Rails - 基於孫子屬性創建範圍

Question

我正在嘗試爲基於孫子狀態的類創建範圍。

我有一個佐賀課程，裏面有許多故事，其中有許多章節，我希望佐賀有一個範圍，只有故事中的章節有傳說。 Chapter.published是一個布爾值

class Saga < ActiveRecord::Base 
    has_many :stories, -> { order(:order) } 

    def self.default_scope 
    end 
end 

class Story < ActiveRecord::Base 
    belongs_to :saga 
    has_many :chapters, -> { order(:order) } 

    def self.default_scope 
    where(saga_id: nil) 
    lambda{ where('EXISTS (SELECT 1 FROM chapters WHERE chapters.published = 1 AND chapters.story_id = stories.id)') } 
    end 
end 

class Chapter < ActiveRecord::Base 
    belongs_to :story 

    def self.default_scope 
    where(published: true) 
    end 

end 

感謝您的幫助！

Answer 1

嘗試使用ActiveRecord的.joins()方法：

class Saga < ActiveRecord::Base 
    ... 
    scope :has_published_chapter, -> { 
    joins(stories: :chapters).where("chapters.published IS TRUE") 
    }