Rails：验证每个组中至少一个记录的属性存在

Question

I am trying to do something like:

validates :primary_product, presence: { scope: :student_id }

There can be multiple rows with same student_id . For set of all rows(with same student_id ) at least one value of primary_product should be present. This does not seem to work. Not sure if I can apply scope with presence.

Answer 1

You can try the following, using custom validation:

validates :primary_product, if: -> x {
  where.not(primary_product: nil).exists?(student_id: x.student_id)
}