gistfile1.rb

Enumerable.module_eval do
  def select_by(attribute_name, value)
    detect do |item|
      item.send(attribute_name) == value
    end
  end

  def select_by!(attribute_name, value)
    select_by(attribute_name, value) \
      or raise StandardError.new("can't find item with #{attribute_name} equal to #{value} in #{self.inspect}")
  end
end