Rails模型反向验证的唯一性

Question

I have rails model with two attributes :ticket_id and :parent_ticket_id . I want to validate such that there is only record having these two values. For example,

There should be one and only record with 4 and 1

:ticket_id => 4, :parent_ticket_id => 1

And I don't want any more rows having these same two values in any combination. Nothing of the sort (1,4) or (4,1).

will validates :ticket_id, :uniqueness => true, :scope => :parent_ticket_id work? I guess this will prevent just (1,4) combination and not (4,1)..

Answer 1

You can do this in a custom validator (this query looks both ways in one query versus Salil using two different queries to do it):

validate :ticket_and_parent_ticket_are_unique

private
  def ticket_and_parent_ticket_are_unique
    errors.add(:base, 'They are not unique') if ModelName.exists?(:ticket_id => [self.ticket_id, self.parent_ticket_id], :parent_ticket_id => [self.ticket_id, self.parent_ticket_id])
  end

Answer 2

I don't think this is present in Rails, you have to write your own something like following

validate :some_method_name

def some_method_name
  if ModelName.exists?(:ticket_id => self.ticket_id, :parent_ticket_id => self.parent_ticket_id) || ModelName.exists?(:ticket_id => self.parent_ticket_id , :parent_ticket_id => self.ticket_id)
    self.errors.add :base, '<Your ERROR Message Here>'
  end
end

No Check though