根据其他模型中的条件获取记录

Question

有文章和评论。评论属于文章。目标是在发布的文章上发布所有评论。

class Article < ActiveRecord::Base
  has_many :comments

  # published
  def self.is_published
    where(published: true)
  end

class Comment < ActiveRecord::Base
  belongs_to :article

  def method_name
    # get all comments where article.is_published
  end
end

现在在控制器中使用它：

@comments = Comment.method_name.order("created_at desc")

Answer 1

您可以使用范围执行此操作。利用ActiveRecord#merge来避免重复条款发布的条件。

class Comment < ActiveRecord::Base
  belongs_to :article

  def self.published_only
    joins(:article).
      merge(Article.is_published)
  end
end

使用它看起来像

@comments = Comment.published_only.order(created_at: :desc)