例如model将是UserEmail.

class UserEmail < ActiveRecord::Base
    belongs_to :user
end
 
class User < ActiveRecord::Base
    has_many :user_emails
end

并覆盖devise的方法在用户模型中查找记录：

def self.find_first_by_auth_conditions(warden_conditions)
  conditions = warden_conditions.dup
  if email = conditions.delete(:email)
    User.includes(:user_emails).where('user_emails.email = ?',email).first
  else
    super(warden_conditions)
  end

阅读更多关于覆盖在这里：https://github.com/plataformatec/devise/wiki/How-To:-Allow-users-to-sign-in-using-their-username-or-email-address