Rails .where()属性IS NOT NULL

Question

我有一个Page包含许多Section模型的模型,它与一个SectionRevision通过相关联current_revision.从Page模型我想选择所有Sections在current_revision.parent_section_id不为零.

Section 模型:

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

和Page型号:

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是基于以下内容编写的:Rails,其中条件使用NOT NULL并且当前生成一个空数组.它无法正确检测"parent_section_id"是否为空.

我怎么写得Page.top_level_sections正确？

Answer 1

试试这个:

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