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。在Page模型中，我尝试选择Sections不为零的所有current_revision.parent_section_id。

Section型号：

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

Page模型：

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基于：Rails where condition using NOT NULL编写，目前生成一个空数组。它无法正确检测“parent_section_id”是否为空。

如何正确撰写Page.top_level_sections？

Answer 1

试试这个：

self.sections.includes(:current_revision).
  where("section_revisions.parent_secti‌on_id IS NOT NULL")

Rails .where（）属性IS NOT NULL

1 个答案: