bad_design.rb

require "csv"

class AwesomeCsvReader
  def initialize(importer)
    @importer = importer
  end

  def read
    CSV.foreach "large.csv" do |line|
      @importer.import line
    end
  end
end

class AwesomeRecordImporter
  def import(datum)
    puts "Imported #{datum.inspect}"
  end
end

importer = AwesomeRecordImporter.new
reader = AwesomeCsvReader.new importer

reader.read

memory_hog.rb

require "csv"

class AwesomeCsvReader
  def read
    CSV.read "large.csv"
  end
end

class AwesomeRecordImporter
  def import(data)
    data.each do |datum|
      puts "Imported #{datum.inspect}"
    end
  end
end

reader = AwesomeCsvReader.new
importer = AwesomeRecordImporter.new

importer.import reader.read

memory_smart.rb

require "csv"

class AwesomeCsvReader
  def read
    CSV.enum_for :foreach, "large.csv"
  end
end

class AwesomeRecordImporter
  def import(data)
    data.each do |datum|
      puts "Imported #{datum.inspect}"
    end
  end
end

reader = AwesomeCsvReader.new
importer = AwesomeRecordImporter.new

importer.import reader.read

recover_errors.rb

def import_data_source
  data = [
    :good_data,
    :bad_data,
    :good_data
  ]
  Enumerator.new do |yielder|
    data.each do |data|
      begin
        yielder << data
      rescue
      end
    end
  end
end

def import(data)
  raise "Error!" if data == :bad_data
  puts "Successfully imported #{data}"
end

import_data_source.each do |data|
  import data
end