Ruby on rails 如何返回嵌套资源的ActiveRecord关系

我有一门文章课

class Article < ActiveRecord::Base
    belongs_to :category
end

and Category class

class Category < ActiveRecord::Base
    has_many :articles
    has_many :categories
    belongs_to :category
end

所以，如果一个用户想要搜索政治，本地和世界都应该在桌面上，当他想要运动的时候，我们会搜索足球，业余和职业拳击。

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我的问题是，我如何编写一个方法/范围来返回所有类别在所选类别下的文章？请记住，我打算稍后使用ThinkingSphinx，因此它不可能是一个简单的数组，我需要ActiveRecord关系。

您可以递归地将类别和子类别ID放入单个数组，然后在“where”子句中使用“IN”语句，如下所示：

class Category < ActiveRecord::Base

  ...

  def all_subcategory_ids
    cat_ids = []
    cat_ids << self.id
    self.categories.each do |category|
      cat_ids << category.id
      cat_ids << category.all_subcategory_ids
    end
    #since we have a mixed array of ids and sub-arrays, we need to flatten
    #the cat_ids array so it is just a one-dimensional array of ids [Ruby Array#flatten](http://ruby-doc.org/core-2.0.0/Array.html#method-i-flatten) 
    cat_ids.flatten
  end
end  

类别cat_id您可以递归地将类别和子类别id放入单个数组，然后在“where”子句中使用“IN”语句，如下所示：

class Category < ActiveRecord::Base

  ...

  def all_subcategory_ids
    cat_ids = []
    cat_ids << self.id
    self.categories.each do |category|
      cat_ids << category.id
      cat_ids << category.all_subcategory_ids
    end
    #since we have a mixed array of ids and sub-arrays, we need to flatten
    #the cat_ids array so it is just a one-dimensional array of ids [Ruby Array#flatten](http://ruby-doc.org/core-2.0.0/Array.html#method-i-flatten) 
    cat_ids.flatten
  end
end  

类别class Article < ActiveRecord::Base

  ...

  def self.in_category_and_subcategories(category)
    Article.where("category_id IN (?)", category.all_subcategory_ids)
  end
end