Writing a Scope containing a method - Rails 4 -

i new rails , or advise appreciated

• i trying write scope displays users ratings equal or greater 4. unsure why scope not working , appreciated

user.rb

scope :ratings_equal_and_greater_than_4, where('average_rating_final_score >= 4')  def average_rating_final_score     if self.average_rating_score == 1.0       1     elsif self.average_rating_score == 2.0       2     elsif self.average_rating_score == 3.0       3     elsif self.average_rating_score == 4.0       4     elsif self.average_rating_score == 5.0       5     else       self.average_rating_score     end       end    def average_rating_score     ratings_total.to_f / ratings_count   end 

the scope works when written this:

<% if user.average_rating_final_score >= 4 %>    # display users ratings equal or greater 4 star <% end %> 

but write in views

@users.ratings_equal_and_greater_than_4 

could 1 kindly advise me how write correctly scope

rails scopes arel - kind of ruby wrapped sql. it's mean can't call ruby code sql statement this:

where('average_rating_final_score >= 4') 

but can define class method work want:

def self.ratings_equal_and_greater_than_4   all.reject{ |record| record.average_rating_final_score < 4 } end 

also can write propper sql query:

where('(`table_name.ratings_total` / `table_name.ratings_count`) >= 4')