gistfile1.rb

class Material < ActiveRecord::Base
  has_many :product_materials
  has_many :products, :through => :product_materials
  
  #validates :title, presence: true
end

class Product < ActiveRecord::Base
  has_many :product_materials
  has_many :materials, :through => :product_materials
  
  #validates :title, presence: true
end


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