Rails 3: Generate unique codes (coupons)

In Ruby's standard library there is SecureRandom for this:

SecureRandom.hex(3)

The length of the output is double of what the length input specified.

What you want is to generate a GUID. See here:

guid generator in ruby

You can do something like this too:

chars = ('a'..'z').to_a + ('A'..'Z').to_a
def String.random_alphanumeric(size=16)
    (0...size).collect { chars[Kernel.rand(chars.length)] }.join
end

But then you would have to compare against a database to make sure it is not used yet.

Maybe try this, seems to be more proof than just generating some random key. They say: UUID generator for producing universally unique identifiers based on RFC 4122 (http://www.ietf.org/rfc/rfc4122.txt). http://rubygems.org/gems/uuid

gem install uuid
cd /myproject/path
uuid-setup

In your code

require_gem 'uuid'
my_unique_id_var = UUID.new

Reference: http://railsforum.com/viewtopic.php?id=12616#p44545