Question

I would like to sort my links using an algorithm, all the information needed can be derived from values in my Links table. How can I return items sorted by the item’s calculated Score?

Schema https://gist.github.com/1326044

Index Action https://gist.github.com/1326045

Time Calculation https://gist.github.com/1326050

Algorithm

  # Score = (P-1) / (T+2)^G 
  # P = points of an item (and -1 is to negate submitters vote)
  # T = time since submission (in hours)
  # G = Gravity, defaults to 1.8

Answer 1

I’d do as follows:

First, in your model:

after_initialize :calculate_score

attr_accessor :score

def calculate_score
  unless self.new_record?
    time_elapsed = (Time.zone.now - self.created_at) / 3600
    self.score = (self.points-1) / (time_elapsed+2)^G # I don't know how you retrieve G
  end
end  

In your controller:

@links = Link.all.sort_by(&:score)