Rails how to order after an instance variable

In my konkurrancerstable I have:

rating_score => The current score (integer)
ratings => The number of ratings which led to the score (integer)

In my view I want to sort konkurrancers after rating. So I have to do this math: rating_score/ratings ratings may not be null because I can not divide be zero.

<% @konkurrencer.find(:all, :order => '@rating ASC', :limit => 5).each do |vind| %>
  <%= link_to(image_tag(vind.banner2, :style => 'border:none; width:125px; height:125px;'), vind.tracking, :target => '_blank')  %>
<% end %>

My controller:

class PublicController < ApplicationController
  helper_method :sort_column, :sort_direction
  def index 
    @konkurrencer = Konkurrancer
  end
end

My view:

15: <%= @konkurrencer.find(:all, :select => "rating_score/ratings AS rating", :order => 'rating ASC', :limit => 5).each do |da| %>
16: <%= da.banner2 %>
17: <% end %>

And I get following error:

ActiveModel::MissingAttributeError in Public#index Showing C:/Rails/konkurranceportalen/app/views/public/_konkurrencer.html.erb where line #16 raised: missing attribute: 开发者_JS百科banner2

How do I create the instance variable rating to order the konkurrancers?

---

If nothing else, you can sort your list of records by two criteria after retrieving them from the database.

In the index method in your controller, I'd do this:

@konkurrancers = Konkurrancer.find(:all, :order => '@rating ASC')
@konkurrancers.sort! {|a, b|
  rel = a.rating_score <=> b.rating_score
  # if "rating_scores" are equivalent, only then consider "ratings"
  rel == 0 ? a.ratings <=> b.ratings : rel
}

That much will give you a list of all your Konkurrencer objects, sorted by two criteria.

In your view, I'd do this:

<% @konkurrancers[0,5].each do |vind| %>
   <%= link_to(image_tag(vind.banner2, :style => 'border:none; width:125px; height:125px;'), vind.tracking, :target => '_blank')  %>
<% end %

That should create the html for only the first 5 items in the list you made in your controller. (Is that what you wanted?)

---

If you are using SQL you can use

@konkurrencer.find(:all, :select => "rating_score/ratings AS rating", :order => 'rating ASC', :limit => 5)

class Konkurrencer
  def rating
    self[:rating] || (rating_score/rating)
  end
end

rshallit linked to a good post about this above. However it is in Rails 3 and it appears you are using Rails < 3