How to Validate Uniqueness Of a Record within Date Range

Rails
1

I would like to validate the uniqueness of a record within a date range.

For example : I want a customer attached to a post office within a date
range arrives(date) and departs (date).

So this is ok:
customer1; postoffice1; Feb1(arrives);Mar1(departs)
customer1; postoffice1; Mar2(arrives);Apr1(departs)

This however is NOT ok:
customer1; postoffice1; Feb1(arrives);Mar1(departs)
customer1; postoffice1; Jan1(arrives);Feb10(departs) [xxx overlapping
dates xxx]

The validation clause for this would be?

? validates_uniqueness_of :customer_id, :scope =>
[:postoffice_id,:arrives,:departs], :message=>“This unit with this
arrival date for this PSO already exists.”
?

I dont think the above is right? How do I specify range within scope.

2

I don’t see a way for you to combine the high-level validations to do
what
you want. However, you can overwrite the validate method to do what you
want.

class SomeModel < ActiveRecord::Base
def validate
#custom validation here
end
end

See
http://www.railsbrain.com/api/edge/doc/index.html?a=C00000457&name=Validations,
which shows an example Person model that uses the high-level
validations
and overwrites validate. It also shows how to add errors if your custom
validation fails.

Regards,
Craig