just for fun.... converted it into 1 line

news_letters_controller.rb

class NewsLettersController < ApplicationController  
def send_news_letter
    #if params[:send_news_letter][:email].present?
     # @user = User.new params[:send_news_letter]
     # @user.save validate: false
     # Notifier.send_news_letter(@user).deliver
     # redirect_to root_path, notice: "Thanks for sharing. We'll keep you in the loop!"
    #else
      #redirect_to root_path, error: "Please provide your email for the newsletter."
      redirect_to *lambda {lambda{ @user = User.new( params[:send_news_letter]); @user.save(validate: false); Notifier.send_news_letter(@user).deliver  }.call  if params[:send_news_letter][:email].present? ; return [root_path, (params[:send_news_letter][:email].present? ? { notice: "Thanks for sharing. We'll keep you in the loop!" } : {error: "Please provide your email for the news letter!"})] }.call
    #end
  end
end