Rails 'nil'不是activemodel兼容的对象。它必须实现:to_partial_path。ajax

I am following section 4 (Server Side Concerns) to set up ajax on a page. I've copied the tutorial text completely (replacing the model names with my own) and it creates and saves my "Participants" record, but does not automatically refresh the ajax partial. I am following section 4 (Server Side Concerns)