title: Rails / ActiveAdmin - how to pass custom data from controller into content
body: <p>I have a custom page that is going to pull some data and format it to so it can be displayed in a table. This is a very simplified version:</p>
  
  <pre><code>ActiveAdmin.register_page "My Custom Page" do
    controller do
      @data = [
        { name: "foo"},
        { name: "bar"}
      ]
    end
  
    content do
      panel "My Panel" do
        table_for @data do
          column("Name") { |row| row[:name] }
        end
      end
    end
  end
  </code></pre>
  
  <p>When I run that, I get an error <code>undefined method '[]' for nil:NilClass
  </code> because the variable <code>row</code> getting passed into the block is nil. How do I properly pass the <code>@data</code> object to the view?</p>