Is_Unique validation with custom db table

[eluser]wehappyfew[/eluser]
It seems off topic because I was asking a way to "extend" somehow the is_unique validation so as someone to be able to add a variable inside its arguments to specify a custom table,which would be generated automatically when the new user would be created.

You on the other hand should look more closely the examples of the user guide. The $db variable in the first case is causing the problem.Check if you use it somewhere without having pass it first.
Your syntax seems alright.
The use of the is_unique validation is really straightforward.