gistfile1.txt

class User < ActiveRecord::Base
  has_many :residencies
  has_many :states, :through => :residencies
  
  def peers
    Residency.where(:state_id => self.state_ids).include(:users).users
  end
end

class State < ActiveRecord::Base
  has_many :residencies
  has_many :users, :through => :residencies
end

class Residency < ActiveRecord::Base
  belongs_to :user
  belongs_to :state
end