To practice my rails skills, I decided to make a website about events. It is a website mainly between organizations, who hold an event and volunteers, who join the event.

Among all the problems I encountered, I want to share the DoubleRenderError because it bothered me for a long time and how I solve the problem.

Problem

I got this error when I tried to add some helpers method for the show route of User. My application_controller.rb looks like this:

class ApplicationController < ActionController::Base

    def current_user
      User.find_by :id=>session[:user_id]
    end
    def log_in?
      !!session[:user_id]
    end
    def log_in_first
        if !log_in?
          flash[:error]="You have to log in first to continue your               operation"
          redirect_to "/login"
        end
      end
      def correct_user?
        if !(current_user.id==@user.id)
         flash[:error]="You have no right to do this operation."
          redirect_to "/"
        end
      end
end

And here’s my show action in users_controller.rb:

def show
   log_in_first
   @user = User.find_by id: params[:id]
   correct_user?
   if @user
      render 'show'
     else
       redirect_to '/login'
   end
end

As you can see, I tried to verify that the user is logged in and it is the correct user before a user can browse on a specific user page. So let’s say if someone’s not logged in but wants to go to the show route, it will be redirected to the login page when it hits the log_in_first method, and see the error message: “You have to log in first to continue your operation”.

However, when I tested it as a not-logged-in user, I got this error:

AbstractController::DoubleRenderError (Render and/or redirect were called multiple times in this action. Please note that you may only call render OR redirect, and at most once per action. Also note that neither redirect nor render terminate execution of the action, so if you want to exit an action after redirecting, you need to do something like "redirect_to(...) and return".)

#ruby-on-rails #error #error-handling #ruby-on-rails-development #ruby