Trying to save some others going through this pain. I have a parent and child associations both in the same form.
In parent i added `accepts_nested_attributes_for :child` and thought its going to take care of everything which is wrong. This helps in `create` and `update` but not in `delete`. To delete the child association you need to mention allow_destroy: true
accepts_nested_attributes_for :child, allow_destroy: true