How to authenticate an access token in rails? - ruby-on-rails

Question

I have this code in my ApplicationController
class ApplicationController < ActionController::Base
protect_from_forgery with: :exception
def authenticate!
# unless current_user
if current_user
current_user
else
render json: { 'error' => {'message' => 'Invalid access token', 'code' => 301 } }
return
end
end
def current_user
return #current_user if #current_user.present?
user = User.find_by(access_token: params.delete(:token))
if user.present?
#current_user = user
else
false
end
end
end
and I authenticate a user with
class Api::V1::RegisterController < ApplicationController
layout nil
skip_before_action :verify_authenticity_token
def get_user
authenticate!
render json: {'hello' => 'hi'}
end
end
it throws me an error of Double Render.
how can I render an invalid access token message if user's access token is not present in my database and return user details if present?
EDIT1: I tried the code provided by #andrew21
class ApplicationController < ActionController::Base
class UnauthorizedAccess < StandardError; end
rescue_from UnauthroizedAccess, with: render_invalid_access
protect_from_forgery with: :exception
def authenticate!
raise UnauthorizedAccess, 'invalid access token' unless current_user
end
def render_invalid_access
render json: { 'error' => {'message' => 'Invalid access token', 'code' => 301 } }
end
end
but I get an error.
undefined local variable or method `render_invalid_access' for ApplicationController:Class

Answer 1

why don't you raise an error on invalid access, then rescue the error and render the appropriate response. e.g.:
class ApplicationController < ActionController::Base
class UnauthorizedAccess < StandardError; end
protect_from_forgery with: :exception
rescue_from UnauthorizedAccess, with: :render_invalid_access
def authenticate!
raise UnauthorizedAccess, 'invalid access token' unless current_user
end
def render_invalid_access
render json: { 'error' => {'message' => 'Invalid access token', 'code' => 301 } }
end
end