matching_personalities.rb

# Model files

class Match < ActiveRecord::Base
  belongs_to :source, foreign_key: 'from_id', class_name: Personality
  belongs_to :target, foreign_key: 'to_id', class_name: Personality
end

class Person < ActiveRecord::Base
  belongs_to :personality

  def matches
    Person.where(personality_id: personality.matching_personalities.pluck(:id))
  end
end

class Personality < ActiveRecord::Base
  has_many :matches, foreign_key: 'from_id'
  has_many :matching_personalities, through: :matches, source: :target
end


# schema.rb

ActiveRecord::Schema.define(version: 20160407182307) do

  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"

  create_table "matches", force: :cascade do |t|
    t.integer  "from_id"
    t.integer  "to_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  create_table "people", force: :cascade do |t|
    t.integer  "personality_id"
    t.string   "name"
    t.datetime "created_at",     null: false
    t.datetime "updated_at",     null: false
  end

  create_table "personalities", force: :cascade do |t|
    t.string   "description"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
  end

end