class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception
  before_action :configure_permitted_parameters, if: :devise_controller?
  before_action :authenticate_user!, except: [:home]

  protected

    def configure_permitted_parameters
      devise_parameter_sanitizer.permit(:sign_up, keys: [:username])
    end
end

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception
  before_action :configure_permitted_parameters, if: :devise_controller?
  before_action :authenticate_user!, except: [:home]

  helper_method :correct_user

  def correct_user
    !!(current_user == @resource.user)
  end

  protected

    def configure_permitted_parameters
      devise_parameter_sanitizer.permit(:sign_up, keys: [:username])
    end
end

Add correct_user method as controller method and helper.
Add correct_user method as controller method and helper.
