Rails: Too Few Arguments

You forgot to write responds_to block:

def update
  @holder = Holder.find(params[:id])
  if @holder.update_attributes(params[:holder])
    respond_to do |format|
      format.html { redirect_to holders_path } #, flash[:success] = "holder updated")
      format.js
    end
  else
    render 'edit'
  end
end

But I am suspicious about your index.html.erb, I don’t think that will really work the way you think.