gistfile1.rb

require 'date'

module Stats
  class << self
    def calculate_stats(model, date_from = Date.today - 7, date_to = Date.today)
      process_tracks(date_from, date_to).map do |track|
        # Bar.get_stats_hash(track)
        track
      end
    end
    
    private

    def process_tracks(date_from, date_to)
      # tracks = Track.all
      # (...)
      %w(some useful and important stats)
    end
  end
end

# Stats.calculate_stats(Campaign, params[:date_from], params[:date_to])



class StatsClass
  def initialize(model, date_from = Date.today - 7, date_to = Date.today)
    @model = model
    @date_from = date_from
    @date_to = date_to
  end

  def calculate_stats
    @stats ||= process_tracks.map do |track|
      # Bar.get_stats_hash(track)
      track
    end
  end

  private

  def process_tracks
    # tracks = Track.all
    # (...)
    %w(some useful and important stats)
  end
end

# StatsClass.new(Campaign, parmas[:date_from], params[:date_to]).calculate_stats