gistfile1.rb

def set_position
  if not self.special
    categories = self.user.categories.normal.with_position.asc(:position)
    if categories.present? && categories.count > 0
      self.position = categories.last.position + 1
    else
      self.position = 1
    end
  end
end

Did you set inverse_of on the relation?

I did not. I thought this is no longer necessary for Mongoid 2.x.

…

On Aug 5, 2011, at 9:35 PM, paulelliott wrote: Did you set inverse_of on the relation? ## Reply to this email directly or view it on GitHub: https://gist.github.com/1127539

You need it for the identity map to work correctly, so although it isn't "required" it is highly recommended.

…

-- Paul

On Friday, August 5, 2011 at 9:42 AM, steverandy wrote: I did not. I thought this is no longer necessary for Mongoid 2.x. On Aug 5, 2011, at 9:35 PM, paulelliott wrote: > Did you set inverse_of on the relation? > ## > > Reply to this email directly or view it on GitHub: > https://gist.github.com/1127539 ## Reply to this email directly or view it on GitHub: https://gist.github.com/1127539

Sorry it did actually have inverse_of.

class User
  include Mongoid::Document
  include Mongoid::Timestamps

  embeds_many :categories, :validate => false
end

class Category
  include Mongoid::Document
  include Mongoid::Timestamps

  embedded_in :user, :inverse_of => :categories
end

The error was the following

NoMethodError: undefined method `categories' for nil:NilClass

The methods was called from self.user.categories.normal.with_position.asc(:position) from the following codes.

def set_position
  if not self.special
    categories = self.user.categories.normal.with_position.asc(:position)
    if categories.present? && categories.count > 0
      self.position = categories.last.position + 1
    else
      self.position = 1
    end
  end
end

Where is the set_position method? Is it in the category?

Can you post the fabricators being used in here as well?

class Category
  include Mongoid::Document
  include Mongoid::Timestamps

  embedded_in :user, :inverse_of => :categories

  before_create :set_position

  def set_position
    if not self.special
      categories = self.user.categories.normal.with_position.asc(:position)
      if categories.present? && categories.count > 0
        self.position = categories.last.position + 1
      else
        self.position = 1
      end
    end
  end
end

For the fabricator:

Fabricator(:category) do
  title { Fabricate.sequence(:title) { |i| "Category #{i}" } }
end

Fabricator(:user) do
  full_name { Fabricate.sequence(:full_name) { |i| "User #{i}" } }
  username { Fabricate.sequence(:username) { |i| "user#{i}" } }
  email { Fabricate.sequence(:email) { |i| "user#{i}@example.com" } }
  password "password"
  password_confirmation "password"
end

And the unit test

  test "should have position" do
    user = Fabricate :user
    category = Fabricate :category, :user => user, :title => "Category"
    assert_equal category.position, 1
  end