How do I use instance variables, defined in the controller, in the view with ActiveAdmin?

Question

I have this:

ActiveAdmin.register User do
  controller do
    def show
      @user = User.find(params[:id])
      show! 
    end
  end

  show do
    attributes_table do
      row "User" do
        link_to @user.display_name, user_path(@user.slug) 
      end
    end
  end
end

But when I load the page, I get an error saying:

undefined method `display_name' for nil:NilClass

which means that @user is nil. I am positive that @user is set appropriately (meaning the finder is getting appropriate data that exists in the db). I'm thinking it has something to with how ActiveAdmin works that I'm unfamiliar with. Any thoughts?

Also, I know I could do show do |user|, but there are more complicated things I am using this for and need access to the user object in the controller.

Answer 1

Just in case someone else stumbles upon this:

controller.instance_variable_get(:@user)

should work as well.

Answer 2

There is controller in active admin, despite this you can not pass instance variable to arbre part. But you can use params hash for this:

ActiveAdmin.register User do
  controller do
    def show
      params[:user] = User.find(params[:id])
      show! 
    end
  end

  show do
    attributes_table do
      row "User" do
        link_to params[:user].display_name, user_path(params[:user].slug) 
      end
    end
  end
end

P.S.: If you don't want to change params, then all instance variables are stored in @arbre_context.assigns. You may also do like:

link_to @arbre_context.assigns[:user].display_name, user_path(@arbre_context.assigns[:user].slug)