需要另一个特定模型的多对多对多关系

Question

我通过供应在超市、产品和品牌之间建立了多对多的关系-和 Origin-模型。 我还想存储我在超市中拥有的特定产品-品牌-组合。 我想到了另一个模型（我称之为Specific_Combination，我将在其中存储:supermarket_id、:product_id 和:brand_id。

class Supermarket < ActiveRecord::Base
  has_many :supplies
  has_many :products, :through => :supplies
end

class Supply < ActiveRecord::Base  
  belongs_to :product  
  belongs_to :supermarket  
end

class Product < ActiveRecord::Base
  has_many :supplies
  has_many :supermarkets, :through => :supplies

  has_many :origins
  has_many :brands, :through => :origins
end

class Origin < ActiveRecord::Base
  belongs_to :products
  belongs_to :brands
end

class Brand < ActiveRecord::Base
  has_many :origins
  has_many :products, :through => :origins
end

现在我认为可以用来存储特定产品-品牌组合的类

class Specific_Combination < ActiveRecord::Base
  # to show which columns I would use:
  attr_accessible :supermarket_id, :product_id, :brand_id
end

• 这是一种合适的方法吗？
• 如何对与Specific_Combination 之间的关系建模？
• 如何访问（创建...）Specific_Combination 中的项目？
• 更好的方法（标准化）应该是什么样子？

编辑

class Supply < ActiveRecord::Base  
  belongs_to :origin  
  belongs_to :supermarket  
end

class Product < ActiveRecord::Base
  has_many :origins
end

class Origin < ActiveRecord::Base
  belongs_to :product
  belongs_to :brands
end

class Brand < ActiveRecord::Base
  has_many :origins
end

class Supermarket < ActiveRecord::Base
  has_many :supplies
  has_many :origins, :through => :supplies

  # my attempt to create an array of names of supermarkets
    def self.to_be_chosen
      chosen_supermarket = Array.new
      Supermarket.find_each do |supermarket|
        chosen_supermarket << supermarket.name
      end
    return chosen_supermarket
    end
end

/编辑

Answer 1

在这里，我的供应可能属于原产地而不是产品。

另外，想想你是否需要SpecificCombination。你打算用它做什么操作？您要列出数据库中的所有特定组合吗？您要搜索以找到特定的吗？您要创建一个新组合吗？

然后想想这些操作是否可以通过其他类简单地完成？

class Supermarket < ActiveRecord::Base
  has_many :supplies
  has_many :origins, :through => :supplies

  def self.choice
    Supermarket.all.map { |supermarket| [ supermarket.name, supermarket.id ] }
  end
end

end

class Supply < ActiveRecord::Base  
  belongs_to :origin
  belongs_to :supermarket  
end

class Origin < ActiveRecord::Base
  belongs_to :supplies
  belongs_to :brands
end


walmart = Supermarket.create(:name => "Walmart");

cornflakes = Product.create(:name => "Corn Flakes");
kellogs = Brand.create(:name => "Kellog's");
walmart.origins.create(:product_id => cornflakes, :brand_id = kellogs)