Rails范围过滤元素没有has_many关联元素

Posted 2021-05-06

我有以下型号：

class Property < ActiveRecord::Base
    has_many :photos
    scope :no_photos, -> { where('properties.id NOT IN (SELECT DISTINCT(property_id) FROM photos)') }
end

class Photo < ActiveRecord::Base
    belongs_to :property
end

我知道我的范围非常低效。我需要另一种方法来获取没有任何相关照片的属性。

有帮助吗？

答案

您可以执行以下操作：

class Property < ActiveRecord::Base
  has_many :photos
  scope :has_no_photo, includes(:photos).where(photos: { id: nil })
  scope :has_photo, includes(:photos).where('photos.id IS NOT NULL')
  # rails 4 or higher (thanks to @trip)
  scope :has_photo, includes(:photos).where.not(photos: { id: nil })

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