Ruby on rails - 嵌套表单，未保存的属性（使用回形针上传图像）

I have followed harlt's tutorial to start with ruby. Now I want to add pictures to my microposts. When I use the simple form just to upload a picture it works. When I want to upload a picture in the form of my micropost, image is created but all attributes are empty.I have followed harlt's tutorial to start with