CSV streamer

csv_streamer.rb

# controller method

def csv_export
  respond_to do |format|
    format.csv {
      @filename = "responses-#{Date.today.to_s(:db)}.csv"
      self.response.headers["Content-Type"] ||= 'text/csv'
      self.response.headers["Content-Disposition"] = "attachment; filename=#{@filename}"
      self.response.headers['Last-Modified'] = Time.now.ctime.to_s

      self.response_body = Enumerator.new do |y|
        i = 0
        Model.find_each do |m|
          if i == 0
            y << Model.csv_header.to_csv
          end
          y << sr.csv_array.to_csv
          i = i+1
          GC.start if i%500==0
        end
      end
    }
  end
end


# model.rb

 def self.csv_header
    ["ID", "Route", "username"]
  end

  def csv_array
    [id, route, username]
  end

# model.rb (outra versao)

attr_reader :records, :event, :titles, :attribs

  def initialize(records, event, titles, attribs)
    @event = event
    @records = records
    @titles = titles
    @attribs = attribs
  end
  
  def each
    yield CSV.generate_line(titles)
    records.each do |r|
      yield csv_row(r)
    end    
  end
  
  def csv_row(r)
    CSV.generate_line(attribs.map{|a| a.call(r,event)})
  end


# response headers
self.response.headers["Content-Type"] = "application/octet-stream" 
self.response.headers["Content-Disposition"] = "attachment; filename=#{filename}"
self.response.headers['Last-Modified'] = Time.now.ctime.to_s