Rails .where() 属性不为空

Question

我有一个 Page 模型，其中包含许多 Section 模型，这些模型与 SectionRevision 到 current_revision 相关联。从Page 模型中，我尝试选择所有Sections，其中current_revision.parent_section_id 不为零。

Section模特：

class Section < ActiveRecord::Base
  belongs_to :page
  has_many :revisions, :class_name => 'SectionRevision', :foreign_key => 'section_id'
  has_many :references

  has_many :revisions, :class_name => 'SectionRevision', 
                       :foreign_key => 'section_id'
  belongs_to :current_revision, :class_name => 'SectionRevision', :foreign_key => 'current_revision_id'

  delegate :position, to: :current_revision

  def set_current_revision
    self.current_revision = self.revisions.order('created_at DESC').first
  end

  def children
    Section.includes(:current_revision).where(:section_revisions => {:parent_section_id => self.id})
  end
end

还有Page模特：

class Page < ActiveRecord::Base
  belongs_to :parent, :class_name => 'Page', :foreign_key => 'parent_page_id'
  has_many :children, :class_name => 'Page', :foreign_key => 'parent_page_id'
  belongs_to :page_image, :class_name => 'Image', :foreign_key => 'page_image_id'
  has_many :sections

  validates_uniqueness_of :title, :case_sensitive => false

  def top_level_sections
    self.sections.includes(:current_revision).where(:section_revisions => {:parent_section_id => "IS NOT NULL"})
  end

end

---

Page.top_level_sections 是基于：Rails where condition using NOT NULL 编写的，当前生成一个空数组。它不能正确检测“parent_section_id”是否不为空。

如何正确写Page.top_level_sections？

Answer 1

试试这个：

self.sections.includes(:current_revision).
  where("section_revisions.parent_secti‌​on_id IS NOT NULL")