tags.rb

class items
  has_many :tags, through: :item_tags
  has_many :item_tags
  belongs_to :city
end

class cities
  has_many_ :items
end

class tags
  has_many :items, through: :item_tags
  has_many :item_tags
  
  def top_five_cities
    h = {}
    self.items.each do |i|
      h[i.city] ||= 1
      h[i.city] += 1
    end
    # sort will arrange our cities in ASC order, reverse it and take the first five... (would like to use .first(5) here)
    top_five = h.sort_by{|k,v| v}.reverse[0..5]
    cities = top_five.keys.map(&:to_s)
  end
end

class item_tags # join table
  belongs_to :tags
  belongs_to :items
end