fuck.rb

class Product < ActiveRecord::Base
  has_many :products_materials
  has_many :materials, :through => :products_materials
end


class Material < ActiveRecord::Base
  has_many :products_materials
  has_many :products, :through => :products_materials
end


class ProductsMaterial < ActiveRecord::Base
  belongs_to :product
  belongs_to :material
end

well i tried copying your above example line for liine but kept getting:

1.9.3-p0 :020 > p = Product.first
Product Load (28.6ms) SELECT "products".* FROM "products" LIMIT 1
=> #<Product id: 1, title: "teddy", created_at: "2012-02-25 04:28:14", updated_at: "2012-02-25 04:28:14">
1.9.3-p0 :021 > p.materials
NameError: uninitialized constant Product::ProductsMaterial

hmm, must be something simple