Rails ActiveRecord custom validator returns false but model.save is accepted without rollback - ruby-on-rails

Question

i have a model which defines size ranges like 100m² to 200m². I wrote a validator:
class SizeRange < ActiveRecord::Base
validate :non_overlapping
def non_overlapping
lower_in_range = SizeRange.where(lower_bound: lower_bound..upper_bound)
upper_in_range = SizeRange.where(upper_bound: lower_bound..upper_bound)
if lower_in_range.present?
errors.add(:lower_bound, 'blablabla')
end
if upper_in_range.present?
errors.add(:upper_bound, 'blablabla')
end
end
end
My guess was, that when I try to save a new model which lower or upper bound appears to be in the range of an other SizeRange instance the validator would mark the model as invalid and the save action would be aborted.
What really happened is that my model got saved and assigned an id, but when I call model.valid? it returns false (So my validator seems to do what it should).
Is there anything I could have done wrong, or did I not understand how the validators work? Can I force the validator to abort the save action?
Another question:
Is there any way to enforce a constraint like that through database constraints? I think I would prefer a solution on database side.
Thanks for your help!

Answer 1

model.save
would be accepted silently and return false. It will not throw any Exception.
You should call:
model.save!
to fail with validations

Answer 2

You should return false after each errors.add to cancel the record saving

Answer 3

Turns out the problem was my not well-formed validator function.
The case I checked an which led to confusion:
SizeRange from 200 to 400 already in the database
Creating a new one between 200 and 400 like SizeRange.new({:lower_bound=>250, :upper_bound=>350})
So I expected that to be invalid (model.valid? -> false) but it was, of course, valid. So model.save did no rollback and AFTER that I tested on model.valid? which would NOW return false, as the newly saved instance would violate the constraint, because it was tested against itself.
So there were two problems:
model.valid? would also test against the same instance if it already had an id
the validator would not validate what I thought it would
So I ended up rewriting my validator function:
def non_overlapping
sr = id.present? ? SizeRange.where.not(id: id) : SizeRange
ranges = sr.all
lower_overlappings = ranges.map { |r| lower_bound.between?(r.lower_bound, r.upper_bound)}
upper_overlappings = ranges.map { |r| upper_bound.between?(r.lower_bound, r.upper_bound)}
if lower_overlappings.any?
errors.add(:lower_bound, 'lower bla bla')
end
if upper_overlappings.any?
errors.add(:lower_bound, 'upper bla bla')
end
end
The first line handles the first problem and the rest handles the intended validation.
Thanks for your help and sorry for the confusion.

Answer 4

You should be using begin and rescue:
class SizeRange < ActiveRecord::Base
validate :non_overlapping
private
def non_overlapping
lower_in_range = SizeRange.where(lower_bound: lower_bound..upper_bound)
upper_in_range = SizeRange.where(upper_bound: lower_bound..upper_bound)
begin
raise("Lower Bound Met!") if lower_in_range.present?
rescue => ex
errors.add(:lower_bound, "#{ex.message} (#{ex.class})")
end
begin
raise("Lower Bound Met!") if upper_in_range.present?
rescue => ex
errors.add(:upper_bound, "#{ex.message} (#{ex.class})")
end
end
end