Login with email or username

new.html.erb

<%= form_tag :login do %>
  <%= label_tag :login, "Email or Username" %>
  <%= text_field_tag :login %>
  <%= submit_tag "Log In" %>
<% end %>

sessions_controller.rb

class SessionsController < ApplicationController
  def create
    user = User.find_by_login(params[:login])
    
    if user.try(:authenticate, params[:password])
      session[:user_id] = user.id
      redirect_to root_url
    else
      flash.now.alert = 'Wrong login/password combination'
      render :new
    end
  end
end

user.rb

class User < ActiveRecord::Base
  has_secure_password
  
  validates_presence_of   :username, :email
  validates_uniqueness_of :username, :email
  
  before_save ->{ email.downcase! }, if: :email_changed?
  before_save ->{ username.downcase! }, if: :username_changed?
  
  def self.find_by_login(login)
    column = login =~ /@/ ? :email : :username
    find_by(column => login.downcase)
  end
  
  # before_validation :format_logins

  # def self.find_by_login(login)
  #   where(
  #     "#{table_name}.email = :login OR
  #      #{table_name}.username = :login",
  #     login: login.downcase
  #   ).take
  # end
  
  # def self.find_by_login(login)
  #   login.downcase!
  #   where(
  #     arel_table[:email].eq(login).or
  #     arel_table[:username].eq(login)
  #   ).take
  # end
  
# private

  # def format_logins
  #   downcase_email if email_changed?
  #   downcase_username if username_changed?
  # end
  
  # def format_logins
  #   [:email, :username].each do |login|
  #     public_send("#{login}=", public_send(login).downcase) if public_send("#{login}_changed?")
  #   end
  # end
end