Rails Route based on something different than ID

Another possibility to consider would be the friendly_id gem - https://github.com/norman/friendly_id

You need is to override to_param method in User model:

class User
  def to_param
   username
  end
end

Then rails will use it automagically for routing. See http://api.rubyonrails.org/classes/ActiveRecord/Base.html#method-i-to_param