Unique usernames in Devise for Rails

Question

I followed Devise's instructions for using usernames in addition to emails for logins. Works great except people can signup with duplicate usernames. If someone tries to signup with a duplicate email address, they are presented with this error message on the signup page:

1 error prohibited this user from being saved:

Email has already been taken

I want something very similar for usernames. How do I implement this?

Answer 1

You should use uniqueness validator. Add following into user.rb:

validates_uniqueness_of :username

more about this validator

Answer 2

Note that you probably want to make usernames unique, but also case-insensitive, so you don't end up with both username and Username:

class User < ApplicationRecord
  validates :username, presence: true, uniqueness: { case_sensitive: false }
  # Rest of user model
end

From the Devise wiki.