The `PlayerScore` class represents a player's completion grade in a video game. For some inexplicable reason, the possible grades, from best to worst, are: "S+", "S", and "A". This class implements the spaceship operator, so that it can mix in `Comparable`.

player_score.rb

class PlayerScore

  include Comparable

  attr_accessor :grade

  def <=>(other)
    return 0 if grade == other.grade
    if grade == "S+"
      return 1
    elsif grade == "A"
      return -1
    else
      if other.grade == "S+"
        return -1
      else
        return 1
      end
    end
  end

end

first_score = PlayerScore.new
first_score.grade = "S+"
second_score = PlayerScore.new
second_score.grade = "S"

puts first_score <=> second_score # => 1
puts second_score <=> first_score # => -1

Are there other ways to implement <=> that are more concise (without being too obscure)? Are there other ways to implement <=> that are less concise, but clearer?

A suggestion from Logan Barnett reduced this to:

class PlayerScore                          

  include Comparable                       

  attr_accessor :grade                     

  def <=>(other)                           
    ranks = {"S+" => 3, "S" => 2, "A" => 1}
    ranks[grade] <=> ranks[other.grade]    
  end                                      

end                                        

...Which seems both shorter and clearer. Unless somebody else knows a more widely-used solution, I think I'm going with this. Thanks for looking, folks!