Count objects

count_objects_by_class.rb

module GC
  def self.count_objects_by_class
    @@runs ||= []
    run = Hash.new 0
    @@runs << run 

    # Count objects of each class.
    ObjectSpace.each_object do |obj|
      run[obj.class.name.to_sym] += 1
    end
    
    # List classes and number of them in each run.
    @@runs.map(&:keys).flatten.uniq.sort.each do |klass|
      puts "#{klass} #{@@runs.map {|r| r[klass] }}"
    end
  end
end