Ajax在设计Rails中

I am currently doing a project, and I am using Devise for the User Authentication. I have the before_action :authenticate_user!in my Post Controller. When I click new post without Signing in it redirects to the Log in Page. That's fine, But I want it to be as pop over(when I click the new post,the log in form must popover). How can I achieve this. I have also referred to this

Rails 4 Devise Login as a POPUP window

But, still when I clicked the new Post, it is redirecting to the sign in page. Help me with this issue, Thanks in advance.

I have this code in my Users::SessionsController < Devise::SessionsController is

class Users::SessionsController < Devise::SessionsController


respond_to :json

  def create
    session['user_auth'] = params[:user]
    resource = warden.authenticate!(:scope => resource_name, :recall => "#{controller_path}#failure")

sign_in(resource_name, resource)
message = I18n.t 'devise.sessions.signed_in'

yield resource if block_given?

if request.xhr?
 return render :json => {:success => true, :login => true, :data =>  {:message => message}}
else
  respond_with resource, location: after_sign_in_path_for(resource)
end


end

  def failure
    user = User.where(email: session['user_auth'][:email]).first rescue nil
    message = I18n.t 'devise.failure.invalid', authentication_keys: "email"

respond_to do |format|
  format.json {
    render :json => {:success => false, :data => {:message => message, :cause => 'invalid'} }
  }
  format.html {
    redirect_to '/users/sign_in'
  }
end


end
end