Question

I used this code in my “users” views and had no trouble: <% if current_user.admin? %>. But using it in a set of views associated with a different controller throws up the “No method Error.”

Background: the app allows admins to create scavenger hunts. Admins should be able to delete hunts. I thought I knew how to configure everything, but apparently, I’m missing something. Here’s my code:

controller.rb

class HuntsController < ApplicationController

  def index
     @title = "All Hunts"
     @hunts = Hunt.order("name ASC") 
  end

  def show
    @hunt = Hunt.find(params[:id])
    @title = @hunt.name    
  end

  def new
    @hunt = Hunt.new
    @title = "New Hunt"  
  end

  def create
    @hunt = Hunt.new(params[:hunt])
    if @hunt.save
      flash[:success] = "Hunt created!"
      redirect_to hunts
    else
      @title = "New Hunt"
      render 'new'     
    end
  end

  def edit
    @hunt = Hunt.find(params[:id])
    @title = "Edit hunt"
  end

  def delete
    Hunt.find(params[:id]).destroy
    flash[:success] = "Hunt destroyed."
    redirect_to index  
  end

end

Views/Index.html.erb

    <h1>All Hunts</h1>

    <ul>
      <% @hunts.each do |hunt| %>
         <%= render hunt  %>
      <% end %>
    </ul>

    <%= link_to( "Create New Hunt", '/hunts/new') %> 

Views/_hunt.html.erb

<li>
  <%= link_to hunt.name, hunt %>
  <% if current_user.admin? %>
   <%= link_to "delete", hunt, :method => :delete, :confirm => "You sure?",
                                :title => "Delete #{hunt.name}" %>
  <% end %>
</li>

Error Message when trying to head to /hunts:

NoMethodError in Hunts#index
Showing ...../app/views/hunts/_hunt.html.erb where line #3 raised:
undefined method `admin?' for nil:NilClass

Answer 1

current_user is nil, and thus does not know how to respond to admin?. Either ensure that current_user is always a user instance, or check that it’s not nil.

In Ruby 2.3+, one can use the “safe navigation” operator (&.):

if current_user&.admin?

In Ruby 2.2 and earlier, instead use boolean short-circuiting:

if current_user && current_user.admin?

Note that ActiveSupport has try, but that has different behavior which will potentially hide bugs. For similar behavior, use try! instead.

Getting “undefined method _____ for nil:NilClass” is a very common occurrence in Ruby, so get used to it happening often :).