选择产品子产品和子子产品的最有效方法是什么？自指 has_and_belongs_to_many 关联

Question

我正在制作物料清单申请。 一个产品可以是许多组件的一部分，并且有许多 sub_products。 我有以下型号：

models/product.rb
has_many :sub_structure, primary_key: "produktnr", class_name: "Structure", foreign_key: "produktnr"
has_many :sub_products, through: :sub_structure, source: :product
has_many :structures, primary_key: "produktnr", class_name: "Structure", foreign_key: "delproduktnr"
has_many :assemblies, through: :structures, source: :assemblie

models/structre.rb
belongs_to :assemblie, primary_key: "produktnr", class_name: "Product", foreign_key: "produktnr"
belongs_to :product, primary_key: "produktnr", class_name: "Product", foreign_key: "delproduktnr"

选择所有子产品很容易：

@product.sub_products

但是选择子产品并且它们是子产品的最有效方法是什么？

类似：

@product.sub_products.sub_products

Answer 1

我肯定知道有更好更合适的方法，但我前几天遇到了同样的问题，我知道这不漂亮，我必须适应你的情况，我没有测试，但你去：

class Product
  @@all_products = nil

  def self.all_products
    @@all_products
  end

  #You will have to call this right before getting the children products
  def self.cache_products
    if defined? @@all_products && @@all_products.nil?
      @@all_products = ActiveSupport::Cache::MemoryStore.new(expires_in: 5.minutes)
      list = Product.all.ordered.pluck(:id, :name, :parent_id)
      product_instances = []
      list.each {|n|
        p = Product.new
        p.id = n.first
        p.name = n.second
        p.parent_id = n.third
        product_instances << p
      }
      @@all_products.write('products', product_instances)
    end
    @@all_products.read('products').select{|c| c.parent_id == nil}
  end

  def self.get_children(products)
    children = []
    products.each do |p|
      children += Product.all_products.read('products').select { |j| p.id == j.parent_id }}
    end
    children
  end

  def self.products_with_no_children
    Product.where("id NOT IN (#{Product.all.pluck(:parent_id)})")
  end
end