do is use a url like /books/4f450e7a84b93e2b44000001/pages/3/ to get the third page in that book.

Now the crux of the question:
I want to find the page via a call like Book.find('4f450e7a84b93e2b44000001').pages.find('3') or like Book.find('4f450e7a84b93e2b44000001').pages.find('4f4bba1384b93ea750000003')

I know that I can override the find method in Page with something like

  class << self
    def find(*args)
      where(:page_number => args.first).first || super(args)
    end
  end

But that doesn’t seem to have any effect on the scoped query book.pages.find('3') as it seems the scoped search uses a different find method.

How do I specifically override the find method used by book.pages.find('3')?

Answer 1

Why just do a where criteria on your pages ?

Book.find('4f450e7a84b93e2b44000001').pages.where( :page_number => '3')

You can do a scope to in your Pages

class Page
  scope :page_number, lambda{|num| where(:page_number => num) }
end

and use it like :

Book.find('4f450e7a84b93e2b44000001').pages.page_number('3')