确保集合中的一个对象为true,并将其他对象设置为false

我有一个布尔属性的类, primary

validates_uniqueness_of :primary, if: :primary, scope: [:restaurant_id]

最近,我想自定义writer方法,使其在将当前实例在集合中的同级设置为false(如果实例为true)时分配当前实例的新值。尽管如此,我的测试还是失败了:

 MenuGroup did not properly validate that :primary is case-sensitively
       unique within the scope of :restaurant_id.
         After taking the given MenuGroup, setting its :primary to ‹"an
         arbitrary value"› (read back as ‹true›), and saving it as the existing
         record, then making a new MenuGroup and setting its :primary to a
         different value, ‹true› and its :restaurant_id to a different value,
         ‹nil›, the matcher expected the new MenuGroup to be invalid, but it
         was valid instead.

这是测试:

it { should validate_uniqueness_of(:primary).scoped_to([:restaurant_id]) }

class MenuGroup < ApplicationRecord
  belongs_to :restaurant

  validates_uniqueness_of :primary, if: :primary, scope: [:restaurant_id]

  def primary=(primary)
    if primary?
      MenuGroup
       .where.not(id: self.id)
       .where(restaurant_id: self.restaurant_id).update_all(primary: false)
    end

    write_attribute :primary, primary
  end
end