Why does it feel like im going about this the wrong way?

searchtree

def index
    if request.format == 'json'
      if params[:product_type_id].present?
        @search_trees = ProductType.find(params[:product_type_id]).search_trees
      else
        @search_trees = SearchTree.botttom_nodes
      end
    else
      @search_trees = SearchTree.roots
    end

    authorize! :read, @search_trees
    respond_with @search_trees do |format|
      format.json{ render :json => @search_trees.map{|s| {:search_tree => {:name => s.short_label, :id => s.id}}}.to_json}
    end
  end