Question

我有类别和规范模型以及通过CategoriesSpecifications表的多对多关联，如下所示：

create_table :categories_specifications, id: false do |t|
   t.belongs_to :specification, null: false
   t.belongs_to :category, null: false
   t.integer :status, null: false, default: 0
end

通过类别

选择所有规格的最佳做法和最短路径是什么

Answer 1

@category = Category.first
@category.specifications # this is the shortest way to select all specifications via Category

确保在模型中声明关联：

class Category < ActiveRecord::Base
  has_many :categories_specifications
  has_many :specifications, through: :categories_specifications
end

class Specification < ActiveRecord::Base
  has_many :categories_specifications
  has_many :categories, through: :categories_specifications
end

class CategoriesSpecification < ActiveRecord::Base
  belongs_to :category
  belongs_to :specification
end

推荐阅读： http://guides.rubyonrails.org/association_basics.html

Answer 2

假设您有以下内容：

class Category < ActiveRecord::Base
  has_many :specifications
  has_many :categories, :through => :categories_specifications
end

class CategoriesSpecification < ActiveRecord::Base
  belongs_to :category
  belongs_to :specification
end

class Specification < ActiveRecord::Base
  has_many :categories_specifications
  has_many :categories, :through => :categories_specifications
end

您可以简单地找到category，然后选择所有specifications：

Category.find(1).specifications

RoR很多很多协会

2 个答案: