Question

validates_format_of            :order_of_importance, :on => :create, :with => /^[1-3]{3}$/,
                             :message => "Order of Importance must have 3 Digits"

Right now I have it validating that the numbers used are either 1, 2, 3, but I want to also make sure that those numbers are not only used, but that each one is used only once.

For example:

Should be working numbers

2 3 1

1 3 2

1 2 3

Should not be working numbers:

1 1 2

2 2 1

3 3 3

Answer 1

Isn’t it easier to check against all 3! valid permutations?

Edit:

But to take you up on the challenge:
(?:1(?!\d*1)|2(?!\d*2)|3(?!\d*3)){3}

It uses negative lookaheads to make sure numbers are picked only once.

Edit:

Checked with rubular.com.