新手问题 <%=image_tag 升级到 rails 5.2.1 后报错，原来 5.1.2 没有问题。求解决
CarrierWave with Rails 5.2 ActiveStorage may have some issues. You could try to change your classic image_tag.
Assuming you're using something like this :
%= image_tag(@user.image) %>
Change it to something like this, using .url
<%= image_tag(@user.image.url) %>
https://stackoverflow.com/questions/50307547/carrierwave-for-image-upload-with-ruby-on-rails