动态添加基本嵌套字段，而不在rails 4中使用“link_to_function”

For a month I have been struggling to get the hang of nested forms. It has been difficult because the examples are very complicated and include code that is now deprecated. I have it all worked out except adding the fields dynamically. I am hoping to see the minimum code necessary for the most basic application which I have built here - a parent called 'parent' with one nested child association called 'child'. For a month I have been struggling to get the h