Validating the uniqueness of the combination of two fields

Rails
1

Is there a built-in method to validate that two fields in combination
are unique?

e.g. if my table is :

username | password

user1 | pass1

the following happens

MyObject.new(username=>“user1”,password=>“pass2”) => ok
MyObject.new(username=>“user2”,password=>“pass1”) => ok
MyObject.new(username=>“user1”,password=>“pass1”) => not ok

Thanks

2

I am interested in this too. Does anybody have any ideas?

3

validates_uniqueness_of :username, :scope => :password

http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html#M000944

(this is an extra query. You could write a unique index and rescue the
exception).