Composition and delegation

gistfile1.rb

# WheelType knows about the behavior of wheels
class WheelType
  def diameter
    #snip
  end

  def rim_size
    #snip
  end

  def weight
    #snip
  end
end

class Bicycle
  attr_accessor :wheel_type
  def initialize options = {}
    #do some stuff
    self.wheel_type = WheelType.new options
  end

  def rim_size
    #delegate to wheel_type
    wheel_type.rim_size
  end

  # add other delegate methods for 
  # wheel weight diameter, behavior

end