ruby – ActiveRecord – 在连接模型中查找具有共享属性的所有对

发布时间：2020-12-16 23:10:16 所属栏目：百科来源：网络整理

导读：我有三个型号 class Boat ActiveRecord::Base belongs_to :captain has_many :boat_classifications has_many :classifications,through: :boat_classificationsendclass Classification ActiveRecord::Base has_many :boat_classifications has_many :boats

我有三个型号

class Boat < ActiveRecord::Base
  belongs_to  :captain
  has_many    :boat_classifications
  has_many    :classifications,through: :boat_classifications
end

class Classification < ActiveRecord::Base
  has_many :boat_classifications
  has_many :boats,through: :boat_classifications
end

class BoatClassification < ActiveRecord::Base
  belongs_to :boat
  belongs_to :classification
end

我正在尝试编写一个简单的ActiveRecord查询来查找所有类型帆船的船只.类似于Boat.where(分类：“帆船”)

解决方法

我认为这可行：

Boat.joins(:classifications).where(classifications: { name: 'Sailboat' }) # name or whatever field contains Sailboat

生成此查询：

SELECT `boats`.* FROM `boats` INNER JOIN `boat_classifications` ON `boat_classifications`.`boat_id` = `boats`.`id` INNER JOIN `classifications` ON `classifications`.`id` = `boat_classifications`.`classification_id` WHERE `classification`.`name` = 'Sailboat'

（编辑：李大同）

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