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

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

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

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： Rails where 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”是否不为空。

如何正确书写

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")

Answer 2

这些天你会使用：

scope :top_level_sections, lambda {
  sections
    .includes(:current_revision)
    .where.not(section_revisions: {parent_section_id: nil})
}