Refactor with Strategy Pattern. In Ruby

Heads up! In the below example, using a pattern is probably overkill... however, if I were extending this to count genres, count the members in a given band, count the number of fans, count the number of venues played, count the number of records sold, count the number of downloads for a specific song etc... it seems like there could be a ton of stuff to count.

The Goal:

To create a new function that chooses the correct counting function based on the input.

The Example:

class Genre < ActiveRecord::Base
  has_many :songs
  has_many :artists, through: :songs

  def song_count
    self.songs.length
  end

  def artist_count
    self.artists.length
  end

end

P.S. If you are also a curious about this question, you may find this other question (unfortunately answered in C#) to be helpful as a supplemental context. Strategy or Command pattern? ...