在form_for块中传递特定控制器和操作的选项哈希时未找到控制器操作

I'm trying to create a form in rails 4 using form_for based on an object representing a training course. Before loading the page, the app checks whether the current user has already signed up for the course. If not, then the submit button on the form creates a new 'signup' marking the course id and the user id in the signups table. This works correctly.I'm trying to create a form in rails 4 using fo