UsersController
+ user : User+ article : Article
+ show()+ new()+ edit()+ index()+ destroy()+ create()+ update()- user_params()- admin_user?()
ActionController::Base
+ before_action()+ include()
ApplicationController
+ logged_in_user()- logged_in?()
SessionsHelper
+ log_in(User: user)+ current_user()+ logged_in?()+ forget(User: user)+ log_out()+ remember(User: user)+ current_user?(User: user)+ redirect_back_or(String: url)+ store_location()
