gistfile1.rb

require "delegate"  
  
class CollectionProxy  
  def products
    @products                  ||= HasManyAssociation.new([])  
    @products.associated_class ||= Product  
    @products
  end  
end  
  
class Product  
  def initialize(attributes)  
    @attributes = attributes  
  end  
  
  attr_reader :attributes
  
  def name  
    attributes[:name]
  end  
end  


# -----------------------------------------------------------
# With DelegateClass
# -----------------------------------------------------------
class HasManyAssociation < DelegateClass(Array)
  attr_accessor :associated_class

  def initialize(array)
    super(array)
  end

  def create(params)
    self << associated_class.new(params)
  end
end

proxy = CollectionProxy.new  
products = proxy.products  
products.create(:name => 'products one')  
products.create(:name => 'products two')  
p products[0].name
p products[1].name
p products.map { |q| q.name }
# -----------------------------------------------------------
# with method_missing
# -----------------------------------------------------------
class HasManyAssociation < BasicObject  
  attr_accessor :associated_class  
  
  def initialize(array)  
    @array = array  
  end  
  
  def create(params)  
    self << associated_class.new(params)  
  end  
  
  def method_missing(*a, &b)  
    @array.send(*a, &b)  
  end  
end  

proxy = CollectionProxy.new  
products = proxy.products  
products.create(:name => 'products one')  
products.create(:name => 'products two')  

p products.map { |q| q.name }