Count all Rails models

print_count.rb

class PrintCount
  def diff
    before = count_all_models_with_table
    after = if block_given?
      yield
      count_all_models_with_table
    else
      Hash.new(0)
    end
    print_diff(before, after)
  end

  private

  def models_with_table
    ActiveRecord::Base.connection.tables.map do |x|
      x.classify.safe_constantize
    end.compact
  end


  def count_all_models_with_table
    models_with_table.each_with_object(Hash.new(0)) do |klass, collection|
      collection[klass.name] = if klass.respond_to? :with_deleted
                                 klass.with_deleted.count
                               else
                                 klass.count
                               end
    end
  end

  def print_diff(before, after)
    before.keys.each do |key|
      next if before[key] == after[key]

      diff = before[key] - after[key]
      Rails.logger.warn("#{key}: #{diff}")
    end
  end
end